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IN DENTAL ESTHETICS CLINICAL AND LABORATORY PROCEDURES

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PRECISION IN DENTAL ESTHETICS 'fhi.. hook j, dedirall'd to 111� ..plt·ndid daugl11er. Sarah." ho ha., tnadl' 111� lifl' nH·aniugful. and to 111� part'llh.

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CLINICAL AND LABORATORY PROCEDURES

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DOMENICO MASSIRONI, MD, DMD

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Private Practice, Milan, Italy 'Thi .. hook j, d(·dirml'd to all 111� dt·are,l. wond('rful frit·rHI ..-111� part'lth. inrluding my fath('r. Sih io. ''Ito left 11, all too ,ooiL uncl111� n1olitt·r. Ho ..alha. "ho j., happy for nw wda�. and 111� cltildren. Chri ..tian nnd Cahrit·li·. '' ho hring j o� to 111� lifl'. To thi, li.t I arid m� hr1hrr. Bol,eno. and 111� �Iarina. who are nnill'd

Gillsl•ppe

Jloltii'O

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id1

lh

\,� llu· I-896. 8.

oral camera and operating microscope for the detection

17. Sheets CG, Paquette IM. Hatate K. The clinical micro·

precision dentistry. Compend Conlin Educ Dent 1999;

scope in an esthetic restorative practice. J Esthet Restor

9· Michaelides PL. USe of the operating microscope in dentistry. I calif Dent Assoc 1996;24:45-50.

25. Sheets CG, Paquette IM. Practical applications of the

for teaching histology. I Dent Educ 1984;48:566-567.

clinical microscope in a restorative dental practice. Com·

20. Khayat BG. The use or magnification in endodontic therapy. The operating microscope. Pract Periodontics Aesthet Dent 1998;10:137-144·

In: Hardin I (ed). Clark's Clinical Dentistry, vol 4- St Louis: Mosby, 1998:1-14.

ment or Strabismus, ed 3 · St Louis: Mosby, 1985. 27. Zoz Nl, Kuznetsov luA. Some health aspects of vision during work with microscopes (in Russian]. Gig Tr Prof

22. Arens DE. Introduction to magniication in endodontics.

Zabol 1972;16:5-9. 28. Richards W. Instrument myopia-Microscopy. Am I

Esthet Restor Dent 2003;15:426-439.

23. Sempira HN, Hatwell GR. Frequency or second mesio· buccal canals in maxillary molars as determined by use of an operating microscope: A clinical study.

Burian MM, von Noorden GC. Burian-von Noorden's Binocular Vision and Ocular Motility: Theory and anage­

21. Carr GB. Magnification and illumination in endodontics.

1

pend Contin Educ Dent 2000;21:1084-1090. 26.

I

Endod

2000;26:673674·

Optom Physiol Opt 1976;53:658663. 29. Friedman MI. Landesman HM. Microscope-assisted pre­ cision (MAP) dentistry. A challenge for new knowledge. I (ali[ Dent Assoc 1998;26:90-905.

24. Pecora G, Andreana S. Use of dental operating micro· scopes in endodontic surgery. Oral Surg Oral ed Oral Pathol 1993;75:751-759.

667671.

Friedman M, ora AF, Schmidt R. Microscope-assisted

20:723-7)6.

19. Powell GL, Stevens W. The use of conference microscopes

Dent 2001;1):187-200. 18. Winter RR, Cornell OF, Vingoren Gl, Patrick RB. Use of magnification in dental technology. I Esthet Restor Dent 2003;15:409-415;discussion 416.

2

3

CHAPTER 2 Magnification Systems Used in Dentistry

R E F E R E N CES

10. Erten H, Uctasli MB, Akarslan U, Uzun 0, Baspinar E. The assessment of unaided visual examination, intra·

1. Weathers A K . Access to success: Taking a closer look a t magnification. Dent Today 2005;24:to6, 108-111. 2. van As G. Magnification and the alternatives for micro· dentistry. Compend Contm Educ Dent 2001;22:10o8tOt2, 1014-1016. ). Garcia A. Dental magniication: A clear view of the pres· ent and a close-up view of the future. Compend Cantin Educ Dent 205;26:459-463. 4· Caplan SA. agniication in dentistry. I Esthet Dent

1990;2:17-21. 5 · Shanelec DA. Optical principles of loupes. I Calif Dent Assoc 1992;20:25-32. 6. Millar Bl. Focus on loupes. Br Dent I 1998;185:504-508. 7. Zaugg B. Stassinakis A. Holl P. lnnuence or magnifica­

or occlusal caries lesions. Oper Dent 2005;30:t9cr194· 11. Behle C. Photography and the operating microscope in dentistry. I (ali[ Dent Assoc 2001;29:765-771. 12. Tibbetts LS, Shanelec DA. An overview of periodontal microsurgery. Curr Opin Periodontal 1994:187-193. 13. Shanelec OA, Tibbetts LS. A perspective on the future of periodontal microsurgery. Periodontal 2000 1996;11: 58-64. 14. Cortellini P. Tonetti MS. Microsurgical approach to peri· odontal regeneration. Initial evaluation in a case report. 1 Periodontal 2001;4:559-569.

15. Tibbetts LS, Shanelec DA. Periodontal microsurgery. Dent Clin North Am 1998;42:339-359.

tion tools on the recognition of simulated preparation

16. Whitehead SA. Wilson NH. Restorative decision-making

and filling errors (in German� Schweiz Monatsschr

behavior with magnification. Quintessence tnt 1992;23:

Zahnmed 2004; 114:89>-896. 8.

oral camera and operating microscope for the detection

17. Sheets CG, Paquette IM. Hatate K. The clinical micro·

precision dentistry. Compend Conlin Educ Dent 1999;

scope in an esthetic restorative practice. J Esthet Restor

9· Michaelides PL. USe of the operating microscope in dentistry. I calif Dent Assoc 1996;24:45-50.

25. Sheets CG, Paquette IM. Practical applications of the

for teaching histology. I Dent Educ 1984;48:566-567.

clinical microscope in a restorative dental practice. Com·

20. Khayat BG. The use or magnification in endodontic therapy. The operating microscope. Pract Periodontics Aesthet Dent 1998;10:137-144·

In: Hardin I (ed). Clark's Clinical Dentistry, vol 4- St Louis: Mosby, 1998:1-14.

ment or Strabismus, ed 3 · St Louis: Mosby, 1985. 27. Zoz Nl, Kuznetsov luA. Some health aspects of vision during work with microscopes (in Russian]. Gig Tr Prof

22. Arens DE. Introduction to magniication in endodontics.

Zabol 1972;16:5-9. 28. Richards W. Instrument myopia-Microscopy. Am I

Esthet Restor Dent 2003;15:426-439.

23. Sempira HN, Hatwell GR. Frequency or second mesio· buccal canals in maxillary molars as determined by use of an operating microscope: A clinical study.

Burian MM, von Noorden GC. Burian-von Noorden's Binocular Vision and Ocular Motility: Theory and anage­

21. Carr GB. Magnification and illumination in endodontics.

1

pend Contin Educ Dent 2000;21:1084-1090. 26.

I

Endod

2000;26:673674·

Optom Physiol Opt 1976;53:658663. 29. Friedman MI. Landesman HM. Microscope-assisted pre­ cision (MAP) dentistry. A challenge for new knowledge. I (ali[ Dent Assoc 1998;26:90-905.

24. Pecora G, Andreana S. Use of dental operating micro· scopes in endodontic surgery. Oral Surg Oral ed Oral Pathol 1993;75:751-759.

667671.

Friedman M, ora AF, Schmidt R. Microscope-assisted

20:723-7)6.

19. Powell GL, Stevens W. The use of conference microscopes

Dent 2001;1):187-200. 18. Winter RR, Cornell OF, Vingoren Gl, Patrick RB. Use of magnification in dental technology. I Esthet Restor Dent 2003;15:409-415;discussion 416.

2

3

C H A P T E R

3

T O O T H P RE PARAT I O N C O M P L E TE C R O W N S

F OR

A X I A L . ANATO M I C L I M ITS Prosthetic restoration involves a number of proce­

4

O C C L U S A L .

A N D

G I N G I V A L

L I M I T S

Devitalization of the tooth for this purpose is con­ sidered overtreatment. 1

With respect to the occlusal limit, proper reduc·

dures designed to integrate the restoration in the

tion of the occlusal or palatal surface of the tooth

patient's mouth in keeping with functional, esthetic,

should not exceed limits of minimum tooth structure

and anatomic concerns. Tooth preparation is an es­

or adversely affect the masticatory function. This

sential pat of this process. The success of this pro­

limit depends on the relation of the pulp chamber to

cedure requires optimal use of various materials for

the occlusal surface during reduction, and it some­

impressions, restoration, and adhesion, exploiting

times conflicts with the goal of achieving ideal thick­

certain properties and minimizing others. Preparation

ness for a ceramic or metal-ceramic prosthesis. One

requires controlled reduction of tooth form and vol­

of the most common errors committed during tooth

ume (Figs 3-1 to 3-3). Too much or too little thick­

preparation is insufficient reduction of the occlusal

ness or depth can initiate a series of imprecisions

surface of prepared teeth (molars and premolars).

and errors that jeopardize the success of the

particularly in the middle third of canines and in the

restoration. The clinician must be reasonably dex­

palatal area of incisors.

terous and, above all, have a clear vision of how to

In a study of 25 canines prepared for restoration,

proceed with the tooth reduction while keeping in

Zanetti et al' found the reduction too shallow in

mind the three fundamental anatomic limits: axial,

Bs% of the cases, excessive in 15% of the cases,

occlusal, and gingivaL

and of average correct depth in only 10% of the

The term axial limit refers to the consideration of

cases. For 25% of the cases, the reduction did not

pulpal vitality. It is now widely accepted that reduc­

even reach a depth of o.s mm, a serious error for

ing a tooth for prosthetic purposes is compatible

the longevity of the definitive restoration. To avoid

with the integrity and health of the dental pulp.

th i s problem when preparing the palatal area of

Fig 3-1 S i l i cone index positioned over a model of a maxillary central incisor. The longitudinally sectioned silicone index clearly illustrates the necessary reduction for a ceramic or ceramometal restoration. Use of a silicone index allows the clinician to define the proportions and dimensions of the prosthetic tooth before beginning reduction to ensure the proper integration of the restoration.

Figs 3-2 and 3-3 Examples of preparations with controlled reduction. The clinician can measure reduction with the diameter size of the b u rs to preserve the overall shape of the prepared tooth and provide the necessary space for the restorative materiaL

_

Ftg 3-4 When the shape of the reduction tool impedes accurate measurement of the amount of tissue removed. a clinician may prepare the tooth one half at a lime. as recommended by Mclean.3 Figs 3-5 and 3-6 Tooth extracted with periodontal tissue and sectioned using a microtome. The periodontal tissue. with its delicate structure. must always be treated carefully during preparation and the positioning of the finish line.

S

C H A P T E R

3

T O O T H P RE PARAT I O N C O M P L E TE C R O W N S

F OR

A X I A L . ANATO M I C L I M ITS Prosthetic restoration involves a number of proce­

4

O C C L U S A L .

A N D

G I N G I V A L

L I M I T S

Devitalization of the tooth for this purpose is con­ sidered overtreatment. 1

With respect to the occlusal limit, proper reduc·

dures designed to integrate the restoration in the

tion of the occlusal or palatal surface of the tooth

patient's mouth in keeping with functional, esthetic,

should not exceed limits of minimum tooth structure

and anatomic concerns. Tooth preparation is an es­

or adversely affect the masticatory function. This

sential pat of this process. The success of this pro­

limit depends on the relation of the pulp chamber to

cedure requires optimal use of various materials for

the occlusal surface during reduction, and it some­

impressions, restoration, and adhesion, exploiting

times conflicts with the goal of achieving ideal thick­

certain properties and minimizing others. Preparation

ness for a ceramic or metal-ceramic prosthesis. One

requires controlled reduction of tooth form and vol­

of the most common errors committed during tooth

ume (Figs 3-1 to 3-3). Too much or too little thick­

preparation is insufficient reduction of the occlusal

ness or depth can initiate a series of imprecisions

surface of prepared teeth (molars and premolars).

and errors that jeopardize the success of the

particularly in the middle third of canines and in the

restoration. The clinician must be reasonably dex­

palatal area of incisors.

terous and, above all, have a clear vision of how to

In a study of 25 canines prepared for restoration,

proceed with the tooth reduction while keeping in

Zanetti et al' found the reduction too shallow in

mind the three fundamental anatomic limits: axial,

Bs% of the cases, excessive in 15% of the cases,

occlusal, and gingivaL

and of average correct depth in only 10% of the

The term axial limit refers to the consideration of

cases. For 25% of the cases, the reduction did not

pulpal vitality. It is now widely accepted that reduc­

even reach a depth of o.s mm, a serious error for

ing a tooth for prosthetic purposes is compatible

the longevity of the definitive restoration. To avoid

with the integrity and health of the dental pulp.

th i s problem when preparing the palatal area of

Fig 3-1 S i l i cone index positioned over a model of a maxillary central incisor. The longitudinally sectioned silicone index clearly illustrates the necessary reduction for a ceramic or ceramometal restoration. Use of a silicone index allows the clinician to define the proportions and dimensions of the prosthetic tooth before beginning reduction to ensure the proper integration of the restoration.

Figs 3-2 and 3-3 Examples of preparations with controlled reduction. The clinician can measure reduction with the diameter size of the b u rs to preserve the overall shape of the prepared tooth and provide the necessary space for the restorative materiaL

_

Ftg 3-4 When the shape of the reduction tool impedes accurate measurement of the amount of tissue removed. a clinician may prepare the tooth one half at a lime. as recommended by Mclean.3 Figs 3-5 and 3-6 Tooth extracted with periodontal tissue and sectioned using a microtome. The periodontal tissue. with its delicate structure. must always be treated carefully during preparation and the positioning of the finish line.

S

CHAPTER 3 Tooth Preparation for Complete Crowns

. incisors and canines, the clinician should reduce one

axial surfaces. In 1955. )orgensen6 recommended a

half of a tooth at a time. Using this technique, de·

value of 2 to 5 degrees, which was supported by

scribed by Mclean,3 a football contour point is used

retention tests measuring tensile strength and con­

to reduce one half of the tooth (Fig 3-4). By follow·

firmed in 1994 by Wilson and Chan7 (Fig 3-7). These

ing this procedure, the clinician can make an imme­

recommended values for the TOC appear to be ideal

diate evaluation of the amount of dental structure

values for maximum retention, though they are rarely

removed, even when using convex points, which do

achieved in clinical practice. Indeed, the average

not permit measurement of the amount and depth

TOC angle ranges from 12 to 27 degrees, with no ap·

of reduction.

parent correlation to the level of experience of the

The gingiva/ limit is defined by an area known as

clinicians sampled.s-1 1

the biologic width, a concept that is universally rec­

These studies underscore the influence of several

ognized but remains dificult to quantify numerical·

factors on the TOC angle, including the type of tooth

ly.4·S According to Gargiulo et al,4 the biologic width

(anterior or posterior), the arch in which it is located

varies from tooth to tooth, but the authors report

(maxilla or mandible), and the tooth surface being

the following average values: o.69 mm for the gin·

prepared. The authors noted the following factors:

FIG 3-7

TH E TOC ANGLE

FIG 3-8

RAN G ES

FROM

gival sulcus, 0.97 mm for the epithelial attachment, and 1.07 mm for the connective tissue attachment, for a total biologic width of 2.04 mm (0.97 mm

+

1.07 mm). For prosthetic purposes, the biologic width

•

•

or by the prosthetic margin after cementation. If the

Mandibular teeth had a greater TOC angle than Posterior teeth had a greater TOC angle than an· terior teeth (Fig 3·8)

•

upon during the initial positioning of the finish line biologic width is not preserved, the tissues react with

0 22 DEGREES

maxillay teeth

represents the minimum distance from the finish line to the bone crest, and it must never be intruded

1 0 T

Buccolingual surfaces had a greater TOC angle than mesiodistal surfaces

•

Monocular vision yielded a greater TOC than binocular vision

chronic gingival inflammation and bone recession. Therefore the clinician must stay within these limits to

In defense of the TOC values obtained by clini­

maintain healthy and stable gingival tissue (Figs 3·5

cians, some studies have offered a modified per·

and 3·6).

spective.9·"·'3 Oodge et al'4 tested the resistance of cemented crowns in teeth 10 mm in diameter and

SCIENTIFIC PRINCIPLES

3 - 5 mm in height with three diferent TOC angles. The 22-degree angle proved inadequate in resisting

The clinical approach to tooth preparation for com·

lateral forces, while no significant difference was

plete crowns must take into consideration certain

noted between the IO· and 16-degree angles. The

scientific principles to ensure the biomechanical and

authors concluded that 16 degrees was ideal, since

esthetic success of the restoration. One preparation

to-degree angles are not easily achieved in clinical

requisite that has attracted clinical interest is the

practice. In 1997, Shillingburg et ai'S recommended

total occlusal convergence (TOQ, which is defined

that the TOC angle should be confined to a range of

as the angle of convergence b etween two opposing

10 to 2 2 degrees (Figs 3·9 and 3·1o).

FIG 3-9

.

FIG 3-10

Fig J-7 TOC of a prepared maxillary central incisor. The TOC. calculated by measuring the angle between the mesial and distal surfaces. is about 8 degrees. This value is lower than optimal. according to several researchers 1·7

Fig3-8 TOC of a prepared posterior tooth. Posterior teeth have a greater TOC than do anterior teeth. and the angle formed by the buccal and palatal walls is larger than that between the mesial and distal walls. F1gs 3-g and 3·10 Examples of prepared teeth with optimal TOC angles \between 1 0 and 2 2 degrees) for prosthetic purposes.

11

CHAPTER 3 Tooth Preparation for Complete Crowns

. incisors and canines, the clinician should reduce one

axial surfaces. In 1955. )orgensen6 recommended a

half of a tooth at a time. Using this technique, de·

value of 2 to 5 degrees, which was supported by

scribed by Mclean,3 a football contour point is used

retention tests measuring tensile strength and con­

to reduce one half of the tooth (Fig 3-4). By follow·

firmed in 1994 by Wilson and Chan7 (Fig 3-7). These

ing this procedure, the clinician can make an imme­

recommended values for the TOC appear to be ideal

diate evaluation of the amount of dental structure

values for maximum retention, though they are rarely

removed, even when using convex points, which do

achieved in clinical practice. Indeed, the average

not permit measurement of the amount and depth

TOC angle ranges from 12 to 27 degrees, with no ap·

of reduction.

parent correlation to the level of experience of the

The gingiva/ limit is defined by an area known as

clinicians sampled.s-1 1

the biologic width, a concept that is universally rec­

These studies underscore the influence of several

ognized but remains dificult to quantify numerical·

factors on the TOC angle, including the type of tooth

ly.4·S According to Gargiulo et al,4 the biologic width

(anterior or posterior), the arch in which it is located

varies from tooth to tooth, but the authors report

(maxilla or mandible), and the tooth surface being

the following average values: o.69 mm for the gin·

prepared. The authors noted the following factors:

FIG 3-7

TH E TOC ANGLE

FIG 3-8

RAN G ES

FROM

gival sulcus, 0.97 mm for the epithelial attachment, and 1.07 mm for the connective tissue attachment, for a total biologic width of 2.04 mm (0.97 mm

+

1.07 mm). For prosthetic purposes, the biologic width

•

•

or by the prosthetic margin after cementation. If the

Mandibular teeth had a greater TOC angle than Posterior teeth had a greater TOC angle than an· terior teeth (Fig 3·8)

•

upon during the initial positioning of the finish line biologic width is not preserved, the tissues react with

0 22 DEGREES

maxillay teeth

represents the minimum distance from the finish line to the bone crest, and it must never be intruded

1 0 T

Buccolingual surfaces had a greater TOC angle than mesiodistal surfaces

•

Monocular vision yielded a greater TOC than binocular vision

chronic gingival inflammation and bone recession. Therefore the clinician must stay within these limits to

In defense of the TOC values obtained by clini­

maintain healthy and stable gingival tissue (Figs 3·5

cians, some studies have offered a modified per·

and 3·6).

spective.9·"·'3 Oodge et al'4 tested the resistance of cemented crowns in teeth 10 mm in diameter and

SCIENTIFIC PRINCIPLES

3 - 5 mm in height with three diferent TOC angles. The 22-degree angle proved inadequate in resisting

The clinical approach to tooth preparation for com·

lateral forces, while no significant difference was

plete crowns must take into consideration certain

noted between the IO· and 16-degree angles. The

scientific principles to ensure the biomechanical and

authors concluded that 16 degrees was ideal, since

esthetic success of the restoration. One preparation

to-degree angles are not easily achieved in clinical

requisite that has attracted clinical interest is the

practice. In 1997, Shillingburg et ai'S recommended

total occlusal convergence (TOQ, which is defined

that the TOC angle should be confined to a range of

as the angle of convergence b etween two opposing

10 to 2 2 degrees (Figs 3·9 and 3·1o).

FIG 3-9

.

FIG 3-10

Fig J-7 TOC of a prepared maxillary central incisor. The TOC. calculated by measuring the angle between the mesial and distal surfaces. is about 8 degrees. This value is lower than optimal. according to several researchers 1·7

Fig3-8 TOC of a prepared posterior tooth. Posterior teeth have a greater TOC than do anterior teeth. and the angle formed by the buccal and palatal walls is larger than that between the mesial and distal walls. F1gs 3-g and 3·10 Examples of prepared teeth with optimal TOC angles \between 1 0 and 2 2 degrees) for prosthetic purposes.

11

CHAPTER 3 Tooth Preparation for Complete Crowns

�

Another study'6 showed that the most important

is the use of boxes, grooves, or pin holes. 21 These

factor in the stability of the prosthetic restoration is

secondary retentions must be constructed with

its resistance to lateral forces, rather than its inser­

regard to the dislocating forces, which differ accord­

tion axis or TOC angle. The clinician must seek to

ing to restoration type. For single crowns, the dislo­

create convergence angles that are reproducible with

cating forces are primarily buccolingual and the

restorative materials and yet will ensure the lateral

boxes and grooves must be placed on the proximal,

stability of the prosthetic restoration. The authors

mesial, and distal surfaces. For fixed patial den­

believe that an angle measuring between 10 and 20

tures, the forces are primarily mesiodistal and the

degrees will provide such stability. A TOC angle over

retentive elements should be placed on the buccal

the limit leads to certain dislocation of the restora­

and lingual surfaces" (Figs 3-11 and 3-12).

tion,'7 but it is impossible to set a maximum limit

In a literature review, Goodacre et ai'J list sever­

since other variables, such as the height of the pre­

al preparation guidelines to ensure the mechanical,

pared tooth, are involved in determining the stability.

biologic, and esthetic success of a restoration.

Another point of clinical interest with regard to

Among the principles listed are those regarding the

retention is the minimum occlusogingival height of

preparation of the tooth in its entirety, including the

the prepared tooth in relation to the angle of con­

TOC, the occlusogingival and incisogingival dimen­

vergence. In an analysis of the stability of incisors

sions, the relationship between the occlusogingival

and premolars with occlusogingival heights of 1, 2,

dimension and the buccolingual dimension, and the

3, and 5 mm and a minimal TOC angle of 6 degrees,

circumferential morphology. Other principles concern

Maxwell et al'8 concluded that the height must be at

aspects of the inish line (le, its position, form, and

least 3 mm. Another study'9 introduced the concept

depth in relation to the various restorative materi­

of a critical TOC value over which a crown cannot

als), the depth of axial and occlusaVincisal reduc­

maintain adequate stability. The study indicated

tion, the form of the linear angle, and the surface of

that, theoretically, stability criteria are met when a

the prepared tooth.

molar 10 mm in diameter and 3 mm in occlusogin­

I

I

- ·

FIG 3-11

G R O O V E S M U ST B E P R E P A R E D TO O P P O S E T H E D I S P LA C E M E N T F O R C E S

Their conclusions can be summarized as follows:

gival height has a TOC of 17-4 degrees or less. Woolsey and Matich20 conirmed these data, con­

•

cluding that a height of 3 mm is suficient if associ­ ated with an angle of 10 degrees but insuficient

degrees. •

Recommended minimum heights are 4 mm for

with an angle of 20 degrees, which is common in

prepared molars and 3 mm for other prepared

molars. For molars, the ideal occlusocervical height

teeth. If the values are lower, axial grooves and

is 4 mm.

boxes can be added to the proximal surface for

When working with convergence angles of 10 to

single crowns or to the buccolingual areas for

20 degrees, the clinician should prepare incisors and premolars with a minimum occlusogingival height of

fixed partial dentures. •

3 mm and molars with a minimum height of 4 mm. When the clinician is faced with a clinical case in

8

The TOC angle should be between 10 and 20

The occlusogingivaVbuccolingual dimension ratio

FIG 3-12

should be equal to or greater than 0.4 mm. •

Facioproximal and linguoproximal line angles

which more stability is needed in teeth that do not

should be preserved whenever possible. Exces-

have the minimum dimensions, a viable alternative

sive rounding is to be avoided.

.

Figs 3-11 and 3-12 Retention grooves can be prepared on the mesial or distal walls for a single crown or on the buccal or palatal surfaces for a fixed partial denture. The grooves should create resistance against the dislocating forces. which have different vectors for a single crown (buccolingual) or a fixed partial denture (mesiodistal).

I

CHAPTER 3 Tooth Preparation for Complete Crowns

�

Another study'6 showed that the most important

is the use of boxes, grooves, or pin holes. 21 These

factor in the stability of the prosthetic restoration is

secondary retentions must be constructed with

its resistance to lateral forces, rather than its inser­

regard to the dislocating forces, which differ accord­

tion axis or TOC angle. The clinician must seek to

ing to restoration type. For single crowns, the dislo­

create convergence angles that are reproducible with

cating forces are primarily buccolingual and the

restorative materials and yet will ensure the lateral

boxes and grooves must be placed on the proximal,

stability of the prosthetic restoration. The authors

mesial, and distal surfaces. For fixed patial den­

believe that an angle measuring between 10 and 20

tures, the forces are primarily mesiodistal and the

degrees will provide such stability. A TOC angle over

retentive elements should be placed on the buccal

the limit leads to certain dislocation of the restora­

and lingual surfaces" (Figs 3-11 and 3-12).

tion,'7 but it is impossible to set a maximum limit

In a literature review, Goodacre et ai'J list sever­

since other variables, such as the height of the pre­

al preparation guidelines to ensure the mechanical,

pared tooth, are involved in determining the stability.

biologic, and esthetic success of a restoration.

Another point of clinical interest with regard to

Among the principles listed are those regarding the

retention is the minimum occlusogingival height of

preparation of the tooth in its entirety, including the

the prepared tooth in relation to the angle of con­

TOC, the occlusogingival and incisogingival dimen­

vergence. In an analysis of the stability of incisors

sions, the relationship between the occlusogingival

and premolars with occlusogingival heights of 1, 2,

dimension and the buccolingual dimension, and the

3, and 5 mm and a minimal TOC angle of 6 degrees,

circumferential morphology. Other principles concern

Maxwell et al'8 concluded that the height must be at

aspects of the inish line (le, its position, form, and

least 3 mm. Another study'9 introduced the concept

depth in relation to the various restorative materi­

of a critical TOC value over which a crown cannot

als), the depth of axial and occlusaVincisal reduc­

maintain adequate stability. The study indicated

tion, the form of the linear angle, and the surface of

that, theoretically, stability criteria are met when a

the prepared tooth.

molar 10 mm in diameter and 3 mm in occlusogin­

I

I

- ·

FIG 3-11

G R O O V E S M U ST B E P R E P A R E D TO O P P O S E T H E D I S P LA C E M E N T F O R C E S

Their conclusions can be summarized as follows:

gival height has a TOC of 17-4 degrees or less. Woolsey and Matich20 conirmed these data, con­

•

cluding that a height of 3 mm is suficient if associ­ ated with an angle of 10 degrees but insuficient

degrees. •

Recommended minimum heights are 4 mm for

with an angle of 20 degrees, which is common in

prepared molars and 3 mm for other prepared

molars. For molars, the ideal occlusocervical height

teeth. If the values are lower, axial grooves and

is 4 mm.

boxes can be added to the proximal surface for

When working with convergence angles of 10 to

single crowns or to the buccolingual areas for

20 degrees, the clinician should prepare incisors and premolars with a minimum occlusogingival height of

fixed partial dentures. •

3 mm and molars with a minimum height of 4 mm. When the clinician is faced with a clinical case in

8

The TOC angle should be between 10 and 20

The occlusogingivaVbuccolingual dimension ratio

FIG 3-12

should be equal to or greater than 0.4 mm. •

Facioproximal and linguoproximal line angles

which more stability is needed in teeth that do not

should be preserved whenever possible. Exces-

have the minimum dimensions, a viable alternative

sive rounding is to be avoided.

.

Figs 3-11 and 3-12 Retention grooves can be prepared on the mesial or distal walls for a single crown or on the buccal or palatal surfaces for a fixed partial denture. The grooves should create resistance against the dislocating forces. which have different vectors for a single crown (buccolingual) or a fixed partial denture (mesiodistal).

I

CHAPTER 3 Tooth Preparation for Complete Crowns

11

Conclusions regarding the finish line can be sum-

Bur design

marized as follows: Handpieces'S are classified according to the maxi­ •

•

•

The choice of finish line depends on the type of

mum diameter of the bur, for example, a cone­

restoration, the esthetic demands, the ease of

shaped bur is classified by the maximum diameter

execution, and the clinician's experience.

rather than by the diameter of the point, which is

Esthetics and the condition of the prepared teeth

considerably narrower. The handpiece is completed

determine the position of the finish line. The

by a shank made of tempered stainless steel, which

supragingival position is most recommended.

is corrosion-resistant and, above all, flex-resistant

Line angles should be rounded and well pol·

even at high speeds.

ished.

FIG 3-13

There are two categories of burs. The first essen­

determined by the head shape (eg, cylindrical, con­

adaptation with the various types of finish lines

ical, inverted cone) and the geometric blade design'S

because results of comparative studies are biased

(eg, surgical osteotrites used in implant surgery).

by the varied abilities and skills of dental techni­

Tungsten carbide burs are made of a sintered mate­

cians who make the prostheses.

Fig 3-14 Coarse-grit bur at rest.

of tungsten carbide. The design of these burs is

dificult to scientifically correlate better marginal

FIG 3-15

Fig 3-13 Fine-gril (30-�ml and coarse-grit (1 80-�ml burs. When not in motion the fine-grit bur appears to have a larger diameter.

tially performs a boring action and is usually made The most important aspect, however, is that it is

FIG 3-14

F1g 3-15 Coarse-grit bur in motion. demonstrating a diameter equal to the fine-g rit bur.

rial of 90% tungsten carbide and 10% cobalt, which acts as a binder, and they have a characteristic hard­

0

11

cone}, but the abrasion layer is determined by the

risk of breakage and maintain the integrity of the

ROTATING I N STRUMENTS

ness value of 1,6oo (compare with the hardness value of 400 for stainless steel). The tungsten carbide bur

random distribution of diamond grains on the bur.

high-speed air turbine. The clinician must maintain

Before the practical aspects of tooth preparation can

is attached by means of hydrostatic pressure, heat

The diamond grains, selected by size, are bonded to

congruity between the shape and total diameter of

be addressed, the required instruments should be

(hot isostatic pressure [HIPD. and welding to the

the bur head of the instrument through an electro­

the bur, depending on the grit of the abrasion layer

described to clariy their selection and proper use.

neck of the instrument, which in turn is connected

lytic bath, whereby two thirds of each grain be­

(coarse, medium, or fine). For example, a bur with a

Tooth preparation using rotating instruments must be

to the stainless steel shank. The blade design of the

come embedded in the nickel bonding compound.

coarse grit should have a diameter that is smaller

carried out following a systematic process through­

bur may be helicoidal, transversal, straight, or cross

Diamonds are used for abrasion because they have

than that of a bur with a finer grit and yet still pre­

out treatment. Every clinician must be completely

cutting, with cutting and finishing options that vary

a hardness superior to that of the surfaces to be

serve optimal rigidity. To avoid excessive weakening

familiar with these instruments, which are used pri­

according to the clinical or laboratory application

abraded.

of the shank, coarse grits are most efective for burs

marily for abrasion.

(eg, finishing of the tooth preparation, crown sepa­

The eficacy and quality of an abrasion bur are

of reduced diameter, such as 0.14 mm, whereas

There is considerable debate as to the proper

ration, cavity preparation, fabrication of resin crowns

determined by the type of abrasion material, the

extra-coarse grits are more efective for burs of 0.1B

shape, diameter, and blade design or grit of the bur.

or removable partial dentures, casting, waxing, fin­

coaxiality and concentric rotation, the shape and

mm diameter or larger. Burs with coarse- and extra­

For example, one study24 incorrectly recommends

ishing, and polishing).

diameter of the bur. and the grit of the abrasion

coarse grit will appear smaller than a bur with the

the use of sharp, medium-grit diamonds of small

The second type of bur works with the abrasion

layer. The coaxiality, or symmetry, of the bur controls

same diameter but finer grit. Only during rotation is

diameter, claiming that this will ensure maximum

of a diamond layer. Diamond burs also have a vari­

vibration accompanied by percussive efects and the

it possible to see that the diameters are identical

conservation of dental tissue and pulp.

ety of head shapes (eg, conical, cylindrical, inverted .

bur's degree of precision. It also helps reduce the

(Figs 3-13 to 3-15).

..

91

CHAPTER 3 Tooth Preparation for Complete Crowns

11

Conclusions regarding the finish line can be sum-

Bur design

marized as follows: Handpieces'S are classified according to the maxi­ •

•

•

The choice of finish line depends on the type of

mum diameter of the bur, for example, a cone­

restoration, the esthetic demands, the ease of

shaped bur is classified by the maximum diameter

execution, and the clinician's experience.

rather than by the diameter of the point, which is

Esthetics and the condition of the prepared teeth

considerably narrower. The handpiece is completed

determine the position of the finish line. The

by a shank made of tempered stainless steel, which

supragingival position is most recommended.

is corrosion-resistant and, above all, flex-resistant

Line angles should be rounded and well pol·

even at high speeds.

ished.

FIG 3-13

There are two categories of burs. The first essen­

determined by the head shape (eg, cylindrical, con­

adaptation with the various types of finish lines

ical, inverted cone) and the geometric blade design'S

because results of comparative studies are biased

(eg, surgical osteotrites used in implant surgery).

by the varied abilities and skills of dental techni­

Tungsten carbide burs are made of a sintered mate­

cians who make the prostheses.

Fig 3-14 Coarse-grit bur at rest.

of tungsten carbide. The design of these burs is

dificult to scientifically correlate better marginal

FIG 3-15

Fig 3-13 Fine-gril (30-�ml and coarse-grit (1 80-�ml burs. When not in motion the fine-grit bur appears to have a larger diameter.

tially performs a boring action and is usually made The most important aspect, however, is that it is

FIG 3-14

F1g 3-15 Coarse-grit bur in motion. demonstrating a diameter equal to the fine-g rit bur.

rial of 90% tungsten carbide and 10% cobalt, which acts as a binder, and they have a characteristic hard­

0

11

cone}, but the abrasion layer is determined by the

risk of breakage and maintain the integrity of the

ROTATING I N STRUMENTS

ness value of 1,6oo (compare with the hardness value of 400 for stainless steel). The tungsten carbide bur

random distribution of diamond grains on the bur.

high-speed air turbine. The clinician must maintain

Before the practical aspects of tooth preparation can

is attached by means of hydrostatic pressure, heat

The diamond grains, selected by size, are bonded to

congruity between the shape and total diameter of

be addressed, the required instruments should be

(hot isostatic pressure [HIPD. and welding to the

the bur head of the instrument through an electro­

the bur, depending on the grit of the abrasion layer

described to clariy their selection and proper use.

neck of the instrument, which in turn is connected

lytic bath, whereby two thirds of each grain be­

(coarse, medium, or fine). For example, a bur with a

Tooth preparation using rotating instruments must be

to the stainless steel shank. The blade design of the

come embedded in the nickel bonding compound.

coarse grit should have a diameter that is smaller

carried out following a systematic process through­

bur may be helicoidal, transversal, straight, or cross

Diamonds are used for abrasion because they have

than that of a bur with a finer grit and yet still pre­

out treatment. Every clinician must be completely

cutting, with cutting and finishing options that vary

a hardness superior to that of the surfaces to be

serve optimal rigidity. To avoid excessive weakening

familiar with these instruments, which are used pri­

according to the clinical or laboratory application

abraded.

of the shank, coarse grits are most efective for burs

marily for abrasion.

(eg, finishing of the tooth preparation, crown sepa­

The eficacy and quality of an abrasion bur are

of reduced diameter, such as 0.14 mm, whereas

There is considerable debate as to the proper

ration, cavity preparation, fabrication of resin crowns

determined by the type of abrasion material, the

extra-coarse grits are more efective for burs of 0.1B

shape, diameter, and blade design or grit of the bur.

or removable partial dentures, casting, waxing, fin­

coaxiality and concentric rotation, the shape and

mm diameter or larger. Burs with coarse- and extra­

For example, one study24 incorrectly recommends

ishing, and polishing).

diameter of the bur. and the grit of the abrasion

coarse grit will appear smaller than a bur with the

the use of sharp, medium-grit diamonds of small

The second type of bur works with the abrasion

layer. The coaxiality, or symmetry, of the bur controls

same diameter but finer grit. Only during rotation is

diameter, claiming that this will ensure maximum

of a diamond layer. Diamond burs also have a vari­

vibration accompanied by percussive efects and the

it possible to see that the diameters are identical

conservation of dental tissue and pulp.

ety of head shapes (eg, conical, cylindrical, inverted .

bur's degree of precision. It also helps reduce the

(Figs 3-13 to 3-15).

..

91

TAB L E 3 - 1 Characteristics of diamond b u rs with various grit levels

CHAPTER 3

GRIT LEVEL

Tooth Preparation for Complete Crowns

FINE

COARSE

LOW

HIGH

HIGHER

LOW

WORKING JORCE

LOW

HIGHER

GENERATED•HEAi

LIMITED

LESS LIMITED

PRETIO. EFFECT

LOW

HIGHER

BETTER

POOR

WORKING TIME·

LONGER

SHORTER

BUR ENDURANCE •··.

HIGHER

LOWER

PARAMETER .

In the authors' opinion, the quality of lhe dia-

preparation. Table 3-1 shows that diamond burs wilh

mond burs is much more essential for selecting a

coarse grits have greater abrasion and cut more effi·

manufacturer than the range of bur shapes and

ciently, permitting the operator lo use a working

designs. A high-quality abrasion handpiece has a grit

force of aboul 100 g, 26- 27 while the working force

that is uniform in both size and shape. Allhough it

that can be used with fine-grit burs is about 30 g.

should have no bald spots, which would remove

Some authors28•29 have shown that when a clinician

material unevenly, the diamond layer should contain

reduces a tooth using a fine-gril diamond bur with

spaces that allow for the elimination of debris.

suficient water cooling,3° the increase in tooth tem­

Burs are available in a vast array of shapes and

perature is less than for burs with coarse and extra­

diameters, but tooth preparation for prostheses

coarse grits. Galindo and othersJ• analyzed the use

mostly requires large diameters that are easier for

of burs with coarse and extra-coarse grit (12S and

the operator to use, cause less lrauma to the pulp,

180 �m) and noted that the mean lemperature

and also function as measuring instruments. The shape and peripheral definition of the tooth preparation usually reflects the last application of

recorded during and after the cutting procedures was lower than baseline temperature. A comparative study32 showed that the tooth tem­

the bur on the tooth, during which the entire point

perature rises an average of o.8°C with fine-grit burs,

remains in contact with the tooth's longitudinal axis.

1.3°C with medium-grit burs, and t.S°C and 1.8°C with

Large-diameter burs are much easier to control than

coarse- and extra-coarse-grit burs, respectively. How­

smaller-diameter burs, and the correct preparation

ever, the trials in this study were carried out by

shape can be deined with fewer applications. In

making three successive cuts of o.8, o.s. and o.s mm

addition, the tooth temperature does not increase

toward the tooth's center. In clinical practice, the clin­

as much with large-diameter burs, thus protecting

ician works the bur around the circumference of the

the pulp. Large-diameter burs produce less heat

tooth to progressively abrade the surface and never

because they develop greater peripheral velocity

removes such thicknesses in one cut.

and therefore dissipate more heat. This rule is ex­ pressed through the following formula:

Vp (peripheral velocity) where K

�

�

diameter of the tool X no. of revolutions x T K

6o,ooo

All hough the conclusions of these in vitro exper­

�

ABRASION '"

,.. -

. �

J FINISHING .,

.'.ll

... p..

·�

.. iS reduced by SO%, 3S0fo, and 2S0/o for the three grades, respectively. A reduction in eficiency translates into a longer working time, an increased working force applied by

iments are valid, the authors of this text argue in

the operator, and a greater likelihood of clogging of

favor of the coarse- and extra-coarse-grit burs be­

the cutting edges of the diamonds. These factors

cause of the better cutting efficiency and debris

lead to an increase in temperature, which in turn

mond grains of 30 �m. are suitable only for inishing the tooth preparation and should be used with very little cutting force to keep the tooth temperature from rising too much and damaging the pulp.

H i g h-speed handp ieces Clinicians must use high-speed instruments, either

elimination, which leads consequently to substan­

detrimentally affects the pulp. For this reason, a clin­

tial decreases in the operating time and stress on

ician should reduce teeth using coarse- and extra­

high-speed air turbine handpieces or handpieces

the tooth. Although the greater eficiency of burs

coarse-grit burs, leaving the fine-grit burs exclusive­

with a torque multiplier. The high-speed air turbine

with coarse and extra-coarse grit is not widely rec­

ly for finishing the tooth preparation.

handpiece, invented in the 196os, remains the most

With a high peripheral velocity, which is directly

ognized,JJ Siegel and Von Fraunhofer34 have dis­

Because of their superior abrasion, coarse and

commonly used instrument for tooth preparation,

proportional to the diameter of the bur, not only can

cussed the importance of reduced operating times

extra-coarse burs produce a very irregular surface

especially in Mediterranean countries. However, this

heat dissipate more efficiently, but chips and shav­

and how efficiency decreases after the initial cut.

with a high degree of surface roughness (Fig 3-16),

instrument is being replaced by handpieces with

ings are eliminated more easily.

Their study comparing diamond burs with medium,

and they sufer more wear during use and must be

torque multipliers (Fig 3·17).

coarse, and extra-coarse grit making three succes­

replaced relatively often. Fine-particle burs, with dia-

The correct use of rotating instruments must also address grit selection and the techniques of tooth

.

sive cuts shows that the eficiency of the third cut .

93

TAB L E 3 - 1 Characteristics of diamond b u rs with various grit levels

CHAPTER 3

GRIT LEVEL

Tooth Preparation for Complete Crowns

FINE

COARSE

LOW

HIGH

HIGHER

LOW

WORKING JORCE

LOW

HIGHER

GENERATED•HEAi

LIMITED

LESS LIMITED

PRETIO. EFFECT

LOW

HIGHER

BETTER

POOR

WORKING TIME·

LONGER

SHORTER

BUR ENDURANCE •··.

HIGHER

LOWER

PARAMETER .

In the authors' opinion, the quality of lhe dia-

preparation. Table 3-1 shows that diamond burs wilh

mond burs is much more essential for selecting a

coarse grits have greater abrasion and cut more effi·

manufacturer than the range of bur shapes and

ciently, permitting the operator lo use a working

designs. A high-quality abrasion handpiece has a grit

force of aboul 100 g, 26- 27 while the working force

that is uniform in both size and shape. Allhough it

that can be used with fine-grit burs is about 30 g.

should have no bald spots, which would remove

Some authors28•29 have shown that when a clinician

material unevenly, the diamond layer should contain

reduces a tooth using a fine-gril diamond bur with

spaces that allow for the elimination of debris.

suficient water cooling,3° the increase in tooth tem­

Burs are available in a vast array of shapes and

perature is less than for burs with coarse and extra­

diameters, but tooth preparation for prostheses

coarse grits. Galindo and othersJ• analyzed the use

mostly requires large diameters that are easier for

of burs with coarse and extra-coarse grit (12S and

the operator to use, cause less lrauma to the pulp,

180 �m) and noted that the mean lemperature

and also function as measuring instruments. The shape and peripheral definition of the tooth preparation usually reflects the last application of

recorded during and after the cutting procedures was lower than baseline temperature. A comparative study32 showed that the tooth tem­

the bur on the tooth, during which the entire point

perature rises an average of o.8°C with fine-grit burs,

remains in contact with the tooth's longitudinal axis.

1.3°C with medium-grit burs, and t.S°C and 1.8°C with

Large-diameter burs are much easier to control than

coarse- and extra-coarse-grit burs, respectively. How­

smaller-diameter burs, and the correct preparation

ever, the trials in this study were carried out by

shape can be deined with fewer applications. In

making three successive cuts of o.8, o.s. and o.s mm

addition, the tooth temperature does not increase

toward the tooth's center. In clinical practice, the clin­

as much with large-diameter burs, thus protecting

ician works the bur around the circumference of the

the pulp. Large-diameter burs produce less heat

tooth to progressively abrade the surface and never

because they develop greater peripheral velocity

removes such thicknesses in one cut.

and therefore dissipate more heat. This rule is ex­ pressed through the following formula:

Vp (peripheral velocity) where K

�

�

diameter of the tool X no. of revolutions x T K

6o,ooo

All hough the conclusions of these in vitro exper­

�

ABRASION '"

,.. -

. �

J FINISHING .,

.'.ll

... p..

·�

.. iS reduced by SO%, 3S0fo, and 2S0/o for the three grades, respectively. A reduction in eficiency translates into a longer working time, an increased working force applied by

iments are valid, the authors of this text argue in

the operator, and a greater likelihood of clogging of

favor of the coarse- and extra-coarse-grit burs be­

the cutting edges of the diamonds. These factors

cause of the better cutting efficiency and debris

lead to an increase in temperature, which in turn

mond grains of 30 �m. are suitable only for inishing the tooth preparation and should be used with very little cutting force to keep the tooth temperature from rising too much and damaging the pulp.

H i g h-speed handp ieces Clinicians must use high-speed instruments, either

elimination, which leads consequently to substan­

detrimentally affects the pulp. For this reason, a clin­

tial decreases in the operating time and stress on

ician should reduce teeth using coarse- and extra­

high-speed air turbine handpieces or handpieces

the tooth. Although the greater eficiency of burs

coarse-grit burs, leaving the fine-grit burs exclusive­

with a torque multiplier. The high-speed air turbine

with coarse and extra-coarse grit is not widely rec­

ly for finishing the tooth preparation.

handpiece, invented in the 196os, remains the most

With a high peripheral velocity, which is directly

ognized,JJ Siegel and Von Fraunhofer34 have dis­

Because of their superior abrasion, coarse and

commonly used instrument for tooth preparation,

proportional to the diameter of the bur, not only can

cussed the importance of reduced operating times

extra-coarse burs produce a very irregular surface

especially in Mediterranean countries. However, this

heat dissipate more efficiently, but chips and shav­

and how efficiency decreases after the initial cut.

with a high degree of surface roughness (Fig 3-16),

instrument is being replaced by handpieces with

ings are eliminated more easily.

Their study comparing diamond burs with medium,

and they sufer more wear during use and must be

torque multipliers (Fig 3·17).

coarse, and extra-coarse grit making three succes­

replaced relatively often. Fine-particle burs, with dia-

The correct use of rotating instruments must also address grit selection and the techniques of tooth

.

sive cuts shows that the eficiency of the third cut .

93

CHAPTER 3 Tooth Preparation for Complete Crowns

.

The free-running speed of 30o,ooo to 40o,ooo

with a diameter of 0.10 mm and a cylindrical shape

rpm produced by the high-speed air turbine drops

(6879-314- 0IO [6 = grit, 879 = shape , 314

sharply as soon as the bur comes into contact with

grip, 010

the tooth. In contrast, the handpiece with torque

cone-shaped needle points with small diameters.

multiplier produces a free-running speed of 230,000

Needle point burs quickly lose diamond particles in

rpm, which can be maintained during abrasion and

the excessively fine tip, and their conical shape

adjusted to the lower speeds when necessary. The

often creates conical tooth preparations with little

technology of the torque multiplier permits the oper­

retention, a defect that is dificult to correct in sub­

ator to multiply the basic speed of 40,000 rpm by 4,

sequent stages.

=

=

friction

diameter], Komet) is preferable to the

s . or 5 - 7· increasing the speed to 16o,ooo, 2oo,ooo,

The simultaneous preparation of multiple teeth

and 230,000 rpm, respectively. Two settings for the

requires greater concentration of the clinician than

torque multiplier are used during tooth preparation.

the preparation of a single tooth. If the multiple

The maximum multiplication setting is used for the

restorations are to be connected, the prepared teeth

stages of separation and preliminary preparation,

must have the same insertion path to ensure prop­

while the lowest multiplication setting (4 multiplica·

er prosthetic fit. Even in the case of unconnected

tions) is used for finishing.

FIG J-17

FIG 3-16

Fig 3-16 Fine- 130 �ml and coarse-grit 1 1 80 �ml b u rs seen under a stereomicroscope at high magnification 1 2 5 X ) .

Fig 3-17 Handpiece with torque multiplier a n d three water-spray jets f o r cooling. T h i s handpiece h a s a multiplication factor o f five.

fixed restorations in which each tooth is restored independently, proper parallelism is critical for limit­

Choosing the right instrument for tooth preparation

ing the subsequent stress and possible distortion of the impression materials (see chapter 9 for more details about impressions). Therefore, when prepar­

For didactic purposes, tooth preparation can be divid­

ing multiple teeth, the clinician must prepare each

ed into three sequential stages: separation, prelimi­

tooth before moving on to the next stage. Separa­

nary preparation, and inishing. In each stage, dif­

tion, however, is performed only on the teeth adja­

ferent burs and instruments are used to optimize

cent to the preserved natural dentition.

results while minimizing operator stress and the

"

. at a rate of 44 m/minl 5 through three holes in the

appear on the bur where only the binding substance

upper part of the handpiece. The convergence of the

remains, the result would be pulpal damage. There

water on the working area reduces or eliminates the

is currently no standard method for evaluating the

possibility of damaging the tooth.

Prelim i nary preparation

Preliminary preparation is the most demanding stage

generated heatJ6 (Figs 3-20 and 3-21) . To optimize

degree of wear of a bur; manufacturers rely on the

Separation

because it establishes the conditions for the pros­

this stage, large-diameter burs (0.14, 0.16, and 0.18

sensitivity of the operator, an empirical criterion that

The critical separation stage requires great precision

thetic outcome. The objective is to reduce the tooth

mm) with the coarsest possible grit (180 �m) are

is not without error.

to avoid causing i rreversible damage to adjacent

in volume and shape and to correctly position the

used to achieve the maximum efect with the least

teeth and establishing inaccurate parallelism of the

gingival margins (Figs 3-18 and 3-19). This stage is

damage to the pulpal tissue (see Table 3-1).

prepared teeth. The use of a small-diameter cylin­

carried out using the torque multiplier at the mini­

Another i m portant factor i n minimizing trauma

visual checks with magnifying instruments in two

drical bur is preferred for the interproximal zone.

mum level of multiplication, and a working pressure

during a dental preparation involves the wear of the

ways. A static examination of wear is made by

Esthetic appearance is not crucial in this area, but

at a maximum of 100 g.

diamond abrasion layer, which is most significant

checking the visible ratio of diamonds to binding

with the coarsest grit. Wear manifests through the

substance. A dynamic examination involves observ­

The authors' method is to change the b u rs fre­ quently (every six to eight preparations) and make

the clinician must create sufficient space for the

During preliminay preparation of the dental tis­

preparation burs to place the buccopalatal grooves

sue, the clinician must cool the working area with a

loss of the diamond grains on the surface during

ing the bur in motion, to ensure that the diamond

(see Figs 4-82 and 4-83). A chamfer diamond bur

continuous jet of water. The water ideally is sprayed .

rotation (Fig 3-22). I f use continues after bald spots

grains produce the most uniform shape possible.

.

CHAPTER 3 Tooth Preparation for Complete Crowns

.

The free-running speed of 30o,ooo to 40o,ooo

with a diameter of 0.10 mm and a cylindrical shape

rpm produced by the high-speed air turbine drops

(6879-314- 0IO [6 = grit, 879 = shape , 314

sharply as soon as the bur comes into contact with

grip, 010

the tooth. In contrast, the handpiece with torque

cone-shaped needle points with small diameters.

multiplier produces a free-running speed of 230,000

Needle point burs quickly lose diamond particles in

rpm, which can be maintained during abrasion and

the excessively fine tip, and their conical shape

adjusted to the lower speeds when necessary. The

often creates conical tooth preparations with little

technology of the torque multiplier permits the oper­

retention, a defect that is dificult to correct in sub­

ator to multiply the basic speed of 40,000 rpm by 4,

sequent stages.

=

=

friction

diameter], Komet) is preferable to the

s . or 5 - 7· increasing the speed to 16o,ooo, 2oo,ooo,

The simultaneous preparation of multiple teeth

and 230,000 rpm, respectively. Two settings for the

requires greater concentration of the clinician than

torque multiplier are used during tooth preparation.

the preparation of a single tooth. If the multiple

The maximum multiplication setting is used for the

restorations are to be connected, the prepared teeth

stages of separation and preliminary preparation,

must have the same insertion path to ensure prop­

while the lowest multiplication setting (4 multiplica·

er prosthetic fit. Even in the case of unconnected

tions) is used for finishing.

FIG J-17

FIG 3-16

Fig 3-16 Fine- 130 �ml and coarse-grit 1 1 80 �ml b u rs seen under a stereomicroscope at high magnification 1 2 5 X ) .

Fig 3-17 Handpiece with torque multiplier a n d three water-spray jets f o r cooling. T h i s handpiece h a s a multiplication factor o f five.

fixed restorations in which each tooth is restored independently, proper parallelism is critical for limit­

Choosing the right instrument for tooth preparation

ing the subsequent stress and possible distortion of the impression materials (see chapter 9 for more details about impressions). Therefore, when prepar­

For didactic purposes, tooth preparation can be divid­

ing multiple teeth, the clinician must prepare each

ed into three sequential stages: separation, prelimi­

tooth before moving on to the next stage. Separa­

nary preparation, and inishing. In each stage, dif­

tion, however, is performed only on the teeth adja­

ferent burs and instruments are used to optimize

cent to the preserved natural dentition.

results while minimizing operator stress and the

"

. at a rate of 44 m/minl 5 through three holes in the

appear on the bur where only the binding substance

upper part of the handpiece. The convergence of the

remains, the result would be pulpal damage. There

water on the working area reduces or eliminates the

is currently no standard method for evaluating the

possibility of damaging the tooth.

Prelim i nary preparation

Preliminary preparation is the most demanding stage

generated heatJ6 (Figs 3-20 and 3-21) . To optimize

degree of wear of a bur; manufacturers rely on the

Separation

because it establishes the conditions for the pros­

this stage, large-diameter burs (0.14, 0.16, and 0.18

sensitivity of the operator, an empirical criterion that

The critical separation stage requires great precision

thetic outcome. The objective is to reduce the tooth

mm) with the coarsest possible grit (180 �m) are

is not without error.

to avoid causing i rreversible damage to adjacent

in volume and shape and to correctly position the

used to achieve the maximum efect with the least

teeth and establishing inaccurate parallelism of the

gingival margins (Figs 3-18 and 3-19). This stage is

damage to the pulpal tissue (see Table 3-1).

prepared teeth. The use of a small-diameter cylin­

carried out using the torque multiplier at the mini­

Another i m portant factor i n minimizing trauma

visual checks with magnifying instruments in two

drical bur is preferred for the interproximal zone.

mum level of multiplication, and a working pressure

during a dental preparation involves the wear of the

ways. A static examination of wear is made by

Esthetic appearance is not crucial in this area, but

at a maximum of 100 g.

diamond abrasion layer, which is most significant

checking the visible ratio of diamonds to binding

with the coarsest grit. Wear manifests through the

substance. A dynamic examination involves observ­

The authors' method is to change the b u rs fre­ quently (every six to eight preparations) and make

the clinician must create sufficient space for the

During preliminay preparation of the dental tis­

preparation burs to place the buccopalatal grooves

sue, the clinician must cool the working area with a

loss of the diamond grains on the surface during

ing the bur in motion, to ensure that the diamond

(see Figs 4-82 and 4-83). A chamfer diamond bur

continuous jet of water. The water ideally is sprayed .

rotation (Fig 3-22). I f use continues after bald spots

grains produce the most uniform shape possible.

.

CHAPTER 3 Tooth Preparation for Complete Crowns

. Fintshing

The last stage is finishing, which is usually performed

knows the anatomic and clinical aspects of the case and has a clear idea of the type of preparation

with a fine-grit bur, silicon carbide or Arkansas

required for the restoration. Once these objectives

stones, polishing rubbers, and manual cutting tools

have been established, the clinician can select a pre­

(ie. rounded chisel). When finishing with rotating

cise and effective procedure for a successful out·

instruments. the clinician should use the multiplier

come. There are several step-by-step approaches to

torque at the lowest multiplication level and a

tooth preparation that are designed to simpliy tooth

working force of 30 g. The aim is to make the sur­

reduction,

faces smoother and more uniform. Any attempt to

nique,J8 Mclean's reduction of half of the tooth at a

including Stei n's guide-groove tech­

modify the shape of the prepared tooth would gen­

time,J and Martignoni and Schonenberger's slant·

erate excessive heat and damage the pulp. The

cutting method.J9 Regardless of the technique, the

authors use a fine-grit bur (30 �m) to finish the axial

clinician must always keep anatomic references in

walls and the finish line (Fig 3-23). To make the fin­

mind and control the tooth reduction through an

ish line more regular. the authors use rounded chis­

awareness of the bur's diameter and the quantity of

els with suitable shapes and diameters (Fig 3-24).

dental matter being removed.

FIG 3-18

FIG 3-19

Knowing the amount of material to remove is possible by using a silicone index with a shore hard­

SYSTEMATIZED TOOTH PREPARATION

ness of 85 to 90 (Zetalabor, Zhermack).•0 A silicone index is made on a diagnostic cast or waxup pre­ pared in the laboratory. The clinician can use a sili­

Tooth preparation is a clinical operation t h a t c a n be

cone index that is properly cut longitudinally, hori­

carried out successfully.J7 provided the clinician

zontally, or serially (depending on the practical

�

FIG 3-20

FIG 3-21

FIG 3-22

Fig l-18 At high magnification. the rough surface of the tooth prepared with the 1 80-�m-grit bur is evident. ig 3-1 g Note the irregular profile resulting from the use of the 1 80-�m-grit bur. Figs 3-20 Bur in motion with jets of water aimed at the point . F1Q 3-21 8ur that does not provide adequate spray because of clogged or damaged water jets.

Fig 3;22 A worn bur (left) and a new one (right) of identical grit and shape. Coarse-grit burs are particularly subject to wear as d1amond gra1ns tome loose. Fig� 3-23 and 3-24 Prep ared tooth finished with a fine-grit bur and a manual chisel _ rehn1ng the preparat1on.

16

fDM1.

Oeppeler). the ideal instruments for

FIG 3-23

FIG 3-24

CHAPTER 3 Tooth Preparation for Complete Crowns

. Fintshing

The last stage is finishing, which is usually performed

knows the anatomic and clinical aspects of the case and has a clear idea of the type of preparation

with a fine-grit bur, silicon carbide or Arkansas

required for the restoration. Once these objectives

stones, polishing rubbers, and manual cutting tools

have been established, the clinician can select a pre­

(ie. rounded chisel). When finishing with rotating

cise and effective procedure for a successful out·

instruments. the clinician should use the multiplier

come. There are several step-by-step approaches to

torque at the lowest multiplication level and a

tooth preparation that are designed to simpliy tooth

working force of 30 g. The aim is to make the sur­

reduction,

faces smoother and more uniform. Any attempt to

nique,J8 Mclean's reduction of half of the tooth at a

including Stei n's guide-groove tech­

modify the shape of the prepared tooth would gen­

time,J and Martignoni and Schonenberger's slant·

erate excessive heat and damage the pulp. The

cutting method.J9 Regardless of the technique, the

authors use a fine-grit bur (30 �m) to finish the axial

clinician must always keep anatomic references in

walls and the finish line (Fig 3-23). To make the fin­

mind and control the tooth reduction through an

ish line more regular. the authors use rounded chis­

awareness of the bur's diameter and the quantity of

els with suitable shapes and diameters (Fig 3-24).

dental matter being removed.

FIG 3-18

FIG 3-19

Knowing the amount of material to remove is possible by using a silicone index with a shore hard­

SYSTEMATIZED TOOTH PREPARATION

ness of 85 to 90 (Zetalabor, Zhermack).•0 A silicone index is made on a diagnostic cast or waxup pre­ pared in the laboratory. The clinician can use a sili­

Tooth preparation is a clinical operation t h a t c a n be

cone index that is properly cut longitudinally, hori­

carried out successfully.J7 provided the clinician

zontally, or serially (depending on the practical

�

FIG 3-20

FIG 3-21

FIG 3-22

Fig l-18 At high magnification. the rough surface of the tooth prepared with the 1 80-�m-grit bur is evident. ig 3-1 g Note the irregular profile resulting from the use of the 1 80-�m-grit bur. Figs 3-20 Bur in motion with jets of water aimed at the point . F1Q 3-21 8ur that does not provide adequate spray because of clogged or damaged water jets.

Fig 3;22 A worn bur (left) and a new one (right) of identical grit and shape. Coarse-grit burs are particularly subject to wear as d1amond gra1ns tome loose. Fig� 3-23 and 3-24 Prep ared tooth finished with a fine-grit bur and a manual chisel _ rehn1ng the preparat1on.

16

fDM1.

Oeppeler). the ideal instruments for

FIG 3-23

FIG 3-24

CHAPTER 3 Tooth Preparation for Complete Crowns

4

needs of the operator), to evaluate the tooth prepa­

bur to access the entire occlusal surface, including

ration and determine what remains to be done (Figs

the lingual aspect. The object is to prepare the difi­

3-25 to 3-28).

cult lingual side with as much precision as the buc­

The initial stage of preparation consists of sepa­

cal side (Figs 3-33 to 3-36). The authors prefer con­

rating the preserved natural dentition from the teeth

ical burs to the barrel contour burs because they are

to be restored by using a thin cylindrical bur and a

more practical and versatile; the barrel contour bur

chamfer with a diameter of 0.10 (6879 - 314 - 010) (Fig

is often incongruent with the occlusal morphology of

3-29). Special care must be taken to protect the

the teeth. In the case of incisors and canines. the

interproximal area, preventing any lesions to the

palatal surface is prepared with a football contour

adjacent teeth or gingiva. The gingival reference

bur, using the Mclean techniquel to reduce half of

must never be lost; extending the preparation

the tooth at a time (Figs 3-37 and 3-38).

beyond the gingival margin not only damages the soft tissue, but also loses the positional reference.

two ridges and a groove are sufficient. Excessive sculpting of the occlusal surface could lead to a lack

each clinical stage before proceeding, since each

of correspondence during occlusion. with areas of

stage is preparatory for the next step. An incorrect or

the restoration presenting insufficient thickness.

incomplete procedure would require the operator to

Finally, the clinician may round the palatal and buc­

change burs several times to complete the next

cal surfaces for the insertion of the prosthesis, or,

stage, thus disrupting the clinician's concentration.

according to Kuwata's three-plane theory,•' to create

The finish line is repositioned only after the retraction cord (no. ooo or no. oo) has been placed.

face of the middle third of the tooth (Fig 3-30).

The anatomy of the gingiva and the technique of

According to Stein's technique,l8 other grooves

using retraction cords (see chapter 6) determines to

are made on the buccal and palatal surfaces (Fig 3-

what extent the restoration margin can be posi­

31) to the desired depth. If the preparation is being

tioned subgingivally. The thickness of the cord deter­

made with a so-degree shoulder bur or a chamfer

mines the amount of vertical retraction, and the pre­

bur, the depth is half the width of the instrument.

cision of the gingival retraction dictates the subgin­

After the first groove is made, the second is pre­

gival restoration margin. Once the impression has

pared by leaning on the first guide groove and

been made and the cord has been removed, the gin­

matching the inclination of the tooth. The reduction

giva should return to its normal level prior to the

of the tooth surface is then completed according to

insertion of the cord. Gingival retraction gives the clinician access to

procedure results in a uniform reduction of tooth

reposition the finish line to a subgingival level. For

volume and thickness (Fig 3-32).

about a decade, the authors have performed reposi­

The clinician reduces the occlusal surface of the

I

shape and thickness (Figs 3-39 to 3-41).

careful to avoid contact with the gingiva or the sur­

tooth with a large-diameter, short conical diamond

FIG 3-28

the requi red space for the restoration buildup in

operator places the groove with the bur slanted,

the limits set by the Stein grooves. The controlled

FIG 3-27

The clinician need not reproduce all the crests,

Another important element is the overall efficien­

buccal and palatal margins with a guide groove. The

FIG 3-26

grooves, and other features of the occlusal anatomy;

cy of the preparation. The operator should complete

After separation, the clinician must position the

FIG 3-25

tioning using sonic or ultrasonic oscillating instru­ ments. These nonrotating instruments do not dam- ..

Fig 3-25 Silicone index of a shore hardness of 85 (Zetalaborl made directly on the diagnostic waxup or cast. These functional guides can be sectioned to determine the volumes of the various longitudinal or horizontal planes.

Fig 3-26 1ndex has been sectioned horizontally with cuts at 2-mm intervals. leaving the peripheral portion intact. to help ualyze buccal reduc­ tion at the apical. middle. and coronal levels. Fig 3-27 Horizontal section of a silicone index. It is possible to make other index sections. for instance. by removing the buccal area entirely but leaving 1 to 2 mm of the incisal area on the buccal side. or by sectioning only the incisal portion. yielding an indirect view of available space.

Fig 3-28 Longitudinal section of a silicone index. Positioned at the midpoint of the tooth. the index provides exact values for the buccal. palatal. and incisal reduction.

"

CHAPTER 3 Tooth Preparation for Complete Crowns

4

needs of the operator), to evaluate the tooth prepa­

bur to access the entire occlusal surface, including

ration and determine what remains to be done (Figs

the lingual aspect. The object is to prepare the difi­

3-25 to 3-28).

cult lingual side with as much precision as the buc­

The initial stage of preparation consists of sepa­

cal side (Figs 3-33 to 3-36). The authors prefer con­

rating the preserved natural dentition from the teeth

ical burs to the barrel contour burs because they are

to be restored by using a thin cylindrical bur and a

more practical and versatile; the barrel contour bur

chamfer with a diameter of 0.10 (6879 - 314 - 010) (Fig

is often incongruent with the occlusal morphology of

3-29). Special care must be taken to protect the

the teeth. In the case of incisors and canines. the

interproximal area, preventing any lesions to the

palatal surface is prepared with a football contour

adjacent teeth or gingiva. The gingival reference

bur, using the Mclean techniquel to reduce half of

must never be lost; extending the preparation

the tooth at a time (Figs 3-37 and 3-38).

beyond the gingival margin not only damages the soft tissue, but also loses the positional reference.

two ridges and a groove are sufficient. Excessive sculpting of the occlusal surface could lead to a lack

each clinical stage before proceeding, since each

of correspondence during occlusion. with areas of

stage is preparatory for the next step. An incorrect or

the restoration presenting insufficient thickness.

incomplete procedure would require the operator to

Finally, the clinician may round the palatal and buc­

change burs several times to complete the next

cal surfaces for the insertion of the prosthesis, or,

stage, thus disrupting the clinician's concentration.

according to Kuwata's three-plane theory,•' to create

The finish line is repositioned only after the retraction cord (no. ooo or no. oo) has been placed.

face of the middle third of the tooth (Fig 3-30).

The anatomy of the gingiva and the technique of

According to Stein's technique,l8 other grooves

using retraction cords (see chapter 6) determines to

are made on the buccal and palatal surfaces (Fig 3-

what extent the restoration margin can be posi­

31) to the desired depth. If the preparation is being

tioned subgingivally. The thickness of the cord deter­

made with a so-degree shoulder bur or a chamfer

mines the amount of vertical retraction, and the pre­

bur, the depth is half the width of the instrument.

cision of the gingival retraction dictates the subgin­

After the first groove is made, the second is pre­

gival restoration margin. Once the impression has

pared by leaning on the first guide groove and

been made and the cord has been removed, the gin­

matching the inclination of the tooth. The reduction

giva should return to its normal level prior to the

of the tooth surface is then completed according to

insertion of the cord. Gingival retraction gives the clinician access to

procedure results in a uniform reduction of tooth

reposition the finish line to a subgingival level. For

volume and thickness (Fig 3-32).

about a decade, the authors have performed reposi­

The clinician reduces the occlusal surface of the

I

shape and thickness (Figs 3-39 to 3-41).

careful to avoid contact with the gingiva or the sur­

tooth with a large-diameter, short conical diamond

FIG 3-28

the requi red space for the restoration buildup in

operator places the groove with the bur slanted,

the limits set by the Stein grooves. The controlled

FIG 3-27

The clinician need not reproduce all the crests,

Another important element is the overall efficien­

buccal and palatal margins with a guide groove. The

FIG 3-26

grooves, and other features of the occlusal anatomy;

cy of the preparation. The operator should complete

After separation, the clinician must position the

FIG 3-25

tioning using sonic or ultrasonic oscillating instru­ ments. These nonrotating instruments do not dam- ..

Fig 3-25 Silicone index of a shore hardness of 85 (Zetalaborl made directly on the diagnostic waxup or cast. These functional guides can be sectioned to determine the volumes of the various longitudinal or horizontal planes.

Fig 3-26 1ndex has been sectioned horizontally with cuts at 2-mm intervals. leaving the peripheral portion intact. to help ualyze buccal reduc­ tion at the apical. middle. and coronal levels. Fig 3-27 Horizontal section of a silicone index. It is possible to make other index sections. for instance. by removing the buccal area entirely but leaving 1 to 2 mm of the incisal area on the buccal side. or by sectioning only the incisal portion. yielding an indirect view of available space.

Fig 3-28 Longitudinal section of a silicone index. Positioned at the midpoint of the tooth. the index provides exact values for the buccal. palatal. and incisal reduction.

"

CHAPTER 3 Tooth Preparation for Complete Crowns

Fig 3-31 Central buccal reduction grooves as recommended by Stein.31 Knowing the diameter and size of the bur. the amount of the initial reduction can be determined by making vertical notches in the tooth. start1ng from the gu1de groove made previOusly. Fig 3-32 Preparation proceeds to even out the rest of the palatal and buccal surfaces with the reduction grooves. always starting from the guide groove.

Fig 3-33 Reduction of the occlusal surface of the tooth. B y reducing the surface one half at a time. the clinician can visualize the extent of the reduction. Figs 3-34 and 3-35 Note how the occlusal reference points are maintained.

Fig 3-2g Separation of the tooth. Using metal matrices and wooden wedges as separators. care is taken not to impact the integrity of the neigh­ boring tooth. For this stage. the authors prefer to use a cylindrical bur with a small diameter 10.10 mm) rather than a needle-point bur. which wears down rapidly at the tip and can make the walls too conical. Fig 3-30 A g o-degree guide groove made while keeping the bur in an undercut direction. A chamfer. 50-degree. or round bur could also be used. The purpose of this step is to make a distinct line to mark the start of the preparation so that it is above the gingival margin and not touching the soft tissues. This is done on both the buccal and palatal surfaces. Normally the authors use a modified chamfer bur.

10

Fig 3-36 Barrel contour bur used for the o c clusal reduction. The authors prefer to use a short conical bur with a diameter of 2 . 5 mm.

Figs 3-37 and 3-38 Tooth preparation using football contour burs. The palatal surface of an anterior tooth is prepared with a coarse-grit bur fol­ lowed by a fine-grit bur. reducing one half of the tooth at a time.

101

CHAPTER 3 Tooth Preparation for Complete Crowns

Fig 3-31 Central buccal reduction grooves as recommended by Stein.31 Knowing the diameter and size of the bur. the amount of the initial reduction can be determined by making vertical notches in the tooth. start1ng from the gu1de groove made previOusly. Fig 3-32 Preparation proceeds to even out the rest of the palatal and buccal surfaces with the reduction grooves. always starting from the guide groove.

Fig 3-33 Reduction of the occlusal surface of the tooth. B y reducing the surface one half at a time. the clinician can visualize the extent of the reduction. Figs 3-34 and 3-35 Note how the occlusal reference points are maintained.

Fig 3-2g Separation of the tooth. Using metal matrices and wooden wedges as separators. care is taken not to impact the integrity of the neigh­ boring tooth. For this stage. the authors prefer to use a cylindrical bur with a small diameter 10.10 mm) rather than a needle-point bur. which wears down rapidly at the tip and can make the walls too conical. Fig 3-30 A g o-degree guide groove made while keeping the bur in an undercut direction. A chamfer. 50-degree. or round bur could also be used. The purpose of this step is to make a distinct line to mark the start of the preparation so that it is above the gingival margin and not touching the soft tissues. This is done on both the buccal and palatal surfaces. Normally the authors use a modified chamfer bur.

10

Fig 3-36 Barrel contour bur used for the o c clusal reduction. The authors prefer to use a short conical bur with a diameter of 2 . 5 mm.

Figs 3-37 and 3-38 Tooth preparation using football contour burs. The palatal surface of an anterior tooth is prepared with a coarse-grit bur fol­ lowed by a fine-grit bur. reducing one half of the tooth at a time.

101

CHAPTER 3 Principles of Preparation for Complete Crowns

�

age gingival tissue and are easier to control, result· ing in a more precise finish line (see chapter s).

preparation (ie, separation, preliminary preparation, and finishing) involves different priorities and foci.

The next stage is finishing, which is performed

A level of concentration (medium, medium-high, or

using fine-grit (Jo �m) diamond burs and roughing

high) can be assigned to each factor of tooth prepa­

stones of the same diameter. Roughing stones (sili­

ration based on the stage of preparation and the

con carbide and Arkansas). can be modified in shape

objectives (Fig 3-48). During the separation stage,

and size according to the operator's needs (Figs 3-42

concentration must be medium-high with respect to

to 3-44). Perfect shoulder polishing can be achieved

parallelism and medium for the tooth form and the

only through the use of manual chisels of appropri­

execution of the finish line. In the primary reduction

ate size and shape. Rounded chisels work via traction

stage, the level of concentration should be high for

in a clockwise and counterclockwise direction and are

parallelism and tooth form and medium-high for the

easy to use, permitting precise completion of the fin·

finish line. In the finishing stage, which is completed

ish line (Figs 3-45 and 3-46).

at low speed, maximum concentration is required for

SELECTIVE CO NCENTRATION

pleting the finish line. Parallelism is already estab­

FIG 3-39

FIG 3-40

FIG 3-41

FIG 3-42

FIG 3-43

FIG 3-4

FIG 3-45

FIG 3-46

polishing and finishing of the shoulder and for com­ lished at this point and requires little attention. In

T h e clinician must set t h e correct handpiece speed

this way, the necessary level of concentration can be

and choose burs with cutting or abrasion properties

focused on the principal objective of each stage,

to best address the specific task at hand and suc­

rather than concentrating equally on each factor, at

cessfully complete all stages of tooth preparation (Fig

all times. Selective attention helps the practitioner

3-47). These operating principles require the constant

avoid fatigue and lapses in concentration and con-

focused concentration of the clinician. Each stage of

tributes to the success of tooth preparation.

fig 3-3g Buccal and palatal surfaces are rounded holding the bur at a 45-degree angle to the tooth's longitudinal axis. figs 3-0 and 3-41 Preliminary preparation has provided adequate volume for the restorative materials. Note the presence of rough surfaces and sharp edges. from the occlusal mw. note the favorable spacing of the prepared tooth and the total visi­ bility of the shoulder mcumference. free of the shaded areas that i n dicate undercuts. fig 3-41 finishing stage of preparation carried out using fine-grit diamond burs or silicon carbide or corundum stones. figs 3-43 and3-44 A clin ician may customize the torm of Arkansas burs by direct abrasion on a stone of greater hardness. adapt­ _ to match Ing thm shape and me the spaces 1n the finiSh line obtained during preliminary preparation. figs 3;45 and 3-4i The last instrument needed for smoothing the surface is the rounded chisel. which can be used on every sur­ face 1n a clockwiSe and counterclockwise direction. Note the degree of smoothness on the finish tine obtained through the use of the rounded chiSel.

•

12 tl3

CHAPTER 3 Principles of Preparation for Complete Crowns

�

age gingival tissue and are easier to control, result· ing in a more precise finish line (see chapter s).

preparation (ie, separation, preliminary preparation, and finishing) involves different priorities and foci.

The next stage is finishing, which is performed

A level of concentration (medium, medium-high, or

using fine-grit (Jo �m) diamond burs and roughing

high) can be assigned to each factor of tooth prepa­

stones of the same diameter. Roughing stones (sili­

ration based on the stage of preparation and the

con carbide and Arkansas). can be modified in shape

objectives (Fig 3-48). During the separation stage,

and size according to the operator's needs (Figs 3-42

concentration must be medium-high with respect to

to 3-44). Perfect shoulder polishing can be achieved

parallelism and medium for the tooth form and the

only through the use of manual chisels of appropri­

execution of the finish line. In the primary reduction

ate size and shape. Rounded chisels work via traction

stage, the level of concentration should be high for

in a clockwise and counterclockwise direction and are

parallelism and tooth form and medium-high for the

easy to use, permitting precise completion of the fin·

finish line. In the finishing stage, which is completed

ish line (Figs 3-45 and 3-46).

at low speed, maximum concentration is required for

SELECTIVE CO NCENTRATION

pleting the finish line. Parallelism is already estab­

FIG 3-39

FIG 3-40

FIG 3-41

FIG 3-42

FIG 3-43

FIG 3-4

FIG 3-45

FIG 3-46

polishing and finishing of the shoulder and for com­ lished at this point and requires little attention. In

T h e clinician must set t h e correct handpiece speed

this way, the necessary level of concentration can be

and choose burs with cutting or abrasion properties

focused on the principal objective of each stage,

to best address the specific task at hand and suc­

rather than concentrating equally on each factor, at

cessfully complete all stages of tooth preparation (Fig

all times. Selective attention helps the practitioner

3-47). These operating principles require the constant

avoid fatigue and lapses in concentration and con-

focused concentration of the clinician. Each stage of

tributes to the success of tooth preparation.

fig 3-3g Buccal and palatal surfaces are rounded holding the bur at a 45-degree angle to the tooth's longitudinal axis. figs 3-0 and 3-41 Preliminary preparation has provided adequate volume for the restorative materials. Note the presence of rough surfaces and sharp edges. from the occlusal mw. note the favorable spacing of the prepared tooth and the total visi­ bility of the shoulder mcumference. free of the shaded areas that i n dicate undercuts. fig 3-41 finishing stage of preparation carried out using fine-grit diamond burs or silicon carbide or corundum stones. figs 3-43 and3-44 A clin ician may customize the torm of Arkansas burs by direct abrasion on a stone of greater hardness. adapt­ _ to match Ing thm shape and me the spaces 1n the finiSh line obtained during preliminary preparation. figs 3;45 and 3-4i The last instrument needed for smoothing the surface is the rounded chisel. which can be used on every sur­ face 1n a clockwiSe and counterclockwise direction. Note the degree of smoothness on the finish tine obtained through the use of the rounded chiSel.

•

12 tl3

CHAPTER l Tooth Preparation for Complete Crowns

� '

� t

w 1 ( : ..

Reduct1on

Separation Handptece spud

Level

Handp'ec' speed

l

Level Speed

Speed

$"

F1msh tme

Key

0100

=

=

Fmal flmshmg

Margm repos•t•on1ng

Level

Lew!

+

� NA

NA

0

NA

NA

000

Med1um concentrat•on

00 0I00 0 0

n

Fin i s h i g

0000

L

post lion

-+

$"

1

Form

w 1 ( : ..

=

Med1um-h1gh concentration

High concentration

pOSitiOn

00000

Ultrasonic tnstrument

Some

00000

tnstrument

Rounded ChiSel

NA

0000

Save e n e rgy u s i n g : Fig 3-47 Maxillary premolar and molar prepared for complete crowns. All stages of preparation are complete.

• • •

Clea r o bj ectives

Syst e m a t i c p roce d u re s

S e lective c o n c e n t ra t i o n

Fig 3-48 Diagram illustrating the selective concentration needed during the various stages o f preparation. The objective i s t o avoid fatigue b y focusing on the task at hand requiring the most attention. NA = not applicable.

14

105

CHAPTER l Tooth Preparation for Complete Crowns

� '

� t

w 1 ( : ..

Reduct1on

Separation Handptece spud

Level

Handp'ec' speed

l

Level Speed

Speed

$"

F1msh tme

Key

0100

=

=

Fmal flmshmg

Margm repos•t•on1ng

Level

Lew!

+

� NA

NA

0

NA

NA

000

Med1um concentrat•on

00 0I00 0 0

n

Fin i s h i g

0000

L

post lion

-+

$"

1

Form

w 1 ( : ..

=

Med1um-h1gh concentration

High concentration

pOSitiOn

00000

Ultrasonic tnstrument

Some

00000

tnstrument

Rounded ChiSel

NA

0000

Save e n e rgy u s i n g : Fig 3-47 Maxillary premolar and molar prepared for complete crowns. All stages of preparation are complete.

• • •

Clea r o bj ectives

Syst e m a t i c p roce d u re s

S e lective c o n c e n t ra t i o n

Fig 3-48 Diagram illustrating the selective concentration needed during the various stages o f preparation. The objective i s t o avoid fatigue b y focusing on the task at hand requiring the most attention. NA = not applicable.

14

105

CHAPTER 3 Tooth Preparation for Complete Crowns

REFERENCES

12. Lempoel Pi. Snoek PA. van1 Hof M. Lemmens Pl. The

2z. Wiskott HW, Nicholls 11. Belser UC. The efect of tooth

convergence angle of crown preparations with clinically

preparation height and diameter on the resistance of

satisactorv retention [in Dutch[. Ned Tijdschr Tand·

complete crowns to atigue loading. lnt J Prosthodont

diamond burs of diferent grit.

heelkd 1993;100:336-338.

1997;10:207-215.

80:12-19.

1. Kois JC. New paradigms for anterior tooth preparation. Rationale and technique. Oral Health 1998;88:19-30.

32.

Ottl P, Lauer HC. Temperature response in the pulpal chamber during ultrahigh-speed tooth preparation with

I Prosthet Dent 1998;

2. Zanetti AL, engar A. Novelli MD. Lagana DC. Thick·

13. Mou SH. Chai T, Wang )S. Shiau Y. Influence of difer­

23. Goodacre CJ. Campagni V, Aquilino SA. Tooth prepa·

ness of the remaining enamel after preparation of cin­

ent convergence angles and tooth preparation heights

rations for complete crowns: An art form based on sci­

ment of diferent grit on dental hard tissue [in Genman].

I Prosthet Dent

on the internal adaptation of Cerec crowns. J Prosthet

entiic principles. I Prosthet Dent 2001;85:363-376.

Dtsch Stomatal 1991;41:32>-322.

3· Mclean JW. The Science and M of Dental Ceramics.

14. Dodge W. Weed RM. Baez RJ. Buchanan RN. The efect

gulum rest seats on maxillay canines. 1998;8o:31-322.

Chicago: Quintessence. 1979.

of convergence angle on retention and resistance form.

4. Gargiulo AW. Wentz FM. Orban 81. Dimensions and rela· tion of the dentogingival junction in humans. J Peri­

mond burs: Heavy·handed or light-touch? I Prosthodont

cago: Quintessence. 1997.

1999:8:39·

ment of temperature change in the pulp chamber dur·

forces at high speed. J Prosthet Dent 2003;89:286-291.

ing cavity preparation. J Prosthet Dent 2004;91:436-440.

crowns to dynamic loading. lnt J Prosthodont 1996;9:

28. Carson J. Rider T, Nash D. A thermographic study of heat

37. Castellani D. La Preparazione dei pilastri per corone in

117-139 ·

ation of resistance form of dislodged crowns and retain­ ers. J Prosthet Dent 1998;80:405-409.

preparation height on the retention and resistance of gold castings. Gen Dent 1990;38:20>-202.

1993;2:61�6.

mented for dental students and general practitioners.

1

Am Dent

Assoc 1978:97:978980. 21.

1990:63:407-414.

change in the pulp chamber during complete crown preparation. I Prosthet Dent 1991;65:5Ht. 31. Galindo OF, Ercoli C. Funkenbusch PO, et al. Tooth

the resistance form of cast restorations.

pared for atiicial crowns. I Oral Rehabil 1978;5:371-375.

Acta Odontol Scand 1996:54:10-112.

Prosthodont

20. Woolsey GO. atich JA. The efect of axial grooves on

10. Ohm E, Silness J. The convergence angle in teeth pre­

U, Hansson . et al. xial wall

1

New guidelines for preparation taper.

Prosthet Dent

30. Laforgia PO, Milano V. Morea C, Desiate A. Temperature

19. Parker MH, Calverley MI. Gardner FM. Gunderson RB.

walls of full veneer crown preparations in a dental

29. Lauer HC, Kraft E. Rothlauf W. Zwingers l Efects of the

ultrahigh-speed tooth preparation. I

metal·ceramica. Bologna: Martina. 1994:207-2o8. 38. Stein RS, Kuwata M. A dentist and a dental technologist

Dent Res 1979;58:1681-1684.

temperature of cooling water during high-speed and

18. Maxwell AW, Blank LW, Pelleu GB Jr. Efect of crown

9· Noonan IE Jr. Goldfogel MH. Convergence of the axial

. Engstrom

distribution during ultra-speed cavity preparation. J

17. Trier AC. Parker MH. Cameron SM. Brousseau JS. Evalu·

criterion for the full veneer crown preparation in pre­

convergence of full veneer crown preparations. Docu­

25:544-548. 36. Ozturk B, Usumez A. Ozturk AN, Ozer . In vitro assess­

27. Elias K, Am is A. Setchell OJ. The magnitude of cutting

tion convergence and retention of extracoronal retain­

school environment. J Prosthet Dent 1991;66:70-708.

coolant Row rates and dental cutting. Oper Dent 2000:

between abutment taper and resistance of cemented

7- Wilson AH, Chan DC. The relationship between prepara­

clinical prosthodontics. I Prosthodont 1999;8:196-200.

diamond bur grit sizes. J Am Dent Assoc 200;131: 1706-1710.

16. Wiskott HW. Nicholls II, Belser UC. The relationship

convergence angle in cemented veneer crowns. Acta

8. Smith T. Garv 11. Conkin IE. Franks HL Efective taper

34· Siegel SC, Von Fraunhofer JA. Cutting eiciency of three

35· von Fraunhofer )A. Siegel SC. Feldman S. Handpiece

SE. Fundamentals of Fixed Prosthodontics, ed 3· Chi·

6. Jorgensen KD. The relationship between retention and

ers. I Prosthodont 1994;3:74-78.

I Prosthet Dent 2005;

26. Siegel SC, von Fraunhofer JA. Dental cutting with dia·

Omegan 1977;70:62�5.

Odontol Scand 1955;13:35-40.

25. Glossav of Prosthodontic Tenms. 94:192.

Quintessence lnt 1985;16:191-194.

5· Ingber JS, Rose LF, Coslet JG. The "biologic width"-A concept in periodontics and restorative dentistry. Alpha

Prlparationstechnik. Quintessenz 2001;52:873-883.

15. Shillingburg HT. Hobo S. Whitsett LD. Jacobi R, Brackett

odontal 1961;32:261-267.

11. Annerstedt

24. Kimmel K. Veahren und Probleme der oralmedizinischen

Dent 2002;87=24&-255·

33. )ung M, Pantke H . The efect of diamond grinding instru­

preparation: A study on the efect of diferent variables and a comparison between conventional and channeled

analyze current ceramo-metal procedures. Dent Clin North Am 1977; 21:729-749. 39- Martignoni M, Schonenberger J. Precision Fixed Pros­ thodontics: Clinical and Laboratorv Aspects. Chicago; Quintessence, 1989. 40. Magne P, Belser U. Bonded Porcelain Restorations in the Anterior Dentition: A Biomimetic Approach. Berlin: Quintessence, 2002:244-247· 41. Kuwata M. Color Atlas of Ceramo-Metal Technology. St Louis: lshiyaku EuroAmenca, 1986.

diamond burs. J Prosthodont 2004;13:3-16.

Proussaefs P, Campagni W, Bernal G, Goodacre C, Kim J. The efectiveness of auxiliay features on a tooth prepa­ ration with inadequate resistance form. 2004;91:3)-41.

1

Prosthet Dent

14 107

CHAPTER 3 Tooth Preparation for Complete Crowns

REFERENCES

12. Lempoel Pi. Snoek PA. van1 Hof M. Lemmens Pl. The

2z. Wiskott HW, Nicholls 11. Belser UC. The efect of tooth

convergence angle of crown preparations with clinically

preparation height and diameter on the resistance of

satisactorv retention [in Dutch[. Ned Tijdschr Tand·

complete crowns to atigue loading. lnt J Prosthodont

diamond burs of diferent grit.

heelkd 1993;100:336-338.

1997;10:207-215.

80:12-19.

1. Kois JC. New paradigms for anterior tooth preparation. Rationale and technique. Oral Health 1998;88:19-30.

32.

Ottl P, Lauer HC. Temperature response in the pulpal chamber during ultrahigh-speed tooth preparation with

I Prosthet Dent 1998;

2. Zanetti AL, engar A. Novelli MD. Lagana DC. Thick·

13. Mou SH. Chai T, Wang )S. Shiau Y. Influence of difer­

23. Goodacre CJ. Campagni V, Aquilino SA. Tooth prepa·

ness of the remaining enamel after preparation of cin­

ent convergence angles and tooth preparation heights

rations for complete crowns: An art form based on sci­

ment of diferent grit on dental hard tissue [in Genman].

I Prosthet Dent

on the internal adaptation of Cerec crowns. J Prosthet

entiic principles. I Prosthet Dent 2001;85:363-376.

Dtsch Stomatal 1991;41:32>-322.

3· Mclean JW. The Science and M of Dental Ceramics.

14. Dodge W. Weed RM. Baez RJ. Buchanan RN. The efect

gulum rest seats on maxillay canines. 1998;8o:31-322.

Chicago: Quintessence. 1979.

of convergence angle on retention and resistance form.

4. Gargiulo AW. Wentz FM. Orban 81. Dimensions and rela· tion of the dentogingival junction in humans. J Peri­

mond burs: Heavy·handed or light-touch? I Prosthodont

cago: Quintessence. 1997.

1999:8:39·

ment of temperature change in the pulp chamber dur·

forces at high speed. J Prosthet Dent 2003;89:286-291.

ing cavity preparation. J Prosthet Dent 2004;91:436-440.

crowns to dynamic loading. lnt J Prosthodont 1996;9:

28. Carson J. Rider T, Nash D. A thermographic study of heat

37. Castellani D. La Preparazione dei pilastri per corone in

117-139 ·

ation of resistance form of dislodged crowns and retain­ ers. J Prosthet Dent 1998;80:405-409.

preparation height on the retention and resistance of gold castings. Gen Dent 1990;38:20>-202.

1993;2:61�6.

mented for dental students and general practitioners.

1

Am Dent

Assoc 1978:97:978980. 21.

1990:63:407-414.

change in the pulp chamber during complete crown preparation. I Prosthet Dent 1991;65:5Ht. 31. Galindo OF, Ercoli C. Funkenbusch PO, et al. Tooth

the resistance form of cast restorations.

pared for atiicial crowns. I Oral Rehabil 1978;5:371-375.

Acta Odontol Scand 1996:54:10-112.

Prosthodont

20. Woolsey GO. atich JA. The efect of axial grooves on

10. Ohm E, Silness J. The convergence angle in teeth pre­

U, Hansson . et al. xial wall

1

New guidelines for preparation taper.

Prosthet Dent

30. Laforgia PO, Milano V. Morea C, Desiate A. Temperature

19. Parker MH, Calverley MI. Gardner FM. Gunderson RB.

walls of full veneer crown preparations in a dental

29. Lauer HC, Kraft E. Rothlauf W. Zwingers l Efects of the

ultrahigh-speed tooth preparation. I

metal·ceramica. Bologna: Martina. 1994:207-2o8. 38. Stein RS, Kuwata M. A dentist and a dental technologist

Dent Res 1979;58:1681-1684.

temperature of cooling water during high-speed and

18. Maxwell AW, Blank LW, Pelleu GB Jr. Efect of crown

9· Noonan IE Jr. Goldfogel MH. Convergence of the axial

. Engstrom

distribution during ultra-speed cavity preparation. J

17. Trier AC. Parker MH. Cameron SM. Brousseau JS. Evalu·

criterion for the full veneer crown preparation in pre­

convergence of full veneer crown preparations. Docu­

25:544-548. 36. Ozturk B, Usumez A. Ozturk AN, Ozer . In vitro assess­

27. Elias K, Am is A. Setchell OJ. The magnitude of cutting

tion convergence and retention of extracoronal retain­

school environment. J Prosthet Dent 1991;66:70-708.

coolant Row rates and dental cutting. Oper Dent 2000:

between abutment taper and resistance of cemented

7- Wilson AH, Chan DC. The relationship between prepara­

clinical prosthodontics. I Prosthodont 1999;8:196-200.

diamond bur grit sizes. J Am Dent Assoc 200;131: 1706-1710.

16. Wiskott HW. Nicholls II, Belser UC. The relationship

convergence angle in cemented veneer crowns. Acta

8. Smith T. Garv 11. Conkin IE. Franks HL Efective taper

34· Siegel SC, Von Fraunhofer JA. Cutting eiciency of three

35· von Fraunhofer )A. Siegel SC. Feldman S. Handpiece

SE. Fundamentals of Fixed Prosthodontics, ed 3· Chi·

6. Jorgensen KD. The relationship between retention and

ers. I Prosthodont 1994;3:74-78.

I Prosthet Dent 2005;

26. Siegel SC, von Fraunhofer JA. Dental cutting with dia·

Omegan 1977;70:62�5.

Odontol Scand 1955;13:35-40.

25. Glossav of Prosthodontic Tenms. 94:192.

Quintessence lnt 1985;16:191-194.

5· Ingber JS, Rose LF, Coslet JG. The "biologic width"-A concept in periodontics and restorative dentistry. Alpha

Prlparationstechnik. Quintessenz 2001;52:873-883.

15. Shillingburg HT. Hobo S. Whitsett LD. Jacobi R, Brackett

odontal 1961;32:261-267.

11. Annerstedt

24. Kimmel K. Veahren und Probleme der oralmedizinischen

Dent 2002;87=24&-255·

33. )ung M, Pantke H . The efect of diamond grinding instru­

preparation: A study on the efect of diferent variables and a comparison between conventional and channeled

analyze current ceramo-metal procedures. Dent Clin North Am 1977; 21:729-749. 39- Martignoni M, Schonenberger J. Precision Fixed Pros­ thodontics: Clinical and Laboratorv Aspects. Chicago; Quintessence, 1989. 40. Magne P, Belser U. Bonded Porcelain Restorations in the Anterior Dentition: A Biomimetic Approach. Berlin: Quintessence, 2002:244-247· 41. Kuwata M. Color Atlas of Ceramo-Metal Technology. St Louis: lshiyaku EuroAmenca, 1986.

diamond burs. J Prosthodont 2004;13:3-16.

Proussaefs P, Campagni W, Bernal G, Goodacre C, Kim J. The efectiveness of auxiliay features on a tooth prepa­ ration with inadequate resistance form. 2004;91:3)-41.

1

Prosthet Dent

14 107

C H A P T E R

4

F INISH L INE DESIGNS F OR C OM PLETE CROWN PRE PARATIONS

A

ccording to Castellani,' the finish line is

addition to the restorative materials, namely the

defined as the border between the intact por­

anatomy and tooth position; the number of teeth

tion of the tooth and the most apical point of

involved; the skill, precision. and experience of the

the preparation. The design of the finish line is critical

operator; and the practicality and convenience of the

in preparing complete crowns; it must be well defined.

design (Table 4-1). These criteria force the clinician to

regular, and, above all. well positioned. All of these

make diicult and complicated treatment choices that

properties are heavily inluenced by the accessibility,

are often case specific and require nonroutine and

or depth, of the inish line (igs 4-1 and 4-2).

unfamiliar procedures.l·•

TABLE 4-1 Comparison of restorative fi nish lines and their effects on restoration margin

Level of d i ficulty

Esthetics

Restoration margin

Marginal stress

Indications or contraindications

Feather edge

Easy

Poor

Metal collar

Very high

Indicated for fixed restorations with

Knife edge

Easy

Poor

Metal collar

Very high

intraoperative dental preparation

Type

There are numerous types of finish lines dis­ Aea inish lines

cussed in the literature, and their use in clinical prac­ tice depends on dental school curricula' and current

CHARACTERISTICS O F T H E

trends, as well as the kinds of materials used in the

VARIOUS F I N ISH L I N ES

advanced peri-odontal disease;

restoration. In practical terms. the key factors influ­ encing the design are the restorative material (eg,

The classification of finish lines involves an impor­

metal-ceramic, collarless metal-ceramic, all-ceramic).

tant distinction between area and linear finish lines

the type of connection, and the prosthetic treatment

(Figs 4-3 and 4-4). both of which have various con·

plan. It is now common for manufacturers to recom­

figurations. Area finish lines are either feather edged

mend a certai n type of finish line for materials with

or knife edged. Linear finish lines are either complex

speciic characteristics.

or simple and have either a shoulder or a chamfer.

The complexity of biomechanics requires advanced

An area finish line does not clearly delineate the

techniques, which also must be carefully considered

end of the prepared area from the intact portion of

when planning the restoration. The selection of a fin­

the tooth. These finish lines are oten erroneously

ish line. therefore, depends on several actors in

confused with nonpreparation of a tooth and are .

Rg 4-1 The finish line of the prep ara ti on must be regular. linear. and properly positioned. Preparations for both complete crowns or _inlays depend on the mobohty of the f1nish line. Rg 4-2 finish tine on a stone cast for a gold inlay restoration. This finish line. with an external bevel· a support plane · and an Internal bevel. guarantees the long-term success of the restoration.

Complex linear inish lines Beveled shoulder

Diicult

Poor

Metal collar

Very high

Indicated for multiple connected restorations

Beveled chamfer

Dificult

Poor

Metal collar

Vey high

Indicated for multiple connected restorations

Easy

Moderate

Metal collar

Moderate

Indicated for multiple connected restorations

Simple inish lines so-degree

Classic chamfer

Easy

Moderate

Metal collar

Minimal

Permits a good lit i n cases with buccolingual unevenness; m u ltiple

or micromargin

connected restorations Rounded shoulder

Difficult

Excellent

90-degee

May use all

Minimal

Dificult

Excellent

May use all

Moderate

Easy

Excellent

Optimal lit

Not to be used for multiple connected restorations

materials

shoulder

Not to be used for multiple connected restorations

materials

short chamfer

Modified chamfer

11

or micromargin

shoulder

Minimal

Permits a good fit in cases of

with all

buccolingual unevenness; multiple

materials

connected restorations

C H A P T E R

4

F INISH L INE DESIGNS F OR C OM PLETE CROWN PRE PARATIONS

A

ccording to Castellani,' the finish line is

addition to the restorative materials, namely the

defined as the border between the intact por­

anatomy and tooth position; the number of teeth

tion of the tooth and the most apical point of

involved; the skill, precision. and experience of the

the preparation. The design of the finish line is critical

operator; and the practicality and convenience of the

in preparing complete crowns; it must be well defined.

design (Table 4-1). These criteria force the clinician to

regular, and, above all. well positioned. All of these

make diicult and complicated treatment choices that

properties are heavily inluenced by the accessibility,

are often case specific and require nonroutine and

or depth, of the inish line (igs 4-1 and 4-2).

unfamiliar procedures.l·•

TABLE 4-1 Comparison of restorative fi nish lines and their effects on restoration margin

Level of d i ficulty

Esthetics

Restoration margin

Marginal stress

Indications or contraindications

Feather edge

Easy

Poor

Metal collar

Very high

Indicated for fixed restorations with

Knife edge

Easy

Poor

Metal collar

Very high

intraoperative dental preparation

Type

There are numerous types of finish lines dis­ Aea inish lines

cussed in the literature, and their use in clinical prac­ tice depends on dental school curricula' and current

CHARACTERISTICS O F T H E

trends, as well as the kinds of materials used in the

VARIOUS F I N ISH L I N ES

advanced peri-odontal disease;

restoration. In practical terms. the key factors influ­ encing the design are the restorative material (eg,

The classification of finish lines involves an impor­

metal-ceramic, collarless metal-ceramic, all-ceramic).

tant distinction between area and linear finish lines

the type of connection, and the prosthetic treatment

(Figs 4-3 and 4-4). both of which have various con·

plan. It is now common for manufacturers to recom­

figurations. Area finish lines are either feather edged

mend a certai n type of finish line for materials with

or knife edged. Linear finish lines are either complex

speciic characteristics.

or simple and have either a shoulder or a chamfer.

The complexity of biomechanics requires advanced

An area finish line does not clearly delineate the

techniques, which also must be carefully considered

end of the prepared area from the intact portion of

when planning the restoration. The selection of a fin­

the tooth. These finish lines are oten erroneously

ish line. therefore, depends on several actors in

confused with nonpreparation of a tooth and are .

Rg 4-1 The finish line of the prep ara ti on must be regular. linear. and properly positioned. Preparations for both complete crowns or _inlays depend on the mobohty of the f1nish line. Rg 4-2 finish tine on a stone cast for a gold inlay restoration. This finish line. with an external bevel· a support plane · and an Internal bevel. guarantees the long-term success of the restoration.

Complex linear inish lines Beveled shoulder

Diicult

Poor

Metal collar

Very high

Indicated for multiple connected restorations

Beveled chamfer

Dificult

Poor

Metal collar

Vey high

Indicated for multiple connected restorations

Easy

Moderate

Metal collar

Moderate

Indicated for multiple connected restorations

Simple inish lines so-degree

Classic chamfer

Easy

Moderate

Metal collar

Minimal

Permits a good lit i n cases with buccolingual unevenness; m u ltiple

or micromargin

connected restorations Rounded shoulder

Difficult

Excellent

90-degee

May use all

Minimal

Dificult

Excellent

May use all

Moderate

Easy

Excellent

Optimal lit

Not to be used for multiple connected restorations

materials

shoulder

Not to be used for multiple connected restorations

materials

short chamfer

Modified chamfer

11

or micromargin

shoulder

Minimal

Permits a good fit in cases of

with all

buccolingual unevenness; multiple

materials

connected restorations

CHAPtER 4 Fin1sh Line Designs for Complete Crown Preparations

A R E A A N D L I N E A R F I N ISH L I N ES

Figs 4-3 and 4-4 Two principal types of f1nish line, linear I Fig 4-1 and area I Fig 4-4). Tooth preparation with a linear finish line ends on a distinct line for its entire circumference. An area finish adapts the tooth preparation to the entire surface rather than to an exact li ne .

..commonly found under old fixed dental restorations.

subject to distortion and tension.s However, area in­

Although feather and knife edges are valid finish

ish lines are sometimes the best clinical solution dur­

lines that require the removal of dental tissue and

ing the surgical stage for cases of advanced peri­

the definition of form and volume, they are used

odontal disease that require a fixed dental prosthe­

less frequently in current clinical practice. It is the

sis.6 Area inish lines may also be useful for con­

authors' opinion, however, that a mediocre area fin ­

necting several restorative crowns together to stabi­

ish line is preferable to a mediocre linear inish line.

lize dental movement in the presence of signiicant­

With an area finish line (Fig 4-5), the marginal seal

ly reduced periodontal support.7 In �uch a situation,

will be more sure, whereas an inadequate linear fin­

it would be impossible to splint many crowns pre­

ish line inevitably produces a significant gap at the

pared, for example, with a shoulder design because

restoration margin (Fig 4-6).

of the lack of space between the tooth abutments

The main problem with area finish lines is that,

during the laboratory work and because of a prob­

given the preparation space and the thickness of re­

lem with the angles and planes. Although area finish

storative materials, they are suitable only for crowns

lines yield good marginal adaptation, the authors

with metal collars. furthermore, the thickness of the

prefer, even in such a case, to perform seconday

restorations at the margin does not meet minimum

welds once the margins are closed individually on

recommended values for laboratory procedures,

chamfer, modified chamfer, or other linear finish lines

which may result in a margin that is weak and thus

110

(Figs 4-7 and 4-8).8.9

Fig 4-5 1ncorrect area finish line. The obvious convexity of this preparation in profile creates an undercut. which presents a drawback for both adaptation and insertion of the prosthesis.

.

Fig4-6 Evident gap from the matching of an inadequate linear finish line to an ill-fitting metal margin. The same error for an area fin­ ish line is more acceptable because the seal covers an entire area of the surface instead of just a line. Figs 4-7 and 4-8 Clinical case of a patient with advanced periodontal disease and considerable buccal flaring of the teeth. The teeth were realigned through orthodontic and periodontal treatment and required a fixed prosthesis. The treatment aimed to cause u lit­ tle damage to the pulp as possible. Ceramic crowns were made individually and united using secondary welds i n three sections equipped with interlock devices. The area for the secondary weld was prepared by the dental technician along with the waxing of the framework and ceramic coating of the connections. The welding was completed only after the ceramic was applied.

1t1

CHAPtER 4 Fin1sh Line Designs for Complete Crown Preparations

A R E A A N D L I N E A R F I N ISH L I N ES

Figs 4-3 and 4-4 Two principal types of f1nish line, linear I Fig 4-1 and area I Fig 4-4). Tooth preparation with a linear finish line ends on a distinct line for its entire circumference. An area finish adapts the tooth preparation to the entire surface rather than to an exact li ne .

..commonly found under old fixed dental restorations.

subject to distortion and tension.s However, area in­

Although feather and knife edges are valid finish

ish lines are sometimes the best clinical solution dur­

lines that require the removal of dental tissue and

ing the surgical stage for cases of advanced peri­

the definition of form and volume, they are used

odontal disease that require a fixed dental prosthe­

less frequently in current clinical practice. It is the

sis.6 Area inish lines may also be useful for con­

authors' opinion, however, that a mediocre area fin ­

necting several restorative crowns together to stabi­

ish line is preferable to a mediocre linear inish line.

lize dental movement in the presence of signiicant­

With an area finish line (Fig 4-5), the marginal seal

ly reduced periodontal support.7 In �uch a situation,

will be more sure, whereas an inadequate linear fin­

it would be impossible to splint many crowns pre­

ish line inevitably produces a significant gap at the

pared, for example, with a shoulder design because

restoration margin (Fig 4-6).

of the lack of space between the tooth abutments

The main problem with area finish lines is that,

during the laboratory work and because of a prob­

given the preparation space and the thickness of re­

lem with the angles and planes. Although area finish

storative materials, they are suitable only for crowns

lines yield good marginal adaptation, the authors

with metal collars. furthermore, the thickness of the

prefer, even in such a case, to perform seconday

restorations at the margin does not meet minimum

welds once the margins are closed individually on

recommended values for laboratory procedures,

chamfer, modified chamfer, or other linear finish lines

which may result in a margin that is weak and thus

110

(Figs 4-7 and 4-8).8.9

Fig 4-5 1ncorrect area finish line. The obvious convexity of this preparation in profile creates an undercut. which presents a drawback for both adaptation and insertion of the prosthesis.

.

Fig4-6 Evident gap from the matching of an inadequate linear finish line to an ill-fitting metal margin. The same error for an area fin­ ish line is more acceptable because the seal covers an entire area of the surface instead of just a line. Figs 4-7 and 4-8 Clinical case of a patient with advanced periodontal disease and considerable buccal flaring of the teeth. The teeth were realigned through orthodontic and periodontal treatment and required a fixed prosthesis. The treatment aimed to cause u lit­ tle damage to the pulp as possible. Ceramic crowns were made individually and united using secondary welds i n three sections equipped with interlock devices. The area for the secondary weld was prepared by the dental technician along with the waxing of the framework and ceramic coating of the connections. The welding was completed only after the ceramic was applied.

1t1

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

�

Area finish lines

occlusal force. The authors avoid this type of finish

Area finish lines (Fig 4-9 to 4-11), both feather- and

vanced periodontal disease, finish lines that include

knife-edged, offer several advantages clinically and in

a minimal angle to properly support the restorative

the laboratory. The angle between the axial wall and

materials.

line when possible, preferring, even in cases of ad­

the radicular wall is near or slightly less than 180 degrees. Clinicians distinguish between a feather edge,

Linear finish lines

with an angle of approximately 180 degrees, and a knife edge, with an angle slightly less than 180

The following distinctions can be made between

degrees. Area finish lines are relatively easy to com­

preparations with a linear finish lines. Complex linear

plete because the operator does not have to focus on

finish lines have a beveled shoulder or a beveled

creating a distinct linear finish line, thus reducing the

chamfer. Simple linear finish lines have a so- or 135-

clinician's stress and fatigue. However, circular and

degree shoulder, a classic chamfer, a rounded shoul­

rotational movements and the use of small-diameter

der, a 90-degree shoulder, or a modified chamfer.

burs should be avoided during the preparation to

112

prevent irregular surfaces, conical tooth preparations,

Complex, Beveled chamfer and beveled shoulder

or overheating of the pulp.

Although complex finish lines require the formation of

The area inish line is indicated for fixed dental

an angle, they are addressed first because their bevel

restorations i n periodontal cases, for intraoperative

is, in some ways, similar to the area finish lines. The

dental preparation, and for multiple fixed restora­

beveled chamfer inish line is often cited i n the liter­

tions. It is the authors' belief that because of modern

ature but rarely used in clinical practice. Given its

implant technology, full-mouth fixed restorations

similarity to the beveled shoulder design, it will be

should be avoided, and instead connecting and link­

included in the analysis of the beveled shoulder.

ing should take place for partial segments. This has

The beveled shoulder finish line is complex be­

clear advantages for precision in all operative stages,

cause the design is obtained through the intersection

not least in the cementation stage.

of two lines, but this finish line provides no clear

FIG 4-10

FIG 4-9

FIG 4-1 1

Fig 4- g Cross section o f a tooth preparation with a n area finish line. The near absence o f a definitive line permits a strong seal at the restoration margin.

Fig 4-10 Area finish line completed with a flame-shaped bur. I n the authors' view. the shape of this bur i s wrong for creating an area finish line. Fig 4-11 Use of a large-diameter conical cham fe r b u r i s generally recommended for area finish lines.

�

years of experience. This finish line reduces the

gina I adaptation. Bevels with angles greater than 70

amount of exposed cement. which would seem to

degrees require edges so thin that the stability can­

Area inish lines also have several disadvantages.

advantage over less dificult designs (Fig 4-12). The

indicate a better marginal seal."·" On the other

not be checked during the working stages. and any

Excellent esthetics are unlikely to result from an area

beveled shoulder can be accomplished in two ways.

hand, a finish line with an internal angle close to 90

openings or distortions i n the restorative margins

inish line because the thin area of support at the fin­

In one case, the entire preparation is executed using

degrees could impede the normal cement flow,

cannot be corrected in subsequent stages. Moreover,

ish line is insuicient for ceramic material, with or

a 90-degree bur, and, after the shoulder is made, the

especially under conditions of abnormal fluidity,'J

such edges lose their shape during laboratory pro­

without metal margins. Therefore, a metallic border of

exterior finish line is rounded off until the desired

and result in occlusal lifting.

cedures or because of occlusal force.8

significant height is needed, making the cervical area

bevel is formed (Figs 4-13 and 4-14). The other tech­

One possible advantage of the bevel is that it

less esthetic. Horizontally, the space is too limited to

Another point made in the literature' in fa vor of

nique involves first designing the finish line with a

could be used i n conjunction with the shoulder to

beveled finish lines is the possibility of burnishing

ofer proper support for any restorative material

long chamfer (this will later constitute the bevel), and

because of the minimal angle that is created with the

combine the benefits of a greater support area of

the margin a fter cementation by using rotating burs

then using a 90-degree bur to execute the shoulder

axial wall. The stress that is distributed to this finish

the shoulder and the ferrule efect of the bevel.

at low speed. The authors believe that, from a prac­

in the internal portion of the chamfer (Fig 4-15).

According to Mclean and Wilson,'4 however, the

tical standpoint, this is impossible because of the

line exceeds that of other types of finish lines'0 and

In analyzing the advantages of this finish line, the

results in distortion of the thin metal at the margin of

angle of the bevel must be at least 45 degrees to

subgingival extension of the restoration margins and

authors find it impossible to confine their discussion

the restoration during iring or when subjected to

obtain the retention and ferrule efects. but only

the likelihood of damaging the metallic margins.

to theoretical concepts without drawing upon their ..

bevels with more than 70 degrees improve the mar-

..

113

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

�

Area finish lines

occlusal force. The authors avoid this type of finish

Area finish lines (Fig 4-9 to 4-11), both feather- and

vanced periodontal disease, finish lines that include

knife-edged, offer several advantages clinically and in

a minimal angle to properly support the restorative

the laboratory. The angle between the axial wall and

materials.

line when possible, preferring, even in cases of ad­

the radicular wall is near or slightly less than 180 degrees. Clinicians distinguish between a feather edge,

Linear finish lines

with an angle of approximately 180 degrees, and a knife edge, with an angle slightly less than 180

The following distinctions can be made between

degrees. Area finish lines are relatively easy to com­

preparations with a linear finish lines. Complex linear

plete because the operator does not have to focus on

finish lines have a beveled shoulder or a beveled

creating a distinct linear finish line, thus reducing the

chamfer. Simple linear finish lines have a so- or 135-

clinician's stress and fatigue. However, circular and

degree shoulder, a classic chamfer, a rounded shoul­

rotational movements and the use of small-diameter

der, a 90-degree shoulder, or a modified chamfer.

burs should be avoided during the preparation to

112

prevent irregular surfaces, conical tooth preparations,

Complex, Beveled chamfer and beveled shoulder

or overheating of the pulp.

Although complex finish lines require the formation of

The area inish line is indicated for fixed dental

an angle, they are addressed first because their bevel

restorations i n periodontal cases, for intraoperative

is, in some ways, similar to the area finish lines. The

dental preparation, and for multiple fixed restora­

beveled chamfer inish line is often cited i n the liter­

tions. It is the authors' belief that because of modern

ature but rarely used in clinical practice. Given its

implant technology, full-mouth fixed restorations

similarity to the beveled shoulder design, it will be

should be avoided, and instead connecting and link­

included in the analysis of the beveled shoulder.

ing should take place for partial segments. This has

The beveled shoulder finish line is complex be­

clear advantages for precision in all operative stages,

cause the design is obtained through the intersection

not least in the cementation stage.

of two lines, but this finish line provides no clear

FIG 4-10

FIG 4-9

FIG 4-1 1

Fig 4- g Cross section o f a tooth preparation with a n area finish line. The near absence o f a definitive line permits a strong seal at the restoration margin.

Fig 4-10 Area finish line completed with a flame-shaped bur. I n the authors' view. the shape of this bur i s wrong for creating an area finish line. Fig 4-11 Use of a large-diameter conical cham fe r b u r i s generally recommended for area finish lines.

�

years of experience. This finish line reduces the

gina I adaptation. Bevels with angles greater than 70

amount of exposed cement. which would seem to

degrees require edges so thin that the stability can­

Area inish lines also have several disadvantages.

advantage over less dificult designs (Fig 4-12). The

indicate a better marginal seal."·" On the other

not be checked during the working stages. and any

Excellent esthetics are unlikely to result from an area

beveled shoulder can be accomplished in two ways.

hand, a finish line with an internal angle close to 90

openings or distortions i n the restorative margins

inish line because the thin area of support at the fin­

In one case, the entire preparation is executed using

degrees could impede the normal cement flow,

cannot be corrected in subsequent stages. Moreover,

ish line is insuicient for ceramic material, with or

a 90-degree bur, and, after the shoulder is made, the

especially under conditions of abnormal fluidity,'J

such edges lose their shape during laboratory pro­

without metal margins. Therefore, a metallic border of

exterior finish line is rounded off until the desired

and result in occlusal lifting.

cedures or because of occlusal force.8

significant height is needed, making the cervical area

bevel is formed (Figs 4-13 and 4-14). The other tech­

One possible advantage of the bevel is that it

less esthetic. Horizontally, the space is too limited to

Another point made in the literature' in fa vor of

nique involves first designing the finish line with a

could be used i n conjunction with the shoulder to

beveled finish lines is the possibility of burnishing

ofer proper support for any restorative material

long chamfer (this will later constitute the bevel), and

because of the minimal angle that is created with the

combine the benefits of a greater support area of

the margin a fter cementation by using rotating burs

then using a 90-degree bur to execute the shoulder

axial wall. The stress that is distributed to this finish

the shoulder and the ferrule efect of the bevel.

at low speed. The authors believe that, from a prac­

in the internal portion of the chamfer (Fig 4-15).

According to Mclean and Wilson,'4 however, the

tical standpoint, this is impossible because of the

line exceeds that of other types of finish lines'0 and

In analyzing the advantages of this finish line, the

results in distortion of the thin metal at the margin of

angle of the bevel must be at least 45 degrees to

subgingival extension of the restoration margins and

authors find it impossible to confine their discussion

the restoration during iring or when subjected to

obtain the retention and ferrule efects. but only

the likelihood of damaging the metallic margins.

to theoretical concepts without drawing upon their ..

bevels with more than 70 degrees improve the mar-

..

113

CH�PTER 4 Finish Line Designs for Complete Crown Preparations

.

Among the shortcomings of this complex design

tal tissues and enables the clinician to prepare a

is the difficulty of adequately establishing the finish

subgingival margin without retracting the gingiva. For

line, realizing it equally on all sides of the tooth,

cases in which a retraction cord is not used in the

and taking impressions of the bevel. The clinician is

initial stage of preparation, this technique may be

required to use a high degree of concentration to

used to position an intrasulcular restoration margin.

precisely define the position of two lines and the exact spacing between them.

Because more than one third of the longitudinal

The design of the most exterior portion of the fin·

area, this preparation design considerably reduces the surface retention for the crown. The area of the

material. To provide suficient resistance against the

preparation that usually provides the greatest sup­

flexure forces that are generated at the margin, it is

port (that is, the area with the largest diameter and

necessary to use a metal edge to seal the margin,

hence the greatest surface area) is very conical in

which provides less than optimal esthetics. More­

this design because the finish line develops on a

over, the thin metal edges used with bevels of

slant (Figs 4-17 and 4-18).21 The conical shape makes

angles greater than 70 degrees have a tendency to

this technique unsuitable for teeth of reduced height

lose their shape during laboratory preparation or

but advisable for splinted prostheses connecting

because of the vey high marginal stress during

multiple teeth.

The authors believe that this type of complex fin­

In the authors' view, this finish line represents an evolutionary step, in esthetic terms, from area finish

ish line is now obsolete because it is difficult to

lines. Nonetheless, the so- and 135-degree shoul­

master, requires considerable dexterity and concen­

ders are outdated because they do not provide a

tration and does not provide the benefits it was

suficient zone of support for newer esthetic restora­

designed to furnish.'S-18 Moreover, most patients con­

tion materials with ceramic margins (Fig 4-19).

sider the visible metal margin unesthetic.

·.

axis of the prepared tooth consists of the finish line

ish line provides insuficient support for all-ceramic

occlusion.8

\

For this design, the best esthetic results can be achieved with the ceramic micromargin, a restora­

Simple: 50- and 1 35-degree shoulder

tion margin of metal that is coated in an opaque

The 50- and 135-degree shoulders are simple finish

material and then layered in ceramic. This complex

lines. They are based on the plane of reference used

technique requires the use of a microscope in the

to measure the size of the angle, either the hori­

laboratoy and a dental technician who has experi­

zontal or longitudinal axis of the toothl4-t9 (Fig 4-16).

ence working at high magnification. All three types

The popularity of this type of finish line during the

of restorative materials are used in this margin, pro­

198os and 1990s is largely due to the studies con­

viding the advantages of a metal closure and con­

ducted by Kuwatas and by Martignoni and Shonen­

ventional cementation along with the esthetics of a

berger20 as well as its intrinsic simplicity.

ceramic margin. The greatest problem is how to fit

Visibility while working with the bur is excellent.

the three materials in such a small space; it is

The clinician may immediately determine the final

almost impossible without resorting to horizontal

angle and shape of the preparation by using half the

contours, although these are of limited extension

diameter of the instrument, held vetically. The bur's

and are clinically insignificant if reduced correctly.

ig 4-12 Cross section of a tooth prepared with complex beveled shoulder finish line.

Fig 4-13 Thin flame-shaped bur. 2.5 m m long. used to prepare the finish line without interfering with the walls of the tooth preparation itself or with the adjacent tooth. Fig 4-14 Small-diameter football-shaped tungsten carbide bur used to make a shorter. concave bevel. -

Fig 4-15 Beveled shoulder finish line may be completed even after preparation of a long chamfer by shifting the shoulder internally with degree bur.

1

90-

pointed shape causes minimal damage to periodon-

114 115

CH�PTER 4 Finish Line Designs for Complete Crown Preparations

.

Among the shortcomings of this complex design

tal tissues and enables the clinician to prepare a

is the difficulty of adequately establishing the finish

subgingival margin without retracting the gingiva. For

line, realizing it equally on all sides of the tooth,

cases in which a retraction cord is not used in the

and taking impressions of the bevel. The clinician is

initial stage of preparation, this technique may be

required to use a high degree of concentration to

used to position an intrasulcular restoration margin.

precisely define the position of two lines and the exact spacing between them.

Because more than one third of the longitudinal

The design of the most exterior portion of the fin·

area, this preparation design considerably reduces the surface retention for the crown. The area of the

material. To provide suficient resistance against the

preparation that usually provides the greatest sup­

flexure forces that are generated at the margin, it is

port (that is, the area with the largest diameter and

necessary to use a metal edge to seal the margin,

hence the greatest surface area) is very conical in

which provides less than optimal esthetics. More­

this design because the finish line develops on a

over, the thin metal edges used with bevels of

slant (Figs 4-17 and 4-18).21 The conical shape makes

angles greater than 70 degrees have a tendency to

this technique unsuitable for teeth of reduced height

lose their shape during laboratory preparation or

but advisable for splinted prostheses connecting

because of the vey high marginal stress during

multiple teeth.

The authors believe that this type of complex fin­

In the authors' view, this finish line represents an evolutionary step, in esthetic terms, from area finish

ish line is now obsolete because it is difficult to

lines. Nonetheless, the so- and 135-degree shoul­

master, requires considerable dexterity and concen­

ders are outdated because they do not provide a

tration and does not provide the benefits it was

suficient zone of support for newer esthetic restora­

designed to furnish.'S-18 Moreover, most patients con­

tion materials with ceramic margins (Fig 4-19).

sider the visible metal margin unesthetic.

·.

axis of the prepared tooth consists of the finish line

ish line provides insuficient support for all-ceramic

occlusion.8

\

For this design, the best esthetic results can be achieved with the ceramic micromargin, a restora­

Simple: 50- and 1 35-degree shoulder

tion margin of metal that is coated in an opaque

The 50- and 135-degree shoulders are simple finish

material and then layered in ceramic. This complex

lines. They are based on the plane of reference used

technique requires the use of a microscope in the

to measure the size of the angle, either the hori­

laboratoy and a dental technician who has experi­

zontal or longitudinal axis of the toothl4-t9 (Fig 4-16).

ence working at high magnification. All three types

The popularity of this type of finish line during the

of restorative materials are used in this margin, pro­

198os and 1990s is largely due to the studies con­

viding the advantages of a metal closure and con­

ducted by Kuwatas and by Martignoni and Shonen­

ventional cementation along with the esthetics of a

berger20 as well as its intrinsic simplicity.

ceramic margin. The greatest problem is how to fit

Visibility while working with the bur is excellent.

the three materials in such a small space; it is

The clinician may immediately determine the final

almost impossible without resorting to horizontal

angle and shape of the preparation by using half the

contours, although these are of limited extension

diameter of the instrument, held vetically. The bur's

and are clinically insignificant if reduced correctly.

ig 4-12 Cross section of a tooth prepared with complex beveled shoulder finish line.

Fig 4-13 Thin flame-shaped bur. 2.5 m m long. used to prepare the finish line without interfering with the walls of the tooth preparation itself or with the adjacent tooth. Fig 4-14 Small-diameter football-shaped tungsten carbide bur used to make a shorter. concave bevel. -

Fig 4-15 Beveled shoulder finish line may be completed even after preparation of a long chamfer by shifting the shoulder internally with degree bur.

1

90-

pointed shape causes minimal damage to periodon-

114 115

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

Taking an impression of the finish line contours

it is decidedly m o re versatile than both and less de­

The classic chamfer is a finish line that generally

palatal levels, which is accentuated in natural teeth,

is also difficult. A shoulder finish line with an under·

manding of the clinician's effort and time (Fig 4-40).

exploits the absence of a sharp internal angle and is

make it impossible to achieve exact adaptation with

lying "horizontal plate" design may stress the im­

To execute a modified chamfer, the clinician may

defined as long or short, according to the degree of

this design.

pression material's resistance to tearing when the

use half the diameter of the diamond bur to mea­

impression is removed from the mouth. Therefore, it

sure the reduction, keeping the finish line a s close

. Simple. Classtc chamfer

.

shoulders and the differences in the buccal and

concavity in the preparation (Fig 4-20). This design

The popularity of this finish line is driven by

is easy to execute, in practical clinical terms, and

patients' continuing demand for improved esthetics.

is more dificult to make a clear impression with an

as possible to the center of the bur (Fig 4-41). This

can be adapted to various restoration scenarios

The drive for esthetics has resulted in widespread

intact tooth structure beyond the finish line, com­

design may be used for various restorative materi­

(Figs 4-21 to 4-23). The classic chamfer is ideal for

use of all-ceramic crowns and the popularity of

pared with a more vertical or a slanted finish line

als, and it leaves the type of margin open to decision

teeth with substantial differences in buccal and lin­

implant-supported prostheses, which have greatly

design.

at any stage of treatment, even after the i m p ression

gual levels or multiple connected restorations. The

improved the esthetics of restorative solutions for

restoration margins endure reduced stress because

the edentulous. For these reasons, especially i n

S i m ple: 90-degree shoulder

applicable to any type of restoration margin. With

the occlusal force is more evenly distributed over

recent years, restorations have become more depen·

The last of the common finish lines is the go-degree

the proper area of support executed by the clinician,

has been made. This finish line is thus u niversally

the entire restoration. The finish line cannot take a

dent on adhesives rather than metal structural sup­

shoulder (Figs 4-33 to 4-3s). Though still discussed,

this design can accept all-ceramic crowns, metal­

collarless metal-ceramic restoration but works with a

ports. Clinicians now use porcelain laminate veneers

the 90-degree shoulder finish line has been sup­

ceramic crowns, collarless metal-ceramic, or metal­

metal margin or micromargin. However, the dental

or all-ceramic crowns on nonvital teeth reconstruct­

planted by the rounded shoulder design for practi­

ceramic crowns with a metallic margin or micromar­

technician has difficulty controlling the stability of

ed with fiberglass dowels. For larger edentulous

cal and ergonomic reasons. Moreover, the diamond

gin (Figs 4-42 to 4-44).

the metal, resulting in frequent distortions during

areas, small fixed partial dentures are being made

at the vey tip of the new bur is the first to be dis­

The micromargin may be used because clinicians

firing.22

using the collarless technique" or with a structure

lodged during the rotating impact, thus impeding

have found that a so-degree bur is the least dam­ aging to the periodontal tissues during the defini­

This preparation has many of the same charac­

of nonmetallic materials. With ample support at the

the formation of a sharp angle (Figs 4-36 and 4-37).

teristics as the so-degree finish line, as well as some

marginal level, the clinician may use all-ceramic

However, this design is still used when the clinical

tion of the finish line and permits a restoration at

improvements owing to the concave design. This dif­

restorations with this finish line. Feldspathic ce­

crown of a short tooth cannot be surgically length­

the critical angleS where metal, opaque, and ceram­

ference allots more space for the restorative materi­

ramic crowns impart the most esthetically pleasing

ened or orthodontically extruded. In such a case, the

ic layers meet. In addition to the esthetic problems

als and improves the esthetics. However, the greater

effect, but crowns with an alumina core or pressable

90-degree shoulder is the only finish line that per­

related to the limited space available for the ceram­

lateral or external extension of the rotation of the

ceramic crowns ofer better function, especially ater

mits maximum surface retention. This finish line is

ic, described earlier, the authors believe that an

diamond bur causes slightly more damage to the

cementation, combined with long-term resistance to

also frequently used for ceramic inlay preparations

angle of this size does not have room for adequate

gingival tissue.

occlusal force (Figs 4-29 and 4-30).

(Figs 4-38 and 4-39). Although clinicians no longer

metal material. If the metal is not sufficient, the den­

For the clinician, this design is not easy to exe­

use this design for complete crown restorations, any

tal technician will ace problems of instability during

Simple: Short chamfer or rounded shoulder

cute. The center of the rounded bur is difficult to

clinician doing prosthetic work would be advised to

the various firing cycles and a margin design that

Deepening the chamfer by using a more rounded

identify, and, because measurment is compromised,

become familiar with it and learn how to position

cannot absorb the tensions caused by the crystal

point produces a short chamfer or rounded shoulder

excessive abrasion along the axial surface can result

and finish this well-defined finish line.

lattice of the alloy.'4

finish line, which is currently the design most fre­

in weakened areas that lack support and give an

quently used in US dental schools' (Figs 4-24 to

undesirable curl to the finish line (Figs 4-31 and

Simple: Modified chamfer

adaptation, Massironi et at'S perfected a technique known as the counter-chamfer that involves increas­

To stabilize the metal during iring for a precise

4-28). The short chamfer finish line is a modern

4-32). This obstacle creates considerable difficulty,

The design known as the modied chamfer was

version of the long chamfer, developed to meet de­

sometimes preventing the dental technician from

created to provide adequate space for all kinds of

ing the thickness of the metal used for the restora­

mands for better esthetics at the expense of some

producing a precise prosthesis. Above all, the pres­

restorations and to leave the decision of the restora­

tion margin, which is a medium title, 54% gold

functional features. The shot chamfer creates greater

ence of a curl creates a fragile area in the margin,

tion margin open at every stage of treatment.'l The

(BegoStar, Bego), creating a slightly convex shape.

difficulties in connecting several crowns and in using

which may break during use and can even lead to

modified chamfer finish line is described as a long

While this technique works admirably to increase

certain metal alloys. In cases where several prepared

secondary caries.

chamfer combined with a rounded shoulder, though

the stability of the metal, it further reduces the ..

teeth are connected, the presence of numerous flat

..

111 117

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

Taking an impression of the finish line contours

it is decidedly m o re versatile than both and less de­

The classic chamfer is a finish line that generally

palatal levels, which is accentuated in natural teeth,

is also difficult. A shoulder finish line with an under·

manding of the clinician's effort and time (Fig 4-40).

exploits the absence of a sharp internal angle and is

make it impossible to achieve exact adaptation with

lying "horizontal plate" design may stress the im­

To execute a modified chamfer, the clinician may

defined as long or short, according to the degree of

this design.

pression material's resistance to tearing when the

use half the diameter of the diamond bur to mea­

impression is removed from the mouth. Therefore, it

sure the reduction, keeping the finish line a s close

. Simple. Classtc chamfer

.

shoulders and the differences in the buccal and

concavity in the preparation (Fig 4-20). This design

The popularity of this finish line is driven by

is easy to execute, in practical clinical terms, and

patients' continuing demand for improved esthetics.

is more dificult to make a clear impression with an

as possible to the center of the bur (Fig 4-41). This

can be adapted to various restoration scenarios

The drive for esthetics has resulted in widespread

intact tooth structure beyond the finish line, com­

design may be used for various restorative materi­

(Figs 4-21 to 4-23). The classic chamfer is ideal for

use of all-ceramic crowns and the popularity of

pared with a more vertical or a slanted finish line

als, and it leaves the type of margin open to decision

teeth with substantial differences in buccal and lin­

implant-supported prostheses, which have greatly

design.

at any stage of treatment, even after the i m p ression

gual levels or multiple connected restorations. The

improved the esthetics of restorative solutions for

restoration margins endure reduced stress because

the edentulous. For these reasons, especially i n

S i m ple: 90-degree shoulder

applicable to any type of restoration margin. With

the occlusal force is more evenly distributed over

recent years, restorations have become more depen·

The last of the common finish lines is the go-degree

the proper area of support executed by the clinician,

has been made. This finish line is thus u niversally

the entire restoration. The finish line cannot take a

dent on adhesives rather than metal structural sup­

shoulder (Figs 4-33 to 4-3s). Though still discussed,

this design can accept all-ceramic crowns, metal­

collarless metal-ceramic restoration but works with a

ports. Clinicians now use porcelain laminate veneers

the 90-degree shoulder finish line has been sup­

ceramic crowns, collarless metal-ceramic, or metal­

metal margin or micromargin. However, the dental

or all-ceramic crowns on nonvital teeth reconstruct­

planted by the rounded shoulder design for practi­

ceramic crowns with a metallic margin or micromar­

technician has difficulty controlling the stability of

ed with fiberglass dowels. For larger edentulous

cal and ergonomic reasons. Moreover, the diamond

gin (Figs 4-42 to 4-44).

the metal, resulting in frequent distortions during

areas, small fixed partial dentures are being made

at the vey tip of the new bur is the first to be dis­

The micromargin may be used because clinicians

firing.22

using the collarless technique" or with a structure

lodged during the rotating impact, thus impeding

have found that a so-degree bur is the least dam­ aging to the periodontal tissues during the defini­

This preparation has many of the same charac­

of nonmetallic materials. With ample support at the

the formation of a sharp angle (Figs 4-36 and 4-37).

teristics as the so-degree finish line, as well as some

marginal level, the clinician may use all-ceramic

However, this design is still used when the clinical

tion of the finish line and permits a restoration at

improvements owing to the concave design. This dif­

restorations with this finish line. Feldspathic ce­

crown of a short tooth cannot be surgically length­

the critical angleS where metal, opaque, and ceram­

ference allots more space for the restorative materi­

ramic crowns impart the most esthetically pleasing

ened or orthodontically extruded. In such a case, the

ic layers meet. In addition to the esthetic problems

als and improves the esthetics. However, the greater

effect, but crowns with an alumina core or pressable

90-degree shoulder is the only finish line that per­

related to the limited space available for the ceram­

lateral or external extension of the rotation of the

ceramic crowns ofer better function, especially ater

mits maximum surface retention. This finish line is

ic, described earlier, the authors believe that an

diamond bur causes slightly more damage to the

cementation, combined with long-term resistance to

also frequently used for ceramic inlay preparations

angle of this size does not have room for adequate

gingival tissue.

occlusal force (Figs 4-29 and 4-30).

(Figs 4-38 and 4-39). Although clinicians no longer

metal material. If the metal is not sufficient, the den­

For the clinician, this design is not easy to exe­

use this design for complete crown restorations, any

tal technician will ace problems of instability during

Simple: Short chamfer or rounded shoulder

cute. The center of the rounded bur is difficult to

clinician doing prosthetic work would be advised to

the various firing cycles and a margin design that

Deepening the chamfer by using a more rounded

identify, and, because measurment is compromised,

become familiar with it and learn how to position

cannot absorb the tensions caused by the crystal

point produces a short chamfer or rounded shoulder

excessive abrasion along the axial surface can result

and finish this well-defined finish line.

lattice of the alloy.'4

finish line, which is currently the design most fre­

in weakened areas that lack support and give an

quently used in US dental schools' (Figs 4-24 to

undesirable curl to the finish line (Figs 4-31 and

Simple: Modified chamfer

adaptation, Massironi et at'S perfected a technique known as the counter-chamfer that involves increas­

To stabilize the metal during iring for a precise

4-28). The short chamfer finish line is a modern

4-32). This obstacle creates considerable difficulty,

The design known as the modied chamfer was

version of the long chamfer, developed to meet de­

sometimes preventing the dental technician from

created to provide adequate space for all kinds of

ing the thickness of the metal used for the restora­

mands for better esthetics at the expense of some

producing a precise prosthesis. Above all, the pres­

restorations and to leave the decision of the restora­

tion margin, which is a medium title, 54% gold

functional features. The shot chamfer creates greater

ence of a curl creates a fragile area in the margin,

tion margin open at every stage of treatment.'l The

(BegoStar, Bego), creating a slightly convex shape.

difficulties in connecting several crowns and in using

which may break during use and can even lead to

modified chamfer finish line is described as a long

While this technique works admirably to increase

certain metal alloys. In cases where several prepared

secondary caries.

chamfer combined with a rounded shoulder, though

the stability of the metal, it further reduces the ..

teeth are connected, the presence of numerous flat

..

111 117

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

TOOTH METHACRY­ LATE RESIN

Fig 4-16 Cross section of a 50-degree shoulder. Fig 4-17 Coarse-grit bur used to create a 50-degree shoulder on an extracted tooth.

Fig 4-18 Fine-grit bur used to create a 50-degree shoulder on an extracted tooth. This design exhibits low retention. The use of collarless metal-ceramic restorative materials is impossible. Fig 4-1 g A cross section of a 50-degree shoulder photographed through the microscope under polarized light. The preparation records the negative image of the bur used to abrade the tooth.

118

Fig 4-20 Cross section showing the slight concavity of the classic long chamfer design. which permits better esthetics than the 50-degree shoulder design. Figs 4-21 and 4-22 Coarse- and fine-grit round burs. used for preliminary preparation and finishing, respectively. of the classic chamfer. Fig 4-23 Cross section of a metal-ceramic restoration with a long chamfer design.

119

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

TOOTH METHACRY­ LATE RESIN

Fig 4-16 Cross section of a 50-degree shoulder. Fig 4-17 Coarse-grit bur used to create a 50-degree shoulder on an extracted tooth.

Fig 4-18 Fine-grit bur used to create a 50-degree shoulder on an extracted tooth. This design exhibits low retention. The use of collarless metal-ceramic restorative materials is impossible. Fig 4-1 g A cross section of a 50-degree shoulder photographed through the microscope under polarized light. The preparation records the negative image of the bur used to abrade the tooth.

118

Fig 4-20 Cross section showing the slight concavity of the classic long chamfer design. which permits better esthetics than the 50-degree shoulder design. Figs 4-21 and 4-22 Coarse- and fine-grit round burs. used for preliminary preparation and finishing, respectively. of the classic chamfer. Fig 4-23 Cross section of a metal-ceramic restoration with a long chamfer design.

119

I CHAPTER 4 Finish Line Designs for Complete Crown Preparations

\

i

I

Fig 4-24 Rounded burs in coarse and fine grit and in 0.14- and 0.1 6-mm diameters. used for the shoulder design. Figs 4-15 o. 4-18 Different diameters are � sed for the interproximal spaces and for the palatal and buccal areas. and different grits are used . for prellmmary reductiOn and for fmosh1ng. The short chamfer or rounded shoulder finish line produces the ideal support for feldspathic ceramic and all-ceramic restorations.

10

Figs 4-19 and 4-30 Frontal and sagittal views of a prepared central incisor. The spatial proportions of the tooth are maintained by removing an adequate amount of tooth from the correct areas. The different positions of the buccal and palatal shoulders result from the natural differ­ ence in levels.

Figs 4-31 and 4-31 Excessive longitudinal abrasion of the bur and the loss of a measurement reference can result i n a curled finish line design that can not be adequately supported and is likely lo break under occlusal force. lt is also difficult for a dental technician lo fabricate a restoration for this type of incorrect finish line preparation.

121

I CHAPTER 4 Finish Line Designs for Complete Crown Preparations

\

i

I

Fig 4-24 Rounded burs in coarse and fine grit and in 0.14- and 0.1 6-mm diameters. used for the shoulder design. Figs 4-15 o. 4-18 Different diameters are � sed for the interproximal spaces and for the palatal and buccal areas. and different grits are used . for prellmmary reductiOn and for fmosh1ng. The short chamfer or rounded shoulder finish line produces the ideal support for feldspathic ceramic and all-ceramic restorations.

10

Figs 4-19 and 4-30 Frontal and sagittal views of a prepared central incisor. The spatial proportions of the tooth are maintained by removing an adequate amount of tooth from the correct areas. The different positions of the buccal and palatal shoulders result from the natural differ­ ence in levels.

Figs 4-31 and 4-31 Excessive longitudinal abrasion of the bur and the loss of a measurement reference can result i n a curled finish line design that can not be adequately supported and is likely lo break under occlusal force. lt is also difficult for a dental technician lo fabricate a restoration for this type of incorrect finish line preparation.

121

CHAPil ' Finish Line Designs for Complete Crown Preparations

Fig 4-33 Simple 90-degree shoulder finish line. This design provides support for maximum esthetics and retention. Figs 4-4 and 4-35 Buccal and palatal views of a 90-degree shoulder.

Figs 4-36 and 4-37 Cross section of a tooth illustrating the proximity of the prepared area to the pulp chamber. AI higher magnification. it is pos.s1ble to see the slight round1ng of the Internal angle. which occurs because the diamond on the very tip of the bur tends to come loose rapidly.

12

Figs 4-38 and 4-39 Ninety-degree shoulder design could be ideal for preparations with little retention. for extrasulcular preparations. a n d for restorations using ceramic or resin composite onlays.

Fig 4-40 Cross section of a tooth prepared with a modified chamfer design. Fig 4-41 Preparation of a modified chamfer finish line. The clinician must keep the bur in contact with the surface being prepared. along the lon­ gitudinal axis of the tooth. When working on long or surgically lengthened teeth. the finish line looks like a small or mini chamfer. whereas for short teeth or to address esthetic concerns. the modified chamfer looks like a rounded-off shoulder.

12]

CHAPil ' Finish Line Designs for Complete Crown Preparations

Fig 4-33 Simple 90-degree shoulder finish line. This design provides support for maximum esthetics and retention. Figs 4-4 and 4-35 Buccal and palatal views of a 90-degree shoulder.

Figs 4-36 and 4-37 Cross section of a tooth illustrating the proximity of the prepared area to the pulp chamber. AI higher magnification. it is pos.s1ble to see the slight round1ng of the Internal angle. which occurs because the diamond on the very tip of the bur tends to come loose rapidly.

12

Figs 4-38 and 4-39 Ninety-degree shoulder design could be ideal for preparations with little retention. for extrasulcular preparations. a n d for restorations using ceramic or resin composite onlays.

Fig 4-40 Cross section of a tooth prepared with a modified chamfer design. Fig 4-41 Preparation of a modified chamfer finish line. The clinician must keep the bur in contact with the surface being prepared. along the lon­ gitudinal axis of the tooth. When working on long or surgically lengthened teeth. the finish line looks like a small or mini chamfer. whereas for short teeth or to address esthetic concerns. the modified chamfer looks like a rounded-off shoulder.

12]

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

MODIFIED

CHAMFER

P R E P A R AT I O N

SYSTEM

Modified chamfer design

Figs 4-42 o 4-4 Modified chamfer is versatile and can be adapted to all kinds of restoration margins, all-ceramic (Fig 4-42!. ceramic shoul­ der. metallic margin (Fig 4-43). and metal-ceramic micromargin (Fig 4-44).

.. amount of space available for the esthetic material.

and 0.18 mm. Each group includes a coarse-grit (180

Therefore, a new chamfer finish line that is close to

�m) bur with a so-degree point and two modified

6o degrees has been designed, answering the need

chamfer burs of varying grits, one coarse (180 �m)

for a greater area of support for both all-ceramic and

and one fine (jo �m) (Figs 4·47 and 4-48).

metal-ceramic materials (Figs 4·4S and 4-46).

The clinician must be able to keep half of the bur in sight to define the depth and location of the fin·

Assembled preparaion

124

kis

ish line. A so-degree point diamond bur is the best

An assembled preparation kit is a procedure system

instrument for tracing the guide groove (Figs 4-49

that has instruments divided into various shapes and

and 4·so). The guide groove may also be made using

diameters for the different stages in the preparation

the modified chamfer bur.

of the finish line: guide groove creation, peripheral

In the preliminary preparation stage immediately

delimitation, and margin inishing. It is composed of

following the placement of the guide groove, the

groups of three burs with diameters of 0.14, 0.16,

clinician uses a coarse-grit modified chamfer bur to .

Fig 4-45 Counter-chamfer technique permits increased support provided by the thicker metal in the marginal area. with increased stability of the metal during firing. but reduces the space for the ceramic layer.

Fig 4-46 Modified chamfer design has an angle of roughly 60 degrees and provides better esthetics in the marginal area even if the thickness of the metal is increased from the counter-chamfer.

125

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

MODIFIED

CHAMFER

P R E P A R AT I O N

SYSTEM

Modified chamfer design

Figs 4-42 o 4-4 Modified chamfer is versatile and can be adapted to all kinds of restoration margins, all-ceramic (Fig 4-42!. ceramic shoul­ der. metallic margin (Fig 4-43). and metal-ceramic micromargin (Fig 4-44).

.. amount of space available for the esthetic material.

and 0.18 mm. Each group includes a coarse-grit (180

Therefore, a new chamfer finish line that is close to

�m) bur with a so-degree point and two modified

6o degrees has been designed, answering the need

chamfer burs of varying grits, one coarse (180 �m)

for a greater area of support for both all-ceramic and

and one fine (jo �m) (Figs 4·47 and 4-48).

metal-ceramic materials (Figs 4·4S and 4-46).

The clinician must be able to keep half of the bur in sight to define the depth and location of the fin·

Assembled preparaion

124

kis

ish line. A so-degree point diamond bur is the best

An assembled preparation kit is a procedure system

instrument for tracing the guide groove (Figs 4-49

that has instruments divided into various shapes and

and 4·so). The guide groove may also be made using

diameters for the different stages in the preparation

the modified chamfer bur.

of the finish line: guide groove creation, peripheral

In the preliminary preparation stage immediately

delimitation, and margin inishing. It is composed of

following the placement of the guide groove, the

groups of three burs with diameters of 0.14, 0.16,

clinician uses a coarse-grit modified chamfer bur to .

Fig 4-45 Counter-chamfer technique permits increased support provided by the thicker metal in the marginal area. with increased stability of the metal during firing. but reduces the space for the ceramic layer.

Fig 4-46 Modified chamfer design has an angle of roughly 60 degrees and provides better esthetics in the marginal area even if the thickness of the metal is increased from the counter-chamfer.

125

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

�

create the peripheral outline of the preparation, cor­

The complete preparation system is also avail­

recting the initial angle (Figs 4-51 and 4-52) without

able in a cylindrical version (kit TD 1272, Komet, by

altering the apical level of the finish line. The clini­

D. Massironi), which contains nine burs and is used

cian then finishes the prepared tooth using a fine­

most frequently in preparations involving a single·

grit bur of the same shape and diameter as the pre­

unit restoration or small fixed partial dentures,

vious one (Rgs 4-53 and 4-54).

where there is little space for instruments of various

The modified chamfer system preparation includes

diameters (Figs 4-60 to 4·7!l - For more extensive

a kit and two oscillating tips: the ultrasonic point kit

cases with multiple preparations or restorations for

(with two points, 0.14 and 0.16) (TO 1073A Komet

patients who have undergone crown-lengthening

with EMS instrument device) and the sonic point kit

surgery, there is a conical version (kit TD 86o,

(with two points, 0.14 and 0.16) (SF 979 Kava with

Komet, by D. Massironi). This kit, which contains six

soninex instrument) (Rg 4-55). There are also two

burs, can be very useful in helping the clinician

rounded chisels, 0.14 and 0.16 mm in diameter, for

achieve ideal parallelism between the tooth prepa­

manual use (DM1 and DM2, Deppeler) (Figs 4- 56 and

rations because of a 3-degree conicity and a diame­

4-57). The shapes and diameters of the chisels cor­

ter that is the same as the cylindrical burs (0.16 to

respond to those of the modified chamfer burs and

0.18 mm) (Rgs 4-72 to 4-80).

are specifically designed for completing the finish

The modified chamfer kit is a procedure system' l-28

line. They can be used in a clockwise or (by invert­

comprising a limited number of burs specific to pre­

ing the handpiece) counterclockwise direction (Rgs

paring a modified chamfer finish line. The burs can­

4-58 and 4-59). The chisels have a contra-angle

not be used for occlusal reduction, palatal reduction,

design that allows the user to employ the instru­

or separation, which considerably limits the cost of

ment in all areas of the preparation, provided the

the kit while still providing for the practical needs

cutting edge is kept against the shoulder, in con­

and creativity of the clinician (Fig 4-81).

junction with the longitudinal axis of the tooth. This

As stated earlier, the great advantage of this fin­

also allows the operator to check for undercuts.

ish line design lies in its versatility, which allows it

Rnishing the prepared tooth with a properly pol­

to be applied to almost every clinical situation and

ished surface is critical for making accurate impres­

with diferent types of margins, including the metal

sions. If the preparation is excessively rough, the

impression materials may tear.'6

collar (oten used in laboratory cases), metal micro­ margin coated in ceramic, collarless, and all-ceramic restorations (Rgs 4-82 to 4-15 7).

..

Figs 4-47 and 4-48 Procedure systems provide the clinician with appropriate working tools. thus reducing stress a n d working times. The prepa­ ration kit includes nine points. including two rounded chisels and two types of oscillating devices !sonic and ultrasonic). Rgs 4-4g and 4-50 Fifty-degree bur used for initial reduction. The pointed tip permits a clear view of the working area. It also causes less damage to marginal gingiva. as can be seen in the magnified view. Figs4-51 and 4-52 After the guide groove is prepared. the SO-degree shoulder !see Fig 4-46. fixed points A and 8) is rectified with a modified chamfer diamond bur tFig 4-52). thus delimiting the periphery and the shoulders final shape.

16

127

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

�

create the peripheral outline of the preparation, cor­

The complete preparation system is also avail­

recting the initial angle (Figs 4-51 and 4-52) without

able in a cylindrical version (kit TD 1272, Komet, by

altering the apical level of the finish line. The clini­

D. Massironi), which contains nine burs and is used

cian then finishes the prepared tooth using a fine­

most frequently in preparations involving a single·

grit bur of the same shape and diameter as the pre­

unit restoration or small fixed partial dentures,

vious one (Rgs 4-53 and 4-54).

where there is little space for instruments of various

The modified chamfer system preparation includes

diameters (Figs 4-60 to 4·7!l - For more extensive

a kit and two oscillating tips: the ultrasonic point kit

cases with multiple preparations or restorations for

(with two points, 0.14 and 0.16) (TO 1073A Komet

patients who have undergone crown-lengthening

with EMS instrument device) and the sonic point kit

surgery, there is a conical version (kit TD 86o,

(with two points, 0.14 and 0.16) (SF 979 Kava with

Komet, by D. Massironi). This kit, which contains six

soninex instrument) (Rg 4-55). There are also two

burs, can be very useful in helping the clinician

rounded chisels, 0.14 and 0.16 mm in diameter, for

achieve ideal parallelism between the tooth prepa­

manual use (DM1 and DM2, Deppeler) (Figs 4- 56 and

rations because of a 3-degree conicity and a diame­

4-57). The shapes and diameters of the chisels cor­

ter that is the same as the cylindrical burs (0.16 to

respond to those of the modified chamfer burs and

0.18 mm) (Rgs 4-72 to 4-80).

are specifically designed for completing the finish

The modified chamfer kit is a procedure system' l-28

line. They can be used in a clockwise or (by invert­

comprising a limited number of burs specific to pre­

ing the handpiece) counterclockwise direction (Rgs

paring a modified chamfer finish line. The burs can­

4-58 and 4-59). The chisels have a contra-angle

not be used for occlusal reduction, palatal reduction,

design that allows the user to employ the instru­

or separation, which considerably limits the cost of

ment in all areas of the preparation, provided the

the kit while still providing for the practical needs

cutting edge is kept against the shoulder, in con­

and creativity of the clinician (Fig 4-81).

junction with the longitudinal axis of the tooth. This

As stated earlier, the great advantage of this fin­

also allows the operator to check for undercuts.

ish line design lies in its versatility, which allows it

Rnishing the prepared tooth with a properly pol­

to be applied to almost every clinical situation and

ished surface is critical for making accurate impres­

with diferent types of margins, including the metal

sions. If the preparation is excessively rough, the

impression materials may tear.'6

collar (oten used in laboratory cases), metal micro­ margin coated in ceramic, collarless, and all-ceramic restorations (Rgs 4-82 to 4-15 7).

..

Figs 4-47 and 4-48 Procedure systems provide the clinician with appropriate working tools. thus reducing stress a n d working times. The prepa­ ration kit includes nine points. including two rounded chisels and two types of oscillating devices !sonic and ultrasonic). Rgs 4-4g and 4-50 Fifty-degree bur used for initial reduction. The pointed tip permits a clear view of the working area. It also causes less damage to marginal gingiva. as can be seen in the magnified view. Figs4-51 and 4-52 After the guide groove is prepared. the SO-degree shoulder !see Fig 4-46. fixed points A and 8) is rectified with a modified chamfer diamond bur tFig 4-52). thus delimiting the periphery and the shoulders final shape.

16

127

CHAPTER Finish Line Designs for Complete Crown Preparations

Rg 4-53 Bur in motion. about to modify a line traced earlier by the 50-degree bur. Rg 4-54 The preparation is finished with a fine-grit dia­ mond bur. Rg 4-55 Diamond- coated tips with a modified chamfer shape are powered by sonic and ultrasonic oscillating instruments. They can be used to reposition and complete the finish line without rotating movements. thus causing no damage to the gingiva. Rg 4-56 Manual round­ ed chosels for f1nosh1ng IDMl and DMZI. w1th shapes and diameters to match the rotating burs. The rounded chisels can work on all sides of the tooth preparations beca � se they are angled so that they can be held in the ideal positions for working in traction movement. The blades are also contra-angled. wh1ch perm1ts the�r use even 1n interproximal and other inaccessible areas. Rg 4-57 Note the congruity of shape between the rotat1ng bur and the chos � l. Rg 4-58 During completion of the finish line. the chisel must be held against the axis of the tooth. espwally to check for undercuts or 1rregulant1es 1n the preparation. Rg 4-59 Excellent finish denoting a well-controlled reduction of the prosthetic plane. 128

Rg 4-60 Clinical case of a z g -year-old woman who presented with a metal-ceramic crown on the maxillary right central incisor. three endodontically treated teeth. and numerous composite restorations. Rg 4-61 Treatment plan in cluded re-treatment of the canals and prepros­ thetic reconstruction with gold posts and cores. The posts and cores have been cemented. Rg 4-62 After an i mpression was taken in elas­ tomeric material. a master cast was fabricated in epoxy resin. Rg 4-63 High magnification reveals the shoulder obtained from a modified chamfer design. There is ample support for all-ceramic or metal-ceramic crowns.Rg 4-64 Four metallic frameworks obtained by means of 540. of gold and palladium alloy with a micromargin. Rg 4-65 After the opaque layer is brushed on. space remains for the entire margin to be covered by the esthetic ceramic material.

19

CHAPTER Finish Line Designs for Complete Crown Preparations

Rg 4-53 Bur in motion. about to modify a line traced earlier by the 50-degree bur. Rg 4-54 The preparation is finished with a fine-grit dia­ mond bur. Rg 4-55 Diamond- coated tips with a modified chamfer shape are powered by sonic and ultrasonic oscillating instruments. They can be used to reposition and complete the finish line without rotating movements. thus causing no damage to the gingiva. Rg 4-56 Manual round­ ed chosels for f1nosh1ng IDMl and DMZI. w1th shapes and diameters to match the rotating burs. The rounded chisels can work on all sides of the tooth preparations beca � se they are angled so that they can be held in the ideal positions for working in traction movement. The blades are also contra-angled. wh1ch perm1ts the�r use even 1n interproximal and other inaccessible areas. Rg 4-57 Note the congruity of shape between the rotat1ng bur and the chos � l. Rg 4-58 During completion of the finish line. the chisel must be held against the axis of the tooth. espwally to check for undercuts or 1rregulant1es 1n the preparation. Rg 4-59 Excellent finish denoting a well-controlled reduction of the prosthetic plane. 128

Rg 4-60 Clinical case of a z g -year-old woman who presented with a metal-ceramic crown on the maxillary right central incisor. three endodontically treated teeth. and numerous composite restorations. Rg 4-61 Treatment plan in cluded re-treatment of the canals and prepros­ thetic reconstruction with gold posts and cores. The posts and cores have been cemented. Rg 4-62 After an i mpression was taken in elas­ tomeric material. a master cast was fabricated in epoxy resin. Rg 4-63 High magnification reveals the shoulder obtained from a modified chamfer design. There is ample support for all-ceramic or metal-ceramic crowns.Rg 4-64 Four metallic frameworks obtained by means of 540. of gold and palladium alloy with a micromargin. Rg 4-65 After the opaque layer is brushed on. space remains for the entire margin to be covered by the esthetic ceramic material.

19

Figs 4-66 o 4-68 Metal-ceramic restorations with micromargins. The esthetic result is excellent. especially considering that these are porte­ lain-fused-to-metal crowns with a metal margin.

Figs 4-69 o 4-71 Detail of the gingival margin. evaluated through a stereomicroscope. Note the integration of the restorations and the soft tis­ sues. as well as the healthy gingival margin.

10

Figs 4-66 o 4-68 Metal-ceramic restorations with micromargins. The esthetic result is excellent. especially considering that these are porte­ lain-fused-to-metal crowns with a metal margin.

Figs 4-69 o 4-71 Detail of the gingival margin. evaluated through a stereomicroscope. Note the integration of the restorations and the soft tis­ sues. as well as the healthy gingival margin.

10

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

Fig 4-72 Conical abrasive burs. The conical kit (TO 860. conical version) has burs with the same diameters as in the cylindrical version. but a conicity of 3 degrees: therefore. The 0.14 mm point becomes 0.18 mm at the base of the stem. while the 0.18-mm bur becomes 0.23 mm at the base. The use of these burs must be limited to cases involving the restoration of multiple teeth and particularly those with advanced peri­ odontal disease. The conicity permits the clinician to establish the proper parallelism.

Figs 4-73 and 4-74 Conical diamond held vertically for a good angle of TOC. The clinician must maintain this slant during the operative stage: the wrong slant would create an undesired angle.

1

133

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

Fig 4-72 Conical abrasive burs. The conical kit (TO 860. conical version) has burs with the same diameters as in the cylindrical version. but a conicity of 3 degrees: therefore. The 0.14 mm point becomes 0.18 mm at the base of the stem. while the 0.18-mm bur becomes 0.23 mm at the base. The use of these burs must be limited to cases involving the restoration of multiple teeth and particularly those with advanced peri­ odontal disease. The conicity permits the clinician to establish the proper parallelism.

Figs 4-73 and 4-74 Conical diamond held vertically for a good angle of TOC. The clinician must maintain this slant during the operative stage: the wrong slant would create an undesired angle.

1

133

l

Fimsh Line Designs for Complete Crown Prepara

fig 4-75 Clinical case of a patient with advanced periodontal disease. The patient has already undergone periodontal surgery. and the teeth are b11ng prepared. Preservation � f the pulp vitality is a fundamental aspect of treatment. Fig 4-76 Development of the correct axis of the pre.parallon for tak1ng the 1mpres11on and f� r 1nsert1ng the prostheses. The original axis of the tooth 11 marked with a permanent marker to facilitate the reduction The 50-degree bur IS used to separate and create the guide groove. (See also figs 4-48 to 4-59 for more detail on the 1n�trumentat1on.l F1g 4-77 f1nal tooth pre � aralions. f1g 4-78 Occlusal view showing good alignment of the tooth preparations along the 1nsertton path. f1gs 4-79 and 4-80 Master cast 1llustrallng the paralleliSm obta1ned with the use of conical burs. The clinician should evaluate the pmllellsm mesiodistally and palatol1ngually Moreover. the ftn11h line shoulder will offer m1n1mal support area. depending on the length of the tooth preparation and the natural ap1cal narrow1ng of the tooth The chamfer will be quite small. even if 1t 1s made with a modified chamfer bur. and support a metal-ceramic restoration w1th a metallic margin 14

Fig 4-81 Master cast of a preparation for a molar executed with conical b u rs. fig 4-82 to 4-119 Schematic illustrations simulating tooth preparation with a modified chamfer finish line. fig 4-82 Facial view of a maxillary central incisor. The clinician separates the interproximal area using a 0.1 0-mm-diameter bur F19 4-83 Cross section of a sagittal view after separation. fig 4-84 Dental structure must be reduced to the purple line to place a metal- ceramic crown The th1ckness required for each sector is 1ndicated with a millimeter grid. Fig 4-85 Proportional relationship of a 50- degree. 0.16-mm. coarse-grtt bur with a tooth. Ftgs 4-86 to 4-88 Creat1on of guide grooves. With the bur held at about a 45-degree angle. the clin1cian creates a gu1de groove in the labiog1ng1val and palatoging1val margin areas. 135

l

Fimsh Line Designs for Complete Crown Prepara

fig 4-75 Clinical case of a patient with advanced periodontal disease. The patient has already undergone periodontal surgery. and the teeth are b11ng prepared. Preservation � f the pulp vitality is a fundamental aspect of treatment. Fig 4-76 Development of the correct axis of the pre.parallon for tak1ng the 1mpres11on and f� r 1nsert1ng the prostheses. The original axis of the tooth 11 marked with a permanent marker to facilitate the reduction The 50-degree bur IS used to separate and create the guide groove. (See also figs 4-48 to 4-59 for more detail on the 1n�trumentat1on.l F1g 4-77 f1nal tooth pre � aralions. f1g 4-78 Occlusal view showing good alignment of the tooth preparations along the 1nsertton path. f1gs 4-79 and 4-80 Master cast 1llustrallng the paralleliSm obta1ned with the use of conical burs. The clinician should evaluate the pmllellsm mesiodistally and palatol1ngually Moreover. the ftn11h line shoulder will offer m1n1mal support area. depending on the length of the tooth preparation and the natural ap1cal narrow1ng of the tooth The chamfer will be quite small. even if 1t 1s made with a modified chamfer bur. and support a metal-ceramic restoration w1th a metallic margin 14

Fig 4-81 Master cast of a preparation for a molar executed with conical b u rs. fig 4-82 to 4-119 Schematic illustrations simulating tooth preparation with a modified chamfer finish line. fig 4-82 Facial view of a maxillary central incisor. The clinician separates the interproximal area using a 0.1 0-mm-diameter bur F19 4-83 Cross section of a sagittal view after separation. fig 4-84 Dental structure must be reduced to the purple line to place a metal- ceramic crown The th1ckness required for each sector is 1ndicated with a millimeter grid. Fig 4-85 Proportional relationship of a 50- degree. 0.16-mm. coarse-grtt bur with a tooth. Ftgs 4-86 to 4-88 Creat1on of guide grooves. With the bur held at about a 45-degree angle. the clin1cian creates a gu1de groove in the labiog1ng1val and palatoging1val margin areas. 135

CH Pl Fimsh Line Designs for Complete Crown Preparations

Figs4-8g and 4-go Creation of reduction grooves. With the bur held vertically. the clinician places reduction grooves. measuring half the thick­ ness of the bur. Fig 4-g 1 Frontal view of reduction grooves. Figs 4- g2 and 4-gJ labial reduction. The clinician reduces the tooth. following the lines and extension defined by the reduction grooves.

Fig 4-4 Palatal reduction. The clinician carries out the same reduction on the palatal side. starting from the guide groove area and keeping the point in constant contact with the tooth surface. Fig 4- g5 and 4-g6 Modified chamfer bur with a 0.16 - mm diameter and coarse grit.

16

Fig 4- g7 Labial rounding. The clinician rounds the labial aspect in keeping with the anatomy and profile of the natural tooth. Fig 4- gs Palatal finish line. The clinician corrects the finish line on the palatal aspect.

Figs 4-Qg and 4-100 Using a 0.14-mm bur with coarse grit. the clinician connects the shoulder or buccal guide groove with the palatal guide groove. Fig4-101 1ncisal edge grooves. The clinician reduces the incisal edge by making two notches with the 0 . 1 6 - m m bur to the incisal finish line. Fig 4-102 Frontal view of incisal reduction grooves.

Fig 4-103 Incisal edge reduction. With the extent of reduction established by the grooves. the clinician reduces the entire incisal edge.

7

CH Pl Fimsh Line Designs for Complete Crown Preparations

Figs4-8g and 4-go Creation of reduction grooves. With the bur held vertically. the clinician places reduction grooves. measuring half the thick­ ness of the bur. Fig 4-g 1 Frontal view of reduction grooves. Figs 4- g2 and 4-gJ labial reduction. The clinician reduces the tooth. following the lines and extension defined by the reduction grooves.

Fig 4-4 Palatal reduction. The clinician carries out the same reduction on the palatal side. starting from the guide groove area and keeping the point in constant contact with the tooth surface. Fig 4- g5 and 4-g6 Modified chamfer bur with a 0.16 - mm diameter and coarse grit.

16

Fig 4- g7 Labial rounding. The clinician rounds the labial aspect in keeping with the anatomy and profile of the natural tooth. Fig 4- gs Palatal finish line. The clinician corrects the finish line on the palatal aspect.

Figs 4-Qg and 4-100 Using a 0.14-mm bur with coarse grit. the clinician connects the shoulder or buccal guide groove with the palatal guide groove. Fig4-101 1ncisal edge grooves. The clinician reduces the incisal edge by making two notches with the 0 . 1 6 - m m bur to the incisal finish line. Fig 4-102 Frontal view of incisal reduction grooves.

Fig 4-103 Incisal edge reduction. With the extent of reduction established by the grooves. the clinician reduces the entire incisal edge.

7

Fono1h Line Ouignl for Complete Crown Preparatoon•

1

fog 4 14 and 4 lOS CliniCian rtducu hall ol lht eonuvt surface ol lhe ptlalal aru 11 a hmt. u11ng a loolball·shapad bur fogl 4 16 •nd 4 107 F1n1sh1ng slaga Tht cllnomn uau font grot burs w11h the nmt thape and dlameler at In the reduct1on slage fog 4 108 Plaumanl of lht rtlrtcllon cord Tht aua ol lht cord and the uu and type of lmpregnahng toluhon It choun baud on the pero· odonlal blolypt and lha 1mpreulon malerlll uud fog 4 100 Rtpotlllonlng of lht l1nlsh lint Aflor lht huue is rtlrlcltd. lht el1n1cian uus a bur wllh the ume doamtlor and domension as the ont und prnloualy to rtpo1111on lht 11nlsh lint fog 4 110 Conhnull•on of rtp011l10n1ng Tha cllnomn utabllshu lht ntw gongoval morgon. using 0 1 !-mm oscollallng ullrason1c or tonic lnstrumanlt

Il

fogs 4-111 1o 4 113 Repositioning In the onterproxomal area The elonomn repos1toons the finiSh line on the onlorproximal area. using 0 1 4 - m m nonrolatlng s o n i c or ultrasonic instruments F1gs 4-114 10 4-116 Relining of the shoulder finish lone with a manual rounded ch111l F1g 4-117 Finished preparation li the cllnlelan notices a mln1mal homonlal space between the glng1va and the shoulder lln11h line. or a small area ol lhe tooth not prepared thai is not covered by the retraction cord. the Impression can be made. leaving the llrsl cord 1 n place F1g 4-118 II part of the g1nglval margin 1mpedes the acceu of the 1mpreuoon matenal. a second retraction cord 11 Inserted for homonlol retracilon and 11 removed Immediately before lak1ng the impreu1on F1g 4 119 Once a sullable 1mpren1on has been taken. the ciln1clan removu lht retraction cord The g1ng1va w11t return to lht natural level

Fono1h Line Ouignl for Complete Crown Preparatoon•

1

fog 4 14 and 4 lOS CliniCian rtducu hall ol lht eonuvt surface ol lhe ptlalal aru 11 a hmt. u11ng a loolball·shapad bur fogl 4 16 •nd 4 107 F1n1sh1ng slaga Tht cllnomn uau font grot burs w11h the nmt thape and dlameler at In the reduct1on slage fog 4 108 Plaumanl of lht rtlrtcllon cord Tht aua ol lht cord and the uu and type of lmpregnahng toluhon It choun baud on the pero· odonlal blolypt and lha 1mpreulon malerlll uud fog 4 100 Rtpotlllonlng of lht l1nlsh lint Aflor lht huue is rtlrlcltd. lht el1n1cian uus a bur wllh the ume doamtlor and domension as the ont und prnloualy to rtpo1111on lht 11nlsh lint fog 4 110 Conhnull•on of rtp011l10n1ng Tha cllnomn utabllshu lht ntw gongoval morgon. using 0 1 !-mm oscollallng ullrason1c or tonic lnstrumanlt

Il

fogs 4-111 1o 4 113 Repositioning In the onterproxomal area The elonomn repos1toons the finiSh line on the onlorproximal area. using 0 1 4 - m m nonrolatlng s o n i c or ultrasonic instruments F1gs 4-114 10 4-116 Relining of the shoulder finish lone with a manual rounded ch111l F1g 4-117 Finished preparation li the cllnlelan notices a mln1mal homonlal space between the glng1va and the shoulder lln11h line. or a small area ol lhe tooth not prepared thai is not covered by the retraction cord. the Impression can be made. leaving the llrsl cord 1 n place F1g 4-118 II part of the g1nglval margin 1mpedes the acceu of the 1mpreuoon matenal. a second retraction cord 11 Inserted for homonlol retracilon and 11 removed Immediately before lak1ng the impreu1on F1g 4 119 Once a sullable 1mpren1on has been taken. the ciln1clan removu lht retraction cord The g1ng1va w11t return to lht natural level

J

Finish Line Designs for Complete Crown Preparalion

Fig 4-120 Clinical case of a patient who exhiblh severe bruxism. The initial clinical situation shows severe abrasions in the maxillary and mandibular anterior Ieeth. as well as numerous necrotic Ieeth resulting from the progressive wear of the tooth surfaces. F1g4-121 To reestab­ lish normal occlusion and incre �se vertical height after orlhognalhic treatment with bile raising. the clinician lengthened the clinical crown . and roconloured the bone and g1ng1val marg1ns. Fig 4-122 Changed anatomy and crown exposure after healing period. Fig 4-123 Tooth prepa­ ration using cylindrical diamond bur kit. The clinician waited 6 months after the surgery for the tissues to heal. The teeth were separated using a 0.16-mm cylindrical bur with a modified chamfer. ThiS bur can also be used to make the guide grooves. Figs 4-124 and 4-125 Creation of a gu1de groon. The guide groove extends to the g1ngiva. By keeping the groove above the sulcus the clinician maintains the gingival ref­ erence point F1g 4-126 Amount of reduction Is verified using the diameter of the bur.

10

Fig 4-127 Reduction grooves. Fig 4-128 I ncisal reduction. The clinician reduced the incisal edge minimally because it was necessary to increase the vertical height considerably. Fig 4-129 Once the labial portion of the tooth has been prepared. the clinician connects the labial and palatal surfaces through the interproximal area. Figs 4-130 and 4-131 Reducing half of the tooth at a time. This technique is ideal for cir­ cumstances that preclude the use of simple grooves. lor surfaces thai are not flat. and lor use with curved burs. With half the canine pre­ pared. the clinician may compare it with the intact half and evaluate the extent of the reduction. Fig 4-132 Completed tooth reduction. I n a patient who exhibits bruxi sm. tooth preparation is principally aimed at providing resistance and function rather than esthetics. Figs 4-133 and 4-136 Repositioning the gingival margins. The clinician inserts the retraction cord and finishes Ieeth with rotating fine-grit burs.

141

J

Finish Line Designs for Complete Crown Preparalion

Fig 4-120 Clinical case of a patient who exhiblh severe bruxism. The initial clinical situation shows severe abrasions in the maxillary and mandibular anterior Ieeth. as well as numerous necrotic Ieeth resulting from the progressive wear of the tooth surfaces. F1g4-121 To reestab­ lish normal occlusion and incre �se vertical height after orlhognalhic treatment with bile raising. the clinician lengthened the clinical crown . and roconloured the bone and g1ng1val marg1ns. Fig 4-122 Changed anatomy and crown exposure after healing period. Fig 4-123 Tooth prepa­ ration using cylindrical diamond bur kit. The clinician waited 6 months after the surgery for the tissues to heal. The teeth were separated using a 0.16-mm cylindrical bur with a modified chamfer. ThiS bur can also be used to make the guide grooves. Figs 4-124 and 4-125 Creation of a gu1de groon. The guide groove extends to the g1ngiva. By keeping the groove above the sulcus the clinician maintains the gingival ref­ erence point F1g 4-126 Amount of reduction Is verified using the diameter of the bur.

10

Fig 4-127 Reduction grooves. Fig 4-128 I ncisal reduction. The clinician reduced the incisal edge minimally because it was necessary to increase the vertical height considerably. Fig 4-129 Once the labial portion of the tooth has been prepared. the clinician connects the labial and palatal surfaces through the interproximal area. Figs 4-130 and 4-131 Reducing half of the tooth at a time. This technique is ideal for cir­ cumstances that preclude the use of simple grooves. lor surfaces thai are not flat. and lor use with curved burs. With half the canine pre­ pared. the clinician may compare it with the intact half and evaluate the extent of the reduction. Fig 4-132 Completed tooth reduction. I n a patient who exhibits bruxi sm. tooth preparation is principally aimed at providing resistance and function rather than esthetics. Figs 4-133 and 4-136 Repositioning the gingival margins. The clinician inserts the retraction cord and finishes Ieeth with rotating fine-grit burs.

141

Fimsh Line Des1gns for Complete Crown Preparations

j

4- 1 3 8

4- 1 4 5

Fig 4- 135 CliniCal v1ew before repositioning the finish line with nonrolating instruments. Fig 4-136 Finish with ultrasonic tip. Because ultra­ SOniC technology IS not based on rotation, it does not damage the periodontal tissue. Fig 4-137 Anterior teeth alter the first stage of prepara­ tion f1gs 4-138 and 4- 13g Second-stage promional prostheses on the working cast, alter adaptation and positioning in the patient's mouth. _ not accentuated, but th teeth have been elongated according The anlenor gu1de IS to the clinician's instructions. Fig 4-140 Mock-up of � mandibular p �ostheus The mandibular antenor tnth also needed to be lengthened. and ceramic veneers were planned from canine to can1ne Mandibular prostheses were mocked up according to the pretreatment indications.

142

4- 1 4 6

Fig 4-141 Try-in of mock-up. Fig 4-142 Once adapted, the mock-up became the provisional restoration. permitting normal speech and main­ taining a normal lip line. Fig 4-143 Posterior mandi bular provisional restorations. Once the posterior height was b e determined. the clinician could proceed to adapt the anterior provisional restorations according to the indications. Fig 4-14 Anterior mandibular provision! restora­ tions adapted to the height of the posterior restorations. Aller the clinician spot etched the center of the teeth with 37% phosphoric acid for 20 seconds, a film of resin bonding solution was applied both on the surface of the prepared tooth and inside the provisional. and then poly­ merized with light. Provisional porcelain laminate veneers are never composed of single veneers. When a significant amount of dentin is exposed. it is preferable to use a transparent cement (TempBond Clear. Kerr) instead of the bonding solution. Fig 4-145 Finish line analysis on the master cast. The goat lor the laminate veneer preparation is to save as much tissue as possible. Fig 4-146 Feldspathic porcelain laminate veneers on the cast.

13

Fimsh Line Des1gns for Complete Crown Preparations

j

4- 1 3 8

4- 1 4 5

Fig 4- 135 CliniCal v1ew before repositioning the finish line with nonrolating instruments. Fig 4-136 Finish with ultrasonic tip. Because ultra­ SOniC technology IS not based on rotation, it does not damage the periodontal tissue. Fig 4-137 Anterior teeth alter the first stage of prepara­ tion f1gs 4-138 and 4- 13g Second-stage promional prostheses on the working cast, alter adaptation and positioning in the patient's mouth. _ not accentuated, but th teeth have been elongated according The anlenor gu1de IS to the clinician's instructions. Fig 4-140 Mock-up of � mandibular p �ostheus The mandibular antenor tnth also needed to be lengthened. and ceramic veneers were planned from canine to can1ne Mandibular prostheses were mocked up according to the pretreatment indications.

142

4- 1 4 6

Fig 4-141 Try-in of mock-up. Fig 4-142 Once adapted, the mock-up became the provisional restoration. permitting normal speech and main­ taining a normal lip line. Fig 4-143 Posterior mandi bular provisional restorations. Once the posterior height was b e determined. the clinician could proceed to adapt the anterior provisional restorations according to the indications. Fig 4-14 Anterior mandibular provision! restora­ tions adapted to the height of the posterior restorations. Aller the clinician spot etched the center of the teeth with 37% phosphoric acid for 20 seconds, a film of resin bonding solution was applied both on the surface of the prepared tooth and inside the provisional. and then poly­ merized with light. Provisional porcelain laminate veneers are never composed of single veneers. When a significant amount of dentin is exposed. it is preferable to use a transparent cement (TempBond Clear. Kerr) instead of the bonding solution. Fig 4-145 Finish line analysis on the master cast. The goat lor the laminate veneer preparation is to save as much tissue as possible. Fig 4-146 Feldspathic porcelain laminate veneers on the cast.

13

Fimsh --.

Line Designs for Complete Crown Preparations

I

FiQI 4-147 and 4-148 The area is isolated with rubber dam. and the tooth is etched prior to cementation of the veneer. FiQ 4-149 Natural die preparations immediately prior to cementation.

FIQ 4-150 Where possible, the clinician preserved pulp vitality. a prime objective in every treatment.

FIQ 4-151 Occlusal view of the mandibular arch after cementation of the laminate veneers and metal-ceram1c crowns.

Figs 4-154 and 4-155 Clinical situation before and after comp. lete restoration. with increased vertical height. complete crowns. and porcelain laminate veneers. The clinician decided to restore the mandibular anter�or teeth w1th veneers mstead of With complete crowns because of the resistance of adhesion. even with parafunctional activity. and the difficulty of preparing the mandibular incisors for metal-ceramic crowns.

Figs 4-156 and 4-157 Mandibular anterior teeth before and after restoration with porcelain laminate veneers. Note the increased vertical height.

F1QI 4-152 and 4-153 Maxillary anterior restorations after cementation

14

15

Fimsh --.

Line Designs for Complete Crown Preparations

I

FiQI 4-147 and 4-148 The area is isolated with rubber dam. and the tooth is etched prior to cementation of the veneer. FiQ 4-149 Natural die preparations immediately prior to cementation.

FIQ 4-150 Where possible, the clinician preserved pulp vitality. a prime objective in every treatment.

FIQ 4-151 Occlusal view of the mandibular arch after cementation of the laminate veneers and metal-ceram1c crowns.

Figs 4-154 and 4-155 Clinical situation before and after comp. lete restoration. with increased vertical height. complete crowns. and porcelain laminate veneers. The clinician decided to restore the mandibular anter�or teeth w1th veneers mstead of With complete crowns because of the resistance of adhesion. even with parafunctional activity. and the difficulty of preparing the mandibular incisors for metal-ceramic crowns.

Figs 4-156 and 4-157 Mandibular anterior teeth before and after restoration with porcelain laminate veneers. Note the increased vertical height.

F1QI 4-152 and 4-153 Maxillary anterior restorations after cementation

14

15

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

. AD DITIONAL G U I D ELI N ES FOR TOOTH PREPARAT I O N

With regard to axial reduction, clinicians general· ly believe it should make possible both the devel­ opment or normal periodontal borders and ade­

Clinicians have always debated t h e relative merits o r

quate resistance and esthetics. For metal restor­

different finish lines a n d their application t o a variety

ations, a reduction or 0.5 to o.8 mm in the buccal

of clinical situations. One of the criteria for deter·

and lingual surfaces appears to be suficient, while

mining the choice or a specific finish line design is

for both metal-ceramic and all-ceramic crowns, depths

the type or restorative material used, ie, metal,

or 1.0 to 1.5 mm•' are recommended. Occlusal re­

metal-ceramic, or all-ceramic.

duction ranges from 2.0 to 2.5 mm, according to the

Long chamfer finish lines are usually used with

thickness or the posterior teeth and the patient's

cast metal crowns; in this kind or restoration, the

age. For all-ceramic restorations, occlusal reductions

reduction depth must be in the range or 0.3 to 0.5

should be about 2.0 mm to develop proper mor­

mm, 29 permitting a minimum overall reduction or

phology without endangering the health or the

the tooth.

pulpal tissue.

For metal-ceramic crowns, clinicians have typi·

The recommended values should not be consid­

cally used either chamfer, beveled chamfer, shout·

ered absolute; they are merely indications for guid­

der, or beveled shoulder finish lines. A number of

ing the clinician in tooth reduction to create suitable

authorsJ>-JJ found no significant diferences in the

space for the restorative materials. The skill and

marginal adaptation or metal-ceramic restorations

ability or the dental technician, the condition or the

with any or these inish lines. Some studiesJ• show

teeth, and the expectations or the patient all influ­

that choosing which finish line to use with metal­

ence tooth preparation. The silicone guides on the

ceramic crowns should not be based on marginal

diagnostic waxup or the final restoration. when sec·

adaptation but rather on esthetic preferences, ease

tioned, can be useful to provide the clinician with a

or execution, and type or margin Oe. metal, micro­

clear view or the amount or available space.

margin, or ceramic).3'

The authors' opinion is that the preparation

The recommended thickness or the finish lines is

phase is the prologue to obtaining excellence in

1.0 to 1.5 mm, the minimum required for resistance

every restorative phase, but many clinicians lack the

and esthetics and the minimum space required for

guidelines for performing these steps Oe. separa­

achieving an ideal emergence profile.'l-35 Clinical

tion, reduction, and finishing).

studies, however, show that these values are rarely achieved in clinical practice.J6. J7

4-168) is a workable system that allows greater ease

The modified chamfer preparation (Figs 4-158 to

For all-ceramic crowns, studies have shown either

in obtaining excellent results at diferent stages and

that the chamfer finish line was far less resistant

with varying levels or concentration. It offers an inno­

than the 90-degree shoulder,38- 39 or that no signifi­

vative design that permits all types or restorations

cant diference was round after adhesive cementa·

(metal, micromargin, and all-ceramic) and every kind

tion.•0 Nevertheless, there is a general concensus

or connection-in the complete arch, with many

that the optimal recommended depth for successful

connected teeth, and or course, in the case or a sin-

all-ceramic crowns is 1 mm.41

gle-unit esthetic crown with feldspathic ceramics.

Figs 4-158 to 4-168 Clinical case illustrating the esthetics obtained with the modified chamfer technique.

Fig4-158 Preoperative view of a 27-year-old female patient with two metal-ceramic crowns on the maxillary left central a n d lateral incisors. The restorations had been placed 1 year earlier. after a traumatic event. Clinical examination revealed, inadequate esthetic result of the two crowns. resin composite restorations on the right central and lateral incisors. and that the teeth were excessively short for a person her age and in relation to the opposing dentition. Fig 4-15g Removal of the fixed dental prostheses revealed discolored and inadequate tooth preparations.

•

Figs 4-160 After the diagnostic waxup was prepared. the clinician replaced the composite restorations and prepared for two veneers.

Fig 4-161 The nonvital teeth were whitened and reconstructed using fiberglass dowels. The finish line for the all-ceramic restorations was prepared using the modified chamfer technique. Care was taken to leave an adequate support for the planned restoration. Figs 4-162 and 4-163 Occlusal view of clinical situation. before and after treatment.

lU

147

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

. AD DITIONAL G U I D ELI N ES FOR TOOTH PREPARAT I O N

With regard to axial reduction, clinicians general· ly believe it should make possible both the devel­ opment or normal periodontal borders and ade­

Clinicians have always debated t h e relative merits o r

quate resistance and esthetics. For metal restor­

different finish lines a n d their application t o a variety

ations, a reduction or 0.5 to o.8 mm in the buccal

of clinical situations. One of the criteria for deter·

and lingual surfaces appears to be suficient, while

mining the choice or a specific finish line design is

for both metal-ceramic and all-ceramic crowns, depths

the type or restorative material used, ie, metal,

or 1.0 to 1.5 mm•' are recommended. Occlusal re­

metal-ceramic, or all-ceramic.

duction ranges from 2.0 to 2.5 mm, according to the

Long chamfer finish lines are usually used with

thickness or the posterior teeth and the patient's

cast metal crowns; in this kind or restoration, the

age. For all-ceramic restorations, occlusal reductions

reduction depth must be in the range or 0.3 to 0.5

should be about 2.0 mm to develop proper mor­

mm, 29 permitting a minimum overall reduction or

phology without endangering the health or the

the tooth.

pulpal tissue.

For metal-ceramic crowns, clinicians have typi·

The recommended values should not be consid­

cally used either chamfer, beveled chamfer, shout·

ered absolute; they are merely indications for guid­

der, or beveled shoulder finish lines. A number of

ing the clinician in tooth reduction to create suitable

authorsJ>-JJ found no significant diferences in the

space for the restorative materials. The skill and

marginal adaptation or metal-ceramic restorations

ability or the dental technician, the condition or the

with any or these inish lines. Some studiesJ• show

teeth, and the expectations or the patient all influ­

that choosing which finish line to use with metal­

ence tooth preparation. The silicone guides on the

ceramic crowns should not be based on marginal

diagnostic waxup or the final restoration. when sec·

adaptation but rather on esthetic preferences, ease

tioned, can be useful to provide the clinician with a

or execution, and type or margin Oe. metal, micro­

clear view or the amount or available space.

margin, or ceramic).3'

The authors' opinion is that the preparation

The recommended thickness or the finish lines is

phase is the prologue to obtaining excellence in

1.0 to 1.5 mm, the minimum required for resistance

every restorative phase, but many clinicians lack the

and esthetics and the minimum space required for

guidelines for performing these steps Oe. separa­

achieving an ideal emergence profile.'l-35 Clinical

tion, reduction, and finishing).

studies, however, show that these values are rarely achieved in clinical practice.J6. J7

4-168) is a workable system that allows greater ease

The modified chamfer preparation (Figs 4-158 to

For all-ceramic crowns, studies have shown either

in obtaining excellent results at diferent stages and

that the chamfer finish line was far less resistant

with varying levels or concentration. It offers an inno­

than the 90-degree shoulder,38- 39 or that no signifi­

vative design that permits all types or restorations

cant diference was round after adhesive cementa·

(metal, micromargin, and all-ceramic) and every kind

tion.•0 Nevertheless, there is a general concensus

or connection-in the complete arch, with many

that the optimal recommended depth for successful

connected teeth, and or course, in the case or a sin-

all-ceramic crowns is 1 mm.41

gle-unit esthetic crown with feldspathic ceramics.

Figs 4-158 to 4-168 Clinical case illustrating the esthetics obtained with the modified chamfer technique.

Fig4-158 Preoperative view of a 27-year-old female patient with two metal-ceramic crowns on the maxillary left central a n d lateral incisors. The restorations had been placed 1 year earlier. after a traumatic event. Clinical examination revealed, inadequate esthetic result of the two crowns. resin composite restorations on the right central and lateral incisors. and that the teeth were excessively short for a person her age and in relation to the opposing dentition. Fig 4-15g Removal of the fixed dental prostheses revealed discolored and inadequate tooth preparations.

•

Figs 4-160 After the diagnostic waxup was prepared. the clinician replaced the composite restorations and prepared for two veneers.

Fig 4-161 The nonvital teeth were whitened and reconstructed using fiberglass dowels. The finish line for the all-ceramic restorations was prepared using the modified chamfer technique. Care was taken to leave an adequate support for the planned restoration. Figs 4-162 and 4-163 Occlusal view of clinical situation. before and after treatment.

lU

147

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

Figs 4-14 and 4-165 Close-up views 1 month after cementation. showing excellent esthetic integration. The clinician had placed ceramic restorations on the maxillary left central and lateral incisors and porcelain laminate veneers on the maxillary right central and lateral incisors.

11

Fig 4-166 Patient's smile before treatment. figs 4-167 to 4-168 Patient's smile after treatment. showing improved esthetics in terms of the shape and luminosity of the teeth. as welt as an excellent lip line.

149

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

Figs 4-14 and 4-165 Close-up views 1 month after cementation. showing excellent esthetic integration. The clinician had placed ceramic restorations on the maxillary left central and lateral incisors and porcelain laminate veneers on the maxillary right central and lateral incisors.

11

Fig 4-166 Patient's smile before treatment. figs 4-167 to 4-168 Patient's smile after treatment. showing improved esthetics in terms of the shape and luminosity of the teeth. as welt as an excellent lip line.

149

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

12.

REFERENCES

Kashani HG, Khera SC. Gulker lA. The efects of bevel angulation on marginal integrity.

1.

Castellani 0. La Preparazione dei pilastri per corone in metal-ceramica. Bologna: artina, 1994:207-208.

2.

103:882-885. 13.

and occlusal seat of full crown preparations. Dent 1981;45: 138-145· 14.

Kuwata M. Atlante a colon sulla tecnologia

6.

17.

Panno V. Vahidi F, Gulker I, Ghalili KM. Evaluation or

Ramp MH. McCracken MS. Mazar RB. Tooth structure

28.

1 Prosthet Dent 1986:56:655�61.

Mitchell A. Pintado MR, Douglas WH. Nondestructive,

and Bridge Procedures. Amsterdam: Dental Center for

29.

I

JO.

breaking strength of Dicor crowns. lnt J Prosthodont

Hamaguchi H, Cacciatore A, Tueller VM. Marginal distor·

1993;6:28&-290.

Postgraduate Courses. 1985.

tion of the porcelain-bonded-to-metal complete crown: An SEM study. I Prosthet Dent 1982;47:14&-153·

retention of cemented gold castings. J Prosthet Dent 1961;11:487-502.

Change in marginal it as related to margin design. alloy

Martignoni M, Shonenberger AJ. Precision Fixed Pros·

type, and porcelain proximity in porcelain-fused-to·

thodontics: Clinical and Laboratory Aspects. Chicago:

metal restorations.

31.

32.

I

Belser UC, MacEntee Ml, Richter WA. Fit of three

El Ebrashi MK, Craig RG, Peyton FA. Experimental stress

sign in porcelain-fused-to-metal restorations. J Prosthet

electron microscope study.

analysis of dental restorations. Part Ill. The concept of

Dent 1980;43=149-155·

24-29.

Rosner D. Fundion placement and reproduction of bevels for gold castings. I Prosthet Dent 1963;13:116o.

33·

I

Prosthet Dent 1985;53:

Douglas RD. P/bylska M. Predicting porcelain thick· ness required for dental shade matches. I Prosthet Dent 1999;82:143-149·

41.

Stambaugh RV, Wittrock JW. The relationship of the pulp chamber to the extenal surface of the tooth. Dent 1977;37:537-546.

Prosthet Dent 1988;6o:435-439.

porcelain-fused-to-metal designs in vivo: A scanning

tions for collarless metal-ceramic crowns: Hand-planning

40.

Richter·Snapp K. Aquilino SA, Svare CW, Turner KA.

Faucher RR. Nicholls 11. Distortion related to margin de·

22. Zena RB, Khan Z, von Fraunhofer JA. Shoulder prepara·

Bernal G, Jones RM, Brown DT, Munoz A, Goodacre CJ. The efect of inish line m and luting agent on the

Prosthodontics. ed 2. St Louis: Mosby, 1995:137-138,

tients [in German). Parodontol 1990;1:153-164.

geometry of proximal margins. 1 Prosthet Dent 196g;

39·

17o-173. 184-185, 229.

Kauman EG, Coelho DH, Colin L. Factors inluencing

Quintessence, 1990.

thodont 1990:3:241-248.

Prosthet Dent 1999;82:398-409.

Rosenstiel S. Land MF, Fujimoto J. Contemporary Rxed

duced periodontal support in partially edentulous pa·

21.

Doyle MG, Munoz . Goodacre CJ. Friedlander LD, Moore BK. The efect of tooth preparation design on the

2001;85 : 5 75-584.

20.

38.

breaking strength of Dicor crowns: Part 2. tnt J Pros·

in vitro quantification of crown margins. I Prosthet Dent

19.

thodont 1990;3=159-168.

Moschen I, Berger P. Falk M, Horl R. Horle M, Gausch K.

lelism with the use of four tooth preparation methods.

advanced periodontal disease. J Periodontal 1979;50:

22:333-345·

Friedlander LD, Munoz A. Goodacre CJ, Doyle MG,

Comparison of resin-bonded prosthesis groove paral­

18. Pameijer JHN. Periodontal and Occlusal Fadors in Crown

Siegel SC, Driscoll CF, Feldman S. Tooth stabilization

37.

the 45·degree labial bevel with a shoulder preparation.

periodontal and prosthetic treatment of patients with

45-76.

IO

1996;75 =40--411.

45-46. 27.

Seymour K, Zou L, Samarawickrama D. Lynch E. Assess·

1993:6:25-30. 16.

ixed partial dentures. Dent Clin North Am 1999:43:

11.

bonded to metal crown preparations. J Prosthet Dent

Mclean JW. Wilson AD. Butt joint versus beveled gold

36.

breaking strength of Dicor crowns: Part t. lnt J Pros·

and splinting before and ater periodontal therapy with

10.

ment of shoulder dimensions and angles of porcelain

and Techniques. Santa Rosa. A: Alto Books, 1990:

Restaurazione Protesica. Verona: Resch, 1993.

79=491-494·

163-169.

9·

Albers H. Impressions: A Text for Selection of Materials

when using self·limiting burs. I Prosthet Dent 1998;

7· Nyman S. lindhe J. A longitudinal study of combined

De Soever lA. Fixed restorations of a dentition with re·

26.

line geometry on the it of crowns. lnt J Prosthodont

Periodontics Restorative Dent 1985;5:52�2.

8.

Chiche GJ. Pinault A. Esthetics of Anterior Fixed Prostho· dontics. Chicago: Quintessence. 1994:86-91, 102-103.

Moore BK. The efect or tooth preparation design on the

Di Febo G. Canevale G, Sterrantino S. Treatment of a case of advanced periodontitis: Clinical procedures uti­ .. lizing the .combined preparation technique. tnt J

35·

loss apical to preparations for fixed partial dentures

delle

ricostruzioni ceramo-metalliche. Utet t989;2:2 JS-2SO.

principles. I Prosthet Dent 2001;85:363-376.

15. Syu JZ. Byrne G. Laub LW. Land MF. Influence of finish·

lnt 2001;32:603�10. 5.

tions for complete crowns: An art based on scientific

Menghini P, Battaini P. Metallurgia in odontoiatria. Milan:

Massironi D. Battistelli A, Pascetta R. La Precisione Nella

Prosthet

1980:14:239-250.

34· Goodacre CJ, Campagni W, Aquilino SA. Tooth prepara·

25.

margin in metal-ceramic crowns. J Biomed Mater Res

Peon BK, Smales RJ. Assessment of clinical preparations for single gold and ceramometal crowns. Quintessence

I

Massironi D. Battistelli A. Sistema di preparazione per corone complete. Masson Protech 2000;J:JS-47·

Masson. 1997:38-39.

Gavelis JW. Morency JD. Riley ED. Sozio RB. The efect

sign: A dental school survey. I Prosthet Dent 1991;65:

fessionale odontoiatrica. Milan: Masson. 1990:408-4D9. 4-

24.

of various inish line preparations on the marginal seal

Guastamacchia C. Elementi di ergonomia e pratica pro­

23.

Dent Assoc 1981;

Butel EM. Campbell JC. DiFiore PM. Crown margin de·

303-305. 3-

I Am

42.

I

Prosthet

AI·Omari WM. AI·Wahadni AM. Convegence angle, occlu· sal reduction. and finish line depth of full·crown prepa· rations made by dental students. Quintessence tnt 2004; 3 5 :287-293·

Byrne G. Influence of finish-line form on crown cemen· tation. lnt I Prosthodont 1992;5:137-144.

as opposed to rotary instrumentation. J Prosthet Dent 1989;62:273-277.

151

CHAPTER 4 Finish Line Designs for Complete Crown Preparations

12.

REFERENCES

Kashani HG, Khera SC. Gulker lA. The efects of bevel angulation on marginal integrity.

1.

Castellani 0. La Preparazione dei pilastri per corone in metal-ceramica. Bologna: artina, 1994:207-208.

2.

103:882-885. 13.

and occlusal seat of full crown preparations. Dent 1981;45: 138-145· 14.

Kuwata M. Atlante a colon sulla tecnologia

6.

17.

Panno V. Vahidi F, Gulker I, Ghalili KM. Evaluation or

Ramp MH. McCracken MS. Mazar RB. Tooth structure

28.

1 Prosthet Dent 1986:56:655�61.

Mitchell A. Pintado MR, Douglas WH. Nondestructive,

and Bridge Procedures. Amsterdam: Dental Center for

29.

I

JO.

breaking strength of Dicor crowns. lnt J Prosthodont

Hamaguchi H, Cacciatore A, Tueller VM. Marginal distor·

1993;6:28&-290.

Postgraduate Courses. 1985.

tion of the porcelain-bonded-to-metal complete crown: An SEM study. I Prosthet Dent 1982;47:14&-153·

retention of cemented gold castings. J Prosthet Dent 1961;11:487-502.

Change in marginal it as related to margin design. alloy

Martignoni M, Shonenberger AJ. Precision Fixed Pros·

type, and porcelain proximity in porcelain-fused-to·

thodontics: Clinical and Laboratory Aspects. Chicago:

metal restorations.

31.

32.

I

Belser UC, MacEntee Ml, Richter WA. Fit of three

El Ebrashi MK, Craig RG, Peyton FA. Experimental stress

sign in porcelain-fused-to-metal restorations. J Prosthet

electron microscope study.

analysis of dental restorations. Part Ill. The concept of

Dent 1980;43=149-155·

24-29.

Rosner D. Fundion placement and reproduction of bevels for gold castings. I Prosthet Dent 1963;13:116o.

33·

I

Prosthet Dent 1985;53:

Douglas RD. P/bylska M. Predicting porcelain thick· ness required for dental shade matches. I Prosthet Dent 1999;82:143-149·

41.

Stambaugh RV, Wittrock JW. The relationship of the pulp chamber to the extenal surface of the tooth. Dent 1977;37:537-546.

Prosthet Dent 1988;6o:435-439.

porcelain-fused-to-metal designs in vivo: A scanning

tions for collarless metal-ceramic crowns: Hand-planning

40.

Richter·Snapp K. Aquilino SA, Svare CW, Turner KA.

Faucher RR. Nicholls 11. Distortion related to margin de·

22. Zena RB, Khan Z, von Fraunhofer JA. Shoulder prepara·

Bernal G, Jones RM, Brown DT, Munoz A, Goodacre CJ. The efect of inish line m and luting agent on the

Prosthodontics. ed 2. St Louis: Mosby, 1995:137-138,

tients [in German). Parodontol 1990;1:153-164.

geometry of proximal margins. 1 Prosthet Dent 196g;

39·

17o-173. 184-185, 229.

Kauman EG, Coelho DH, Colin L. Factors inluencing

Quintessence, 1990.

thodont 1990:3:241-248.

Prosthet Dent 1999;82:398-409.

Rosenstiel S. Land MF, Fujimoto J. Contemporary Rxed

duced periodontal support in partially edentulous pa·

21.

Doyle MG, Munoz . Goodacre CJ. Friedlander LD, Moore BK. The efect of tooth preparation design on the

2001;85 : 5 75-584.

20.

38.

breaking strength of Dicor crowns: Part 2. tnt J Pros·

in vitro quantification of crown margins. I Prosthet Dent

19.

thodont 1990;3=159-168.

Moschen I, Berger P. Falk M, Horl R. Horle M, Gausch K.

lelism with the use of four tooth preparation methods.

advanced periodontal disease. J Periodontal 1979;50:

22:333-345·

Friedlander LD, Munoz A. Goodacre CJ, Doyle MG,

Comparison of resin-bonded prosthesis groove paral­

18. Pameijer JHN. Periodontal and Occlusal Fadors in Crown

Siegel SC, Driscoll CF, Feldman S. Tooth stabilization

37.

the 45·degree labial bevel with a shoulder preparation.

periodontal and prosthetic treatment of patients with

45-76.

IO

1996;75 =40--411.

45-46. 27.

Seymour K, Zou L, Samarawickrama D. Lynch E. Assess·

1993:6:25-30. 16.

ixed partial dentures. Dent Clin North Am 1999:43:

11.

bonded to metal crown preparations. J Prosthet Dent

Mclean JW. Wilson AD. Butt joint versus beveled gold

36.

breaking strength of Dicor crowns: Part t. lnt J Pros·

and splinting before and ater periodontal therapy with

10.

ment of shoulder dimensions and angles of porcelain

and Techniques. Santa Rosa. A: Alto Books, 1990:

Restaurazione Protesica. Verona: Resch, 1993.

79=491-494·

163-169.

9·

Albers H. Impressions: A Text for Selection of Materials

when using self·limiting burs. I Prosthet Dent 1998;

7· Nyman S. lindhe J. A longitudinal study of combined

De Soever lA. Fixed restorations of a dentition with re·

26.

line geometry on the it of crowns. lnt J Prosthodont

Periodontics Restorative Dent 1985;5:52�2.

8.

Chiche GJ. Pinault A. Esthetics of Anterior Fixed Prostho· dontics. Chicago: Quintessence. 1994:86-91, 102-103.

Moore BK. The efect or tooth preparation design on the

Di Febo G. Canevale G, Sterrantino S. Treatment of a case of advanced periodontitis: Clinical procedures uti­ .. lizing the .combined preparation technique. tnt J

35·

loss apical to preparations for fixed partial dentures

delle

ricostruzioni ceramo-metalliche. Utet t989;2:2 JS-2SO.

principles. I Prosthet Dent 2001;85:363-376.

15. Syu JZ. Byrne G. Laub LW. Land MF. Influence of finish·

lnt 2001;32:603�10. 5.

tions for complete crowns: An art based on scientific

Menghini P, Battaini P. Metallurgia in odontoiatria. Milan:

Massironi D. Battistelli A, Pascetta R. La Precisione Nella

Prosthet

1980:14:239-250.

34· Goodacre CJ, Campagni W, Aquilino SA. Tooth prepara·

25.

margin in metal-ceramic crowns. J Biomed Mater Res

Peon BK, Smales RJ. Assessment of clinical preparations for single gold and ceramometal crowns. Quintessence

I

Massironi D. Battistelli A. Sistema di preparazione per corone complete. Masson Protech 2000;J:JS-47·

Masson. 1997:38-39.

Gavelis JW. Morency JD. Riley ED. Sozio RB. The efect

sign: A dental school survey. I Prosthet Dent 1991;65:

fessionale odontoiatrica. Milan: Masson. 1990:408-4D9. 4-

24.

of various inish line preparations on the marginal seal

Guastamacchia C. Elementi di ergonomia e pratica pro­

23.

Dent Assoc 1981;

Butel EM. Campbell JC. DiFiore PM. Crown margin de·

303-305. 3-

I Am

42.

I

Prosthet

AI·Omari WM. AI·Wahadni AM. Convegence angle, occlu· sal reduction. and finish line depth of full·crown prepa· rations made by dental students. Quintessence tnt 2004; 3 5 :287-293·

Byrne G. Influence of finish-line form on crown cemen· tation. lnt I Prosthodont 1992;5:137-144.

as opposed to rotary instrumentation. J Prosthet Dent 1989;62:273-277.

151

C H A P T E R

5

R E P OSITI O NING AN D C O M P LETI NG THE F I NISH L I NE WITH OSC I L LATI NG I NST R U M E NTS

R

epositioning of the finish line is accom­

retraction procedures. Traditionally, the finish line is

plished before the definitive impression is

repositioned during the impression-taking stage.

taken and approximately 3 weeks' after the

This involves retracting the gingival tissues in the

preliminay preparation phase has been completed.

prepared areas to accurately assess the intact tooth

The procedure requires the level of the finish line to

structure beyond the inish line.

be adjusted and the preparation to be refined to a more apical position immediately afier gingival de· lection (Fig 5·1). In the initial stage of tooth preparation, a non·

OSC I L LATI N G I N STRUM ENTS

A

N EW

Sonic and ultrasonic instruments may be used to

impregnated retraction cord is placed to retract the

reposition and complete the finish line. Originally

gingival tissues apically, thus making the inish line

developed for finishing the interproximal boxes of

accessible. With this increased accessibility, an exact

inlay preparations.' the instruments were gradually

finish line can be designed and inalized with one of

adopted for the delicate stage of repositioning the

4·

inish line {Figs 5-2 and 5-3) because of the need for

Since placement of a provisional prosthesis with cor­

instrument tips that could replace the classic rotating

the preparation techniques described in chapter

FIG 5-1

rect morphology will stimulate the development of

instruments. which many clinicians have dificulty

the gingiva, the deinitive impression is rarely made

controlling near the gingiva. Damage to the sulcular

at this stage. An average of 3 weeks' is recom­

and parasulcular gingival tissues often causes bleed·

mended for the development of adequate gingival

ing, reducing the efectiveness of the impression ma·

tissue prior to initiating the various sofi tissue

terials and the precision of impressions in general. .

Fig 5-1 Preparation lor an all-ceramic crown. There is a lack of space. with the finish line and the gingival sulcus in close contact. Making an impression under such conditions would lead to failure. figs 5-2 and 5-3 Images of a coarse-grit bur !stationary and in motion! used with a rotating handpiece lor conventional tooth preparation. II insufficiently controlled during use. the diamond bur can come into contact with the gingiva and cause lesions on the soft tissue. Bleeding impedes proper impression taking of the finish line and of the intact tooth beyond the finish t i ne .

FIG 5-3 152

FIG 5-2

LEVEL FOR THE FINISH LIN E P O S I TI O N

C H A P T E R

5

R E P OSITI O NING AN D C O M P LETI NG THE F I NISH L I NE WITH OSC I L LATI NG I NST R U M E NTS

R

epositioning of the finish line is accom­

retraction procedures. Traditionally, the finish line is

plished before the definitive impression is

repositioned during the impression-taking stage.

taken and approximately 3 weeks' after the

This involves retracting the gingival tissues in the

preliminay preparation phase has been completed.

prepared areas to accurately assess the intact tooth

The procedure requires the level of the finish line to

structure beyond the inish line.

be adjusted and the preparation to be refined to a more apical position immediately afier gingival de· lection (Fig 5·1). In the initial stage of tooth preparation, a non·

OSC I L LATI N G I N STRUM ENTS

A

N EW

Sonic and ultrasonic instruments may be used to

impregnated retraction cord is placed to retract the

reposition and complete the finish line. Originally

gingival tissues apically, thus making the inish line

developed for finishing the interproximal boxes of

accessible. With this increased accessibility, an exact

inlay preparations.' the instruments were gradually

finish line can be designed and inalized with one of

adopted for the delicate stage of repositioning the

4·

inish line {Figs 5-2 and 5-3) because of the need for

Since placement of a provisional prosthesis with cor­

instrument tips that could replace the classic rotating

the preparation techniques described in chapter

FIG 5-1

rect morphology will stimulate the development of

instruments. which many clinicians have dificulty

the gingiva, the deinitive impression is rarely made

controlling near the gingiva. Damage to the sulcular

at this stage. An average of 3 weeks' is recom­

and parasulcular gingival tissues often causes bleed·

mended for the development of adequate gingival

ing, reducing the efectiveness of the impression ma·

tissue prior to initiating the various sofi tissue

terials and the precision of impressions in general. .

Fig 5-1 Preparation lor an all-ceramic crown. There is a lack of space. with the finish line and the gingival sulcus in close contact. Making an impression under such conditions would lead to failure. figs 5-2 and 5-3 Images of a coarse-grit bur !stationary and in motion! used with a rotating handpiece lor conventional tooth preparation. II insufficiently controlled during use. the diamond bur can come into contact with the gingiva and cause lesions on the soft tissue. Bleeding impedes proper impression taking of the finish line and of the intact tooth beyond the finish t i ne .

FIG 5-3 152

FIG 5-2

LEVEL FOR THE FINISH LIN E P O S I TI O N

CHAPTER 5 Repositioning and Completing the Finish Line with Oscillating Instuments

. Furthermore, if the lesions develop on thin peri·

Ultrasonic power is controlled by the amplitude

odontal tissue or are extensive, more serious com·

of oscillation, which is between so and 70 �m (not,

plications could result, threatening the stability of

as some might expect, by the frequency of the

the dentogingival complex and even resulting in

waves emitted, which ranges from 28,ooo to 32.ooo

unattractive gingival recession. To prevent gingival damage, the authors devel·

Hz and cannot be controlled by the operator). The clinician regulates the intensity of oscillation to

oped ultrasonic and sonic diamond-coated tips with

modulate the abrasive effect and expand the range

medium grit that are designed to be mounted on

of application. When an ultrasonic instrument is

piezoelectric and pneumatic grips, respectivelyl Be·

used at maximum oscillation, the tip can abrade

cause ultrasonic and sonic technology work with

dentin with a progressive tissue-removal effect that

oscillating rather than rotating movement, these

can easily be controlled even by an inexperienced

instruments do not damage adjacent gingival tissue

operator. Such a high degree of control thus permits

during preparation.• A kit of ultrasonic instruments

the clinician to reposition the finish line without the

TD 1073A; ISO.IJJ.014 or ISO.IJJ.016, Komet) is

risk of creating lesions on the marginal gingiva (Figs

available with tips duplicating the shape of the

s·7 to s·tO). At the lowest level, the tip can create

modified chamfer' (see chapter 4) for completing

well-polished and well-defined surfaces comparable

the finish line on complete crown preparations (Fig

to those obtained using a medium-grit (about 7S �m)

s-4). When using ultrasonic instruments at the gin·

rotating diamond bur (Fig S·ll).

gival margin, tips should have an average grit of 91 �m and a working surface of 9 mm in length. The

Therefore, ultra-coarse-grit

(ISO· to 180-�m),

medium-grit (107·�m), and fine-grit (Jo-�m) rotating

clinician will also need tip diameters of 0.14 and

diamond burs and a rounded chisel as a manual

0.16 mm (ISO.IJJ.014 and ISO.IJJ.016), compatible

instrument were used. These were compared with

with the bur diameters most frequently used in

oscillating ultrasonic and sonic instruments, the lat·

preparing complete crowns (Figs s·s and s·6).

ter set at three different power levels (high, medium,

Repeated in vitro and clinical tests with proto·

FIG 5-4

and low).

types of these tips demonstrated that they not only

In this study (shown in Table S·l), both average

inish preparations with a high degree of precision,

roughness (which is most important) and maximum

but also reposition the level of the finish line more

roughness values were obtained. The results

apically when necessary.

showed that the ultra-coarse- and medium-grit burs ..

FIG 5-5

Fig 5-4 K i t co �taining oscillating- � onrotating (ultrasonic! margin-positioning and finishing tips (designed by D. Massironi. Italy!. These t1ps have the sam � diameters 10.14 and 0.16 mm) and shape as rotating modified chamfer burs. They serve to _ repos1t1on and complete the finiSh line preparation using oscillation rather than rotating movement. Fig 5-5 Prototype diamo � d tips. Several prototypes. with differently positioned diamond layers and different grits were d � s1gned and tested. Initially. th � tops were sectioned l �ngitudinally. with the flat part to be in contact with the gingival mar­ gin. The 1neff1c1ent des1gn was d1scarded because the l1ps only worked on one side of the preparation and easily broke. Fig 5-6 Diamond grits from 15 to 125 pm were tested. but the best results were obtained using a 9 1 - pm grit.

14

FIG 5-6

CHAPTER 5 Repositioning and Completing the Finish Line with Oscillating Instuments

. Furthermore, if the lesions develop on thin peri·

Ultrasonic power is controlled by the amplitude

odontal tissue or are extensive, more serious com·

of oscillation, which is between so and 70 �m (not,

plications could result, threatening the stability of

as some might expect, by the frequency of the

the dentogingival complex and even resulting in

waves emitted, which ranges from 28,ooo to 32.ooo

unattractive gingival recession. To prevent gingival damage, the authors devel·

Hz and cannot be controlled by the operator). The clinician regulates the intensity of oscillation to

oped ultrasonic and sonic diamond-coated tips with

modulate the abrasive effect and expand the range

medium grit that are designed to be mounted on

of application. When an ultrasonic instrument is

piezoelectric and pneumatic grips, respectivelyl Be·

used at maximum oscillation, the tip can abrade

cause ultrasonic and sonic technology work with

dentin with a progressive tissue-removal effect that

oscillating rather than rotating movement, these

can easily be controlled even by an inexperienced

instruments do not damage adjacent gingival tissue

operator. Such a high degree of control thus permits

during preparation.• A kit of ultrasonic instruments

the clinician to reposition the finish line without the

TD 1073A; ISO.IJJ.014 or ISO.IJJ.016, Komet) is

risk of creating lesions on the marginal gingiva (Figs

available with tips duplicating the shape of the

s·7 to s·tO). At the lowest level, the tip can create

modified chamfer' (see chapter 4) for completing

well-polished and well-defined surfaces comparable

the finish line on complete crown preparations (Fig

to those obtained using a medium-grit (about 7S �m)

s-4). When using ultrasonic instruments at the gin·

rotating diamond bur (Fig S·ll).

gival margin, tips should have an average grit of 91 �m and a working surface of 9 mm in length. The

Therefore, ultra-coarse-grit

(ISO· to 180-�m),

medium-grit (107·�m), and fine-grit (Jo-�m) rotating

clinician will also need tip diameters of 0.14 and

diamond burs and a rounded chisel as a manual

0.16 mm (ISO.IJJ.014 and ISO.IJJ.016), compatible

instrument were used. These were compared with

with the bur diameters most frequently used in

oscillating ultrasonic and sonic instruments, the lat·

preparing complete crowns (Figs s·s and s·6).

ter set at three different power levels (high, medium,

Repeated in vitro and clinical tests with proto·

FIG 5-4

and low).

types of these tips demonstrated that they not only

In this study (shown in Table S·l), both average

inish preparations with a high degree of precision,

roughness (which is most important) and maximum

but also reposition the level of the finish line more

roughness values were obtained. The results

apically when necessary.

showed that the ultra-coarse- and medium-grit burs ..

FIG 5-5

Fig 5-4 K i t co �taining oscillating- � onrotating (ultrasonic! margin-positioning and finishing tips (designed by D. Massironi. Italy!. These t1ps have the sam � diameters 10.14 and 0.16 mm) and shape as rotating modified chamfer burs. They serve to _ repos1t1on and complete the finiSh line preparation using oscillation rather than rotating movement. Fig 5-5 Prototype diamo � d tips. Several prototypes. with differently positioned diamond layers and different grits were d � s1gned and tested. Initially. th � tops were sectioned l �ngitudinally. with the flat part to be in contact with the gingival mar­ gin. The 1neff1c1ent des1gn was d1scarded because the l1ps only worked on one side of the preparation and easily broke. Fig 5-6 Diamond grits from 15 to 125 pm were tested. but the best results were obtained using a 9 1 - pm grit.

14

FIG 5-6

CHAPTER 5 Repositioning and Completing the Finish line with Oscillating Instruments

.. and the ultrasonic and sonic instruments performed

perpendicular to the direction of oscillation, the efect

poorly at the maximum working power, while the

is vey much reduced, or even nullified. Wavelength is

sonic instrument at low power achieved a finishing

directly proportional to speed in that shot waves

effect similar to that using fine- and medium-grit

move at high speeds. In the case of ultrasonic waves,

burs, and in some aspects a manual rounded chisel.

it is possible to reach a frequency of 32,000 Hz, but

These results demonstrate how a change in heat

the working area is vey small because the amplitude

intensity alters the effectiveness of the tool. At high

of oscillation (../2) is very small, resulting in a limited

power, the ultrasonic and sonic instruments are per­

number of diamond granules working in a single direc­

fectly suitable for repositioning the finish line of a

tion. Because the ultrasonic tip works at high oscilla­

preparation, but at lower levels their effect is limit·

tions, it produces a surface that does not appear

ed to polishing and finishing.

smooth and uniform, but the tool works very efi­

FIG 5-8

FIG 5-7

FIG 5-10

FIG 5-9

ciently if the tip is kept properly oriented. The sonic instrument (Sonicflex, KaVa) uses a

CO M PARING SONIC AND

pneumatic feed and requires insertion of a multi flex

U LTRAS O N I C I N STRUM ENTS

attachment in place of the high-speed air turbine. The multiflex attachment is composed of a hollow

A comparison of sonic and ultrasonic instruments

cylinder with an interior sheath or tube with to lat­

highlights the diferent characteristics of each.6 The

eral holes. The cylinder rotates as a result of pres­

ultrasonic instrument is electric: An alternating cur­

surized air that the operator controls with a pedal

rent produces a series of volumetric contractions in

switch. The oscillation frequency (around 6,ooo Hz)

quart2 cystals, which generate localized propaga­

is much lower than that of the ultrasonic instrument

tion waves (peak to peak, between so and

70

�m)

but generates a three-dimensional elliptical move­

in a restricted area with bidirectional and linear

ment, with both longitudinal and transversal com­

movement. The diamond-coated tips can be used

ponents, that renders the entire tip active. The sonic

only on the ultrasonic tool or grip, which features

tip will abrade the surface of the tooth regardless of

front and rear resonance chambers on either side of

its position relative to the tooth.

the middle cystals. The rear resonance chambers

The amplitude of the oscillation has a peak­

are triggered by an activator and transform the wave

to-peak range of 120 to 250 �m. sufficient For a

from longitudinal to transversal. The sound wave

rotational movement on small surfaces. It creates a

thus creates an oscillation in the tip, which is coat­

less abrasive efect than ultrasonic instruments and

ed with diamond granules.

Fig 5-7 Although lhe tip is in contact with the gingiva. there are no visible lesions. It i s important to irrigate the tool with a stream of water to avoid overheating the tip and the prepared tooth. or it could result in the formation of a superficial lesion on the soft lis­ sues.

Fig 5-8 Tooth preparation for a fixed partial denture. The ultrasonic tip is being used to reposition the finish line more apically.

Figs 5-9 and 5-10 Degree of finishing and condition of the gingiva following repositioning. at high magnification. The tissue is free of lesions and bleeding. Fig 5-11 Surface of a tooth prepared using an ultrasonic lip. This image shows the difference i n surface quality obtained with two levels of oscillation intensity. AI higher oscillation, the surface takes on irregularities (large area). w h i le at lower oscillation the surface appears smoothly polished (small area).

FIG 5-11

TABLE 5-1 Degree of roughness obtained with rotating, ultrasonic, and manual instruments Average

allows a greater working area at the tip. With its

Maximum

64-�m-grit diamond layer, pneumatic feed, and grip­

Instrument

amplitude /2) between two waves; the smaller the

regulated intensity (Ievet t, range amplitude [raj = 120

Ultra-coarse-grit (t8o-�m) bur

24.3

51.8

diameter of the tip, the closer together the waves are

:

15 �m; level 2, ra

Medium-grit (107-�m) bur

14.2

35.1

and the more the tip oscillates. Because the wave

:

15 �m), the sonic tool can be used effectively to

moves in a linear ashion, the oscillation produces

reposition the finish line and finish the suraces.

=

160

: 15

�m; level 3, ra

=

250

maximum tissue removal when the tip is aligned with

The authors have used various diamond grits (eg,

the direction of wave movement. If t he t i p is orient ed

21, 46, and 91 �m) and have discovered that both ..

Fine-grit (30-�m) bur Ultrasonic instrument (EMS)

roughness* (tm)

roughnesst (Jm)

The abrasive efect of the tip depends on the

8.9

13.1

15.4

23.5

Sonic (Sonicflex) instrument, minimum power

12.6

19.0

Sonic (Sonicflex) instrument, maximum power

16.9

28.3

7.2

15.3

Rounded chisel, manual action

•Average roughness (R7) i s t h e mean value obtained from t h e single roughness values of ive subsequent measuring lengths i n the roughness profile. 'Maximum roughness (R max) is the highest of the five single roughness values. 16

17

CHAPTER 5 Repositioning and Completing the Finish line with Oscillating Instruments

.. and the ultrasonic and sonic instruments performed

perpendicular to the direction of oscillation, the efect

poorly at the maximum working power, while the

is vey much reduced, or even nullified. Wavelength is

sonic instrument at low power achieved a finishing

directly proportional to speed in that shot waves

effect similar to that using fine- and medium-grit

move at high speeds. In the case of ultrasonic waves,

burs, and in some aspects a manual rounded chisel.

it is possible to reach a frequency of 32,000 Hz, but

These results demonstrate how a change in heat

the working area is vey small because the amplitude

intensity alters the effectiveness of the tool. At high

of oscillation (../2) is very small, resulting in a limited

power, the ultrasonic and sonic instruments are per­

number of diamond granules working in a single direc­

fectly suitable for repositioning the finish line of a

tion. Because the ultrasonic tip works at high oscilla­

preparation, but at lower levels their effect is limit·

tions, it produces a surface that does not appear

ed to polishing and finishing.

smooth and uniform, but the tool works very efi­

FIG 5-8

FIG 5-7

FIG 5-10

FIG 5-9

ciently if the tip is kept properly oriented. The sonic instrument (Sonicflex, KaVa) uses a

CO M PARING SONIC AND

pneumatic feed and requires insertion of a multi flex

U LTRAS O N I C I N STRUM ENTS

attachment in place of the high-speed air turbine. The multiflex attachment is composed of a hollow

A comparison of sonic and ultrasonic instruments

cylinder with an interior sheath or tube with to lat­

highlights the diferent characteristics of each.6 The

eral holes. The cylinder rotates as a result of pres­

ultrasonic instrument is electric: An alternating cur­

surized air that the operator controls with a pedal

rent produces a series of volumetric contractions in

switch. The oscillation frequency (around 6,ooo Hz)

quart2 cystals, which generate localized propaga­

is much lower than that of the ultrasonic instrument

tion waves (peak to peak, between so and

70

�m)

but generates a three-dimensional elliptical move­

in a restricted area with bidirectional and linear

ment, with both longitudinal and transversal com­

movement. The diamond-coated tips can be used

ponents, that renders the entire tip active. The sonic

only on the ultrasonic tool or grip, which features

tip will abrade the surface of the tooth regardless of

front and rear resonance chambers on either side of

its position relative to the tooth.

the middle cystals. The rear resonance chambers

The amplitude of the oscillation has a peak­

are triggered by an activator and transform the wave

to-peak range of 120 to 250 �m. sufficient For a

from longitudinal to transversal. The sound wave

rotational movement on small surfaces. It creates a

thus creates an oscillation in the tip, which is coat­

less abrasive efect than ultrasonic instruments and

ed with diamond granules.

Fig 5-7 Although lhe tip is in contact with the gingiva. there are no visible lesions. It i s important to irrigate the tool with a stream of water to avoid overheating the tip and the prepared tooth. or it could result in the formation of a superficial lesion on the soft lis­ sues.

Fig 5-8 Tooth preparation for a fixed partial denture. The ultrasonic tip is being used to reposition the finish line more apically.

Figs 5-9 and 5-10 Degree of finishing and condition of the gingiva following repositioning. at high magnification. The tissue is free of lesions and bleeding. Fig 5-11 Surface of a tooth prepared using an ultrasonic lip. This image shows the difference i n surface quality obtained with two levels of oscillation intensity. AI higher oscillation, the surface takes on irregularities (large area). w h i le at lower oscillation the surface appears smoothly polished (small area).

FIG 5-11

TABLE 5-1 Degree of roughness obtained with rotating, ultrasonic, and manual instruments Average

allows a greater working area at the tip. With its

Maximum

64-�m-grit diamond layer, pneumatic feed, and grip­

Instrument

amplitude /2) between two waves; the smaller the

regulated intensity (Ievet t, range amplitude [raj = 120

Ultra-coarse-grit (t8o-�m) bur

24.3

51.8

diameter of the tip, the closer together the waves are

:

15 �m; level 2, ra

Medium-grit (107-�m) bur

14.2

35.1

and the more the tip oscillates. Because the wave

:

15 �m), the sonic tool can be used effectively to

moves in a linear ashion, the oscillation produces

reposition the finish line and finish the suraces.

=

160

: 15

�m; level 3, ra

=

250

maximum tissue removal when the tip is aligned with

The authors have used various diamond grits (eg,

the direction of wave movement. If t he t i p is orient ed

21, 46, and 91 �m) and have discovered that both ..

Fine-grit (30-�m) bur Ultrasonic instrument (EMS)

roughness* (tm)

roughnesst (Jm)

The abrasive efect of the tip depends on the

8.9

13.1

15.4

23.5

Sonic (Sonicflex) instrument, minimum power

12.6

19.0

Sonic (Sonicflex) instrument, maximum power

16.9

28.3

7.2

15.3

Rounded chisel, manual action

•Average roughness (R7) i s t h e mean value obtained from t h e single roughness values of ive subsequent measuring lengths i n the roughness profile. 'Maximum roughness (R max) is the highest of the five single roughness values. 16

17

CHAPTER 5 Repositioning and Completing the Finish Line with Oscillating Instruments

�

larger and smaller grits can be used effectively for

case, a gingival lesion and subsequent blood now

the removal of dentin, as well as for simple polish­

would jeopardize the outcome of the impression.

finish line. The lack of rotation is the instruments'

mond granules eventually fall of (Fig 5-25) . Such

most important feature, permitting ideal control. With

problems are not unique to sonic and ultrasonic

ing. The production of tips with diferent grits and

From years of experimentation to improve sonic

the possibility of modulating the oscillation intensity

instruments, since breaks also occur in scaling in·

diameters is expected so that a full range of oscillat­

and ultrasonic instruments, the authors have had

of the instrument, the clinician is able to reposition

struments (Fig 5-26). However, these instruments

ing implements will be available (Figs 5-12 to 5-21).

ample opportunity to determine their optimal use.

and complete the finish line without causing even

should be examined fai rly regularly under magnifica­

minimal lesions in the marginal gingiva.

tion and replaced when they start to show signs of

The choice between an ultrasonic or sonic system

The first requirement of sonic and ultrasonic instru­

is often dictated more by the type of system cur­

ments is internal irrigation to prevent overheating

The surface obtained by using the sonic instru­

rently available in an oice, rather than by marked

that may damage dentin and pulp and to avoid

ments is irregular, with a pockmarked appearance

number of teeth prepared but far less than the com­

preference or understanding of operational differ­

breaking the diamond tips. The sonic and ultrasonic

(Figs 5-22 and 5-23), unlike the circular little grooves

parable wear of rotating tips. In the authors' experi­

ences. A sonic tool will vibrate constantly, regardless

tools need about 15 and 30 ml/min of water respec­

that are produced by a rotating diamond bur. In

ence, the instruments need to be replaced, on aver­

of the operating pressure, producing a good efect

tively for cooling.8·9 The presence of water between

theory, such a surface should provide better adhe­

age, two or three times per year. In clinical practice, a retraction cord is inserted to obtain the vertical displacement of the gingival tis­

wear. The degree of wear is proportional to the

that removes dentinal tissue during the repositioning

the tip and the tooth surface can result in an unde­

sion by permitting the cement to cover more area.

of the finish line. The ultrasonic tool, with its bi­

sirable hydroplaning effect. similar to the situation

According to the literature,'0 the ideal degree of pol­

directional oscillation, works optimally only when

that occurs between a car tire and a wet road. The

ishing of dental preparations, which can be mea­

sue, and the sonic or ultrasonic instrument is used

the operator matches the working direction to that

liquid layer nullifies the oscillating effect of the

sured with a roughness profilometer, is between 5

in combination with a stereomicroscope, initially in

of the wave. The preparation of a surface through

instrument, and the dental assistant must aim inter­

and 10 �m. Below this value, the cement adheres

direct view of the buccal area and then in indi rect

widespread removal of tissue yields a better result

mittent jets of air at the prepared tooth to restore

less efectively to the surfaces of the prepared tooth,

view of the palatal area and interproximal relation­

when sonic instruments are used. Moreover, because

normal functioning.

while above 12 �m the cement does not spread

ships of all the teeth involved (Figs 5-27 and 5-28).

evenly, leaving uncemented spots."

The exceptional control provided by oscillating instru­

the elliptical movement is more convenient and the

Another requirement for ideal functioning of an

intensity of the sonic instrument can be easily regu­

ultrasonic instrument is the proper difusion and

Diamond tips used with sonic and ultrasonic

ments prevents damage to the paramarginal gingiva

lated to create uniform and well-polished surfaces,

direction of the ultrasonic waves that are generated

instruments have greater longevity than diamond

and thus provides a more accessible finish line dur­ ing the inishing and i mpression stages (Figs 5-29 to

the sonic system is easier for the clinician to master'

11

�

in the handle by the quartz crystals, which oscillate

burs used with rotating instruments. Oscillation of

in response to the piezoelectric stimulation. These

the tips keeps wear to a minimum by avoiding the

5-37). Taking the impression will also be made eas-

waves pass through the grip and the cuvature of the

stress of high-speed rotation and limiting the stress

ier by the absence of gingival lesions. I n addition,

OPTI MAL USE OF OSCI LLATI NG

stem to the tip, where their intensity is at its peak,

to the abrasion of the tooth surface.

I N STRUM ENTS

with the exception of the two linear areas distal and

These instruments can break if used improperly

mesial to the tip. If the instrument is positioned

or without water (Fig 5-24). and, as is true for all

In addition to the versatility of oscillating instru­

curve on nat. it will have the least effect because

instruments with an abrasive diamond layer, the dia-

ments, their greatest advantage is lack of rotation,

that area of the tip is free of waves. If the tip is sim­

which permits absolute control during the most del­

ply rotated a few degrees, it will function perfectly,

icate stages of preparation and reduces the risk of

although its best efect will still be above and below

gingival lesions. This also benefits impression mak­

the point of the wave's maximum peak.

ing because it eliminates the need to remove blood

In the author's opinion, the use of sonic and ultra­

from the area before making an impression. Oscillat·

sonic instruments constitutes an innovative system of

ing instruments are particularly useful when nonim­

preparation. While they do not replace rotating instru­

pregnated retraction cords are used, resulting in

ments in the preparation stage, these instruments can

minimal vertical retraction of the gingiva; in such a

be of great value in repositioning and completing the .

the continuous irrigation with intermittent water and air spray results, in most cases, in the need for only one retraction cord, with obvious benefits for the ac­

curacy of the planned finish line (Figs 5-38 to 5-47). •

159

CHAPTER 5 Repositioning and Completing the Finish Line with Oscillating Instruments

�

larger and smaller grits can be used effectively for

case, a gingival lesion and subsequent blood now

the removal of dentin, as well as for simple polish­

would jeopardize the outcome of the impression.

finish line. The lack of rotation is the instruments'

mond granules eventually fall of (Fig 5-25) . Such

most important feature, permitting ideal control. With

problems are not unique to sonic and ultrasonic

ing. The production of tips with diferent grits and

From years of experimentation to improve sonic

the possibility of modulating the oscillation intensity

instruments, since breaks also occur in scaling in·

diameters is expected so that a full range of oscillat­

and ultrasonic instruments, the authors have had

of the instrument, the clinician is able to reposition

struments (Fig 5-26). However, these instruments

ing implements will be available (Figs 5-12 to 5-21).

ample opportunity to determine their optimal use.

and complete the finish line without causing even

should be examined fai rly regularly under magnifica­

minimal lesions in the marginal gingiva.

tion and replaced when they start to show signs of

The choice between an ultrasonic or sonic system

The first requirement of sonic and ultrasonic instru­

is often dictated more by the type of system cur­

ments is internal irrigation to prevent overheating

The surface obtained by using the sonic instru­

rently available in an oice, rather than by marked

that may damage dentin and pulp and to avoid

ments is irregular, with a pockmarked appearance

number of teeth prepared but far less than the com­

preference or understanding of operational differ­

breaking the diamond tips. The sonic and ultrasonic

(Figs 5-22 and 5-23), unlike the circular little grooves

parable wear of rotating tips. In the authors' experi­

ences. A sonic tool will vibrate constantly, regardless

tools need about 15 and 30 ml/min of water respec­

that are produced by a rotating diamond bur. In

ence, the instruments need to be replaced, on aver­

of the operating pressure, producing a good efect

tively for cooling.8·9 The presence of water between

theory, such a surface should provide better adhe­

age, two or three times per year. In clinical practice, a retraction cord is inserted to obtain the vertical displacement of the gingival tis­

wear. The degree of wear is proportional to the

that removes dentinal tissue during the repositioning

the tip and the tooth surface can result in an unde­

sion by permitting the cement to cover more area.

of the finish line. The ultrasonic tool, with its bi­

sirable hydroplaning effect. similar to the situation

According to the literature,'0 the ideal degree of pol­

directional oscillation, works optimally only when

that occurs between a car tire and a wet road. The

ishing of dental preparations, which can be mea­

sue, and the sonic or ultrasonic instrument is used

the operator matches the working direction to that

liquid layer nullifies the oscillating effect of the

sured with a roughness profilometer, is between 5

in combination with a stereomicroscope, initially in

of the wave. The preparation of a surface through

instrument, and the dental assistant must aim inter­

and 10 �m. Below this value, the cement adheres

direct view of the buccal area and then in indi rect

widespread removal of tissue yields a better result

mittent jets of air at the prepared tooth to restore

less efectively to the surfaces of the prepared tooth,

view of the palatal area and interproximal relation­

when sonic instruments are used. Moreover, because

normal functioning.

while above 12 �m the cement does not spread

ships of all the teeth involved (Figs 5-27 and 5-28).

evenly, leaving uncemented spots."

The exceptional control provided by oscillating instru­

the elliptical movement is more convenient and the

Another requirement for ideal functioning of an

intensity of the sonic instrument can be easily regu­

ultrasonic instrument is the proper difusion and

Diamond tips used with sonic and ultrasonic

ments prevents damage to the paramarginal gingiva

lated to create uniform and well-polished surfaces,

direction of the ultrasonic waves that are generated

instruments have greater longevity than diamond

and thus provides a more accessible finish line dur­ ing the inishing and i mpression stages (Figs 5-29 to

the sonic system is easier for the clinician to master'

11

�

in the handle by the quartz crystals, which oscillate

burs used with rotating instruments. Oscillation of

in response to the piezoelectric stimulation. These

the tips keeps wear to a minimum by avoiding the

5-37). Taking the impression will also be made eas-

waves pass through the grip and the cuvature of the

stress of high-speed rotation and limiting the stress

ier by the absence of gingival lesions. I n addition,

OPTI MAL USE OF OSCI LLATI NG

stem to the tip, where their intensity is at its peak,

to the abrasion of the tooth surface.

I N STRUM ENTS

with the exception of the two linear areas distal and

These instruments can break if used improperly

mesial to the tip. If the instrument is positioned

or without water (Fig 5-24). and, as is true for all

In addition to the versatility of oscillating instru­

curve on nat. it will have the least effect because

instruments with an abrasive diamond layer, the dia-

ments, their greatest advantage is lack of rotation,

that area of the tip is free of waves. If the tip is sim­

which permits absolute control during the most del­

ply rotated a few degrees, it will function perfectly,

icate stages of preparation and reduces the risk of

although its best efect will still be above and below

gingival lesions. This also benefits impression mak­

the point of the wave's maximum peak.

ing because it eliminates the need to remove blood

In the author's opinion, the use of sonic and ultra­

from the area before making an impression. Oscillat·

sonic instruments constitutes an innovative system of

ing instruments are particularly useful when nonim­

preparation. While they do not replace rotating instru­

pregnated retraction cords are used, resulting in

ments in the preparation stage, these instruments can

minimal vertical retraction of the gingiva; in such a

be of great value in repositioning and completing the .

the continuous irrigation with intermittent water and air spray results, in most cases, in the need for only one retraction cord, with obvious benefits for the ac­

curacy of the planned finish line (Figs 5-38 to 5-47). •

159

C IAIT R Repositioning and Completing the Finish Line with Oscillating Instruments

F1g 5-12 Sonic grip and tips. The sonic instrument usu pneumatic power and elliptical low-frequency. 6-MHz waves to produce good finish linu. Tips are available in diameters of 0.14 and 0.16 mm !Sf 919.000.014 and Sf 919.000.016. Kamel).

Fig 5-13 Prototype sonic lips with varying stem curvature radii. The straight stem (not available) transmits greater vibration and oscillation than the curved stem and causes more discomfort for the patient.

fig 5-16 Use of sonic instrument prior to the positioning of a retraction cord. fig 5-17 Healthy gingiva. after placement of the vertical retraction cord and during the apical repositioning of the finish line.

f1gs 5-14 1nd 5-15 Sonic lip poSitioned along the long axis of the tooth. The advantage of the sonic tool is thai it works e q ually well in all posi­ tions and direc11ons. unlike the ullruonlt Instrument.

lG

111

C IAIT R Repositioning and Completing the Finish Line with Oscillating Instruments

F1g 5-12 Sonic grip and tips. The sonic instrument usu pneumatic power and elliptical low-frequency. 6-MHz waves to produce good finish linu. Tips are available in diameters of 0.14 and 0.16 mm !Sf 919.000.014 and Sf 919.000.016. Kamel).

Fig 5-13 Prototype sonic lips with varying stem curvature radii. The straight stem (not available) transmits greater vibration and oscillation than the curved stem and causes more discomfort for the patient.

fig 5-16 Use of sonic instrument prior to the positioning of a retraction cord. fig 5-17 Healthy gingiva. after placement of the vertical retraction cord and during the apical repositioning of the finish line.

f1gs 5-14 1nd 5-15 Sonic lip poSitioned along the long axis of the tooth. The advantage of the sonic tool is thai it works e q ually well in all posi­ tions and direc11ons. unlike the ullruonlt Instrument.

lG

111

CHA . . Repositioning and Completing the Finish Line with Oscillating Instuments

Figs 5-18 and 5-1 g Stereomicroscope views of finish line before and after apical repositioning with the pneumatic sonic instrument (magnifi­ cation X 25).

112

Figs 5-20 and 5-21 New position of the finish line achieved easily and without trauma using the sonic tool following placement of only one impregnated retraction cord !magnification x 2 5).

CHA . . Repositioning and Completing the Finish Line with Oscillating Instuments

Figs 5-18 and 5-1 g Stereomicroscope views of finish line before and after apical repositioning with the pneumatic sonic instrument (magnifi­ cation X 25).

112

Figs 5-20 and 5-21 New position of the finish line achieved easily and without trauma using the sonic tool following placement of only one impregnated retraction cord !magnification x 2 5).

CHAPTER 5 Repositioning and Completing the Finish Line with Oscillating Instruments

Figs 5-22 and 5-23 Two polyether impressions of the same molar. The surface of the first impression has the regular. horizontal lines from treat­ ment with a rotating bur. In the second impression. the irregular. pockmarked surface and absence of horizontal lines results from the oscil­ lation of an ultrasonic instrument. Fig 5-24 Broken stem of an ultrasonic instrument. after use. Fig 5-25 Ultrasonic tip showing wear i n the dia­ mond grit. Oscillating tips are subject to less wear than traditional burs. because there is no rotation impact. Fig 5-16 Broken tools used to remove calcified tartar and plaque. Figs 5-27 and 5-28 Correct repositioning and completion of finish line using an ultrasonic instrument. with placement of one retraction cord. The finish line has shifted apically without evident alteration at the gingival level. Fig 5-29 Clinical case involving the removal of an inadequate metal-ceramic restoration. A well-integrated provisional prosthesis has been placed for finishing and taking the impression. 14

15

CHAPTER 5 Repositioning and Completing the Finish Line with Oscillating Instruments

Figs 5-22 and 5-23 Two polyether impressions of the same molar. The surface of the first impression has the regular. horizontal lines from treat­ ment with a rotating bur. In the second impression. the irregular. pockmarked surface and absence of horizontal lines results from the oscil­ lation of an ultrasonic instrument. Fig 5-24 Broken stem of an ultrasonic instrument. after use. Fig 5-25 Ultrasonic tip showing wear i n the dia­ mond grit. Oscillating tips are subject to less wear than traditional burs. because there is no rotation impact. Fig 5-16 Broken tools used to remove calcified tartar and plaque. Figs 5-27 and 5-28 Correct repositioning and completion of finish line using an ultrasonic instrument. with placement of one retraction cord. The finish line has shifted apically without evident alteration at the gingival level. Fig 5-29 Clinical case involving the removal of an inadequate metal-ceramic restoration. A well-integrated provisional prosthesis has been placed for finishing and taking the impression. 14

15

CHAPTER 5 Repositioning and Completing the Finish Line with Oscillating Instuments

5·3 1

fig 5-30 Prepared tooth after the first preparation. prior to adaptation of the provisional.

fig 5-31 Frontal view through the stereomicroscope. Note the healthy gingiva prior to placement of the retraction cord.

Fig 5-32 Position of the gingiva and its close contact with the finish tine would compromise the impression without adequate retraction.

fig 5-33 Displacement of the gingival tissue (Gingi-Aid Z-Twist no. 00. Gingi Paki.The retraction cord vertically deflects the gingiva. The clin­ ician can easily measure the extent of this displacement in relation to the level of the finish line before retraction to calculate the juxta­ gingival placement of the prosthetic margin during repositioning.

fig 5-4 Note the horizontal displacement caused by the retraction cord and the vertical distance between the cord and the finish line.

14

167

CHAPTER 5 Repositioning and Completing the Finish Line with Oscillating Instuments

5·3 1

fig 5-30 Prepared tooth after the first preparation. prior to adaptation of the provisional.

fig 5-31 Frontal view through the stereomicroscope. Note the healthy gingiva prior to placement of the retraction cord.

Fig 5-32 Position of the gingiva and its close contact with the finish tine would compromise the impression without adequate retraction.

fig 5-33 Displacement of the gingival tissue (Gingi-Aid Z-Twist no. 00. Gingi Paki.The retraction cord vertically deflects the gingiva. The clin­ ician can easily measure the extent of this displacement in relation to the level of the finish line before retraction to calculate the juxta­ gingival placement of the prosthetic margin during repositioning.

fig 5-4 Note the horizontal displacement caused by the retraction cord and the vertical distance between the cord and the finish line.

14

167

CHAPTER \ Repositioning and Completing the Finish Line with Oscillating Instruments

Fig 5-35 Oscillating tip during apical repositioning of the finish line. The lack of rotation permits precise control. and the soft tissue shows no sign of damage. Figs 5-36 and 5-37 Manual chisel during the finishing stage. High magnification shows the dentinal debris removed during polishing.

11

Figs 5-38 and 5-39 B u ccal and palatal views of working cast in epoxy resin. before epoxy die trimming. The horizontal space delineated by the retraction cord allows the clinician to easily evaluate the finish line. without doubts about extension.

Fig 5-0 Captek metal structure (leach

&

Dillon) realized on the master cast.

169

CHAPTER \ Repositioning and Completing the Finish Line with Oscillating Instruments

Fig 5-35 Oscillating tip during apical repositioning of the finish line. The lack of rotation permits precise control. and the soft tissue shows no sign of damage. Figs 5-36 and 5-37 Manual chisel during the finishing stage. High magnification shows the dentinal debris removed during polishing.

11

Figs 5-38 and 5-39 B u ccal and palatal views of working cast in epoxy resin. before epoxy die trimming. The horizontal space delineated by the retraction cord allows the clinician to easily evaluate the finish line. without doubts about extension.

Fig 5-0 Captek metal structure (leach

&

Dillon) realized on the master cast.

169

Repoa1tlonmg

nd Completing the

Flm

h Line w1lh

0

clllalmg Instruments

]

5·43

F1g � 41 Captek metal structure tluch & 011tonl. trlld In the pat11nt's mouth f1g I 42 Cond111on al the g1ng1va during the try-1n 1nd1talt1 the clinician's rupect lor the tluuu In adaplltlon of the provisional and in the t1k1ng of the lmprtulon

170

Fig 5-43 Preoperative view o f clinical case.

flgs S-4 Definitive metal-ceramic crown with integrated g1ngival marg1n

171

Repoa1tlonmg

nd Completing the

Flm

h Line w1lh

0

clllalmg Instruments

]

5·43

F1g � 41 Captek metal structure tluch & 011tonl. trlld In the pat11nt's mouth f1g I 42 Cond111on al the g1ng1va during the try-1n 1nd1talt1 the clinician's rupect lor the tluuu In adaplltlon of the provisional and in the t1k1ng of the lmprtulon

170

Fig 5-43 Preoperative view o f clinical case.

flgs S-4 Definitive metal-ceramic crown with integrated g1ngival marg1n

171

CHAPTER 5 Repositioning and Completing the Finish Line with Oscillating Instruments

REFERENCES

7. Schmidlin PR, Beuchat M, Busslinger A, Lehmann 8, lutz F. Tooth substance loss resulting from mechanical. sonic and ultrasonic root instrumentation assessed by

1. Wilson RD. Maynard G. lntracrevicular restorative den­ tistry. lnt J Periodontics Restorative Dent t98t;t:J4-49-

liquid scintillation. I Clin Periodontal 2001;28:1058-1o66.

2. Krejci I, Lutz F, Krejci D. Schall· ultraschallbetriebene

8. Zesewitz H. Klaiber 8, Hot2 P, Hugo B. Heat propagation

diamantierte lnstrumente zur Kavitatenpraparation. zum

in dentin during cavity preparation in vitro with oscil·

Konturieren und zum Rnieren. ZWR t995:to4:78t-786.

lating instruments [in Germani. Schweiiz Monatsschr

3· Kocher

.

Zahnmed 2005;115:536-541.

Plagmann HC. The diamond-coated sonic

scaler tip. Part II: loss of substance and alteration of

9· Kocher T, Plagmann HC. Heat propagation in dentin

root surface texture after diferent scaling modalities. lnt

during instrumentation with diferent sonic scaler tips.

I Periodontics Restorative Dent 1997:17:484-493.

Quintessence lnt 1996;27:259-264.

4- Massironi 0. 'utilizzo di strumenti diamantati non

10. Gilde H. Lenz P, Richter U. Experimentelle und statis ·

rotanti a funzionamento ultrasonico. Teamwork 2001;3:

tiche Untersuchungen zur Pr�parationsmethodik. Otsch

26-34·

Zahnarztl z 1984:39:798-800.

s- Massironi D. Banistelli A Sistema di preparazione per

corone complete. Masson Protech 2000;J :JS-476. Drisko CL, Cochran DL, Blieden T, et al. Postion paper:

n.

Wegmann U. Quality of ground enamel suraces and preparation margins [in German). Dtsch Zahnarztl Z 1985:40=472-478.

Sonic and ultrasonic scalers in periodontics. Research, Science and Therapy Committee of the American Academy of Periodontology. I Periodontal 2000;71: 1792-1801.

Figs 5-45 and 5-46 Excellent integration ol the metal-ceramic restoration with the gingiva alter cementation.

Fig 5-47 Lateral view of clinical adaptation of the restoration margin through the stereomicroscope.

172

173

CHAPTER 5 Repositioning and Completing the Finish Line with Oscillating Instruments

REFERENCES

7. Schmidlin PR, Beuchat M, Busslinger A, Lehmann 8, lutz F. Tooth substance loss resulting from mechanical. sonic and ultrasonic root instrumentation assessed by

1. Wilson RD. Maynard G. lntracrevicular restorative den­ tistry. lnt J Periodontics Restorative Dent t98t;t:J4-49-

liquid scintillation. I Clin Periodontal 2001;28:1058-1o66.

2. Krejci I, Lutz F, Krejci D. Schall· ultraschallbetriebene

8. Zesewitz H. Klaiber 8, Hot2 P, Hugo B. Heat propagation

diamantierte lnstrumente zur Kavitatenpraparation. zum

in dentin during cavity preparation in vitro with oscil·

Konturieren und zum Rnieren. ZWR t995:to4:78t-786.

lating instruments [in Germani. Schweiiz Monatsschr

3· Kocher

.

Zahnmed 2005;115:536-541.

Plagmann HC. The diamond-coated sonic

scaler tip. Part II: loss of substance and alteration of

9· Kocher T, Plagmann HC. Heat propagation in dentin

root surface texture after diferent scaling modalities. lnt

during instrumentation with diferent sonic scaler tips.

I Periodontics Restorative Dent 1997:17:484-493.

Quintessence lnt 1996;27:259-264.

4- Massironi 0. 'utilizzo di strumenti diamantati non

10. Gilde H. Lenz P, Richter U. Experimentelle und statis ·

rotanti a funzionamento ultrasonico. Teamwork 2001;3:

tiche Untersuchungen zur Pr�parationsmethodik. Otsch

26-34·

Zahnarztl z 1984:39:798-800.

s- Massironi D. Banistelli A Sistema di preparazione per

corone complete. Masson Protech 2000;J :JS-476. Drisko CL, Cochran DL, Blieden T, et al. Postion paper:

n.

Wegmann U. Quality of ground enamel suraces and preparation margins [in German). Dtsch Zahnarztl Z 1985:40=472-478.

Sonic and ultrasonic scalers in periodontics. Research, Science and Therapy Committee of the American Academy of Periodontology. I Periodontal 2000;71: 1792-1801.

Figs 5-45 and 5-46 Excellent integration ol the metal-ceramic restoration with the gingiva alter cementation.

Fig 5-47 Lateral view of clinical adaptation of the restoration margin through the stereomicroscope.

172

173

C H A P T E R

6

T E C H N I C A L C O N S I D E R AT I O N S F O R S O FT T I S S U E R ET RACT I O N

6-2

G

ingival retraction requires healthy periodontal

Supragingival restoration margins are considered

tissue that is free of pathology and inflam­

to be most favorable for oral health, in part because

mation (Figs 6-1 to 6-3). Accurate analysis of

of their greater accessibility.' The supragingival posi­

the periodontal tissue should be performed during

tion provides access during all stages of treatment:

the diagnostic stage to identify periodontal disease.

tooth preparation, finishing, impression taking, try·

anomalies, or insufficient supporting tissue (Figs 6·4

in, and cementation. Despite the advantage of greater

and 6-5). Gingival probing is essential for evaluating

access, the supragingival restoration margin offers

periodontal health and deciding whether surgery is

poor esthetics; it is generally indicated for the lingual

necessary. Prosthetic restoration can begin only after

aspect of prepared teeth.

the clinical condition of the gingiva has been identi­

A finish line in a juxtagingival position is more

fied and phase one treatment has been completed.

esthetic but lies closer to the gingival tissue. The

When taking impressions, the clinician should verify

juxtagingival restoration margin is used for the buc­

the gingival biotype to determine how to proceed

cal aspect of mandibular molars and premolars.

with the gingival displacement (Figs 6-6 to 6-9).

The intracrevicular position is best for addressing esthetic concerns or for the following indications2: a need for greater retention and resistance because of

DETERM I N I N G THE POSITION O F

i ncreased height and surface area of the restoration;

THE RESTORATION MARGIN

presence of caries or old restorations at the margin,

Fin ish line positions

ture; or the problem of an accentuated radicular sen­

requiring an apical shift to find healthy dental struc­

174

6·5

sitivity in prepared teeth.

Restoration margins can be placed in one of three

In the past, the position of a restoration margin

areas of the gingiva: supragingival, iuxtagingival, or

was thought to be the cause of periodontal lesions

intracrevicular.

and other problems, but today the influence of the ..

Fig 6-1 Healthy periodontium is indispensable for successful gingival retraction. figs 6-2 and 6-3 Gingival margin with natural dentition !at 24 x and 50 X magnification). Figs 6-4 and 6-5 Periodontal probing and analysis of the keratinized tissue help to classify the gingival biotype and to ensure stability and integrity of the restoration margin over lime.

C H A P T E R

6

T E C H N I C A L C O N S I D E R AT I O N S F O R S O FT T I S S U E R ET RACT I O N

6-2

G

ingival retraction requires healthy periodontal

Supragingival restoration margins are considered

tissue that is free of pathology and inflam­

to be most favorable for oral health, in part because

mation (Figs 6-1 to 6-3). Accurate analysis of

of their greater accessibility.' The supragingival posi­

the periodontal tissue should be performed during

tion provides access during all stages of treatment:

the diagnostic stage to identify periodontal disease.

tooth preparation, finishing, impression taking, try·

anomalies, or insufficient supporting tissue (Figs 6·4

in, and cementation. Despite the advantage of greater

and 6-5). Gingival probing is essential for evaluating

access, the supragingival restoration margin offers

periodontal health and deciding whether surgery is

poor esthetics; it is generally indicated for the lingual

necessary. Prosthetic restoration can begin only after

aspect of prepared teeth.

the clinical condition of the gingiva has been identi­

A finish line in a juxtagingival position is more

fied and phase one treatment has been completed.

esthetic but lies closer to the gingival tissue. The

When taking impressions, the clinician should verify

juxtagingival restoration margin is used for the buc­

the gingival biotype to determine how to proceed

cal aspect of mandibular molars and premolars.

with the gingival displacement (Figs 6-6 to 6-9).

The intracrevicular position is best for addressing esthetic concerns or for the following indications2: a need for greater retention and resistance because of

DETERM I N I N G THE POSITION O F

i ncreased height and surface area of the restoration;

THE RESTORATION MARGIN

presence of caries or old restorations at the margin,

Fin ish line positions

ture; or the problem of an accentuated radicular sen­

requiring an apical shift to find healthy dental struc­

174

6·5

sitivity in prepared teeth.

Restoration margins can be placed in one of three

In the past, the position of a restoration margin

areas of the gingiva: supragingival, iuxtagingival, or

was thought to be the cause of periodontal lesions

intracrevicular.

and other problems, but today the influence of the ..

Fig 6-1 Healthy periodontium is indispensable for successful gingival retraction. figs 6-2 and 6-3 Gingival margin with natural dentition !at 24 x and 50 X magnification). Figs 6-4 and 6-5 Periodontal probing and analysis of the keratinized tissue help to classify the gingival biotype and to ensure stability and integrity of the restoration margin over lime.

CHAPTER

6

Technical Considerations for Soft Tissue Retraction

. position is regarded as secondary. As Richter-Snapp

Analyzing the dento g i n g ival complex

et al J concluded, "the adaptation, the precision, and the quality of the restoration margin can be of

The term biologic width was coined in 1962,4 but the

greater significance in terms of gingival health. than

first studies to measure its components were com·

the position of the margin itself."

pleted by Gargiulo et aJS in 1961 and taken up 20

Today, margin positioning is influenced to a large

years later by Dragoo and Williams 6·7 These re­

extent by patients' demand for esthetics. Clinicians

searchers established the mean dimensions of peri·

execute intracrevicular margins for maxillary and man·

odontal tissue as follows: gingival sulcus. o.69 mm;

dlbular anterior segments and sometimes for restora­

junctional epithelium. 0.97 mm; and connective tis·

tions as distal as second premolars. while juxtagin­

sue. 1.07 mm. The mean dimension of the biologic

glval margins are reserved for the lingual surfaces of

width is 2.04 mm (0.97

all prepared teeth. However, when finalizing a pros·

ions diverge, most clinicians agree that biologic

thesis for a patient who has been treated for ad·

width is an inviolable gingival limit.

+

Polemics continue. however, over which gingival

gival recession. practical considerations outweigh

components are included in the biologic width and

esthetics. and the margins must be positioned supra·

their mean dimensions. Vacek et ai8 conducted a study

When the patient has insufficient keratinized tis­

FIG 6-7

FIG 6-8

FIG 6-9

1.07 mm). Although opin·

vanced periodontal disease or has considerable gin·

gingivally.

FIG 6-6

of 10 cadaveric arches to measure the connective tis­ sue. the epithelium. and the related loss and depth

sue. and related complications prohibit surgery, the

of the sulcus. Their results showed that the connec·

clinician must alter the finish line design. By working

tive tissue had a mean thickness of o.n

at the buccal aspect with a 90-degree rounded shout·

t h e junctional epithelium. 1 . 1 4

+

:

0.32 m m ;

0-49 mm; a n d t h e

der or a modified chamfer preparation. the clinician

gingival sulcus. 1 . 3 4

can complete the restoration with a collarless pros·

the biologic width is often intruded upon. especially

thesis (Fig 6-10). When a patient requires intracrevic­

in the interproximal and buccal areas. and less fre·

ular margins, the clinician should be able to deter­

quently in the palatal region, whether by mistake or

+

o.84 mm. I n daily practice,

mine its feasibility during the diagnostic stage by

due to carelessness. Violation of the biologic width

classifying the periodontal biotype and evaluating the

generally causes inflammation of the circular fibers.

clinical situation (Figs 6-u to 6-14).

even in areas not adjacent to the site of damage.

..

Fig 6-6 Absence of kerati � ized tiss � e around a � andibular right canine. � n this case. intrasulcular positioning of the finish l1ne is impossi­ . ble. F1gs 6 - 7to 6-9 Analysis of kerat1n1zed tissue 1n a pat10nt With a ceramic crown on the mmllary right central incisor. The periodontal bio­ type is thick. wh1ch is evident under high magnification and espemlly in a lateral v1ew.

171

m

CHAPTER

6

Technical Considerations for Soft Tissue Retraction

. position is regarded as secondary. As Richter-Snapp

Analyzing the dento g i n g ival complex

et al J concluded, "the adaptation, the precision, and the quality of the restoration margin can be of

The term biologic width was coined in 1962,4 but the

greater significance in terms of gingival health. than

first studies to measure its components were com·

the position of the margin itself."

pleted by Gargiulo et aJS in 1961 and taken up 20

Today, margin positioning is influenced to a large

years later by Dragoo and Williams 6·7 These re­

extent by patients' demand for esthetics. Clinicians

searchers established the mean dimensions of peri·

execute intracrevicular margins for maxillary and man·

odontal tissue as follows: gingival sulcus. o.69 mm;

dlbular anterior segments and sometimes for restora­

junctional epithelium. 0.97 mm; and connective tis·

tions as distal as second premolars. while juxtagin­

sue. 1.07 mm. The mean dimension of the biologic

glval margins are reserved for the lingual surfaces of

width is 2.04 mm (0.97

all prepared teeth. However, when finalizing a pros·

ions diverge, most clinicians agree that biologic

thesis for a patient who has been treated for ad·

width is an inviolable gingival limit.

+

Polemics continue. however, over which gingival

gival recession. practical considerations outweigh

components are included in the biologic width and

esthetics. and the margins must be positioned supra·

their mean dimensions. Vacek et ai8 conducted a study

When the patient has insufficient keratinized tis­

FIG 6-7

FIG 6-8

FIG 6-9

1.07 mm). Although opin·

vanced periodontal disease or has considerable gin·

gingivally.

FIG 6-6

of 10 cadaveric arches to measure the connective tis­ sue. the epithelium. and the related loss and depth

sue. and related complications prohibit surgery, the

of the sulcus. Their results showed that the connec·

clinician must alter the finish line design. By working

tive tissue had a mean thickness of o.n

at the buccal aspect with a 90-degree rounded shout·

t h e junctional epithelium. 1 . 1 4

+

:

0.32 m m ;

0-49 mm; a n d t h e

der or a modified chamfer preparation. the clinician

gingival sulcus. 1 . 3 4

can complete the restoration with a collarless pros·

the biologic width is often intruded upon. especially

thesis (Fig 6-10). When a patient requires intracrevic­

in the interproximal and buccal areas. and less fre·

ular margins, the clinician should be able to deter­

quently in the palatal region, whether by mistake or

+

o.84 mm. I n daily practice,

mine its feasibility during the diagnostic stage by

due to carelessness. Violation of the biologic width

classifying the periodontal biotype and evaluating the

generally causes inflammation of the circular fibers.

clinical situation (Figs 6-u to 6-14).

even in areas not adjacent to the site of damage.

..

Fig 6-6 Absence of kerati � ized tiss � e around a � andibular right canine. � n this case. intrasulcular positioning of the finish l1ne is impossi­ . ble. F1gs 6 - 7to 6-9 Analysis of kerat1n1zed tissue 1n a pat10nt With a ceramic crown on the mmllary right central incisor. The periodontal bio­ type is thick. wh1ch is evident under high magnification and espemlly in a lateral v1ew.

171

m

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

..

An article by Kois9 has become a standard refer­

In a study by Tarnow et al.'0 the finish lines in two

ence for the study and analysis of the relationship be­

patients were positioned halfway between the bone

tween the bone crest and the gingival margin. Kois's

crest and the gingival margin. The researchers noted

bone-sounding technique involves anesthetizing a

gingival recession ranging between 0-4 and 1.2 mm

gingival area before inserting a thin periodontal probe

after 2 weeks and 1.2 mm or more after 8 weeks.

to the bone crest. The buccal and interproximal mea­

These results demonstrate histologically that reces­

surements thus obtained define the ridge type and

sion phenomena were activated in the first 7 days;

its relationship to the gingiva. This procedure has

the junctional epithelium and connective tissue then

been used to distinguish three types of gingiva-bone

re-formed apical to the finish line. This study indi­

crest structure.9 A normal crest, found in 85% of

cates that the natural mechanisms that repair inva­

patients, is defined as having probing depths of

sive damage to the biologic width result in gingival

3 mm in buccal areas and 4-5 mm in interproximal

recession, with all or its obvious functional and

areas. A high crest. found in 2% of patients, has

esthetic drawbacks.

probing depths of less than 3 mm in both the buccal

Although they never use the bone-sounding tech­

and interproximal areas. A /ow crest, present in 13%

nique, the authors of this text adhere to the Kois

of patients, has probing depths of greater than 3 mm

classification9 of ridge type. By analyzing the clinical

in the buccal area and greater than 5 mm in the inter­

results or normal periodontal probing, intraoral radio­

proximal regions.

graphs, and clinical examination, a clinician can detect

Different gingiva-bone crest structures require dif­

many conditions, including gingival recession, insufi­

ferent approaches to gingival retraction. With a high

cient keratinized gingiva, incomplete tooth eruption,

ridge, the clinician will have difficulty inserting retrac­

and edentulous areas. Depending on the patient

tion cords and runs the risk of intruding on the bio­

ridge type, the authors adopt different materials and

logic width. With a low ridge and unstable periodon­

techniques. whenever possible, to perform periodon­

tal tissue, gingival retraction can lead to gingival

tal interventions aimed at restoring the proper bio­

recession (Figs 6-15 and 6-16).

logic width so as to allow for intracrevicular margins" (Figs 6-17 to 6-30).

Fig 6-10 Collarless metal-ceramic crown. This restoration technique is often proposed in cases in which gingival tissue is lack1ng and the restoration margin must be positioned supra- or juxtagingivally.

.

6- 1 3

Figs 6-11 o 6- 14 Details of a restoratiOn !Figs 6 - l l and 6-121 and a natural tooth !Figs 6-13 and 6-141 1profile views were pho­ _ _ tographed Without a flash). The anatomy of the g•ng1val sulcus and its relationship with the restoration is evident. Note the appearance of the sulcus under the stereomicroscope. as well as the emergence profile of the crown and tooth. The frontal v11ws illustrate the health of the gingival tissue for each.

171 179

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

..

An article by Kois9 has become a standard refer­

In a study by Tarnow et al.'0 the finish lines in two

ence for the study and analysis of the relationship be­

patients were positioned halfway between the bone

tween the bone crest and the gingival margin. Kois's

crest and the gingival margin. The researchers noted

bone-sounding technique involves anesthetizing a

gingival recession ranging between 0-4 and 1.2 mm

gingival area before inserting a thin periodontal probe

after 2 weeks and 1.2 mm or more after 8 weeks.

to the bone crest. The buccal and interproximal mea­

These results demonstrate histologically that reces­

surements thus obtained define the ridge type and

sion phenomena were activated in the first 7 days;

its relationship to the gingiva. This procedure has

the junctional epithelium and connective tissue then

been used to distinguish three types of gingiva-bone

re-formed apical to the finish line. This study indi­

crest structure.9 A normal crest, found in 85% of

cates that the natural mechanisms that repair inva­

patients, is defined as having probing depths of

sive damage to the biologic width result in gingival

3 mm in buccal areas and 4-5 mm in interproximal

recession, with all or its obvious functional and

areas. A high crest. found in 2% of patients, has

esthetic drawbacks.

probing depths of less than 3 mm in both the buccal

Although they never use the bone-sounding tech­

and interproximal areas. A /ow crest, present in 13%

nique, the authors of this text adhere to the Kois

of patients, has probing depths of greater than 3 mm

classification9 of ridge type. By analyzing the clinical

in the buccal area and greater than 5 mm in the inter­

results or normal periodontal probing, intraoral radio­

proximal regions.

graphs, and clinical examination, a clinician can detect

Different gingiva-bone crest structures require dif­

many conditions, including gingival recession, insufi­

ferent approaches to gingival retraction. With a high

cient keratinized gingiva, incomplete tooth eruption,

ridge, the clinician will have difficulty inserting retrac­

and edentulous areas. Depending on the patient

tion cords and runs the risk of intruding on the bio­

ridge type, the authors adopt different materials and

logic width. With a low ridge and unstable periodon­

techniques. whenever possible, to perform periodon­

tal tissue, gingival retraction can lead to gingival

tal interventions aimed at restoring the proper bio­

recession (Figs 6-15 and 6-16).

logic width so as to allow for intracrevicular margins" (Figs 6-17 to 6-30).

Fig 6-10 Collarless metal-ceramic crown. This restoration technique is often proposed in cases in which gingival tissue is lack1ng and the restoration margin must be positioned supra- or juxtagingivally.

.

6- 1 3

Figs 6-11 o 6- 14 Details of a restoratiOn !Figs 6 - l l and 6-121 and a natural tooth !Figs 6-13 and 6-141 1profile views were pho­ _ _ tographed Without a flash). The anatomy of the g•ng1val sulcus and its relationship with the restoration is evident. Note the appearance of the sulcus under the stereomicroscope. as well as the emergence profile of the crown and tooth. The frontal v11ws illustrate the health of the gingival tissue for each.

171 179

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

E V A L U AT I O N

0 F

P E R I O D O N TA L

B I OT Y P E

F1gs 6-lSand6-l6 Gingival recession w1th metal-ceramic restorations resulting from improper treatment of the gingiva.

lG

Fig 6·17 Prov1s1onal restoration in place after removal of the metal-ceramic crowns The dental techniciiR created leteral 1nd untral incisors with different shapes to accommodate uneven gingival contours. resulting in a lack of harmony and an unnatural appnrance. Fig 6-18 Residual tooth structure. Restoral1on w1ll require periodontal surgery. involving clinical crown lengthening 1nd formation of the cor­ rect bone and gingival contours F1gs 6-19 o 6-11 Surgical crown lengthening A gingival flap was made with 1 paramarginal incision and repositioned at the level of the bone crest. us1ng the measunng lip of a bur i H207 314 012. Komet). Two notches are made to mark the dis­ tance created between the bone crest and the finish line Figs 6-22 and 6-13 Mattress-style vertical sutures anchored to the periosteu m .

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

E V A L U AT I O N

0 F

P E R I O D O N TA L

B I OT Y P E

F1gs 6-lSand6-l6 Gingival recession w1th metal-ceramic restorations resulting from improper treatment of the gingiva.

lG

Fig 6·17 Prov1s1onal restoration in place after removal of the metal-ceramic crowns The dental techniciiR created leteral 1nd untral incisors with different shapes to accommodate uneven gingival contours. resulting in a lack of harmony and an unnatural appnrance. Fig 6-18 Residual tooth structure. Restoral1on w1ll require periodontal surgery. involving clinical crown lengthening 1nd formation of the cor­ rect bone and gingival contours F1gs 6-19 o 6-11 Surgical crown lengthening A gingival flap was made with 1 paramarginal incision and repositioned at the level of the bone crest. us1ng the measunng lip of a bur i H207 314 012. Komet). Two notches are made to mark the dis­ tance created between the bone crest and the finish line Figs 6-22 and 6-13 Mattress-style vertical sutures anchored to the periosteu m .

[l· I Technical Considerations for Soft Tissue Retraction

Figs 6-24 and 6-25 Clinical case presenting with four metal-ceramic crowns lhal are incongruous in form and gingival contour. The palienl sought a new restoration because of significant gingival recession of I he central and lateral incisors. Figs 6-26 and 6-27 Presurgical views show1ng lhe residual Ieeth before and after loolh whitening with the walking bleach procedure. using sodium perborale and hydrogen peroxide.

112

Figs 6-28 and 6-2g Surgical stage with an apically positioned gingival flap. The views show lhe new contours of remodeled bone and lhe treat­ ment to lhe palatal area. Fig 6-30 Cornick"s - baslinf sutures.

18J

[l· I Technical Considerations for Soft Tissue Retraction

Figs 6-24 and 6-25 Clinical case presenting with four metal-ceramic crowns lhal are incongruous in form and gingival contour. The palienl sought a new restoration because of significant gingival recession of I he central and lateral incisors. Figs 6-26 and 6-27 Presurgical views show1ng lhe residual Ieeth before and after loolh whitening with the walking bleach procedure. using sodium perborale and hydrogen peroxide.

112

Figs 6-28 and 6-2g Surgical stage with an apically positioned gingival flap. The views show lhe new contours of remodeled bone and lhe treat­ ment to lhe palatal area. Fig 6-30 Cornick"s - baslinf sutures.

18J

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

.. G I N G IVAL RETRACTION

minum sulfate, and ferrous sulfate and their various combinations (Fig 6·38 to 6·40).

T h e need t o retract gingiva for taking impressions i s

Surgical techniques involve rotary curettage or

universally acknowledged, »-t4 although clinicians

electrosurgery to remove the epithelial layer of the

disagree as to technique. The complexity of the pro·

sulcular tissue.

cedure arises from a need to provide adequate hor· izontal space for the impression materials. Laufer et

periodontal tissue that has not been damaged or innamed during tooth preparation. The selection of

0.2

and 0-4 mm, so that when the re·

horizontal displacement and a significant undercut 6-3 1

a retraction technique depends on the operator's ex·

traction cord is removed, the clinician can compen·

perience, the periodontal biotype, and, in the authors'

sate for the substantial undercut of the final prepa­

view, the principle of choosing the least invasive

ration (Figs 6-31 to 6·34). Gingival retraction during

technique that will produce the most effective re·

any stage of restoration, no matter the technique,

suits. Based on these criteria, mechanical or mechan·

may cause a lesion to form on the periodontal tis·

icochemical methods can be used, but surgery,

sue.'6 Periodontal tissue with normal healing capac·

whether with a rotating instrument or electric scalpel,

ity will repair itself.'7-'B

exists between a m i n i mum

The use of any retraction system requires healthy

at'S have determined that the horizontal space must be between

A di rect relationship usually

should not be considered because of the clinical dif· ficulties and the uncertainty of outcome.

Gingival retraction techniques

Gingival retraction is divided into two stages, namely vertical and horizontal. During vertical de·

Techniques for gingival retraction are traditionally

nection, the clinician can position and complete the

classiied as mechanical, mechanicochemical, and sur·

finish line, while horizontal denection facilitates im·

gicat. Mechanical techniques are manifold and in·

pression taking and the subsequent removal of the

elude the use of silk or cotton cords, silicone-based

impression material.

substances, copper rings, and compressive displace·

Traditionally, these two stages are accomplished

ment.'9 These techniques are sometimes insuficient

through the use of a double retraction cord," along

for obtaining the required retraction for refining prep­

with a small-diameter thread to create vertical dis·

arations and taking impressions 20 In the authors'

placement as well as a larger- diameter thread for

view, some of these methods can even be harmful

horizontal denection. The larger-diameter thread is

(Figs 6·35 to 6-37).

removed immediately before the application of the

Mechanicochemical techniques combine mechan·

impression materials, whereas the small-diameter

ical and chemical interventions. The term often refers

thread remains i n place during the impression. Clini­

to the use of retraction cords impregnated with solu·

cians must understand the characteristics of diferent

tions that have hemostatic or vasoconstricting

retraction cords and their compatibility with the

effects, such as epinephrine, aluminum chloride, alu·

impression materials.

Fig 6-31 Design far intact tooth structure beyond the finish line. which represents the largest undercut possible. in relation to the quantity of material needed for the impression because of the need to keep horizontal retraction to a minimum and thus make the positioning of the marg1n reliable. Much also depends on the type of tooth being prepared. because a triangular tooth that tapers toward the root w1ll have greater undercut than a square tooth with a very large root. Figs 6-32 and 6-33 Tooth prepared for a ceramic complete crown The limited space between the epithelium and the finish line can be seen. In this sit­ uation it would be futile to allempt to take an impress1on without a retraction cord in place. Fig 6-4 Silvered master cast _ and the area reveals the f1n1sh line of 1ntact tooth structure beyond it. 14

..

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

.. G I N G IVAL RETRACTION

minum sulfate, and ferrous sulfate and their various combinations (Fig 6·38 to 6·40).

T h e need t o retract gingiva for taking impressions i s

Surgical techniques involve rotary curettage or

universally acknowledged, »-t4 although clinicians

electrosurgery to remove the epithelial layer of the

disagree as to technique. The complexity of the pro·

sulcular tissue.

cedure arises from a need to provide adequate hor· izontal space for the impression materials. Laufer et

periodontal tissue that has not been damaged or innamed during tooth preparation. The selection of

0.2

and 0-4 mm, so that when the re·

horizontal displacement and a significant undercut 6-3 1

a retraction technique depends on the operator's ex·

traction cord is removed, the clinician can compen·

perience, the periodontal biotype, and, in the authors'

sate for the substantial undercut of the final prepa­

view, the principle of choosing the least invasive

ration (Figs 6-31 to 6·34). Gingival retraction during

technique that will produce the most effective re·

any stage of restoration, no matter the technique,

suits. Based on these criteria, mechanical or mechan·

may cause a lesion to form on the periodontal tis·

icochemical methods can be used, but surgery,

sue.'6 Periodontal tissue with normal healing capac·

whether with a rotating instrument or electric scalpel,

ity will repair itself.'7-'B

exists between a m i n i mum

The use of any retraction system requires healthy

at'S have determined that the horizontal space must be between

A di rect relationship usually

should not be considered because of the clinical dif· ficulties and the uncertainty of outcome.

Gingival retraction techniques

Gingival retraction is divided into two stages, namely vertical and horizontal. During vertical de·

Techniques for gingival retraction are traditionally

nection, the clinician can position and complete the

classiied as mechanical, mechanicochemical, and sur·

finish line, while horizontal denection facilitates im·

gicat. Mechanical techniques are manifold and in·

pression taking and the subsequent removal of the

elude the use of silk or cotton cords, silicone-based

impression material.

substances, copper rings, and compressive displace·

Traditionally, these two stages are accomplished

ment.'9 These techniques are sometimes insuficient

through the use of a double retraction cord," along

for obtaining the required retraction for refining prep­

with a small-diameter thread to create vertical dis·

arations and taking impressions 20 In the authors'

placement as well as a larger- diameter thread for

view, some of these methods can even be harmful

horizontal denection. The larger-diameter thread is

(Figs 6·35 to 6-37).

removed immediately before the application of the

Mechanicochemical techniques combine mechan·

impression materials, whereas the small-diameter

ical and chemical interventions. The term often refers

thread remains i n place during the impression. Clini­

to the use of retraction cords impregnated with solu·

cians must understand the characteristics of diferent

tions that have hemostatic or vasoconstricting

retraction cords and their compatibility with the

effects, such as epinephrine, aluminum chloride, alu·

impression materials.

Fig 6-31 Design far intact tooth structure beyond the finish line. which represents the largest undercut possible. in relation to the quantity of material needed for the impression because of the need to keep horizontal retraction to a minimum and thus make the positioning of the marg1n reliable. Much also depends on the type of tooth being prepared. because a triangular tooth that tapers toward the root w1ll have greater undercut than a square tooth with a very large root. Figs 6-32 and 6-33 Tooth prepared for a ceramic complete crown The limited space between the epithelium and the finish line can be seen. In this sit­ uation it would be futile to allempt to take an impress1on without a retraction cord in place. Fig 6-4 Silvered master cast _ and the area reveals the f1n1sh line of 1ntact tooth structure beyond it. 14

..

chnical Considerations for Soft Tissue Retraction

f1g a 3S N1tural preparad tooth follow�ng removal of th1 frtcturod porcol11n lam1nato Yeneer

f1g a 3a Following proper ra-propor1t1on of th1 tooth, 1 non impregnated silk cord 11 pos11ioned 1n tho sulcus for m1n1mal vertical deflection r1g 8-7 In 1n occluul vltw the cord c1nnot be sun around th1 1nt1r1 buccal aspect, a 11gn of insuff1c1enl deflection

Figs 6-39 and 6-0 Cementation phase of the restoratiOn, w1th the veneer 1n place after removal of rubber dam Note the perfect volumetm pro­ portiOns and the marginal adaptatiOn

f1g & 31 S1m1 tooth 1fler the non1mpregn1ted 11lk cord hu bun removed and repl1ced w1th a br11ded cord Impregnated w1th alum1num sui­ fall, providing grntor vert1c1l and homontal g1ng1v11 defl1clion

Ill

117

chnical Considerations for Soft Tissue Retraction

f1g a 3S N1tural preparad tooth follow�ng removal of th1 frtcturod porcol11n lam1nato Yeneer

f1g a 3a Following proper ra-propor1t1on of th1 tooth, 1 non impregnated silk cord 11 pos11ioned 1n tho sulcus for m1n1mal vertical deflection r1g 8-7 In 1n occluul vltw the cord c1nnot be sun around th1 1nt1r1 buccal aspect, a 11gn of insuff1c1enl deflection

Figs 6-39 and 6-0 Cementation phase of the restoratiOn, w1th the veneer 1n place after removal of rubber dam Note the perfect volumetm pro­ portiOns and the marginal adaptatiOn

f1g & 31 S1m1 tooth 1fler the non1mpregn1ted 11lk cord hu bun removed and repl1ced w1th a br11ded cord Impregnated w1th alum1num sui­ fall, providing grntor vert1c1l and homontal g1ng1v11 defl1clion

Ill

117

CHAPTER 6 Technical Considerations for Sot Tissue Retraction

.. Retraction cords

break, hold the chemical solutions 2.5 times longer than other kinds of cords, and do not get tangled in

In prosthodontics, retraction cords are the most

rotating diamond burs during preparation. However,

common method used to displace tissue for impres·

they are easily cut during preparation and, because

sion taking, and many different types of cords and

they are more easily compressed, offer less gingival

chemical solutions are available (Fig 6·41). Most

retraction.

cords are made of various textile blends of wool, silk, cotton, and synthetic fibers, which are twisted, braided, or knitted together'9 (Fig 6-42). Cords also can be distinguished as either soft or compact. Sot

For mechanicochemical techniques, retraction cords

cords are easy to position and have a high capacity

are i mpregnated with chemical solutions that aug­

for absorbing gingival fluids or chemical solutions,

ment the effect of retraction and hemostasis. How­

but they can break easily during positioning and

ever, animal studies using dogs21 have shown that

removal and disintegrate when in contact with re·

chemical solutions cause a certain amount of inflam­

traction fluids. Compact cords provide better hori·

mation of the connective tissue. Among the most

zontal displacement, exhibit minimal degeneration

frequently used solutions are epinephrine; various

from retraction fluids, and are less prone to break­

astringents, such as aluminum chloride, aluminum

ing, but they are difficult to position and absorb min­

sulfate, and ferrous sulfate; and combinations of

imal gingival or retraction luids.

these compounds.22

Twisted cords are the oldest type of cord used

Epinephrine is frequently used because it offers

in dentistry; these are composed of two or three

excellent vasoconstriction, provides considerable tis­

threads twisted together. Twisted cords are easy to

sue retraction, and results in minimal postoperative

insert, and larger cords can be separated into two

tissue loss.'B One study,'J however, found no signif­

smaller ones. However, the threads come apart eas­

icant difference compared with aluminum sulfate.

ily during positioning and can get tangled in the

Epinephrine should never be used in patients whose

rotating bur during preparation. The braided cords are woven so tightly that it is

Fig 6-41 Different types of retraction cord. There are many types of cords and Impregnating substances.

Fig 6-42 Basic types ol retraction cord: (left to righ) braided. twisted. and knitted.

Fig 6-43 Result of taking an impression after using a retraction cord impregnated with aluminum chloride. The impression material. in this case polyether. cannot polymerize correctly in the presence of aluminum chloride. The same situation applies to aluminum sulfate and polyvinyl siloxane.

gingiva has been damaged during preparation or for patients with hyperthyroid conditions, cardiovascular

impossible to separate the threads. These cords are

pathologies, or hypersensitivity. The latter conditions

vey stable, remain intact during positioning, do not

may lead to cardiovascular reactions, such as an

get tangled or torn by rotating diamond burs, and

i ncrease in blood pressure, tachycardia, accelerated

come in two varieties: solid core and hollow core.

respiration, or headache.

. However, it can be used on damaged tissues with only moderate tissue loss after healing. The impregnating solutions can inhibit the poly­

necessary to carefully clean the surfa ce of the cord with cotton pellets and water spray to reduce or eliminate the polymerization interference.

merization of impression material when they come in

Aluminum sulate ofers good gingival retraction

and eicient working time. Some authors27 believe

Cords with a solid core exhibit greater volume and

Aluminum chloride is a commonly used astringent

contact; a similar phenomena has been found when

more horizontal retraction, but they are stiffer and

that causes no adverse systemic effects and only a

latex gloves are used with polyvinyl siloxanes.'6

this chemical is toxic to tissues and, because of the

more difficult to inset. Cords with hollow cores have

few undesired localized effects. 24 It is usually found

Aluminum chloride is compatible with polyvinyl silox­

sulfur, can interfere with the polymerization of poly­

anes, but it inhibits the reaction of the polyether

greater flexibility and are easier to position, but they

marketed as a 14% solution. The hemostasis and

are less voluminous and exhibit less horizontal dis­

retraction that are provided by aluminum chloride

placement. The knitted cords are knitted together without a central thread. They are easily compressed, do not

11

I m pregnating chem icals

vinyl siloxanes'8 i f the cord is not rinsed thoroughly

chains, and if they remain in contact, the impression

before impression. On the other hand, aluminum sul­

are inferior to those of epinephrine; moreover, if

material loses its contours and detail and will appear

fate shows excellent compatibility with polyethers in

used at high concentrations, this chemical can cause

melted (Fig 6-43). Many clinicians continue to use

general, and it is recommended for use with these

significant postoperative paramarginal tissue loss.'S .

aluminum chloride as a hemostatic agent, making it

impression materials.

..

CHAPTER 6 Technical Considerations for Sot Tissue Retraction

.. Retraction cords

break, hold the chemical solutions 2.5 times longer than other kinds of cords, and do not get tangled in

In prosthodontics, retraction cords are the most

rotating diamond burs during preparation. However,

common method used to displace tissue for impres·

they are easily cut during preparation and, because

sion taking, and many different types of cords and

they are more easily compressed, offer less gingival

chemical solutions are available (Fig 6·41). Most

retraction.

cords are made of various textile blends of wool, silk, cotton, and synthetic fibers, which are twisted, braided, or knitted together'9 (Fig 6-42). Cords also can be distinguished as either soft or compact. Sot

For mechanicochemical techniques, retraction cords

cords are easy to position and have a high capacity

are i mpregnated with chemical solutions that aug­

for absorbing gingival fluids or chemical solutions,

ment the effect of retraction and hemostasis. How­

but they can break easily during positioning and

ever, animal studies using dogs21 have shown that

removal and disintegrate when in contact with re·

chemical solutions cause a certain amount of inflam­

traction fluids. Compact cords provide better hori·

mation of the connective tissue. Among the most

zontal displacement, exhibit minimal degeneration

frequently used solutions are epinephrine; various

from retraction fluids, and are less prone to break­

astringents, such as aluminum chloride, aluminum

ing, but they are difficult to position and absorb min­

sulfate, and ferrous sulfate; and combinations of

imal gingival or retraction luids.

these compounds.22

Twisted cords are the oldest type of cord used

Epinephrine is frequently used because it offers

in dentistry; these are composed of two or three

excellent vasoconstriction, provides considerable tis­

threads twisted together. Twisted cords are easy to

sue retraction, and results in minimal postoperative

insert, and larger cords can be separated into two

tissue loss.'B One study,'J however, found no signif­

smaller ones. However, the threads come apart eas­

icant difference compared with aluminum sulfate.

ily during positioning and can get tangled in the

Epinephrine should never be used in patients whose

rotating bur during preparation. The braided cords are woven so tightly that it is

Fig 6-41 Different types of retraction cord. There are many types of cords and Impregnating substances.

Fig 6-42 Basic types ol retraction cord: (left to righ) braided. twisted. and knitted.

Fig 6-43 Result of taking an impression after using a retraction cord impregnated with aluminum chloride. The impression material. in this case polyether. cannot polymerize correctly in the presence of aluminum chloride. The same situation applies to aluminum sulfate and polyvinyl siloxane.

gingiva has been damaged during preparation or for patients with hyperthyroid conditions, cardiovascular

impossible to separate the threads. These cords are

pathologies, or hypersensitivity. The latter conditions

vey stable, remain intact during positioning, do not

may lead to cardiovascular reactions, such as an

get tangled or torn by rotating diamond burs, and

i ncrease in blood pressure, tachycardia, accelerated

come in two varieties: solid core and hollow core.

respiration, or headache.

. However, it can be used on damaged tissues with only moderate tissue loss after healing. The impregnating solutions can inhibit the poly­

necessary to carefully clean the surfa ce of the cord with cotton pellets and water spray to reduce or eliminate the polymerization interference.

merization of impression material when they come in

Aluminum sulate ofers good gingival retraction

and eicient working time. Some authors27 believe

Cords with a solid core exhibit greater volume and

Aluminum chloride is a commonly used astringent

contact; a similar phenomena has been found when

more horizontal retraction, but they are stiffer and

that causes no adverse systemic effects and only a

latex gloves are used with polyvinyl siloxanes.'6

this chemical is toxic to tissues and, because of the

more difficult to inset. Cords with hollow cores have

few undesired localized effects. 24 It is usually found

Aluminum chloride is compatible with polyvinyl silox­

sulfur, can interfere with the polymerization of poly­

anes, but it inhibits the reaction of the polyether

greater flexibility and are easier to position, but they

marketed as a 14% solution. The hemostasis and

are less voluminous and exhibit less horizontal dis­

retraction that are provided by aluminum chloride

placement. The knitted cords are knitted together without a central thread. They are easily compressed, do not

11

I m pregnating chem icals

vinyl siloxanes'8 i f the cord is not rinsed thoroughly

chains, and if they remain in contact, the impression

before impression. On the other hand, aluminum sul­

are inferior to those of epinephrine; moreover, if

material loses its contours and detail and will appear

fate shows excellent compatibility with polyethers in

used at high concentrations, this chemical can cause

melted (Fig 6-43). Many clinicians continue to use

general, and it is recommended for use with these

significant postoperative paramarginal tissue loss.'S .

aluminum chloride as a hemostatic agent, making it

impression materials.

..

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

.

Ferrous sulfate is commonly used as an astrin­

ment with a thickness to suit the cord type (twisted,

gent because of its excellent hemostasis and negli­

braided, or knitted). In the authors' view, cord place­

gible tissue loss. However, this chemical provides

ment can be accomplished using a composite spat­

minimal retraction and stains the gingival tissues.

ula or other tool and does not require the purchase

The precipitate that forms on the cord is difficult to

of expensive, specially designed instruments.

eliminate before taking impressions, and since fer­

Using an instrument compatible with the cord

rous sulfate is incompatible with polyethers, clini­

type, the clinician begins by gently inseting the cord

cians must use hydrocolloidal impression material.

in the interproximal zone. The greater quantity of

In the authors' view, the use of this chemical and its

gingival tissue found in the interproximal zone

associated impression technique are obsolete. Various combinations of astringents can also be

makes it more favorable than the buccal area for starting cord placement. The cord is inserted using

used for retraction. The combination of aluminum

a single spatula or two spatulas at the same time

sulfate and aluminum chloride seems to provide bet­

(the bimanual technique) (Figs 6-44 to 6-47). The

ter results than either of the two used in combina­

clinician must not push too hard, as this could result

tion with epinephrine.

in placing the cord too deep. After the first part of the cord is positioned, the clinician must work along

R ETRACTION PROCEDURES Mechanical a n d mechanicochemical techniq ues

the buccal zone. toward the initial point of insertion. If the clinician begins working away from the initial point of insertion, the portion of the cord already in place tends to shift (Fig 6-48). After inserting the cord along the buccal zone, the ends should be

Although the cord-positioning procedure is the same

inserted in the palatal area, where overlaps are bet­

regardless of cord type or technique, retraction cords

ter tolerated.

can be used in single-cord, selective double-cord, or double-cord approaches. The single-cord technique generally requires a

Some authors29 recommend that. when using the single-cord technique, the cord be removed immedi­ ately before taking the impression. This technique,

cord of the smallest diameter (no. ooo or oo). For

however, should be avoided, because once the cord

cord insertion, the clinician uses a manual instru-

is removed, the sulcus tends to close immediately, .

Figs 6-4 and 6-45 Placement of retraction cord, preVIOusly cut to the size of the tooth. Insertion beg�ns '" the �nterprox1mal area and leaves the two loose ends to be overlapped '" the palatal area.

Fig 6-46 Bimanual technique. The cliniCian may use two Instruments simultaneously. one to hold lhe retract1on cord in posi­ tion and the second to insert 1t Fig 6-47 Effects of g�ng1val retraction. Before insert1on of the retraction cord. the finiSh l1ne was at the same level as the gin­ gival marg1n

X 6-4BA

6-488

Fig 6-48 insertlon technique Working away from the initial po1nt of Insertion /a) i s ineffective The cliniCian must work toward the IRII1al po1nt of insert1on fbi. starling at a po1nt a good diStance from the Initial point

110

lfl

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

.

Ferrous sulfate is commonly used as an astrin­

ment with a thickness to suit the cord type (twisted,

gent because of its excellent hemostasis and negli­

braided, or knitted). In the authors' view, cord place­

gible tissue loss. However, this chemical provides

ment can be accomplished using a composite spat­

minimal retraction and stains the gingival tissues.

ula or other tool and does not require the purchase

The precipitate that forms on the cord is difficult to

of expensive, specially designed instruments.

eliminate before taking impressions, and since fer­

Using an instrument compatible with the cord

rous sulfate is incompatible with polyethers, clini­

type, the clinician begins by gently inseting the cord

cians must use hydrocolloidal impression material.

in the interproximal zone. The greater quantity of

In the authors' view, the use of this chemical and its

gingival tissue found in the interproximal zone

associated impression technique are obsolete. Various combinations of astringents can also be

makes it more favorable than the buccal area for starting cord placement. The cord is inserted using

used for retraction. The combination of aluminum

a single spatula or two spatulas at the same time

sulfate and aluminum chloride seems to provide bet­

(the bimanual technique) (Figs 6-44 to 6-47). The

ter results than either of the two used in combina­

clinician must not push too hard, as this could result

tion with epinephrine.

in placing the cord too deep. After the first part of the cord is positioned, the clinician must work along

R ETRACTION PROCEDURES Mechanical a n d mechanicochemical techniq ues

the buccal zone. toward the initial point of insertion. If the clinician begins working away from the initial point of insertion, the portion of the cord already in place tends to shift (Fig 6-48). After inserting the cord along the buccal zone, the ends should be

Although the cord-positioning procedure is the same

inserted in the palatal area, where overlaps are bet­

regardless of cord type or technique, retraction cords

ter tolerated.

can be used in single-cord, selective double-cord, or double-cord approaches. The single-cord technique generally requires a

Some authors29 recommend that. when using the single-cord technique, the cord be removed immedi­ ately before taking the impression. This technique,

cord of the smallest diameter (no. ooo or oo). For

however, should be avoided, because once the cord

cord insertion, the clinician uses a manual instru-

is removed, the sulcus tends to close immediately, .

Figs 6-4 and 6-45 Placement of retraction cord, preVIOusly cut to the size of the tooth. Insertion beg�ns '" the �nterprox1mal area and leaves the two loose ends to be overlapped '" the palatal area.

Fig 6-46 Bimanual technique. The cliniCian may use two Instruments simultaneously. one to hold lhe retract1on cord in posi­ tion and the second to insert 1t Fig 6-47 Effects of g�ng1val retraction. Before insert1on of the retraction cord. the finiSh l1ne was at the same level as the gin­ gival marg1n

X 6-4BA

6-488

Fig 6-48 insertlon technique Working away from the initial po1nt of Insertion /a) i s ineffective The cliniCian must work toward the IRII1al po1nt of insert1on fbi. starling at a po1nt a good diStance from the Initial point

110

lfl

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

. preventing penetration of the impression material.

drawback of using a second cord is the inevitable

. deflection using a compound of kaolin and aluminum

sive contact of the electrode with the tissues even at

Cord removal also can result in bleeding. The clini­

compression and apical repositioning of the first

chloride (Expasyl, Pierre Rolland) which has a d ilat­

low frequencyB can cause high temperatures from lateral heat, which also can result in tissue necrosis.

cian must keep the cord in place throughout the

cord, which makes cord positioning difficult to con·

ing effect (Figs 6-64 to 6-66). The product comes in

operative stages, from repositioning and completing

trol and healing from the gingival displacement

convenient capsules and can be injected while it is

For this reason, researchers and m a n u facturers

the finish line to taking the impression.

unpredictable.

still malleable directly into the sulcus with a small­

have developed electrosurgery instruments that use

The cord must retract the gingiva enough to ex­

However, i n the authors' experience, a second re­

gauge syringe. Expasyl expands and hardens upon

small-diameter electrodes. These instruments, which

pose a portion of the unprepared tooth lying beyond

traction cord must never be used during tooth prepar­

contact with the fluids in the sulcus. Because of the

have a filtered current that produces less lateral

the finish line, without i nterference from the soft tis­

ation and positioning of the finish line because of

aluminum chloride, the clinician must rinse the area

heat, are more appropriately called radioscalpels and

sue. If the gingiva is not retracted suficiently, the

the serious risk of gingival recession. Thus, choosing

copiously before taking an im pression, especially if

their technique, radiosurgery. A radioscalpel works

impression material will not properly record the fin­

a technique depends on which instruments are used

polyether material is being used. Expasyl is very

with ultrahigh-frequency radio waves to make a

ish line preparation and intact tooth (Figs 6-49 to

for the finish line positioning and which impression

effective when used in combination with a single

clean cut without necrosing the gingival tissues. In

6-53).

materials are used.

The selective double-cord technique involves insert­

cord, but in the authors' opinion its use alone pro­

addition to high frequency (27 MHz) and a small­

vides insufficient retraction for taking an impression.

diameter electrode, an important distinction between

lose the points of reference, especially of the gingi­

Moreover, if Expasyl is used without a retraction

the radioscalpel and the electroscalpel concerns the

or 2) in the interproximal area directly over

val margin, always proceeding according to the stages

cord, the clinician cannot position a subgingival

absence or presence of a grounding plate; the pres­

the irst cord, to further displace the papillae (Figs

outlined in chapter 5- When using rotating instru­

restoration margin without damaging the gingiva; it

ence of a large grounding plate causes anxiety i n

6-54 to 6-6o). This method of selective horizontal

ments for primary tooth reduction, the clinician must

does not provide the same amount of space that can

some patients. For these reasons, t h e use of a radio­

displacement facilitates impression taking without

avoid accidentally touching or damaging the gingiva

be obtained by using a cord.

involving the delicate buccal tissues. The pieces of

in order to keep the tissue intact and free of bleed­

ing small pieces of cord of equal or greater diameter (no. o,

1,

cord must be removed immediately before taking the

ing. Above all, the retraction cords must be placed,

impression.

no matter how temporarily, only after the guide

The double-cord technique requires the insertion

2

During tooth preparation, the clinician must never

groove and finish line position have been defined.

scalpel (Odontosurge, Odonto-Wave) is recommended. The clinician must a lways maintain visibility of the

Surg ical tech n i q ues

cut, which can be achieved by using magnifying instru­

Sometimes, after vertical retraction with a single cord

The radioscalpel can be used only in the interproxi­

ments such as a stereomicroscope in indirect vision.

of a second cord of equal or greater diameter (no. o,

If the clinician repositions the finish line with

and the completing of the finish line with oscillating

mal and palatal areas, and never in the buccal areas

1, or 2) directly over the first cord to obtain the hor­

oscillating instruments to minimize gingival damage,

instruments, gingiva may still block access for the

(Figs 6-68 to 6-71). When it has been used to remove

izontal retraction for the entire ci rcumference of the

and if a continuous jet of water and air is used to

impression material. I n such cases, the clinician may

small bits of excess tissue, the point must be cleaned

prepared tooth1 2 ·3° (Figs 6-61 to 6-63). The second

prevent overheating, the ideal horizontal displace­

need to remove gingival tissue using a surgical tech­

after each cut, both with a gauze pad soaked in alco­ hol and with a medium-grit refinishing disk.

cord is removed just before the impression is taken,

ment can be obtained mechanically. Impression mate­

nique (Fig 6-67). The traditional surgical procedure is

while the first cord is left in place. In the first 20 sec­

rial can subsequently be injected in the sulcus with­

electrosurgery, which uses high-frequency waves to

The authors believe the radioscalpel must be

onds after cord removal, the horizontal displacement

out requiring a second retraction cord. If, after repo­

induce an electric current that cuts the gingival tis­

used only in combination with a retraction cord and

of the soft tissue is reduced by 35%, and in the sub·

sitioning and completing the finish line with round­

sue and coagulates the wounds. Most electroscalpels

is appropriate only for removing limited quantities of

sequent 20 seconds, another 18% of the displacement

ed chisels, the first retraction cord (which was posi­

have two main components: a working point that is

gingival tissue. Clinicians are strongly discouraged from using the electroscalpel or the radioscalpel as

space is lostY The speed at which the impression

tioned 0.2 or 0.3 mm apical to the finish line) is not

an electrode and a metal dispersion box to ground

material is inserted after the second retraction cord

visible, the clinician may need additional horizontal

the current with a frequency of about 3 MHz.3'

is removed is therefore critical.

displacement. Localized displacement can be accom­

The greatest d rawback to using electrosurgey is

the sole means of retraction because it is i mpossible to adequately control the depth of the cut.

Selecting a retraction technique depends on vari­

plished manually by retracting the gingival tissue

the risk of producing high temperatures. Temperature

ous clinical factors and the type of cord used. For

with the spatula used to position the cords im­

control requires using the electrical current at the

instance, the clinician would be well advised to use

mediately prior to inserting the impression material.

correct intensity; if it is too high, the electrode can

the double-cord technique for a patient with thick

When the gingiva obscures the retraction cord in

carbonize the tissue, whereas insuficient intensity

In clinical practice, diferent types of retraction cord

periodontal tissue and/or slight inflammation. The

several areas, the clinician can complete horizontal ..

will cause the tissue to adhere to the electrode. Exces-

are used depending on the periodontal biotype, the ..

A D D ITIONAL G U I D E LI N ES

193

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

. preventing penetration of the impression material.

drawback of using a second cord is the inevitable

. deflection using a compound of kaolin and aluminum

sive contact of the electrode with the tissues even at

Cord removal also can result in bleeding. The clini­

compression and apical repositioning of the first

chloride (Expasyl, Pierre Rolland) which has a d ilat­

low frequencyB can cause high temperatures from lateral heat, which also can result in tissue necrosis.

cian must keep the cord in place throughout the

cord, which makes cord positioning difficult to con·

ing effect (Figs 6-64 to 6-66). The product comes in

operative stages, from repositioning and completing

trol and healing from the gingival displacement

convenient capsules and can be injected while it is

For this reason, researchers and m a n u facturers

the finish line to taking the impression.

unpredictable.

still malleable directly into the sulcus with a small­

have developed electrosurgery instruments that use

The cord must retract the gingiva enough to ex­

However, i n the authors' experience, a second re­

gauge syringe. Expasyl expands and hardens upon

small-diameter electrodes. These instruments, which

pose a portion of the unprepared tooth lying beyond

traction cord must never be used during tooth prepar­

contact with the fluids in the sulcus. Because of the

have a filtered current that produces less lateral

the finish line, without i nterference from the soft tis­

ation and positioning of the finish line because of

aluminum chloride, the clinician must rinse the area

heat, are more appropriately called radioscalpels and

sue. If the gingiva is not retracted suficiently, the

the serious risk of gingival recession. Thus, choosing

copiously before taking an im pression, especially if

their technique, radiosurgery. A radioscalpel works

impression material will not properly record the fin­

a technique depends on which instruments are used

polyether material is being used. Expasyl is very

with ultrahigh-frequency radio waves to make a

ish line preparation and intact tooth (Figs 6-49 to

for the finish line positioning and which impression

effective when used in combination with a single

clean cut without necrosing the gingival tissues. In

6-53).

materials are used.

The selective double-cord technique involves insert­

cord, but in the authors' opinion its use alone pro­

addition to high frequency (27 MHz) and a small­

vides insufficient retraction for taking an impression.

diameter electrode, an important distinction between

lose the points of reference, especially of the gingi­

Moreover, if Expasyl is used without a retraction

the radioscalpel and the electroscalpel concerns the

or 2) in the interproximal area directly over

val margin, always proceeding according to the stages

cord, the clinician cannot position a subgingival

absence or presence of a grounding plate; the pres­

the irst cord, to further displace the papillae (Figs

outlined in chapter 5- When using rotating instru­

restoration margin without damaging the gingiva; it

ence of a large grounding plate causes anxiety i n

6-54 to 6-6o). This method of selective horizontal

ments for primary tooth reduction, the clinician must

does not provide the same amount of space that can

some patients. For these reasons, t h e use of a radio­

displacement facilitates impression taking without

avoid accidentally touching or damaging the gingiva

be obtained by using a cord.

involving the delicate buccal tissues. The pieces of

in order to keep the tissue intact and free of bleed­

ing small pieces of cord of equal or greater diameter (no. o,

1,

cord must be removed immediately before taking the

ing. Above all, the retraction cords must be placed,

impression.

no matter how temporarily, only after the guide

The double-cord technique requires the insertion

2

During tooth preparation, the clinician must never

groove and finish line position have been defined.

scalpel (Odontosurge, Odonto-Wave) is recommended. The clinician must a lways maintain visibility of the

Surg ical tech n i q ues

cut, which can be achieved by using magnifying instru­

Sometimes, after vertical retraction with a single cord

The radioscalpel can be used only in the interproxi­

ments such as a stereomicroscope in indirect vision.

of a second cord of equal or greater diameter (no. o,

If the clinician repositions the finish line with

and the completing of the finish line with oscillating

mal and palatal areas, and never in the buccal areas

1, or 2) directly over the first cord to obtain the hor­

oscillating instruments to minimize gingival damage,

instruments, gingiva may still block access for the

(Figs 6-68 to 6-71). When it has been used to remove

izontal retraction for the entire ci rcumference of the

and if a continuous jet of water and air is used to

impression material. I n such cases, the clinician may

small bits of excess tissue, the point must be cleaned

prepared tooth1 2 ·3° (Figs 6-61 to 6-63). The second

prevent overheating, the ideal horizontal displace­

need to remove gingival tissue using a surgical tech­

after each cut, both with a gauze pad soaked in alco­ hol and with a medium-grit refinishing disk.

cord is removed just before the impression is taken,

ment can be obtained mechanically. Impression mate­

nique (Fig 6-67). The traditional surgical procedure is

while the first cord is left in place. In the first 20 sec­

rial can subsequently be injected in the sulcus with­

electrosurgery, which uses high-frequency waves to

The authors believe the radioscalpel must be

onds after cord removal, the horizontal displacement

out requiring a second retraction cord. If, after repo­

induce an electric current that cuts the gingival tis­

used only in combination with a retraction cord and

of the soft tissue is reduced by 35%, and in the sub·

sitioning and completing the finish line with round­

sue and coagulates the wounds. Most electroscalpels

is appropriate only for removing limited quantities of

sequent 20 seconds, another 18% of the displacement

ed chisels, the first retraction cord (which was posi­

have two main components: a working point that is

gingival tissue. Clinicians are strongly discouraged from using the electroscalpel or the radioscalpel as

space is lostY The speed at which the impression

tioned 0.2 or 0.3 mm apical to the finish line) is not

an electrode and a metal dispersion box to ground

material is inserted after the second retraction cord

visible, the clinician may need additional horizontal

the current with a frequency of about 3 MHz.3'

is removed is therefore critical.

displacement. Localized displacement can be accom­

The greatest d rawback to using electrosurgey is

the sole means of retraction because it is i mpossible to adequately control the depth of the cut.

Selecting a retraction technique depends on vari­

plished manually by retracting the gingival tissue

the risk of producing high temperatures. Temperature

ous clinical factors and the type of cord used. For

with the spatula used to position the cords im­

control requires using the electrical current at the

instance, the clinician would be well advised to use

mediately prior to inserting the impression material.

correct intensity; if it is too high, the electrode can

the double-cord technique for a patient with thick

When the gingiva obscures the retraction cord in

carbonize the tissue, whereas insuficient intensity

In clinical practice, diferent types of retraction cord

periodontal tissue and/or slight inflammation. The

several areas, the clinician can complete horizontal ..

will cause the tissue to adhere to the electrode. Exces-

are used depending on the periodontal biotype, the ..

A D D ITIONAL G U I D E LI N ES

193

CHAPTtR 6 Technical Considerations for Soft Tissue Retraction

6-50

Figs 6-4g and 6-50 Distance between the finish line and the vertical retraction cord. a s well as the relationship with the paramarginal tissues. as viewed through the microscope.

194

Fig 6-51 In the occlusal view. the retraction cords are visible after the finish line has been completed. There is no evidence of bleeding or damaged soft tissue. Figs 6-52 and 6-53 Removal of a metal crown from a vital tooth. After the tooth has been re-prepared. the retraction cord is perfectly visible immediately before the impression is taken.

195

CHAPTtR 6 Technical Considerations for Soft Tissue Retraction

6-50

Figs 6-4g and 6-50 Distance between the finish line and the vertical retraction cord. a s well as the relationship with the paramarginal tissues. as viewed through the microscope.

194

Fig 6-51 In the occlusal view. the retraction cords are visible after the finish line has been completed. There is no evidence of bleeding or damaged soft tissue. Figs 6-52 and 6-53 Removal of a metal crown from a vital tooth. After the tooth has been re-prepared. the retraction cord is perfectly visible immediately before the impression is taken.

195

Fig 6-54 Occlusal view of a loath after a single retraction cord has been positioned. Gingiva obscures the cord around a significant part of the tooth. Figs 6-55 and 6-56 Selective double-cord technique. Portions of cord are inserted in the areas where gingiva requires additional retraction. The pieces of cord are removed immediately prior to laking lhe impression. Fig 6-57 Impression of the tooth. Figs 6-58 to 6-60 Ceramic crown with a pressed ceramic core offers high resistance. great precision. and excellent esthetics. Figs 6-61 and 6-62 Double- cord technique. Note lhe lwo loose ends provided for fast removal immediately before insertion of the impression material into the sulcus. Fig 6-63 Impression accurately records lhe finish line. The thickness of the material at the margin of the impression indi cates the horizontal displacement created by the double cords. Figs 6-64 to 6-66 Expansion material in the syringe and cartridge with single-use gauge to insert material direclly mto the sulcus. Expasyt. a combination of kaolin and aluminum chloride. provides good horizontal retraction. is slightly hemostatic. and works optimally in combination with a single vertical retraction cord. In the authors experien ce. Expasyl is useful i n cases lacking vertical retraction. such as those showing excess or slightly damaged tissue after the insertion of the first cord.

Fig 6-54 Occlusal view of a loath after a single retraction cord has been positioned. Gingiva obscures the cord around a significant part of the tooth. Figs 6-55 and 6-56 Selective double-cord technique. Portions of cord are inserted in the areas where gingiva requires additional retraction. The pieces of cord are removed immediately prior to laking lhe impression. Fig 6-57 Impression of the tooth. Figs 6-58 to 6-60 Ceramic crown with a pressed ceramic core offers high resistance. great precision. and excellent esthetics. Figs 6-61 and 6-62 Double- cord technique. Note lhe lwo loose ends provided for fast removal immediately before insertion of the impression material into the sulcus. Fig 6-63 Impression accurately records lhe finish line. The thickness of the material at the margin of the impression indi cates the horizontal displacement created by the double cords. Figs 6-64 to 6-66 Expansion material in the syringe and cartridge with single-use gauge to insert material direclly mto the sulcus. Expasyt. a combination of kaolin and aluminum chloride. provides good horizontal retraction. is slightly hemostatic. and works optimally in combination with a single vertical retraction cord. In the authors experien ce. Expasyl is useful i n cases lacking vertical retraction. such as those showing excess or slightly damaged tissue after the insertion of the first cord.

M I N I M A L

H O R I Z O N TA L

D E F L E C T I O N

Fig 6-67 Occlusal view of partially obscured retraction cords around two maxillary right t .. th after repositioning and com­ pleting the finish line. The radiosurgery technique removes minimal amounts of gingival tissue with a radioscalpel to leave the finish line visible and ready for impression material. Fig 6-68 Point of the radioscalpet used to remove excess tissue. A plastic (noncondu ctive) mirror and a medium-grit disk soaked in alcohol are also used in radiosurgery. Figs 6-69 and 6-70 Cut progression of the working point. as s"n through the stereomicroscope in indirect vision. Radiosurgery is never used on the buccal aspect of the tooth. The small tip of a high-frequency radioscalpel is very precise. and the presence of the first retraction cord helps the clinician to avoid errors of depth or direction. Fig 6-71 View of same tooth after removal of a thin band of gingival tissue that obscured the retraction cord. The sulcus shows no signs of bl .. ding after the radiosurgery. Fig 6-72 Polyether impression showing minimum thickness and height indicates that retraction was obtained using a single impregnated cord and radiosurgery.

.. various clinical stages, and the health of the gingiva.

patibility between the polyether material and the alu­

In the presence of thin periodontium that is already

m inum chloride. Horizontal displacement can be

at risk of gingival recession, the authors recommend

achieved with a second retraction cord, xpasyl, or

nonimpregnated, compact no. ooo cords (Uitrapak

radiosurgey.

Knitted Cord, Ultradent) or 2/o silk sutures for verti­

Though the literature specifies the quantity of

cal retraction. Horizontal retraction should be ob­

required horizontal displacement as o.s mm for im­ t

tained using mechanical or mechanicochemical means

pressions using elastomeric materials and

(eg, xpasyl), but in most cases the use of a second

impressions using irreversible hydrocolloids,>B these

cord should be avoided.

values are too high to be considered noninvasive.

m m for

For thick periodontium, where the risk of subse­

Modern elastomeric materials have such a high de­

quent gingival recession is minimized, a twisted no.

gree of tear strength resistance that they can record

oo cord impregnated with aluminum sulfate (Gingi­

the finish line and the intact tooth structure beyond

Aid Z-Twist), or a nonimpregnated compact no. ooo

the fi nish line using a thickness level below litera­

cord (Uitrapak) soaked in aluminum chloride (Hemo­

ture recommendations. Because hydrocolloid i mpres­

dent, Premier) can be used. If polyether impression

sion materials require invasive horizontal retraction,

material is used, the area should be rinsed copious­

the authors do not use them (Fig 6-72).

ly before the impression is taken to prevent incom-

..

M I N I M A L

H O R I Z O N TA L

D E F L E C T I O N

Fig 6-67 Occlusal view of partially obscured retraction cords around two maxillary right t .. th after repositioning and com­ pleting the finish line. The radiosurgery technique removes minimal amounts of gingival tissue with a radioscalpel to leave the finish line visible and ready for impression material. Fig 6-68 Point of the radioscalpet used to remove excess tissue. A plastic (noncondu ctive) mirror and a medium-grit disk soaked in alcohol are also used in radiosurgery. Figs 6-69 and 6-70 Cut progression of the working point. as s"n through the stereomicroscope in indirect vision. Radiosurgery is never used on the buccal aspect of the tooth. The small tip of a high-frequency radioscalpel is very precise. and the presence of the first retraction cord helps the clinician to avoid errors of depth or direction. Fig 6-71 View of same tooth after removal of a thin band of gingival tissue that obscured the retraction cord. The sulcus shows no signs of bl .. ding after the radiosurgery. Fig 6-72 Polyether impression showing minimum thickness and height indicates that retraction was obtained using a single impregnated cord and radiosurgery.

.. various clinical stages, and the health of the gingiva.

patibility between the polyether material and the alu­

In the presence of thin periodontium that is already

m inum chloride. Horizontal displacement can be

at risk of gingival recession, the authors recommend

achieved with a second retraction cord, xpasyl, or

nonimpregnated, compact no. ooo cords (Uitrapak

radiosurgey.

Knitted Cord, Ultradent) or 2/o silk sutures for verti­

Though the literature specifies the quantity of

cal retraction. Horizontal retraction should be ob­

required horizontal displacement as o.s mm for im­ t

tained using mechanical or mechanicochemical means

pressions using elastomeric materials and

(eg, xpasyl), but in most cases the use of a second

impressions using irreversible hydrocolloids,>B these

cord should be avoided.

values are too high to be considered noninvasive.

m m for

For thick periodontium, where the risk of subse­

Modern elastomeric materials have such a high de­

quent gingival recession is minimized, a twisted no.

gree of tear strength resistance that they can record

oo cord impregnated with aluminum sulfate (Gingi­

the finish line and the intact tooth structure beyond

Aid Z-Twist), or a nonimpregnated compact no. ooo

the fi nish line using a thickness level below litera­

cord (Uitrapak) soaked in aluminum chloride (Hemo­

ture recommendations. Because hydrocolloid i mpres­

dent, Premier) can be used. If polyether impression

sion materials require invasive horizontal retraction,

material is used, the area should be rinsed copious­

the authors do not use them (Fig 6-72).

ly before the impression is taken to prevent incom-

..

Technical Considerations for Soft Tissue Retraction

.

Figs 6-73 and 6-74 Clinical case of a 30-year-old woman who requested the restoration of the metal-ceramic crown on the maxillary left cen­ tral incisor. After the crown has been removed. an inadequate preparation is revealed. with a post and core of dubious function. Fig 6-75 Diagnostic waxup The planned restoration of the left central incisor and the porcelain laminate veneer for the right central in cisor wilt give the central incisors new length and luminosity Fig 6-76 Removal of the dowel and bleaching of the nonvital tooth provided a suitable tooth preparation for a feldspathic ceramic crown. Fi g 6-77 After whitening. the tooth was reconstructed with a fiberglass dowel, and a no. DO retraction cord was placed. Fig 6-78 Apical retraction as viewed through the stereomicroscope. Fig 6-79 Finish line is repositioned with ultra­ sonic tools and finished with a rounded chisei iDeppeler D M l l .

00

T h e authors' philosophy regarding restorative

nique, preferring instead methods of retraction that

work is to favor techniques that cause the least trau­

accomplish the minimum amount of horizontal dis­ 0.2

ma to tooth structure and gingiva; the authors rec­

placement-about

ommend the s i ng le-co rd technique, the selective

cord and the restoration margin3•-required for

m m between the retraction

double-cord technique, the use of a single cord com­

modern elastomeric i mpression materials.3S Such

bined with xpasyl, or even radiosurgery to remove

techniques enable the clinician to accomplish pre­

small amounts of tissue (figs 6·73 to 6·88). The

cise repositioning of the restoration margin without

authors discourage the use of the double-cord tech-

risking the stability of the gingival tissue.

•

111

Technical Considerations for Soft Tissue Retraction

.

Figs 6-73 and 6-74 Clinical case of a 30-year-old woman who requested the restoration of the metal-ceramic crown on the maxillary left cen­ tral incisor. After the crown has been removed. an inadequate preparation is revealed. with a post and core of dubious function. Fig 6-75 Diagnostic waxup The planned restoration of the left central incisor and the porcelain laminate veneer for the right central in cisor wilt give the central incisors new length and luminosity Fig 6-76 Removal of the dowel and bleaching of the nonvital tooth provided a suitable tooth preparation for a feldspathic ceramic crown. Fi g 6-77 After whitening. the tooth was reconstructed with a fiberglass dowel, and a no. DO retraction cord was placed. Fig 6-78 Apical retraction as viewed through the stereomicroscope. Fig 6-79 Finish line is repositioned with ultra­ sonic tools and finished with a rounded chisei iDeppeler D M l l .

00

T h e authors' philosophy regarding restorative

nique, preferring instead methods of retraction that

work is to favor techniques that cause the least trau­

accomplish the minimum amount of horizontal dis­ 0.2

ma to tooth structure and gingiva; the authors rec­

placement-about

ommend the s i ng le-co rd technique, the selective

cord and the restoration margin3•-required for

m m between the retraction

double-cord technique, the use of a single cord com­

modern elastomeric i mpression materials.3S Such

bined with xpasyl, or even radiosurgery to remove

techniques enable the clinician to accomplish pre­

small amounts of tissue (figs 6·73 to 6·88). The

cise repositioning of the restoration margin without

authors discourage the use of the double-cord tech-

risking the stability of the gingival tissue.

•

111

Technical Considerations for Soft Tissue Retraction

Fig 6-80 Use of kaolin and aluminum chloride IExpasyt) allows for greater control of the interproximal tissue and increased horizontal retraction. Fig 6-81 Effect of Expasyt at the moment of impression taking.

Fig 6-81 Detail of the impression. Note the distinct and detailed finish line with the proper linearity.

Fig 6-83 Feldspathic ceramic crown and porcelain laminate veneer on the master cast.

Fig 6-84 Patient's smile 15 days alter cementation.

Technical Considerations for Soft Tissue Retraction

Fig 6-80 Use of kaolin and aluminum chloride IExpasyt) allows for greater control of the interproximal tissue and increased horizontal retraction. Fig 6-81 Effect of Expasyt at the moment of impression taking.

Fig 6-81 Detail of the impression. Note the distinct and detailed finish line with the proper linearity.

Fig 6-83 Feldspathic ceramic crown and porcelain laminate veneer on the master cast.

Fig 6-84 Patient's smile 15 days alter cementation.

Fig 6-85 Complete smile.

Fig 6-86 Overall appearance of restorations in relation to the form and esthetics of the adjacent natural dentition.

Figs 6-87 and 6-88 lateral appearance of the restoration under the stereomicroscope. further illustrating its harmony with the natural denti­ tion in terms both of color and shape. The emergence profile of the restorations from the gingival sulcus is particularly effective.

Fig 6-85 Complete smile.

Fig 6-86 Overall appearance of restorations in relation to the form and esthetics of the adjacent natural dentition.

Figs 6-87 and 6-88 lateral appearance of the restoration under the stereomicroscope. further illustrating its harmony with the natural denti­ tion in terms both of color and shape. The emergence profile of the restorations from the gingival sulcus is particularly effective.

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

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207

CHAPTER 6 Technical Considerations for Soft Tissue Retraction

9· Kois JC. Altering gingival levels: The restorative connec·

REFEREN CES 1. Nevins M. Skurow HM. The intracrevicular restorative

10. Tarnow D. Stahl SS. Magner A. Zamzok ). Human gingi·

margin, the biologic width, and the maintenance of the

val attachment responses to subgingival crown place­

gingival margin. lnt J Periodontics Restorative Dent

ment. Marginal remodelling. J Clin Periodontal 1986;13:

1984:4:3>-49·

563-569.

2.

18. A2Zi R, Tsao TF. Carranza FA. Kenney EB. Comparative

11on. Part 1: Biologic variables. J Esthet Dent 1994;6:3-9.

Reiman MS. Exposure of subgingival margins by non·

11. Walie GN, van der Weijden FA. Spanauf AJ. de Quincey

surgical gingival displacement. J Prosthet Dent 1976:36:

GN. Lengthening clinical crowns: A solution for specific

64�54·

periodontal, restorative and esthetic problems. Quintes·

3. Richter·Snapp K. Aquilino SA. Svare W. Turner A. Change in marginal it as related to margin design. alloy

12.

restorations. I Prosthet Dent 1988:6o:435-439·

hemorrhage. J Prosthet Dent 1984:51:647-651.

concept in periodontics and restorative dentistry. Alpha Omegan 1977;70:62-65.

13. Loe H, Silness 1. Tissue reactions to string packs used in ixed restorations. J Prosthet Dent 1963;13:318-323.

4 · Magne P. Magne M. Belser U. Impressions and esthetic

gival retraction medicaments on human gingival ibro· blasts [abstract 1411t J Dent Res 1987;66(spec issue) :283. 28. Albers HF. Impressions: A Text for Selection of Materials and Techniques. Santa Rosa. A: Alto Books, 199>:45-46.

crowns. J Prosthet Dent 1986:55:21-23. 20.

Runyan DA. Reddy TG Jr. Shimada LM. Auid absorbency of retraction cords after soaking in aluminum chloride solution. J Prosthet Dent 1988;6o:676678.

21.

Phillips RW. Skinne(s Science of Dental aterials. ed 9· Philadelphia: Saunders. 1991:45-46.

30. agne P. Belser U. Bonded Porcelain Restorations in the Anterior Dentition: A Biomimetic Approach. Berlin: Quin·

sponse induced by chemical retraction agents in beagle

tessence. 202:244-247.

dogs. tnt J Prosthodont 2002;15:14-19. 22.

29.

Kopac I, Cvetko E, arion L. Gingival inlammatoy re·

31. Laufer BZ. Saharav H. Langer H. Cardash S. The closure

Shaw DH. Krejci RF. Gingival retraction preference of

of the gingival crevice following gingival retraction for

dentists in general practice. Quintessence lnt 1986;17:

impression making. J Oral Rehabil 1997;24:62�35.

277-280. 23. Jokstad A. Clinical trial of gingival retraction cords. J Prosthet Dent 1999:81:258-261.

5· Gargiulo A. Wenz FM. Orban B). Dimensions and rela·

rehabilitation: The preparatory work, clinical procedures

24. Benson BW. Bamberg TJ. Hatch RA. Homan W )r. Tissue

tion of the dentogingival junction in humans. J Peri­

and materials (in French and German]. Schweiz Monats·

displacement methods in ixed prosthodontics. I Prosthet

odontal 1961:32: 261-267.

schr Zahnmed 1995:105:1302-1316.

Dent 1986:55:175-181.

6. Dragoo MR. Williams GB. Periodontal tissue reactions to

27. Bata JP. Fe1gal R), Colman HL. Cytotoxic efects of gin·

Prosthet Dent

19. Tebrock OC. issue retraction for esthetic ceramometal

Nemez H, Donovan T, Landesman H. Exposing the gin· gival margin: A systematic approach for the control of

1

1983:50:561-565.

sence lnt 1994:25:81-88.

type, and porcelain proximity in porcelain·fused-to·metal

4. Ingber )S. Rose LF. Coslet )G. The "biologic width": A

study of gingival retraction methods.

32. Sherman JA. Electrosurgical accessories: New advance· ments. Oral Health 1986;76:37-39. 33· Kalkwaf KL. Krejci RF. Shaw DH. Edison AR. Histologic evaluation of gingival response to an electrosurgical blade. J Oral axilloac Surg 1987:45:671-674. 34· Lauer BZ, Saharav H . Cardash HS. The linear accuracy

15. Laufer BZ. Saharav H, Ganor Y. Cardash HS. The efect

25. Shaw DH, Krejci RF. Cohen OM. Retraction cords with

of impressions and stone dies as aected by the thick·

eriodontics Restorative

of marginal thickness on the distortion of diferent im·

aluminum chloride. Efect on the gingiva. Oper Dent

ness of the impression margin. lnt J Prosthodont 1994;

7. Dragoo MR. Williams GB. Periodontal tissue reactions to

16. Rue! ). Schuessler PJ. Malament K. Mori D. Efect of re·

26. de Camargo LM. Chee W, Donovan TE. Inhibition of

restorative procedures, part II. lnt I Periodontics Restor·

traction procedures on the periodontium in humans. J

polymerization of polvinyl siloxanes by medicaments

eect of sulcular width on the linear accuracy of impres­

alive Dent 1982;2:34-45.

Prosthet Dent 1980:44:5o8-515.

used on gingival retraction cords. I Prosthet Dent 1993:

sion materials in the presence of an undercut. lnt J

70:114-117.

Prosthodont 2004;17:585-589.

restorative procedures. lnt Dent 1981:1:8-23.

I

pression materials. J Prosthet Dent 1996:76:466-471.

8. acek JS. Gher ME, Assad DA, Richardson AC, Giam·

17. de Gennaro GG, Landesman HM. Calhoun )E. Martinol

barresi ll. The dimensions of the human dentogingival

I. A comparison of gingival inlammation related to

junction. lnt J Periodontics Restorative Dent 1994;14:

retraction cords. J Prosthet Dent 1982;47:384-386.

1980;5:138-144·

7:247-252. 35· Saharav H. Kupeshmidt I. Laufer BZ. Cardash HS. The

154-165.

207

C H A P T E R

7

C L I N I C AL C O N S I D ERAT I O N S F O R P R O V I S I O NAL P R O S T H E SES

P

rovisional prosthodontic procedures are fun­ damental to realizing a prosthetic restoration, whether involving a single tooth or multiple

teeth. Most clinicians now recognize the importance of minimizing the damage caused during impression taking. We also now understand the need to support the tissues with provisionals that are anatomically suitable in terms of shape, size, and length and that have perfectly polished margins in order to promote

•

Provide protection for the pulpal organ

•

Allow function in occlusion

•

FIG 7-1

FIG 7-2

FIG 7-3

FIG 7-4

FIG 7-5

FIG 7-6

Ensure a good fit and stable position

•

Permit easy access for hygiene

•

Safeguard the health of the periodontal margin

•

Guarantee acceptable esthetics

•

Exhibit good strength and retention

A broad range of technologies and materials are

satisfactory healing after the impression phase.'-3 In

available for fabricating provisionals that meet these

complex cases, in addition to conditioning and di­

standards. With respect to how long they are expect­

recting the gingival tissues, the provisional restora­

ed to last, provisional prostheses are classified as

tion is essential diagnostically and therapeutically in

either short term or long term.

the initial stage of treatment. In simpler cases, it

Short-term provisional prostheses are further

promotes correct maturation and integration of the

subclassified as irst, second, or third-generation, de­

soft tissues while performing its essential function,

pending on their purpose:

which is to protect the pulp and preserve the spatial relationship with adjacent and opposing teeth (Figs 7-1 to 7-6).

1.

First-generation provisional a. Preformed direct provisional prosthesis b. Provisional prosthesis with a thermoplastic or

CHARACTERISTICS A N D CLASS I FI CATI O N O F PROVI S I O NAL RESTORATIONS T h e ideal qualities of a provisional prosthetic res­ toration, as described by Shillingburg et al,4 are as follows:

8

silicone index c. Provisional based on a diagnostic waxup before preparation of the teeth 2. Second-generation

provisional

3- Third-generation provisional

..

Fig 7-1 A 44-year-old man presented for emergency treatment as a result of the decementation of the maxillary right lateral incisor restora­ tion. There was also secondary infiltration of lhe crowns on lhe right canine and left lateral incisor. The restored canine had a n artificial root. which was needed because the tooth showed marked recession. The crowns were replaced with two immediate provisional restorations. using direct preformed shells. Fig 7-2 Hole the initial adaptation of the provisional prosthesis on the canine and the residual lateral i n cisor. '•g '-3 Root canal treatment was redone. and lhe teeth were re-prepared for reconstruction with alumina core ceramic crowns. : , Replacement of the direcl provisional crowns w1th two second-generation provisionals. fabricated after the teeth were prepared and a polyether impres­ sion made. Fig• 7-5 and 7-6 Before and after cementation of the permanent crowns. respectively.

C H A P T E R

7

C L I N I C AL C O N S I D ERAT I O N S F O R P R O V I S I O NAL P R O S T H E SES

P

rovisional prosthodontic procedures are fun­ damental to realizing a prosthetic restoration, whether involving a single tooth or multiple

teeth. Most clinicians now recognize the importance of minimizing the damage caused during impression taking. We also now understand the need to support the tissues with provisionals that are anatomically suitable in terms of shape, size, and length and that have perfectly polished margins in order to promote

•

Provide protection for the pulpal organ

•

Allow function in occlusion

•

FIG 7-1

FIG 7-2

FIG 7-3

FIG 7-4

FIG 7-5

FIG 7-6

Ensure a good fit and stable position

•

Permit easy access for hygiene

•

Safeguard the health of the periodontal margin

•

Guarantee acceptable esthetics

•

Exhibit good strength and retention

A broad range of technologies and materials are

satisfactory healing after the impression phase.'-3 In

available for fabricating provisionals that meet these

complex cases, in addition to conditioning and di­

standards. With respect to how long they are expect­

recting the gingival tissues, the provisional restora­

ed to last, provisional prostheses are classified as

tion is essential diagnostically and therapeutically in

either short term or long term.

the initial stage of treatment. In simpler cases, it

Short-term provisional prostheses are further

promotes correct maturation and integration of the

subclassified as irst, second, or third-generation, de­

soft tissues while performing its essential function,

pending on their purpose:

which is to protect the pulp and preserve the spatial relationship with adjacent and opposing teeth (Figs 7-1 to 7-6).

1.

First-generation provisional a. Preformed direct provisional prosthesis b. Provisional prosthesis with a thermoplastic or

CHARACTERISTICS A N D CLASS I FI CATI O N O F PROVI S I O NAL RESTORATIONS T h e ideal qualities of a provisional prosthetic res­ toration, as described by Shillingburg et al,4 are as follows:

8

silicone index c. Provisional based on a diagnostic waxup before preparation of the teeth 2. Second-generation

provisional

3- Third-generation provisional

..

Fig 7-1 A 44-year-old man presented for emergency treatment as a result of the decementation of the maxillary right lateral incisor restora­ tion. There was also secondary infiltration of lhe crowns on lhe right canine and left lateral incisor. The restored canine had a n artificial root. which was needed because the tooth showed marked recession. The crowns were replaced with two immediate provisional restorations. using direct preformed shells. Fig 7-2 Hole the initial adaptation of the provisional prosthesis on the canine and the residual lateral i n cisor. '•g '-3 Root canal treatment was redone. and lhe teeth were re-prepared for reconstruction with alumina core ceramic crowns. : , Replacement of the direcl provisional crowns w1th two second-generation provisionals. fabricated after the teeth were prepared and a polyether impres­ sion made. Fig• 7-5 and 7-6 Before and after cementation of the permanent crowns. respectively.

CHAPTER 1 Clinical Considerations for Provisional Prostheses

.. Long-term provisional prostheses have a metal

more marginal discrepancies than composite based

frame with a base that can be filled to provide good

on bisphenol glycidyl methacrylate (bis-GMA) or

stabilization and resistance in occlusion.

polyethyl methacrylate and vinylethyl methacrylate,

Various techniques can be used for fabricating a

which had similar values.8 The latter materials are

provisional restoration, each one developed to meet

among the most frequently used for provisional

RESTORAT I O N S

tends to be difficult to work with and forms bubbles that impede satisfactory adhesion to the thermo­ plastic shell (Figs 7-7 and 7-8).

Short-term provis ionals

The authors are convinced that adhering to the treatment plan, fabricating the provisional prosthe­

restorations. Christensen9 lists polyethyl methacry­

First generation

sis in the laboratory, and scrupulously monitoring

late, bis-GMA, and the last-generation materials

The direct provisional restoration is generally made

the operating times will guarantee an optimal func­

Clinical consi derations and p roced u res

described in chapter 9 as suitable for this purpose.

only in emergencies using a preformed shell (ION,

tional and esthetic outcome. Conversely, a lack of

In a study comparing the effect of six resin materi­

3M Espe). Made of polycarbonate, these shells are

adequate planning will result i n unnecessary loss of

The different techniques for fabricating a provision­

als,'0 Tjan et al" showed that various materials of

classified by type and size/shape rather than func­

time and energy, while direct preformed and ther­

al restoration should be considered in clinical situa­

similar chemical composition may exhibit wide dif­

tion or color, which are largely determined by the

moplastic shells will need to be replaced after a few

tions that require a provisional with specific charac­

ferences in precision at the margin.

acrylic resin material used for filling them. The shells

days since they cannot sustain masticatory loads for

Another important feature for the clinician is the

are preformed for different tooth shapes (ie, incisors,

even a short period.

second or third generation should be based at least

amount of heat generated during hardening of both

canines, premolars, and molars) and must be re­

A more suitable solution, in terms of function and

in part on how long it is planned to remain in the

the relining materials and the materials used to make

placed with laboratory-fabricated provisionals within

esthetics, is to prefill the shell or use shell provi­

oral cavity. If it is to be used over a relatively long

the provisionals with a direct technique. When a tra­

1

period, the provisional restoration should have a

ditional self-curing acrylic resin is used, intrapulpal

more precise margin and the capacity to resist

temperatures can rise by 0-42°C to 7.21°C during fill­

theses are made by molding a shell of thermoplas­

to simulate the ideal preparation. These shells act as

greater masticatory loads.

ing. According to a scientific study of the phenome­

tic material (Erkopress, Erkodent), which is pressure­

a support for the acrylic resin, which is baked in the

the demands of speciic clinical situations.

teristics. Selection of a provisional restoration of the

In addition to the risk of marginal infiltration,

week. In the non-emergency setting, provisional pros­

non, 12 polyethyl methacrylate generated the most

sionals that are fabricated in the lab after the diag­ nostic stone cast or its duplicate has been modified

shaped after the disk has been preheated to 50°C to

lab and can be made by following the indications

teeth that have been prepared and provisionally

heat. When using materials that generate a consid­

6o°C on the plaster cast. The existing parameters

provided by the diagnostic waxup, depending on the

are not modified in this stage.

restored tend to exhibit inflammation of the peri­

erable degree of heat, it is advisable to apply con­

odontal margin. Studies have shown that more

tinuous jets of air-water spray while the material is

plaque accumulates on the surface of provisional

hardening to counteract the heat as much as possi­

index from an impression using extrahard (85

cone and poured in plaster, it can provide support

restorations than on the cervical surfaces of adja­

ble. When selecting a material for intraoral filling, the

shores) silicone (Zetalabor, Zhermack). The acrylic

for the fabrication of the provisional restoration, act­

cent natural teeth.S Therefore, the operator must be

potential increase in temperature is an important

resin is applied to the silicone index and pressed

ing as a mold for the resin, which is cured and then

precise in closing the marginal borders and defining

concern for minimizing damage to the pulp chamber.

over the preparations until curing is complete. This

finished in the laboratory.

the emergence profiles to prevent potential compli­ cations such as gingival recession_6.7

A variation of this technique is to make a silicone

The margins of provisional restorations are fin­

results in immediate realization of a provisional

ished in resin. Because the resin inevitably deforms

restoration.

complexity and requirements of the treatment plane. Once the waxup is duplicated using the proper sili­

To assist the clinician in controlling the position of the provisional prosthesis during filling, the labo­

The material used to reproduce the finish line of

and fractures under stress,'3·'• provisional prosthe­

The pressed-shell technique produces a provi­

ratory technician makes an index in extrahard sili­

the provisional prosthetic margin has a significant

ses must be used for a limited period or checked

sional that has the advantage of being very thin and

cone (85 shores) that is applied directly to the fin­

effect on its precision. A study comparing diferent

and replaced frequently.

materials found that epimine presents considerably

210

.. PROCEDU RES FOR PROVI S I O NAL

..

thus adapts well to the shape of the preparations

ished provisional, forming occlusal stops on the

and the interproximal spaces. Moreover, once the

adjacent natural teeth for added stability. The provi­

resin curing is finished, it becomes the surface of

sional prosthesis is then inserted into the silicone

the provisional restoration. Although the technique

index, which facilitates proper positioning on the

adapts readily to the clinical setting, it poses the

preparations in terms of axis and d i rection, thus

problem of using a fairly large amount of acrylic

eliminating the danger of excessive lengthening or

resin in the office as a support material. Acrylic resin

repositioning (Figs 7-9 to 7-13).

..

211

CHAPTER 1 Clinical Considerations for Provisional Prostheses

.. Long-term provisional prostheses have a metal

more marginal discrepancies than composite based

frame with a base that can be filled to provide good

on bisphenol glycidyl methacrylate (bis-GMA) or

stabilization and resistance in occlusion.

polyethyl methacrylate and vinylethyl methacrylate,

Various techniques can be used for fabricating a

which had similar values.8 The latter materials are

provisional restoration, each one developed to meet

among the most frequently used for provisional

RESTORAT I O N S

tends to be difficult to work with and forms bubbles that impede satisfactory adhesion to the thermo­ plastic shell (Figs 7-7 and 7-8).

Short-term provis ionals

The authors are convinced that adhering to the treatment plan, fabricating the provisional prosthe­

restorations. Christensen9 lists polyethyl methacry­

First generation

sis in the laboratory, and scrupulously monitoring

late, bis-GMA, and the last-generation materials

The direct provisional restoration is generally made

the operating times will guarantee an optimal func­

Clinical consi derations and p roced u res

described in chapter 9 as suitable for this purpose.

only in emergencies using a preformed shell (ION,

tional and esthetic outcome. Conversely, a lack of

In a study comparing the effect of six resin materi­

3M Espe). Made of polycarbonate, these shells are

adequate planning will result i n unnecessary loss of

The different techniques for fabricating a provision­

als,'0 Tjan et al" showed that various materials of

classified by type and size/shape rather than func­

time and energy, while direct preformed and ther­

al restoration should be considered in clinical situa­

similar chemical composition may exhibit wide dif­

tion or color, which are largely determined by the

moplastic shells will need to be replaced after a few

tions that require a provisional with specific charac­

ferences in precision at the margin.

acrylic resin material used for filling them. The shells

days since they cannot sustain masticatory loads for

Another important feature for the clinician is the

are preformed for different tooth shapes (ie, incisors,

even a short period.

second or third generation should be based at least

amount of heat generated during hardening of both

canines, premolars, and molars) and must be re­

A more suitable solution, in terms of function and

in part on how long it is planned to remain in the

the relining materials and the materials used to make

placed with laboratory-fabricated provisionals within

esthetics, is to prefill the shell or use shell provi­

oral cavity. If it is to be used over a relatively long

the provisionals with a direct technique. When a tra­

1

period, the provisional restoration should have a

ditional self-curing acrylic resin is used, intrapulpal

more precise margin and the capacity to resist

temperatures can rise by 0-42°C to 7.21°C during fill­

theses are made by molding a shell of thermoplas­

to simulate the ideal preparation. These shells act as

greater masticatory loads.

ing. According to a scientific study of the phenome­

tic material (Erkopress, Erkodent), which is pressure­

a support for the acrylic resin, which is baked in the

the demands of speciic clinical situations.

teristics. Selection of a provisional restoration of the

In addition to the risk of marginal infiltration,

week. In the non-emergency setting, provisional pros­

non, 12 polyethyl methacrylate generated the most

sionals that are fabricated in the lab after the diag­ nostic stone cast or its duplicate has been modified

shaped after the disk has been preheated to 50°C to

lab and can be made by following the indications

teeth that have been prepared and provisionally

heat. When using materials that generate a consid­

6o°C on the plaster cast. The existing parameters

provided by the diagnostic waxup, depending on the

are not modified in this stage.

restored tend to exhibit inflammation of the peri­

erable degree of heat, it is advisable to apply con­

odontal margin. Studies have shown that more

tinuous jets of air-water spray while the material is

plaque accumulates on the surface of provisional

hardening to counteract the heat as much as possi­

index from an impression using extrahard (85

cone and poured in plaster, it can provide support

restorations than on the cervical surfaces of adja­

ble. When selecting a material for intraoral filling, the

shores) silicone (Zetalabor, Zhermack). The acrylic

for the fabrication of the provisional restoration, act­

cent natural teeth.S Therefore, the operator must be

potential increase in temperature is an important

resin is applied to the silicone index and pressed

ing as a mold for the resin, which is cured and then

precise in closing the marginal borders and defining

concern for minimizing damage to the pulp chamber.

over the preparations until curing is complete. This

finished in the laboratory.

the emergence profiles to prevent potential compli­ cations such as gingival recession_6.7

A variation of this technique is to make a silicone

The margins of provisional restorations are fin­

results in immediate realization of a provisional

ished in resin. Because the resin inevitably deforms

restoration.

complexity and requirements of the treatment plane. Once the waxup is duplicated using the proper sili­

To assist the clinician in controlling the position of the provisional prosthesis during filling, the labo­

The material used to reproduce the finish line of

and fractures under stress,'3·'• provisional prosthe­

The pressed-shell technique produces a provi­

ratory technician makes an index in extrahard sili­

the provisional prosthetic margin has a significant

ses must be used for a limited period or checked

sional that has the advantage of being very thin and

cone (85 shores) that is applied directly to the fin­

effect on its precision. A study comparing diferent

and replaced frequently.

materials found that epimine presents considerably

210

.. PROCEDU RES FOR PROVI S I O NAL

..

thus adapts well to the shape of the preparations

ished provisional, forming occlusal stops on the

and the interproximal spaces. Moreover, once the

adjacent natural teeth for added stability. The provi­

resin curing is finished, it becomes the surface of

sional prosthesis is then inserted into the silicone

the provisional restoration. Although the technique

index, which facilitates proper positioning on the

adapts readily to the clinical setting, it poses the

preparations in terms of axis and d i rection, thus

problem of using a fairly large amount of acrylic

eliminating the danger of excessive lengthening or

resin in the office as a support material. Acrylic resin

repositioning (Figs 7-9 to 7-13).

..

211

Clinical Considerations for Provisional Prostheses

P R O V I S I O N A L S I N

S H A P E .

A N A T O M I C A L L Y

V O L U M E .

A N D

C O R R E C T

E X T E N S I O N

F1g 7-7 8011ng of the stone cast and molded thermoplastic disk. Fig 7-8 The self-curing resin then is applied directly on the prepared tooth until it flits the shell. The advantage of this system is the immediate adaptation because the thickness of the old restoration leaves ample space for fitting in the material. Fig 7-g The provisional restoration of both first and second generations fabricated in the lab is used with an ultrahard silicone index 185 shores! that functions as a guide during positioning and relining. Fig 1-10 The provisional is supported by the index and adapts correctly in terms of position and length because the silicone index has occlusal stops that ensure proper repositioning.

212

M A I N T A I N

P R O P E R

P R O P O R T I O N S

R E L A T I O N S

A C H I E V E D

I N

A N D L A B

Fig 7-11 The silicone guide also makes it easier to obtain the correct axis during filling. Figs 7-12 and 7-13 Clinical case illustrating excellent adaptation of the provisional restoration in the maxillary right and left anterior segments and good maturation of the interproximal tissues.

213

Clinical Considerations for Provisional Prostheses

P R O V I S I O N A L S I N

S H A P E .

A N A T O M I C A L L Y

V O L U M E .

A N D

C O R R E C T

E X T E N S I O N

F1g 7-7 8011ng of the stone cast and molded thermoplastic disk. Fig 7-8 The self-curing resin then is applied directly on the prepared tooth until it flits the shell. The advantage of this system is the immediate adaptation because the thickness of the old restoration leaves ample space for fitting in the material. Fig 7-g The provisional restoration of both first and second generations fabricated in the lab is used with an ultrahard silicone index 185 shores! that functions as a guide during positioning and relining. Fig 1-10 The provisional is supported by the index and adapts correctly in terms of position and length because the silicone index has occlusal stops that ensure proper repositioning.

212

M A I N T A I N

P R O P E R

P R O P O R T I O N S

R E L A T I O N S

A C H I E V E D

I N

A N D L A B

Fig 7-11 The silicone guide also makes it easier to obtain the correct axis during filling. Figs 7-12 and 7-13 Clinical case illustrating excellent adaptation of the provisional restoration in the maxillary right and left anterior segments and good maturation of the interproximal tissues.

213

CHAPTER 7 Clinical Considerations for Provisional Prostheses

. Second generation

Second-generation provisionals are fabricated after

in irreversible hydrocolloid material, so that the

Filling can be immediate (the traditional type) or

A uniform mixture of acrylic resin is applied inside

laboratory is advised of all of the variations in

delayed. Immediate filling is generally performed

the prepared resin shell, and care is then taken to

elastomeric impressions are taken. A nonimpregnat­

shape, color, and so forth desired by the patient and

directly on the preparations just after the impression

position and adapt it correctly in the mouth. Once

ed retraction cord is placed in the gingival sulcus for

clinician.

is taken, when it is not easy to achieve a satisfac­

positioned in the mouth, the provisional must be

tory level of precision.

delicately removed during self-curing via a gentle

vetical and horizontal displacement of the tissues and after the finish line of the right depth and design has been finished. Apical repositioning of the finish

Long-term p rovisionals

To obtain more accurate margins, it is possible to

back-and-forth movement over about 2 mm. This

execute a second, delayed filling known as precision

prevents adhesion to the prepared tooth and unde­

line has not been carried out at this point. This repo­

When it becomes necessay for therapeutic reasons

illing. This is executed on the master cast, after the

sired retention in the undercut areas of the adjacent

sitioning of the inish line may be performed imme­

to prolong the use of a provisional restoration in the

final impression has been taken during a subse­

teeth. It is also advisable to cool the tooth and the

diately or later, during the session when the defini­

oral cavity, it is advisable to make the prosthesis

quent stage, and again after the provisional (which

provisional with water. l -'7-•B

tive impression is taken (in which case another refill­

using acylic resin with a reinforcing metal frame,

has already been filled during the initial stage) has

In this initial filling, the goal is to make an incisal

ing of the provisional will be necessary).

which increases its resistance to functional and mas­

been decemented. The provisional prosthesis is

stop internal to the provisional and again perform

Generally, a provisional prosthesis made in this

ticatory loads. This reinforcing structure is made in

roughened internally with a bur and relined with

initial adaptation of the resin to the surfaces of the

fashion does not need additional refilling or modifi­

a single-casting monoblock, creating adequate oc­

composite resin directly on the master cast, thus

prepared teeth. The clinician should not pay undue

cation, except perhaps for some isolated areas; this

clusal supports and reinforcing connections. It can

avoiding errors caused by excess soft tissue and

attention to the precision of the prosthetic margins;

is why it is called a precision provisional prosthesis.

also be useful in conditioning the sot tissues after

oral fluids.

eforts should be directed at ensuring that the resin

However, this is possible only if the impression does

surgery. For this reason, the provisional prosthesis

There are many diferent filling techniques. Among

material moistened with monomer adheres well to

not present major distortions (Figs 7-14 to 7-22).

can be made so that it can be filled. •s In fact, when

these are two that appear similar but actually involve

the inish line using a Heidemann spatula. Once the

using provisionals with a metal frame, it is prefer­

diferent approaches, results, and fabrication times.

resin has cured, the provisional is removed from the

Third generation

able that the marginal seal be made in resin, so that

The first technique, which has been in common use

mouth and placed in a pressure pot to accelerate

Finally, there are the third-generation provisionals,

if necessary the clinician can execute further refilling

for some time, consists of executing successive fill­

polymerization.

so called because they typically replace the second­

and adaptation following postsurgical healing or for

ings with unheated acrylic resin and waiting for them

Once polymerization is complete, another re-illing

generation provisionals. The third-generation provi­

other situations (Figs 7-40 and 7-41).

to harden completely before making any further

is needed to define the margin with precision. This

sional is thus fabricated after the definitive impres­

modifications to the material. In order to accelerate

is done ater the excess resin at the margin and the

sion has been taken and the master cast poured.

the hardening process and reduce the formation of

thin layer that has hardened on the internal axial

This type of provisional prosthesis is used in

C L I N I CAL CO N S I D ERATI O N S FOR

air bubbles (and thus obtain an ideal compact con­

surfaces and marginal area has been removed using

THE WORKI NG STAGES

sistency), the unpolymerized provisional can be

tungsten carbide burs. Care should be taken not to

dontic team an opportunity to analyze and confirm

immersed in lukewarm water (3o•C)•6 or in a pres­

remove the resin at the level of the occlusal and

each of the functional and esthetic parameters that

Filling

sure pot at 4 bars for 10 minutes.

palatal internal stops (Fig 7-45).

Filling involves brushing a layer of petroleum jelly

For the second illing, a more liquid form of resin

For most types of provisional prostheses made of

directly on the preparations to isolate them and pre­

is placed in the provisional shell. It is important to

be used to reproduce the desired effect after the

acrylic resin, the filling and finishing of the pros­

vent adhesion of the two surfaces as well as over­

spread and adapt the resin to the margin as accu­

patient approves the design (Figs 7-23 to 7-39).

thetic margin are critical steps because these proce­

heating (Figs 7-42 to 7-44). The authors prefer to use

rately as possible, using a thin Heidemann spatula

Clin ically, it is possible to use the seco nd­

dures make it possible to obtain precise restorations

a layer of liquid soap to isolate the prepared tooth;

coated with monomer (Figs 7-46 and 7-47). The same

generation provisional as a guide for modifications

that simulate the emergence profile and support the

since soap reduces surface tension more than does

procedures used to obtain polymerization in the first

made directly in white wax. After the patient's ap­

soft tissues (in the same manner as the definitive

petroleum jelly, this improves the density of the resin,

stage are carried out.

proval, an impression of these modiications is made

ceramic restoration).

complex cases; it ofers the patient and the prostho­

were previously proposed and then applied in the diagnostic waxup. The final restorative materials will

.

reducing the risk of creating adaptation defects or air bubbles.

214

The authors prefer the second technique for intra­ oral filling because it is simple and fast. It consists .

215

CHAPTER 7 Clinical Considerations for Provisional Prostheses

. Second generation

Second-generation provisionals are fabricated after

in irreversible hydrocolloid material, so that the

Filling can be immediate (the traditional type) or

A uniform mixture of acrylic resin is applied inside

laboratory is advised of all of the variations in

delayed. Immediate filling is generally performed

the prepared resin shell, and care is then taken to

elastomeric impressions are taken. A nonimpregnat­

shape, color, and so forth desired by the patient and

directly on the preparations just after the impression

position and adapt it correctly in the mouth. Once

ed retraction cord is placed in the gingival sulcus for

clinician.

is taken, when it is not easy to achieve a satisfac­

positioned in the mouth, the provisional must be

tory level of precision.

delicately removed during self-curing via a gentle

vetical and horizontal displacement of the tissues and after the finish line of the right depth and design has been finished. Apical repositioning of the finish

Long-term p rovisionals

To obtain more accurate margins, it is possible to

back-and-forth movement over about 2 mm. This

execute a second, delayed filling known as precision

prevents adhesion to the prepared tooth and unde­

line has not been carried out at this point. This repo­

When it becomes necessay for therapeutic reasons

illing. This is executed on the master cast, after the

sired retention in the undercut areas of the adjacent

sitioning of the inish line may be performed imme­

to prolong the use of a provisional restoration in the

final impression has been taken during a subse­

teeth. It is also advisable to cool the tooth and the

diately or later, during the session when the defini­

oral cavity, it is advisable to make the prosthesis

quent stage, and again after the provisional (which

provisional with water. l -'7-•B

tive impression is taken (in which case another refill­

using acylic resin with a reinforcing metal frame,

has already been filled during the initial stage) has

In this initial filling, the goal is to make an incisal

ing of the provisional will be necessary).

which increases its resistance to functional and mas­

been decemented. The provisional prosthesis is

stop internal to the provisional and again perform

Generally, a provisional prosthesis made in this

ticatory loads. This reinforcing structure is made in

roughened internally with a bur and relined with

initial adaptation of the resin to the surfaces of the

fashion does not need additional refilling or modifi­

a single-casting monoblock, creating adequate oc­

composite resin directly on the master cast, thus

prepared teeth. The clinician should not pay undue

cation, except perhaps for some isolated areas; this

clusal supports and reinforcing connections. It can

avoiding errors caused by excess soft tissue and

attention to the precision of the prosthetic margins;

is why it is called a precision provisional prosthesis.

also be useful in conditioning the sot tissues after

oral fluids.

eforts should be directed at ensuring that the resin

However, this is possible only if the impression does

surgery. For this reason, the provisional prosthesis

There are many diferent filling techniques. Among

material moistened with monomer adheres well to

not present major distortions (Figs 7-14 to 7-22).

can be made so that it can be filled. •s In fact, when

these are two that appear similar but actually involve

the inish line using a Heidemann spatula. Once the

using provisionals with a metal frame, it is prefer­

diferent approaches, results, and fabrication times.

resin has cured, the provisional is removed from the

Third generation

able that the marginal seal be made in resin, so that

The first technique, which has been in common use

mouth and placed in a pressure pot to accelerate

Finally, there are the third-generation provisionals,

if necessary the clinician can execute further refilling

for some time, consists of executing successive fill­

polymerization.

so called because they typically replace the second­

and adaptation following postsurgical healing or for

ings with unheated acrylic resin and waiting for them

Once polymerization is complete, another re-illing

generation provisionals. The third-generation provi­

other situations (Figs 7-40 and 7-41).

to harden completely before making any further

is needed to define the margin with precision. This

sional is thus fabricated after the definitive impres­

modifications to the material. In order to accelerate

is done ater the excess resin at the margin and the

sion has been taken and the master cast poured.

the hardening process and reduce the formation of

thin layer that has hardened on the internal axial

This type of provisional prosthesis is used in

C L I N I CAL CO N S I D ERATI O N S FOR

air bubbles (and thus obtain an ideal compact con­

surfaces and marginal area has been removed using

THE WORKI NG STAGES

sistency), the unpolymerized provisional can be

tungsten carbide burs. Care should be taken not to

dontic team an opportunity to analyze and confirm

immersed in lukewarm water (3o•C)•6 or in a pres­

remove the resin at the level of the occlusal and

each of the functional and esthetic parameters that

Filling

sure pot at 4 bars for 10 minutes.

palatal internal stops (Fig 7-45).

Filling involves brushing a layer of petroleum jelly

For the second illing, a more liquid form of resin

For most types of provisional prostheses made of

directly on the preparations to isolate them and pre­

is placed in the provisional shell. It is important to

be used to reproduce the desired effect after the

acrylic resin, the filling and finishing of the pros­

vent adhesion of the two surfaces as well as over­

spread and adapt the resin to the margin as accu­

patient approves the design (Figs 7-23 to 7-39).

thetic margin are critical steps because these proce­

heating (Figs 7-42 to 7-44). The authors prefer to use

rately as possible, using a thin Heidemann spatula

Clin ically, it is possible to use the seco nd­

dures make it possible to obtain precise restorations

a layer of liquid soap to isolate the prepared tooth;

coated with monomer (Figs 7-46 and 7-47). The same

generation provisional as a guide for modifications

that simulate the emergence profile and support the

since soap reduces surface tension more than does

procedures used to obtain polymerization in the first

made directly in white wax. After the patient's ap­

soft tissues (in the same manner as the definitive

petroleum jelly, this improves the density of the resin,

stage are carried out.

proval, an impression of these modiications is made

ceramic restoration).

complex cases; it ofers the patient and the prostho­

were previously proposed and then applied in the diagnostic waxup. The final restorative materials will

.

reducing the risk of creating adaptation defects or air bubbles.

214

The authors prefer the second technique for intra­ oral filling because it is simple and fast. It consists .

215

CHAPT£H 7 Clinical Considerations for Provisional Prostheses

7-20

Figs 7-14 and 7-15 Clinical case of a maxillary rehabilitation showing serious gingival recession and secondary caries and decementatio n of the maxillary left central incisor. Figs 7-16and7-17 After the inotial provisoonal shell !first generation! was made and the prepared teeth were reconstructed. and after a poly­ ether Impression was made with a nonimpregnated retraction cord in place. the stone cast with sectioned dies was used to make the new. second-generation provisional.

Figs 7-1 g and 7-20 Restoration in feldspathic ceramic. cemented with a n adhesive technique. Note the esthetics a n d functional relationships.

Figs 7-21 and 7-22 Proper management of the provisional permitted control over esthetic and functional aspects. resulting in a natural smile.

Fog 7-18 The cemen ted provisoonal after clonical ontegration. compared woth the final restoratoon !Fig 7-191. The shape and esthetic parame­ _ accordance wolh the ondocaloons furnoshed ters were altered on by the provisional and the diagnosloc waxup.

217

CHAPT£H 7 Clinical Considerations for Provisional Prostheses

7-20

Figs 7-14 and 7-15 Clinical case of a maxillary rehabilitation showing serious gingival recession and secondary caries and decementatio n of the maxillary left central incisor. Figs 7-16and7-17 After the inotial provisoonal shell !first generation! was made and the prepared teeth were reconstructed. and after a poly­ ether Impression was made with a nonimpregnated retraction cord in place. the stone cast with sectioned dies was used to make the new. second-generation provisional.

Figs 7-1 g and 7-20 Restoration in feldspathic ceramic. cemented with a n adhesive technique. Note the esthetics a n d functional relationships.

Figs 7-21 and 7-22 Proper management of the provisional permitted control over esthetic and functional aspects. resulting in a natural smile.

Fog 7-18 The cemen ted provisoonal after clonical ontegration. compared woth the final restoratoon !Fig 7-191. The shape and esthetic parame­ _ accordance wolh the ondocaloons furnoshed ters were altered on by the provisional and the diagnosloc waxup.

217

Clinical Considerations for Provisional Prostheses

Fog 7 23 In complex cases. for example. in thos 40-year-old female patoent who presented following contusion of the maxillary central incisors and right lateral oncosor. it may be advisable to follow the fabricatoon step by step usong a doagnostic waxup.

Fog 7 4 The clonical case presents considerable crowdong. and the treatment plan included possoble orthodontic ontervention. periodontal surgery woth omplants. and prosthetoc restoratoon The lack of space made it necessary to design a specofoc clinocal example that could be shown to the patoent to obtain informed consent for the planned treatment. fogs 7·25 a J 7-26 Two dofferent wax models were proposed, the first made wothout considering orthodontic treatment and the second reflect­ ong a comprehensove treatment plan. onvolvong seroal tooth extractoons and redostrobution of space. Because the central incisors and the right lateral were orreparably lost and there was very loltte peroodontal support. on addition to overcrowdong. the selectoon of the type of rehaboli­ tatoon to propose and then clonocally realoze depended on the optoons chosen in the prelimonary orthodontoc and periodontal plans.

211

Fig 7-27 The clinical orthodontic examination proposed serial extraction of the first premolars to reduce the overcrowding. followed by ortho­ dontic treatment and prosthetic rehabilitation to treat the new spaces. or prosthetic treatment alone. The feasibility of both treatment plans. however. was based on the prosthetic restoration. so the initial clinical diagnosis and the choice of treatment was delayed untol the two pros­ thetic options could be evaluated in the waxups. The difference on the space avaolable in the two options. because of the extractions. provid­ ed the opportunity to create different forms. Fogs 7-28 and 7-2g The lack of periodontal support and the short radicular length steered the choice of treatment toward a more conservative procedure. without additional extractions. The option was for a slower. progressive orthodontic extrusion of the compromised teeth. to pro­ vide more bone and periodontal support for the area afler the extractions. During the stages of slow extrusion. the length of the teeth must be reduced.

Fog 7-30 The compromised teeth were extracted. and the two canines and the lateral incisor were prepared for a prosthesis. After the com­ bined orthodontic and periodontal treatment. the provisional stage was managed using three subsequent provisionals to condition the tissues during the various stages of treatment. using different modalities and procedures. The first provisional was made in the lab. relying on the forms and dimensions represented in the diagnostic waxup. The goal was to restore the esthetics and function of the extracted teeth and con­ dition the tissues in the areas of extraction. Fig 7-31 After allowing an adequate period for healing (about 3 months). during which the condition of the tissues in the extraction areas was controlled and modified several times. a precision polyether impression was taken after positioning a nonimpregnated retraction cord (Ullrapak 000. Ullradent) and completing the finish lines of the preparations to define a reg ular. smooth line. A diamond -grit ball bur was used to redefine the edentulous areas anatomically and esthetically. (A scalpel may also be used.) The new provisional was made using the successive layering of dentin and enamel. creating a resin shell simolar to dentin. cast on a silicone ondex. and fonished woth a bur to give it a natural shape with mamelons. The provisional. properly finished and polished. has been fitted and adapted in the oral cavity. and the esthetic. functional. and phonetic characteristics have been checked.

219

Clinical Considerations for Provisional Prostheses

Fog 7 23 In complex cases. for example. in thos 40-year-old female patoent who presented following contusion of the maxillary central incisors and right lateral oncosor. it may be advisable to follow the fabricatoon step by step usong a doagnostic waxup.

Fog 7 4 The clonical case presents considerable crowdong. and the treatment plan included possoble orthodontic ontervention. periodontal surgery woth omplants. and prosthetoc restoratoon The lack of space made it necessary to design a specofoc clinocal example that could be shown to the patoent to obtain informed consent for the planned treatment. fogs 7·25 a J 7-26 Two dofferent wax models were proposed, the first made wothout considering orthodontic treatment and the second reflect­ ong a comprehensove treatment plan. onvolvong seroal tooth extractoons and redostrobution of space. Because the central incisors and the right lateral were orreparably lost and there was very loltte peroodontal support. on addition to overcrowdong. the selectoon of the type of rehaboli­ tatoon to propose and then clonocally realoze depended on the optoons chosen in the prelimonary orthodontoc and periodontal plans.

211

Fig 7-27 The clinical orthodontic examination proposed serial extraction of the first premolars to reduce the overcrowding. followed by ortho­ dontic treatment and prosthetic rehabilitation to treat the new spaces. or prosthetic treatment alone. The feasibility of both treatment plans. however. was based on the prosthetic restoration. so the initial clinical diagnosis and the choice of treatment was delayed untol the two pros­ thetic options could be evaluated in the waxups. The difference on the space avaolable in the two options. because of the extractions. provid­ ed the opportunity to create different forms. Fogs 7-28 and 7-2g The lack of periodontal support and the short radicular length steered the choice of treatment toward a more conservative procedure. without additional extractions. The option was for a slower. progressive orthodontic extrusion of the compromised teeth. to pro­ vide more bone and periodontal support for the area afler the extractions. During the stages of slow extrusion. the length of the teeth must be reduced.

Fog 7-30 The compromised teeth were extracted. and the two canines and the lateral incisor were prepared for a prosthesis. After the com­ bined orthodontic and periodontal treatment. the provisional stage was managed using three subsequent provisionals to condition the tissues during the various stages of treatment. using different modalities and procedures. The first provisional was made in the lab. relying on the forms and dimensions represented in the diagnostic waxup. The goal was to restore the esthetics and function of the extracted teeth and con­ dition the tissues in the areas of extraction. Fig 7-31 After allowing an adequate period for healing (about 3 months). during which the condition of the tissues in the extraction areas was controlled and modified several times. a precision polyether impression was taken after positioning a nonimpregnated retraction cord (Ullrapak 000. Ullradent) and completing the finish lines of the preparations to define a reg ular. smooth line. A diamond -grit ball bur was used to redefine the edentulous areas anatomically and esthetically. (A scalpel may also be used.) The new provisional was made using the successive layering of dentin and enamel. creating a resin shell simolar to dentin. cast on a silicone ondex. and fonished woth a bur to give it a natural shape with mamelons. The provisional. properly finished and polished. has been fitted and adapted in the oral cavity. and the esthetic. functional. and phonetic characteristics have been checked.

219

Clinical Considerations for Provisional Prostheses

Figs 7-32 and 7-33 This second-generation provisional. although quite close to the final shape. shows some imperfections that can be easily corrected using white wax directly in the patient's mouth and sending the modifications to the lab after having taken an impression in irre­ versible hydrocolloid.

Figs 7-36 o 7-3g Views before !Figs 7-36 and 7-38) and after !Figs 7-37 and 7-3 g ) treatment. The esthetic outcome of this complex treatment is very goad.

F1g 7-34 Only at this stage should the clinician proceed to finish the tooth preparations. positioning the finish lines at the desired level. and take the impression with elastomerit material.

Fig 7-35 It is important to fabri cate a third-generation provisional that wilt exactly replicate the appearance of the final restoration. This last provisional. once fitted � nd cemented. allows. the patient to check .the esthetic result directly and allows the clinical team to verify all the parameters and the stability of the marg�nal tiSsues. Further mod1f1tallons can be made if necessary. The final restoration in this case was done using a porcelain-fused-to- metal crown. involving a metal support structure made in a single casting. No metal is visible at the mar­ gin because of the use of the collarless technique. wh1th requires a ceramic shoulder margin.

11

21

Clinical Considerations for Provisional Prostheses

Figs 7-32 and 7-33 This second-generation provisional. although quite close to the final shape. shows some imperfections that can be easily corrected using white wax directly in the patient's mouth and sending the modifications to the lab after having taken an impression in irre­ versible hydrocolloid.

Figs 7-36 o 7-3g Views before !Figs 7-36 and 7-38) and after !Figs 7-37 and 7-3 g ) treatment. The esthetic outcome of this complex treatment is very goad.

F1g 7-34 Only at this stage should the clinician proceed to finish the tooth preparations. positioning the finish lines at the desired level. and take the impression with elastomerit material.

Fig 7-35 It is important to fabri cate a third-generation provisional that wilt exactly replicate the appearance of the final restoration. This last provisional. once fitted � nd cemented. allows. the patient to check .the esthetic result directly and allows the clinical team to verify all the parameters and the stability of the marg�nal tiSsues. Further mod1f1tallons can be made if necessary. The final restoration in this case was done using a porcelain-fused-to- metal crown. involving a metal support structure made in a single casting. No metal is visible at the mar­ gin because of the use of the collarless technique. wh1th requires a ceramic shoulder margin.

11

21

CHAPTER 7 Clinical Considerations for Provisional Prostheses

• of removing the provisional prosthesis during the

Using impressions taken in the office (ie, the clas·

first stage, while the resin is still malleable, and care·

sic prefilled·type provisional shells) and those fabri·

fully eliminating excess material using abrasive disks

cated from precision impressions with elastomeric

(eg, from Moore) and part of the interior material

material and usually the aid of a nonimpregnated

using tungsten carbide burs, so that more nuid mate·

denection cord, the authors use the dentin-enamel

rial can be added and the margins can be defined

molding technique. This sandwich technique, which

with precision. By not waiting for the resin to hard·

can be performed both in the office and in the lab,

en completely, the second filling is made easier.

involves two successive pressings. The first uses a

Moreover, the possibility of causing occlusal lifting,

dentin resin, which, after roughing up and reducing

which often results from the alternative technique, is

the shape of the shell, effectively simulates the

eliminated.

properties of natural dentin, with mamelons and

When faced with small defects of marginal or sur·

ridges. The second pressing is done directly over the

face adaptation that require slight repairs, it is

dentin shell, using a very nuid resin mixture com·

advisable to use a dual-curing resin (Unifast, GC},

posed of 70% enamel and 30% transparent resin to

which is ideal for small amounts of material that are

achieve the effect of the incisal characteristics.

then polymerized under blue light. This material has good dimensional stability under stress.'9

Two types of acrylic resin are used in this direct technique. For provisionals made in the laboratory,

The self-curing resin the authors use most often

New Outline resin (Anax Dent) is preferred because

for filling provisionals is Sintodent (Welltrade}, which

of its great versatility and superior esthetic quality,

has many important characteristics, as well as

especially for incisal and translucent effects. Difer·

antibacterial properties20•2 1 provided by the presence

ent color inserts and photopolymerizable transpar·

of benzalkonium chloride, increased hardness, resis·

ent inserts are often interposed between the two

tance to wear, and suitability for polishing. 22 A special

layers (Creative, Kerr Hawe).

eyedropper included with the product is used to mix

Another type of precision provisional involves

the monomer, which is calibrated and produced

making the final prosthesis directly on the definitive

specifically to avoid contamination from the external

impression. To assist the healing and maturation of

environment. The powder and liquid are blended in

the soft tissues after taking the impression, it is

rubber containers, with the liquid added to the pow·

important to achieve precision and good seating of

der rather than vice versa, in quantities 20% less than

the provisional. However, in this stage it is difficult

those used in normal procedures. Mixing time is gen·

to obtain the marginal seal in resin on the prepara·

erally about

t

minute (the material must be mixed

slowly}; the resin mixture is then allowed to sit for about

1.5

minutes until the material achieves ideal

consistency and an opaque, fibrous appearance.

tion immediately after the impression is made. This

7-44

7-45

obstacle can be avoided by using third-generation provisionals made from the definitive impression. Second-generation provisionals are made on a

This resin is also used in procedures involving the

stone cast developed from an elastomeric Impression

pressing of the thermoplastic and silicone Indices, in

created after vertically retracting the soft tissues with

which a considerable amount of resin is used. For this

a nonimpregnated denection cord (Uitrapak ooo}, using

reason, the work is performed in the clinician's office.

the sandwich technique. After the fitting, however, it ..

F , 7-40 and 7-41 Construction of a long-term provisional restoration using a g o l d reinforcing structure that includes s o m e occlusal support points to stabilize occlusion and prevent breakage under masticatory loads.

f1g 7-42 first-generation provisional or shell with a silicone index for positioning in the oral cavity. shown on the stone cast. fig 7-43 After the tooth is prepared. it is Immediately isolated with a film of liquid soap before f illi n g .

�,g 7·4 Provisional filling. The acrylic resin is overflowing after insertion and must still be adapted optimally to the f1nish line

Hg 7· 5 First rough1ng of the resin. us1ng a tungsten carbide bur. after the Initial filling. tak1ng care to remove only the inter�or of the walls and the excess marginal material.

223

CHAPTER 7 Clinical Considerations for Provisional Prostheses

• of removing the provisional prosthesis during the

Using impressions taken in the office (ie, the clas·

first stage, while the resin is still malleable, and care·

sic prefilled·type provisional shells) and those fabri·

fully eliminating excess material using abrasive disks

cated from precision impressions with elastomeric

(eg, from Moore) and part of the interior material

material and usually the aid of a nonimpregnated

using tungsten carbide burs, so that more nuid mate·

denection cord, the authors use the dentin-enamel

rial can be added and the margins can be defined

molding technique. This sandwich technique, which

with precision. By not waiting for the resin to hard·

can be performed both in the office and in the lab,

en completely, the second filling is made easier.

involves two successive pressings. The first uses a

Moreover, the possibility of causing occlusal lifting,

dentin resin, which, after roughing up and reducing

which often results from the alternative technique, is

the shape of the shell, effectively simulates the

eliminated.

properties of natural dentin, with mamelons and

When faced with small defects of marginal or sur·

ridges. The second pressing is done directly over the

face adaptation that require slight repairs, it is

dentin shell, using a very nuid resin mixture com·

advisable to use a dual-curing resin (Unifast, GC},

posed of 70% enamel and 30% transparent resin to

which is ideal for small amounts of material that are

achieve the effect of the incisal characteristics.

then polymerized under blue light. This material has good dimensional stability under stress.'9

Two types of acrylic resin are used in this direct technique. For provisionals made in the laboratory,

The self-curing resin the authors use most often

New Outline resin (Anax Dent) is preferred because

for filling provisionals is Sintodent (Welltrade}, which

of its great versatility and superior esthetic quality,

has many important characteristics, as well as

especially for incisal and translucent effects. Difer·

antibacterial properties20•2 1 provided by the presence

ent color inserts and photopolymerizable transpar·

of benzalkonium chloride, increased hardness, resis·

ent inserts are often interposed between the two

tance to wear, and suitability for polishing. 22 A special

layers (Creative, Kerr Hawe).

eyedropper included with the product is used to mix

Another type of precision provisional involves

the monomer, which is calibrated and produced

making the final prosthesis directly on the definitive

specifically to avoid contamination from the external

impression. To assist the healing and maturation of

environment. The powder and liquid are blended in

the soft tissues after taking the impression, it is

rubber containers, with the liquid added to the pow·

important to achieve precision and good seating of

der rather than vice versa, in quantities 20% less than

the provisional. However, in this stage it is difficult

those used in normal procedures. Mixing time is gen·

to obtain the marginal seal in resin on the prepara·

erally about

t

minute (the material must be mixed

slowly}; the resin mixture is then allowed to sit for about

1.5

minutes until the material achieves ideal

consistency and an opaque, fibrous appearance.

tion immediately after the impression is made. This

7-44

7-45

obstacle can be avoided by using third-generation provisionals made from the definitive impression. Second-generation provisionals are made on a

This resin is also used in procedures involving the

stone cast developed from an elastomeric Impression

pressing of the thermoplastic and silicone Indices, in

created after vertically retracting the soft tissues with

which a considerable amount of resin is used. For this

a nonimpregnated denection cord (Uitrapak ooo}, using

reason, the work is performed in the clinician's office.

the sandwich technique. After the fitting, however, it ..

F , 7-40 and 7-41 Construction of a long-term provisional restoration using a g o l d reinforcing structure that includes s o m e occlusal support points to stabilize occlusion and prevent breakage under masticatory loads.

f1g 7-42 first-generation provisional or shell with a silicone index for positioning in the oral cavity. shown on the stone cast. fig 7-43 After the tooth is prepared. it is Immediately isolated with a film of liquid soap before f illi n g .

�,g 7·4 Provisional filling. The acrylic resin is overflowing after insertion and must still be adapted optimally to the f1nish line

Hg 7· 5 First rough1ng of the resin. us1ng a tungsten carbide bur. after the Initial filling. tak1ng care to remove only the inter�or of the walls and the excess marginal material.

223

CHAPTER 7 Clinical Considerations for Provisional Prostheses

�

may be necessary to fill up one or more prepared

The provisional prosthesis serves an im portant

teeth to improve adaptation of the prosthesis and

role in the conditioning of the soft tissues. It also

ensure its stability. This is principally due to the resin

provides

shrinkage. This provisional, which replaced the first

esthetics. The clinician must fully exploit the oppor­

information

regarding

occlusion

and

provisional or shell provisional in an intermediate

tunities provided by the provisional restoration to

stage of treatment, must be filled after the impres­

achieve the final objective (Figs 7-6o to 7-82).

sion has been taken if the marginal level is to be

A provisional prosthesis represents a great

deepened or modified.

opportunity for conditioning and supporting the gin­

Finishing

whether after surgery or after preparation. Shaping

gival tissues. It also permits proper maturation, and modiying the tissues without surgery in an

To finish the provisional prosthesis, tungsten car­

atraumatic manner can be accomplished for small

bide burs are used for progressive roughening of the

modifications, such as shaping and positioning the

margins and the elimination of excess material (Figs

gingival contour, by using provisional prostheses

7-48 to 7-53), assisted by an abrasive disk or an

that have been properly conditioned on the plaster

intercalary cut bur in the interproximal areas.

cast by the dental technician (Fig 7-83).

For polishing, silicone rubber points and wheels

Therefore, tissue conditioning may involve one or

are used first (Fig 7-54), followed by goat-hair brush­

more edentulous areas to create a natural prosthe­

es dipped in powdered pumice and a wool brush

sis with ovate panties.

soaked in polishing paste (Figs 7-55 and 7-56).

Achieving this result in an edentulous area is pos­

Polishing is always completed by a pass with a

sible only through proper conditioning of the gingi­

mechanical polisher (Figs 7-57 to 7-59).

val tissue, which is prepared using a rotating hand­ piece with a round diamond bur or a radioscalpel with a lozenge-shaped tip (Figs 7-84 to 7-88) .

TISSUE CON DITI O N I N G WITH THE PROVISIONAL PROSTH ESIS

When this procedure is carried out, at least

2

mm

of gingival tissue must remain between the most apical point of the prepared tissue and the bone

Provisional restorations have various time and

crest to avoid unwanted compression and decubitis

modality constraints, depending on the functions

lesions, which would threaten the health of the tis­

and goals of the treatment, that is, whether it is pri­

sue and could result in chronic bone innammation

marily an esthetic rehabilitation or a postsurgical,

and possible osteolysis.

..

functional operation.

Figs 7-46 and 7-47 Second filling with more liquid resin. keeping the provisional inside the index. The besl technique is to not wait for the resin to harden completely. but to reinsert i t while it is still malleable in order to avoid the occlusal lifting phenomenon. Removal before it is fully hardened prevents close adhesion to the prepared tooth and the consequent difficult detachment. Fig 7 ll The finishing stage begins with the removal of the excess material accumulated at the margin. using a straight handpiece and a tab­ oratory tungsten carbide bur IH13HF.104.023 and H l J g _ F$0.023. Komell Fl1• 7-4� id 7 iO The next step is a pass with the longest bur IH261.EF.104.023). which is more practical in the profile area.

F; 7- 1 nc 7· 52 Having removed the extra resin after filling. a wax crayon is used to highlight where the resin border will contact the finish line in the intrasulcular zone. The prosthetic margin will have to be carefully poliShed and finished.

m

CHAPTER 7 Clinical Considerations for Provisional Prostheses

�

may be necessary to fill up one or more prepared

The provisional prosthesis serves an im portant

teeth to improve adaptation of the prosthesis and

role in the conditioning of the soft tissues. It also

ensure its stability. This is principally due to the resin

provides

shrinkage. This provisional, which replaced the first

esthetics. The clinician must fully exploit the oppor­

information

regarding

occlusion

and

provisional or shell provisional in an intermediate

tunities provided by the provisional restoration to

stage of treatment, must be filled after the impres­

achieve the final objective (Figs 7-6o to 7-82).

sion has been taken if the marginal level is to be

A provisional prosthesis represents a great

deepened or modified.

opportunity for conditioning and supporting the gin­

Finishing

whether after surgery or after preparation. Shaping

gival tissues. It also permits proper maturation, and modiying the tissues without surgery in an

To finish the provisional prosthesis, tungsten car­

atraumatic manner can be accomplished for small

bide burs are used for progressive roughening of the

modifications, such as shaping and positioning the

margins and the elimination of excess material (Figs

gingival contour, by using provisional prostheses

7-48 to 7-53), assisted by an abrasive disk or an

that have been properly conditioned on the plaster

intercalary cut bur in the interproximal areas.

cast by the dental technician (Fig 7-83).

For polishing, silicone rubber points and wheels

Therefore, tissue conditioning may involve one or

are used first (Fig 7-54), followed by goat-hair brush­

more edentulous areas to create a natural prosthe­

es dipped in powdered pumice and a wool brush

sis with ovate panties.

soaked in polishing paste (Figs 7-55 and 7-56).

Achieving this result in an edentulous area is pos­

Polishing is always completed by a pass with a

sible only through proper conditioning of the gingi­

mechanical polisher (Figs 7-57 to 7-59).

val tissue, which is prepared using a rotating hand­ piece with a round diamond bur or a radioscalpel with a lozenge-shaped tip (Figs 7-84 to 7-88) .

TISSUE CON DITI O N I N G WITH THE PROVISIONAL PROSTH ESIS

When this procedure is carried out, at least

2

mm

of gingival tissue must remain between the most apical point of the prepared tissue and the bone

Provisional restorations have various time and

crest to avoid unwanted compression and decubitis

modality constraints, depending on the functions

lesions, which would threaten the health of the tis­

and goals of the treatment, that is, whether it is pri­

sue and could result in chronic bone innammation

marily an esthetic rehabilitation or a postsurgical,

and possible osteolysis.

..

functional operation.

Figs 7-46 and 7-47 Second filling with more liquid resin. keeping the provisional inside the index. The besl technique is to not wait for the resin to harden completely. but to reinsert i t while it is still malleable in order to avoid the occlusal lifting phenomenon. Removal before it is fully hardened prevents close adhesion to the prepared tooth and the consequent difficult detachment. Fig 7 ll The finishing stage begins with the removal of the excess material accumulated at the margin. using a straight handpiece and a tab­ oratory tungsten carbide bur IH13HF.104.023 and H l J g _ F$0.023. Komell Fl1• 7-4� id 7 iO The next step is a pass with the longest bur IH261.EF.104.023). which is more practical in the profile area.

F; 7- 1 nc 7· 52 Having removed the extra resin after filling. a wax crayon is used to highlight where the resin border will contact the finish line in the intrasulcular zone. The prosthetic margin will have to be carefully poliShed and finished.

m

CHAPTER 7 Clinical Considerations for Provisional Prostheses

..

The presence of the papillae is fundamental to the simulation of a natural prosthesis, and this is

the papillae rather than letting the soft tissues con­ tract to close the gap.

possible only if the embrasures are modified with

The length of the ovate pontic should be about

several applications of acrylic resin in order to sup­

2.5 mm so that the correct amount is positioned in

port the soft tissue (Rgs 7-89 to 7-91). The ideal

the interproximal area. This length is necessary to

shape of the papillae can be achieved only with the

provide sufficient support for the papillae.

proper provisional, which should have an interprox­

Yet another procedure to improve the appearance

imal point of contact as far apical as possible. It is

of the tissue is closing the interproximal black trian­

only when the distance between this point and the

gles. The papillae can be stimulated using tools like

bone crest is equal to or less than

5

mm that the

the scaler (M23, Hu-Friedy) approximately every 15

Another method for achieving proper tissue con­

point of contact and the bone crest within the limits

outcome can be reliably predicted. 'l ditioning is to insert a false root made of acrylic

FIG 7-53

FIG 7-54

FIG 7-56

FIG 7-57

FIG 7-55

days, making sure to keep the distance between the recommended by Tarnow et al'l (Rgs 7-92 to 7-99). •

resin immediately into the extraction site to guide

M A X I M U M F O R

O F

L E V E L

P R O V I S I O N A L

R E S T O R A T I O N S

fig 7-5J The smaU tungsten carbide bur IH7HF.014. Komel) enables the technician to get closer to the margin because of its smaller d1mens1ons and greater control. wh1ch are ideal characteristics for finishing this delicate area. fig 7-4 The polishing stage begins with a self-polishing silicone rubber tip (No. g 557, Komel). Figs 7-55 and 7-iiA goat-hair brush soaked in powdered pumice paste and the wool brush soaked in polishing liquid. fig 7-57 The margin shown at low magnification. properly finished and polished.

Figs 7-58 and 7-� In these two high- magnification images. the excellent finishing of the margin of the provisional restoration ca n be seen. as can the detail created in the shoulder. Also note the compactness and adaptation of the provisional and its . fa1thful reproduction of the charactenshcs of the preparation.

1

FIG 7-58

P R E C I S I O N

FIG 7-59

CHAPTER 7 Clinical Considerations for Provisional Prostheses

..

The presence of the papillae is fundamental to the simulation of a natural prosthesis, and this is

the papillae rather than letting the soft tissues con­ tract to close the gap.

possible only if the embrasures are modified with

The length of the ovate pontic should be about

several applications of acrylic resin in order to sup­

2.5 mm so that the correct amount is positioned in

port the soft tissue (Rgs 7-89 to 7-91). The ideal

the interproximal area. This length is necessary to

shape of the papillae can be achieved only with the

provide sufficient support for the papillae.

proper provisional, which should have an interprox­

Yet another procedure to improve the appearance

imal point of contact as far apical as possible. It is

of the tissue is closing the interproximal black trian­

only when the distance between this point and the

gles. The papillae can be stimulated using tools like

bone crest is equal to or less than

5

mm that the

the scaler (M23, Hu-Friedy) approximately every 15

Another method for achieving proper tissue con­

point of contact and the bone crest within the limits

outcome can be reliably predicted. 'l ditioning is to insert a false root made of acrylic

FIG 7-53

FIG 7-54

FIG 7-56

FIG 7-57

FIG 7-55

days, making sure to keep the distance between the recommended by Tarnow et al'l (Rgs 7-92 to 7-99). •

resin immediately into the extraction site to guide

M A X I M U M F O R

O F

L E V E L

P R O V I S I O N A L

R E S T O R A T I O N S

fig 7-5J The smaU tungsten carbide bur IH7HF.014. Komel) enables the technician to get closer to the margin because of its smaller d1mens1ons and greater control. wh1ch are ideal characteristics for finishing this delicate area. fig 7-4 The polishing stage begins with a self-polishing silicone rubber tip (No. g 557, Komel). Figs 7-55 and 7-iiA goat-hair brush soaked in powdered pumice paste and the wool brush soaked in polishing liquid. fig 7-57 The margin shown at low magnification. properly finished and polished.

Figs 7-58 and 7-� In these two high- magnification images. the excellent finishing of the margin of the provisional restoration ca n be seen. as can the detail created in the shoulder. Also note the compactness and adaptation of the provisional and its . fa1thful reproduction of the charactenshcs of the preparation.

1

FIG 7-58

P R E C I S I O N

FIG 7-59

i tl,·l

I

Clinical Considerations for Provisional Prostheses

Fig 7 60 Clinical case of a 34-year-old male patient who was greatly dissatisfied with his provisional. which was made in another clinic. and wanted to recover the function and esthetics lost following the extraction of the maxillary right central incisor for endodontic reasons. F1g 7-61 and 7·62 The clinical and radiologic examinations of the teeth. already reduced for prosthetic purposes. showed a false path on the right lateral 1ncisor. the presence of an incongruous restoration on the left central incisor. and a carbon fiber post on the left lateral incisor. The in1t1al approach involved the endodontic aspect. with resolutiOn of the false path of the right lateral inCISor and the re-treatment of the left central incisor. F1g 7-63 The provisional presented obvious esthetic defects and is clearly unatlractive because of the gross mismatch in the gingival levels.

1

F1g 7·64 Removal of the provisional reveals even more clearly the asymmetry in the positioning of the restorative teeth. The inadequacy of the forms and height of the prepared teeth can be observed. F1gs 7-65 and 7-66 Initial waxup on the plaster cast. used to formulate a realistic surgical-prosthetic treatment plan.

F1gs 7-67 and 7-68 Preproslhelic surgery reshapes I he bone contours and lhe mucogin � ival defect in lhe edentulous area in a single stage. This resull is obtained with a crown-lengthening procedure and a subepithelial connective t1ssue graft drawn from the palate. F1gs 7-6g and 7·70 Occlusal views of pre- and postoperative conditions.

F1g 7·71 SuccesSIVe preproslhetiC reconstructiOn wilh compoSite res1n.

i tl,·l

I

Clinical Considerations for Provisional Prostheses

Fig 7 60 Clinical case of a 34-year-old male patient who was greatly dissatisfied with his provisional. which was made in another clinic. and wanted to recover the function and esthetics lost following the extraction of the maxillary right central incisor for endodontic reasons. F1g 7-61 and 7·62 The clinical and radiologic examinations of the teeth. already reduced for prosthetic purposes. showed a false path on the right lateral 1ncisor. the presence of an incongruous restoration on the left central incisor. and a carbon fiber post on the left lateral incisor. The in1t1al approach involved the endodontic aspect. with resolutiOn of the false path of the right lateral inCISor and the re-treatment of the left central incisor. F1g 7-63 The provisional presented obvious esthetic defects and is clearly unatlractive because of the gross mismatch in the gingival levels.

1

F1g 7·64 Removal of the provisional reveals even more clearly the asymmetry in the positioning of the restorative teeth. The inadequacy of the forms and height of the prepared teeth can be observed. F1gs 7-65 and 7-66 Initial waxup on the plaster cast. used to formulate a realistic surgical-prosthetic treatment plan.

F1gs 7-67 and 7-68 Preproslhelic surgery reshapes I he bone contours and lhe mucogin � ival defect in lhe edentulous area in a single stage. This resull is obtained with a crown-lengthening procedure and a subepithelial connective t1ssue graft drawn from the palate. F1gs 7-6g and 7·70 Occlusal views of pre- and postoperative conditions.

F1g 7·71 SuccesSIVe preproslhetiC reconstructiOn wilh compoSite res1n.

CHAIII' ! Climcal Considerations for Provisional Prostheses

Figs 7-72 and 7-73 Comparison of the initial situation and that after the endodontic. periodontal. and restorative stages. showing the excellent clinical result achieved. Fo.g 1·74 Two months later. it was. possible to make a new. second-generatoon provisional based on the modified anatomy. The change in the gongoval and dental parameters os evodent. on terms of the wodth-length ratios (the ideal ratio for central incisors is 0.75-0.80). Fog 7-75 Provisional and maturong toss � es The papillae must continue to adapt in relation to the provisional The excellent esthetics achieved . •n the promoonal and good communiCation were fundamental on obta1n1ng the patient's informed consent. especially considering the new tooth lengths

Figs 7-78 and 7-79 O cclusal and palatal views of the provisional . showing resolution of the gingival defect in relation to the right central incisor and excellent integration with the tissue. even in the palatal area. Figs 7-80 and 7-81 Condition of the case with the initial provisional and 6 months after surgical treatment and maturation of the soft tissues. guided by a new provisional prosthesis

Fog 7-82 Control radiograph after placement of the final prosthesis Ia zirconium !lava. J M Espel fixed dental prosthesis). showing clinical healing from endodontic treatment.

Fogs 7·76 ao d 7-77 Details of the provisional In the lateral mws

20

231

CHAIII' ! Climcal Considerations for Provisional Prostheses

Figs 7-72 and 7-73 Comparison of the initial situation and that after the endodontic. periodontal. and restorative stages. showing the excellent clinical result achieved. Fo.g 1·74 Two months later. it was. possible to make a new. second-generatoon provisional based on the modified anatomy. The change in the gongoval and dental parameters os evodent. on terms of the wodth-length ratios (the ideal ratio for central incisors is 0.75-0.80). Fog 7-75 Provisional and maturong toss � es The papillae must continue to adapt in relation to the provisional The excellent esthetics achieved . •n the promoonal and good communiCation were fundamental on obta1n1ng the patient's informed consent. especially considering the new tooth lengths

Figs 7-78 and 7-79 O cclusal and palatal views of the provisional . showing resolution of the gingival defect in relation to the right central incisor and excellent integration with the tissue. even in the palatal area. Figs 7-80 and 7-81 Condition of the case with the initial provisional and 6 months after surgical treatment and maturation of the soft tissues. guided by a new provisional prosthesis

Fog 7-82 Control radiograph after placement of the final prosthesis Ia zirconium !lava. J M Espel fixed dental prosthesis). showing clinical healing from endodontic treatment.

Fogs 7·76 ao d 7-77 Details of the provisional In the lateral mws

20

231

Clinical Considerations for Provisional Prostheses

f1g 7 83 The prov isional may act as a guid � to modify the profile and the relationship with the gingival tissue. for example. in the shifting of _ _ wh1ch. when moved d1stally. confers a more natural appearance. To achieve this. the dental technician must remove the the g1ng1val zenlth. portion o'. ging1val ti�sue involved from the plaster cut. This will be replaced by the resin of the provisional restoration. thus effecting a _ compression and a sltght 1schem1a of the t1ssues. wh1ch w1ll mature and adapt to the new situation. flg> 7-4ald 7-85 The edentulous aru occupied. by the prosthetic restoration must be well adapted to the mucosal tissue lie. an ovate pontic). favorable adaptalton can be obtatned only 1f the area 1s prepared with a bur. or with other techniques and instruments such as the _ presents an ovate shape at the point where it contacts the gingiva. rad1oscalpet. and 1f the prov1s1onal

figs 7-89 and 7-90 The same clinical case during different phases of treatment. Embrasures are evident between three teeth that will be sub­ sequently restored with ceramic restorations. The provisional is made using a direct technique with preformed shells and will later be replaced with a second-generation provisional. made by means of a polyether precision impression with horizontal displacement established by a nonimpre 9 nated retraction cord. Closure of the embrasures between the provisionals is achieved with a direct technique. by adding dual-curing acrylic resin IU nifast) lfig 7-901. f1g 7-91 Note the full maturation of the papillae following cementation of the feldspathic ceramic crowns.

F11 s 7·86 a 1d 7-87 The edentulous portion that Will be 1n contact w1th the provisional must be usy to clean and accessible with Superfloss !Oral BJ. ftg 7· The area. properly conditioned. tan stmulate the presence of a root and mask the absence of the natural tooth.

23

Clinical Considerations for Provisional Prostheses

f1g 7 83 The prov isional may act as a guid � to modify the profile and the relationship with the gingival tissue. for example. in the shifting of _ _ wh1ch. when moved d1stally. confers a more natural appearance. To achieve this. the dental technician must remove the the g1ng1val zenlth. portion o'. ging1val ti�sue involved from the plaster cut. This will be replaced by the resin of the provisional restoration. thus effecting a _ compression and a sltght 1schem1a of the t1ssues. wh1ch w1ll mature and adapt to the new situation. flg> 7-4ald 7-85 The edentulous aru occupied. by the prosthetic restoration must be well adapted to the mucosal tissue lie. an ovate pontic). favorable adaptalton can be obtatned only 1f the area 1s prepared with a bur. or with other techniques and instruments such as the _ presents an ovate shape at the point where it contacts the gingiva. rad1oscalpet. and 1f the prov1s1onal

figs 7-89 and 7-90 The same clinical case during different phases of treatment. Embrasures are evident between three teeth that will be sub­ sequently restored with ceramic restorations. The provisional is made using a direct technique with preformed shells and will later be replaced with a second-generation provisional. made by means of a polyether precision impression with horizontal displacement established by a nonimpre 9 nated retraction cord. Closure of the embrasures between the provisionals is achieved with a direct technique. by adding dual-curing acrylic resin IU nifast) lfig 7-901. f1g 7-91 Note the full maturation of the papillae following cementation of the feldspathic ceramic crowns.

F11 s 7·86 a 1d 7-87 The edentulous portion that Will be 1n contact w1th the provisional must be usy to clean and accessible with Superfloss !Oral BJ. ftg 7· The area. properly conditioned. tan stmulate the presence of a root and mask the absence of the natural tooth.

23

Clinical Considerations for Provisional Prostheses

7- 9 8

Fig 7-92 The papillae must be stimulated because thw maturatiOn is not yet complete, this can be done mechanically using a scaler IM231 in the area of the papillae in contact with the provisional prosthesis igs 7-3 and 7-4 Mechanical stimulation of papillae

Figs 7-98 and 7- g9 Magnification of the final restorations i n the same patient.

Fig 7-95 Clinical aspect immediately following mechanical stimulallon

F1gs 7 96 a•d 7-97 The f1nal restorations '" the same pat�ent. after penodontal-prosthet1c treatment

lJS

Clinical Considerations for Provisional Prostheses

7- 9 8

Fig 7-92 The papillae must be stimulated because thw maturatiOn is not yet complete, this can be done mechanically using a scaler IM231 in the area of the papillae in contact with the provisional prosthesis igs 7-3 and 7-4 Mechanical stimulation of papillae

Figs 7-98 and 7- g9 Magnification of the final restorations i n the same patient.

Fig 7-95 Clinical aspect immediately following mechanical stimulallon

F1gs 7 96 a•d 7-97 The f1nal restorations '" the same pat�ent. after penodontal-prosthet1c treatment

lJS

CHAPTER 7 Clinical Considerations for Provisional Prostheses

8. Tjan AH. Tjan AH, Grant BE. Marginal accuracy of ten·

REFEREN CES t. Harrison JD. Efect of retraction materials on the gingi­ val sulcus epithelium. J Prosthet Dent t96t;11:514. 2. loe H, Silness 1. Tissue reactions to string packs used in fixed restorations. I Prosthet Dent 1963:t):)t8. 3- Dragoo MR, Williams GB. Periodontal tissue reactions to restorative procedures. Part II. lnt 1 Periodontics Restor­ ative Dent 1982;2:34-45.

SE. Fundamentals of Rxed Prosthodontics, ed 3. Chi· cage: Quintessence, 1997-

417-421.

Assoc 1998;26:121-127.

9· Christensen Gl. Provisional restorations for fixed prosth· odontics. l Am Dent Assoc 1996;127:249-252. to. Moulding MB. Teplitsky PE. lntrapulpal temperature dur· ing direct fabrication of provisional restorations. tnt I Prosthodont 1990:3:299-304.

crowns fabricated from six proprietary provisional mate­ rials.

performance and periodontal outcome of temporary crowns and ixed partial dentures: A randomized clinical trial. J Prosthet Dent 2000;83:32-39. 6. Donaldson D. Gingival recession associated with tem­ porary coverage. J Periodontal 1973:44:691�6. 7. Donaldson 0. The etioloy of gingival recession associ­

l Periodontol t974:45:46B.

I

Cal Dent

t6. Ogawa . Aizawa S, Tanaka M. Matsuya S, Hasegawa A, Koyano K. Efect of water temperature on the fit of

l Prosthet Dent 1997;77:482-485.

the pulp chamber during abrication of provisional crowns. J Prosthet Dent 19B9;62:622�26.

R. Antibacterial activity of a resin: A qualitative study. J

17. Yuodelis RA, Faucher R. Provisional restorations: An

22. Albergo G, Sampalmieri F, Mattioli Belmonte M, Andre·

integrated approach to periodontics and restorative

ana S. Mechanical performance of some dental acrylic

dentisty. Dent Clin North Am t980;24:285-303.

niques on intrapulpal temperature during direct abrica·

tance from the contact point to the crest of bone on the presence or absence of the interproximal dental papil­

I

Prosthodont 1991;

4:332-336.

Efects of occlusal loading and thermocycling on the

14. Hung CM, Weiner S. Dastane A, Vaidyanathan TK. Efects

ized resin provisional crowns. J Prosthet Dent 1999;

of thermocycling and occlusal force on the margins of provisional acrylic

resin

crowns.

1

Prosthet

resin. J Dent Res t997:76(s):1103. 23. Tarnow DP, Magner AW, Fletcher P. The efect of the dis·

tion of provisional restorations. lnt

I

Prosthet Dent 1991;65:642�46.

1997:76(special issue):279. 21. (apelli M, Albergo G, Casolari L, Sampalmieri F, Bedini

Dent Res 1998:77:1389.

19. Dubois R), Kyriakakis P, Weiner S, Vaidyanathan TK.

on the margins of transitional acrylic resin crowns.

S. Efect of antimicrobical ingredients on mechanical performance in acrylic resin !abstract 2128]. J Dent Res

Prosthet Dent 1999:82:658661.

1. Weiner S, Berendsen P. Efects of thermocyc\ing

13. Blum

20. Albergo G, Accarisi E, Sampalmieri F, Bedini R, Andreana

provisional crown margins during polymerization. I

t8. Moulding MB, Loney RW. The efect of cooling tech·

12. Tjan AH, Grant BE, Godfrey MF Jrd. Temperature rise in

5· Luthardt RG, Stossel M, Hinz M, Volland! R. Clinical

ated with temporay crowns.

with bonded porcelain laminate veneers.

tt. Tjan AH, Castelnuovo ). Shiatsu G. Marginal fidelity of

4. Shillingburg HT, Hobo S. Whitsett LD, Jacobi R, Brackett

15. Cho GC, Donovan TE, Chee WWL. Clinical experiences

porary composite crowns. J Prosthet Dent 1987;58:

la.

l Periodontal 1992;63:995996.

marginal gaps of light-polymerized and autopolymer·

82:t6t-t66.

Dent

1993:69:573-577·

21

237

CHAPTER 7 Clinical Considerations for Provisional Prostheses

8. Tjan AH. Tjan AH, Grant BE. Marginal accuracy of ten·

REFEREN CES t. Harrison JD. Efect of retraction materials on the gingi­ val sulcus epithelium. J Prosthet Dent t96t;11:514. 2. loe H, Silness 1. Tissue reactions to string packs used in fixed restorations. I Prosthet Dent 1963:t):)t8. 3- Dragoo MR, Williams GB. Periodontal tissue reactions to restorative procedures. Part II. lnt 1 Periodontics Restor­ ative Dent 1982;2:34-45.

SE. Fundamentals of Rxed Prosthodontics, ed 3. Chi· cage: Quintessence, 1997-

417-421.

Assoc 1998;26:121-127.

9· Christensen Gl. Provisional restorations for fixed prosth· odontics. l Am Dent Assoc 1996;127:249-252. to. Moulding MB. Teplitsky PE. lntrapulpal temperature dur· ing direct fabrication of provisional restorations. tnt I Prosthodont 1990:3:299-304.

crowns fabricated from six proprietary provisional mate­ rials.

performance and periodontal outcome of temporary crowns and ixed partial dentures: A randomized clinical trial. J Prosthet Dent 2000;83:32-39. 6. Donaldson D. Gingival recession associated with tem­ porary coverage. J Periodontal 1973:44:691�6. 7. Donaldson 0. The etioloy of gingival recession associ­

l Periodontol t974:45:46B.

I

Cal Dent

t6. Ogawa . Aizawa S, Tanaka M. Matsuya S, Hasegawa A, Koyano K. Efect of water temperature on the fit of

l Prosthet Dent 1997;77:482-485.

the pulp chamber during abrication of provisional crowns. J Prosthet Dent 19B9;62:622�26.

R. Antibacterial activity of a resin: A qualitative study. J

17. Yuodelis RA, Faucher R. Provisional restorations: An

22. Albergo G, Sampalmieri F, Mattioli Belmonte M, Andre·

integrated approach to periodontics and restorative

ana S. Mechanical performance of some dental acrylic

dentisty. Dent Clin North Am t980;24:285-303.

niques on intrapulpal temperature during direct abrica·

tance from the contact point to the crest of bone on the presence or absence of the interproximal dental papil­

I

Prosthodont 1991;

4:332-336.

Efects of occlusal loading and thermocycling on the

14. Hung CM, Weiner S. Dastane A, Vaidyanathan TK. Efects

ized resin provisional crowns. J Prosthet Dent 1999;

of thermocycling and occlusal force on the margins of provisional acrylic

resin

crowns.

1

Prosthet

resin. J Dent Res t997:76(s):1103. 23. Tarnow DP, Magner AW, Fletcher P. The efect of the dis·

tion of provisional restorations. lnt

I

Prosthet Dent 1991;65:642�46.

1997:76(special issue):279. 21. (apelli M, Albergo G, Casolari L, Sampalmieri F, Bedini

Dent Res 1998:77:1389.

19. Dubois R), Kyriakakis P, Weiner S, Vaidyanathan TK.

on the margins of transitional acrylic resin crowns.

S. Efect of antimicrobical ingredients on mechanical performance in acrylic resin !abstract 2128]. J Dent Res

Prosthet Dent 1999:82:658661.

1. Weiner S, Berendsen P. Efects of thermocyc\ing

13. Blum

20. Albergo G, Accarisi E, Sampalmieri F, Bedini R, Andreana

provisional crown margins during polymerization. I

t8. Moulding MB, Loney RW. The efect of cooling tech·

12. Tjan AH, Grant BE, Godfrey MF Jrd. Temperature rise in

5· Luthardt RG, Stossel M, Hinz M, Volland! R. Clinical

ated with temporay crowns.

with bonded porcelain laminate veneers.

tt. Tjan AH, Castelnuovo ). Shiatsu G. Marginal fidelity of

4. Shillingburg HT, Hobo S. Whitsett LD, Jacobi R, Brackett

15. Cho GC, Donovan TE, Chee WWL. Clinical experiences

porary composite crowns. J Prosthet Dent 1987;58:

la.

l Periodontal 1992;63:995996.

marginal gaps of light-polymerized and autopolymer·

82:t6t-t66.

Dent

1993:69:573-577·

21

237

C H A P T E R

8

TE C H N I C AL C O N S I D ERAT I O N S F O R P R O V I S I O NAL P R O S T H E S E S

D IAGNOSITIC PROVISIO NAL

and with the patient's unique individual features,

ELEMENTS

such as the smile, face, and personality. Modern treatment abandons the traditional concept

The provisional prosthesis plays a fundamental part

preparing a provisional prosthesis of mediocre or

in various phases of the prosthetic rehabilitation

poor quality and later replacing it with an improved

treatment, particularly when many teeth are involved

ceramic prosthesis. Treatment must address the ini­

and the patient's occlusal scheme requires dramatic

tial clinical situation in propotion to its complexity,

change.

starting with a diagnostic waxup, which leads to fab­

A patient may feel uncomfortable with the func­

rication of a provisional restoration that incorporates

tion of a provisional prosthesis, with the esthetics,

function and esthetics. Both of these requirements

or both. However, provisionalization constitutes a

transmit essential diagnostic information for the

crucial phase in the overall treatment, and the clini­

definitive restoration.

cian must try to make the patient as comfortable

The diagnostic waxup may be converted initially

with it as possible. All members of the prosthetic

into an acrylic resin provisional prosthesis that is

team should approach this early phase of treatment

used to analyze and verify the proposed parameters

as an opportunity to establish and strengthen a

and determine necessary changes in shape or color

mutually positive relationship with the patient.'

Flu 8-1

FIG 8-2

of

TEC H N I CAL

D IAG NO STIC

A N D

before the ceramic restoration is fabricated. This vey

Complex esthetic restorations require a precise

crucial phase requires cooperation among all mem­

therapeutic approach to ensure that the definitive

bers of the prosthetic team to synthesize what they

restoration harmonizes with the surrounding tissues

know of the patient's character and communicate this .

Fig 8-1 Provisional diagnostic mock-up constructed directly in the patient's mouth. The teeth are isolated by the clinician using liquid glycerin or normal liquid soap to ensure the resin can be more readily detached from the prepared teeth.

Fig 8-2 Silicone matrix filled with acrylic rem in the plastic phase. The clinician uses the silicone index implemented on the diagnostic waxup as a matrix to mold the diagnostic mock-up on the teeth for which the provisional restorations are being prepared. Fig 8-3 Immediate appearance of the resin after direct polymerization and subsequent extraction of the silicone matrix. The acrylic material will be detached later using hand tools. Fig 8-4 Slack demarcations Indicating corrections to improve the anatomy of the mock-up teeth.

1

FIG 8-3

FIG 8-4

ESTH ETI C

APPROACH

C H A P T E R

8

TE C H N I C AL C O N S I D ERAT I O N S F O R P R O V I S I O NAL P R O S T H E S E S

D IAGNOSITIC PROVISIO NAL

and with the patient's unique individual features,

ELEMENTS

such as the smile, face, and personality. Modern treatment abandons the traditional concept

The provisional prosthesis plays a fundamental part

preparing a provisional prosthesis of mediocre or

in various phases of the prosthetic rehabilitation

poor quality and later replacing it with an improved

treatment, particularly when many teeth are involved

ceramic prosthesis. Treatment must address the ini­

and the patient's occlusal scheme requires dramatic

tial clinical situation in propotion to its complexity,

change.

starting with a diagnostic waxup, which leads to fab­

A patient may feel uncomfortable with the func­

rication of a provisional restoration that incorporates

tion of a provisional prosthesis, with the esthetics,

function and esthetics. Both of these requirements

or both. However, provisionalization constitutes a

transmit essential diagnostic information for the

crucial phase in the overall treatment, and the clini­

definitive restoration.

cian must try to make the patient as comfortable

The diagnostic waxup may be converted initially

with it as possible. All members of the prosthetic

into an acrylic resin provisional prosthesis that is

team should approach this early phase of treatment

used to analyze and verify the proposed parameters

as an opportunity to establish and strengthen a

and determine necessary changes in shape or color

mutually positive relationship with the patient.'

Flu 8-1

FIG 8-2

of

TEC H N I CAL

D IAG NO STIC

A N D

before the ceramic restoration is fabricated. This vey

Complex esthetic restorations require a precise

crucial phase requires cooperation among all mem­

therapeutic approach to ensure that the definitive

bers of the prosthetic team to synthesize what they

restoration harmonizes with the surrounding tissues

know of the patient's character and communicate this .

Fig 8-1 Provisional diagnostic mock-up constructed directly in the patient's mouth. The teeth are isolated by the clinician using liquid glycerin or normal liquid soap to ensure the resin can be more readily detached from the prepared teeth.

Fig 8-2 Silicone matrix filled with acrylic rem in the plastic phase. The clinician uses the silicone index implemented on the diagnostic waxup as a matrix to mold the diagnostic mock-up on the teeth for which the provisional restorations are being prepared. Fig 8-3 Immediate appearance of the resin after direct polymerization and subsequent extraction of the silicone matrix. The acrylic material will be detached later using hand tools. Fig 8-4 Slack demarcations Indicating corrections to improve the anatomy of the mock-up teeth.

1

FIG 8-3

FIG 8-4

ESTH ETI C

APPROACH

CHAPTER 8 Technical Considerations for Provisional Prostheses

.. information to the dental technician to use in defin­ ing the tooth shape of the provisional restoration. In the authors' practice, a distinction is made be­ tween different types of provisional elements: • •

The technique consists of adapting the wax

uncomfortable with the look and feel of the new

which have been isolated using either petroleum jelly

veneers (obtained from the silicone casting molded

tooth dimensions when the diagnostic mock-up is

or liquid soap (Figs 8·1 to 8-4). The contours of the

on the waxup) on a new cast duplicated from the

inserted for the first time. This reaction is both nor­

resin mock-up are trimmed of all excess material, and

master cast. A silicone index, molded on the new wax

mal and understandable since the patient's dental

then it is given to the patient to evaluate at home.

veneers, is filled with resin and pressed onto anoth·

expression and tooth shape developed gradually over

directly over the teeth involved in the restoration,

er cast duplicated from the master cast to obtain the

many years. Therefore, it is better to make small pro­

orthodontic mock-up (Figs 8-10 to 8-16).

gressive corrections to the length and shape of the

laboratory using two study casts, one made of stone

Crown diagnostic mock-up

stress, which can lead to a refusal to continue with

and the other of silicone duplication material (Elite

A crown-lengthening mock-up renects the planned

the treatment.

Double, Zhermack). The diagnostic waxup is applied

dimensions of the restored teeth, which can be espe­

Sometimes the patient's first impression is nega­

to the first (stone) cast, which is then used by the

cially valuable for cases in which a design for reshap­

tive. When this happens, the clinician must try to understand the patient's reaction and then proceed

Mock-up

•

First-generation shell or prosthesis

I n direct or technical mock-up

Second-generation or adapted prosthesis

The indirect mock-up technique is undertaken in the

Mock-up By t h e term mock-up w e refer to a very t h i n clinical

.

teeth in order to minimize the patient's anxiety and

aid that is generally made of acrylic resin and that

dental technician to fabricate a mold using extra­

ing and lengthening the teeth must be completed

incorporates each of the new clinical parameters

hard (85 shores) silicone (Zetalabor). This silicone

before tooth preparation, then the provisional restora­

to make the necessay adjustments without showing

established by the diagnostic waxup. In practice, this

index is later filled with acylic resin and placed

tion is immediately executed (Figs 8-17 to 8-20).

this to the patient. Above all, the patient should not

negative copy of the diagnostic waxup also serves as

directly on the second (silicone) cast, thus producing

The acrylic resin mock-up is inserted in the mouth

be given the mock-up for in-home analysis until the

the mock-up. Inert wax (Schuler Dental) is applied to

over the teeth involved in the prosthetic restoration

appropriate changes have been made. Through each

an accurate reproduction of it, thus offering the great advantage of showing the rehabilitation treatment

the teeth involved in the restoration to facilitate

to allow the clinician to check the occlusion, which

phase of treatment, the patient must be informed

integrated in the overall esthetic and functional con­

removal of the acrylic mock-up. The entire site

would have been modified in the previous phase of

about all changes that are made, and the clinician

text directly on the patient. The mock-up can serve

involved in the provisional restoration with the

treatment (Fig 8-21). When occlusal adjustments are

must be aware that subjective esthetic evaluation

acrylic resin must be further isolated with a plaster­

necessay to optimize the relation between the arch­

requires an extended clinical and in-home trial over a

patients who want veneers or other esthetic restora­

resin material (Unifol, Perident). The isolating mater­

es, they can be made on the mock-up. The clinician

tive treatment, when new shapes and sizes and a

ial must be applied to the sites not involved in the

can also use the mock-up to assess the shapes of the

the patient after 1 week, by which time the patient

new volume of the teeth must be designed and

fabrication of the mock-up as well, to facilitate its

teeth and the patient's expression, as well as the

should have become more accustomed to the new

approved by the patient.>6 The patient's input is

extraction without damaging the plaster cast.

occlusion, before initiating treatment in the oral cav­

smile and dental

ity (Figs 8·22 to 8-25).

should not be initiated until after the patient has

as an important means of analysis and testing in

important to avoid any misunderstandings if small

Finally, the series of casts representing the initial

changes are needed based on the information ob­

case, the waxup, and the mock-up are forwarded to

tained from the diagnostic mock-up. Two implementation techniques to prepare the mock-up are described: a clinical or direct mock-up,

Tooth preparation

given approval.

the clinician (Figs 8-s to 8-7) for use in explaining to the patient the various stages that have been com­

An acrylic resin mock-up that lengthens the crowns

pleted (Figs 8·8 and 8-9).

and modifies the gingival contours can be used for

a tooth (eg, when correcting tooth position without

cases in which treatment requires the alignment and

performing orthodontic treatment). Such preparation

Orthodontic mock-up

optimal positioning of the gingival contours. With the

creates the minimum amount of space needed to intro­ duce the mock-up, which thereafter will also act as the irst provisional restoration once it has been aligned.

An orthodontic mock-up can be placed directly i n the

mock-up inserted in the oral cavity, the clinician can

A silicone index is molded via condensation directly

patient's mouth with the teeth in their original posi­

use an indelible marker to mark the modifications on

on the diagnostic waxup (Zetalabor, Zermack) and

tion, prior to any orthodontic displacement. It allows

the gingival potion of the cast, thus making the mock·

then immediately transferred to the dental office. The

the patient to understand the restorative treatment

up useful for intra-operative surgery (see Fig 8-21).

clinician fills the silicone index with autopolymerizing

that is planned and appreciate the importance of the

resin and then positions it inside the patient's mouth

expression.

Surgical mock-up

and a technical or indirect mock-up. Direct or clinical diagnostic mock-up

number of days. The changes can be discussed with

preprosthetic orthodontic treatment.

In general, the diagnostic mock-up enables the

Preliminay tooth preparation for the mock-up is sometimes necessay to reduce the original volume of

Esthetically, however, the appearance of a diag­ nostic mock-up is inadequate when compared with a stratified

provisional restoration that offers the

patient to evaluate the proposed restorative treat·

patient a clearer idea of the definitive restoration and

ment over a period of time. Patients frequently are

is distinctly more comfortable in terms of both func- .

241

CHAPTER 8 Technical Considerations for Provisional Prostheses

.. information to the dental technician to use in defin­ ing the tooth shape of the provisional restoration. In the authors' practice, a distinction is made be­ tween different types of provisional elements: • •

The technique consists of adapting the wax

uncomfortable with the look and feel of the new

which have been isolated using either petroleum jelly

veneers (obtained from the silicone casting molded

tooth dimensions when the diagnostic mock-up is

or liquid soap (Figs 8·1 to 8-4). The contours of the

on the waxup) on a new cast duplicated from the

inserted for the first time. This reaction is both nor­

resin mock-up are trimmed of all excess material, and

master cast. A silicone index, molded on the new wax

mal and understandable since the patient's dental

then it is given to the patient to evaluate at home.

veneers, is filled with resin and pressed onto anoth·

expression and tooth shape developed gradually over

directly over the teeth involved in the restoration,

er cast duplicated from the master cast to obtain the

many years. Therefore, it is better to make small pro­

orthodontic mock-up (Figs 8-10 to 8-16).

gressive corrections to the length and shape of the

laboratory using two study casts, one made of stone

Crown diagnostic mock-up

stress, which can lead to a refusal to continue with

and the other of silicone duplication material (Elite

A crown-lengthening mock-up renects the planned

the treatment.

Double, Zhermack). The diagnostic waxup is applied

dimensions of the restored teeth, which can be espe­

Sometimes the patient's first impression is nega­

to the first (stone) cast, which is then used by the

cially valuable for cases in which a design for reshap­

tive. When this happens, the clinician must try to understand the patient's reaction and then proceed

Mock-up

•

First-generation shell or prosthesis

I n direct or technical mock-up

Second-generation or adapted prosthesis

The indirect mock-up technique is undertaken in the

Mock-up By t h e term mock-up w e refer to a very t h i n clinical

.

teeth in order to minimize the patient's anxiety and

aid that is generally made of acrylic resin and that

dental technician to fabricate a mold using extra­

ing and lengthening the teeth must be completed

incorporates each of the new clinical parameters

hard (85 shores) silicone (Zetalabor). This silicone

before tooth preparation, then the provisional restora­

to make the necessay adjustments without showing

established by the diagnostic waxup. In practice, this

index is later filled with acylic resin and placed

tion is immediately executed (Figs 8-17 to 8-20).

this to the patient. Above all, the patient should not

negative copy of the diagnostic waxup also serves as

directly on the second (silicone) cast, thus producing

The acrylic resin mock-up is inserted in the mouth

be given the mock-up for in-home analysis until the

the mock-up. Inert wax (Schuler Dental) is applied to

over the teeth involved in the prosthetic restoration

appropriate changes have been made. Through each

an accurate reproduction of it, thus offering the great advantage of showing the rehabilitation treatment

the teeth involved in the restoration to facilitate

to allow the clinician to check the occlusion, which

phase of treatment, the patient must be informed

integrated in the overall esthetic and functional con­

removal of the acrylic mock-up. The entire site

would have been modified in the previous phase of

about all changes that are made, and the clinician

text directly on the patient. The mock-up can serve

involved in the provisional restoration with the

treatment (Fig 8-21). When occlusal adjustments are

must be aware that subjective esthetic evaluation

acrylic resin must be further isolated with a plaster­

necessay to optimize the relation between the arch­

requires an extended clinical and in-home trial over a

patients who want veneers or other esthetic restora­

resin material (Unifol, Perident). The isolating mater­

es, they can be made on the mock-up. The clinician

tive treatment, when new shapes and sizes and a

ial must be applied to the sites not involved in the

can also use the mock-up to assess the shapes of the

the patient after 1 week, by which time the patient

new volume of the teeth must be designed and

fabrication of the mock-up as well, to facilitate its

teeth and the patient's expression, as well as the

should have become more accustomed to the new

approved by the patient.>6 The patient's input is

extraction without damaging the plaster cast.

occlusion, before initiating treatment in the oral cav­

smile and dental

ity (Figs 8·22 to 8-25).

should not be initiated until after the patient has

as an important means of analysis and testing in

important to avoid any misunderstandings if small

Finally, the series of casts representing the initial

changes are needed based on the information ob­

case, the waxup, and the mock-up are forwarded to

tained from the diagnostic mock-up. Two implementation techniques to prepare the mock-up are described: a clinical or direct mock-up,

Tooth preparation

given approval.

the clinician (Figs 8-s to 8-7) for use in explaining to the patient the various stages that have been com­

An acrylic resin mock-up that lengthens the crowns

pleted (Figs 8·8 and 8-9).

and modifies the gingival contours can be used for

a tooth (eg, when correcting tooth position without

cases in which treatment requires the alignment and

performing orthodontic treatment). Such preparation

Orthodontic mock-up

optimal positioning of the gingival contours. With the

creates the minimum amount of space needed to intro­ duce the mock-up, which thereafter will also act as the irst provisional restoration once it has been aligned.

An orthodontic mock-up can be placed directly i n the

mock-up inserted in the oral cavity, the clinician can

A silicone index is molded via condensation directly

patient's mouth with the teeth in their original posi­

use an indelible marker to mark the modifications on

on the diagnostic waxup (Zetalabor, Zermack) and

tion, prior to any orthodontic displacement. It allows

the gingival potion of the cast, thus making the mock·

then immediately transferred to the dental office. The

the patient to understand the restorative treatment

up useful for intra-operative surgery (see Fig 8-21).

clinician fills the silicone index with autopolymerizing

that is planned and appreciate the importance of the

resin and then positions it inside the patient's mouth

expression.

Surgical mock-up

and a technical or indirect mock-up. Direct or clinical diagnostic mock-up

number of days. The changes can be discussed with

preprosthetic orthodontic treatment.

In general, the diagnostic mock-up enables the

Preliminay tooth preparation for the mock-up is sometimes necessay to reduce the original volume of

Esthetically, however, the appearance of a diag­ nostic mock-up is inadequate when compared with a stratified

provisional restoration that offers the

patient to evaluate the proposed restorative treat·

patient a clearer idea of the definitive restoration and

ment over a period of time. Patients frequently are

is distinctly more comfortable in terms of both func- .

241

CHr i :£ Technical Considerations for Provisional Prostheses

Fig 8-5 Study cast of the initial situation created using the technique described in chapter l. This cast provides the technician with a clear and immediate view of the treatment result. Fig 8-6 Diagnostic waxup an the duplicate study cast. It is important to consider bath the preoperative anatomy of the case and various treatment options. Fig 8-7 Technical diagnostic mack-up an the second cast obtained from the study cast dupli­ cate. With the indirect technique. the laboratory has the opportunity to use the duplicates of the master study cast and provide the clinician with the fi01shed mack-up an a new cast. Fig 8-8 Patient's smile before treatment. Fig 8 - 9 The mack-up. implemented in the laboratory on the diag­ nostic waxup. is inserted directly an the natural dentition to evaluate the parameters established in the planning phase before any procedures are begun. The changed dental anatomy and dentagingival relationship that would be achieved by the planned treatment can be easily assessed '" this way. Fig 8-10 Initial clinical case in wh1ch the teeth need to be shifted to the left in order to achieve mare optimal spacing.

2

Fig 8-11 Wax up showing new anatomy and positioning. It is important to plan the correct spacing of teeth to achieve satisfactory integration of the restorative treatment in complex esthetic cases. Fig 8-12 Wax up placed directly an the duplicate cast used to create the acrylic resin mock-up. This phase is crucial far determining the patient's acceptance of the treatment plan and above all the esthetic success of the pro­ visional. Fig 8-13 Orthodontic diagnostic mack-up finished and polished by hand and ready to be inserted in the oral cavity. Fig 8-14 Mack-up inserted in the patient's mouth. This step demonstrates to the patient the need far and benefits of orthodontic treatment. Fig 8-15 Patient's smile before treatment. The significant dental asymmetry in relation to the midline of the face is evident. Fig 8-16 Smile after insertion of the acrylic resin mock-up aver the existing prosthetic restoration.

CHr i :£ Technical Considerations for Provisional Prostheses

Fig 8-5 Study cast of the initial situation created using the technique described in chapter l. This cast provides the technician with a clear and immediate view of the treatment result. Fig 8-6 Diagnostic waxup an the duplicate study cast. It is important to consider bath the preoperative anatomy of the case and various treatment options. Fig 8-7 Technical diagnostic mack-up an the second cast obtained from the study cast dupli­ cate. With the indirect technique. the laboratory has the opportunity to use the duplicates of the master study cast and provide the clinician with the fi01shed mack-up an a new cast. Fig 8-8 Patient's smile before treatment. Fig 8 - 9 The mack-up. implemented in the laboratory on the diag­ nostic waxup. is inserted directly an the natural dentition to evaluate the parameters established in the planning phase before any procedures are begun. The changed dental anatomy and dentagingival relationship that would be achieved by the planned treatment can be easily assessed '" this way. Fig 8-10 Initial clinical case in wh1ch the teeth need to be shifted to the left in order to achieve mare optimal spacing.

2

Fig 8-11 Wax up showing new anatomy and positioning. It is important to plan the correct spacing of teeth to achieve satisfactory integration of the restorative treatment in complex esthetic cases. Fig 8-12 Wax up placed directly an the duplicate cast used to create the acrylic resin mock-up. This phase is crucial far determining the patient's acceptance of the treatment plan and above all the esthetic success of the pro­ visional. Fig 8-13 Orthodontic diagnostic mack-up finished and polished by hand and ready to be inserted in the oral cavity. Fig 8-14 Mack-up inserted in the patient's mouth. This step demonstrates to the patient the need far and benefits of orthodontic treatment. Fig 8-15 Patient's smile before treatment. The significant dental asymmetry in relation to the midline of the face is evident. Fig 8-16 Smile after insertion of the acrylic resin mock-up aver the existing prosthetic restoration.

C1 , · Technical Considerations for Provisional Prostheses

Fig 8-17 Clinical case requiring crown lengthening to treat the worn natural dentition of a bruxing patient Fig 8-18 Casts on an articulator showing the required vertical dimension. based on the occlusal record provided by the clinician. Fig 8-1 g Maxillary and mandibular waxups on an articulator. Treatment is focused on the redefinition of the tooth anatomy and function, especially in terms of occlusal guidance and disclusion in protrusion and right and left lateral movements. Fig 8-20 Maxillary and mandibular mock-ups on the casts. It is sound practice also to work on the master cast duplicates in order to obtain these removable provisional elements again at a later time. Fig 8-21 Mock-up inserted in the oral cavity. At this point it is possible to evaluate the established parameters and the occlusal record by performi n g phonetic and esthetic tests. Fig 8-22 Patient's smile before treatment Note the significant loss of vertical height with the marked wear of the o cclusal surfaces and the resulting shape and composition of the dental anatomy. Fig 8-23 Patient's smile with the mock-up placed in the oral cavity. It is advisable to take photographs to allow re-evaluation of the case in regards to esthetic appearance without the patient being present Fig 8-24 Appearance of perioral structures before treatment Fig 8-25 Change in perioral structures with the mock-up inserted.

25

C1 , · Technical Considerations for Provisional Prostheses

Fig 8-17 Clinical case requiring crown lengthening to treat the worn natural dentition of a bruxing patient Fig 8-18 Casts on an articulator showing the required vertical dimension. based on the occlusal record provided by the clinician. Fig 8-1 g Maxillary and mandibular waxups on an articulator. Treatment is focused on the redefinition of the tooth anatomy and function, especially in terms of occlusal guidance and disclusion in protrusion and right and left lateral movements. Fig 8-20 Maxillary and mandibular mock-ups on the casts. It is sound practice also to work on the master cast duplicates in order to obtain these removable provisional elements again at a later time. Fig 8-21 Mock-up inserted in the oral cavity. At this point it is possible to evaluate the established parameters and the occlusal record by performi n g phonetic and esthetic tests. Fig 8-22 Patient's smile before treatment Note the significant loss of vertical height with the marked wear of the o cclusal surfaces and the resulting shape and composition of the dental anatomy. Fig 8-23 Patient's smile with the mock-up placed in the oral cavity. It is advisable to take photographs to allow re-evaluation of the case in regards to esthetic appearance without the patient being present Fig 8-24 Appearance of perioral structures before treatment Fig 8-25 Change in perioral structures with the mock-up inserted.

25

CHAPTER 8 Technical Considerations for Provisional Prostheses

. tion and esthetics. Conversely, the mock-up repre·

preparation, and the third will be used as a matrix for

.

The dental technician pours the acrylic resin

The indirect technique can strengthen cooperation between the clinician and the technician. Indeed, with

sents the most conservative solution with regard to

molding the acrylic resin over the tooth preparations.

inside the silicone matrix and applies it directly to

the patient's health and the most efective means of

The provisional restoration is monochromatic if

the duplicate cast. After it is removed, the dentin

this technique the technician provides the diagnostic

communicating the new parameters of the restora·

dentin materials alone are used (Fig 8·26). and strat·

material is applied at a pressure of 4 bars and poly­

support of a positional silicone index (Fig 8-40),

tion, since it is positioned directly over the existing

ified if the dentin-enamel technique is adopted. In

dental situation.

the latter case, the clinician fabricates a shell using

3 to s min utes'-9 while the silicone index is held in

The diagnostic commitment of making a stratified

dentin-type acrylic resin on teeth isolated with petro·

position using elastic bands.

provisional prosthesis as well may initially appear

leum jelly or liquid soap. After allowing adequate

merized at a temperature between so0( and 6o0( for

A new silicone index is now made with the dentin

which is useful to avoid damaging work executed in the laboratory and as a clinical reference point for positioning the provisional prosthesis. This technique also prevents shape-related distortions of the provi­

excessive, but it offers numerous advantages: It pro·

time for complete

the clinician

layer in place and sectioned horizontally to monitor

sional prosthesis or incorrect positioning during the

vides the best guarantee for the outcome of the

removes the prosthesis from the mouth and roughs

the reduction of the dentin material so as to ensure

alignment process (Figs 8-41 to 8·46).

polymerization,

treatment, reconfirms the patient's trust, avoids mis­

out the incisal, buccal, and palatal surfaces so as to

adequate space for molding the enamel-type resin. A

understandings, and prevents the unpleasant conse·

allow room for a second application, this time using

photopolymerizing adhesive (Connector) is applied to

Indirect technique on the s i licone index

quences of inadequate treatment.

enamel-type resin (Figs 8-27 and 8-28).

the reduced dentin layer, and setting material can be

As with the other procedures for creating provisional

The prepared dentin provisional restoration is

introduced at the incisal edge and then polymerized

restorations, the starting point is the diagnostic

First-generation provisional restoration

then repositioned in the oral cavity, and a silicone

with a special halogen lamp or light-curing unit for 2

waxup, which ensures that the treatment plan meets the patient's requests.

matrix, this time with an enamel-type resin mixture

minutes, to imitate the incisal efects (Fig 8·38).

The shell-fabricated prosthesis is a first-generation

consisting of So% enamel and 20% transparent

Surface characterizations are not necessary on the

The silicone index made from the waxup acts as a

provisional restoration that is adapted and intro­

material, is molded to the dentin layer (Figs 8·29 to

middle and cervical third, since this provisional pros·

matrix for the dentin-type acrylic resin. It is filled with

duced into the oral cavity immediately after the old

8·31). Ater the dentin-enamel provisional restoration

thesis will be handled by the clinician and is subject

resin and polymerized to create a small resin cast

restoration is removed and preliminary tooth prepa­

has hardened, it is removed from the oral cavity and

to alignment adjustment and other modifications.

(Fig 8-47). This resin cast is then used to make a new

ration has been completed. The first-generation pro­

trimmed using suitable disks and burs (Figs 8·32 to

Finally, the enamel mixture is molded directly on the

silicone index, which is sectioned for monitoring the

hardened dentin at a pressure of 4 bars and poly·

reduction of the incisal edges and buccal surfaces of

visional enhances the patient's oral esthetics, pro­

8-34). To improve precision, the clinician must some·

vides the clinician with diagnostic information, and

times roughen the inside surface around the cevical

merized at a temperature between so°C and 6o°C for

the dentin-type material (Fig 8·48). Intermediate pho­

conditions the soft tissues. It can be developed

margin, moisten this surface with a photopolymeriz­

s minutes, using the same silicone matrix that was

topolymerizing shade modifiers (Artglass (reactive,

using a direct technique in the oral cavity, an indirect

ing adhesive (Connector, Heraeus Kulzer), and realign

used for the dentin layer.

Heraeus Kulzer) can be added once the surface has

technique on the plaster cast, or an indirect tech·

the provisional restoration using auto- and pho·

nique on the silicone index.

The provisional prosthesis is removed from the

been covered with a specific adhesive. The enamel­

topolymerizing resins (Unifast, GC).

plaster cast and fitted on the master cast, which has

type layer is molded onto the dentin-type layer, again

Direct technique in the oral cavtty

Indirect technique on the stone cast

(Fig 8-39). A new silicone index is made with the

The laboratoy prepares a master cast, which is later

The indirect technique is performed in the laboratory,

occlusal stops on the adjacent teeth to verify that

The cast is roughed out using laboratory burs

duplicated for the diagnostic waxup (see chapter 1).

and all of the procedures are executed using a sili·

the alignment in the oral cavity corresponds to the

after polymerization has been completed, removing

been previously prepared by the dental technician

using the same silicone matrix used previously (Figs

8·49 and B· so).

After the waxup has been completed, a number of

cone matrix. After completing the diagnostic waxup,

same position on the plaster cast. If the alignment is

the adjacent teeth and leaving intact only the teeth

silicone indices are prepared at a pressure of 4 bars

the dental technician undertakes the preliminary

not identical, the clinician needs to adjust the pre­

involved in the restoration. The provisional restora­

to ensure the highest possible accuracy in reproduc­

tooth preparation on the plaster cast. The preparation

pared tooth inside the mouth or reduce the provi­

ing the details of the waxup.

is monitored using a horizontally sectioned silicone

sional prosthesis at points of friction or in areas of

The clinician eventually receives the study cast. a

index. This cast with prepared teeth is then duplicat-

tissue compression in edentulous sites. The provi­

duplicate cast on which the diagnostic waxup has

ed to create a new plaster cast on which the provi­

sional shell must maintain the same position and

been made, and at least three silicone indices. Two of

sional prosthesis can be created (Figs 8·3s to 8-37). .

the indices will be sectioned for use during tooth

parameters when it is transferred from the plaster cast to the intraoral site.

tion is then trimmed and polished (Fig B· s 1). Because

it is repositioned inside the mold, the small resin

cast can be hollowed out without damaging the cer­

vical limits (Figs B-s2 and B· s3).

The silicone matrix originally used to cast the resin is sectioned horizontally, and the provisional .

247

CHAPTER 8 Technical Considerations for Provisional Prostheses

. tion and esthetics. Conversely, the mock-up repre·

preparation, and the third will be used as a matrix for

.

The dental technician pours the acrylic resin

The indirect technique can strengthen cooperation between the clinician and the technician. Indeed, with

sents the most conservative solution with regard to

molding the acrylic resin over the tooth preparations.

inside the silicone matrix and applies it directly to

the patient's health and the most efective means of

The provisional restoration is monochromatic if

the duplicate cast. After it is removed, the dentin

this technique the technician provides the diagnostic

communicating the new parameters of the restora·

dentin materials alone are used (Fig 8·26). and strat·

material is applied at a pressure of 4 bars and poly­

support of a positional silicone index (Fig 8-40),

tion, since it is positioned directly over the existing

ified if the dentin-enamel technique is adopted. In

dental situation.

the latter case, the clinician fabricates a shell using

3 to s min utes'-9 while the silicone index is held in

The diagnostic commitment of making a stratified

dentin-type acrylic resin on teeth isolated with petro·

position using elastic bands.

provisional prosthesis as well may initially appear

leum jelly or liquid soap. After allowing adequate

merized at a temperature between so0( and 6o0( for

A new silicone index is now made with the dentin

which is useful to avoid damaging work executed in the laboratory and as a clinical reference point for positioning the provisional prosthesis. This technique also prevents shape-related distortions of the provi­

excessive, but it offers numerous advantages: It pro·

time for complete

the clinician

layer in place and sectioned horizontally to monitor

sional prosthesis or incorrect positioning during the

vides the best guarantee for the outcome of the

removes the prosthesis from the mouth and roughs

the reduction of the dentin material so as to ensure

alignment process (Figs 8-41 to 8·46).

polymerization,

treatment, reconfirms the patient's trust, avoids mis­

out the incisal, buccal, and palatal surfaces so as to

adequate space for molding the enamel-type resin. A

understandings, and prevents the unpleasant conse·

allow room for a second application, this time using

photopolymerizing adhesive (Connector) is applied to

Indirect technique on the s i licone index

quences of inadequate treatment.

enamel-type resin (Figs 8-27 and 8-28).

the reduced dentin layer, and setting material can be

As with the other procedures for creating provisional

The prepared dentin provisional restoration is

introduced at the incisal edge and then polymerized

restorations, the starting point is the diagnostic

First-generation provisional restoration

then repositioned in the oral cavity, and a silicone

with a special halogen lamp or light-curing unit for 2

waxup, which ensures that the treatment plan meets the patient's requests.

matrix, this time with an enamel-type resin mixture

minutes, to imitate the incisal efects (Fig 8·38).

The shell-fabricated prosthesis is a first-generation

consisting of So% enamel and 20% transparent

Surface characterizations are not necessary on the

The silicone index made from the waxup acts as a

provisional restoration that is adapted and intro­

material, is molded to the dentin layer (Figs 8·29 to

middle and cervical third, since this provisional pros·

matrix for the dentin-type acrylic resin. It is filled with

duced into the oral cavity immediately after the old

8·31). Ater the dentin-enamel provisional restoration

thesis will be handled by the clinician and is subject

resin and polymerized to create a small resin cast

restoration is removed and preliminary tooth prepa­

has hardened, it is removed from the oral cavity and

to alignment adjustment and other modifications.

(Fig 8-47). This resin cast is then used to make a new

ration has been completed. The first-generation pro­

trimmed using suitable disks and burs (Figs 8·32 to

Finally, the enamel mixture is molded directly on the

silicone index, which is sectioned for monitoring the

hardened dentin at a pressure of 4 bars and poly·

reduction of the incisal edges and buccal surfaces of

visional enhances the patient's oral esthetics, pro­

8-34). To improve precision, the clinician must some·

vides the clinician with diagnostic information, and

times roughen the inside surface around the cevical

merized at a temperature between so°C and 6o°C for

the dentin-type material (Fig 8·48). Intermediate pho­

conditions the soft tissues. It can be developed

margin, moisten this surface with a photopolymeriz­

s minutes, using the same silicone matrix that was

topolymerizing shade modifiers (Artglass (reactive,

using a direct technique in the oral cavity, an indirect

ing adhesive (Connector, Heraeus Kulzer), and realign

used for the dentin layer.

Heraeus Kulzer) can be added once the surface has

technique on the plaster cast, or an indirect tech·

the provisional restoration using auto- and pho·

nique on the silicone index.

The provisional prosthesis is removed from the

been covered with a specific adhesive. The enamel­

topolymerizing resins (Unifast, GC).

plaster cast and fitted on the master cast, which has

type layer is molded onto the dentin-type layer, again

Direct technique in the oral cavtty

Indirect technique on the stone cast

(Fig 8-39). A new silicone index is made with the

The laboratoy prepares a master cast, which is later

The indirect technique is performed in the laboratory,

occlusal stops on the adjacent teeth to verify that

The cast is roughed out using laboratory burs

duplicated for the diagnostic waxup (see chapter 1).

and all of the procedures are executed using a sili·

the alignment in the oral cavity corresponds to the

after polymerization has been completed, removing

been previously prepared by the dental technician

using the same silicone matrix used previously (Figs

8·49 and B· so).

After the waxup has been completed, a number of

cone matrix. After completing the diagnostic waxup,

same position on the plaster cast. If the alignment is

the adjacent teeth and leaving intact only the teeth

silicone indices are prepared at a pressure of 4 bars

the dental technician undertakes the preliminary

not identical, the clinician needs to adjust the pre­

involved in the restoration. The provisional restora­

to ensure the highest possible accuracy in reproduc­

tooth preparation on the plaster cast. The preparation

pared tooth inside the mouth or reduce the provi­

ing the details of the waxup.

is monitored using a horizontally sectioned silicone

sional prosthesis at points of friction or in areas of

The clinician eventually receives the study cast. a

index. This cast with prepared teeth is then duplicat-

tissue compression in edentulous sites. The provi­

duplicate cast on which the diagnostic waxup has

ed to create a new plaster cast on which the provi­

sional shell must maintain the same position and

been made, and at least three silicone indices. Two of

sional prosthesis can be created (Figs 8·3s to 8-37). .

the indices will be sectioned for use during tooth

parameters when it is transferred from the plaster cast to the intraoral site.

tion is then trimmed and polished (Fig B· s 1). Because

it is repositioned inside the mold, the small resin

cast can be hollowed out without damaging the cer­

vical limits (Figs B-s2 and B· s3).

The silicone matrix originally used to cast the resin is sectioned horizontally, and the provisional .

247

CH Pll R S Technical Considerations for Provisional Prostheses

Fig 8-26 Prepared dentin provisional reslorat1on placed in the oral cavity. At this point the provisional can be trimmed and polished imme­ diately for a monochromatic result if the esthetic needs and expectations of the case are not high. Fig 8-27 For cases in which esthetics are important. it is necessary to continue the treatment by reducing the dentin layer to create spate for the enamel resin and photo­ polymeriZing colors. when applicable. Here. the dentin has been prepared to recreate the mamelons and other dentinal structures and reduced to a thin layer in the incisal third to a thieve the optimal value. Fig 8-28 The spate available for the enamel resin and photopoly­ meming colors is checked. Fig 8-2g The incisal gel is plated 1n preparation for the introduction of chromatic characterizations.

Fig 8-30 The clinician has plated the chromatic characterizations on the dentin surface. The colors are polymerized with a special halogen light-emitting lamp. Fig 8-31 Molding phase of enamel-type acrylic resin. Fig 8-32 The provisional has been finished. This phase is always completed using diamond or tungsten carbide burs. Fig 8-33 Polishing has been completed and lhe acrylic resin provisional cemented in the mouth. Fig 8-34 Profile view of the provisional at high magnification under the stereomicroscope.

249

CH Pll R S Technical Considerations for Provisional Prostheses

Fig 8-26 Prepared dentin provisional reslorat1on placed in the oral cavity. At this point the provisional can be trimmed and polished imme­ diately for a monochromatic result if the esthetic needs and expectations of the case are not high. Fig 8-27 For cases in which esthetics are important. it is necessary to continue the treatment by reducing the dentin layer to create spate for the enamel resin and photo­ polymeriZing colors. when applicable. Here. the dentin has been prepared to recreate the mamelons and other dentinal structures and reduced to a thin layer in the incisal third to a thieve the optimal value. Fig 8-28 The spate available for the enamel resin and photopoly­ meming colors is checked. Fig 8-2g The incisal gel is plated 1n preparation for the introduction of chromatic characterizations.

Fig 8-30 The clinician has plated the chromatic characterizations on the dentin surface. The colors are polymerized with a special halogen light-emitting lamp. Fig 8-31 Molding phase of enamel-type acrylic resin. Fig 8-32 The provisional has been finished. This phase is always completed using diamond or tungsten carbide burs. Fig 8-33 Polishing has been completed and lhe acrylic resin provisional cemented in the mouth. Fig 8-34 Profile view of the provisional at high magnification under the stereomicroscope.

249

Technical Considerations for Provisional Prostheses

Fig 8-35 Formalton of several l -mm-deep grooves on the plasler cast Ftg 8-36 The available space for acrylic resin is checked using a sec­ tioned siltcone index obtained from the dtagnostic waxup Fig 8-37 Preliminary tooth preparation is completed on the study cast duplicate. whtch IS ready to be reduplicated The proviSional prosthesis will then be created on this new plaster cast. Fig 8-38 The incisal photopolymer­ iztng colors have been added over the dentin material. Fig 8-3g Promional finished and positioned on the cast. An extra-hard silicone index will be implemented on the provisional while posittoned on the plaster cast. providing occlusal stops on the posterior sector. This will enable the cltntctan to transfer the provistonal to the patient's mouth white maintaining the same positiOn as on the plaster cast. Fig 8-40 Provisional tnserted tn the mouth ustng the siltcone index

Fig 8-41 Preoperattve view of a clintcal case tn which the existtng metal-ceramtc crowns on the central tncisors are dtSproporttonate to the adjacent teeth. Fig 8-42 The provisional prosthesis was implemented ustng the indirect techntque and then aligned in the oral cavity using the silicone index. Fig 8-43 Smtle before treatment. Fig 8-44 Smtle with provisional tn place The central incisors are now in harmony with the adjacent teeth. Fig 8-45 Full-face pretreatment view of pattent. Fig 8-46 Patient's appearance following cementation of the provisional.

251

Technical Considerations for Provisional Prostheses

Fig 8-35 Formalton of several l -mm-deep grooves on the plasler cast Ftg 8-36 The available space for acrylic resin is checked using a sec­ tioned siltcone index obtained from the dtagnostic waxup Fig 8-37 Preliminary tooth preparation is completed on the study cast duplicate. whtch IS ready to be reduplicated The proviSional prosthesis will then be created on this new plaster cast. Fig 8-38 The incisal photopolymer­ iztng colors have been added over the dentin material. Fig 8-3g Promional finished and positioned on the cast. An extra-hard silicone index will be implemented on the provisional while posittoned on the plaster cast. providing occlusal stops on the posterior sector. This will enable the cltntctan to transfer the provistonal to the patient's mouth white maintaining the same positiOn as on the plaster cast. Fig 8-40 Provisional tnserted tn the mouth ustng the siltcone index

Fig 8-41 Preoperattve view of a clintcal case tn which the existtng metal-ceramtc crowns on the central tncisors are dtSproporttonate to the adjacent teeth. Fig 8-42 The provisional prosthesis was implemented ustng the indirect techntque and then aligned in the oral cavity using the silicone index. Fig 8-43 Smtle before treatment. Fig 8-44 Smtle with provisional tn place The central incisors are now in harmony with the adjacent teeth. Fig 8-45 Full-face pretreatment view of pattent. Fig 8-46 Patient's appearance following cementation of the provisional.

251

CHAPTER 8 Technical Considerations for Provisional Prostheses

. prosthesis is introduced into the mouth. By using the actual matrix, the clinician can more easily determine

removable dies and the gingiva.

. then evaluated using the silicone index on the sec­

Another silicone index is created so that the

ond stone cast that was fabricated especially for this

reduction of the dentin layer can be carefully moni­ tored (Figs 8-70 to 8-72). The buccolingual thickness

the exact position of the provisional prosthesis

The duplicate dies are treated with a setting solu­

purpose (Figs 8-6o and 8-61). The dies are bonded

when it is positioned in the oral cavity (Figs 8·54

tion (Margidur, Benzer Dental) that penetrates the

at the cervical margin of the cast using adhesive

of the dentin layer must have an incisal edge that is

and 8-55).

porous plaster without increasing in thickness. After

wax, which is also used to bond the silicone index

significantly though not completely reduced, as this

their exterior surfaces are treated with soft wax. the

to the dies. The surfaces of the dies protruding from

would greatly compromise the value of the final

dies are reintroduced into the impression with a lit­

the upper part of the cast are isolated with a very

result (Fig 8-73). A bonding adhesive (Connector) is

Second-generation provisional prosthesis

tle pressure. Cyanoacrylate is added to the head of

thin layer of inert wax, and then a larger quantity of

applied to ensure an enhanced bond with the pho­

each die, and the dies are then bonded.

inert wax is applied to the base of the dies to iden­

topolymerizing colors (Artglass (reactive) added to the surface (Fig 8·74). The second silicone index is

Modern practitioners have long abandoned the tra·

The dies are bonded at the cervical margin with

tify where they are located during the squaring oper­

ditional practice of using a mediocre provisional

adhesive wax (Kiebewachs, Gebdi), which cements

ation. The two parts previously moistened are then

used to ensure that suficient space is left for the

prosthesis to be replaced with an improved perma·

them during casting (Fig 8-58) and enables them to

fixated with plaster and, once set, excess portions

enamel-type material to be added and polymerized.

nent ceramic prosthesis. '0

be removed once the plaster has set and the bond­

are trimmed to square the entire cast. The sealant

Once the enamel-type material is molded using

The stratified provisional prosthesis involves the

ed dies have been reintroduced inside the impres­

wax is removed from the base using a heat-generat­

the same matrix, the restoration is detached from

application of a technique similar to that used to

sion. For optimal results, this plaster should be in a

ing machine so that the dies can be removed (Figs

the plaster cast, which can be discarded, and adapt·

8-62 to 8-66).

ed to the working cast with the aid of contact·

create

indirect first-generation provisional

slightly more liquified form than usual to allow

restoration, requiring either a stone or resin cast,

the

slight vibrations to be applied during the casting

except that the pigmentation also is applied to the

process.

With its removable dies, this cast provides the

detecting powder (Figs 8-75 to 8-78). The result is

means to condition the soft tissues and assess the

a stratified provisional restoration that can be

For this phase, the technician has two options for

tooth morphology, since the gingival information is

mechanically trimmed and polished without loss of

producing the master cast: The cast can be poured

included. A duplicate of this cast will be needed for

its color characteristics. It can be used to evaluate

Stone casts

as a single process, thus instantly creating the base,

molding the resin.

the shape, length, position, and characterizations

The essential diferences in this procedure compared

or a double-pouring process can be used, requiring

middle and cervical third of the restorations.

with the techniques described earlier are ) the

In summary, the sequence is as follows:

(chroma, value, and color) of the restoration, as well as for gingival conditioning (Figs 8-79 to 8-82).

two separate pours. The latter technique involves a

teeth have already been prepared, and (2) the soft

first pour to cover the dies and a second pour to

•

Master dies

tissues, which for several weeks supported the first­

create a cast in a rubber base. Both casts are

•

Master dies duplicated using silicone

is reconfirmed in vivo with the provisional prosthesis

generation provisional prosthesis, have adapted to

removed from the im pression after the plaster has

•

Duplicated dies

that reproduces the shape of the waxup, or some

the new situation.

set (about 45 minutes) and squared separately

•

Fixed dies used to prepare a control silicone key

detail of the dental anatomy is changed by examin­

Dies originating from the duplication inserted in

ing the slides and a plaster model originating from

the impression for the Geller model

the first provisional prosthesis (Figs 8-83 to 8·86).

For complex cases and others that the clinician

252

rations during the cast construction phase with the

using the cast-squaring tool.

deems appropriate, a second-generation provisional

The dies are removed individually with the use of

restoration should be prepared in the laboratoy on

hot steam produced by a steam generator to melt

a precise elastomeric impression obtained ater gin­

the adhesive wax sealant. The technician must take

gival retraction. The impression should have perfect­

•

•

Geller cast

The diagnostic commitment of the prosthetic team

The second-generation provisional prosthesis is a conversion of the monochromatic waxup in poly­

care to clean the die channels before any subse­

A new waxup is prepared on the duplicate work­

ly discernible cervical margins and be cast using

quent use to optimize the positioning of the remov­

ing cast using the silicone index of the study cast

this represents the most important diagnostic stage,

class IV plaster to obtain the master tooth prepara­

able dies. Care should also be taken to highlight the

waxup as a guide (Figs 8-67 and 8-68). A silicone

and, though it is provisional, it conditions the soft

tions. These are trimmed to give them a carrot-like

perimeter of the arch and the channel position when

matrix is molded on the new waxup, set under a

tissues and demonstrates esthetic quality similar

shape and subsequently duplicated (Figs 8·56 and

the casts are matched, so that holes can later be

pressure of 3 to 4 bars (Zeta labor), and used to adapt

to that of the definitive restorative treatment"-'5

8-57). The same elastomeric impression is used to

prepared to accommodate the protruding parts of

the dentin-type material (New Outline, Anaxdent) on

(Figs 8-87 to 8-92). Additionally, this prosthesis gives

prepare another cast; the silicone index made on this

the dies (Fig 8-59). The dies will be reinserted into

the duplicate stone cast. The dentin layer is then

the patient tangible evidence of the prosthetic team's

cast is used to check the position of the tooth prepa-

the cast and then positioned; their exact position is .

fired on the stone cast at 6o0U-9 (Fig 8-69).

commitment to the work involved in the restorative .

chromatic resin. For major restorative treatments,

CHAPTER 8 Technical Considerations for Provisional Prostheses

. prosthesis is introduced into the mouth. By using the actual matrix, the clinician can more easily determine

removable dies and the gingiva.

. then evaluated using the silicone index on the sec­

Another silicone index is created so that the

ond stone cast that was fabricated especially for this

reduction of the dentin layer can be carefully moni­ tored (Figs 8-70 to 8-72). The buccolingual thickness

the exact position of the provisional prosthesis

The duplicate dies are treated with a setting solu­

purpose (Figs 8-6o and 8-61). The dies are bonded

when it is positioned in the oral cavity (Figs 8·54

tion (Margidur, Benzer Dental) that penetrates the

at the cervical margin of the cast using adhesive

of the dentin layer must have an incisal edge that is

and 8-55).

porous plaster without increasing in thickness. After

wax, which is also used to bond the silicone index

significantly though not completely reduced, as this

their exterior surfaces are treated with soft wax. the

to the dies. The surfaces of the dies protruding from

would greatly compromise the value of the final

dies are reintroduced into the impression with a lit­

the upper part of the cast are isolated with a very

result (Fig 8-73). A bonding adhesive (Connector) is

Second-generation provisional prosthesis

tle pressure. Cyanoacrylate is added to the head of

thin layer of inert wax, and then a larger quantity of

applied to ensure an enhanced bond with the pho­

each die, and the dies are then bonded.

inert wax is applied to the base of the dies to iden­

topolymerizing colors (Artglass (reactive) added to the surface (Fig 8·74). The second silicone index is

Modern practitioners have long abandoned the tra·

The dies are bonded at the cervical margin with

tify where they are located during the squaring oper­

ditional practice of using a mediocre provisional

adhesive wax (Kiebewachs, Gebdi), which cements

ation. The two parts previously moistened are then

used to ensure that suficient space is left for the

prosthesis to be replaced with an improved perma·

them during casting (Fig 8-58) and enables them to

fixated with plaster and, once set, excess portions

enamel-type material to be added and polymerized.

nent ceramic prosthesis. '0

be removed once the plaster has set and the bond­

are trimmed to square the entire cast. The sealant

Once the enamel-type material is molded using

The stratified provisional prosthesis involves the

ed dies have been reintroduced inside the impres­

wax is removed from the base using a heat-generat­

the same matrix, the restoration is detached from

application of a technique similar to that used to

sion. For optimal results, this plaster should be in a

ing machine so that the dies can be removed (Figs

the plaster cast, which can be discarded, and adapt·

8-62 to 8-66).

ed to the working cast with the aid of contact·

create

indirect first-generation provisional

slightly more liquified form than usual to allow

restoration, requiring either a stone or resin cast,

the

slight vibrations to be applied during the casting

except that the pigmentation also is applied to the

process.

With its removable dies, this cast provides the

detecting powder (Figs 8-75 to 8-78). The result is

means to condition the soft tissues and assess the

a stratified provisional restoration that can be

For this phase, the technician has two options for

tooth morphology, since the gingival information is

mechanically trimmed and polished without loss of

producing the master cast: The cast can be poured

included. A duplicate of this cast will be needed for

its color characteristics. It can be used to evaluate

Stone casts

as a single process, thus instantly creating the base,

molding the resin.

the shape, length, position, and characterizations

The essential diferences in this procedure compared

or a double-pouring process can be used, requiring

middle and cervical third of the restorations.

with the techniques described earlier are ) the

In summary, the sequence is as follows:

(chroma, value, and color) of the restoration, as well as for gingival conditioning (Figs 8-79 to 8-82).

two separate pours. The latter technique involves a

teeth have already been prepared, and (2) the soft

first pour to cover the dies and a second pour to

•

Master dies

tissues, which for several weeks supported the first­

create a cast in a rubber base. Both casts are

•

Master dies duplicated using silicone

is reconfirmed in vivo with the provisional prosthesis

generation provisional prosthesis, have adapted to

removed from the im pression after the plaster has

•

Duplicated dies

that reproduces the shape of the waxup, or some

the new situation.

set (about 45 minutes) and squared separately

•

Fixed dies used to prepare a control silicone key

detail of the dental anatomy is changed by examin­

Dies originating from the duplication inserted in

ing the slides and a plaster model originating from

the impression for the Geller model

the first provisional prosthesis (Figs 8-83 to 8·86).

For complex cases and others that the clinician

252

rations during the cast construction phase with the

using the cast-squaring tool.

deems appropriate, a second-generation provisional

The dies are removed individually with the use of

restoration should be prepared in the laboratoy on

hot steam produced by a steam generator to melt

a precise elastomeric impression obtained ater gin­

the adhesive wax sealant. The technician must take

gival retraction. The impression should have perfect­

•

•

Geller cast

The diagnostic commitment of the prosthetic team

The second-generation provisional prosthesis is a conversion of the monochromatic waxup in poly­

care to clean the die channels before any subse­

A new waxup is prepared on the duplicate work­

ly discernible cervical margins and be cast using

quent use to optimize the positioning of the remov­

ing cast using the silicone index of the study cast

this represents the most important diagnostic stage,

class IV plaster to obtain the master tooth prepara­

able dies. Care should also be taken to highlight the

waxup as a guide (Figs 8-67 and 8-68). A silicone

and, though it is provisional, it conditions the soft

tions. These are trimmed to give them a carrot-like

perimeter of the arch and the channel position when

matrix is molded on the new waxup, set under a

tissues and demonstrates esthetic quality similar

shape and subsequently duplicated (Figs 8·56 and

the casts are matched, so that holes can later be

pressure of 3 to 4 bars (Zeta labor), and used to adapt

to that of the definitive restorative treatment"-'5

8-57). The same elastomeric impression is used to

prepared to accommodate the protruding parts of

the dentin-type material (New Outline, Anaxdent) on

(Figs 8-87 to 8-92). Additionally, this prosthesis gives

prepare another cast; the silicone index made on this

the dies (Fig 8-59). The dies will be reinserted into

the duplicate stone cast. The dentin layer is then

the patient tangible evidence of the prosthetic team's

cast is used to check the position of the tooth prepa-

the cast and then positioned; their exact position is .

fired on the stone cast at 6o0U-9 (Fig 8-69).

commitment to the work involved in the restorative .

chromatic resin. For major restorative treatments,

Fig 8-47 Acrylic resin polymerized inside the silicone matrix and implemented on the diagnostic waxup. The acrylic material is baked at a tem­ perature of 6o·c and at a pressure of 4 bars. Fig 8-48 Sectioned silicone index used to evaluate the space available for the enamel-type resin as the surface of the dentin-type resin is reduced. Fig 8-49 Dentin characterizations implemented using photopolymerizing colors. Fig 8-50 Enamel-type acrylic resin molded on the dentin base and subsequently polymerized at a pressure of 4 bars. Fig 8-51 Provisional after polish­ ing on the buccal surfaces. Polishing is achieved using a number of micromotor-operated brushes or a laboratory cleaning machine. Fig 8-52 Provisional following rough1ng out of the internal portion using tungsten carbide burs of different diameters and shapes.

Fig 8-53 Provisional inserted in the silicone index. It is advisable to section the silicone index horizontally to enable easy transfer of the pro­ visional to the mouth for the alignment phase. Fig 8-54 Clinical try-in of the provisional with the help of the silicone index. Fig 8-55 Provisional aligned and cemented in the oral cavity.

255

Fig 8-47 Acrylic resin polymerized inside the silicone matrix and implemented on the diagnostic waxup. The acrylic material is baked at a tem­ perature of 6o·c and at a pressure of 4 bars. Fig 8-48 Sectioned silicone index used to evaluate the space available for the enamel-type resin as the surface of the dentin-type resin is reduced. Fig 8-49 Dentin characterizations implemented using photopolymerizing colors. Fig 8-50 Enamel-type acrylic resin molded on the dentin base and subsequently polymerized at a pressure of 4 bars. Fig 8-51 Provisional after polish­ ing on the buccal surfaces. Polishing is achieved using a number of micromotor-operated brushes or a laboratory cleaning machine. Fig 8-52 Provisional following rough1ng out of the internal portion using tungsten carbide burs of different diameters and shapes.

Fig 8-53 Provisional inserted in the silicone index. It is advisable to section the silicone index horizontally to enable easy transfer of the pro­ visional to the mouth for the alignment phase. Fig 8-54 Clinical try-in of the provisional with the help of the silicone index. Fig 8-55 Provisional aligned and cemented in the oral cavity.

255

Technical Considerations for Provisional Prostheses

Fig 8-56 Master tooth preparations created using a precise elastomeric impression and white class IV plaster. Fig 8-57 The master tooth preparations are duplicated using 1,1 ratio dupliCation silicone. Both the silicone and plaster are treated using a vacuum at a pressure of 4 bars. Fig 8-58 Removable dies with special notches and grooves to guide reinsertion. These dies. which require a slightly tapered shape. are inserted inside the impression to be again subjected to casting. Fig 8-59 Dies reinserted in the cast. The base of the cast has a large trough to house the terminal projections of the removable dies. Retention grooves have been prepared on the adjoining parts. Fig 8-60 Silicone index positioned on the second stone cast. Fig 8-61 Silicone index transferred to the removable-die cast to check positioning.

Fig 8-62 The final section of dies is suitably waxed. and plaster is added over the entire surface. Fig 8-63 Plaster is then poured inside the base trough and on all the retention grooves implemented on the surface. Fig 8-64 Contact positioning of the two parts using the same class IV plaster but with a more liquid consistency. Fig 8-65 Frontal view of the finished and squared cast. Fig 8-66 O cclusal view of a sectioned cast detailing re. -insertion channels of the removable dies. Fig 8-6.7 Frontal view .of a Geller cast of the case. This type of sectioned cast highlights the anatomiC charactenst1cs of the g1ng1val margm and prov1des a better VIeW of the dental anatomy and the dentogingival relationship. It is very difficult to create ceramic restorations without having the gingival tissues for reference.

27

Technical Considerations for Provisional Prostheses

Fig 8-56 Master tooth preparations created using a precise elastomeric impression and white class IV plaster. Fig 8-57 The master tooth preparations are duplicated using 1,1 ratio dupliCation silicone. Both the silicone and plaster are treated using a vacuum at a pressure of 4 bars. Fig 8-58 Removable dies with special notches and grooves to guide reinsertion. These dies. which require a slightly tapered shape. are inserted inside the impression to be again subjected to casting. Fig 8-59 Dies reinserted in the cast. The base of the cast has a large trough to house the terminal projections of the removable dies. Retention grooves have been prepared on the adjoining parts. Fig 8-60 Silicone index positioned on the second stone cast. Fig 8-61 Silicone index transferred to the removable-die cast to check positioning.

Fig 8-62 The final section of dies is suitably waxed. and plaster is added over the entire surface. Fig 8-63 Plaster is then poured inside the base trough and on all the retention grooves implemented on the surface. Fig 8-64 Contact positioning of the two parts using the same class IV plaster but with a more liquid consistency. Fig 8-65 Frontal view of the finished and squared cast. Fig 8-66 O cclusal view of a sectioned cast detailing re. -insertion channels of the removable dies. Fig 8-6.7 Frontal view .of a Geller cast of the case. This type of sectioned cast highlights the anatomiC charactenst1cs of the g1ng1val margm and prov1des a better VIeW of the dental anatomy and the dentogingival relationship. It is very difficult to create ceramic restorations without having the gingival tissues for reference.

27

CHAPTER 8 Technical Considerations for Provisional Prostheses

.. treatment. Based on this high-quality provisional,

•

Patient satisfaction

the patient can establish an opinion of the treat­

•

Appearance of the restoration in relation to the face and smile

ment before the definitive restoration is completed (since a minimum of 10 days is needed before the

•

These impressions of the provisional prosthesis in

•

Emergence of the buccal surfaces of the teeth in

•

Shape of the prosthetic teeth due to wear or the

relation to the lip profile

the mouth are used, along with slides of the inter­ mediate situation, to make only minor changes re­

presence of composite restorations

lated to shape and soft tissue integration.

In situ eva luation

•

Condition of the soft tissues and maturity of the

•

Integration of the provisional restoration with

interdental papillae adjacent teeth

An objective evaluation of the provisional restora­ tion or diagnostic mock-up in situ cannot be con­ ducted in a single appointment, since the restora­

Position of the incisal edge relative to the contour of the lower lip and of the labial commissure

final impressions can be taken) (Figs 8-93 to 8-95).

•

Occlusion

tion generally proposes a significant change. ••-20

Each parameter should be photographed to give

The preoperative situation frequently results from a

the clinician and dental technician the opportunity

slow progressive deterioration of the volume and

to assess the overall situation in the laboratory dur­

shape of the teeth or the previous restoration. The

ing the next phase of the ceramic preparation and

patient is unlikely to immediately adapt to the new

determine the corrections, if any, to be made. If sig­

prosthesis because the new restorative parameters differ significantly from the pretreatment situation.

to prepare a new provisional prosthesis; the authors

In general, the prosthetic team should avoid adjust·

generally prefer to prepare the wax corrections direct-

ing the restoration in the first visit to allow the

ly on the provisional prosthesis and then ix the whole

patient the necessary time to grow accustomed to

prosthesis in an irreversible hydrocolloid impression.

the provisional restoration.

When minor changes are required, the corrections

The provisional prosthesis is evaluated through assessment of the following parameters:

B-70

nificant changes are required, it may be necessary

can be executed di rectly on the definitive ceramic work and evaluated during the bisque-bake try-in.

•

B-72

Figs 8-68 to 8-75 Provisional stratification. Fig 8-68 Suitably adapted diagnostic waxup. Fig 8-6g Molding phase o f dentin-type acrylic resin obtained from the silicone matrix. Figs 8-70 and 8-71 Silicone index showing the space available on the labial surfaces as the dentin material is reduced. Fig 8-72 Silicone index in place after sectioning in the sagittal direction. Fig 8-73 Dentin reduction completed with the incisal edge significantly reduced.

1

259

CHAPTER 8 Technical Considerations for Provisional Prostheses

.. treatment. Based on this high-quality provisional,

•

Patient satisfaction

the patient can establish an opinion of the treat­

•

Appearance of the restoration in relation to the face and smile

ment before the definitive restoration is completed (since a minimum of 10 days is needed before the

•

These impressions of the provisional prosthesis in

•

Emergence of the buccal surfaces of the teeth in

•

Shape of the prosthetic teeth due to wear or the

relation to the lip profile

the mouth are used, along with slides of the inter­ mediate situation, to make only minor changes re­

presence of composite restorations

lated to shape and soft tissue integration.

In situ eva luation

•

Condition of the soft tissues and maturity of the

•

Integration of the provisional restoration with

interdental papillae adjacent teeth

An objective evaluation of the provisional restora­ tion or diagnostic mock-up in situ cannot be con­ ducted in a single appointment, since the restora­

Position of the incisal edge relative to the contour of the lower lip and of the labial commissure

final impressions can be taken) (Figs 8-93 to 8-95).

•

Occlusion

tion generally proposes a significant change. ••-20

Each parameter should be photographed to give

The preoperative situation frequently results from a

the clinician and dental technician the opportunity

slow progressive deterioration of the volume and

to assess the overall situation in the laboratory dur­

shape of the teeth or the previous restoration. The

ing the next phase of the ceramic preparation and

patient is unlikely to immediately adapt to the new

determine the corrections, if any, to be made. If sig­

prosthesis because the new restorative parameters differ significantly from the pretreatment situation.

to prepare a new provisional prosthesis; the authors

In general, the prosthetic team should avoid adjust·

generally prefer to prepare the wax corrections direct-

ing the restoration in the first visit to allow the

ly on the provisional prosthesis and then ix the whole

patient the necessary time to grow accustomed to

prosthesis in an irreversible hydrocolloid impression.

the provisional restoration.

When minor changes are required, the corrections

The provisional prosthesis is evaluated through assessment of the following parameters:

B-70

nificant changes are required, it may be necessary

can be executed di rectly on the definitive ceramic work and evaluated during the bisque-bake try-in.

•

B-72

Figs 8-68 to 8-75 Provisional stratification. Fig 8-68 Suitably adapted diagnostic waxup. Fig 8-6g Molding phase o f dentin-type acrylic resin obtained from the silicone matrix. Figs 8-70 and 8-71 Silicone index showing the space available on the labial surfaces as the dentin material is reduced. Fig 8-72 Silicone index in place after sectioning in the sagittal direction. Fig 8-73 Dentin reduction completed with the incisal edge significantly reduced.

1

259

CIAPl ER Technical Considerations for Provisional Prostheses

Fig 8-74 Photopotymerizing colors applied over the dentin layer. Fig 8-75 Molding phase of the enamel-type acrylic resin. Figs 8-76 to 8-78 Lines c � e ated using contact-detecting powder are useful for defining the shape of the restorations during the finishing phase. Figs 8-7g to 8-81 . FiniShed and polished prom1onal restorahons. Note the emergence profiles shown in the lateral views.

ZG

Fig 8-82 Provisional before insertion in the mouth. The reconstruction of the clinical case involves veneers on the central i n cisors and crowns on the lateral incisors. Fig 8-83 First provisional on 2.1 and 2.2 for whitening . The patient requested improvement i n the shape and brilliance of the teeth. Fig 8-84 Provisional in situ. The diagnostic planning done in the laboratory is evaluated direclly i n the mouth with the help of the provisional. Fig 8-85 View of the right maxillary incisors showing the anatomy of the restorations. Fig 8-86 View of the left max­ illary incisor. Note that the cervical area is no longer gray. as it was i n the previous restorative treatment.

261

CIAPl ER Technical Considerations for Provisional Prostheses

Fig 8-74 Photopotymerizing colors applied over the dentin layer. Fig 8-75 Molding phase of the enamel-type acrylic resin. Figs 8-76 to 8-78 Lines c � e ated using contact-detecting powder are useful for defining the shape of the restorations during the finishing phase. Figs 8-7g to 8-81 . FiniShed and polished prom1onal restorahons. Note the emergence profiles shown in the lateral views.

ZG

Fig 8-82 Provisional before insertion in the mouth. The reconstruction of the clinical case involves veneers on the central i n cisors and crowns on the lateral incisors. Fig 8-83 First provisional on 2.1 and 2.2 for whitening . The patient requested improvement i n the shape and brilliance of the teeth. Fig 8-84 Provisional in situ. The diagnostic planning done in the laboratory is evaluated direclly i n the mouth with the help of the provisional. Fig 8-85 View of the right maxillary incisors showing the anatomy of the restorations. Fig 8-86 View of the left max­ illary incisor. Note that the cervical area is no longer gray. as it was i n the previous restorative treatment.

261

Technical Considerations for Provisional Prostheses

Fig 8-87 Pre operative view of clinical case. Fig 8-88 Following the diagnostic wax up in the laboratory. distalization of the papilla between the _ _ mmllary nght c ! ntral and lateral 1nc1 sors was planned. Fig 8-8g Preparation for tissue conditioning is achieved by removing plaster from _ the Internal g1ng1val port1on """g a sphemal bur. resulting in the fabrication of a larger provisional in relation to the existing gingival _ g tiSsues. Fig 8- o Prom1onal 1n the mouth shows a tiSsue ISChemia corresponding to the area where plaster was removed from the cast.

Ul

Fig 8- gl Provisional now perfectly adapted to the oral cavity following tissue conditioning. Fig 8- g2 Detail of the provisional after tissue con­ ditioning. Fig 8- gJ Cast showing plans for tissue conditioning for a pontic. Fig 8-4 Edentulous site following tissue conditioning. Fig 8-gs Pontic in place. perfectly adapted to give the esthetic appearance of a good emergence profile. even though the restoration does not extend sub­ gingivally.

23

Technical Considerations for Provisional Prostheses

Fig 8-87 Pre operative view of clinical case. Fig 8-88 Following the diagnostic wax up in the laboratory. distalization of the papilla between the _ _ mmllary nght c ! ntral and lateral 1nc1 sors was planned. Fig 8-8g Preparation for tissue conditioning is achieved by removing plaster from _ the Internal g1ng1val port1on """g a sphemal bur. resulting in the fabrication of a larger provisional in relation to the existing gingival _ g tiSsues. Fig 8- o Prom1onal 1n the mouth shows a tiSsue ISChemia corresponding to the area where plaster was removed from the cast.

Ul

Fig 8- gl Provisional now perfectly adapted to the oral cavity following tissue conditioning. Fig 8- g2 Detail of the provisional after tissue con­ ditioning. Fig 8- gJ Cast showing plans for tissue conditioning for a pontic. Fig 8-4 Edentulous site following tissue conditioning. Fig 8-gs Pontic in place. perfectly adapted to give the esthetic appearance of a good emergence profile. even though the restoration does not extend sub­ gingivally.

23

CHAPTER 8 Technical Considerations for Provisional Prostheses

REFEREN CES

7.

Brisman S. Esthetics: A comparison of dentists' and

13.

patients' concepts. J Am Dent Assoc t98o:too:345-352. 1.

2.

Levinson NLA. Psychologic acets of esthetic dental

8. Albino JE. Tedesco LA. Conny DJ. Patient perceptions of

care: A developmental perspective. J Prosthet Dent

dental-facial esthetics: Shared concerns in orthodontics

1990:64:486-491.

and prosthodontics. J Prosthet Dent 1984:5 2:9-13.

Ellmann ). Compression formed plaster shells for tem­

3-

concetto

Krug RS. Multiple use of plastic template in fixed prosthodontics. J Prosthet Dent 1973:30:745-748.

s.

14.

trattamento estetico.

Dent

integrated approach to periodontics and restorative

G,

Sampalmieri

F, Mattioli

Belmonte

dentistry. Dent Clin North Am t98o:24:285-303.

Liu Cl. Use of a modiied ovate pontic in areas of ridge

Dialogue

15.

isher D, Shillingburg HT Jr. Dewhirst RB. Indirect tem­

16.

tion of provisional restorations. lnt

Miller MB. Ovate pontics: The natural tooth replacement.

4:33 2-336. 20.

Pract Periodontics Aesthet Dent 1996:8:140.

porary restorations. J Am Dent Assoc 1971;82: 16o-t63. 11. Albergo G. Accarisi E. Sampalmieri F, Bedini R. Andreana

Emtiaz S, Tarnow DP. Processed acrylic resin provision­

marginal gaps of light-polymerized and autopolymer·

Ogawa T, Ai2awa S, Tanaka M, atsuya S, Hasegawa A.

82: 16!-!66.

Koyano K. Efect of water temperature on the it of pro­

1997:76(special issue):279·

visional

Capelli M, Albergo G, Casolari L, Sampalmieri F, Bedini

tions in restorative dentistry: The blueprint for success.

R. Antibacterial activity of a resin: A qualitative study. J

J Can Dent Assoc 1999:65:272-275-

Dent Res 1998:77:1389.

Dubois R). Kyriakakis P, Weiner S, Vaidyanathan TK. Efects of occlusal loading and thermocycling on the

ized resin provisional crowns. I Prosthet Dent 1999;

performance in acrylic resin (abstract 2128). J Dent Res

12.

Prosthodont 1991;

Prosthet Dent 1998:79:484-488.

5. Efect of antimicrobical ingredients on mechanical

Assoc 1998:26:t21-127.

I

al restoration with lingual cast metal ramewor.. J

Cho GC, Donovan TE. Chee NL. Clinical experiences

17.

Moulding MB, Loney RW. The efect of cooling tech­ niques on intrapulpal temperature during direct abrica­

2004;16:273-2Bt: discussion 282-283.

with bonded porcelain laminate veneers. J Cal Dent

6. Donovan TE, Cho GC. Diagnostic provisional restora·

19.

defects: A repon of two cases. J Esthet Restor Dent

200t;5:44o-453· 10.

4- Preston JD. A systematic approach to the control of

esthetic form. J Prosthet Dent 1976:35 :393-402.

del

18. Youdelis RA, Faucher R. Provisional restorations: An

Albergo

acrylic resin. J Dent Res t997:76:11o3.

9- Romeo G. II prowisorio diagnostico per comprendere it

porary splints. Dent Dig 1971:77:334-339·

M,

Andreana S. echanical performance of some dental

crown

margins

during

polymerization.

I

Prosthet Dent 1999:B2:6sH61.

25

CHAPTER 8 Technical Considerations for Provisional Prostheses

REFEREN CES

7.

Brisman S. Esthetics: A comparison of dentists' and

13.

patients' concepts. J Am Dent Assoc t98o:too:345-352. 1.

2.

Levinson NLA. Psychologic acets of esthetic dental

8. Albino JE. Tedesco LA. Conny DJ. Patient perceptions of

care: A developmental perspective. J Prosthet Dent

dental-facial esthetics: Shared concerns in orthodontics

1990:64:486-491.

and prosthodontics. J Prosthet Dent 1984:5 2:9-13.

Ellmann ). Compression formed plaster shells for tem­

3-

concetto

Krug RS. Multiple use of plastic template in fixed prosthodontics. J Prosthet Dent 1973:30:745-748.

s.

14.

trattamento estetico.

Dent

integrated approach to periodontics and restorative

G,

Sampalmieri

F, Mattioli

Belmonte

dentistry. Dent Clin North Am t98o:24:285-303.

Liu Cl. Use of a modiied ovate pontic in areas of ridge

Dialogue

15.

isher D, Shillingburg HT Jr. Dewhirst RB. Indirect tem­

16.

tion of provisional restorations. lnt

Miller MB. Ovate pontics: The natural tooth replacement.

4:33 2-336. 20.

Pract Periodontics Aesthet Dent 1996:8:140.

porary restorations. J Am Dent Assoc 1971;82: 16o-t63. 11. Albergo G. Accarisi E. Sampalmieri F, Bedini R. Andreana

Emtiaz S, Tarnow DP. Processed acrylic resin provision­

marginal gaps of light-polymerized and autopolymer·

Ogawa T, Ai2awa S, Tanaka M, atsuya S, Hasegawa A.

82: 16!-!66.

Koyano K. Efect of water temperature on the it of pro­

1997:76(special issue):279·

visional

Capelli M, Albergo G, Casolari L, Sampalmieri F, Bedini

tions in restorative dentistry: The blueprint for success.

R. Antibacterial activity of a resin: A qualitative study. J

J Can Dent Assoc 1999:65:272-275-

Dent Res 1998:77:1389.

Dubois R). Kyriakakis P, Weiner S, Vaidyanathan TK. Efects of occlusal loading and thermocycling on the

ized resin provisional crowns. I Prosthet Dent 1999;

performance in acrylic resin (abstract 2128). J Dent Res

12.

Prosthodont 1991;

Prosthet Dent 1998:79:484-488.

5. Efect of antimicrobical ingredients on mechanical

Assoc 1998:26:t21-127.

I

al restoration with lingual cast metal ramewor.. J

Cho GC, Donovan TE. Chee NL. Clinical experiences

17.

Moulding MB, Loney RW. The efect of cooling tech­ niques on intrapulpal temperature during direct abrica­

2004;16:273-2Bt: discussion 282-283.

with bonded porcelain laminate veneers. J Cal Dent

6. Donovan TE, Cho GC. Diagnostic provisional restora·

19.

defects: A repon of two cases. J Esthet Restor Dent

200t;5:44o-453· 10.

4- Preston JD. A systematic approach to the control of

esthetic form. J Prosthet Dent 1976:35 :393-402.

del

18. Youdelis RA, Faucher R. Provisional restorations: An

Albergo

acrylic resin. J Dent Res t997:76:11o3.

9- Romeo G. II prowisorio diagnostico per comprendere it

porary splints. Dent Dig 1971:77:334-339·

M,

Andreana S. echanical performance of some dental

crown

margins

during

polymerization.

I

Prosthet Dent 1999:B2:6sH61.

25

C H A P T E R

9

C U S T O M IM P RESS I O N TRAY S A N D IM P RESS I O N MATER IAL S FIG 9-1

I

n dental prosthetics, the impression is essential

sizes to accommodate almost every clinical situa­

for fabricating a restoration. If the proper proce­

tion, eg, polystyrene, plastic, aluminum, or steel;

dures are not followed, the clinician may intro­

perforated or nonperforated; etc (Figs 9-1 to 9-3).

duce errors or distortions that cannot be eliminated

During setting, the chemical reaction of the paste

or corrected in subsequent stages. The impression

and catalyst can lead to shrinkage, which alters the

communicates the clinical condition of the patient's

shape and dimension and compromises the preci­

mouth

to the dental technician; therefore, an

sion of the impression. To minimize shrinkage, the

impression that faithfully records the details of a

thickness of impression material should be ade­

dental arch leads to a well-adapted restoration. A

quate to accurately record every stressed clinical sit­

precise impression can be made using several dif­

uation (natural undercuts, convex, natural tooth),

ferent types of materials and impression trays. The

but no thickerJ·•

FIG 9-2

FIG 9-3

clinician must understand the techniques and fac­ tors that ensure an accurate impression. The follow­ ing general overview details the procedures typical­

Custom i m p ression trays

ly used by the authors.

Clinicians can regulate the thickness of an impres­

I M PRES S I O N TRAYS

photopolymerizable resin. By molding a 3-mm-thick

sion by making custom impression trays out of

An impression material generally consists of a paste

zu

sheet of soft wax around the dental arch on a diag­ nostic cast before molding the resin, the clinician

and a catalyst that gradually harden when mixed

can create the ideal thickness for the impression

together. Once the paste and catalyst come in con­

material (Fig 9-4). Some authorsS-6 do not agree that

tact, the impression material begins to increase in

custom trays are necessary for precise impressions,

viscosity and slowly develops elasticity. This gradual

believing that the degree of shrinkage of impression

hardening permits the clinician to position the mate­

materials is clinically insignificant. However, custom

rial while it is still in an plastic state (working stage)

trays can mitigate another important phenomenon­

before it hardens into a elastic state. '·2

distortion caused by undercuts.

While it is in a plastic state, the impression mate­

In the authors' opinion, one of the greatest

rial is placed in a suitable tray for the arch being

stresses on impression materials is the presence of

impressed. Manufacturers fabricate impression trays

undercuts, for example, found in the natural anato­

out of different materials and in various shapes and

my of intact maxillary teeth. Apical to the initial pro- ..

FIG 9-4

FIG 9-5

Figs g-1 to g -3 Stock trays. Fig g -1 Polystyrene tray. These trays are very flexible and are unsuitable for precision impressions. ' However. they can be used to make a full plaster impression of implants because they can be cut easily afler casting. Fig g -2 Perforated aluminum tray. Perforated trays. including those in steel. are unsuitable for impression taking because the perforations can create anomalies in the impres­ sion.1 Fig g-3 Solid steel tray. These trays must be boxed in with wax to ensure good adaptation. Fig g _4 Sheet of spacing wax that is molded direclly on top of the diagnostic cast. Its thickness !generally 3 mml creates the ideal space for the impression material. Fig g_s Tooth prepa­ ration for a complete crown. The horizontal retraction creates a pronounced undercut formed by the natural taper of the root.

217

C H A P T E R

9

C U S T O M IM P RESS I O N TRAY S A N D IM P RESS I O N MATER IAL S FIG 9-1

I

n dental prosthetics, the impression is essential

sizes to accommodate almost every clinical situa­

for fabricating a restoration. If the proper proce­

tion, eg, polystyrene, plastic, aluminum, or steel;

dures are not followed, the clinician may intro­

perforated or nonperforated; etc (Figs 9-1 to 9-3).

duce errors or distortions that cannot be eliminated

During setting, the chemical reaction of the paste

or corrected in subsequent stages. The impression

and catalyst can lead to shrinkage, which alters the

communicates the clinical condition of the patient's

shape and dimension and compromises the preci­

mouth

to the dental technician; therefore, an

sion of the impression. To minimize shrinkage, the

impression that faithfully records the details of a

thickness of impression material should be ade­

dental arch leads to a well-adapted restoration. A

quate to accurately record every stressed clinical sit­

precise impression can be made using several dif­

uation (natural undercuts, convex, natural tooth),

ferent types of materials and impression trays. The

but no thickerJ·•

FIG 9-2

FIG 9-3

clinician must understand the techniques and fac­ tors that ensure an accurate impression. The follow­ ing general overview details the procedures typical­

Custom i m p ression trays

ly used by the authors.

Clinicians can regulate the thickness of an impres­

I M PRES S I O N TRAYS

photopolymerizable resin. By molding a 3-mm-thick

sion by making custom impression trays out of

An impression material generally consists of a paste

zu

sheet of soft wax around the dental arch on a diag­ nostic cast before molding the resin, the clinician

and a catalyst that gradually harden when mixed

can create the ideal thickness for the impression

together. Once the paste and catalyst come in con­

material (Fig 9-4). Some authorsS-6 do not agree that

tact, the impression material begins to increase in

custom trays are necessary for precise impressions,

viscosity and slowly develops elasticity. This gradual

believing that the degree of shrinkage of impression

hardening permits the clinician to position the mate­

materials is clinically insignificant. However, custom

rial while it is still in an plastic state (working stage)

trays can mitigate another important phenomenon­

before it hardens into a elastic state. '·2

distortion caused by undercuts.

While it is in a plastic state, the impression mate­

In the authors' opinion, one of the greatest

rial is placed in a suitable tray for the arch being

stresses on impression materials is the presence of

impressed. Manufacturers fabricate impression trays

undercuts, for example, found in the natural anato­

out of different materials and in various shapes and

my of intact maxillary teeth. Apical to the initial pro- ..

FIG 9-4

FIG 9-5

Figs g-1 to g -3 Stock trays. Fig g -1 Polystyrene tray. These trays are very flexible and are unsuitable for precision impressions. ' However. they can be used to make a full plaster impression of implants because they can be cut easily afler casting. Fig g -2 Perforated aluminum tray. Perforated trays. including those in steel. are unsuitable for impression taking because the perforations can create anomalies in the impres­ sion.1 Fig g-3 Solid steel tray. These trays must be boxed in with wax to ensure good adaptation. Fig g _4 Sheet of spacing wax that is molded direclly on top of the diagnostic cast. Its thickness !generally 3 mml creates the ideal space for the impression material. Fig g_s Tooth prepa­ ration for a complete crown. The horizontal retraction creates a pronounced undercut formed by the natural taper of the root.

217

CHAPTER 9 Custom I mpression Trays and Impression Materials

.. trusion of the tooth in the area of the dental alve­

around the vestibular fornix to delimit the edge of

oli, there is a depression of varying extent in the

the tray (Figs 9-8 to 9-10). Occlusal stops are made

area of the vestibular fornix; clinical treatment to

by creating small depressions, with adequate exten­

modify the shape and length of the clinical crown

sions, in the anterior hard palate and edentulous

can reveal natural undercuts (Fig 9-5). Undercuts can

areas. A sufficient number of well-positioned stops

also be erroneously created during tooth prepara­

are needed to provide tripod-like stability; if there

tion, a risk that is often underestimated as a poten­

are no edentulous areas, additional stops can be

tial cause of the impression distotion that leads to

made against the palatal mucosa at the level of the

poor adaptation of the restoration. The clinician

maxillary first molars. If this is not possible for ana­

must be aware of all undercuts while preparing the

tomic reasons (eg, a lack of edentulous areas in the

custom tray and block out those areas with addi­

mandible or the presence of an accentuated palate),

tional spacing wax. By leaving more room in the cus­

the cusps of teeth in noncritical areas {ie, those not

tom tray for a thicker application of material to the

afecting functional movements, such as the buccal

undercuts, the impression should be able to with­

cusps of maxillay teeth and the lingual cusps of man­

stand the force required to remove it from the oral

dibular teeth) can be used as support for the tripod.

cavity without laceration or stretching. For these rea­

Light-curing resin (MultiTray, 3M ESPE) is used to

sons, the clinician should use custom trays to obtain

make the tray. The stops and detachment wings are

a suitable impression.'

prepared first by placing small amounts of resin in

FIG 9-6

FIG 9-7

FIG 9-8

FIG 9-9

FIG 9-10

FIG 9-11

the wax depressions that are then polymerized for 5 Fabrication of the custom i m p ression tray

ESPE) (Fig 9-11) so they will adhere to the rest of the

ing the stone cast, which will be marked according

resin.

to the planned form and dimension of the custom

The main sheet of resin is applied over the wax

tray and to prevent material from locking into the

and the prepolymerized stops and carefully adapted

marked undercuts. Using a graphite pencil or wax

to the design of the tray. Once the central handle

crayon, the clinician traces the limits of the tray's

and the detachment wings are shaped, the custom­

apical extension taking care to avoid the involve­

made tray, prepared on the plaster model, is placed

ment of the vestibular fornix and to include the area 2

m m apical to the inish line (Figs 9-6 and 9-7).

i n the light-curing unit for 5 minutes (Figs 9-12 to

9-14). The tray undergoes two polymerizations of s

To obtain ideal thickness. a 3-mm wax sheet is

minutes each, first for the exterior and then for the

heated to 40°C and then molded to the diagnostic

interior, without removing the spacing wax. The spac­

cast, following the guide marks. Additional wax is

ing wax is finally removed, and the tray is placed in

adapted to areas of pronounced natural undercuts so

the light-polymerizing unit for another 5 minutes to

that the tray will withstand the extra stress in these

cure the interior surface (Fig 9-15).

areas. Thus, the custom impression tray will not be of uniform thickness but of controlled thickness.

21

to 10 seconds in a light-curing unit (Multilight, 3M

To make a custom impression tray, stat by evaluat­

Once the polymerization is finished, the tray must be evaluated on the cast to ensure that the stops

Once the wax sheet has been adapted to the

make proper contact with the desired areas (Figs

plaster cast, the clinician uses a laboratory knife to

9-16 and 9-17) and the detachment wings and the

trim excess wax from the cast according to plan and

han dle are correctly positioned (Fig 9-18). Using t u n g- �

Fi gs 9-6 and 9-7 Graphite pencil or a wax crayon is used to mark the placement of occlusal slops and the borders of the custom lny that extend 2 mm apical to the finish line. However. in areas of the mouth thai are not involved in the restoration. the impression should not exlend beyond the finish line to minimize the number of natural undercuts in the impression. Fig 9-8 and 9-9 A laboratory scalpel is used to cut the spacing wax at the tray limits marked in graphite and in the areas for occlusal stops. Fig g -10 Cut-out areas are filled in with pieces of light-curing resin to ereale lhe occlusal stops for sealing lhe impression. Fig 9-ll lighl-curing unit. The occlusal stops are polymerized for a few sec­ onds so that the partially hardened resin will adhere to the main sheet of resin.

2"

CHAPTER 9 Custom I mpression Trays and Impression Materials

.. trusion of the tooth in the area of the dental alve­

around the vestibular fornix to delimit the edge of

oli, there is a depression of varying extent in the

the tray (Figs 9-8 to 9-10). Occlusal stops are made

area of the vestibular fornix; clinical treatment to

by creating small depressions, with adequate exten­

modify the shape and length of the clinical crown

sions, in the anterior hard palate and edentulous

can reveal natural undercuts (Fig 9-5). Undercuts can

areas. A sufficient number of well-positioned stops

also be erroneously created during tooth prepara­

are needed to provide tripod-like stability; if there

tion, a risk that is often underestimated as a poten­

are no edentulous areas, additional stops can be

tial cause of the impression distotion that leads to

made against the palatal mucosa at the level of the

poor adaptation of the restoration. The clinician

maxillary first molars. If this is not possible for ana­

must be aware of all undercuts while preparing the

tomic reasons (eg, a lack of edentulous areas in the

custom tray and block out those areas with addi­

mandible or the presence of an accentuated palate),

tional spacing wax. By leaving more room in the cus­

the cusps of teeth in noncritical areas {ie, those not

tom tray for a thicker application of material to the

afecting functional movements, such as the buccal

undercuts, the impression should be able to with­

cusps of maxillay teeth and the lingual cusps of man­

stand the force required to remove it from the oral

dibular teeth) can be used as support for the tripod.

cavity without laceration or stretching. For these rea­

Light-curing resin (MultiTray, 3M ESPE) is used to

sons, the clinician should use custom trays to obtain

make the tray. The stops and detachment wings are

a suitable impression.'

prepared first by placing small amounts of resin in

FIG 9-6

FIG 9-7

FIG 9-8

FIG 9-9

FIG 9-10

FIG 9-11

the wax depressions that are then polymerized for 5 Fabrication of the custom i m p ression tray

ESPE) (Fig 9-11) so they will adhere to the rest of the

ing the stone cast, which will be marked according

resin.

to the planned form and dimension of the custom

The main sheet of resin is applied over the wax

tray and to prevent material from locking into the

and the prepolymerized stops and carefully adapted

marked undercuts. Using a graphite pencil or wax

to the design of the tray. Once the central handle

crayon, the clinician traces the limits of the tray's

and the detachment wings are shaped, the custom­

apical extension taking care to avoid the involve­

made tray, prepared on the plaster model, is placed

ment of the vestibular fornix and to include the area 2

m m apical to the inish line (Figs 9-6 and 9-7).

i n the light-curing unit for 5 minutes (Figs 9-12 to

9-14). The tray undergoes two polymerizations of s

To obtain ideal thickness. a 3-mm wax sheet is

minutes each, first for the exterior and then for the

heated to 40°C and then molded to the diagnostic

interior, without removing the spacing wax. The spac­

cast, following the guide marks. Additional wax is

ing wax is finally removed, and the tray is placed in

adapted to areas of pronounced natural undercuts so

the light-polymerizing unit for another 5 minutes to

that the tray will withstand the extra stress in these

cure the interior surface (Fig 9-15).

areas. Thus, the custom impression tray will not be of uniform thickness but of controlled thickness.

21

to 10 seconds in a light-curing unit (Multilight, 3M

To make a custom impression tray, stat by evaluat­

Once the polymerization is finished, the tray must be evaluated on the cast to ensure that the stops

Once the wax sheet has been adapted to the

make proper contact with the desired areas (Figs

plaster cast, the clinician uses a laboratory knife to

9-16 and 9-17) and the detachment wings and the

trim excess wax from the cast according to plan and

han dle are correctly positioned (Fig 9-18). Using t u n g- �

Fi gs 9-6 and 9-7 Graphite pencil or a wax crayon is used to mark the placement of occlusal slops and the borders of the custom lny that extend 2 mm apical to the finish line. However. in areas of the mouth thai are not involved in the restoration. the impression should not exlend beyond the finish line to minimize the number of natural undercuts in the impression. Fig 9-8 and 9-9 A laboratory scalpel is used to cut the spacing wax at the tray limits marked in graphite and in the areas for occlusal stops. Fig g -10 Cut-out areas are filled in with pieces of light-curing resin to ereale lhe occlusal stops for sealing lhe impression. Fig 9-ll lighl-curing unit. The occlusal stops are polymerized for a few sec­ onds so that the partially hardened resin will adhere to the main sheet of resin.

2"

HI Custom Impression Trays and Impression Materials

. sten carbide burs with a crossover cut (no. H77 EF,

When necessary (eg, in cases with pronounced under­

H79 EF, H351 EF; Komet), the rough tray is finished

cuts), a wax net designed to make metallic supports

by removing the excess material and smoothing the

for prosthetic frames can be placed over the wax

sharp edges and irregularities. The internal surface

foundation to enhance microretention (Figs 9-20 to

of the tray is carefully washed with a grease-cutting

9-22). When pressed onto the sheet of spacing wax,

product (eg, rectified benzine) to remove the oily

this wax-net layer creates small raised bumps that

residue left by the wax.

will be transferred to the interior surface of the tray

Elastomer adhesion is a constant problem in im­

(Fig 9-23).

pression taking because impression materials with

The tray must be tested in the patient's mouth.

strong internal cohesion, such as addition silicones

At least 30 minutes before the impression is taken,

and polyethers, do not adhere well to the resin sur­

an adhesive that is compatible with the impression

face of the tray.8 To improve the adhesion when

material must be applied to the tray. A minimum of

using polyethers. a groove can be made with a

15 minutes is needed to ensure that the adhesive is

small-diameter tungsten carbide bur on the interior

completely dry9; if it is wet, the adhesive will insu­

surface directly below the edge of the tray (Fig 9-19).

late rather than bond (Fig 9-24).

Ftgs g.12 and g.13 Moldtng of the sheet of restn dtroctly on the spacing wax and the partially polymerized stops. Ftg g-14 After lha handle and detachment wings are made. the top and bottom surfaces of the tray are polymerized for 5 minutes each with­ out removtng lhe spacing wax . Ftg 9-15 After removal of the spacing wax. the interior surface of the hardened impression tray is cured for an addthonal 5 mtnulu Figs 9·16 and 9-17 Fintshad custom tray Sealed on tho cast. the principal occlusal stops

..

rest on the soft tissue. It is preferable to establish occlusal stops on the mucous areas of the palate or tn edentulous Sites. rather than on the surface of teeth. Fig g. 18 Internal surface of the custom tray after cleaning with rectified benz1nt and finishing the margins and borders. fig g-19 Mechanical retention groove for the impression material. Fig 9-20 Sheet of wax netting normally used in fabricallon of metallic frames for removable partial prostheses. Figs 9-21 and g-22 The wax net pattern increases microretenlion between elastomer tmpression materials and the resin material of the custom tray Elastomers have high cohesion and therefore adhere poorly to many surfaces Ftg g.23 High-magntftealion shows the close mechanical adaptation between an elastomer impresSion material and the reSin of the custom tray The liquid adhesive layer between the elastomer and resin increases adhesion Fig g-24 Polyelher-compallble adhesive The adhesive is applied with a brush to the internal surface of the custom tray to facilitate adheSion of the impression matenal lo the light-curing resin 211

HI Custom Impression Trays and Impression Materials

. sten carbide burs with a crossover cut (no. H77 EF,

When necessary (eg, in cases with pronounced under­

H79 EF, H351 EF; Komet), the rough tray is finished

cuts), a wax net designed to make metallic supports

by removing the excess material and smoothing the

for prosthetic frames can be placed over the wax

sharp edges and irregularities. The internal surface

foundation to enhance microretention (Figs 9-20 to

of the tray is carefully washed with a grease-cutting

9-22). When pressed onto the sheet of spacing wax,

product (eg, rectified benzine) to remove the oily

this wax-net layer creates small raised bumps that

residue left by the wax.

will be transferred to the interior surface of the tray

Elastomer adhesion is a constant problem in im­

(Fig 9-23).

pression taking because impression materials with

The tray must be tested in the patient's mouth.

strong internal cohesion, such as addition silicones

At least 30 minutes before the impression is taken,

and polyethers, do not adhere well to the resin sur­

an adhesive that is compatible with the impression

face of the tray.8 To improve the adhesion when

material must be applied to the tray. A minimum of

using polyethers. a groove can be made with a

15 minutes is needed to ensure that the adhesive is

small-diameter tungsten carbide bur on the interior

completely dry9; if it is wet, the adhesive will insu­

surface directly below the edge of the tray (Fig 9-19).

late rather than bond (Fig 9-24).

Ftgs g.12 and g.13 Moldtng of the sheet of restn dtroctly on the spacing wax and the partially polymerized stops. Ftg g-14 After lha handle and detachment wings are made. the top and bottom surfaces of the tray are polymerized for 5 minutes each with­ out removtng lhe spacing wax . Ftg 9-15 After removal of the spacing wax. the interior surface of the hardened impression tray is cured for an addthonal 5 mtnulu Figs 9·16 and 9-17 Fintshad custom tray Sealed on tho cast. the principal occlusal stops

..

rest on the soft tissue. It is preferable to establish occlusal stops on the mucous areas of the palate or tn edentulous Sites. rather than on the surface of teeth. Fig g. 18 Internal surface of the custom tray after cleaning with rectified benz1nt and finishing the margins and borders. fig g-19 Mechanical retention groove for the impression material. Fig 9-20 Sheet of wax netting normally used in fabricallon of metallic frames for removable partial prostheses. Figs 9-21 and g-22 The wax net pattern increases microretenlion between elastomer tmpression materials and the resin material of the custom tray Elastomers have high cohesion and therefore adhere poorly to many surfaces Ftg g.23 High-magntftealion shows the close mechanical adaptation between an elastomer impresSion material and the reSin of the custom tray The liquid adhesive layer between the elastomer and resin increases adhesion Fig g-24 Polyelher-compallble adhesive The adhesive is applied with a brush to the internal surface of the custom tray to facilitate adheSion of the impression matenal lo the light-curing resin 211

CHAPTER 9 Custom I mpression Trays and Impression Materials

• CHARACTER I STICS OF I M PRESSION

M ATER IALS FOR FIXED

• Flu i d ity and viscosity

does not alter their precision or accurate reproduc­ tion of the details. Many authors have recognized

polyvinyl siloxanes and polyesters have greater co· hesion than adhesion (ie, poor wetting), while hydro­

the need to disi nfect impressions as a precaution to

Fluidity measures a material's capacity to insinuate

remove any pathogens that may have been present

itself into the minute spaces of an object and there­

good wetting). This means that when polyvinyl silox­

i n the oral cavity.•6·'' A number of scientific studies

by faithfully reproduce its smallest details. Fluidity is

anes and polyesters are used, the clinician should

The impression communicates all the parameters

have been performed to evaluate the effect of vari­

a characteristic found primarily in detail materials,

add an adhesive to ensure that the material will

and details needed by the dental technician to cor­

ous disinfectants on impression materials. In a sur­

which are generally used directly in the dentogingi­

adhere to the impression tray. Most manufacturers

RESTORATI O N S

colloids have greater adhesion than cohesion (ie,

rectly execute a fixed restoration. In practical terms,

vey of im pression disinfection in 400 US dental lab­

val sulcus to reproduce the finish line and the intact

add substances to impression materials to reduce

the impression is a negative or inverse form of the

oratories, Kugel et al'8 found that only 44% of

tooth structure beyond. Conversely, support materi­

surface tension. Wettability is affected by disinfec­

prepared tooth. The impression must be a faithful

impressions were disinfected directly by clinicians.

als are classified according to their viscosity (high,

tion 2 1·30-3' but the effed is not clinically significant.

reproduction of the preparation and clinical situa­

Of these, the modality was undocumented in 23%

medium, and low) and function to suppot and

tion, free from alterations, which are often imper­

and the time of immersion was undocumented in

guide the low-viscosity detail materials. The viscos­

ceptible and frequently caused by distortion of the

47°/o. The effects of the various disinfectant modali­

ity of support materials is determined by placing 0.5

i mpression materials'0 (Figs 9-25 and 9-26).

Elastic me mory

ties on different impression materials are well docu­

ml of the material on two flat plates (ISO 4823). Ten

Elastic memory refers to a material's capacity to

Some clinicians and dental technicians subscribe

mented.'9-2S Following disinfection, in solutions con­

seconds after extrusion, the plates are subjected to

recover its original shape after it has

to the belief that impression materials are distotion

taining 2% glutaraldehyde (glyoxal glutaraldehyde,

1.5 N for 30 seconds. High- and very high-viscosity

deformed. The greater the degree of deformity, the

proof. The literature is illed with in vitro studies"-'3

phenol glutaraldehyde) or 5 - 25°/o sodium hypochlo­

materials yield a diameter of less than 35 mm,

more time that should pass before pouring the

demonstrating that polyethers and especially poly­

rite for periods ranging from 10 to 30 minutes,26 for

medium-viscosity materials yield a diameter of 31 to

stone impression. There is no codified system to

vinyl siloxanes are stable, provide accurate surface

example, impression materials generally maintain

41 mm, and low-viscosity materials yield a diameter

define the degree and type of impression deforma­

details, and resist deformation. Without disputing

their clinical acceptability and the precision of the

of more than 36 mm.

tion or the period of time to wait for the material to

their validity, the authors believe such studies do

impression. However, Johnson et al27 evaluated the

Viscosity correlates with accuracy, resistance to

recover its original shape before pouring a stone

not take into account the diferent situations that

dimensions of various materials after disinfection

deformation, dimensional stability, and tear resis­

cast. However, for materials that have a suitable

arise in clinical practice. In vivo, the elasticity limit

and found that irreversible hydrocolloids expanded

tance but is unfavorable for detail precision and

dimensional stability, manuadurers have empha­

of impression materials is often exceeded,' thus

1.4 to 1.7 �m buccolingually, polyvinyl siloxanes ex­

ease of handling.8 Hardness, commonly expressed in

sized precise minimum and maximum time periods

shore units, varies over time, increasing after 15

minutes, 1 hour, and 24 hours (see the section on

that must elapse before a cast is poured.'

16 �m.

polyethers later in this chapter). This property influ­

deformation: that is, a material with minimal elastic

compromising the original dimensions.

Detail reproduction and disi nfection

panded 6 to 8 �m. and polyethers expanded 11 to For purposes of clinical evaluation, impression ma­

ences dimensional stability.

terials are classified as either elastic or nonelastic.'8

The American Dental Association (ADA) defines a

Elastic materials include reversible hydrocolloid (agar);

material as precise when it can reproduce the form

i rreversible hydrocolloid (alginate); and synthetics

of a 20-�m triangular sulcus (method for the preci­

such as polysulfide, condensation silicone, polyvinyl

sion verification according to DIN 13913)-4 (Figs 9-27

siloxanes, and polyether. Nonelastic materials include

been

Elastic memory is inversely related to permanent memoy will produce an impression with a signifi­ cant capacity for permanent deformation. To devel­

Wetta bility

op completely, elastic memory of an i mpression

Wettability, or low surface tension, describes how a

proportion to the size of the undercuts (Fig 9-30).

material requires a length of time that is in dired

and 9-28). Elastomers are generally able to repro­

plaster, thermoplastic pastes, zinc oxide-eugenol

material adapts to a contact surface. Wettability is

The elastic limit of elastomers is easily exceeded;

duce details the size of a few microns, and exact

pastes, and waxes. The requisite characteristics8 of

determined by the contact angle formed (theta)

even minimal tension or stress to the material while

reproduction of details requires a material to repro­

an impression material can be evaluated on the

when a given quantity of paste is positioned on a

taking the impression (eg, using force to remove the

�m. and in some cases,

basis of fluidity and viscosity, wettability, elastic

surface with a film of water: the smaller the angle of

impression from undercuts) will prevent the materi­

memory, thixotropy, dimensional stability, tear

contact, the better the material will adapt to the sur­

al from returning to its original shape and condition.

To prevent the transmission of infection, impres­

strength, hydrophilic behavior, thermal expansion,

ace to be impressed (Fig 9-29). The balance between

The ADA sets 2.5% as the limit of acceptability for

cohesion and adhesion is an impotant factor i n

permanent deformation'4 (Fig 9-31).

duce features as small as

2

even under 1 �m.•s sions must be disinfected using a treatment that

and application range.

.

.

determining a material's wettability. For example,

2

3

CHAPTER 9 Custom I mpression Trays and Impression Materials

• CHARACTER I STICS OF I M PRESSION

M ATER IALS FOR FIXED

• Flu i d ity and viscosity

does not alter their precision or accurate reproduc­ tion of the details. Many authors have recognized

polyvinyl siloxanes and polyesters have greater co· hesion than adhesion (ie, poor wetting), while hydro­

the need to disi nfect impressions as a precaution to

Fluidity measures a material's capacity to insinuate

remove any pathogens that may have been present

itself into the minute spaces of an object and there­

good wetting). This means that when polyvinyl silox­

i n the oral cavity.•6·'' A number of scientific studies

by faithfully reproduce its smallest details. Fluidity is

anes and polyesters are used, the clinician should

The impression communicates all the parameters

have been performed to evaluate the effect of vari­

a characteristic found primarily in detail materials,

add an adhesive to ensure that the material will

and details needed by the dental technician to cor­

ous disinfectants on impression materials. In a sur­

which are generally used directly in the dentogingi­

adhere to the impression tray. Most manufacturers

RESTORATI O N S

colloids have greater adhesion than cohesion (ie,

rectly execute a fixed restoration. In practical terms,

vey of im pression disinfection in 400 US dental lab­

val sulcus to reproduce the finish line and the intact

add substances to impression materials to reduce

the impression is a negative or inverse form of the

oratories, Kugel et al'8 found that only 44% of

tooth structure beyond. Conversely, support materi­

surface tension. Wettability is affected by disinfec­

prepared tooth. The impression must be a faithful

impressions were disinfected directly by clinicians.

als are classified according to their viscosity (high,

tion 2 1·30-3' but the effed is not clinically significant.

reproduction of the preparation and clinical situa­

Of these, the modality was undocumented in 23%

medium, and low) and function to suppot and

tion, free from alterations, which are often imper­

and the time of immersion was undocumented in

guide the low-viscosity detail materials. The viscos­

ceptible and frequently caused by distortion of the

47°/o. The effects of the various disinfectant modali­

ity of support materials is determined by placing 0.5

i mpression materials'0 (Figs 9-25 and 9-26).

Elastic me mory

ties on different impression materials are well docu­

ml of the material on two flat plates (ISO 4823). Ten

Elastic memory refers to a material's capacity to

Some clinicians and dental technicians subscribe

mented.'9-2S Following disinfection, in solutions con­

seconds after extrusion, the plates are subjected to

recover its original shape after it has

to the belief that impression materials are distotion

taining 2% glutaraldehyde (glyoxal glutaraldehyde,

1.5 N for 30 seconds. High- and very high-viscosity

deformed. The greater the degree of deformity, the

proof. The literature is illed with in vitro studies"-'3

phenol glutaraldehyde) or 5 - 25°/o sodium hypochlo­

materials yield a diameter of less than 35 mm,

more time that should pass before pouring the

demonstrating that polyethers and especially poly­

rite for periods ranging from 10 to 30 minutes,26 for

medium-viscosity materials yield a diameter of 31 to

stone impression. There is no codified system to

vinyl siloxanes are stable, provide accurate surface

example, impression materials generally maintain

41 mm, and low-viscosity materials yield a diameter

define the degree and type of impression deforma­

details, and resist deformation. Without disputing

their clinical acceptability and the precision of the

of more than 36 mm.

tion or the period of time to wait for the material to

their validity, the authors believe such studies do

impression. However, Johnson et al27 evaluated the

Viscosity correlates with accuracy, resistance to

recover its original shape before pouring a stone

not take into account the diferent situations that

dimensions of various materials after disinfection

deformation, dimensional stability, and tear resis­

cast. However, for materials that have a suitable

arise in clinical practice. In vivo, the elasticity limit

and found that irreversible hydrocolloids expanded

tance but is unfavorable for detail precision and

dimensional stability, manuadurers have empha­

of impression materials is often exceeded,' thus

1.4 to 1.7 �m buccolingually, polyvinyl siloxanes ex­

ease of handling.8 Hardness, commonly expressed in

sized precise minimum and maximum time periods

shore units, varies over time, increasing after 15

minutes, 1 hour, and 24 hours (see the section on

that must elapse before a cast is poured.'

16 �m.

polyethers later in this chapter). This property influ­

deformation: that is, a material with minimal elastic

compromising the original dimensions.

Detail reproduction and disi nfection

panded 6 to 8 �m. and polyethers expanded 11 to For purposes of clinical evaluation, impression ma­

ences dimensional stability.

terials are classified as either elastic or nonelastic.'8

The American Dental Association (ADA) defines a

Elastic materials include reversible hydrocolloid (agar);

material as precise when it can reproduce the form

i rreversible hydrocolloid (alginate); and synthetics

of a 20-�m triangular sulcus (method for the preci­

such as polysulfide, condensation silicone, polyvinyl

sion verification according to DIN 13913)-4 (Figs 9-27

siloxanes, and polyether. Nonelastic materials include

been

Elastic memory is inversely related to permanent memoy will produce an impression with a signifi­ cant capacity for permanent deformation. To devel­

Wetta bility

op completely, elastic memory of an i mpression

Wettability, or low surface tension, describes how a

proportion to the size of the undercuts (Fig 9-30).

material requires a length of time that is in dired

and 9-28). Elastomers are generally able to repro­

plaster, thermoplastic pastes, zinc oxide-eugenol

material adapts to a contact surface. Wettability is

The elastic limit of elastomers is easily exceeded;

duce details the size of a few microns, and exact

pastes, and waxes. The requisite characteristics8 of

determined by the contact angle formed (theta)

even minimal tension or stress to the material while

reproduction of details requires a material to repro­

an impression material can be evaluated on the

when a given quantity of paste is positioned on a

taking the impression (eg, using force to remove the

�m. and in some cases,

basis of fluidity and viscosity, wettability, elastic

surface with a film of water: the smaller the angle of

impression from undercuts) will prevent the materi­

memory, thixotropy, dimensional stability, tear

contact, the better the material will adapt to the sur­

al from returning to its original shape and condition.

To prevent the transmission of infection, impres­

strength, hydrophilic behavior, thermal expansion,

ace to be impressed (Fig 9-29). The balance between

The ADA sets 2.5% as the limit of acceptability for

cohesion and adhesion is an impotant factor i n

permanent deformation'4 (Fig 9-31).

duce features as small as

2

even under 1 �m.•s sions must be disinfected using a treatment that

and application range.

.

.

determining a material's wettability. For example,

2

3

CHAP1' I Custom I mpression Trays and Impression Materials

a

b

c

� Deformation 2.5%

c 9-3 1

Figs 9-25 and 9-26 Comparison of a tooth preparation and its cast developed from an accurate impression. Clinicians are generally convinced that

an impression is a perfect copy of the prepared tooth. The impression material reproduces tooth preparations as accurately as possible, and stone or epoxy resin casts have many clinical characteristics of the originaL However. it is impossible to obtain two identical impressions of the same tooth. Fig 9-27 Polyether impression of a groove photographed at 50 x magnification. Fig 9-28 Impression of a preparation involving a gold inlay at 24 < . The external and internal bevels demonstrate the precision of detail reproduction of the impression materials. Fig g_2g Different angles of wettability for three polyethers with different viscosities, /let to righ) low. medium, and high. Fig 9-30 Silver-plated master

die showing a divergence between the buccal and palatal walls (total occlusal convergence (TOC] angle) that resulted from an error during preparation. Given the shape of the preparation. the restoration will be distorted because the elastic limit has been exceeded. Furthermore. because the anatomic shape of the canine has not been Ia ken 1nlo consideration in the design of this preparation. the dental technician wilt be unable to create a restoration that simulates the natural canine shape. Fig 9-31 Illustration of the 2.5% deformation accepted by the ADA. After intense stress lie. removal from the oral cavity). the impression material has difficulty returning to its original shape.

CHAP1' I Custom I mpression Trays and Impression Materials

a

b

c

� Deformation 2.5%

c 9-3 1

Figs 9-25 and 9-26 Comparison of a tooth preparation and its cast developed from an accurate impression. Clinicians are generally convinced that

an impression is a perfect copy of the prepared tooth. The impression material reproduces tooth preparations as accurately as possible, and stone or epoxy resin casts have many clinical characteristics of the originaL However. it is impossible to obtain two identical impressions of the same tooth. Fig 9-27 Polyether impression of a groove photographed at 50 x magnification. Fig 9-28 Impression of a preparation involving a gold inlay at 24 < . The external and internal bevels demonstrate the precision of detail reproduction of the impression materials. Fig g_2g Different angles of wettability for three polyethers with different viscosities, /let to righ) low. medium, and high. Fig 9-30 Silver-plated master

die showing a divergence between the buccal and palatal walls (total occlusal convergence (TOC] angle) that resulted from an error during preparation. Given the shape of the preparation. the restoration will be distorted because the elastic limit has been exceeded. Furthermore. because the anatomic shape of the canine has not been Ia ken 1nlo consideration in the design of this preparation. the dental technician wilt be unable to create a restoration that simulates the natural canine shape. Fig 9-31 Illustration of the 2.5% deformation accepted by the ADA. After intense stress lie. removal from the oral cavity). the impression material has difficulty returning to its original shape.

CHAPTER 9 Custom I mpression Trays and Impression Materials

.

. er the lear strength will be. However, flexibility also increases the capacity for a material to permanently

the greater likelihood of undercuts during tooth

for impression preservation, and especially the max­

ment should be avoided because they provide less

deform (Fig 9-32). The material must be flexible

preparation and I he elasticity of the gingival tissue.

imum time limit for pouring an impression. However,

dimensional stability. Immediate investment com­

enough to maintain its shape during removal and

the authors believe it is equally important that the

promises the elastic memory and leads to more fre­

sufficiently viscose to accurately reproduce impres­

clinician avoid pouring the stone impression too

quent internal distortions and deformations of the

sion details.

early. Waiting the necessary time before producing a

stone cast.

stone cast, even a few days, allows the elastic mem­ ory to develop fully.'B

Thixotropy

memory of the impression

Periodontal hemorrhage (which should

never

occur in this stage) also reduces tear strength. Blood compromises the impression material's polymeriza­

An operator can detect a low degree of tear

tion since it fills up the space created for the impres­ sion material. Another aspect that can cause tears is

Stability continues to be an important focus of

strength by using a microscope (see chapter 2) with

research on impression materials'•: studies have

a good depth of field to look for any imperfections

sharp edges, especially of rough preparations (Figs

demonstrated the stability of impression materials

or alterations in the impression (Fig 9-33).

9-47 and 9-48).

in relation to the time elapsed before investing the

Stress from impression removal from undercuts

In clinical terms, tear strength depends mostly on

impression with stoneJ • or with respect to disinfec­

can create a distortion wave in the impression and

the thickness of the material i n the area of the

Thixotropy refers to a material's capacity to become

tion techniques.'J Piwowarczyk et al3' studied six

alter the shape and dimensions of the preparation.

preparation and the finish line, as well as the type

more fluid when subjected to mechanical stimula­

silicones and two polyethers, using in vitro tests

While some undercuts exist naturally in the mouth,

of preparation. According to some authors,8·34 the

tion, such as compression when an impression is

and a steel model. The dimensional stability among

during tooth preparation clinicians must not create

tear strength for impression materials can be classi­

being taken. This property, which is common to

the i mpression materials ranged from 11 to 19 �m

additional undercuts that could afect the precision

fied in the following descending order: polysulfides,

polyethers and few other materials, manifests each

over a complete dental arch, demonstrating high

of the restoration (Figs 9-34 to 9-37). An impression

polyvinyl siloxanes, polyethers, and hydrocolloids.

of a perfect tooth preparation can therefore be com­

time the low-viscosity detail materials placed along

precision. Stability often depends on such condi­

the gingival sulcus are pressed by the high-viscosity

tions as the amount of cross bonding that occurs

promised by the presence of any undercuts in the

support materials during tray positioning. The

during the chemical reaction, loss of volatile com­

dental arch.

mechanical compression of high-viscosity material

ponents (eg, alcohols) or water, and swelling due to

i ncreases the fluidity of low-viscosity material, which

water absorption.

Hydrophilic behavior

Because teeth naturally taper sharply at the

Hydrophilia is a material's capacity to absorb water

cementoenamel junction, the deepest undercuts can

and is attributed to the presence of free hydrogen

in turn flows more easily into thin cracks and areas

oten be found in the area apical to the finish line

bonds in the molecular chains. Hydrophilic materials

of the finish line and around the tooth structure

(Fig 9-38). The horizontal gingival retraction that

will absorb water, even i n the form of atmospheric

provides space for the impression material around

humidity after removal from the mouth. Water

beyond the finish line.

Tear strength Tear strength is a material's capacity to resist dam­

the finish line must be kept to a minimum to avoid

absorption can deform the i mpression and alter the

age (above all, breakage) even in the presence of

complications. The result is a very thin impression in

volume dimensions. The clinician can only take im­

undercuts when the impression is removed from the

the area subjected to highest stress (Figs 9-39 and

pressions with hydrophilic material in a d y environ­

Dimensional stability refers to a material's capacity

mouth.JJ-JS Tear strength is influenced by flexibility

9-40). According to Albers,J6 o.s mm is adequate

ment area that is not subject to high temperatures.

to retain its shape over time and under any humid­

(compression deformation) and viscosity (the con­

horizontal gingival retraction for elastomers in gen­

ity or temperature conditions within a tolerance of

sistency of the impression material); a delicate bal­

0.2% (per ADA requirements).•• Investing the im­

ance between these two properties is required for a

loids, given the properties of the impression materi­

of water, for example, when in contact with a moist

material to manifest maximum tear strength.8

als. A material with a high degree of tear strength

surface, and depends on the presence of tensioac­

D i m ensional stability

pression with stone immediately after it has been

6

preparations are more prone to tearing because of

material. Therefore,

impression materials that require immediate invest­

To exploit the maximum effect of elastic memory, the clinician must be aware of the proper techniques

eral, while 1 mm is required for reversible hydrocol­

Hydrophilic behavior, on the other hand, is a

material's capacity to be unafected by the presence

requires less gingival retraction than a material with

tive substances. Thus. a material with hydrophilic

a low degree of tear strength {Figs 9-41 to 9-46).

behavior can adhere to preparations while the

taken can compensate for the relatively low dimen­

To overcome the stress of being removed from

sional stability of some impression materials or the

undercuts, an impression material must be highly

possibility of water absorption or secretion. How­

flexible. Flexibility determines the amount of force

The placement of the inish line can influence the

ever, as noted earlier, immediate pouring of the

that is required to remove the impression from the

required amount of tear strength. lntracrevicular

stone cast prevents full development of the elastic

mouth: the greater the degree of flexibility, the high- .

impression sets, even if there are traces of moisture . .

CHAPTER 9 Custom I mpression Trays and Impression Materials

.

. er the lear strength will be. However, flexibility also increases the capacity for a material to permanently

the greater likelihood of undercuts during tooth

for impression preservation, and especially the max­

ment should be avoided because they provide less

deform (Fig 9-32). The material must be flexible

preparation and I he elasticity of the gingival tissue.

imum time limit for pouring an impression. However,

dimensional stability. Immediate investment com­

enough to maintain its shape during removal and

the authors believe it is equally important that the

promises the elastic memory and leads to more fre­

sufficiently viscose to accurately reproduce impres­

clinician avoid pouring the stone impression too

quent internal distortions and deformations of the

sion details.

early. Waiting the necessary time before producing a

stone cast.

stone cast, even a few days, allows the elastic mem­ ory to develop fully.'B

Thixotropy

memory of the impression

Periodontal hemorrhage (which should

never

occur in this stage) also reduces tear strength. Blood compromises the impression material's polymeriza­

An operator can detect a low degree of tear

tion since it fills up the space created for the impres­ sion material. Another aspect that can cause tears is

Stability continues to be an important focus of

strength by using a microscope (see chapter 2) with

research on impression materials'•: studies have

a good depth of field to look for any imperfections

sharp edges, especially of rough preparations (Figs

demonstrated the stability of impression materials

or alterations in the impression (Fig 9-33).

9-47 and 9-48).

in relation to the time elapsed before investing the

Stress from impression removal from undercuts

In clinical terms, tear strength depends mostly on

impression with stoneJ • or with respect to disinfec­

can create a distortion wave in the impression and

the thickness of the material i n the area of the

Thixotropy refers to a material's capacity to become

tion techniques.'J Piwowarczyk et al3' studied six

alter the shape and dimensions of the preparation.

preparation and the finish line, as well as the type

more fluid when subjected to mechanical stimula­

silicones and two polyethers, using in vitro tests

While some undercuts exist naturally in the mouth,

of preparation. According to some authors,8·34 the

tion, such as compression when an impression is

and a steel model. The dimensional stability among

during tooth preparation clinicians must not create

tear strength for impression materials can be classi­

being taken. This property, which is common to

the i mpression materials ranged from 11 to 19 �m

additional undercuts that could afect the precision

fied in the following descending order: polysulfides,

polyethers and few other materials, manifests each

over a complete dental arch, demonstrating high

of the restoration (Figs 9-34 to 9-37). An impression

polyvinyl siloxanes, polyethers, and hydrocolloids.

of a perfect tooth preparation can therefore be com­

time the low-viscosity detail materials placed along

precision. Stability often depends on such condi­

the gingival sulcus are pressed by the high-viscosity

tions as the amount of cross bonding that occurs

promised by the presence of any undercuts in the

support materials during tray positioning. The

during the chemical reaction, loss of volatile com­

dental arch.

mechanical compression of high-viscosity material

ponents (eg, alcohols) or water, and swelling due to

i ncreases the fluidity of low-viscosity material, which

water absorption.

Hydrophilic behavior

Because teeth naturally taper sharply at the

Hydrophilia is a material's capacity to absorb water

cementoenamel junction, the deepest undercuts can

and is attributed to the presence of free hydrogen

in turn flows more easily into thin cracks and areas

oten be found in the area apical to the finish line

bonds in the molecular chains. Hydrophilic materials

of the finish line and around the tooth structure

(Fig 9-38). The horizontal gingival retraction that

will absorb water, even i n the form of atmospheric

provides space for the impression material around

humidity after removal from the mouth. Water

beyond the finish line.

Tear strength Tear strength is a material's capacity to resist dam­

the finish line must be kept to a minimum to avoid

absorption can deform the i mpression and alter the

age (above all, breakage) even in the presence of

complications. The result is a very thin impression in

volume dimensions. The clinician can only take im­

undercuts when the impression is removed from the

the area subjected to highest stress (Figs 9-39 and

pressions with hydrophilic material in a d y environ­

Dimensional stability refers to a material's capacity

mouth.JJ-JS Tear strength is influenced by flexibility

9-40). According to Albers,J6 o.s mm is adequate

ment area that is not subject to high temperatures.

to retain its shape over time and under any humid­

(compression deformation) and viscosity (the con­

horizontal gingival retraction for elastomers in gen­

ity or temperature conditions within a tolerance of

sistency of the impression material); a delicate bal­

0.2% (per ADA requirements).•• Investing the im­

ance between these two properties is required for a

loids, given the properties of the impression materi­

of water, for example, when in contact with a moist

material to manifest maximum tear strength.8

als. A material with a high degree of tear strength

surface, and depends on the presence of tensioac­

D i m ensional stability

pression with stone immediately after it has been

6

preparations are more prone to tearing because of

material. Therefore,

impression materials that require immediate invest­

To exploit the maximum effect of elastic memory, the clinician must be aware of the proper techniques

eral, while 1 mm is required for reversible hydrocol­

Hydrophilic behavior, on the other hand, is a

material's capacity to be unafected by the presence

requires less gingival retraction than a material with

tive substances. Thus. a material with hydrophilic

a low degree of tear strength {Figs 9-41 to 9-46).

behavior can adhere to preparations while the

taken can compensate for the relatively low dimen­

To overcome the stress of being removed from

sional stability of some impression materials or the

undercuts, an impression material must be highly

possibility of water absorption or secretion. How­

flexible. Flexibility determines the amount of force

The placement of the inish line can influence the

ever, as noted earlier, immediate pouring of the

that is required to remove the impression from the

required amount of tear strength. lntracrevicular

stone cast prevents full development of the elastic

mouth: the greater the degree of flexibility, the high- .

impression sets, even if there are traces of moisture . .

Fig 9-32 Polyether impression of natural teeth (lmpregum Penta Soft HB and LB. 3M ESPEJ. The tear strength is primarily evident in the interproximal areas. which remain unchanged after removal from lhe mouth. F1g 9-33 lower degree of tear strength i n the buccal aspect of lhe Impression. The impression of the sulcus was damaged dunng removal from lhe oral cavity. The lack of detail of the intact tooth structure apical to the finish line will hamper the technician in interpreting the position and extension of the f1n1sh line. Figs g-4and g -35 Example of poorly executed tooth preparations. An impression has been taken and Invested to create a working cast on which four complete crowns can be made. The most troubling aspect is that the impression was sent to the lab even with serious defects (arrow} m the design and parallelism of the prepared Ieeth lnaccurams 1n lhe impression are manifest in the numerous stnpes caused by the tensile stress placed on the impresSIOn material. Though errors are both conceptual and opera­ Ilona!. the greatest fallacy lies in thinking that a dental technician can produce an accurate restoration from such an ImpresSIOn Figs 9-36 and 9-37 Magnified views of another case, the working cast and clin1cal situation. Note the undercuts caused by incorrect tooth preparation. w1th areas that are clearly inadequate in terms of thickness and finishing. Figs g -38 Clear and deta�led fin1sh line in the interproximal area. Fig g -3g Ev1dence of excessive ging1val retraction. Although this impression 1s correct. 11 is too thick at the cervical margin. Fig g-40 Evidence of minimal gingival deflection. The thin width and height of the intact tooth structure apical to the fmish line is typical of impressions taken using the single-cord lechn1que. A thin impres­ sion in this area can d1stort easily during pouring and preclude the creation of more lhan one casl. Figs 9-41 and g-42 Using a microscope. a dental technician reinforces the outside impression border of the intact tooth structure beyond the finish line with a thin line of inert wax. I n this instance. the thin width and height of the impression beyond the finish line facilitates th1s operation. Once the border has been reinforced. the impression can be used to pour several precision casts.

211

279

Fig 9-32 Polyether impression of natural teeth (lmpregum Penta Soft HB and LB. 3M ESPEJ. The tear strength is primarily evident in the interproximal areas. which remain unchanged after removal from lhe mouth. F1g 9-33 lower degree of tear strength i n the buccal aspect of lhe Impression. The impression of the sulcus was damaged dunng removal from lhe oral cavity. The lack of detail of the intact tooth structure apical to the finish line will hamper the technician in interpreting the position and extension of the f1n1sh line. Figs g-4and g -35 Example of poorly executed tooth preparations. An impression has been taken and Invested to create a working cast on which four complete crowns can be made. The most troubling aspect is that the impression was sent to the lab even with serious defects (arrow} m the design and parallelism of the prepared Ieeth lnaccurams 1n lhe impression are manifest in the numerous stnpes caused by the tensile stress placed on the impresSIOn material. Though errors are both conceptual and opera­ Ilona!. the greatest fallacy lies in thinking that a dental technician can produce an accurate restoration from such an ImpresSIOn Figs 9-36 and 9-37 Magnified views of another case, the working cast and clin1cal situation. Note the undercuts caused by incorrect tooth preparation. w1th areas that are clearly inadequate in terms of thickness and finishing. Figs g -38 Clear and deta�led fin1sh line in the interproximal area. Fig g -3g Ev1dence of excessive ging1val retraction. Although this impression 1s correct. 11 is too thick at the cervical margin. Fig g-40 Evidence of minimal gingival deflection. The thin width and height of the intact tooth structure apical to the fmish line is typical of impressions taken using the single-cord lechn1que. A thin impres­ sion in this area can d1stort easily during pouring and preclude the creation of more lhan one casl. Figs 9-41 and g-42 Using a microscope. a dental technician reinforces the outside impression border of the intact tooth structure beyond the finish line with a thin line of inert wax. I n this instance. the thin width and height of the impression beyond the finish line facilitates th1s operation. Once the border has been reinforced. the impression can be used to pour several precision casts.

211

279

CHAPTER 9 Custom I mpression Trays and Impression Materials

. Thermal expansion

nents, base paste and catalyst, are measured out in a ratio recommended by the manufacturer using var­

The ADA has determined that a coefficient of thermal

ious extrusion systems and placed on a suitable

expansion that is less than 2% is acceptable for

mixing surface. It is impossible for the operator to

impression materials.'• Shifts of 2o°C can affect this

mix the two components so that all of the material

coeficient, so clinicians must consider how and

is activated at the same time and thus i n the same

where impressions are stored. Purk et al37 found

stage of chemical reaction. During the plastic stage,

that at the upper and lower limits of extreme tem­

the material is kneaded or mixed and, because the

peratures (66°C and -to0C) impression materials

chemical chains are still open, the material can be

experiences distortions, while Corso et al38 found no

gently seated in the mouth to take an impression. In

significant dimensional alterations for temperatures

the elastic stage, the chains are closed and the

ranging between 4°C and 40°C.

material is less malleable.

Evaluating a p p lication range

times of the impression materials and keep the two

9-43

9-4 4

The operator must know working and setting stages absolutely separate. An impression must be

Using impression materials with a versatile applica­

taken shortly after mixing the material, because

tion range makes clinical procedures easier, reduces

once the chemical chains close, the i mpression

the number of materials used, and thus optimizes

material cannot correctly adapt and record shape

the material cost and yield (Figs 9-49 to 9-51).

and details of the patient's mouth. If a clinician tries

Evaluation of the application range includes a con­

to take an impression with material already in the

sideration of the characteristics discussed so far and

elastic stage, it tends to return to its original shape

of the compatibility with various i nvestment materi­

after being removed from the mouth.'

als (eg, stone, epoxy resins, polyurethane resins) or techniques (Figs 9-52 to 9-54).

For several years, equipment has been available to mechanically blend impression materials packaged

Each impression material is compatible with cer­

in vacuum-packed cartridges. During extrusion, the

tain i nvestment materials used to pour the master

base paste and catalyst are blended in the proper

cast; for example, hydrocolloids are incompatible

quantities and for the correct amount of time.

with electroplating. Certain materials also are con­

Mechanical mixing offers many conveniences,39 in­

traindicated for intracrevicular preparations. Thus, in

cluding a faster mixing speed, use of less material,

choosing a material, it is important to assess the

less air incorporated into the mixture, exact mixing

range of application in order to limit the amount of

ratios, and the assurance that all of the impression

i nventory kept in storage and simplify the handling

material is in the same stage (Figs 9-55 to 9-57). The

procedures (eg, paste mixing, working times, expira­

disadvantage, according to Keck,4° is that "materials

tion dates) of the impression materials.

mixed automatically have 4% less tear strength than those mixed manually."

M ixing i m pression materials

G

When selecting an impression material, the clini· cian must be aware of all properties and compati­

Manual mixing of impression material has always

bilities. An impression material must ofer a high re­

presented problems for operators. The two compo-

sistance to tearing and deformation, accurate three- ..

Figs g-43 and g-44 Wax reinforcement of the border makes the finish line more prominent on the plaster cast and fac i litates the difficult oper­ ation of trimming the cast. However. during structural evaluation with the ceramic in the bisque-bake stage. the clinician must take an elas­ tomeric impression to establish the correct relationship with the nonretracted gingiva (instead of the reflection typical of the impression stage). Figs g-45 and g-46 To avoid taking another impression. the wax can be removed easily and the relationship with the gingiva reproduced in a new cast. Figs 9-47 and 9-48 Excessive roughness of the tooth preparations. seen at the cervical margin and along the axial walls. can tear the impression by increasing the resistance required to release the impression material from the oral cavity. Both impressions. however. sat­ isfy basic clinical criteria.

11

CHAPTER 9 Custom I mpression Trays and Impression Materials

. Thermal expansion

nents, base paste and catalyst, are measured out in a ratio recommended by the manufacturer using var­

The ADA has determined that a coefficient of thermal

ious extrusion systems and placed on a suitable

expansion that is less than 2% is acceptable for

mixing surface. It is impossible for the operator to

impression materials.'• Shifts of 2o°C can affect this

mix the two components so that all of the material

coeficient, so clinicians must consider how and

is activated at the same time and thus i n the same

where impressions are stored. Purk et al37 found

stage of chemical reaction. During the plastic stage,

that at the upper and lower limits of extreme tem­

the material is kneaded or mixed and, because the

peratures (66°C and -to0C) impression materials

chemical chains are still open, the material can be

experiences distortions, while Corso et al38 found no

gently seated in the mouth to take an impression. In

significant dimensional alterations for temperatures

the elastic stage, the chains are closed and the

ranging between 4°C and 40°C.

material is less malleable.

Evaluating a p p lication range

times of the impression materials and keep the two

9-43

9-4 4

The operator must know working and setting stages absolutely separate. An impression must be

Using impression materials with a versatile applica­

taken shortly after mixing the material, because

tion range makes clinical procedures easier, reduces

once the chemical chains close, the i mpression

the number of materials used, and thus optimizes

material cannot correctly adapt and record shape

the material cost and yield (Figs 9-49 to 9-51).

and details of the patient's mouth. If a clinician tries

Evaluation of the application range includes a con­

to take an impression with material already in the

sideration of the characteristics discussed so far and

elastic stage, it tends to return to its original shape

of the compatibility with various i nvestment materi­

after being removed from the mouth.'

als (eg, stone, epoxy resins, polyurethane resins) or techniques (Figs 9-52 to 9-54).

For several years, equipment has been available to mechanically blend impression materials packaged

Each impression material is compatible with cer­

in vacuum-packed cartridges. During extrusion, the

tain i nvestment materials used to pour the master

base paste and catalyst are blended in the proper

cast; for example, hydrocolloids are incompatible

quantities and for the correct amount of time.

with electroplating. Certain materials also are con­

Mechanical mixing offers many conveniences,39 in­

traindicated for intracrevicular preparations. Thus, in

cluding a faster mixing speed, use of less material,

choosing a material, it is important to assess the

less air incorporated into the mixture, exact mixing

range of application in order to limit the amount of

ratios, and the assurance that all of the impression

i nventory kept in storage and simplify the handling

material is in the same stage (Figs 9-55 to 9-57). The

procedures (eg, paste mixing, working times, expira­

disadvantage, according to Keck,4° is that "materials

tion dates) of the impression materials.

mixed automatically have 4% less tear strength than those mixed manually."

M ixing i m pression materials

G

When selecting an impression material, the clini· cian must be aware of all properties and compati­

Manual mixing of impression material has always

bilities. An impression material must ofer a high re­

presented problems for operators. The two compo-

sistance to tearing and deformation, accurate three- ..

Figs g-43 and g-44 Wax reinforcement of the border makes the finish line more prominent on the plaster cast and fac i litates the difficult oper­ ation of trimming the cast. However. during structural evaluation with the ceramic in the bisque-bake stage. the clinician must take an elas­ tomeric impression to establish the correct relationship with the nonretracted gingiva (instead of the reflection typical of the impression stage). Figs g-45 and g-46 To avoid taking another impression. the wax can be removed easily and the relationship with the gingiva reproduced in a new cast. Figs 9-47 and 9-48 Excessive roughness of the tooth preparations. seen at the cervical margin and along the axial walls. can tear the impression by increasing the resistance required to release the impression material from the oral cavity. Both impressions. however. sat­ isfy basic clinical criteria.

11

I AG 9-56

FIG 9-55

C O R R E C T

B A S E - C A T A L Y S T

M I X I N G

R A T I 0

FIG 9-57

Figs 9-49 o 9-51 Versatile Impression materials can be used to take Impressions of various restorations. including inlays. indirect gold posts and cores. and complete crowns. In the management of a professional dental office. material versatility is a considerable advantage for stor­ age and handling F1gs 9-52 o 9-4 Impression materials must be compatible w1th the other matenals. such as electroplating silver. plaster. and polyurethane or epoxy reSin

2

Fig g.55 Pentamix II unit 13M ESPEI for mixing impression materials.

Fig g-56 Garant dispenser 13M ESPEI.

Fig 9-57 Impression material mixed using the Pentamix II.

23

I AG 9-56

FIG 9-55

C O R R E C T

B A S E - C A T A L Y S T

M I X I N G

R A T I 0

FIG 9-57

Figs 9-49 o 9-51 Versatile Impression materials can be used to take Impressions of various restorations. including inlays. indirect gold posts and cores. and complete crowns. In the management of a professional dental office. material versatility is a considerable advantage for stor­ age and handling F1gs 9-52 o 9-4 Impression materials must be compatible w1th the other matenals. such as electroplating silver. plaster. and polyurethane or epoxy reSin

2

Fig g.55 Pentamix II unit 13M ESPEI for mixing impression materials.

Fig g-56 Garant dispenser 13M ESPEI.

Fig 9-57 Impression material mixed using the Pentamix II.

23

CHAPTER 9 Custom I mpression Trays and I mpression Materials

. dimensional reproduction, and dimensional stability.

Reversible hydrocolloids are neither flexible nor

. on clothing. Pouring of the cast demands scrupulous

The ability to reproduce precise surface details is

viscous, and this lack of elastic memory and

attention because the material's high flexibility lends

necessary for an accurate restoration margin and

thixotropy is associated with fragility at the level of

itself to easy deformation, and the material contin·

Introduced in 1965, polyethers ofer several practical

depends largely on the luidity of the material. When

the gingival sulcus. As a result. the clinician will

ues to react even after removal from the mouth and

advantages, such as high dimensional stability and

an i mpression material has these characteristics, the

have difficulty identifying the cervical limits and will

ongoing reactions that produce alcohols.

likelihood of obtaining a suitable impression increases.

be forced to retract the gingiva more extensively

In the authors' view, polysufides are unsuitable

the cervical margins and no requirement for special

than is generally required with other elastomers.

for fixed and removable restorations because of

apparatus. I n addition, they have a good shelf life

Because they have the lowest tear strength,8 re·

their high rate of distortion, which is well masked by

(2 years) and may be poured up to

versible hydrocolloids are not recommended for

their flexibility. The impressions appear to be accu·

impression taking without any concern, allowing the

intracrevicular preparations, which are often called

rate but actually correspond little to the clinical sit·

impression to set completely for maximum elastic

for in patients who seek high-quality esthetics.

uation they are intended to reproduce.

memory.

Because of the need for immediate pouring, the

Today, polyethers are represented by an assort·

Reversible hydrocolloid materials, which irst appeared

material's elastic memoy, and hence its elastic

on the market in 1925, are made of marine algae

recovery, cannot be exploited. For these reasons,

Condensation silicones

ment of materials with varying degrees of viscosity

(agar). These materials were among the first to be

and especially given the considerable horizontal

used to make precision impressions in prosthodon­ tics, and they remain popular today because of their

TYPES O F I M PRESSION MATERIAL

Reversible hydrocolloi ds

tages related to their chemical composition: They tolerate slight humidity at the gingival sulcus, have

rapid solidification, along with excellent recording of

7

days after

and hardness, so that they are extremely versatile

The first elastomers, condensation silicones were

with a wide range of application in clinical practice.

retraction they require, the authors believe hydro·

introduced in 1955, 10 years before the first poly·

They are composed of a base paste made of poly­

colloids are now obsolete for clinical use.

ethers became available. At the time, they were

ether imine-terminated prepolymer, i nert fillers,

relatively high degree of precision and low cost. Reversible hydrocolloids present unique advan·

Polyethers

Polysulfides Polysulfide materials became available in the 1950s,

widely accepted by dental professionals and contin·

emollients, pigments, and aromatic substances. The

ue to be used frequently in clinical practice. Con·

catalyst is composed of an ester derivative of aro·

densation silicones ofer the advantages of requiring

matic sulphonic acid, inert illers, emollients, and

no custom tray or other special equipment, provid­

pigments. The additives and illers are essentially

a pleasant taste, and do not leave indelible marks.

principally as a precision impression for a complete

ing a good record of the cervical limits because of

inorganic and consist of strongly dispersed silica

In addition, a custom tray is not needed for taking

denture, and later extended to fixed prostheses.

their high tear strength, and exhibiting good elastic

and fossil flour, which are responsible for the mate­

impressions. Besides these rheologic characteristics,

These materials have high tear strengthJ4 , J 5 owing

recovery and a reasonable degree of versatility, as

rials' increased final rigidity, dimensional stability

other advantages of these materials include a low

to their extraordinay, even excessive, flexibility,

well as a relatively low cost.

after removal from the mouth, and thixotropy.

cost per impression, a long shelf life, and the rela­

which produces a highly detailed impression. They

Unfortunately, condensation silicones are hydro·

The d iferent consistencies found among poly·

tive ease of pouring with the investment materials.

provide apparently correct impressions that exhibit

phobic, and their use requires rigorous attention to

ethers, according to the ISO 4823 technical specii·

Reversible hydrocolloids also have some disad­

good detail at the cervical limits, can be treated with

keep the gingival sulcus d y during impression tak·

cations, are shown i n Table 9-1. An analysis of the

vantages, including the need for an expensive piece

electroplating for casting, and have a long shelf life.

ing. Because they have inadequate dimensional sta·

table illustrates that the various consistencies of

of equipment for conditioning the materials (special

Unfortunately, excessive flexibility and insuficient

bility, the cast must be poured within 20 minutes,

polyethers determine their applications. For exam­

water trays for boiling and cooling, and a humidor

hardness result in elevated marginal distortion,

and care must be taken to avoid deformation, which

ple, the high-viscosity polyethers are indicated for

for impression storage), and they pose a risk of

which renders polysulfide impressions unsuitable for

can occur easily.

scalding the patient i f handled improperly. Moreover,

making accurate restorations. Other disadvantages

The demand for these materials remains steady

als reproduce greater detail. Their wide variability and compatibility permit clinicians to use diferent

suppot functions, whereas the low-viscosity materi­

because the materials have the capacity to absorb

include the need to make a custom tray to overcome

today primarily because they are frequently used in

water molecules while the impression is being

the most pronounced undercuts, a high degree of

the putty-wash technique, which involves making a

polyether materials according to the clinical situa·

taken, the cast must be poured immediately (within

sensitivity to heat, and a pronounced hydrophobia

double impression. In the authors' opinion, howev­

tion and its requisites; the clinician can decide

a maximum time of 15 minutes') . Consequently,

that requires a completely dry gingival sulcus for

er, their dimensional instability makes them unsuit·

which material to use without compromising proper

electroplating techniques and epoxy resins cannot

impression taking. Furthermore, polysulfide materials

able for current clinical needs.

clinical procedure.

be used for casting.

have a disagreeable odor and leave indelible stains

�

�

5

CHAPTER 9 Custom I mpression Trays and I mpression Materials

. dimensional reproduction, and dimensional stability.

Reversible hydrocolloids are neither flexible nor

. on clothing. Pouring of the cast demands scrupulous

The ability to reproduce precise surface details is

viscous, and this lack of elastic memory and

attention because the material's high flexibility lends

necessary for an accurate restoration margin and

thixotropy is associated with fragility at the level of

itself to easy deformation, and the material contin·

Introduced in 1965, polyethers ofer several practical

depends largely on the luidity of the material. When

the gingival sulcus. As a result. the clinician will

ues to react even after removal from the mouth and

advantages, such as high dimensional stability and

an i mpression material has these characteristics, the

have difficulty identifying the cervical limits and will

ongoing reactions that produce alcohols.

likelihood of obtaining a suitable impression increases.

be forced to retract the gingiva more extensively

In the authors' view, polysufides are unsuitable

the cervical margins and no requirement for special

than is generally required with other elastomers.

for fixed and removable restorations because of

apparatus. I n addition, they have a good shelf life

Because they have the lowest tear strength,8 re·

their high rate of distortion, which is well masked by

(2 years) and may be poured up to

versible hydrocolloids are not recommended for

their flexibility. The impressions appear to be accu·

impression taking without any concern, allowing the

intracrevicular preparations, which are often called

rate but actually correspond little to the clinical sit·

impression to set completely for maximum elastic

for in patients who seek high-quality esthetics.

uation they are intended to reproduce.

memory.

Because of the need for immediate pouring, the

Today, polyethers are represented by an assort·

Reversible hydrocolloid materials, which irst appeared

material's elastic memoy, and hence its elastic

on the market in 1925, are made of marine algae

recovery, cannot be exploited. For these reasons,

Condensation silicones

ment of materials with varying degrees of viscosity

(agar). These materials were among the first to be

and especially given the considerable horizontal

used to make precision impressions in prosthodon­ tics, and they remain popular today because of their

TYPES O F I M PRESSION MATERIAL

Reversible hydrocolloi ds

tages related to their chemical composition: They tolerate slight humidity at the gingival sulcus, have

rapid solidification, along with excellent recording of

7

days after

and hardness, so that they are extremely versatile

The first elastomers, condensation silicones were

with a wide range of application in clinical practice.

retraction they require, the authors believe hydro·

introduced in 1955, 10 years before the first poly·

They are composed of a base paste made of poly­

colloids are now obsolete for clinical use.

ethers became available. At the time, they were

ether imine-terminated prepolymer, i nert fillers,

relatively high degree of precision and low cost. Reversible hydrocolloids present unique advan·

Polyethers

Polysulfides Polysulfide materials became available in the 1950s,

widely accepted by dental professionals and contin·

emollients, pigments, and aromatic substances. The

ue to be used frequently in clinical practice. Con·

catalyst is composed of an ester derivative of aro·

densation silicones ofer the advantages of requiring

matic sulphonic acid, inert illers, emollients, and

no custom tray or other special equipment, provid­

pigments. The additives and illers are essentially

a pleasant taste, and do not leave indelible marks.

principally as a precision impression for a complete

ing a good record of the cervical limits because of

inorganic and consist of strongly dispersed silica

In addition, a custom tray is not needed for taking

denture, and later extended to fixed prostheses.

their high tear strength, and exhibiting good elastic

and fossil flour, which are responsible for the mate­

impressions. Besides these rheologic characteristics,

These materials have high tear strengthJ4 , J 5 owing

recovery and a reasonable degree of versatility, as

rials' increased final rigidity, dimensional stability

other advantages of these materials include a low

to their extraordinay, even excessive, flexibility,

well as a relatively low cost.

after removal from the mouth, and thixotropy.

cost per impression, a long shelf life, and the rela­

which produces a highly detailed impression. They

Unfortunately, condensation silicones are hydro·

The d iferent consistencies found among poly·

tive ease of pouring with the investment materials.

provide apparently correct impressions that exhibit

phobic, and their use requires rigorous attention to

ethers, according to the ISO 4823 technical specii·

Reversible hydrocolloids also have some disad­

good detail at the cervical limits, can be treated with

keep the gingival sulcus d y during impression tak·

cations, are shown i n Table 9-1. An analysis of the

vantages, including the need for an expensive piece

electroplating for casting, and have a long shelf life.

ing. Because they have inadequate dimensional sta·

table illustrates that the various consistencies of

of equipment for conditioning the materials (special

Unfortunately, excessive flexibility and insuficient

bility, the cast must be poured within 20 minutes,

polyethers determine their applications. For exam­

water trays for boiling and cooling, and a humidor

hardness result in elevated marginal distortion,

and care must be taken to avoid deformation, which

ple, the high-viscosity polyethers are indicated for

for impression storage), and they pose a risk of

which renders polysulfide impressions unsuitable for

can occur easily.

scalding the patient i f handled improperly. Moreover,

making accurate restorations. Other disadvantages

The demand for these materials remains steady

als reproduce greater detail. Their wide variability and compatibility permit clinicians to use diferent

suppot functions, whereas the low-viscosity materi­

because the materials have the capacity to absorb

include the need to make a custom tray to overcome

today primarily because they are frequently used in

water molecules while the impression is being

the most pronounced undercuts, a high degree of

the putty-wash technique, which involves making a

polyether materials according to the clinical situa·

taken, the cast must be poured immediately (within

sensitivity to heat, and a pronounced hydrophobia

double impression. In the authors' opinion, howev­

tion and its requisites; the clinician can decide

a maximum time of 15 minutes') . Consequently,

that requires a completely dry gingival sulcus for

er, their dimensional instability makes them unsuit·

which material to use without compromising proper

electroplating techniques and epoxy resins cannot

impression taking. Furthermore, polysulfide materials

able for current clinical needs.

clinical procedure.

be used for casting.

have a disagreeable odor and leave indelible stains

�

�

5

CHAPTER 9 Custom I mpression Trays and Impression Materials

.

Hardness. measured in shore units, is tested over

and, together with polyethers, are more precise,

time because it increases over time.•• Table 9-2

more stable, and thus by far the most frequently

demonstrates that the characteristics produced by

used material for impression

[

taking in clinical

different components, especially the fillers, can make

prosthodontics. Their primary advantage is versat ili·

a material more suitable for certain functions. For

ty: they can be used with many different techniques,

example, lmpregum Penta has very high rigidity after

including the double impression (putty-wash) tech·

TABLE 9-1 Consistencies of polyeth e rs_____________! __

Material

Consistency (mm)

--

40

Permadyne Light Body

Permadyne Heavy Body

33

lmpregum Penta

33

24 hours and is therefore ideal for taking a precision

nique and the one-step/one-. two-. or three-paste

lmpregum Penta Soft

35

impression for implant-supported prostheses.

techniques. In addition to excellent precision and

l m pregum DuoSot, light body

42

l mpregum DuoSoft, heavy body

32

The advantages that particularly distinguish poly­

recording of marginal details, their other advantages

ethers are wettability. which makes them more com­

include wettability, excellent elasticity, and pleasant

patible with diverse surfaces; thixotropy, which makes

odor and appearance. Polyvinyl siloxanes make it

the materials more nuid and increases their capacity

possible for several casts to be made from the same

to reproduce details; and good hydrophilic behavior,

impression, though only the first one will have the

which allows them to function optimally even in the

quality of a master cast (the subsequent i mpres­

presence of slight humidity in the gingival sulcus.

sions will have lost the detail or the intact tooth

Among the disadvantages are the necessity to

structure beyond the finish line). Moreover, they do

make a custom impression tray, to which polyethers

not require special equipment, are easy to store,

adhere poorly, particularly when a specific adhesive is used incorrectly. High-viscosity polyethers (eg, lm· pregum Penta, Permadyne Heavy Body; 3M ESPE) are

TABLE 9-2 Hardness of polyether over time

Hardness (shore) Material

After 15 min

After

1

h

After 24 h

Permadyne Light Body

33

45

53

Permadyne Heavy Body

allow for electroplating, and are easy to mix into a

46

lmpregum Penta Soft

40

55 47

sa so

paste.

l m pregum Penta

46

55

6!

Among their drawbacks are difficulty in pouring,

quite rigid, especially with respect to removal from

high cost, and considerable hydrophobia, which

the mouth. Thus, to avoid complications such as frac­

requires a completely dry gingival sulcus. Further·

tures of weak teeth or avulsion of teeth with little

more, the operator cannot wear latex gloves while

periodontal support, the undercuts must be careful­

manipulating polyvinyl silxanes because the reticu­

ly filled in with stone paste, provisional cement, or

lar reaction of the chain polymerization Is inhibited

materials with low consistency (eg, Permadyne Light

by latex.•'

.. I M PRESSION TECH N I QU ES

called regular, so that both hardness and viscosity may be obtained from one material.

Body or lmpregum DuoSoft light body; 3M. ESPE).

Polyvinyl siloxanes have been available since

Other negative aspects unrelated to clinical outcome

1975 in various consistencies and with various char­

It is generally believed that various viscosities of

Clinicians distinguish between impression tech­

are cost, indelible staining of clothing, and marked

acteristics, depending on their composition. In their

impression materials correspond to different quali­

niques that involve the use of a single material and

sensitivity to ultraviolet light and excessive heat.

medium-, high-, and very-high-viscosity versions, they

ties and applications. All impression materials are

those that use two or more materials simultaneous­

are used as support materials, while low-viscosity

classified either as a support material or a detail

ly. Among the various impression techniques are

material. Support materials must exhibit elevated

the one-step/one-paste technique, the one-step/two­

hardness (greater than s o shore units) for stability

paste technique, the one-step/three-paste technique,

Polyvinyl siloxanes, also known as addition silicones,

and high viscosity (35 mm or less). Detail materials

and the two-step/two-paste technique.

are among the most recent generation of elastomers

must be highly nuid to reproduce minute details and

Polvinyl siloxanes

polyvinyl siloxanes are used to reproduce details.

..

therefore must have a low viscosity and a hardness value that is not excessive. To meet the varied needs

One-step/one- paste technique

of clinical operators, manufacturers have also intra·

T h e one-step/one-paste technique is t h e easiest and

duced materials with medium characteristics. often

perhaps the most common technique used for fixed ..

17

CHAPTER 9 Custom I mpression Trays and Impression Materials

.

Hardness. measured in shore units, is tested over

and, together with polyethers, are more precise,

time because it increases over time.•• Table 9-2

more stable, and thus by far the most frequently

demonstrates that the characteristics produced by

used material for impression

[

taking in clinical

different components, especially the fillers, can make

prosthodontics. Their primary advantage is versat ili·

a material more suitable for certain functions. For

ty: they can be used with many different techniques,

example, lmpregum Penta has very high rigidity after

including the double impression (putty-wash) tech·

TABLE 9-1 Consistencies of polyeth e rs_____________! __

Material

Consistency (mm)

--

40

Permadyne Light Body

Permadyne Heavy Body

33

lmpregum Penta

33

24 hours and is therefore ideal for taking a precision

nique and the one-step/one-. two-. or three-paste

lmpregum Penta Soft

35

impression for implant-supported prostheses.

techniques. In addition to excellent precision and

l m pregum DuoSot, light body

42

l mpregum DuoSoft, heavy body

32

The advantages that particularly distinguish poly­

recording of marginal details, their other advantages

ethers are wettability. which makes them more com­

include wettability, excellent elasticity, and pleasant

patible with diverse surfaces; thixotropy, which makes

odor and appearance. Polyvinyl siloxanes make it

the materials more nuid and increases their capacity

possible for several casts to be made from the same

to reproduce details; and good hydrophilic behavior,

impression, though only the first one will have the

which allows them to function optimally even in the

quality of a master cast (the subsequent i mpres­

presence of slight humidity in the gingival sulcus.

sions will have lost the detail or the intact tooth

Among the disadvantages are the necessity to

structure beyond the finish line). Moreover, they do

make a custom impression tray, to which polyethers

not require special equipment, are easy to store,

adhere poorly, particularly when a specific adhesive is used incorrectly. High-viscosity polyethers (eg, lm· pregum Penta, Permadyne Heavy Body; 3M ESPE) are

TABLE 9-2 Hardness of polyether over time

Hardness (shore) Material

After 15 min

After

1

h

After 24 h

Permadyne Light Body

33

45

53

Permadyne Heavy Body

allow for electroplating, and are easy to mix into a

46

lmpregum Penta Soft

40

55 47

sa so

paste.

l m pregum Penta

46

55

6!

Among their drawbacks are difficulty in pouring,

quite rigid, especially with respect to removal from

high cost, and considerable hydrophobia, which

the mouth. Thus, to avoid complications such as frac­

requires a completely dry gingival sulcus. Further·

tures of weak teeth or avulsion of teeth with little

more, the operator cannot wear latex gloves while

periodontal support, the undercuts must be careful­

manipulating polyvinyl silxanes because the reticu­

ly filled in with stone paste, provisional cement, or

lar reaction of the chain polymerization Is inhibited

materials with low consistency (eg, Permadyne Light

by latex.•'

.. I M PRESSION TECH N I QU ES

called regular, so that both hardness and viscosity may be obtained from one material.

Body or lmpregum DuoSoft light body; 3M. ESPE).

Polyvinyl siloxanes have been available since

Other negative aspects unrelated to clinical outcome

1975 in various consistencies and with various char­

It is generally believed that various viscosities of

Clinicians distinguish between impression tech­

are cost, indelible staining of clothing, and marked

acteristics, depending on their composition. In their

impression materials correspond to different quali­

niques that involve the use of a single material and

sensitivity to ultraviolet light and excessive heat.

medium-, high-, and very-high-viscosity versions, they

ties and applications. All impression materials are

those that use two or more materials simultaneous­

are used as support materials, while low-viscosity

classified either as a support material or a detail

ly. Among the various impression techniques are

material. Support materials must exhibit elevated

the one-step/one-paste technique, the one-step/two­

hardness (greater than s o shore units) for stability

paste technique, the one-step/three-paste technique,

Polyvinyl siloxanes, also known as addition silicones,

and high viscosity (35 mm or less). Detail materials

and the two-step/two-paste technique.

are among the most recent generation of elastomers

must be highly nuid to reproduce minute details and

Polvinyl siloxanes

polyvinyl siloxanes are used to reproduce details.

..

therefore must have a low viscosity and a hardness value that is not excessive. To meet the varied needs

One-step/one- paste technique

of clinical operators, manufacturers have also intra·

T h e one-step/one-paste technique is t h e easiest and

duced materials with medium characteristics. often

perhaps the most common technique used for fixed ..

17

CHAPTER 9 Custom I mpression Trays and I mpression Materials

. prostheses. Its popularity probably results from its

lure. Low-viscosity materials can be applied in min­

simplicity; it uses a single material with one consis­

imal amounts directly along the finish line. using a

tency at one time (Figs 9·58 to 9-60). Moreover, both

syringe equipped with tips suitable for optimal

functions required to obtain a precision impression

extrusion and adaptation. Manufacturer kits include

(ie. detail and support) are carried out using only

preformed tips with standard-diameter openings (Fig

one material of medium to high consistency (eg, reg­

9·66). but these can be replaced by syringe tips with

ular for a polyvinyl siloxane. soft or hard for a poly­

diferent angles and diameters (Fig 9-67).

ether). Unfortunately, while the support function can

When using the single-cord method of retraction.

be performed just as adequately with a medium- or

which is their preferred method. the authors choose

regular-viscosity material, the same cannot be said

a syringe tip with a very small opening that fits the

for the detail function, which is severely compro­

minimal space available, both horizontally and ver­

mised in the authors' opinion. This technique leads

tically (Fig 9-68). During extrusion, they use adapt·

to difficulty in reproducing adequate detail of the

able tips for reaching the palatal and lingual sur­

finish line preparation without extensive displace­

faces of the teeth. With suitably curved tips, the

ment of soft tissue. and thus the cervical margins

operator can ensure that the impression material

are not always clear and precise.

contacts the critical areas to be reproduced in the

The authors firmly prefer the other techniques

impression. Tips produced by Anthogyr or Centrix

over this one because they allow for the use of

permit the operator to modiy the diameter and

materials of diferent consistencies for each function

angle of curvature without creating undesirable bot­

(detail or support) i n the same plastic phase. The

tlenecks in the extrusion channel. Tips that can be

clinician never allows one of the materials to hard­

adapted to suit the clinical case and the operator's

en before the other (Figs 9-61 to 9·65).

working position allow easy application in areas where access is otherwise difficult (Figs 9-69 and 9-70).

One-step/two- or three-paste tech nique

Variations in the technique should be based on the periodontal biotype and the number of missing teeth. In cases where the periodontal tissue is thin

Impression materials are classified in terms of nuid­

and retraction is thus carefully kept to a minimum,

ity and viscosity, and the latter perform better in

the authors avoid using materials with a high vis­

reproducing detail. The smallest details are general·

cosity in the custom tray, opting instead for a regu-

ly those around the inish line, delineating between

lar polyether material (eg, lmpregum Penta Soft) to

the tooth preparation from the i ntact tooth struc·

reduce the occlusal force at the gingival sulcus, even

Figs 9-58 and 9-59 One-step/one- paste technique. The technique uses a medium- or high-viscosity material placed in an impression tray. When using a high-viscosity material. the only way to obtain a good impression of the intact tooth structure beyond the finish line is to perform an extensive horizontal retraction of the gingiva. which is not recommended. Fig g -60 Good clinical result using a medium-viscosity material. which requires less horizontal retraction of the gingiva. Fig g-61 One-step/two-paste impression technique. The clinician uses high- and low-viscosity polyethers. simultaneously. by applying the first (light body. low viscosity! in the sulcus and the second (heavy body. high viscosity) in the tray. in the same plastic state. Figs 9-62 o 9-4 One-step/two-paste impressions. illustrating the parameters for a precision impression.

Fig 9-65 Polyvinyl siloxane impression (President. Coltine/Whaledentl using the one-step/two-paste technique.

�

CHAPTER 9 Custom I mpression Trays and I mpression Materials

. prostheses. Its popularity probably results from its

lure. Low-viscosity materials can be applied in min­

simplicity; it uses a single material with one consis­

imal amounts directly along the finish line. using a

tency at one time (Figs 9·58 to 9-60). Moreover, both

syringe equipped with tips suitable for optimal

functions required to obtain a precision impression

extrusion and adaptation. Manufacturer kits include

(ie. detail and support) are carried out using only

preformed tips with standard-diameter openings (Fig

one material of medium to high consistency (eg, reg­

9·66). but these can be replaced by syringe tips with

ular for a polyvinyl siloxane. soft or hard for a poly­

diferent angles and diameters (Fig 9-67).

ether). Unfortunately, while the support function can

When using the single-cord method of retraction.

be performed just as adequately with a medium- or

which is their preferred method. the authors choose

regular-viscosity material, the same cannot be said

a syringe tip with a very small opening that fits the

for the detail function, which is severely compro­

minimal space available, both horizontally and ver­

mised in the authors' opinion. This technique leads

tically (Fig 9-68). During extrusion, they use adapt·

to difficulty in reproducing adequate detail of the

able tips for reaching the palatal and lingual sur­

finish line preparation without extensive displace­

faces of the teeth. With suitably curved tips, the

ment of soft tissue. and thus the cervical margins

operator can ensure that the impression material

are not always clear and precise.

contacts the critical areas to be reproduced in the

The authors firmly prefer the other techniques

impression. Tips produced by Anthogyr or Centrix

over this one because they allow for the use of

permit the operator to modiy the diameter and

materials of diferent consistencies for each function

angle of curvature without creating undesirable bot­

(detail or support) i n the same plastic phase. The

tlenecks in the extrusion channel. Tips that can be

clinician never allows one of the materials to hard­

adapted to suit the clinical case and the operator's

en before the other (Figs 9-61 to 9·65).

working position allow easy application in areas where access is otherwise difficult (Figs 9-69 and 9-70).

One-step/two- or three-paste tech nique

Variations in the technique should be based on the periodontal biotype and the number of missing teeth. In cases where the periodontal tissue is thin

Impression materials are classified in terms of nuid­

and retraction is thus carefully kept to a minimum,

ity and viscosity, and the latter perform better in

the authors avoid using materials with a high vis­

reproducing detail. The smallest details are general·

cosity in the custom tray, opting instead for a regu-

ly those around the inish line, delineating between

lar polyether material (eg, lmpregum Penta Soft) to

the tooth preparation from the i ntact tooth struc·

reduce the occlusal force at the gingival sulcus, even

Figs 9-58 and 9-59 One-step/one- paste technique. The technique uses a medium- or high-viscosity material placed in an impression tray. When using a high-viscosity material. the only way to obtain a good impression of the intact tooth structure beyond the finish line is to perform an extensive horizontal retraction of the gingiva. which is not recommended. Fig g -60 Good clinical result using a medium-viscosity material. which requires less horizontal retraction of the gingiva. Fig g-61 One-step/two-paste impression technique. The clinician uses high- and low-viscosity polyethers. simultaneously. by applying the first (light body. low viscosity! in the sulcus and the second (heavy body. high viscosity) in the tray. in the same plastic state. Figs 9-62 o 9-4 One-step/two-paste impressions. illustrating the parameters for a precision impression.

Fig 9-65 Polyvinyl siloxane impression (President. Coltine/Whaledentl using the one-step/two-paste technique.

�

CHAPTER 9 Custom I mpression Trays and Impression Materials

FIG 9-66

C O R R E C T

FIG 9-69

FIG 9-67

R E L AT I O N

D I M E N S I O N S

A N D

A M O N G

H O R I Z O NTA L

T H E

FIG 9-70

T I P ' S

D E F L E C T I O N Fig g-66 Syringe and tip used to extrude low- and medium-viscosity materials. Fig g-67 Comparison of lip included with the Pentamix I I unit (top) and Anthogyr tip (bottom). The smaller-diameter opening of the Anthogyr tip corresponds more readily to the space of the sulcus. Figs g-68 and g_6g Different tips can be used. and the shape of the opening can be altered. Fig g-70 Tip curves also can be customized by the operator to facilitate access i n operating areas.

FIG 9-68

HI

CHAPTER 9 Custom I mpression Trays and Impression Materials

FIG 9-66

C O R R E C T

FIG 9-69

FIG 9-67

R E L AT I O N

D I M E N S I O N S

A N D

A M O N G

H O R I Z O NTA L

T H E

FIG 9-70

T I P ' S

D E F L E C T I O N Fig g-66 Syringe and tip used to extrude low- and medium-viscosity materials. Fig g-67 Comparison of lip included with the Pentamix I I unit (top) and Anthogyr tip (bottom). The smaller-diameter opening of the Anthogyr tip corresponds more readily to the space of the sulcus. Figs g-68 and g_6g Different tips can be used. and the shape of the opening can be altered. Fig g-70 Tip curves also can be customized by the operator to facilitate access i n operating areas.

FIG 9-68

HI

CHAPTER 9 Custom Impression Trays and Impression Materials

. in the presence of several teeth and extensive pros­ theses (Fig 9-71).

.

material used'-that is, sections of thicker material contract more than sections with thinner material.

thickness is suitable for the detail reproduction of a light-bodied material. Nissan et al46 conducted a

I n complex treatments involving numerous eden­

Phillips3 underscores the necessity of using less

precision impression, free of distortion from con·

study using 45 impressions made from a steel cast

tulous areas, the authors use a high-viscosity mate·

material by advocating the putty-wash technique,

traction. However, impressions made with this tech­

and roughening the putty for thicknesses of

rial (lmpregum Penta) as a support material along

which i nvolves taking an i mpression in two stages,

nique, while very accurate in reproducing detail, are

and 3 mm. Their findings indicate that a thickness

with a low-viscosity material (Permadyne Light Body)

separately applying two materials of different vis­

often distorted (Fig 9-78).

in a syringe (Figs 9-72 and 9-73). However, if a thin

cosity.4J .44

When studied through in vitro tests under con­

t,

2,

of 3 mm is to be avoided because the resulting plas­ ter casts differed significantly from the original.

The principle of contraction gave rise to methods

trolled conditions and on steel casts or casts de·

However, the ideal thickness of 2 m m or less poses

use the three-paste technique, involving the appli­

that use highly viscous putty as a support material.

signed for repeated insertion and removal, the im­

a significant obstacle to correct reinsertion without

cation of a medium-viscosity material over the detail

Once the putty hardens, it works as a support for a

pressions are rated as comparable to or better than

inadvertently touching the putty.

material (lmpregum Penta Soft) using a syringe. This

low-viscosity or light relining material. In this tech­

those obtained with a single-step technique.44-4S

On the interior surface, where only the color of

method reduces the pressure from the high-viscosi­

nique, a preliminary impression is taken of the

Reinsertion, however, is a key problem in this pro­

the light-bodied material should be visible, the ap­

ty material and improves the tear strength of the

entire arch using a putty material with a high degree

cedure because it is difficult to recenter and refit the

pearance of a putty color in several areas indicates

low-viscosity material. In cases where the periodon­

of hardness. After the hardened putty is removed

impression tray perfectly, avoiding contact with the

the impression's contact with a material already in

tal tissues are thick, adequate gingival reflection

from the mouth, the impression is roughened with

hardened putty in order to create a final impression

the elastic, and not plastic, stage. This anomalous

may be accomplished without hesitation, and high­

large laboratory burs or scalpels, then relined with a

whose interior surface is entirely identical in color to

contact with hardened putty, which is thus unable to

viscosity materials can be used for support after fol­

low-viscosity impression material. The roughening

the low-viscosity material (Figs 9-79 to 9-82). Only

adapt to any shape, generates a distortion wave

lowing the application of low-viscosity materials to

stage focuses on the interproximal areas, removing

when the impression is free of direct tooth contact

that originates from a point not necessarily involved

record the sulcus.

the septa and the midline of the teeth. By minimiz­

with the putty is it truly accurate, but all too often

in the prosthetic treatment, resulting in an impres­ sion with serious defects. For this reason, the authors prefer techniques in which the materials are in the

biotype is a consideration as well, the clinician can

ing the space for the low-viscosity materiai,4S the

this technique yields inaccurate and distorted

viscosity material is used to reproduce detail and

clinician reduces the amount of contraction, at least

impressions.

the paste used i n the tray, regardless of viscosity,

in theorya At this point, the clinician reseats the

A clinical technique for avoiding tooth-putty con­

is used for support.

i mpression tray, which has been relined with low­

tact on reinsetion involves roughing out the interi­

viscosity material. The first impression works like a

or as much as possible while ensuring that the

In summary, for all possible combinations low­

Two-step/two-paste technique ( putty wash)

custom tray; it leaves minimal space for the filling material, but is highly precise, and functions to sup­ port the light material as it reproduces details of the

During polymerization and hardening, impression ma­ terials shrink in direct proportion to the quantity of

2

In theory this technique is appealing, and conceptually it provides a method for obtaining a high­

finish line (Figs 9-74 to 9-77).

_

same physical state (plastic), such as the one-step/ two-paste technique.

..

CHAPTER 9 Custom Impression Trays and Impression Materials

. in the presence of several teeth and extensive pros­ theses (Fig 9-71).

.

material used'-that is, sections of thicker material contract more than sections with thinner material.

thickness is suitable for the detail reproduction of a light-bodied material. Nissan et al46 conducted a

I n complex treatments involving numerous eden­

Phillips3 underscores the necessity of using less

precision impression, free of distortion from con·

study using 45 impressions made from a steel cast

tulous areas, the authors use a high-viscosity mate·

material by advocating the putty-wash technique,

traction. However, impressions made with this tech­

and roughening the putty for thicknesses of

rial (lmpregum Penta) as a support material along

which i nvolves taking an i mpression in two stages,

nique, while very accurate in reproducing detail, are

and 3 mm. Their findings indicate that a thickness

with a low-viscosity material (Permadyne Light Body)

separately applying two materials of different vis­

often distorted (Fig 9-78).

in a syringe (Figs 9-72 and 9-73). However, if a thin

cosity.4J .44

When studied through in vitro tests under con­

t,

2,

of 3 mm is to be avoided because the resulting plas­ ter casts differed significantly from the original.

The principle of contraction gave rise to methods

trolled conditions and on steel casts or casts de·

However, the ideal thickness of 2 m m or less poses

use the three-paste technique, involving the appli­

that use highly viscous putty as a support material.

signed for repeated insertion and removal, the im­

a significant obstacle to correct reinsertion without

cation of a medium-viscosity material over the detail

Once the putty hardens, it works as a support for a

pressions are rated as comparable to or better than

inadvertently touching the putty.

material (lmpregum Penta Soft) using a syringe. This

low-viscosity or light relining material. In this tech­

those obtained with a single-step technique.44-4S

On the interior surface, where only the color of

method reduces the pressure from the high-viscosi­

nique, a preliminary impression is taken of the

Reinsertion, however, is a key problem in this pro­

the light-bodied material should be visible, the ap­

ty material and improves the tear strength of the

entire arch using a putty material with a high degree

cedure because it is difficult to recenter and refit the

pearance of a putty color in several areas indicates

low-viscosity material. In cases where the periodon­

of hardness. After the hardened putty is removed

impression tray perfectly, avoiding contact with the

the impression's contact with a material already in

tal tissues are thick, adequate gingival reflection

from the mouth, the impression is roughened with

hardened putty in order to create a final impression

the elastic, and not plastic, stage. This anomalous

may be accomplished without hesitation, and high­

large laboratory burs or scalpels, then relined with a

whose interior surface is entirely identical in color to

contact with hardened putty, which is thus unable to

viscosity materials can be used for support after fol­

low-viscosity impression material. The roughening

the low-viscosity material (Figs 9-79 to 9-82). Only

adapt to any shape, generates a distortion wave

lowing the application of low-viscosity materials to

stage focuses on the interproximal areas, removing

when the impression is free of direct tooth contact

that originates from a point not necessarily involved

record the sulcus.

the septa and the midline of the teeth. By minimiz­

with the putty is it truly accurate, but all too often

in the prosthetic treatment, resulting in an impres­ sion with serious defects. For this reason, the authors prefer techniques in which the materials are in the

biotype is a consideration as well, the clinician can

ing the space for the low-viscosity materiai,4S the

this technique yields inaccurate and distorted

viscosity material is used to reproduce detail and

clinician reduces the amount of contraction, at least

impressions.

the paste used i n the tray, regardless of viscosity,

in theorya At this point, the clinician reseats the

A clinical technique for avoiding tooth-putty con­

is used for support.

i mpression tray, which has been relined with low­

tact on reinsetion involves roughing out the interi­

viscosity material. The first impression works like a

or as much as possible while ensuring that the

In summary, for all possible combinations low­

Two-step/two-paste technique ( putty wash)

custom tray; it leaves minimal space for the filling material, but is highly precise, and functions to sup­ port the light material as it reproduces details of the

During polymerization and hardening, impression ma­ terials shrink in direct proportion to the quantity of

2

In theory this technique is appealing, and conceptually it provides a method for obtaining a high­

finish line (Figs 9-74 to 9-77).

_

same physical state (plastic), such as the one-step/ two-paste technique.

..

9-BO

9-8 2

Fig g-71 1mpression o_f a maxilla 'y restoration using medium-viscosity polyether support material and low-viscosity polyether detail materi­ . al. The thon ompressoon of the on tact tooth structure beyond the finish line is a common feature of thin periodontal biotypes. Figs g -12 and 9-73 1mpression made with a medium-viscosity support material and a low-viscosity detail material for a complex restoration. The finish line is cle � rly visible _aro_und the circumferenc_e of each toot � . Fig 9-7� Irreversible hydrocolloid impression of a healthy dentition. An area of com­ pressoon _ on the oncosal edge of the maxollary central onCISors (due to excessive pressure during insertion and application in the mouth) resulted on contact between the metalloc tray and the oncosal edge. Fig g -75 The impression for this cast appeared accurate to the naked eye. but once it was invested with plaster the incisal defect became evident. Figs 9-76 and 9-77 Comparison of healthy dentition and the working cast developed from the faulty impression. Severe deformation caused by an area of compression occurs when an impression is taken with a rigid support (custom tray or prehardened putty) and contact is erroneously made between the support and the tooth to be restored.

Fig g-78 Impression made using the putty-wash technique. The presence of the yellow putty. which had already hardened at the time of rein­ sertion with the green impression material. clearly indicates areas of compression. Therefore. when two colors are seen. the effect is similar to a metal tray coming into contact with an incisal edge. Distortion is usually masked by the elasticity of the silicone. but it is nevertheless present and can resull in a restoration wilh undesired friction and poor marginal fit. Fig 9-79 Sagittal cross section of a cast impression. Properly centering an impression tray is difficult when the materials are in the same plastic state: it is even more difficult with the thinly _ spread relonong materoal of the putty-wash technoque. Fog 9-80 In reducong the forst putty ompressoon. too much material was removed. lead­ ing to an excess of _low-viscosity reliner. Figs g -81 and g -82 Cross se � tions of two different teeth from the same impression. Medium-intensity g putty compressoon IS evodent on Fog - 8 1 . but severe compressoon IS evodent on the premolar preparatoon of Fig 9-82. A longitudinal cross section permits the evaluation of the common distortions and alterations of the different impression materials and techniques.

9-BO

9-8 2

Fig g-71 1mpression o_f a maxilla 'y restoration using medium-viscosity polyether support material and low-viscosity polyether detail materi­ . al. The thon ompressoon of the on tact tooth structure beyond the finish line is a common feature of thin periodontal biotypes. Figs g -12 and 9-73 1mpression made with a medium-viscosity support material and a low-viscosity detail material for a complex restoration. The finish line is cle � rly visible _aro_und the circumferenc_e of each toot � . Fig 9-7� Irreversible hydrocolloid impression of a healthy dentition. An area of com­ pressoon _ on the oncosal edge of the maxollary central onCISors (due to excessive pressure during insertion and application in the mouth) resulted on contact between the metalloc tray and the oncosal edge. Fig g -75 The impression for this cast appeared accurate to the naked eye. but once it was invested with plaster the incisal defect became evident. Figs 9-76 and 9-77 Comparison of healthy dentition and the working cast developed from the faulty impression. Severe deformation caused by an area of compression occurs when an impression is taken with a rigid support (custom tray or prehardened putty) and contact is erroneously made between the support and the tooth to be restored.

Fig g-78 Impression made using the putty-wash technique. The presence of the yellow putty. which had already hardened at the time of rein­ sertion with the green impression material. clearly indicates areas of compression. Therefore. when two colors are seen. the effect is similar to a metal tray coming into contact with an incisal edge. Distortion is usually masked by the elasticity of the silicone. but it is nevertheless present and can resull in a restoration wilh undesired friction and poor marginal fit. Fig 9-79 Sagittal cross section of a cast impression. Properly centering an impression tray is difficult when the materials are in the same plastic state: it is even more difficult with the thinly _ spread relonong materoal of the putty-wash technoque. Fog 9-80 In reducong the forst putty ompressoon. too much material was removed. lead­ ing to an excess of _low-viscosity reliner. Figs g -81 and g -82 Cross se � tions of two different teeth from the same impression. Medium-intensity g putty compressoon IS evodent on Fog - 8 1 . but severe compressoon IS evodent on the premolar preparatoon of Fig 9-82. A longitudinal cross section permits the evaluation of the common distortions and alterations of the different impression materials and techniques.

CHAPTER 9 Custom Impression Trays and Impression Materials

CAUSES

I rregular material in the fin ish line area

Failures that occur while taking an impression are

•

. FAI LU R ES A N D T H E I R P R I N C I PAL

B ETTER R E S U LTS U S I N G MATE R I A L S I N SA M E P H YS I CA L STATE

Lack of polymerization resulting from the pres­

caused by factors related to human error-either

ence of blood or incompatible hemostatic or

aulty operational decision making or inadequate eval­

astringent substances (Fig 9-90)

uation of objectives. In addition, complications unan­ ticipated by tests performed under in vitro conditions may arise in clinical situations that are far from ideal.

Rough or powdery plaster cast •

Rough and irregular i m pression surface •

Incomplete polymerization resulting from premature removal from the mouth, incorrect ratios or incorrect mixing of the components, or the presence of oily

• •

Excess tensioactive substance let on the impression

•

Incorrect manipulation of the plaster

•

Rapid polymerization resulting from excessive

Distortion •

•

Catalyst-base ratio too high for condensation sil­ icones

•

of the tray after adhesive application, or use of

ing substances not daubed with alcohol or from

an unsuitable adhesive

non polymerization of the resin composite due to

•

Air bubbles Excessively rapid polymerization impeding the

• •

•

Incorrect filling of the tray (Figs 9-83 and 9-84)

•

fi

Excessive or insuficient space created for the low­ Continuous pressure on an impression material

•

Movement of the tray during the polymerization stage

I rregular-shaped holes •

Use of excessive amount of material

that has already developed elastic properties

mixing process •

Elastic properties of the impression material devel­ oped before insertion of the tray'

viscosity material during the putty-wash technique

low of the material Incorporation of air in the mechanical or manual

Loss of mechanical retention for the materials un­ afected by the adhesive

•

•

Poor adhesion of the elastomer to the tray caused by an insufficient adhesive layer, premature filling

Surface interference from polyethers with bond­

lack of oxygen

•

Resin impression tray inadequately hardened and still subject to polymerization contraction

humidity or high temperatures •

Premature investment of the i mpression before

During mechanical mixing, the two components (base paste and catalyst) were not added simul­ taneously

•

Premature removal of the cast

the minimum time elapsed

substances or organic material on the teeth •

Inadequate cleaning of the impression Excess water left on the surface of the impression

Moisture or detritus on the surface of the teeth

•

Delay in casting from polysulfide or condensation

•

Premature removal from the mouth or removal

Fig 9-83 Small air bubble near the cervical margin. Air bubbles cannot always be prevented. but because it is outside of tho restoration area. this one will not influence the subsequent procedures or compromise the impression. Fig 9-4 Small bubble on the surface of the tooth due to a tooth preparation defect. When the cast is poured. the tooth preparation will have an air bubble. which tho technician can eliminate easily without jeopardizing the restoration.

silicone impressions

Poor adaptation of the material to the surface of

with improper movement (eg, removal from only

the tooth (Figs 9-85 to 9-89)

one side) (Figs 9-91 to 9-93)

. f7

CHAPTER 9 Custom Impression Trays and Impression Materials

CAUSES

I rregular material in the fin ish line area

Failures that occur while taking an impression are

•

. FAI LU R ES A N D T H E I R P R I N C I PAL

B ETTER R E S U LTS U S I N G MATE R I A L S I N SA M E P H YS I CA L STATE

Lack of polymerization resulting from the pres­

caused by factors related to human error-either

ence of blood or incompatible hemostatic or

aulty operational decision making or inadequate eval­

astringent substances (Fig 9-90)

uation of objectives. In addition, complications unan­ ticipated by tests performed under in vitro conditions may arise in clinical situations that are far from ideal.

Rough or powdery plaster cast •

Rough and irregular i m pression surface •

Incomplete polymerization resulting from premature removal from the mouth, incorrect ratios or incorrect mixing of the components, or the presence of oily

• •

Excess tensioactive substance let on the impression

•

Incorrect manipulation of the plaster

•

Rapid polymerization resulting from excessive

Distortion •

•

Catalyst-base ratio too high for condensation sil­ icones

•

of the tray after adhesive application, or use of

ing substances not daubed with alcohol or from

an unsuitable adhesive

non polymerization of the resin composite due to

•

Air bubbles Excessively rapid polymerization impeding the

• •

•

Incorrect filling of the tray (Figs 9-83 and 9-84)

•

fi

Excessive or insuficient space created for the low­ Continuous pressure on an impression material

•

Movement of the tray during the polymerization stage

I rregular-shaped holes •

Use of excessive amount of material

that has already developed elastic properties

mixing process •

Elastic properties of the impression material devel­ oped before insertion of the tray'

viscosity material during the putty-wash technique

low of the material Incorporation of air in the mechanical or manual

Loss of mechanical retention for the materials un­ afected by the adhesive

•

•

Poor adhesion of the elastomer to the tray caused by an insufficient adhesive layer, premature filling

Surface interference from polyethers with bond­

lack of oxygen

•

Resin impression tray inadequately hardened and still subject to polymerization contraction

humidity or high temperatures •

Premature investment of the i mpression before

During mechanical mixing, the two components (base paste and catalyst) were not added simul­ taneously

•

Premature removal of the cast

the minimum time elapsed

substances or organic material on the teeth •

Inadequate cleaning of the impression Excess water left on the surface of the impression

Moisture or detritus on the surface of the teeth

•

Delay in casting from polysulfide or condensation

•

Premature removal from the mouth or removal

Fig 9-83 Small air bubble near the cervical margin. Air bubbles cannot always be prevented. but because it is outside of tho restoration area. this one will not influence the subsequent procedures or compromise the impression. Fig 9-4 Small bubble on the surface of the tooth due to a tooth preparation defect. When the cast is poured. the tooth preparation will have an air bubble. which tho technician can eliminate easily without jeopardizing the restoration.

silicone impressions

Poor adaptation of the material to the surface of

with improper movement (eg, removal from only

the tooth (Figs 9-85 to 9-89)

one side) (Figs 9-91 to 9-93)

. f7

FIG 9-90

FIG 9·91

D I STORT I O N : T H E P R I N C I PAL E N E M Y O F T H E P R O S T H E S I S FIG 9-85

FIG 9-86

FIG 9-87

FIG 9-92

FIG 9-88

FIG 9-89

FIG 9-93

Fig g .as Defect involving the finish line. While the defects in the two preVIous examples d1d not hinder further work. this impression must be retaken. The impression should be exammed under a microscope to avo1d sending the laboratory Impressions that cannot be used and requiring an additional appointment with the patient to take impressions. Figs 9-86 to 9-89 Two different impressions of the same teeth. both cast in epoxy res1n. Figs 9-86 and g.a7 The cervical limits and detail of the finish line are correct. but the impression has not adapted properly on the buccal aspect. The cast from this impression highlights the area of distortion. Figs g .aa and g .ag A second impression was retaken during the same appointment because the defect was noticed immediately. The clinician may have difficulty knowing the degree of imperfection 1n an impression. F1g g. go Occasionally. a portion of retrac­ tion cord can become trapped in the impression. Magnification should be used to check whether the cord would compromise a cast of the intact tooth structure apical to the finish tine. In this case. the cord does not alter the situation significantly. so the impression can be sent to the laboratory as is. and the cord will be removed only after casting. F1gs g .g 1 and g . gz Polyvinyl s1loxane impression with stretched areas and bubbles at the prepara­ tion margin. The cast shows serious defects i n both the tooth preparation and the impression: work cannot be continued. Fig 9-93 Cross section of a cast impression and impression tray to evaluate the spacing and the centenng of the custom tray Impression Because the tray was badly centered in the patient's mouth and came into contact with the shoulder of a tooth. It would have beon clinically useless

FIG 9-90

FIG 9·91

D I STORT I O N : T H E P R I N C I PAL E N E M Y O F T H E P R O S T H E S I S FIG 9-85

FIG 9-86

FIG 9-87

FIG 9-92

FIG 9-88

FIG 9-89

FIG 9-93

Fig g .as Defect involving the finish line. While the defects in the two preVIous examples d1d not hinder further work. this impression must be retaken. The impression should be exammed under a microscope to avo1d sending the laboratory Impressions that cannot be used and requiring an additional appointment with the patient to take impressions. Figs 9-86 to 9-89 Two different impressions of the same teeth. both cast in epoxy res1n. Figs 9-86 and g.a7 The cervical limits and detail of the finish line are correct. but the impression has not adapted properly on the buccal aspect. The cast from this impression highlights the area of distortion. Figs g .aa and g .ag A second impression was retaken during the same appointment because the defect was noticed immediately. The clinician may have difficulty knowing the degree of imperfection 1n an impression. F1g g. go Occasionally. a portion of retrac­ tion cord can become trapped in the impression. Magnification should be used to check whether the cord would compromise a cast of the intact tooth structure apical to the finish tine. In this case. the cord does not alter the situation significantly. so the impression can be sent to the laboratory as is. and the cord will be removed only after casting. F1gs g .g 1 and g . gz Polyvinyl s1loxane impression with stretched areas and bubbles at the prepara­ tion margin. The cast shows serious defects i n both the tooth preparation and the impression: work cannot be continued. Fig 9-93 Cross section of a cast impression and impression tray to evaluate the spacing and the centenng of the custom tray Impression Because the tray was badly centered in the patient's mouth and came into contact with the shoulder of a tooth. It would have beon clinically useless

CHAPTER 9 Custom I mpression Trays and Impression Materials

�

�

and finish the prosthetic work on the master cast,

ments are screwed on the implant, the screw holes

preferably in a single-casting monoblock.

are protected with moist cotton swabs to prevent

I M PRESS I O N S FOR I M PLANT­

and even plaster) and requires many techniques (eg,

S U P P O RTED RESTORAT I O N S

various ways of splinting). The literature is replete with in vitro studies that underscore the inadequate

Otherwise, the clinician must take an initial im­

the plaster from closing up the holes. and the tray

Impression materials are t h e only solution for gath·

results obtained using medium- and high-viscosity

pression using the conventional pickup technique

is filled with extra-hard, q uick-drying plaster (Snow

ering necessary clinical information to construct

elastomers, 59 and others where the gap left after

functional and esthetic restorations.

and then seat the abutments on the implants in par­

White, Kerr Hawe) using a syringe with a cut tip. The

taking an impression with polyethers averages 190

allel in the laboratory, using a bur and a parallel­

plaster is allowed to harden completely, and care is

ometer.

The advent of implant dentistry and the develop­

�m 6o The lack of consistent results creates error

ment of prosthetic implant techniques. which in­

and false expectations for the clinical operator;

volve the study and analysis of the passive fit, have

there is no doubt that an elastomer impression of

called into question the validity and accuracy of

several i mplants, i f executed in the traditional man­

i mpression materials. Giordano underscored the

ner, will not yield reliable results.

taken to remove the excess material onto the sur­ face of the small mold, onto which an adhesive suit­

Modular custom i m p ression tray When taking an impression of mixed dentition,

able for elastomers will be applied (Fig 9-100).

After the most apical area of the first tray is filled with an elastomer extruded through a syringe, the

limitations of impression materials in stating that

Suppoted by findings in the literature,6• the

including natural teeth and implants, a modular

second tray is illed with the impression material

implant-supported restorations require extreme

authors are convinced that the only way to avoid

impression tray, composed of a small open mold on

and centered precisely over the tray holding the

accuracy; small impressions are acceptable for fixed

error during transfer of the implant position is to

the top that serves to support the plaster, can be

hardened plaster. When the elastomer has hard­

prostheses because of the movement permitted by

use plaster as an impression material or to splint

used. The custom tray holds the small mold and is

ened, the blocking screws anchoring the transfer

the periodontal ligament, but this luxury does not

the elements being transferred.6' Plaster is the

cut away to permit the unscrewing of the transfer

copings are removed, and the entire system is

exist when using implants.•'

impression material of choice for achieving an exact

copings. This custom tray (with a cutaway area for

extracted from the mouth, thus making a precision

The techniques of impression taking for an

reproduction of the implant position, and in the case

the implants) fits the entire arch and is used to take

impression that includes both the position of the

implant-supported restoration have changed over

of edentulous patients, who must undergo a full­

an impression of the residual teeth in elastomeric

time. Methods of implant positioning in the labora·

mouth rehabilitation with implants, this can be

material.

tory have evolved from a direct technique, to

accomplished using a plastic impression tray or a

To make a modular custom impression tray, the

The dental technician will then make a single cast

clinician must have a cast that represents the

on the abutments, which will be made to provide a

implants and their relationship to the adjacent teeth

(Fig 9· 101).

removal and subsequent reinsertion of the transfer

custom tray created specifically for the purpose. The

coping, to the latest procedure known as the pick­

dental technician will destroy the tray to remove the

implant site, indicated by the healing abutments or

passive fit with the implants directly in the lab.

up technique.•;' These techniques use traditional

plaster impression and pour a cast using other den·

a diagnostic cast. The implant site is delimited with

Therefore, no paste is needed to detect tension or

impression materials (generally elastomers) with

tal stone that is properly isolated with a layer of

a block of sot wax or by a small mold of the same

distortion directly i n the mouth.

custom trays that are cut out where the implant

insulating material.

resin, so that it occupies the part that will later be

The accuracy of this i mpression technique is illus­ trated clinically in a case of multiple implants i n the

emerges, allowing the removal of the anchor screw

The clinical procedure becomes more complicat-

filled with plaster. The example shows a clinical case

before the hardened impression material is removed

ed when implants are present in a mixed dentition,

in which the analogue (ie, a cast produced from an

posterior dentition. In a 63·year-old female patient,

from the oral cavity (Fig 9-94). Scientific studies of

including healthy natural teeth and teeth prepared

impression with the transfer coping using the pick­

two implants were placed in the mandibular left

impression techniques have found that when work­

for a prosthesis. For this reason, the authors have

up technique) is already inserted in the plaster.

quadrant and three in the mandibular right quad­

ing on a single element, the pickup technique with

designed a modular system of custom impression

Around this block, a small, well-adapted mold of

rant. The patient authorized the taking of three

subsequent repositioning in the i mpression for the

trays, which are made directly in the clinician's

self-curing resin (MultiTray) is left open occlusally. It

impressions with custom trays, two modular and

casting is preferable to the cut-away procedure,

office. This system results in a one-step impression

is polymerized in the light-curing unit (Multilight) for

one using the conventional pickup technique. The

though it tends to result in rotational errors.53

made of plaster for the i m plants and of polyether or polyvinyl siloxane for the remaining dentition. I f the

The custom tray is made by applying a sheet of

two plaster-elastomer casts, shaping and casting a

prosthetic fit have demonstrated that definitive

clinician uses parallel implants or implants without

wax, with a thickness calibrated for the elastomer, to

mono block structure in noble metal alloy on the two

passive.

an internal hexagon or connections that impede the

the resin mold, following the procedure already

lateral segments. The framework thus obtained can

Impression taking with implants involves the use of

removal of the transfer coping, it is possible to

described for making a custom impression tray (Figs

be fit to the cast to verify the implant position ob­

different materials (eg, high-viscosity elastomers

obtain their exact position i n a single impression ..

Over the years, in vitro and survey studiess•-ss of restorations

are

neither precise

nor

5 minutes (Figs 9-95 and 9-96).

9-97 to 9-99). After the transfer copings or abut-

abutments were prepared di rectly on one of the

tained from the three diferent impressions, two in ..

301

CHAPTER 9 Custom I mpression Trays and Impression Materials

�

�

and finish the prosthetic work on the master cast,

ments are screwed on the implant, the screw holes

preferably in a single-casting monoblock.

are protected with moist cotton swabs to prevent

I M PRESS I O N S FOR I M PLANT­

and even plaster) and requires many techniques (eg,

S U P P O RTED RESTORAT I O N S

various ways of splinting). The literature is replete with in vitro studies that underscore the inadequate

Otherwise, the clinician must take an initial im­

the plaster from closing up the holes. and the tray

Impression materials are t h e only solution for gath·

results obtained using medium- and high-viscosity

pression using the conventional pickup technique

is filled with extra-hard, q uick-drying plaster (Snow

ering necessary clinical information to construct

elastomers, 59 and others where the gap left after

functional and esthetic restorations.

and then seat the abutments on the implants in par­

White, Kerr Hawe) using a syringe with a cut tip. The

taking an impression with polyethers averages 190

allel in the laboratory, using a bur and a parallel­

plaster is allowed to harden completely, and care is

ometer.

The advent of implant dentistry and the develop­

�m 6o The lack of consistent results creates error

ment of prosthetic implant techniques. which in­

and false expectations for the clinical operator;

volve the study and analysis of the passive fit, have

there is no doubt that an elastomer impression of

called into question the validity and accuracy of

several i mplants, i f executed in the traditional man­

i mpression materials. Giordano underscored the

ner, will not yield reliable results.

taken to remove the excess material onto the sur­ face of the small mold, onto which an adhesive suit­

Modular custom i m p ression tray When taking an impression of mixed dentition,

able for elastomers will be applied (Fig 9-100).

After the most apical area of the first tray is filled with an elastomer extruded through a syringe, the

limitations of impression materials in stating that

Suppoted by findings in the literature,6• the

including natural teeth and implants, a modular

second tray is illed with the impression material

implant-supported restorations require extreme

authors are convinced that the only way to avoid

impression tray, composed of a small open mold on

and centered precisely over the tray holding the

accuracy; small impressions are acceptable for fixed

error during transfer of the implant position is to

the top that serves to support the plaster, can be

hardened plaster. When the elastomer has hard­

prostheses because of the movement permitted by

use plaster as an impression material or to splint

used. The custom tray holds the small mold and is

ened, the blocking screws anchoring the transfer

the periodontal ligament, but this luxury does not

the elements being transferred.6' Plaster is the

cut away to permit the unscrewing of the transfer

copings are removed, and the entire system is

exist when using implants.•'

impression material of choice for achieving an exact

copings. This custom tray (with a cutaway area for

extracted from the mouth, thus making a precision

The techniques of impression taking for an

reproduction of the implant position, and in the case

the implants) fits the entire arch and is used to take

impression that includes both the position of the

implant-supported restoration have changed over

of edentulous patients, who must undergo a full­

an impression of the residual teeth in elastomeric

time. Methods of implant positioning in the labora·

mouth rehabilitation with implants, this can be

material.

tory have evolved from a direct technique, to

accomplished using a plastic impression tray or a

To make a modular custom impression tray, the

The dental technician will then make a single cast

clinician must have a cast that represents the

on the abutments, which will be made to provide a

implants and their relationship to the adjacent teeth

(Fig 9· 101).

removal and subsequent reinsertion of the transfer

custom tray created specifically for the purpose. The

coping, to the latest procedure known as the pick­

dental technician will destroy the tray to remove the

implant site, indicated by the healing abutments or

passive fit with the implants directly in the lab.

up technique.•;' These techniques use traditional

plaster impression and pour a cast using other den·

a diagnostic cast. The implant site is delimited with

Therefore, no paste is needed to detect tension or

impression materials (generally elastomers) with

tal stone that is properly isolated with a layer of

a block of sot wax or by a small mold of the same

distortion directly i n the mouth.

custom trays that are cut out where the implant

insulating material.

resin, so that it occupies the part that will later be

The accuracy of this i mpression technique is illus­ trated clinically in a case of multiple implants i n the

emerges, allowing the removal of the anchor screw

The clinical procedure becomes more complicat-

filled with plaster. The example shows a clinical case

before the hardened impression material is removed

ed when implants are present in a mixed dentition,

in which the analogue (ie, a cast produced from an

posterior dentition. In a 63·year-old female patient,

from the oral cavity (Fig 9-94). Scientific studies of

including healthy natural teeth and teeth prepared

impression with the transfer coping using the pick­

two implants were placed in the mandibular left

impression techniques have found that when work­

for a prosthesis. For this reason, the authors have

up technique) is already inserted in the plaster.

quadrant and three in the mandibular right quad­

ing on a single element, the pickup technique with

designed a modular system of custom impression

Around this block, a small, well-adapted mold of

rant. The patient authorized the taking of three

subsequent repositioning in the i mpression for the

trays, which are made directly in the clinician's

self-curing resin (MultiTray) is left open occlusally. It

impressions with custom trays, two modular and

casting is preferable to the cut-away procedure,

office. This system results in a one-step impression

is polymerized in the light-curing unit (Multilight) for

one using the conventional pickup technique. The

though it tends to result in rotational errors.53

made of plaster for the i m plants and of polyether or polyvinyl siloxane for the remaining dentition. I f the

The custom tray is made by applying a sheet of

two plaster-elastomer casts, shaping and casting a

prosthetic fit have demonstrated that definitive

clinician uses parallel implants or implants without

wax, with a thickness calibrated for the elastomer, to

mono block structure in noble metal alloy on the two

passive.

an internal hexagon or connections that impede the

the resin mold, following the procedure already

lateral segments. The framework thus obtained can

Impression taking with implants involves the use of

removal of the transfer coping, it is possible to

described for making a custom impression tray (Figs

be fit to the cast to verify the implant position ob­

different materials (eg, high-viscosity elastomers

obtain their exact position i n a single impression ..

Over the years, in vitro and survey studiess•-ss of restorations

are

neither precise

nor

5 minutes (Figs 9-95 and 9-96).

9-97 to 9-99). After the transfer copings or abut-

abutments were prepared di rectly on one of the

tained from the three diferent impressions, two in ..

301

CHAPTER 9 Custom Impression Trays and Impression Materials

�

plaster-polyether and one in complete polyether.

ament, which compensates, in part, for a minimal

The abutments are screwed on the analogues on

degree of imperfection and permits the seating of

each of the three casts to check the adaptation of

the fixed dental restorations.

the single cast.

The authors' working philosophy demands that

The key aspect is the repeatability of the mixed

during tooth preparation for a conventional pros­

plaster-€1astomer i mpression: the structures adapt

thesis, the clinician must think not only about seat­

perfectly to the positions on these casts, while those

ing the restoration, but above all of eliminating,

made in all elastomer result in considerable gaps

through close adherence to the recommended pro­

and poor adaptation (igs 9-102 to 9-105). This aspect

cedures, all possible sources of tension on the

further recommends the use of plaster for implant

i mpression materials (Figs 9-106 to 9-108). During

impressions. The nonrepeatability of elastomeric im­

preparation, the clinician must act in accordance

pressions, true for both implants and natural denti­

with the characteristics of the impression materials,

tion, proves that though these materials have accu­

even before considering the aspects related to the

rate results for in vitro studies, the stress they are

type of prosthesis and the material used for making

subjected to in clinical settings often exceeds the

it. Given the characteristics of the impression mate­

elastic limit of the material. Precise prosthetic restor­

rials available today, this is the means by which the

ations that adapt well to the natural dentition are

clinician may achieve maximum precision (Figs 9-109

closely linked to the presence of the periodontal lig-

to 9-134).

•

Fig 9-94 Pickup technique for making impressions for implant-supported prostheses. This type of impression yields unpre­ dictable results in clinical treatment. Fig 9-95 Fabrication of a modular custom impression tray. There are two modules. one for taking a plaster impression of the implant area and the other for taking an elastomeric impression of the remai ning den­ tition. The plaster module is made by either adapting a strip of curing resin around a block of wax or directly shaping the resin and positioning it around the implant site to contain the plaster. Figs g_g6 and 9-g7 Spacing wax covers the cast and the mold for the plaster. Wax has been removed in areas to make occlusal stops for centering the impression. Figs g -98 and 9-99 Finished modular custom impression tray.

02

3

CHAPTER 9 Custom Impression Trays and Impression Materials

�

plaster-polyether and one in complete polyether.

ament, which compensates, in part, for a minimal

The abutments are screwed on the analogues on

degree of imperfection and permits the seating of

each of the three casts to check the adaptation of

the fixed dental restorations.

the single cast.

The authors' working philosophy demands that

The key aspect is the repeatability of the mixed

during tooth preparation for a conventional pros­

plaster-€1astomer i mpression: the structures adapt

thesis, the clinician must think not only about seat­

perfectly to the positions on these casts, while those

ing the restoration, but above all of eliminating,

made in all elastomer result in considerable gaps

through close adherence to the recommended pro­

and poor adaptation (igs 9-102 to 9-105). This aspect

cedures, all possible sources of tension on the

further recommends the use of plaster for implant

i mpression materials (Figs 9-106 to 9-108). During

impressions. The nonrepeatability of elastomeric im­

preparation, the clinician must act in accordance

pressions, true for both implants and natural denti­

with the characteristics of the impression materials,

tion, proves that though these materials have accu­

even before considering the aspects related to the

rate results for in vitro studies, the stress they are

type of prosthesis and the material used for making

subjected to in clinical settings often exceeds the

it. Given the characteristics of the impression mate­

elastic limit of the material. Precise prosthetic restor­

rials available today, this is the means by which the

ations that adapt well to the natural dentition are

clinician may achieve maximum precision (Figs 9-109

closely linked to the presence of the periodontal lig-

to 9-134).

•

Fig 9-94 Pickup technique for making impressions for implant-supported prostheses. This type of impression yields unpre­ dictable results in clinical treatment. Fig 9-95 Fabrication of a modular custom impression tray. There are two modules. one for taking a plaster impression of the implant area and the other for taking an elastomeric impression of the remai ning den­ tition. The plaster module is made by either adapting a strip of curing resin around a block of wax or directly shaping the resin and positioning it around the implant site to contain the plaster. Figs g_g6 and 9-g7 Spacing wax covers the cast and the mold for the plaster. Wax has been removed in areas to make occlusal stops for centering the impression. Figs g -98 and 9-99 Finished modular custom impression tray.

02

3

CHAPHR 9 Custom Impression Trays a n d Impression Materials

s ,.,J � ,

--

Figs 9-100 and 9-101 In vitro example. The clinician takes a plaster impression (Snow Whitel of the transfer coping screwed onto the implants. After the plaster hardens in the patient"s mouth. excess material is removed. adhesive is applied to the exteri or of the plaster _ both _ conta�ns mold. and elaslomeric material is sealed i n the rest of the dental arch in the custom tray. I n this manner. a s1ngle 1mpress1on modules. as seen in Fig 9 - 1 0 1 . Fig g-102 Three impressions were taken of two areas (the mandibular right and left quadrants! to be restored with implant-supported fixed prostheses. The impressions were taken using three series of transfer copin � s. one 1n onl y elastomenc _ material and the other two in a combination of plaster and elastomer. according to the modular custom impress1on tray technique. Fig 9-103 Fixed partial denture in a single casting. realized using the first cast from the plaster and polyether impression. Fig g -104 Abutments re­ moved and positioned on the cast of the elastomer impression. illustrating the framework"s lack of fit. Fig 9-105 Abutments removed and positioned on the second plaster-elastomer cast. illustrating the correspondence and good fit. The abutments can b e perfectly supenm­ posed on the first plaster-elastomer model. This underscores the clinical repeatability of plaster impressions. l4

Fig g-106 Correct impression yields a distinct and unbroken finish line for the entire perimeter of the tooth. Fig 9-107 Same type of impression details obtained with minimal horizontal retraction. This type of impression ensures the long-term stability of the gingiva. Fig g -108 Adequate impression requiring improved tooth preparation for the primary reduction and the finishing. The impression material must establish more than just the restorations insertion axis. Fig g. Jog Clinical case of a 64-year-old female patient who presented with serious periodontal problems and only five Ieeth in the maxillary arch. The teeth will be restored with a telescopic prosthesis after suitable periodontal treat­ ment.

CHAPHR 9 Custom Impression Trays a n d Impression Materials

s ,.,J � ,

--

Figs 9-100 and 9-101 In vitro example. The clinician takes a plaster impression (Snow Whitel of the transfer coping screwed onto the implants. After the plaster hardens in the patient"s mouth. excess material is removed. adhesive is applied to the exteri or of the plaster _ both _ conta�ns mold. and elaslomeric material is sealed i n the rest of the dental arch in the custom tray. I n this manner. a s1ngle 1mpress1on modules. as seen in Fig 9 - 1 0 1 . Fig g-102 Three impressions were taken of two areas (the mandibular right and left quadrants! to be restored with implant-supported fixed prostheses. The impressions were taken using three series of transfer copin � s. one 1n onl y elastomenc _ material and the other two in a combination of plaster and elastomer. according to the modular custom impress1on tray technique. Fig 9-103 Fixed partial denture in a single casting. realized using the first cast from the plaster and polyether impression. Fig g -104 Abutments re­ moved and positioned on the cast of the elastomer impression. illustrating the framework"s lack of fit. Fig 9-105 Abutments removed and positioned on the second plaster-elastomer cast. illustrating the correspondence and good fit. The abutments can b e perfectly supenm­ posed on the first plaster-elastomer model. This underscores the clinical repeatability of plaster impressions. l4

Fig g-106 Correct impression yields a distinct and unbroken finish line for the entire perimeter of the tooth. Fig 9-107 Same type of impression details obtained with minimal horizontal retraction. This type of impression ensures the long-term stability of the gingiva. Fig g -108 Adequate impression requiring improved tooth preparation for the primary reduction and the finishing. The impression material must establish more than just the restorations insertion axis. Fig g. Jog Clinical case of a 64-year-old female patient who presented with serious periodontal problems and only five Ieeth in the maxillary arch. The teeth will be restored with a telescopic prosthesis after suitable periodontal treat­ ment.

�

Custom I mpression Trays a n d ImpresSIOn Materia

Fig 9-110

Fig 9-1 1 1

ln1t1al stage of treatment. immed�ately follow1ng resectiYe surgery and reconstruction of the missing teeth with fiberglass dowels.

After proper periodontal treatment. the smallest poss1ble retraction cord was posit1oned to vertically retract the gingiva.

Fig 9-112 Finish line repoSitioning and finishing of the tooth preparation Figs 9-113 and g -114 Following the use of oscillating instruments and manual rounded chisels. the tooth preparat1ons are well polished. and the finish line is properly positioned.

01

�

Custom I mpression Trays a n d ImpresSIOn Materia

Fig 9-110

Fig 9-1 1 1

ln1t1al stage of treatment. immed�ately follow1ng resectiYe surgery and reconstruction of the missing teeth with fiberglass dowels.

After proper periodontal treatment. the smallest poss1ble retraction cord was posit1oned to vertically retract the gingiva.

Fig 9-112 Finish line repoSitioning and finishing of the tooth preparation Figs 9-113 and g -114 Following the use of oscillating instruments and manual rounded chisels. the tooth preparat1ons are well polished. and the finish line is properly positioned.

01

CHAPTER 9 Custom Impression Trays and Impression Materials

Figs g-115 o g-111 Higher magnification shows the finish line position. which will be juxlagingival after repositioning.

Figs g -118 to g-120 Lateral and occlusal views demonstrate the good parallelism of the preparations and the care taken to avoid injury to the gin­ giva. Figs g-121 and g-122 Elastomeric impression. Because the compression area is on the mucosal tissue and not on the teeth. the impression can be used.

CHAPTER 9 Custom Impression Trays and Impression Materials

Figs g-115 o g-111 Higher magnification shows the finish line position. which will be juxlagingival after repositioning.

Figs g -118 to g-120 Lateral and occlusal views demonstrate the good parallelism of the preparations and the care taken to avoid injury to the gin­ giva. Figs g-121 and g-122 Elastomeric impression. Because the compression area is on the mucosal tissue and not on the teeth. the impression can be used.

CHAPTER 9 Custom I mpression Trays and Impression Materials

Figs g-123 and 9-124 Extra hard plaster cast shows the accurate finish tines of the tooth preparations and welt-reproduced details.

igs 9-125 o g-m Gold castings for double telescopic crowns for the filling i n the palienrs mouth. During the marginal adaptation. the pre­

cision of the framework was evaluated on the cast MagnifiCatiOn ensures that the same adaptation occurs in the mouth.

310

Figs 9-128and 9-129 High-noble gold copings. which witt be cemented directly onto the prepared teeth. Fig 9-130 Secondary structures adapted to the primary copings. The secondary structures witt be cemented inside the prosthetic framework after electroplating. Figs g -131 and 9-132 Definitive restoration. including the metal-reinforced prosthesis and telescopic crowns in a single block. coaled with an esthetic resin composite ISinfony. 3M ESPEI. The esthetic coating uses one of the latest resin composites for a lighter prosthesis. The advan­ tage of this type of restoration is the possibility of easily resolving any complications with one or more teeth. without having to start over from the beginning. 311

CHAPTER 9 Custom I mpression Trays and Impression Materials

Figs g-123 and 9-124 Extra hard plaster cast shows the accurate finish tines of the tooth preparations and welt-reproduced details.

igs 9-125 o g-m Gold castings for double telescopic crowns for the filling i n the palienrs mouth. During the marginal adaptation. the pre­

cision of the framework was evaluated on the cast MagnifiCatiOn ensures that the same adaptation occurs in the mouth.

310

Figs 9-128and 9-129 High-noble gold copings. which witt be cemented directly onto the prepared teeth. Fig 9-130 Secondary structures adapted to the primary copings. The secondary structures witt be cemented inside the prosthetic framework after electroplating. Figs g -131 and 9-132 Definitive restoration. including the metal-reinforced prosthesis and telescopic crowns in a single block. coaled with an esthetic resin composite ISinfony. 3M ESPEI. The esthetic coating uses one of the latest resin composites for a lighter prosthesis. The advan­ tage of this type of restoration is the possibility of easily resolving any complications with one or more teeth. without having to start over from the beginning. 311

CHAPTER 9 Custom I mpression Trays and Impression Materials

R EFERENCES

12.

Eames WB, Wallace SW, Suway NB, Rogers LB. Accuracy and dimensional stability of elastomeric impression

t. Schulz HH, Schwickerath H. Die Abformung in der

Zahnheilkunde. Cologne: Deutscher lrzte-Verlag, 1989. 2.

materials. ) Prosthet Dent 1979;42:159-162. 13.

Richards MW, Zeiaei 5, Bagby MD, Okubo 5, Soltani ). Working times and dimensional accuracy of the one­ step putty/wash impression technique. J Prosthodont

3·

dentures. J Prosthet Dent 1988;59:288-291. 14·

Revised American Dental Association Specification no.

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15. Johnson GH, Lepe X, Aw TC. The efect of surface mois·

4· Carrotte PV, Johnson A, Winstanley RB. The inluence of

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the impression tray on the accuracy of impressions for crown and bridge work-An investigation and review.

16.

Br Dent J 199B;t85:580-585.

for preparation of individual mold trays [in German).

Owen CP, Goolam R. Disinfection of impression materi­ als to prevent viral cross contamination: A review and

5· Wirz ), Scharer P, Kauhnann P. Selected acrylate resins

6.

Lin CC, Ziebert GJ. Donegan 51. Dhuru VB. Accuracy of impression materials for complete-arch ixed partial

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ADA Council on Scientiic Aairs and ADA Council on

Dent Labor 1979;27:573-580.

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Cho GC, Donovan TE, Chee W, White SN. Tensile bond

20. atyas ), Dao N, Caputo A, Lucatoto FM. Eects of

strength of polvinyl siloxane impressions bonded to a

disinfectants on dimensional accuracy of impression

custom tray as a function of dying time: Pat I. J Prosthet Dent 1995:73:419-423.

materials. I Prosthet Dent 1990;64:25-31. 21.

to. Linke BA, Nicholls )1, Faucher RR. Distortion analysis of stone casts made from impression materials. I Prosthet Dent 1985:54:794-802. 11.

Dounis GS, Zieber! G), Dounis KS. A comparison of

Ken M, Rathmer RM, Strub JR. Three-dimensional investigation of the accuracy of impression materials ater disinfection. J Prosthet Dent 1993:70:44-456.

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Davis BA. Powers JM. Efect of immersion disinfection on properties of impression materials. J Prosthodont

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312

m

CHAPTER 9 Custom I mpression Trays and Impression Materials

R EFERENCES

12.

Eames WB, Wallace SW, Suway NB, Rogers LB. Accuracy and dimensional stability of elastomeric impression

t. Schulz HH, Schwickerath H. Die Abformung in der

Zahnheilkunde. Cologne: Deutscher lrzte-Verlag, 1989. 2.

materials. ) Prosthet Dent 1979;42:159-162. 13.

Richards MW, Zeiaei 5, Bagby MD, Okubo 5, Soltani ). Working times and dimensional accuracy of the one­ step putty/wash impression technique. J Prosthodont

3·

dentures. J Prosthet Dent 1988;59:288-291. 14·

Revised American Dental Association Specification no.

1998:7:25-255·

19 for Non-aqueous, Elastomeric Dental Impression Ma­

Phillips RW. Science of Dental Materials, ed 9. Phila­

terials. J Am Dent Assoc 1977:94:733-741.

delphia: Saunders, 1991.

15. Johnson GH, Lepe X, Aw TC. The efect of surface mois·

4· Carrotte PV, Johnson A, Winstanley RB. The inluence of

ture on detail reproduction of elastomeric impressions. I Prosthet Dent 2oo3;90(4) :354-364.

the impression tray on the accuracy of impressions for crown and bridge work-An investigation and review.

16.

Br Dent J 199B;t85:580-585.

for preparation of individual mold trays [in German).

Owen CP, Goolam R. Disinfection of impression materi­ als to prevent viral cross contamination: A review and

5· Wirz ), Scharer P, Kauhnann P. Selected acrylate resins

6.

Lin CC, Ziebert GJ. Donegan 51. Dhuru VB. Accuracy of impression materials for complete-arch ixed partial

a protocol. tnt I Prosthodont 1993;6:48o-494· 17.

ADA Council on Scientiic Aairs and ADA Council on

Dent Labor 1979;27:573-580.

Dental Practice. Inection control recommendations for

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the dental oice and the dental laboratoy. I Am Dent

bridge prosthodontics. The determination of their place and practical tips [in German> Schweiz Monatsschr

Assoc 1996;t27:672�. t8.

Kugel G, Pery RD, Ferrari M, Lalicata P. Disinfection and

Zahnmed 199t;tOt:62>38.

communication practices: A survey of U.S. dental labo­

7.

Ortensi L, Strocchi ML. Modiied custom tray. ) Prosthet

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8.

Craig RG. Restorative Dental Materials, ed to. St Louis:

sional stability of elastomeric impression materials fol­

Mosby, 1997.

lowing disinfection. I Prosthet Dent 1990;63:27-276.

Dent 2000;84:237-240.

9·

19. Langenwalter EM, Aquilino SA, Tuner A. The dimen­

Cho GC, Donovan TE, Chee W, White SN. Tensile bond

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strength of polvinyl siloxane impressions bonded to a

disinfectants on dimensional accuracy of impression

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materials. I Prosthet Dent 1990;64:25-31. 21.

to. Linke BA, Nicholls )1, Faucher RR. Distortion analysis of stone casts made from impression materials. I Prosthet Dent 1985:54:794-802. 11.

Dounis GS, Zieber! G), Dounis KS. A comparison of

Ken M, Rathmer RM, Strub JR. Three-dimensional investigation of the accuracy of impression materials ater disinfection. J Prosthet Dent 1993:70:44-456.

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Davis BA. Powers JM. Efect of immersion disinfection on properties of impression materials. J Prosthodont

impression materials for complete-arch fixed patial dentures. J Prosthet Dent 1991:65:t65-169.

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56. Jemt T, Rubenstein IE, Carlsson L, Lang BR. easuring

sion technique. I Prosthet Dent •992:67: 583-589.

dimensional stability of polyvinyl siloxane and poly·

binations. lnt J Prosthodont 2oo; t):214-22o.

314

ings and welded titanium frameworks. easurements of the precision of the it between completed implant

Morgana SM. The effect of temperature changes on the

268-276.

1996:11:21-222.

Tjan AH, Li . Efects of reheating on the accuracy of

(eds). Applied Dental Materials, ed 8. Oxford: Blackwell

39·

impression techniques. t nt I Oral Maxillofac Implants

addition silicone putty-wash Impressions. I Prosthet

cation and requirements. In: Mccabe JF. Walls AWG

bility, imbibition, and mass change of disinfected low·

single-tooth implants. lnt I Prosthodont 200t:t4:1S2-t58. Ass r f D. Marshak B, Schmidt A. Accuracy of implant

5 5 · Jemt . Three-dimensional distonion of gold alloy cast­

versus two-step putty wash addition silicone impres­

Purk )H, Willes MG, Tira DE, Eick JD, Hung SH. The

sional stability and detail reproduction of irreversible

cCabe )F, Walls AW. Impression materials: Classifi­

45·

Dent 1990:6):282-285.

disinfectant agents on dimensional stability of elasto­

viscosity impression materials. J Prosthet Dent 2002;88:

30.

Tam LE, Brown JW. The tear resistance of various im· pression materials with and without modifiers. J Prosthet

Adabo GL, Zanarottr E. Fonseca RG, Cruz A. Effect of

44.

Daoudi MF, Setchell DJ, Searson LJ. A laboratory investi· gation of the accuracy of two impression techniques for

43· Nissan J. Laufer BZ, Brosh T, ssif D. Accuracy of three

)). Keck SC, Douglas WH. Tear strength of non-aqueous

ical disinfectant solutions on the stability and accuracy 34

53.

54·

Rlos MP, Morgana SM. Stein RS, Rose L. Effeas of chem­

by immersion. J Prosthet Dent 1998:79=44-453· 28.

de Camargo LM, Chee W, Donovan TE. Inhibition of

after long-term disinfection. I Prosthet Dent 1995:74:

mersed in disinfectants. I Prosthet Dent 1996:76:8-14.

27.

42.

polymerization of polyvinyl siloxanes by medicaments

bility of seven elastomeric impression materials lm·

26.

Piwowarczyk A, Ottl P, Buchler A, Lauer HC, Hoffmann A. In vitro study on the dimensional accuracy of selected

of the dental impression complex. I Prosthet Dent 1996:

25.

)2.

a polyether and addition silicone impression materials

so.

51.

material. lnt J Oral axilloac Implants 1999:14 :88s-888. 62.

Wise M. Fit of implant-suppMed fixed prostheses fab­

78:596-6o4.

ricated on master casts made from a dental stone and

Wee AG, Aquilino SA, Schneider RL. Strategies to

a dental plaster. I Prosthet Dent 200t;86:sJ2-5J8.

31. Clancy JM, Scandrett FR, Ettinger RL Long-term dimen­

the time-dependent dimensional stability of eleven

sional stabrlity of three current elastomers. I Oral Rehabil

elastomeric impression materials . I Prosthet Dent 1984;

achieve fit in implant prosthodontics: A review of the lit­

t983:tO:J2S-333·

S 2 : t 2o-t2S.

erature. lnt I Prosthodont 1999:t2:t67-178.

52.

plant impression splinted techniques: Efect of splinting

Riedy SJ, Lang BR, Lang BE. Fit of implant frameworks fabricated by diferent techniques. J Prosthet Dent 1997:

Wil liams PT, Jackson DG, Bergman W. An evaluation of

61. Assif D, Nissan J. a rsano I, Singe r A. Accuracy of im­

3t5

t P ER Custom Impression Trays a n d I mpression Materials

23.

24.

Lepe X, Johnson GH, Berg JC. Surface characteristics of

materials for monophase elastic impression making. t nt

used on gingival retraction cords. I Prosthet Dent 1993:

181 186.

I Prosthodont 2002:t5: t68-t74·

70:114 -117.

rmpression materials. I Dent Res 1984:6) : 1 5 5 157.

polyvinyl siloxane putty-wash impression techniques. I

Salem NS, Combe EC, Watts DC. Mechanical propenres

Prosthet Dent 2000;8):16t-t6s.

·

76:) 56-)62.

of elastomeric impression materials. I Oral Rehabil

Thouati , Deveaux E. lost A. Behin P. Dimensional sta·

1988:t 5 : 12S-132. 35.

29.

36. Albers HF. Impressions: A Text for Selection of Materials

meric impression materials. J Prosthet Dent 1999;81:

and Techniques. Santa Rosa, A: Alto Books, 1990:

621-624.

45-46.

Johnson GH, Chellis KD, Gordon GE, Lepe X. Dimen·

37·

effects of diferent storage conditions on polyether and

hydrocolloid and elastomeric impressions disinfected

polyvinylsiloxane impressions. I Am Dent Assoc 1998: 129:1014-1021. 38.

Dent 199t:65=743.748.

prostheses and the master casts in routine edentulous

Hung SH, Purk JH. nra DE, Eick JD. Accuracy of one·step

situations. 1 Oral Rehabil 1995 : 2 2 : 5 5 7-564.

46.

bulk on the accuracy of polyvinyl siloxane putty·wash

ing implant-suppoted prostheses in the edentulous jaw.

als. Gen Dent 2000:48:646-648. 48.

Corso M, Abanomy A, Di Canzio J. Zurakowski D,

58.

Jemt T, Book K. Prosthesis misfit and marginal bone

Spector MR, Donovan TE, Nicholls 11. An evaluation of

loss in edentulous implant patients. lnt I Oral axillofac

impression techniques for osseointegrated implants. I

Implants 1996:11:62o625.

Prosthet Dent 1990:63:444-447·

of the accuracy of implant

626-6)1.

Prosthet Dent 1993:69:s88-s93·

49·

lnt I Oral axilloac Implants 1996: 1 1 : t 5 1-158.

Giordano R 2nd. Issues in handling impression materi­

ether impression materials. I Prosthet Dent 1998:79:

S9·

Wee AG. Comparison of impression materials for direct multi-implant impressions. I Prosthet Dent 2000:83:

Hsu CC. Millstein PL. Stein RS. A comparative analysis transfer techniques. J

32)-))1.

6o. Romero GG, Engelmeier R, Powers )M, Canterbuy A.

Phillips KM, Nicholls 11. Ma T, Rubenstein )E. The accu·

Accuracy of three corrective techniques for implant bar

vanced fixed prosthodontics: A comprehensive review.

racy of three implant impression techniques: A three­

fabrication. I Prosthet Dent 2000:84:6o2-607.

Pract Periodontics Aesthet Dent 1999:11:497-504.

dimensional analysis. lnt I Oral Maxillofac Implants

Keck SC. Automixing: A new concept ln elastomeric

•994:9=533-540.

Lee A. Predictable elastomeric impressions in ad·

Detail reproduction, contact angles, and die hardness of

impression material delivey systems. J Prosthet Dent

elastomeric impression and gypsum die material com·

1985 : 54=479-48). 41.

Dent 1996:75:)14-324. S7· Jemt . In vivo measurements of precision of it involv­

impressions. I Oral Rehabil 2002;29:35 7-)61. 47.

Science, 1998:1 18-126.

40.

fit at the implant prosthodontic interace. J Prosthet

Nissan 1. Gross M, Shifman A, Assif D. Efect of wash

Lepe X, Johnson GH, Berg )(, Aw TC, Stroh GS. Wetta­

Ragarn )(, Grosko ML, Raj M, Ryan TN, Johnston WM.

56. Jemt T, Rubenstein IE, Carlsson L, Lang BR. easuring

sion technique. I Prosthet Dent •992:67: 583-589.

dimensional stability of polyvinyl siloxane and poly·

binations. lnt J Prosthodont 2oo; t):214-22o.

314

ings and welded titanium frameworks. easurements of the precision of the it between completed implant

Morgana SM. The effect of temperature changes on the

268-276.

1996:11:21-222.

Tjan AH, Li . Efects of reheating on the accuracy of

(eds). Applied Dental Materials, ed 8. Oxford: Blackwell

39·

impression techniques. t nt I Oral Maxillofac Implants

addition silicone putty-wash Impressions. I Prosthet

cation and requirements. In: Mccabe JF. Walls AWG

bility, imbibition, and mass change of disinfected low·

single-tooth implants. lnt I Prosthodont 200t:t4:1S2-t58. Ass r f D. Marshak B, Schmidt A. Accuracy of implant

5 5 · Jemt . Three-dimensional distonion of gold alloy cast­

versus two-step putty wash addition silicone impres­

Purk )H, Willes MG, Tira DE, Eick JD, Hung SH. The

sional stability and detail reproduction of irreversible

cCabe )F, Walls AW. Impression materials: Classifi­

45·

Dent 1990:6):282-285.

disinfectant agents on dimensional stability of elasto­

viscosity impression materials. J Prosthet Dent 2002;88:

30.

Tam LE, Brown JW. The tear resistance of various im· pression materials with and without modifiers. J Prosthet

Adabo GL, Zanarottr E. Fonseca RG, Cruz A. Effect of

44.

Daoudi MF, Setchell DJ, Searson LJ. A laboratory investi· gation of the accuracy of two impression techniques for

43· Nissan J. Laufer BZ, Brosh T, ssif D. Accuracy of three

)). Keck SC, Douglas WH. Tear strength of non-aqueous

ical disinfectant solutions on the stability and accuracy 34

53.

54·

Rlos MP, Morgana SM. Stein RS, Rose L. Effeas of chem­

by immersion. J Prosthet Dent 1998:79=44-453· 28.

de Camargo LM, Chee W, Donovan TE. Inhibition of

after long-term disinfection. I Prosthet Dent 1995:74:

mersed in disinfectants. I Prosthet Dent 1996:76:8-14.

27.

42.

polymerization of polyvinyl siloxanes by medicaments

bility of seven elastomeric impression materials lm·

26.

Piwowarczyk A, Ottl P, Buchler A, Lauer HC, Hoffmann A. In vitro study on the dimensional accuracy of selected

of the dental impression complex. I Prosthet Dent 1996:

25.

)2.

a polyether and addition silicone impression materials

so.

51.

material. lnt J Oral axilloac Implants 1999:14 :88s-888. 62.

Wise M. Fit of implant-suppMed fixed prostheses fab­

78:596-6o4.

ricated on master casts made from a dental stone and

Wee AG, Aquilino SA, Schneider RL. Strategies to

a dental plaster. I Prosthet Dent 200t;86:sJ2-5J8.

31. Clancy JM, Scandrett FR, Ettinger RL Long-term dimen­

the time-dependent dimensional stability of eleven

sional stabrlity of three current elastomers. I Oral Rehabil

elastomeric impression materials . I Prosthet Dent 1984;

achieve fit in implant prosthodontics: A review of the lit­

t983:tO:J2S-333·

S 2 : t 2o-t2S.

erature. lnt I Prosthodont 1999:t2:t67-178.

52.

plant impression splinted techniques: Efect of splinting

Riedy SJ, Lang BR, Lang BE. Fit of implant frameworks fabricated by diferent techniques. J Prosthet Dent 1997:

Wil liams PT, Jackson DG, Bergman W. An evaluation of

61. Assif D, Nissan J. a rsano I, Singe r A. Accuracy of im­

3t5

C H A P T E R

1 0

L A B O RAT O R Y

P R O C E D U RES

FIG 10-2

FIG 10-1

C R EATI O N OF THE W O R K I N G CAST

Because plaster is compatible with all i mpression materials and can be used with the various comput­

I m pression a nalysis

W O R K I N G

erized scanning systems (computer-aided design/com­

C A S T

S Y S T E M S

puter assisted manufacturing ICAD/CAMD. it is the

High-quality restorations begin with correct impres­

material of choice for making casts. Using plaster

sions, since errors and minor defects in the impres­

guarantees predictable results from practical and

sion are inevitably transferred to the working cast

well-tested techniques.

and may compromise the final adaptation of the

Plaster also is the most economical material avail­

restoration. The dental technician must not only

able for cast fabrication, and in addition to its pre­

take perfect impressions in the laboratory, but also

cision, it ofers the hardness and compression resis­

examine them carefully under the microscope to con­

tance essential to working on a cast without risking

irm that their dimensions and detail reproduction

surface damage.J-7 Varieties of plaster are classified

are precise (Fig 10-1). Once the accuracy of the im­

in terms of their degree of expansion, flexion, com­

pression is confirmed, extreme care must be taken

pression resistance, and hardness. The most common

to avoid introducing mistakes during the fabrication

types are natural plasters fortified with low-expansion

of the master cast to guarantee optimal adaptation

synthetic resin6 (ResinRock, Whip Mix), which offer

and integration of the restoration i n the oral cavity.

high resistance to abrasion and scratches,6.8 good

Materials for master working casts

of the finest type IV plasters, and favorable volu­

FIG 10-J

FIG 1 0-4

plasticity, dimensional stability comparable to that

311

metric expansion ranging from o.o7% to o.o8%.

The technician selects a cast material that is com­

Alternatives to plaster include epoxy and poly­

patible with the type of cast to be made and the

urethane resins. Unlike plasters, which expand, these

type of impression material that was used, because

materials are characterized by volumetric shrinkage

interaction between incompatible materials can give

of o.os%. but they have been shown to provide

rise to imperfections.'·' Manufacturers offer a vast

precise detail reproduction. Their two basic compo­

range of construction systems (eg, Model-Tray System,

nents, resin and polyamine, begin to polymerize as

Model-Tray) and cast materials, such as plasters and

soon as they are mixed; the resin must be poured

polyurethane and epoxy resins.

immediately into the impression while it remains in ..

Fig 10-1 To create a working cast with good dimensional precision and excellent detail reproduction. the dentat technician must work with a precise impression. Note the detailed reproduction of the finish tine. Figs 10-2 and 10-3 Ouatity of the restoration atso depends on the precision of the master cast. Each stage must be performed using tho appro­ priate materials and systems. Fig 10-4 Plaster cast from a reversible hydrocolloid impression. Given the water absorption and secretion of hydrocolloid materials. the tech­ nician must pour a cast within 10 minutes of taking the impression.

317

C H A P T E R

1 0

L A B O RAT O R Y

P R O C E D U RES

FIG 10-2

FIG 10-1

C R EATI O N OF THE W O R K I N G CAST

Because plaster is compatible with all i mpression materials and can be used with the various comput­

I m pression a nalysis

W O R K I N G

erized scanning systems (computer-aided design/com­

C A S T

S Y S T E M S

puter assisted manufacturing ICAD/CAMD. it is the

High-quality restorations begin with correct impres­

material of choice for making casts. Using plaster

sions, since errors and minor defects in the impres­

guarantees predictable results from practical and

sion are inevitably transferred to the working cast

well-tested techniques.

and may compromise the final adaptation of the

Plaster also is the most economical material avail­

restoration. The dental technician must not only

able for cast fabrication, and in addition to its pre­

take perfect impressions in the laboratory, but also

cision, it ofers the hardness and compression resis­

examine them carefully under the microscope to con­

tance essential to working on a cast without risking

irm that their dimensions and detail reproduction

surface damage.J-7 Varieties of plaster are classified

are precise (Fig 10-1). Once the accuracy of the im­

in terms of their degree of expansion, flexion, com­

pression is confirmed, extreme care must be taken

pression resistance, and hardness. The most common

to avoid introducing mistakes during the fabrication

types are natural plasters fortified with low-expansion

of the master cast to guarantee optimal adaptation

synthetic resin6 (ResinRock, Whip Mix), which offer

and integration of the restoration i n the oral cavity.

high resistance to abrasion and scratches,6.8 good

Materials for master working casts

of the finest type IV plasters, and favorable volu­

FIG 10-J

FIG 1 0-4

plasticity, dimensional stability comparable to that

311

metric expansion ranging from o.o7% to o.o8%.

The technician selects a cast material that is com­

Alternatives to plaster include epoxy and poly­

patible with the type of cast to be made and the

urethane resins. Unlike plasters, which expand, these

type of impression material that was used, because

materials are characterized by volumetric shrinkage

interaction between incompatible materials can give

of o.os%. but they have been shown to provide

rise to imperfections.'·' Manufacturers offer a vast

precise detail reproduction. Their two basic compo­

range of construction systems (eg, Model-Tray System,

nents, resin and polyamine, begin to polymerize as

Model-Tray) and cast materials, such as plasters and

soon as they are mixed; the resin must be poured

polyurethane and epoxy resins.

immediately into the impression while it remains in ..

Fig 10-1 To create a working cast with good dimensional precision and excellent detail reproduction. the dentat technician must work with a precise impression. Note the detailed reproduction of the finish tine. Figs 10-2 and 10-3 Ouatity of the restoration atso depends on the precision of the master cast. Each stage must be performed using tho appro­ priate materials and systems. Fig 10-4 Plaster cast from a reversible hydrocolloid impression. Given the water absorption and secretion of hydrocolloid materials. the tech­ nician must pour a cast within 10 minutes of taking the impression.

317

CHA Laboratoy Procedures

I

"" the plastic phase and, because of its sensitivity to moisture, kept in a dry environment.

thus reduces the potential for material difficulties.

"" 10-6). This layer of polyurethane resin prevents

care is taken to safeguard all pertinent anatomic

expansion of the plaster cast from absorption of the

information. The dies are then repositioned in the

bonder of the Plexiglas base, which would alter the

impression, and a plaster cast of the remaining arch

I n general, polyurethane resins (PX Extrarock, PX

The Zeiser system (Zeiser Dental) is composed of

Dental) are not compatible with all impression mate­

a removable cast that is easily inserted into a Plexi­

rials and should not be used with either polysulfide

glas base. Unlike the Pindex system from which it

The dies must be separated by hand, preferably

seves the anatomic details of the soft tissues while

or hydrocolloid impressions. Although they are com­

evolved, the Zeiser system guarantees precise adap­

using the microscope, for optimal control and to

permitting the technician to work with removable

patible with polyethers, an isolating product (PX

tation of the cast material and this Plexiglas (former­

prevent accidental damage to the

preparation

resin dies that precisely imitate the radicular anato­

Extrarock D, PX Dental) should be used to prevent

ly plaster) base, and thus greater control of linear­

edges. However, for a fixed partial denture, the tech­

my of each individual tooth (Figs 10-11 and 10-12).

is poured. The result is a working cast that pre­

cast's physicochemical characteristics.

bonding between the i mpression material and the

though not volumetric- movement. Brass pins in the

nician should keep the area together in a block

Such an anatomic cast is an optimum reproduction

resin.

base of each sectioned part are adapted to the

rather than separating individual dies (Fig 10·7).

of the clinical situation, and it proves very useful for

The obvious diferences between resin and plas­

Plexiglas base by means of calibrated, heat-aided

Keeping the restoration section in one piece gives

subsequent restoration phases (Figs 10-13 to 10-16).

ter concern their respective expansion and contrac­

drilling, providing optimal stability to each remov­

the technician maximum stability and preserves the

The Model System (Tricodent) 13 for preparing a

tion properties. Nonetheless, findings of dimension­

able die.10·u

distances between the dies and thus the exact

working cast is easy, practical, and economic. The

al testing9- 10 to assess differences in detail repro­

During preparation of the master cast, the pre­

dimensions of the clinical situation. Taking this pre­

system includes a special plastic box for holding the

duction indicate that casts made from both materials

pared dies are coated with a special silicone (Pro­

caution assumes even greater importance when a

plaster cast; this box is equipped with internal ver­

reproduce details accurately. When compared, neither

tector, Benzer Dental) to create a protective film that

ceramic margin (36o-degree or collarless) is planned

tical grooves for repositioning the dies and two side

epoxy resin shrinkage nor plaster expansion has a

will be removed only when the cast is complete (Figs

for the entire circumference of the restoration or

clips that can open to block the plaster model: on

signiicant clinical efect. When appropriate procedures

10-2 and 10·3).

when the shoulder portion of the ceramic is layered

the back are two small rest levers that permit com­

solely on the buccal surface.

plete extraction. The borders of the impression are

are followed, both materials meet the American

In pouring the cast, particular attention should be

Dental Association (ADA) guidelines for a precision

paid to the intrinsic properties of the i mpression

To facilitate subsequent procedures carried out in

crown ater cementation.

material. Hydrocolloids, for example, limit normal

making the wax pattern, such as trimming the mar­

from the gingival tissues, so it is possible to mark

laboratory procedures and require modified cast prep­

gins (or allowing for the possibility of ceramic mar­

the midline so as to facilitate alignment of the

tant properties that distinguish the two materials.

aration. Because hydrocolloids vary dimensionally

gins), a laboratory bur should be used to remove

impression with the central axis in the Tricodent sys­

Because of its hardness. an epoxy resin cast is less

through water absorption and secretion, the plaster

plaster in the areas corresponding to the mucous

tem. During this construction phase the two black

fragile and therefore maintains details and precision 10

cast must be developed in 10 minutes or less. Such

membrane in the edentulous zone (Fig 10·8).12 To

closure clips are adapted and, once the base has

better during laboratory procedures and generates

time restriction precludes the possibility of creating

record the details of the soft tissue in the edentu·

been isolated with a silicone material, the impres­

less stress for the dental technician.

a Zeiser-type master cast directly from hydrocolloid

lous zone, a rigid silicone cast (Gingifast Rigid,

sion is cast by filling the tray with type IV extra-hard

Since both plaster and resin materials are subject

impressions. Therefore, if hydrocolloids are used, the

Zhermack) can be used to allow easy repositioning

plaster. Before the plaster hardens, the impression

to aging and deterioration, technicians also must be

clinician must immediately pour a cast (Fig 10-4)

on the master cast as needed (Figs 10-9 and 10-10).

tray is positioned upside-down on the system, taking

aware of expiration dates, especially once the pack­

using a vacuum mixer and send it to the laboratory

Alternatively, a polyurethane resin cast (PX Extra­

care to remove all excess material. Single-plaster

rock) can be made using only the individual dies

casting is one of the advantages of modern systems (Fig 10·17)- 10,1 1,14.15

Breakage and wear resistance are the most impor­

age has been opened.•-6-1o

318

that greatly si mplifies the laboratory procedures and

for fabrication of the master cast. Afteward, the prepared dies are covered with iso­

that are involved rather than the entire arch. The

lating silicone, and the plaster is trimmed with a dy­

individual master dies of resin are roughed out, and

Systems a n d methods for cast construction

cast squaring machine (Trimex Px 1000, Micerium).

To ensure the stability of the working cast, the dental

low-contraction polyurethane resin (PX Extrarock)

technician can use a technique for cast construction

between the cast and Plexiglas base (Figs 10-5 and .

rounded of, leaving a distance of at least 6 mm

..

Following the Zeiser technique, the technician layers

319

CHA Laboratoy Procedures

I

"" the plastic phase and, because of its sensitivity to moisture, kept in a dry environment.

thus reduces the potential for material difficulties.

"" 10-6). This layer of polyurethane resin prevents

care is taken to safeguard all pertinent anatomic

expansion of the plaster cast from absorption of the

information. The dies are then repositioned in the

bonder of the Plexiglas base, which would alter the

impression, and a plaster cast of the remaining arch

I n general, polyurethane resins (PX Extrarock, PX

The Zeiser system (Zeiser Dental) is composed of

Dental) are not compatible with all impression mate­

a removable cast that is easily inserted into a Plexi­

rials and should not be used with either polysulfide

glas base. Unlike the Pindex system from which it

The dies must be separated by hand, preferably

seves the anatomic details of the soft tissues while

or hydrocolloid impressions. Although they are com­

evolved, the Zeiser system guarantees precise adap­

using the microscope, for optimal control and to

permitting the technician to work with removable

patible with polyethers, an isolating product (PX

tation of the cast material and this Plexiglas (former­

prevent accidental damage to the

preparation

resin dies that precisely imitate the radicular anato­

Extrarock D, PX Dental) should be used to prevent

ly plaster) base, and thus greater control of linear­

edges. However, for a fixed partial denture, the tech­

my of each individual tooth (Figs 10-11 and 10-12).

is poured. The result is a working cast that pre­

cast's physicochemical characteristics.

bonding between the i mpression material and the

though not volumetric- movement. Brass pins in the

nician should keep the area together in a block

Such an anatomic cast is an optimum reproduction

resin.

base of each sectioned part are adapted to the

rather than separating individual dies (Fig 10·7).

of the clinical situation, and it proves very useful for

The obvious diferences between resin and plas­

Plexiglas base by means of calibrated, heat-aided

Keeping the restoration section in one piece gives

subsequent restoration phases (Figs 10-13 to 10-16).

ter concern their respective expansion and contrac­

drilling, providing optimal stability to each remov­

the technician maximum stability and preserves the

The Model System (Tricodent) 13 for preparing a

tion properties. Nonetheless, findings of dimension­

able die.10·u

distances between the dies and thus the exact

working cast is easy, practical, and economic. The

al testing9- 10 to assess differences in detail repro­

During preparation of the master cast, the pre­

dimensions of the clinical situation. Taking this pre­

system includes a special plastic box for holding the

duction indicate that casts made from both materials

pared dies are coated with a special silicone (Pro­

caution assumes even greater importance when a

plaster cast; this box is equipped with internal ver­

reproduce details accurately. When compared, neither

tector, Benzer Dental) to create a protective film that

ceramic margin (36o-degree or collarless) is planned

tical grooves for repositioning the dies and two side

epoxy resin shrinkage nor plaster expansion has a

will be removed only when the cast is complete (Figs

for the entire circumference of the restoration or

clips that can open to block the plaster model: on

signiicant clinical efect. When appropriate procedures

10-2 and 10·3).

when the shoulder portion of the ceramic is layered

the back are two small rest levers that permit com­

solely on the buccal surface.

plete extraction. The borders of the impression are

are followed, both materials meet the American

In pouring the cast, particular attention should be

Dental Association (ADA) guidelines for a precision

paid to the intrinsic properties of the i mpression

To facilitate subsequent procedures carried out in

crown ater cementation.

material. Hydrocolloids, for example, limit normal

making the wax pattern, such as trimming the mar­

from the gingival tissues, so it is possible to mark

laboratory procedures and require modified cast prep­

gins (or allowing for the possibility of ceramic mar­

the midline so as to facilitate alignment of the

tant properties that distinguish the two materials.

aration. Because hydrocolloids vary dimensionally

gins), a laboratory bur should be used to remove

impression with the central axis in the Tricodent sys­

Because of its hardness. an epoxy resin cast is less

through water absorption and secretion, the plaster

plaster in the areas corresponding to the mucous

tem. During this construction phase the two black

fragile and therefore maintains details and precision 10

cast must be developed in 10 minutes or less. Such

membrane in the edentulous zone (Fig 10·8).12 To

closure clips are adapted and, once the base has

better during laboratory procedures and generates

time restriction precludes the possibility of creating

record the details of the soft tissue in the edentu·

been isolated with a silicone material, the impres­

less stress for the dental technician.

a Zeiser-type master cast directly from hydrocolloid

lous zone, a rigid silicone cast (Gingifast Rigid,

sion is cast by filling the tray with type IV extra-hard

Since both plaster and resin materials are subject

impressions. Therefore, if hydrocolloids are used, the

Zhermack) can be used to allow easy repositioning

plaster. Before the plaster hardens, the impression

to aging and deterioration, technicians also must be

clinician must immediately pour a cast (Fig 10-4)

on the master cast as needed (Figs 10-9 and 10-10).

tray is positioned upside-down on the system, taking

aware of expiration dates, especially once the pack­

using a vacuum mixer and send it to the laboratory

Alternatively, a polyurethane resin cast (PX Extra­

care to remove all excess material. Single-plaster

rock) can be made using only the individual dies

casting is one of the advantages of modern systems (Fig 10·17)- 10,1 1,14.15

Breakage and wear resistance are the most impor­

age has been opened.•-6-1o

318

that greatly si mplifies the laboratory procedures and

for fabrication of the master cast. Afteward, the prepared dies are covered with iso­

that are involved rather than the entire arch. The

lating silicone, and the plaster is trimmed with a dy­

individual master dies of resin are roughed out, and

Systems a n d methods for cast construction

cast squaring machine (Trimex Px 1000, Micerium).

To ensure the stability of the working cast, the dental

low-contraction polyurethane resin (PX Extrarock)

technician can use a technique for cast construction

between the cast and Plexiglas base (Figs 10-5 and .

rounded of, leaving a distance of at least 6 mm

..

Following the Zeiser technique, the technician layers

319

CHAPTER 1 0 Laboratoy Procedures

I

Fig 10-5 Creating a Zeiser-type master cast from a hydrocolloid impression requires a different procedure than that used lor a polyether impression. It is necessary to modify the development of the impression on the basis of the material itself. Fig 10-6 Layering polyurethane resin between the cast and the Plexiglas base guarantees better dimensional stability lor the whole system. Fig 10-7 In the case of a fixed partial denture. the cast should be sectioned into blocks to improve stability between dies and reduce movement between the elements of the connected structure. Fig 10-8 Block-cut cast used to create a cermet fixed partial denture with a ceramic micromargin. Fig 10-9 Gingival reproduction in rigid silicone is necessary to prevent loss of soft tissue detail in the edentulous zone and monitor the progress of the gingiva. Fig 10-1D Definitive restoration in situ. Note the integration with the soft tissue as well as the stability and precision of the fixed partial den­ ture. Fig 1D-11 Construction of a master cast with removable dies in polyurethane resin. This type of cast accurately records soft tissue detail in the plaster. Fig 1D-12 Definitive cermet crown with a ceramic micromargin on the removable die. This type of cast makes it possible to remove an individual die from the cast. which facilitates work. Figs 10-13 to 10-16 Perfect correspondence between the master cast and the postcementation clinical situation for both the right and left lateral sectors. respectively. The construction of this type of cast can effective­ ly reproduce the oral cavity. Fig 1D-17 Tricodent-type master cast. equipped with a plastic base. The correct position of the removable dies is guaranteed by the grooves inside the box and the lateral blockage system. which uses special sell-blocking clips. o

321

CHAPTER 1 0 Laboratoy Procedures

I

Fig 10-5 Creating a Zeiser-type master cast from a hydrocolloid impression requires a different procedure than that used lor a polyether impression. It is necessary to modify the development of the impression on the basis of the material itself. Fig 10-6 Layering polyurethane resin between the cast and the Plexiglas base guarantees better dimensional stability lor the whole system. Fig 10-7 In the case of a fixed partial denture. the cast should be sectioned into blocks to improve stability between dies and reduce movement between the elements of the connected structure. Fig 10-8 Block-cut cast used to create a cermet fixed partial denture with a ceramic micromargin. Fig 10-9 Gingival reproduction in rigid silicone is necessary to prevent loss of soft tissue detail in the edentulous zone and monitor the progress of the gingiva. Fig 10-1D Definitive restoration in situ. Note the integration with the soft tissue as well as the stability and precision of the fixed partial den­ ture. Fig 1D-11 Construction of a master cast with removable dies in polyurethane resin. This type of cast accurately records soft tissue detail in the plaster. Fig 1D-12 Definitive cermet crown with a ceramic micromargin on the removable die. This type of cast makes it possible to remove an individual die from the cast. which facilitates work. Figs 10-13 to 10-16 Perfect correspondence between the master cast and the postcementation clinical situation for both the right and left lateral sectors. respectively. The construction of this type of cast can effective­ ly reproduce the oral cavity. Fig 1D-17 Tricodent-type master cast. equipped with a plastic base. The correct position of the removable dies is guaranteed by the grooves inside the box and the lateral blockage system. which uses special sell-blocking clips. o

321

I hi· fltll',lt IH,i· llllh •I 11•·11 ·.il.rrpt·flt·d Hl',lttJrt••·ul ·.lfll

11.11 Ill

t)uf

lf·i llfiS I H''(MtHt I •I

(ifi'P·H•·

IHW. h II lito oil f t••,•, IJ·,u·� ·.p�·t "' ' di.JirttHJtl

iHW� jMh•tllt'fi b t tllii •HJIIIIJI'II ��� 1 '11J t}/tJ .uuj (tJifjt•tJ

lt,l '•IJH•tl, I ll••

111

W,0·>•·>3

the restoration. In general, the procedure involves

used extensively.23·43 Compared with more recent

with the exception that the former cements exhibit a

isolation of the surface oxygen with a glycerine gel

cementation materials, this cement has a number of

deterioration of mechanical stresses in some perfor·

to ensure final polymerization of the thin cement

disadvantages. such as solubility in a moist environ· ..

of patients. Following are three case presentations that demonstrate these ideals (Figs 13-60 to 13·91). •

31

.-

Cement at ion -: = . .J

--� � -

--

TAB L E 1 3 - 1 Clinical i n dications for various cements and prosthetic restorations

Zinc Type of restoration Metal-ceramic crowns with weak margins

Zinc

polycar-

phosphates

boxylates

/-

++

+

+

+

/-

+

+

with ceramic micromargins

ZOE -

I-

-

/-

-

Feldspathic ceramic crowns or veneers

-

-

-

Cast ceramic or leucite crowns or veneers

-

-

-

Ceramic crowns with alumina/zirconia core

-

-

-

Non-noble alloy and ceramic resin-bonded adhesive prosthesis

-

-

-

Acrylic resin provisional crowns

-

+

/

-

+

/-

-

++

Metal-ceramic crowns with AGC (Wieland)

-

++

(-) Strongly discouraged;

-

2

() *

Used by the authors.

(GI) glass-ionomer cement.

(/) + -

not recommended;

(+)

possible;

( ) ++

recommended;

(

)

+++

+++

+++

*

*

*

(without eugenol) -

strongly recommended.

L

resins

-

-

++

-

-

-

+++

-

II-

-

+++

/-

+

-

-

-

-

*

I-

+

+++

+

+++

-

+

/*

/-

+++ *

+++

-

DualPhotopolymerizing polymerizing adhesive resins adhesive resins

-

+

+++

Auto· polymerizing adhesive resins

/-

+++

+

-

++

GIC

/

+++

*

Nonadhesive

+ -

+

or Captek (Precious Chemicals) systems (ZOE) Zinc oxid�ugenol;

*

+

-

+

permanent cementation without adhesive resin

+++

-

+

with dentinal sensitivity

GIC

Resinmodified

-

-

/-

+++

I

+++

+

+ -

I-

++

-

+++

*

*

*

++

+

-

+

-

+ -

/

++

-

-

-

-

-

-

-

-

-

-

-

++

+++

+++

*

*

Cementation

1 3-67

Fig 1 3-60 Clinical case of a 40-year-old patient with macrodontia of the maxillary right central incisor and a direct composite restoration of congruent shape and color on the maxillary lefl central incisor following a previous trauma. The obvious esthetic compromise depended on the anomalous width-height ratio of the teeth. The diagnostic waxup and periodontal crown lengthening treatment were designed to improve the width-length ratio.

Fig 13-61 Surgical lengthening of the clinical crown and changes via a delicate stripping procedure using diamond-studded inserts on an EVA­ type handpiece (61 LR head fitted on a 20 LH low-speed or on a 2 g LH reducer handpiece. Oentatus) and medium-grit metal strips. Fig 13-62 Clinical results 6 months after periodontal crown lengthening.

figs 13-63 and 13-64 Analysis with a periodontal explorer that demonstrates the 1 3-mm length o f the clinical crown o n the right central incisor following surgery. The new emergence profile enables a redistribution of space. Preparation of the lefl central incisor involves changing the shape of the tooth to achieve improved proportion among the teeth. Fig 13-65 Cementation of the provisional resin restoration following preparation of the four teeth for ceramic veneers. Figs 1 3-66 o 13-6g Views of the original restoration and the four new feldspathic ceramic veneers after cementation. figs 1 3-70 and 13-71 Patient's smile before and after treatment. The porcelain laminate veneers show significant esthetic improvement in shape. color. and size ratio.

Cementation

1 3-67

Fig 1 3-60 Clinical case of a 40-year-old patient with macrodontia of the maxillary right central incisor and a direct composite restoration of congruent shape and color on the maxillary lefl central incisor following a previous trauma. The obvious esthetic compromise depended on the anomalous width-height ratio of the teeth. The diagnostic waxup and periodontal crown lengthening treatment were designed to improve the width-length ratio.

Fig 13-61 Surgical lengthening of the clinical crown and changes via a delicate stripping procedure using diamond-studded inserts on an EVA­ type handpiece (61 LR head fitted on a 20 LH low-speed or on a 2 g LH reducer handpiece. Oentatus) and medium-grit metal strips. Fig 13-62 Clinical results 6 months after periodontal crown lengthening.

figs 13-63 and 13-64 Analysis with a periodontal explorer that demonstrates the 1 3-mm length o f the clinical crown o n the right central incisor following surgery. The new emergence profile enables a redistribution of space. Preparation of the lefl central incisor involves changing the shape of the tooth to achieve improved proportion among the teeth. Fig 13-65 Cementation of the provisional resin restoration following preparation of the four teeth for ceramic veneers. Figs 1 3-66 o 13-6g Views of the original restoration and the four new feldspathic ceramic veneers after cementation. figs 1 3-70 and 13-71 Patient's smile before and after treatment. The porcelain laminate veneers show significant esthetic improvement in shape. color. and size ratio.

CHAPTE' Cementation

Fig 13-72 Clinical case in which the maxillary left anterior dentition requires restoration, the central incisor with a veneer and the lateral in cisor. canine. and both premolars with all-ceramic crowns. Fig 1 3-73 Definitive restoration immediately following cementation. Fig 13-74 Postoperative view. 3 years later. The stability of the tissues and the periodontal health confirm the validity of the operating technique.

Figs 13-75 and 13-77 Clinical case of a 32-year-old patient who wanted to replace the maxillary right lateral in cisor crown because of its poor esthetics. Removal of the crown revealed inadequate tooth preparation. in terms of health and shape. In addition to replacing the old restora­ tion after endodontic and restoration therapy. the clinician proposed restoring the two central incisors with porcelain laminate veneers. The left central incisor had a large restoration as a result of trauma. and the right central incisor had two Class 3 com posite restorations. The required restoration of the central incisors would give more personality to the overall smite.

Figs 13-78 to 13-79 fetdspathic ceramic restorations were cemented after tooth whitening and restorative treatment with a fiberglass pin. Figs 13-80 and 13-81 Magnification of the central incisors before and after adhesive cementation. Figs 13-82 and 13-83 Excellent integration of the fetdspathic ceramic restorations.

1

CHAPTE' Cementation

Fig 13-72 Clinical case in which the maxillary left anterior dentition requires restoration, the central incisor with a veneer and the lateral in cisor. canine. and both premolars with all-ceramic crowns. Fig 1 3-73 Definitive restoration immediately following cementation. Fig 13-74 Postoperative view. 3 years later. The stability of the tissues and the periodontal health confirm the validity of the operating technique.

Figs 13-75 and 13-77 Clinical case of a 32-year-old patient who wanted to replace the maxillary right lateral in cisor crown because of its poor esthetics. Removal of the crown revealed inadequate tooth preparation. in terms of health and shape. In addition to replacing the old restora­ tion after endodontic and restoration therapy. the clinician proposed restoring the two central incisors with porcelain laminate veneers. The left central incisor had a large restoration as a result of trauma. and the right central incisor had two Class 3 com posite restorations. The required restoration of the central incisors would give more personality to the overall smite.

Figs 13-78 to 13-79 fetdspathic ceramic restorations were cemented after tooth whitening and restorative treatment with a fiberglass pin. Figs 13-80 and 13-81 Magnification of the central incisors before and after adhesive cementation. Figs 13-82 and 13-83 Excellent integration of the fetdspathic ceramic restorations.

1

CHAPT:R 1 .

Cementation

1 3·86

Fig 13-4 Frontal view in relation to the mandibular dentition: esthetic a n d anatomic integration is apparent.

Fig 13-85 Occlusal view. The only tooth not incorporated in the restoration is the left lateral incisor.

Fig 13-86 Esthetic integration is evident through the stereomicroscope. The gingiva reflects periodontal health and good adaptation of the restorations. ig 13-87 Lateral view of the veneers under the stereomicroscope in relation to the mandibular teeth.

8

Figs 13-88 and 13-89 Stereomicroscopic views highlighting the health and esthetic achievement of the restorations. Figs 13-90 and 13-g 1 Frontal and occlusal views of the natural teeth highlight the transparent in cisal effects and the natural anatomy created for function.

CHAPT:R 1 .

Cementation

1 3·86

Fig 13-4 Frontal view in relation to the mandibular dentition: esthetic a n d anatomic integration is apparent.

Fig 13-85 Occlusal view. The only tooth not incorporated in the restoration is the left lateral incisor.

Fig 13-86 Esthetic integration is evident through the stereomicroscope. The gingiva reflects periodontal health and good adaptation of the restorations. ig 13-87 Lateral view of the veneers under the stereomicroscope in relation to the mandibular teeth.

8

Figs 13-88 and 13-89 Stereomicroscopic views highlighting the health and esthetic achievement of the restorations. Figs 13-90 and 13-g 1 Frontal and occlusal views of the natural teeth highlight the transparent in cisal effects and the natural anatomy created for function.

REFERE

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