Easy Endodontics For Clinical Practice [PDF]

Zitiervorschau

i

EASY ENDODONTICS

FOR CLINICAL PRACTICE with color atlasvolume I

hassan tantawy

iv

CONTENTS VOLUME 1 CHAPTER 1. DIAGNOSIS IN ENDODONTICS

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GENERAL VIEW 1

Contraindications to endodontic treatment 28

Chief complaint 1 Medical history 1 Extra oral examination 6

Reversible pulpitis 28 Teeth with hopeless prognosis 29

SPECIFIC VIEW 10

Irreversible pulpitis 31 Pulp necrosis 32 Periapical lesions of endodontic origin 32 Previously initiated treatment 35 Incomplete pathological root resorption 36 Perio-endo lesions 36 Elective endodontics 36

Indications to endodontics 31

Dental history 10 Intraoral examination (clinical diagnostic tests) 10 Radiographic examination 25

INDICATIONS AND CONTRAINDICATIONS OF ROOT CANAL TREATMENT 28

Referred pain 37

CHAPTER 2. RUBBER DAM IN ENDODONTICS BENEFITS OF RUBBER DAM IN ENDODONTICS 45 RELATIVE CONTRAINDICATIONS OF RUBBER DAM 45 RUBBER DAM ARMAMENTARIUM REVIEW 45 Rubber dam material (sheet) 46 Rubber Dam Punch & Rubber Dam Template 46 RUBBER DAM Frame (holder) 47 Rubber Dam Forceps 47 Clamps (retainers) 47 Modeling compound 49 Dental Floss 50 Wedges 50 Rubber Dam Napkin 50 Interproximal contact disk 50 Lubricant 50 Liquid dam 51

RUBBER DAM APPLICATION 58 Isolation planning 58 Preparation of the mouth 59 Preparation of the dam 59 Placement methods 60 Dam over clamp method 61 Winged clamp in dam method 61 Wingless clamp in dam method 62

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Clamp after dam method 62

Completion of rubber dam placement 64 Application of the napkin 64 Adjustment of the dam in the frame 64 Washing of the dam 65 Inversion of the dam 65 Ligation for retraction 65 Protection of the dam from tearing 65

Split dam method 67 Removal of the dam 68

OVERCOMING ISOLATION CHALLENGES 69 Isolation of Malpositioned and crowded teeth 69 Isolation of teeth with Extensive loss of coronal tissue 69 Isolation of teeth with poor retentive shapes 69 Isolation of Teeth with porcelain crowns 69 Isolation of teeth with inter-proximal interferences 70 Leakage problem 70 Repair of a torn rubber dam 70 Placement of Bite block 70 Unassisted Evacuation of fluid from the dam 70 Sealing a root concavity 70 Taking intraoperative radiographs 70 Root canal treatment of teeth with difficult access preparation 71 Narrow molar in mesiodistal direction 71

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CHAPTER 3. ENDODONTIC ACCESS CAVITY ROOT CANAL SYSTEM ANATOMY 75 Pulp chamber 75 Main Root canal 75 Classification of root canals (Vertucci’s classification) 75

Accessory root canals 76 Apical delta 76 Pulpal Isthmus 76 Apical foramen & apical constriction 76 Factors Affecting Internal Anatomy 77

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Access in badly destructed teeth (with No or Minimal clinical crown) 154

CLINICAL DETERMINATION OF THE ROOT CANAL CONFIGURATION DURING ACCESS PREPARATION 155 Coronal considerations 155 Midroot considerations 156 Laws of pulp chamber anatomy 156

ERRORS IN ACCESS CAVITY 158

ACCESS CAVITY OBJECTIVES 81 ACCESS CAVITY REQUIREMENTS 82 PROCEDURE OF ACCESS CAVITY OPENING 87 Instruments for Access Cavity Preparation 87 STEPS OF Access cavity opening 91 Individual shapes of access cavity of different teeth 102

CHALLENGING ACCESS PREPARATIONS 145 Access before rubber dam 145 Access through prosthetic crowns 146 Access through teeth prepared for prosthetic crowns 149 Access of teeth with Class V defects and restorations 150 Access in teeth with presumed calcified canals 151 Crowded or rotated teeth 154

Underextension 158 Mouse hole effect 158 Excessive Removal of Tooth Structure (Overextension) 159 PERFORATION 159 Opening wrong teeth 159 Canal blockage 159

COMPLEX ROOT CANAL SYSTEM 164 Classification of the grades of difficulty of endodontic treatment 164 Root canal complexities 164 C-shaped canals 164 Absent & Extra canals 166 Extra roots 168 Taurodontism 168 Pronounced curved canals 169 Dentinogenesis Imperfecta 170 Open Apex 171

MINIMAL INVASIVE ENDODONTICS/ RECENT TRENDS IN ENDODONTIC ACCESS PREPARATION 171

CHAPTER 4. WORKING LENGTH DETERMINATION DEFINITION AND IMPORTANCE OF WORKING LENGTH 179 ANATOMIC CONSIDERATIONS IN DETERMINING THE WORKING LENGTH 179 Anatomic apex 179 Radiographic apex 179 Average teeth length 180 Apical Constriction 180 Cemento-dentinal junction 180 Apical foramen 180

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coronal flaring 187 Precurvature of file 187 Root Canal negotiation (scouting step) 187

METHODS OF WORKING LENGTH DETERMINATION 194 Radiographic method 194 Non-radiographic methods 201 Traditional methods 201 Apex locator method 203

Combined method 213

CORONAL REFERENCE POINT 185 APICAL END POINT185 PRE-LENGTH DETERMINATION PROCEDURES 187

DETERMINING WORKING LENGTH IN TEETH WITH OPEN APICES 213

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CHAPTER 5. ROOT CANAL INSTRUMENTATION OBJECTIVES OF MECHANICAL PREPARATION (INSTRUMENTATION) OF ROOT CANAL 217 REQUIREMENTS (PRINCIPLES) OF SHAPING PROCEDURE 218 INSTRUMENTS USED IN SHAPING ROOT CANAL 221 MOTIONS USED FOR SHAPING ROOT CANAL 236 IMPORTANT PROCEDURES DURING ANY SHAPING TECHNIQUE 240 Initial pulp extirpation 240 MAINTAINING THE PATENCY OF THE APICAL FORAMEN 241 Preliminary enlargement of root canal 243 ANTICURVATURE FILING METHOD 248 Recapitulation 250

TECHNIQUES FOR SHAPING ROOT CANAL 251 Apical coronal techniques 252 Standardized technique 252 Conventional Step-back technique 252 Modified step-back techniques 257

Coronal apical techniques 259 Crown-Down/Step-Down Technique 259 Balanced force technique 260 Reverse Balanced Force Preparation 260

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Hybrid techniques 262

MECHANICAL SHAPING OF SPECIAL CASES 262 CLEANING AND SHAPING OF CONFLUENT ROOT CANALS 262 Curved Canals 264 Management of narrow (calcified) canals 269 Oval canals 271 Management of C-shaped canals 273 Canals with large apical foramen (open apex) 276 Root canals with Lateral canals 277 Extremely long root canals 278

FINAL EVALUATION OF ROOT CANAL 278 ERRORS DURING SHAPING ROOT CANAL 280 File fracture 280 Canal transportation 294 Ledge formation 301 Loss of working length 309 Iatrogenic Perforation 312 Under instrumentation 316 Over preparation (excessive removal of tooth structure) 317

Rotary endodontic Ni-Ti file systems 317

VOLUME 2 CHAPTER 6. ROOT CANAL DISINFECTION

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IMPORTANCE OF ROOT CANAL IRRIGATION 329 LUBRICANTS IN ENDODONTICS 331 MAIN IRRIGANTS IN ENDODONTICS 332

Manual method 345 Ultrasonic method 345 Microbrushes 346 Suggested Disinfection Protocol 350

0.5:5.25 % Sodium hypochlorite (NaOCl) 332 17 % EDTA solution 338 2 % Chlorhexidine (CHX) 339 Combination of NaOCl, CHX & EDTA 340 Saline and its use 342 RULES FOR IRRIGATION 342 ACTIVATION (AGITATION) OF IRRIGATION 345

Non setting Calcium hydroxide powder / paste 350 2% Chlorhexidine gel 352 Chlorhexidine mixed with calcium hydroxide 352 Antibiotic-corticosteroid combination 352 Triple-antibiotic paste 352

INTRACANAL MEDICATION 350

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CHAPTER 7. ROOT CANAL OBTURATION

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OBJECTIVES OF OBTURATION 355 CORRECT TIMING OF OBTURATION 355

OBTURATION IN DIFFICULT SITUATIONS 394

Single visit vs. multiple visits 355 Factors that determine number of treatment visits 356

Obturating canals with wide apical foramen 394 Obturating canals with very wide diameter (wide lumen) 396 Obturating extremely long canals 397 Obturating oval canals 379 Obturating confluent canals (type II) 399 Obturating splitting canals 402

CONVENTIONAL INSTRUMENTS USED FOR OBTURATION 358 PRE OBTURATION PROCEDURES 360 Obturating instrument selection 360 Master cone selection 361 Drying root canals 364

Obturating Type V root canal 402 Obturating Type III root canal 404 Obturating Type VI root canal 405

OBTURATING MATERIALS 364

POST OBTURATION CONSIDERATIONS 406

Core material (gutta-percha) 364 Properties of Gutta-percha 364 Types of Gutta-percha 365

Cleaning pulp chamber 406 Ensuring coronal seal 406 Post obturation radiograph 406 Post obturation pain 406

Sealers 367 Objectives 367 Ideal requirements of sealers 367 Conventional sealer types 368 Modern sealer types 369 Sealer Placement methods 376

COMMON ERRORS DURING OBTURATION 407

COLD OBTURATION TECHNIQUES 377 Single gutta-percha cone and sealer 378 Cold lateral compaction 379 Variation of cold lateral compaction 383

WARM OBTURATION TECHNIQUES 384 Continuous wave warm vertical compaction 384 Thermoplastic injection techniques 390 Thermoplastic carrier-based systems e.g. Thermafil system. 393

Under obturation (under filling) & under extension 407 Over obturation (over filling) & Over extension 409 Voids in obturation 417 Problems when placing and adapting a master gutta-percha point 418

MAINTAINING STERILITY OF THE ROOT CANAL SYSTEM DURING ROOT CANAL FILLING 421

CHAPTER 8. ROOT CANAL RETREATMENT

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CRITERIA OF FAILED ROOT CANAL TREATMENT423 CAUSES OF FAILED ROOT CANAL TREATMENT 425

Removal of Direct restorations 439 Removal of crowns and fixed partial dentures (FPD) 441 Removal of posts 448

Endodontic (Intraradicular) causes 425 Non-endodontic (Extraradicular) causes 425 Importance of preoperative radiograph in identifying the cause of the failure 426

STEP NO. 2: REMOVAL OF ROOT CANAL FILLING 459

FACTORS AFFECTING RETREATMENT DECISION 430 Wait and review decision 430 Extraction decision 432 Surgical retreatment choice 435

STEP NO. 1: ACCESS CAVITY AND REMOVAL OF CORONAL RESTORATION 437 Removal of coronal restorations (direct restorations, crowns, bridges, post& cores) 438

Improving Access cavity 458

General guidelines for removal of root canal filling 459 Removal of Conventional Gutta-percha filling 462 Different methods for removal of gutta-percha filling 462 Method selection 464 Removal of residual materials 465

Removal of Carrier based Gutta-Percha Obturators 469 Removal of plastic carriers 469 Removal of metal carriers 470

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Removal of gutta-percha core carriers 470

Management of post related perforation (perforation of middle third) 489 Management of apical Perforations of curved canals 489

Removal of Silver point filling 472 Removal of Pastes 474 Soft (non-setting) pastes 474 Hard pastes 474

Lack of coronal seal 499

STEP NO. 3: CORRECTION OF CAUSE OF FAILURE 476 MISSED CANALS 477 Under preparation and obturation 480 Overextension obturation 482 Apical Transportations 483 Repair of Iatrogenic Perforation 485 Factors Affecting Prognosis of Perforation Repair 485 MTA 486 Management of coronal lateral (buccal, palatal, mesial and distal) perforations 486 Management of coronal Perforations of the Pulp Chamber Floor 487 Management of Furcation or Strip perforations 488

SHAPING CONSIDERATIONS IN RETREATMENT 500 CLEANING (DISINFECTION) CONSIDERATIONS IN RETREATMENT 500 OBTURATION CONSIDERATIONS IN RETREATMENT 501 POSSIBLE COMPLICATIONS DURING RETREATMENT 501 Inter-appointment flare-ups 501 Thermal damage to periodontal tissues due to heat generation 502 Another treatment failure 503

CHAPTER 9. PERIO-ENDO LESIONS WHY ENDO-PERIO LESIONS COULD HAPPEN? 505 CAUSES OF INDIVIDUAL ENDODONTIC AND PERIODONTAL DISEASES 506 PATHOGENESIS AND TYPES OF PERIO-ENDO LESIONS 506 Endodontic etiology 506 Periodontal etiology 506 Combination of endodontic and periodontal etiologies 507 Iatrogenic etiology 507

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Common criteria of all perio endo lesions 510 Individual criteria of perio endo lesions 510 Treating primary endodontic lesions with pseudo periodontal disease 517 Treating primary endodontic lesions with secondary true periodontal disease 517 Treating primary periodontal lesions with pseudo endodontic disease 518 Treating primary periodontal lesions with secondary true endodontic disease 518 Treating true combined lesions 518

DIFFERENTIAL DIAGNOSIS AND MANAGEMENT OF PERIO-ENDO LESIONS 510

CHAPTER 10. PULP THERAPY IN CHILDERN DIFFERENCE BETWEEN PRIMARY AND PERMANENT PULPS 523 CLINICAL ASSESSMENT AND GENERAL CONSIDERATIONS 523 Indications of pediatric endodontics 523 Factors that can modify treatment planning (pulp therapy or extraction) 526

VITAL PULP THERAPY FOR PRIMARY MOLARS 529 Indirect pulp capping 529 Direct pulp capping 531 Partial pulpotomy 531 Complete pulpotomy 531

NON VITAL PULP THEARPY FOR PRIMARY TEETH 543

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PULP THERAPY FOR YOUNG PERMANENT TEETH 559 Difference between Pulpal treatment plan in Young Permanent Teeth & in primary teeth 560 The first situation: vital Pulp Therapy for Normal Pulp or Reversible Pulpitis without Pulp Exposure 561 The second situation: VitaI Pulp Therapy for Normal Pulp or Reversible Pulpitis with Pulp Exposure 563 The third situation: non-vital Pulp Treatment for Immature permanent Teeth 569 The forth situation: Non-vital Pulp in Young Mature Teeth 577

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CHAPTER 1 Diagnosis in endodontics Contents

Chief complain

Medical history

Dental history

Intra-oral examination

Indications and contraindications of root canal treatment

Radiographic examination

Extra-oral examination

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Easy endodontics for clinical practice

Figure 8 Bimanual palpation to explore the submandibular lymph nodes.

SPECIFIC VIEW Dental history History of present dental problem The chronology of events that led up to the chief complaint is recorded as the dental history: • When the problem began. • Whether there are factors that positively or negatively influence his presenting complaint, such as heat, cold, pressure, or mastication. • The frequency of the problem. • Whether there is pain; and if so, its location (whether the patient can identify the area of the responsible tooth, or whether the pain is diffuse), its origin (spontaneous or provoked), its character (sharp, dull, lingering, or throbbing), its duration (continuous or intermittent), and whether it is postural (whether the pain occurs in the evening, when the patient is recumbent).

History of previous dental treatment The other component of the dental history involves documenting any recent dental treatment in the offending area. If the patient is a new patient, the clinician should ask the patient about recent dental treatment. The information obtained can sometimes provide clues to guide the clinician toward an accurate diagnosis. For example, recent crown placement or prior pulp capping are positive findings that can lead to inflammation of pulp, even if the patient did not present with symptoms immediately after treatment was rendered.

Intraoral examination >> clinical diagnostic tests During this examination, the diagnosing clinician should consider any factors that might influence the accuracy of diagnosis. For example it was found that ibuprofen taken by patients prior to diagnostic testing could significantly affect the results of percussion, palpation, and cold testing. A more frequent concern is that patients who have experienced pain and/or swelling may already be taking antibiotics and analgesics that can mask signs and symptoms.

Visual and tactile examination With the help of mouth mirror and explorer hard and soft tissues of oral cavity should be examined. The gingiva and mucosa should be dried with either a low-pressure air syringe or a 2-by-2-inch gauze pad. Following aspects should be checked:

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Chapter 1. Diagnosis in endodontics

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Evaluation of oral hygiene status: Note that Poor oral hygiene in a mouth with many missing teeth testifies to a patient who very likely will not appreciate the dentist’s therapeutic efforts and thus does not deserve them. He will not know how to maintain in a state of good health the tooth that he asks the dentist to treat. Presence of intraoral swellings: Swelling in the anterior part of the palate is most frequently associated with an infection present at the apex of the maxillary lateral incisor or the palatal root of the maxillary first premolar (fig. 9). A swelling in the posterior palate is most likely associated with the palatal root of one of the maxillary molars (fig. 10). Presence of any intraoral sinus tracts: A sinus tract develops when a chronic infection drains to the surface and forms a nodule, known as a parulis (or stomata) (fig. 11). In general, a periapical infection that has an associated sinus tract is not painful, although often there is a history of pain & discomfort before sinus tract development. The stomata (parulis) of intraoral sinus tracts may open in the alveolar mucosa, in the attached gingiva, or through the furcation or gingival crevice. They may exit through either the facial or the lingual tissues depending on the proximity of the root apices to the cortical bone. Location of sinus tract according to tooth involved: • Maxillary teeth >> in Labial bone • Maxillary lateral incisor >> in Palatal bone • Palatal root of maxillary molar >> in Palatal bone • Mandibular anterior teeth >> in buccal vestibule • Mandibular posterior teeth >> in Lingual bone Note that if the opening is in the gingival crevice, it is normally present as a narrow defect in one or two isolated areas along the root surface. When a narrow defect is present, the differential diagnosis must include the opening of a periradicular endodontic lesion, a vertical root fracture, or the presence of a developmental groove on the root surface. This type of sinus tract can be differentiated from a primary periodontal lesion because the latter generally presents as a pocket with a broad coronal opening and more generalized alveolar bone loss around the root. Other pulp testing methods may assist in verifying the source of infection (if the pulp is vital, the cause would be primary periodontal lesion). Tracing test (fig. 12&13): • A sinus tract should be traced, when possible, because the location of the parulis may be distant to the source of the infection. • To trace the sinus tract, a size #25 or #30 gutta-percha cone is threaded into the opening of the sinus tract. Although this may be slightly uncomfortable to the patient, the cone should be inserted until resistance is felt. After a periapical radiograph is exposed, the origin of the sinus tract is determined by following the path taken by the gutta-percha cone. • This will direct the clinician to the tooth involved and, more specifically, to the part of the root of the tooth that is the source of the pathosis. Note that once the causative factors related to the formation of the sinus tract are removed, the stoma and the sinus tract will close within several days. Discoloured teeth:

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Any colour differences should be noted (Figure) as these may be a sign of pulpal hemorrhage, internal resorption, pulpal necrosis, microleakage, or staining from the root canal filling material (fig. 14-17). Degree of mouth opening: • Before conducting intraoral examination, check the degree of mouth opening. For a normal patient, it should be at least two fingers (fig.18). • If there is limited mouth opening, there will be difficulty to do root canal treatment in posterior teeth.

Palpation • A palpation test is performed by applying firm digital pressure with a rolling motion to the mucosa covering the roots and apices. The index finger is used to press the mucosa against the underlying cortical bone. This will detect the presence of periradicular abnormalities or specific areas that produce painful response to digital pressure (fig.19). • A positive response to palpation may indicate an active periradicular inflammatory process. However, this test does not indicate whether the inflammatory process is of endodontic or periodontal origin. • The test is most effective when it is performed simultaneously on the contralateral tooth for the purpose of comparison (fig.20).

Percussion • If the patient is experiencing acute sensitivity or pain on mastication, this response can typically be duplicated by individually percussing the teeth, which often isolates the symptoms to a particular tooth. • Percussion is performed by tapping on the incisal or occlusal surfaces of the teeth either with the finger or with a blunt instrument. The testing should initially be done gently, with light pressure being applied digitally with a gloved finger tapping (fig. 21). If the patient cannot detect significant difference between any of the teeth, the test should be repeated using the blunt end of an instrument, like the back end of a mirror handle (fig.22). • Pain to percussion does not indicate that the tooth is vital or nonvital but is rather an indication of inflammation in the periodontal ligament (i.e., symptomatic apical periodontitis). This inflammation may be secondary to physical trauma, teeth undergoing rapid orthodontic movement, occlusal prematurities (high points in a restoration), periodontal disease (lateral or apical periodontal abscess), or the extension of pulpal disease into the periodontal ligament space (endodontic origin). Positive response to the percussion test is a sure sign of an inflammatory process involving the periodontal space, probably of endodontic origin. A negative response, on the other hand, is not a definite sign of good health, because either pulp necrosis or chronic periapical inflammation is usually asymptomatic. • Degree of response to percussion is directly proportional to degree of inflammation. • Dull sound on percussion indicates abscess formation while sharp indicates inflammation. • Before percussing any teeth, the clinician should tell the patient what will transpire during this test. Because the presence of acute symptoms may create anxiety and possibly alter the patient’s response, properly preparing the patient will lead to more accurate results. It is prudent to test the contralateral side first so the patient can get accustomed to what a normal response feels like. • During testing for percussion sensitivity, it may be difficult for some patients to communicate the level of sensitivity clearly. If typical responses from a patient include “they all hurt” or “none of them hurt,” it may be better to perform tests on pairs of teeth at a time, similar to an eye exam with the optometrist. Some patients can provide a clearer response when asked to compare sensations between two teeth, as opposed to responding about sensitivity on one tooth. • Also, it is best not to inform the patient about which tooth is being tested. This ensures there is no bias in responses. • Note that teeth adjacent to the diseased tooth often show some tenderness because of the local spread of cytokines and neuropeptides that lower the pain threshold.

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Note that in some cases it may be necessary to treat the patient symptomatically and wait until the source of the pain becomes clear. This is especially important if more than one tooth in the area may be responsible for the patient’s symptoms.

Figure 9 Fluctuant swelling in the anterior palate associated with periradicular disease from the palatal root of the maxillary first premolar.

Figure 10 Fluctuant swelling in the posterior palate associated with periradicular disease from the palatal root of the maxillary first molar.

Intraoral swelling (yellow arrow) related to a maxillary posterior tooth.

Fluctuant swelling in the mucobuccal fold associated with periradicular disease from the maxillary central incisor.

Figure 11 intraoral sinus tract.

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Figure 12 Two GP points have been used to ‘track’ the sinus tracts

Figure 13 A, To locate the source of an infection, the sinus tract can be traced by threading the stoma with a gutta-percha point. B, Radiograph of the area shows an old root canal in a maxillary second premolar and a questionable radiolucent area associated with the first premolar, with no clear indication of the etiology of the sinus tract. C, after tracing the sinus tract, the gutta-percha is seen to be directed to the source of pathosis, the apex of the maxillary first premolar.

Figure 14 dark discoloration of a maxillary central incisor due to pulpal necrosis.

Figure 15 pink discolouration (white arrow) due to internal resorption in upper right central incisor.

Figure 16 color discoloration due to microleakage around composite.

Figure 17 discolored central incisor due to root canal treatment.

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Easy endodontics for clinical practice

Figure 18 Degree of mouth opening in a normal patient should be at least two fingers.

Figure 20 Bimanual palpation to ascertain the fluctuance of the purulent exudate.

Figure 19 palpation test. Tenderness to palpation assessed by gently pressing the mucosa

Figure 22 Percussion testing of a tooth, using the back end of a mirror handle.

Figure 21 Percussion test performed gently with the index finger.

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Chapter 1. Diagnosis in endodontics

Figure 23 Mobility testing of a tooth, using the back ends of two mirror handles.

A

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Figure 24 periodontal probing.

B

Figure 25 Vertical root fracture. A) A radiograph revealed a widened periodontal ligament with a J-shaped radiolucency around the apex. B) A periodontal probe indicated ore than 12 mm of probing depth. C) Exploratory surgery confirmed a vertical root fracture.

C

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Easy endodontics for clinical practice A

B Figure 26 cold tests. A) Cold testing being carried out; ice crystals have formed on the foam pellet following application of a refrigerant spray. B) Application of cotton pellet saturated with ethyl chloride.

Figure 27 Heat testing being carried out by syringing warm water on to a tooth isolated with rubber dam.

Figure 28 Heat testing being carried out using a warm GP point.

Figure 29 A rubber disc generates frictional heat on the metallic border, and this can be used to perform the heat test on a full crown tooth.

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CHAPTER 2 Rubber dam in endodontics Contents Benefits of rubber dam in endodontics

Relative contraindications of rubber dam

Overcoming isolation challenges Rubber dam application

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Chapter 2. Rubber dam in endodontics

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BENEFITS OF RUBBER DAM IN ENDODONTICS There are many advantages of using rubber dam but the following features are very important in endodontics:

Improving visualization The use of rubber dam Improve visibility by providing a dry field and minimizing mirror fogging.

Protecting the patient • The dam is the only way to prevent extrusion of exudates and/or root canal irrigants into the oral cavity. • The dam is the only tool to avoid accidental swallowing/inhaling of tools. Root canal treatment without dental dam isolation may place doctors under litigation risks if the patient swallows or aspirates an endodontic instrument.

Improving the quality of treatment • The dam is the only way to prevent endodontic contamination by oral cavity bacteria. • Thanks to the use of the rubber dam, the irrigants can work properly as their action is not compromised by the contamination arising from saliva and bacteria of the oral mouth. • Without the dam, in fact, mostly in posterior regions the practitioner tends to firmly grasp the tools out of fear they can slip from fingers. Thus, many iatrogenic misshapes can occur such as ledge, canal transportation….etc due to loss of tactile sensation on the instruments. • Rubber dam increase the focus of clinician in limited operative area. • Rubber dam Create a more efficient and favorable working environment by minimizing rinsing and patient conversations (without rubber dam, the patient usually rinse every minute).

RELATIVE CONTRAINDICATIONS OF RUBBER DAM There are few relative contra-indications to the application of the rubber dam as: • Respiratory tract obstructive diseases: can be managed by piercing the sheet away from the operative area to provide the patient with an air flow to the oral cavity. • Epilepsy and other motor disabilities. • Acute infections. • Extremely malpositioned tooth. • Third molar (in some cases).

RUBBER DAM ARMAMENTARIUM REVIEW Main components: • Rubber dam sheet • Rubber dam punch. • Rubber dam clamps • Rubber dam forceps • Rubber dam frame Rubber Dam Accessories: • Lubricant • Dental floss • Rubber dam napkin • Modeling compound • Wedge • Scissors

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Easy endodontics for clinical practice

• Interproximal contact disk • Liquid dam or flowable resin composite.

Rubber dam material (sheet) Sheet Size 5’’× 5’’ or 6’’ × 6’’ square. The most common size is the 6 × 6-inch square, which is used for isolation of posterior teeth in the permanent dentition. Another common size is the 5 × 5-inch square, which is used for primary dentition or anterior applications.

Sheet Thickness • The heavy and extra-heavy gauges are recommended for isolation. Why? Because: - The heavy dams are no more difficult to apply than are th e thinner materials. - Heavier dams are less likely to tear. - The heavier materials provide a better seal to teeth and retract tissues more effectively than the thinner materials. It is indicated for isolation of class V lesions. • Note that Thinner dam can pass through the contacts easier. Thus, it is indicated in teeth with tight contacts.

Sheet Color (fig.1) Available in several colors, but in endodontics a light-colored dam makes the operative field brighter and the intraoperative radiography easier.

Sheet Shelf life • Latex dam material that has exceeded its shelf life becomes brittle and tears easily; unfortunately, this is usually noticed during dam application. • A simple test for the resistance of rubber dam material to tearing is to attempt to tear a sheet grasped with thumbs and index fingers; a strong dam will be very difficult to tear.

Rubber Dam Punch & Rubber Dam Template (Hole-positioning guides) Rubber Dam Punch (fig.2) • Rubber dam punch is used to make the holes in the rubber sheet through which the teeth can be isolated. • It is characterized by a rotating metal disc, which bears five or six holes of different sizes, and a sharp pointed plunger. • The holes are of different sizes according to the size of different teeth. The Use of the particular hole suggested for that particular tooth should be performed, otherwise a tight seal will not be possible or the dam may tear during its placement (fig.3). • For standard latex heavy- gauge dams, recommended hole sizes are - Size 5 for clamped molars (anchor molars). - Size 4 for other molars. - Size 3 for premolars, canines, and maxillary central incisors. - Size 2 for maxillary lateral incisors. - Size 1 for mandibular incisors. • Some variation from the recommended hole sizes may be needed, depending on the size of individual teeth, operator preference, dam material, and gauge of the dam. • Holes must be cleanly cut; incompletely punched holes will promote tearing of the dam during application or will affect the ability of the dam to seal (fig.4). • When a prestamped dam or a template is used, the following tips should be noted: - Holes should be punched away from the spots to accommodate atypical alignment of teeth.

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Chapter 2. Rubber dam in endodontics

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- When the dam is being prepared to provide isolation for Class 5 restorations, the hole for the tooth to receive a facial Class 5 restoration should be punched approximately 1 mm facial to the spot to allow retraction with the no. 212SA clamp. - No holes should be punched for missing teeth (fig.5).

Hole-positioning guides (Rubber Dam Template) (fig.6) • Take a rubber dam sheet. Punch a hole on its upper right corner or mark it with ‘R’ for identifying the patient’s right side. • The sheet is then placed on a template and the position of the holes marked on it with a pen. • However with a template, only fixed positions can be obtained. When considerable variations are required, the dam can be centered on the teeth to be isolated and the positions marked (fig.7). • When the dam is in position it should reach up to a point just below the patient’s nose, thus covering the mouth but not the nose. To achieve this, the following should be considered: - When applying the rubber dam to the maxillary teeth or mandibular third molars, the position of the upper central incisors should be stamped about 2.5 cm (1 inch) from the top edge of the rubber sheet (fig.8). - For mandibular teeth the holes should be placed further up the sheet so that the rubber does not cover the nose. • Spacing between two holes in the dam should be adequate (approximately ¼ inch) (fig.9): - If inadequate little spacing is present between the holes, there are chances that the rubber dam sheet will move to the mesial or the distal of the papilla, thereby exposing and injuring the gingiva as well as not providing proper isolation. This also increases the chances of tear of the dam. - If the holes are over spaced, rubber dam will bunch in between the teeth thus interfering with the operative procedure.

RUBBER DAM Frame (holder) • Rubber dam frames support the edges of rubber dam. • Rubber dam frames are available in either metal or plastic (fig.10): A plastic frame is advantageous when radiographs will be a part of the procedure because it is radiolucent. The plastic frames do not, however, stand up to heat sterilization as well as do metal frames, and they have a shorter life span while Metal frames are less bulky and last for years. • The frame is preferably placed beneath the dam rather than above it.

Rubber Dam Forceps (fig.11) • Rubber dam forceps are used to carry the clamp to the tooth. • It should be taken care that forceps do not have deep grooves at their tips or they become very difficult to remove once the clamp is in place.

Clamps (retainers) (fig.12) • Clamps may be metallic or nonmetallic. Nonmetallic are made from polycarbonate plastic. An advantage of these clamps over metallic is radiolucency (preferred in endodontics due to need of frequent intraoperative radiography). • Some clamps simply have a number designation; others have a W in front of the number. The W indicates that the clamp is wingless while those clamps that do not bear a W have wings (fig.13). • Clamps should be expanded with the clamp forceps no more than is necessary for the clamp to be passed over the facial and lingual heights of contour of the tooth. If a clamp has been over expanded, it will grasp the tooth with less strength and is more likely to be dislodged. It is usually best to discard a clamp that has been overexpanded. • The number of clamps should be limited to a few that will satisfy most needs. Clamps that will serve in most situations are the following: - For molars (fig.14):

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Easy endodontics for clinical practice ✓ no. W8A or B1 (wingless clamps). ✓ no. 8A or 27 (winged clamps).

- For premolars (fig.15): ✓ no. W2A (wingless). ✓ no. 2A (winged). - For canines & incisors: no. 212SA (fig.16). • Supplemental clamps, to be available on the rare occasions when the usual clamps will not suffice, should be packaged and sterilized separately. Supplemental clamps include: - For partially erupted molars (fig.17): ✓ no. W14A (wingless). ✓ no. 14A (winged). - For asymmetrical molars (in particular second and third): 12 A& 13 A (fig.18) - For premolars with subgingival margins (fig.19): ✓ no. W1A (wingless). ✓ no. 1A (winged). - For mandibular incisors and other small teeth: no. 00 (winged). • The jaw angulation may vary according to the clamp type and it is very important from a clinical point of view: - Clamps with slightly tilted or flat jaws (bland clamps) are actually recommended for teeth with intact clinical crown since they are less traumatic to the periodontium. - While clamps with angulated jaws (retentive clamps) are made to reach the tooth at gingival sulcus depth, so they are recommended for teeth with damaged clinical crown. In multi-rooted teeth, aggressive-jawed clamps are very effective since their tilt allows them to reach for the stump deeply and apically to the tooth preparation end line (fig.21).

Butterfly clamp • The butterfly clamp, no. 212SA, is designed to serve as a retractor only. Because of its double bow and the closeness of the points of each jaw, this clamp must often be stabilized on the tooth, or it may rock mesiodistally during the procedure and damage the root. • For retraction for a facial Class 5 restoration (fig.22): - Dental impression compound (such as red or green compound) should be used under the bows of the clamp on the occlusal (or incisal) and lingual aspects of the teeth to provide stabilization. - The hole for the tooth that is to receive the no. 212SA retracting clamp should be offset facially from the line of teeth by approximately 1 mm. This provides for a greater width of interdental rubber dam septum so that, when the dam is displaced apically for access to the gingival margin of a Class 5 restoration, a water-tight seal will be maintained. - The double bow of the no. 212SA clamp precludes placement of two clamps on adjacent teeth. When two Class 5 restorations are to be placed on adjacent teeth, two no. 212SA clamps may be modified (fig.23); one of the bows of each clamp is cut off so that the remaining bow of one clamp extends to the right and the bow of the other extends to the left. If these clamps are stabilized with modeling compound, adjacent Class 5 restorations may be accomplished simultaneously. - Note that a no. 212SA clamp or a modified no. 212SA clamp may be used on one root of a molar that has a long clinical crown as well as on single-rooted teeth.

Clamp-Tooth contact (fig.23) • An important consideration when a clamp is selected is that only its jaw points contact the tooth; this gives four-point contact. No clamp jaw can ever be contoured to fit a tooth precisely, nor is there any reason for a clamp to fit precisely, because the dam, not the clamp, creates the seal. • Clamp Present 2 prongs which means that there are 4 prongs in a clamp and each prong rests on the mesial/distal line angle of the tooth to be clamped. A prong should not extend beyond the angle of the tooth otherwise it would interfere with the placement of a wedge or matrix band, also may cause gingival trauma& Difficulty in achieving complete seal around anchor tooth.

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Liquid dam (fig.31) • There are products currently available for sale called liquid dams. • They are easy-to-use light curing flowable resins capable of sealing quickly and effectively any gaps causing fluid leakage from and to oral cavity. • The liquid dam extension should not be restricted solely to covering the defect, but it should also include a tooth portion and the part of the sheet close to the gap. • If one of these sealing products be missing, a fluid composite (flow) can be used without acid-etching nor dentin-enamel adhesive.

Figure 1 rubber dam sheet with different colors.

Figure 3 recommended hole sizes

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Figure 2 rubber dam punch.

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Figure 5 No holes should be punched for missing teeth. Perforation placed at 10 mm to compensate for the missing tooth

Figure 4 incompletely punched holes will promote tearing of the dam during application or will affect the ability of the dam to seal.

Figure 7 Marking the position of the teeth directly in the mouth. Note that the rubber shall be stretched over the teeth and held in position, hile the center of the tooth is marked using a permanent marker.

Figure 6 Rubber dam template.

Figure 8 when applying the rubber dam to the maxillary teeth or mandibular third molars, the position of the upper central incisors should be stamped about 2.5 cm (1 inch) from the top edge of the rubber sheet.

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Figure 9 Perforations placed approximately 5 mm apart.

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Figure 10 Ostby frame a) plastic b) metal

Figure 11 rubber dam forceps. Figure 12 winged clamp components.

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Figure 13 (a&c) winged clamps (b&d) wingless clamps.

B

A

C

D

Figure 14 the main clamps used for molar isolation. A) W8A clamp. B) 8A clamp. C) B1 clamp. D) 27 clamp.

B

A

✓

Figure 15 main clamps used for premolar isolation. A) W2A clamp. B) 2A clamp.

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Figure 16 no. 212SA clamp.

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B A

Figure 18 clamps used for asymmetrical olars a) 12 A clamp. b) 13 A clamp.

Figure 17 clamps used for partially erupted molars A) W14A clamp. B) 14 A clamp.

A

B

Figure 19 clamps used for premolars with subgingival margins A) no. 1A clamp. B) no. W1A clamp.

Figure 20 clamp used for lower incisors and other small teeth. no 00 clamp.

Figure 23 clamp should contact tooth at mesial and distal extent of jaws. This 4 point contact provides stability or resistance to rotation or dislodgment for clamp.

Figure 21 Bland (left) and retentive (right) rubber dam clamps.

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Figure 22 butterfly clamp used for retraction for a facial Class 5 restoration

Figure 23 When two Class 5 restorations are to be placed on adjacent teeth, two no. 212SA clamps may be modified.

Figure 24 dental tape placed doubly through the contacts between the teeth.

Figure 26 anesthetic cartridge plunger tied around the distal tooth with floss.

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CHAPTER 3 Endodontic access cavity Contents Clinical determination of root canal configuration

Procedure of access cavity opening Root canal system anatomy

Access cavity requirements Complex root canal system

Access cavity objectives

Minimal invasive endodontics Errors in access cavity preparation

Challenging access preparations

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ROOT CANAL SYSTEM ANATOMY The entire space in the dentin where the pulp is housed is called the root canal system (pulp chamber &root canals). Bitewing radiographs and digital images offer the most accurate and distortion-free information on chamber anatomy in posterior teeth. (Figures 1-2)

Pulp chamber • It is located in the anatomic crown of the tooth. • It occupies the coronal portion of pulp cavity. • It reflects the external form of crown. Pulp chamber roof: The roof of pulp chamber consists of dentin covering the pulp chamber occlusally or incisally. Pulp chamber floor: The floor of the pulp chamber merges into the root canal at the orifices. Pulp horns: - Pulp horns are landmarks present occlusal to pulp chamber. - The occlusal extent of pulp horn corresponds to the height of contour in young permanent teeth. Canal orifice: they are funnel-shaped openings in the floor of pulp chamber leading into root canals.

Main Root canal • It is found in the anatomic root. It extends from canal orifice to the apical foramen. • Root canals begin as funnel shaped canal orifices which are generally at or apical to the cervical line. The canal ends at the apical foramen, which is the apical termination. • Nearly all root canals are curved, particularly in a faciolingual direction. A standard radiograph can only show curvatures in a mesiodistal direction and hence these curvatures may not be visible radiographically. • The number of root canals usually corresponds to the number of roots; however, many roots especially oval ones, can have multiple canals. • A thorough knowledge of the canal morphology in different teeth is essential for any dentist hoping to practice endodontics. The root canal system is complex and canal configurations may vary from case to case.

Classification of root canals (Vertucci’s classification): (fig. 3-10) • Type I: Single canal extends from pulp chamber to the apex. (1-1) • Type II: Two separate canals leave the pulp chamber and join short of the apex to form one canal. (2-1) • Type III – One canal leaves the pulp chamber and divides into two in the root; the two then merge to exit as one canal. (1-2-1) • Type IV – Two separate distinct canals extend from the pulp chamber to the apex. (2-2) • Type V – One canal leaves the pulp chamber and divides short of the apex into two separate distinct canals with separate apical foramina. (1-2) • Type VI – Two separate canals leave the pulp chamber, merge in the body of the root and redivide short of the apex to exit as two distinct canals. (2-1-2) • Type VII – One canal leaves the pulp chamber, divides and then rejoins in the body of the root, and finally redivides into two distinct canals short of apex. (1-2-1-2) • Type VIII – Three separate distinct canals extend from the pulp chamber to the apex. (3-3)

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Accessory root canals • Accessory canals are minute canals that extend in a horizontal, vertical, or lateral direction from the pulp space to the periodontium. • In 74% of cases they are found in the apical third of the root. • Pathologically they are significant because they serve as avenues for the passage of irritants, primarily from the pulp to the periodontium. Lateral root canal: (fig.11) •

It is a canal that is located at approximately right angles to main root canal.

•

It can be better detected by using two view radiographs at different angles.

Furcation canals: Accessory canals that are present in the bifurcation or trifurcation of multirooted teeth.

Apical delta • Apical deltas are multiple accessory canals that branch out from the main canal at or near the root apex (fig.12). • It is a triangular area of root surrounded by main canal, accessory canals and periradicular tissue. • It is the Y shaped branching of the root canal near the apex.

Pulpal Isthmus • It was also known as Corridor / Lateral interconnection or transverse anastomosis. • Isthmus is defined as narrow, ribbon-shaped communication between two root canals encompassing the pulp tissue. • Commonly isthmus is found between two canals present in one root like mesial root of mandibular molars. • It is a part of the root canal system and it is not a separate entity, so it should be cleaned, shaped and obturated as other root canals. Isthmus has shown to be main causative agent responsible for root canal failures because of the bacteria, which may get harbored in that area. So, it is always mandatory to clean, shape and fill the isthmus area. • Incidence: Mesial root of mandibular molar (80%) maxillary first molar (30–50%)

→

→

Maxillary premolar (52%) →

mesiobuccal root of

anterior teeth (15%).

Apical foramen & apical constriction (fig.13-14) Apical Constriction (Minor Diameter) • It is an apical part of root canal with the narrowest diameter short of apical foramina or radiographic apex. • Apical constriction acts as a natural stop for filling materials (it is the reference point clinicians use most often as the apical termination for shaping, cleaning and obturation). • Its Size and shape of foramen should always be maintained. Postoperative discomfort generally is greater when this area is violated by instruments or filling materials, and the healing process may be compromised.

Apical Foramen (Major Diameter) • It is the main apical opening on the surface of root canal through which blood vessels enter the canal. • Its diameter is almost double the apical constriction giving it a funnel shape appearance. • Apical foramen may not always be located at center of the apex. However, It may exit mesial, distal, buccal, or lingual (The apical foramen could be at the root apex or could deviate by up to 3 mm and open anywhere along the root surface short of the apex). • In general the apex to foramen distance is greater in posterior teeth and older teeth than in anterior and younger teeth.

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Factors Affecting Internal Anatomy Though internal anatomy (root canal system) of teeth reflects the tooth form, yet various environmental factors whether physiological or pathological affect its shape and size because of pulpal and dentinal reaction to them. These factors can be enlisted as: • Age: With advancing age, there is continued dentin formation causing regression in the shape and size of pulp cavity. Clinically, it may pose problems in locating the pulp chamber and canals (fig.15). • Irritants: Various irritants like caries, periodontal disease, attrition, abrasion, erosion, cavity preparation and other operative procedures may stimulate dentin formation at the base of tubules resulting in change in shape of pulp cavity. • Calcifications: Pulp stones or diffuse calcifications are usually present in chamber and the radicular pulp. These alter the internal anatomy of teeth and may make the process of canal location difficult.

Figure 1 digital radiograph helps to know morphology of teeth.

Figure 2 Bite-wing radiograph of the teeth in the maxillary right quadrant provides a clearer delineation of the pulpal morphology.

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Figure 3 Vertucci’s classification

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Figure 4 Single canal from pulp chamber to apex

Figure 6 single canal that divides into two that reunites in the apical third.

Figure 8 Single canal that has divided into two in lower first premolar.

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Figure 5 Two canals leaving from the chamber and merging to form a single canal short of apex

Figure 7 Two separate root canals in lower canine.

Figure 9 Two canals that have fused and then redivided.

Figure 10 Three mesial canals.

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Figure 11 Lateral incisor ith a canal loop and multiple lateral canals with associated lesions.

Figure 12 apical delta in distal root of lower 7.

Figure13 Morphology of the root apex. From its orifice the canal tapers to the apical constriction, or minor apical diameter, which generally is considered the narrowest part of the canal. From this point the canal widens as it exits the root at the apical foramen, or major apical diameter. The space between the minor and major apical diameters is funnel shaped.

Variations in apical morphology in root canal systems

Figure 14 Anatomy of the apical foramen. (3) Indicate apical constriction, or minor apical diameter, which generally is considered the narrowest part of the canal. From this point the canal widens as it exits the root at the apical foramen, or major apical diameter (2). The space between the minor and major apical diameters is funnel shaped (5). (1) Indicate anatomic apex which appear as radiographic apex on radiograph.

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Major anatomic components of the root canal system.

Figure 15 pulp space reduces with aging. A) Young pulp; B) old pulp.

ACCESS CAVITY OBJECTIVES The first step of root canal treatment is access cavity opening to provide the following objectives. The major objectives of the access openings include: • Removal of all caries, unsupported and undermined tooth structure and old restorations (fig.16). • Removal of the pulp chamber roof (fig.17). This helps in: - Complete removal of all coronal pulp tissue (vital or necrotic) to prevent interappointment flare-ups and post obturation reinfection & prevent discoloration of teeth because of remaining pulpal tissue. - Complete debridement of pulp chamber. - Improved visibility. - Locating canal orifices. - Permitting straight line access. - Locating all canals. • Unimpeded straight-line access of the instruments in the canals to the apical one third or the first curve (if present). This helps in: - Improved instrument control because of minimal instrument deflection and ease of instrumentation in the canal. - Improved obturation. -Decreased incidence of iatrogenic errors.

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Figure 52 different ultrasonic tips.

STEPS OF Access cavity opening Step 1: estimating depth of access cavity (fig.53-55). This is a measurement from the midlingual surface of anterior teeth and the occlusal surface of posterior teeth to the coronal portion of the pulp chamber. Measuring this distance on a dimensionally accurate pretreatment radiograph may serve as guide in limiting penetration and possibly preventing a perforation. The estimated depth of access is calculated. The estimated depth of access for teeth is similar in different tooth groups: • The maxillary central and lateral incisors average 5.5 mm for the central incisor and 5 mm for the lateral incisor. • The mandibular central and lateral incisors average 4.5 mm for the central incisor and 5 mm for the lateral incisor. • The maxillary canine averages 5.5 mm and the mandibular canine, with its longer clinical crown, averages 6 mm. • In maxillary furcated premolars, the average distance from the cusp buccal cusp tip to the roof of the chamber is 7 mm. • For maxillary molars the distance is 6 mm, and for the mandibular molars it is 6.5 mm. Note that with an average pulp chamber height of 2 mm, the access depth for most molars should not extend beyond 8 mm (the floor of the chamber).

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Step 2: removal of caries and defective restoration (fig.56). • Removal of restorative materials during access is often indicated knowing that following endodontic treatment, a new restoration will be placed. • Removal enhances visibility and may reveal undetected canals, caries, or coronal fractures.

Step 3: initial outline shape preparation (fig.57-61). Molars: (fig.57-59) • The mesial boundary for both the maxillary and mandibular molars is a line connecting the mesial cusp tips. Pulp chambers are rarely found mesial to this imaginary line. A good initial distal boundary for maxillary molars is the oblique ridge. For mandibular molars, the initial distal boundary is a line connecting the buccal and lingual grooves. For molars, the correct starting location is on the central groove halfway between the mesial and distal boundaries. • The bur is directed perpendicular to the occlusal table, and an initial outline shape is created at about half to three fourths its projected final size. Premolars: (fig.60) • The access cavity is ovoid and oriented buccolingually. • The bur is directed perpendicular to the occlusal table. Anteriors: (fig.61) • Initial penetration into enamel are made with the bur perpendicular to the lingual surface of the tooth. After penetration to the depth of 2 to 3 mm, the bur is reoriented to coincide with the long axis and lingual orientation of the root. • This outline form is made in the middle third of the lingual surface. It is triangular in incisors (base of triangle oriented incisally) & ovoid incisogingivally in canines.

Step 4: penetration of pulp chamber roof. The objective of this phase is to “penetrate” the pulp chamber by breaking through the roof with the bur. This phase is performed using a round diamond bur mounted on a high-speed handpiece. Diamond burs are preferred to tungsten burs, because they cut more smoothly and therefore vibrate less and are better tolerated by patients. The diameter of the bur depends on the tooth and pulp chamber being treated. During this phase, it may help to tilt the bur toward the pulp horn where the pulp chamber is wider. Drop-in sensation: • If the pulp chamber is wide enough, there is a sensation of “falling into a vacuum” when the roof is penetrated. If, however, the chamber is very narrow or completely absent because of the development of abundant calcifications, one should not expect this sensation (fig. 62-63). • If the drop-in effect is not felt at the estimated depth, a DG-16 explorer can be used to probe the depth of the access. Often a small opening into the chamber is present, or the dentin is very thin and the explorer penetrates into the chamber (Aggressive probing with a DG-16 explorer at any time during the penetration is encouraged to avoid perforation). Rather, one has to scoop out the access cavity to free the canal openings of obstructions. • If, in drilling a tooth with a completely calcified chamber, one waits for the sensation of falling into a vacuum, it will be too late when it does occur (this would signify perforation).

Step 5: complete removal of pulp chamber roof (deroofing). (Fig.64-66) • Once the pulp chamber has been penetrated, the remaining roof is removed by catching the end of a round bur under the lip of the dentin roof and cutting on the bur’s withdrawal stroke (brushing motion). Working in this manner enables the internal pulp anatomy to dictate the external outline form of the access opening & also, all the overhangings of dentin left behind in the preceding phase are removed.

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• Copious irrigation with sodium hypochlorite helps control any hemorrhage present. • This phase is better performed with a round bur mounted on a low-speed handpiece. Its diameter should be slightly smaller than that of the preceding bur, and it should have a long shaft for improved penetration and visibility.

Step 6: smoothening (fig.68). This phase aims to refine and smooth the cavosurface margins & finish off the work performed during the preceding two phases and to smooth the walls of the access cavity, so that the transition between the access cavity and the pulp chamber walls will be imperceptible to probing. Rough or irregular margins can contribute to coronal leakage through a permanent or temporary restoration. This phase requires a non-end-cutting diamond bur, also called self-guiding bur, mounted on a high-speed handpiece. The non-cutting head allows one to touch the chamber floor with the bur and at the same time precludes modification of its very important anatomy. With the appropriate angulation, the same bur is also useful for slightly flaring the most occlusal portion of the access cavity externally.

Step 7: location of root canal orifices (fig.69-70). • A sharp endodontic explorer is used to detect the canal orifice or to aggressively dislodge calcifications. When a canal is located, a small file or path-finding instrument (.06, .08, or .10 stainless steel file) is used to explore the canal and determine canal patency close to the apical foramen. This procedure is performed in the presence of irrigant or lubricant. • When difficulties occur with calcifications or extensive restorations, the operator may become disoriented. The discovery of one canal can serve as a reference in locating the remaining canals. A file can be inserted and an angled radiograph exposed to reveal which canal has been located. • Note that the canal orifices play an important role in determining the final extensions of the external access outline form.

Step 8: ensuring Straight-line access (coronal flaring of the root canal orifice & removal of lingual shoulder). Often, in an attempt to preserve tooth structure, the access openings are constricted and underprepared. This creates problems with locating canals and gaining straight-line access. Straight-line access to the canal orifice is the ideal goal. Preferably, a small intracanal file should reach the AF or the first point of canal curvature with no deflections. Removal of lingual shoulder: (fig 71-73) • Lingual shoulder is a shelf of dentin present in anterior teeth that extends from the cingulum to a point approximately 2 mm apical to the orifice. • Aim of removal of lingual shoulder: Its removal - Improves straight-line access. - Allows for more intimate contact of files with the canal’s walls for effective shaping and cleaning. - May often expose an extra orifice and canal. If the lingual shoulder has been removed and a file still binds on the incisal edge, the access cavity should be further extended incisally, until the file is not deflected. Thus, the final position of the incisal wall of the access cavity is determined by two factors: (1) complete removal of the pulp horns and (2) straight-line access. Removal of the cervical dentin bulges and orifice and coronal flaring: (fig.74-77)

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• The cervical bulges are shelves of dentin that frequently overhang orifices in posterior teeth, restricting access into root canals and accentuating existing canal curvatures. To facilitate the removal of calcifications, ultrasonics with specific tips, like CPR and ProUltra, are very useful. • During this process, the orifice is often concomitantly flared so that it is contiguous with all walls of the access preparation. The contemporary approach to flaring the orifice involves the use of rotary nickel-titanium (NiTi) orifice openers. • Some clinicians prefer the use of Gates-Glidden burs. When Gates-Glidden burs are used, the largest that can be placed passively 2 mm apical to the orifice is used first with gentle pressure.

Figure 53 Preoperative radiograph can help to note the position and depth of pulp chamber.

Figure 55 Calculation of the estimated depth of access for lower first premolar.

Figure 54 Calculation of the estimated depth of access for lower incisor.

Figure 56 Maxillary molar requiring root canal procedure. Removal of the amalgam reveals a vertical fracture on the palatal margin. Complete cleaning and shaping of the canals. Fracture lines are still visible, but no probings are present.

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Figure 57 Gain entry to pulp chamber with round bur.

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Figure 58 Mesial and distal boundary of a maxillary molar with the access starting location (X).

Figure 59 Mesial and distal boundary of a mandibular molar showing the access starting location (X). D, Distal; M, mesial; MB, mesiobuccal; ML, mesiolingual.

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Figure 60 A, In anterior teeth the starting location for the access cavity is the center of the anatomic crown on the lingual surface (X). B, Preliminary outline form for anterior teeth. The shape should mimic the expected final outline form, and the size should be half to three fourths the size of the final outline form. C, The angle of penetration for the preliminary outline form is perpendicular to the lingual surface. D, The angle of penetration for initial entry into the pulp chamber is nearly parallel to the long axis of the root.

Figure 62 Perforation of the floor at the orifice of the mesiobuccal canal is evident. If, in drilling a tooth with a completely calcified chamber, one aits for the sensation of falling into a vacuum, it will be too late when it does occur (this would signify perforation).

Figure 61 a, Starting location for access to the maxillary premolar (X). B, Initial outline form (dark area) and projected final outline form (dashed line). B, Buccal; L, lingual.

Figure 63 The penetration phase is completed. The diamond bur has broken through the pulp chamber roof.

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Figure 65 Once “drop in” into pulp chamber is obtained, bur is moved inside to outside.

Figure 64 Long-shafted round bur mounted on a low-speed handpiece. It is used for the enlargement phase. The diameter of the bur is always smaller than that of the round, diamond bur used in the preceding phase.

Figure 66 Removal of chamber roof.

Figure 67 deroofing is completed.

Figure 68 Non-end cutting diamond bur mounted on a highspeed handpiece, which is used for the finishing and flaring phase.

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Figure 69 Endo. Explorer used to locate canals.

Chapter 3. Endodontic access cavity

Figure 70 Canal orifices are located and identified ith an endodontic explorer. Small files are used to negotiate to the estimated working length.

Figure 73 A, The lingual ledge of dentin remains, deflecting the file toward the labial wall. As a result, portions of the lingual canal wall will not be shaped and cleaned. B, Removal of the lingual ledge results in straight-line access.

Figure 71 Lingual shoulder of the anterior tooth, extending from the cingulum to 2 mm apical to the orifice.

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Figure 72 Inadequate access preparation. The lingual shoulder was not removed, and incisal extension is incomplete. The file has begun to deviate from the canal in the apical region, creating a ledge.

Figure 74 A, The dashed lines show where dentin must be removed to achieve straight-line access. B, The access completed. C, The original canal (a) is modified using Gates Glidden burs to remove tooth structure at (B) and (C).

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Figure 75 A. Preoperative radiograph of the lower left first molar. Note the curvature of the coronal one third of the mesial root. B. The # 08 file, introduced in the mesiobuccal canal, indicates that the curvature is directed not only distally, as appreciated radiographically, but also lingually. C. The access cavity has been extended mesially and buccally, at the expense of the mesiobuccal cusp. D. This instrument, a # 20 file has straight-line access to the apical one third of the root canal.

Figure 76 A, Pulp roof/pulp horn removal. The round bur hooks under the lip of the pulp horn. B, The bur is rotated and withdrawn in an occlusal direction to remove the lip. C, Removal of a cervical dentin bulge. A Gates-Glidden bur is placed just apical to the orifice and withdrawn in a distoocclusal direction. D, A safety-tip tapered diamond bur is used to blend and funnel the axial wall from the cavosurface margin to the orifice.

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Figure 77 The completed access. The mesiobuccal canal is evident under the mesiobuccal cusp tip, the distobuccal canal is found opposite the buccal groove and slightly lingual to the main mesiobuccal canal, and the palatal canal is located under the mesiolingual cusp tip. Note the identification of the mesiolingual canal (arrow). Removal of the dentinal cornice that covers the mesiolingual canal to reveal the canal orifice.

Schematic representation of access cavity preparation for maxillary anterior teeth: (A) Initial point for entry of bur is middle of middle third of palatal surface; (B) keep round bur perpendicular to the long axis of the tooth; (C) Bur is directed 45° to the long axis of the tooth to penetrate the pulp chamber; (D) removal of chamber roof; (F) final access cavity shape of maxillary central incisor; (G) Access cavity shape of maxillary lateral incisor.

Schematic representation of access cavity preparation for mandibular anterior teeth (A) Initial point of entry for bur; (B) bur is directed perpendicular to long axis of the tooth; (C) direct the bur at 45° to long axis of the tooth; (D) Deroofing of the pulp chamber; (E) oval-shaped access cavity of mandibular incisor.

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A, In anterior teeth the starting location for the access cavity is the center of the anatomic crown on the lingual surface (X). B, Preliminary outline form for anterior teeth. The shape should mimic the expected final outline form, and the size should be half to three fourths the size of the final outline form. C, The angle of penetration for the preliminary outline form is perpendicular to the lingual surface. D, The angle of penetration for initial entry into the pulp chamber is nearly parallel to the long axis of the root. E, Completion of removal of the pulp chamber roof; a round carbide bur is used to engage the pulp horn, cutting on a lingual withdrawal stroke.

Schematic representation of access cavity preparation for premolars: (A) Pulp chamber is located in center of occlusal surface and pulp horns are located within the peaks of their cusps. (B) Penetrate the enamel using round bur and move it in buccolingual direction; (C) locate the canal orifice using endodontic explorer; (D) Move the bur inside to outside for removing roof of the pulp chamber; (E) Removal of coronal bulges for straight line access; (F) Final preparation with coronal flare and larger dimensions buccolingually.

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Schematic representation of access cavity preparation for maxillary molars: (A) Mesial boundary is a line joining the mesial cusps and distal boundary is the oblique ridge. Initial point of bur penetration is on the central groove midway between mesial and distal boundaries; (B) Penetrate the enamel with No. 4 round bur in the central groove directed palatally until “drop” into the pulp chamber is felt; (C) Explore the canal orifices with sharp endodontic explorer; (D) De-roof the pulp chamber moving bur from inside to outside; (E) Remove any cervical bulges or obstructions if present; (F) Final access cavity shows confluent walls of pulp chamber and occlusal surface; (G ) Occlusal view showing rhomboid shaped pulp chamber with acute mesiobuccal angle, obtuse distobuccal angle and palatal right angle.

Schematic representation of access cavity preparation for mandibular molars: (A) Initial point of entry of bur is central fossa midway between the mesial boundary (line joining the mesial cusp tips) and distal boundary (line joining buccal and the lingual grooves); (B) bur is penetrated in central fossa directed toward distal root; (C) explore canal orifices with sharp endodontic explorer; (D) Deroofing of pulp chamber; (E) Removal of coronal ledges or obstructions; (F) Final shape of access cavity with chamber walls flared occlusally.

Individual shapes of access cavity of different teeth. Shape of access cavity is determined by • Size of pulp chamber: In young patients, access preparation is wider than older ones (due to prominent pulp horns). • Shape of pulp chamber: Final outline form should reflect the shape of pulp chamber (It is triangular in incisors, ovoid incisogingivally in canines, ovoid buccolingually in premolars and trapezoidal or triangular in molars). • Number, position and curvature of the canal: It can lead to modified access preparation (to establish straight line access).

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Access Cavity for Maxillary molars (fig. 150-171) Maxillary First Molar Together with the lower first molar, this is the tooth that most frequently requires endodontic therapy. Outline form: Mesial boundary is a line joining the mesiobuccal and mesiolingual cusps and the distal boundary is the oblique ridge. The starting point of bur penetration is on the central groove midway between mesial and distal boundaries (directed palatally). The transverse or oblique ridge is left mostly intact (Pulp chamber lies mesial to oblique ridge). The outline form is triangular (if three canals present) or rhomboidal (if 4 canals present) and located in the mesial half of the tooth, with the base to the facial and the apex toward the palatal. The triangle has acute mesiobuccal angle, obtuse distobuccal angle and palatal right angles. Upper first molar has the largest pulp chamber of all teeth. Length: average length is 21 mm. Root canal configuration: Upper first molar usually has 3 roots (palatal, distobuccal & mesiobuccal roots). Each root has a canal named by its name except mesiobuccal root which is very broad in a buccolingual direction. Thus, usually (in 95% of the cases) contain small second canal [mesiopalatal canal orifice (commonly referred to as the MB2 canal)]. The palatal canal: • The lingual or palatal canal orifice generally exhibits the largest orifice and lies slightly distal to the mesiolingual cusp tip. • Palatal canal is the longest and has the largest diameter. • It curves in the apical third in buccal direction. Buccal curvature of palatal canal (56% of cases) may not be visible on radiographs, leading to procedural errors. Perforation of palatal root is commonly caused by assuming canal to be straight (clinical experience confirms that this root should always be considered curved, until proven otherwise). • The palatal canal frequently has lateral canals, especially in its apical one third. • Most common canal configuration in palatal root →

Vertucci Type I (single canal from orifice to apex).

• Note that because of close proximity of first molar roots (especially palatal root) to maxillary sinus, pulpal inflammation in this tooth can result in sinusitis. The mesiobuccal canal: • The mesiobuccal canal (MB1 canal) orifice lies slightly distal to the mesiobuccal cusp tip. • Mesiobuccal canal is the narrowest of the three canals. The mesiobuccal root- hence, the canal - is often curved distally. The degree of curvature varies from case to case. The distobuccal canal: • The distobuccal canal orifice lies distal and slightly lingual to the main mesiobuccal canal and is in line with the buccal groove. • Distobuccal canal orifice is not directly related to its cusp but more palatally and mesially displaced. • The distobuccal root is usually quite straight, but it may be slightly curved either mesially or distally. • Most common canal configuration in Distobuccal root →

Vertucci Type I (single canal from orifice to apex).

The MB2 canal: • The MB2 canal orifice is located 1 to 3 mm lingual to the main mesiobuccal canal (MB1 canal) and is slightly mesial to a line drawn from the mesiobuccal to the lingual or palatal canal.

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• The initial movement of the canal from the chamber is often not toward the apex but laterally toward the mesial (MB canal approached from the mesial direction while MB2 approached from distopalatal direction). • Removal of the coronal dentin (cornice) in this area permits exposure of the canal as it begins to move apically and facilitates negotiation. • Clinicians should always consider the presence of two canals in the mesiobuccal root of upper first molars, at least unless a careful examination has demonstrated the opposite. • MB2 can be very difficult to negotiate. In the first 1-3 mm the root canal is sharply angled in a mesial direction, and this is the reason why sometimes the tip of the file doesn’t progress apically more than a few millimeters and stops against the mesial wall. Therefore, before negotiating the canal, it is always necessary to open that angle, to remove from the mesial wall of the access cavity the shelf of dentin which is hiding the orifice of the canal, in order to get a straight-line access to the root canal itself. This can be done easily, safely and efficiently with ultrasonics and the specific tips, like CPR and ProUltra. • There are a number of strategies that, when used in combination, greatly increase the identification of the MB2 orifice and system. The most useful concepts and techniques include: - First of all, strongly believe that MB2 is always present! - Use of magnification, starting from loops and magnification glasses (2,5x – 4x) up to the operating microscope. - Start looking for MB2 only after MB1 is completely cleaned and shaped and, in theory, is ready for obturation. -Use a piezo-electric ultrasonic unit along with specially designed tips (CPR, ProUltra) to remove the dentinal shelf hiding the underlying orifice. - Flood the pulp chamber with a warm 5% solution of sodium hypochlorite to conduct the “champagne” or “bubble” test. The clinician can frequently visualize bubbles emanating from organic tissue, which is being digested in the extra canal, and rising towards the occlusal table. - Irrigate with 17% EDTA to remove the smear layer, then with pure alcohol and then air-dry with a Stropko irrigator fitted with a 27-gauge notched endodontic irrigating needle. - Use multiple obliquely angled radiographs (mesial shift in particular) both preoperatively and intraoperatively: the broader the root, the greater the likelihood of a second canal system. • The two canals in mesial root do not always have separate foramina; more often, they usually join together in a single foramen. Awareness of the existence of such a communication is important in determining the degree of preparation of the mesiopalatal canal. If the two canals join in a common foramen, lesser instrumental preparation of this canal can be justified. A gutta-percha cone will later be condensed in the merging mb2 canal so as to terminate against the cone inserted into the mesiobuccal canal, to which sealing of the common foramen is entrusted. With the aim of preventing excessive weakening of the root, which is quite thin and curved mesiodistally, and concave and thinner buccolingually, this is done so as not to risk stripping of the root or subsequent fracture. Most common canal configuration in Mesiobuccal root: - Vertucci Type II – 30% (two canals with common single foramen). - Vertucci Type IV – 29% (two canals with 2 separate foramina) - Vertucci Type I – 18% (single canal from orifice to apex). Note that the following configuration can also occur in upper first molar but it is extremely rare: • Mesiobuccal root can have three canals instead of common two canals (mb1 – mb2 – mb3). • Distobuccal root can have two canals instead of common single canal (Db1 – Db2). • Palatal root can have two canal instead of common single canal (main palatal and distopalatal canals). • Also, upper molar may only has 2 canals (buccal & palatal canals).

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Figure150 Angle of penetration toward the largest canal (palatal) in a maxillary molar.

Figure 151 Access cavity for a maxillary first molar

Figure 152 access cavity of upper first molar showing 4 canals.

Figure 153 A. Photograph of an upper right first molar, seen mesially. Note the curvature of the palatal root, which faces buccally. B. Postoperative radiograph of the upper right first molar. Note the sinuosity of the palatal canal. C. The palatal canal of this upper molar has a large lateral canal directed distally.

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Figure 154 Note the considerable degree of distal curvature of the mesiobuccal canal.

Figure 155 Magnification helps in better visualization of canal anatomy.

Figure 156 A. A photograph taken at 12x reveals the orifice of the mesiobuccal canal and related groove. A dentinal shelf frequently hides the underlying orifice of the mesiopalatal canal. B. After establishing a straight-line access, an appropriately selected ultrasonic tip easily, rapidly and safely eliminated the dentine shelf and exposes the more palatal mesiopalatal orifice

Figure 158 the mb2 canal as it leaves the pulp chamber. Canals that are not negotiable but detected by an explorer may move laterally before proceeding apically.

Figure 157 allowing sodium hypochlorite (NaOCl) to remain in the pulp chamber may help locate a calcified root canal orifice. Tiny bubbles may appear in the solution, indicating the position of the orifice. This is best observed through magnification.

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Figure 159 note the location of mb2.

Figure 160 Cross section of the mesiobuccal root of an upper first molar: the root is concave on the distal aspect, both canals are pretty close to the bifurcation, and the root is thinner in a palatal direction.

Figure 161 The mesiopalatal canal is joining the mesiobuccal with a 90° angle. In such a case, to go to the same working length coming from the mesiopalatal canal is very dangerous and useless!

Figure 162 Postoperative radiograph of an upper right first molar with mesiobuccal and mesiopalatal canals joining together at a common foramen.

Figure 163 A. Postoperative radiograph of the upper right first molar with a mesiopalatal canal with an independent foramen. B. In this patient, both the upper right first and second molars reveal a mesiopalatal canal with an independent foramen.

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Figure 164 note that Mb2 is not found in this case despite troughing of the mesial groove.

Figure 165 A. The access cavity of this extracted molar shows three canals in the mesiobuccal root. B. Careful examination of the access cavity of this upper molar shows the presence of a third opening near the orifice of the mesiopalatal canal. C. The three canals have been cleaned and shaped. D. Postoperative radiograph: MB2 and MB3 were joining together.

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Figure 166 Access cavity of an upper first molar. The mesiobuccal root has three canals. B. The postoperative radiograph shows three canals with independent foramina.

Figure 167 an upper right first molar with five canals, two of which are in the distobuccal root. The five canals don’t seem to have independent foramina.

Figure 168 Two canals in both buccal roots with a common foramen in each root.

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Figure 169 an upper left first molar with two palatal canals in two distinct roots: P, palatal canal; MB, mesiobuccal canal; DB, distobuccal canal; DP, distopalatal canal.

Figure 170 an upper right first molar has two orifices, one palatal and one buccal.

Figure 171 Treatment process using a dental operating microscope and X-ray images. A: Preoperative periapical radiograph of teeth indicates the existence of decay in the distal part of the tooth; B-C: Only one buccal canal orifice and palatal canal orifice can be detected under the visual field of the dental operating microscope; D: Radiograph of master cone; E: Post-obturation periapical radiograph; F: Two root canals are obturated by gutta-percha.

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CHAPTER 4 working length determination Contents Definition and importance of working length Anatomic considerations in working length determination

Coronal reference point Pre-length determination procedures

Methods of working length determination

Apical end point

Determination of working length in teeth with open apices 178

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DEFINITION AND IMPORTANCE OF WORKING LENGTH Working length in endodontics is defined as “the length from a coronal reference point (the point from which the measurement is to be made coronally) to the point at which the canal preparation and obturation should terminate (apical end point)” (fig.1).

The importance of working length determination It is very important to establish the length (distance from the apex) at which canal preparation and subsequent obturation are to be terminated. Correct working length determination is a critical factor within the endodontic triad of success → the cleaning, shaping, and obturation cannot be accomplished accurately unless the working length is determined correctly. Why accurate working length determination is very important? Because this will: • Confine the instrumentation to the canal system (within dentin). • Create and maintain an apical stop or seat at the minor constriction. • Prevent under instrumentation (Working shorter than actual length) that could cause: - Incomplete instrumentation, incomplete cleaning and dead space (leave tissue and debris in the apical segment). (fig.2) - Working to shorter lengths may lead to the accumulation and retention of debris, which in turn may result in apical blockage (fig.3). If the path to the apex is blocked, Procedural errors such as apical perforations, ledge formation and fractured instruments can occur. Such obstacles (which consist of collagen fibers, dentin mud, and most importantly, residual microbes) in apical canal areas are a major cause of persistent or recurrent apical periodontitis or post treatment disease. - Persistent pain and discomfort (interappointment flare-ups) • Prevent over instrumentation (Working beyond the apical terminus) that could cause: - Widening of the apical foramen (Apical perforation that will cause prolonged healing and lower success rate time because of incomplete regeneration of cementum, periodontal ligament, and alveolar bone) - patient discomfort - Violation of apical periodontium & Pushing debris and chemicals to apical region → damage periapical tissue or potentially cause an infection or cyst development from the placement of irritating materials beyond the apex (failed endodontic treatment). (Fig.4)

ANATOMIC CONSIDERATIONS IN DETERMINING THE WORKING LENGTH Many anatomic features should be considered during working length determination. These include: • Anatomic apex • Radiographic apex • Average teeth length • Apical constriction • Cemento-dentinal junction (CDJ) • Apical foramen • Radiographic apex

Anatomic apex (fig.5) It is the real apex of the tooth, appreciated after extraction of the tooth

Radiographic apex (fig.5) • It is the apex of the root tip as appreciated on the radiograph (the anatomical end of the root as seen on the radiograph).

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180 • The radiographic apex is also known as the apical vertex. • Its location can vary due to root morphology and distortion of the radiographic image.

Average teeth length • It is the length measured from incisal or occlusal surface of a tooth to its anatomic apex. • Anatomic studies and clinical experience suggest that typically teeth are 19 to 25 mm long. Most clinical

crowns are approximately 10 mm long, and most roots range from 9 to 15 mm in length. Roots, therefore, can be divided into thirds that are 3 to 5 mm long (fig.6). • Average teeth length helps dentists to determine the estimated working length (table 1-2).

Apical Constriction (Minor Diameter) (fig.7-9) • It is an apical part of root canal with the narrowest diameter short of apical foramina or radiographic apex. • Apical constriction acts as a natural stop for filling materials (it is the reference point clinicians use

most often as the apical termination for shaping, cleaning and obturation [apical end point]). • Its Size and shape of foramen should always be maintained. Postoperative discomfort generally is greater when this area is violated by instruments or filling materials, and the healing process may be compromised.

Cemento-dentinal junction (CDJ) (fig.8) • At this point, the pulp tissue ends, and the endodontium yields to the periodontium. The canal walls are no

longer formed of dentin, but cementum. The pulp therefore ends at the CDJ and must be removed up to this point. • It is the region where the cementum and dentin are united. • Theoretically, it is the actual point that endodontic treatment should stop at. The term ‘theoretically’ is applied here because the CDJ is a histological site and it can only be detected in extracted teeth following sectioning; in the clinical situation it is impossible to identify its position. In addition, the CDJ is not a constant or consistent feature, for example, the extension of the cementum into the root canal can vary. Therefore, it is not an ideal landmark to use clinically as the end-point for root canal preparation and filling. • Apical constriction and CDJ were viewed as a single area for a long time and located at an average of 1 mm from the root apex. However, it is not always necessary that CDJ always coincide with apical constriction.

Apical foramen (Major Diameter) (fig.7-9) • It is the main apical opening on the surface of root canal through which blood vessels enter the canal. • Its diameter is almost double the apical constriction giving it a funnel shape appearance. • Apical foramen may not always be located at center of the apex. However, It may exit mesial, distal, buccal,

or lingual (The apical foramen could be at the root apex or could deviate by up to 3 mm and open anywhere along the root surface short of the apex) (fig.10-11): -In general the apex to foramen distance is greater in posterior teeth and older teeth than in anterior and younger teeth. -It is demonstrated that in 48% of cases the apical foramen is at the anatomic apex (and therefore localizable radiographically), while in 40.9% of cases the emergence of the canal is mesial or distal (and therefore still radiographically identifiable). In only 11.1% of cases was the foramen on the buccal or lingual surface of the root (and therefore not radiographically visible).

Summary to apical tooth anatomy (fig.12) • The shape of this apical portion is considered to be an inverted cone; its base being located at the major

apical foramen. The apex of the inverted cone is the minor foramen that is often thought to coincide with the apical constriction regarded as being at or near the cemento-dentinal junction (CDJ).

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• In other words, the most apical portion of the root canal system narrows from the opening of the major foramen, which is within cementum, to a constriction (minor foramen) before widening out in the main canal to produce an hour-glass shape.

Figure 1 Working length is distance from coronal reference point to a point where instrumentation and obturation should end

Figure 2 Working to shorter lengths results in failed root canal treatment in lower second molar.

Figure 3 Working to shorter lengths may lead to the accumulation and retention of debris, which in turn may result in apical blockage.

Figure 4 failed root canal treatment due to orking beyond apex.

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Apical foramen

Anatomic apex

Figure 5 anatomical and radiographic apex.

Table 1 average anatomical lengths of upper teeth.

Upper central incisor

22.5 mm

Upper lateral incisor

21.5 mm

Upper canine

27 mm (longest tooth)

Upper first premolar

21.5 mm. Buccal canal is usually longer than palatal canal.

Upper second premolar

21 mm. Palatal canal is usually longer than buccal canal.

Upper first molar

21 mm. Usually palatal canal is the longest canal then the distobuccal canal then the mesiobuccal canal and the shortest the MB 2 canal.

Upper second molar

20 mm. Here, usually the mesiobuccal canal is longer than the distobuccal canal.

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Table 1 average anatomic lengths of lower teeth. lower central incisor

21 mm

lower lateral incisor

22.5 mm

lower canine

25.5 mm

lower first premolar

21.5 mm

lower second premolar

22.5 mm

lower first molar

21 mm.

lower second molar

20 mm.

Figure 6 most roots range from 9 to 15 mm in length. Roots, therefore, can be divided into thirds that are 3 to 5 mm long.

Figure 7 Microscopic view of molar root tooth apex, apical constriction (AC), apical foramen (AF), and anatomical apex (AA)

Figure 8 CDJ can only be detected in extracted teeth following sectioning; in the clinical situation it is impossible to identify its position.

Figure 9 Minor and major apical diameter.

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Figure 10 apical foramen could deviate by up to 3 mm from anatomic apex.

Figure 11 (a) Major apical foramen (apical opening) with protruding instruments; (b) root apex.

Figure 12 Idealized anatomy of apical portion of root (a) major apical foramen, (b) minor apical foramen (apical constriction) that may be coincident with the cemento-dentinal junction (CDJ), (c) cementum, (d) dentine and (e) root apex.

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METHODS OF WORKING LENGTH DETERMINATION Radiographic method Radiographs are probably the most common and oldest method used for determining working length.

Requirements The following items are essential to perform this procedure: • Good, undistorted, preoperative radiographs showing the total length and all roots of the involved tooth. • Adequate coronal access to all canals. • An endodontic millimeter ruler. • Working knowledge of the average length of all of the teeth. • Stable reference point on the tooth. • A file with a rubber stopper.

A

C

B

D

F

E

Radiographic method requirements. A) Good, undistorted, preoperative radiographs showing the total length and all roots of the involved tooth. B) Adequate coronal access to all canals. C) Working knowledge of the average length of all of the teeth. D) Stable reference point on the tooth. E) An endodontic millimeter ruler. F) A small file with a rubber stopper.

Technique Step 1 → determination of file length (fig.30) • Measure the tooth length on the preoperative radiograph. • Reduce 1 mm as ‘SAFETY ALLOWANCE’ for possible image distortion (this is the tentative working length [estimated working length]). • Set the endodontic ruler at this tentative working length. Set the file at this length. Step 2 → determination of file size (fig.31) • Insert the adjusted file into the canal till reference point. But stop, if pain is felt. Then take a new periapical radiograph.

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• Note that the largest file to bind is the file chosen to be inserted to this estimated length because a file that is loose in the canal may be displaced during film exposure or forced beyond the apex if the patient bites down inadvertently. • To obtain an accurate measurement, the minimum size of the working length should be a No. 20 file. With files smaller than No. 20, it is difficult to interpret the location of the file tip on the working length film or digital image. Step 3 → radiographic interpretation of file Method A: (fig.32-38) • On the radiograph, measure the difference between the end of the instrument and the end of the root. • Add or subtract this amount to the tentative working length depending on whether the exploring instrument is short or beyond the apex. If the correction is greater than 3 mm, a second working length radiograph should be made with the file placed at the adjusted length. • From this adjusted length, subtract 1 mm as ‘safety factor’ to Confirm with the apex (in necrotic cases subtract 0.5 to 1 mm short of the radiographic apex and 1 to 2 mm in cases involving irreversible pulpitis). • If a definite periapical radiolucency is present with radiographic indication of apical resorption, working length need to be modified. Because root resorption can alter the apical constriction, it was suggested to subtract an extra 0.5 mm from the working length (1.5 mm short of radiographic apex) in teeth exhibiting radiographic evidence of apical resorption. Note that if there is evidence of both bone and root resorption, reduce 2mm from radiographic apex. Method B: (fig.39) Actual length of tooth (working length) can be obtained by mathematical Method as following: 𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀𝐀 𝐀𝐀𝐀𝐀𝐥𝐥 𝐥 𝐥 𝐥 𝐥 𝐥𝐀𝐀𝐀𝐀𝐥𝐥 𝐥 𝐨𝐨𝐨𝐨𝐨𝐨𝐨𝐨 𝐀𝐀𝐀𝐀𝐥𝐥 𝐥 𝐥 𝐥 𝐀𝐀𝐀𝐀𝐨𝐨𝐨𝐨𝐨𝐨𝐨𝐨𝐀𝐀𝐀𝐀𝐥𝐥 𝐥 (𝐀𝐀𝐀𝐀𝐥 𝐥 𝐮𝐮𝐮𝐮𝐨𝐨𝐨𝐨𝐮𝐮𝐮𝐮𝐥𝐥 ) 𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂 𝒍 𝒍 𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒍𝒍 𝒍𝒂𝒂𝒂𝒂𝒍𝒍 𝒍 𝒐𝒐𝒐𝒐𝒐𝒐𝒐𝒐 𝒂𝒂𝒂𝒂𝒐𝒐𝒐𝒐𝒐𝒐𝒐𝒐𝒂𝒂𝒂𝒂𝒍𝒍 𝒍 𝒐𝒐𝒐𝒐𝒂𝒂𝒂𝒂 𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒐𝒐𝒐𝒐𝒍𝒍 𝒍𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒍𝒍 𝒍 (𝒌𝒌 𝒌𝒂 𝒂 𝒐 𝒐 𝒌𝒌𝒌𝒌𝒂𝒂𝒂𝒂)

=

𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒍𝒍𝒍 𝒍 𝒍 𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒍𝒍 𝒍𝒂𝒂𝒂𝒂𝒍𝒍𝒍 𝒐𝒐𝒐𝒐𝒐𝒐𝒐𝒐 𝒓𝒓𝒓𝒓𝒂𝒂𝒂𝒂𝒊𝒊𝒊 𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒓𝒓𝒓𝒓 𝒐𝒐𝒐𝒐𝒓 𝒓𝒍 𝒂𝒂𝒂𝒂(𝒌𝒌𝒌𝒌𝒂𝒂𝒂𝒂𝒐𝒐𝒐𝒐𝒌𝒌𝒌𝒌𝒂𝒂𝒂𝒂) 𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂 𝒍 𝒍 𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒍𝒍𝒍 𝒂𝒂𝒂𝒂𝒍𝒍 𝒍 𝒐𝒐𝒐𝒐𝒐𝒐𝒐𝒐 𝒓𝒓𝒓𝒓𝒂𝒂𝒂𝒂𝒊𝒊 𝒊𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒓𝒓𝒓𝒓 𝒐𝒐𝒐𝒐𝒓𝒓𝒓𝒓𝒍𝒍𝒍 𝒂𝒂𝒂𝒂 𝒐𝒐𝒐𝒐𝒂𝒂𝒂𝒂 𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒐𝒐𝒐𝒐𝒍𝒍 𝒍𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒍𝒍 𝒍 (𝒌𝒌 𝒌𝒂 𝒂 𝒐 𝒐 𝒌𝒌𝒌𝒌𝒂𝒂𝒂𝒂)

In the formula, three variables are known and by applying the formula, fourth variable, that is, the actual length of tooth can be calculated. Clinical Tips • When two superimposed canals are present (e.g., buccal and palatal canals of maxillary premolar, mesiobuccal canals of mesiobuccal root of maxillary first molar, buccal and lingual canals of lower anteriors and lower premolars if present or mesial canals of mandibular molar), one should take the following steps: - Take two individual radiographs with instrument placed in each canal (but this expose the patient to additional x-ray dose). (fig.40) - Apply SLOB rule; expose tooth from mesial or distal horizontal angle; canal which moves to same direction is lingual, whereas canal that moves to opposite direction is buccal. Note that mesial angles are recommended for premolars and maxillary molars. Distal angulation is recommended for the mandibular incisors and molars. (fig.41) - Insert two different instruments, e.g., K file in one canal, H file in other canal, and take radiograph at different angulations. (fig.42) • In curved canals, canal length is reconfirmed because final working length may shorten up to 1 mm as canal is straightened out by instrumentation. (fig.43-44) • Panoramic radiographs are not advocated for calculating tentative working length because gross magnification of 13–28% employed in OPG may lead to errors in calculation of accurate readings. Limitations of conventional radiography • It is only a two-dimensional representation of a three-dimensional structure, which is subject to error, and some anatomical landmarks could be superimposed on each other. For example, the superimposition of the

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196 zygomatic arch over the roots of maxillary molars or mandibular torus over the roots of mandibular premolars will impede the proper location of the radiographic apex on those teeth. (fig.45-46) • Dense bone can also make the visualization of root canal files difficult by obscuring the apex. Newer digital

radiography systems might overcome this problem by image manipulation. • The apical foramen can even be located as far as 3 mm short of the radiographic apex, thus increasing

chances of over instrumentation. Furthermore, the apical foramen and the radiographic apex do not always coincide. When the apical foramen exits to the sides of the root or in a buccolingual direction, it becomes difficult to view on the radiograph.(fig.47-49)

Figure 31 step (2) the largest file to bind is the file chosen to be inserted to this estimated length Figure 30 step (1) determination of estimated working length.

Figure 32 working length determination.

Figure 33 the actual working length should be equal to (estimated working length from radiograph - 0.5:1 mm).

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Figure 34 sometimes the radiograph shows that the file does not reach the ideal length. This discrepancy is added to estimated WL to reach final working length.

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Figure 35 the file is beyond the apex. This distance indicated by the arrow should be subtracted from the estimated length to determine the working length.

Figure 36 in this case the estimated working length is equal to the actual working length.

Figure 37 If the correction is greater than 3 mm, a second working length radiograph should be made with the file placed at the adjusted length.

Figure 38 modification of working length in case of root or bone resorption.

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198 A

B

C

Figure 39 A) apparent length of tooth on radiograph. B) Apparent length of inserted file on radiograph. C) actual length of inserted file.

Figure 41 here, k file is inserted in mesiolingual canal whereas h file is inserted in mesiobuccal canal. Now the two mesial canals can be differentiated on radiograph.

Figure 40 also, you can Take two individual radiographs with instrument placed in each canal. here, the file is in the mesiobuccal canal.

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Figure 42 SLOB rule. (a) Superimposed files over each other in buccal and palatal canals. (b) The same image taken from mesial angle to see the files separately. Note that the mesial file is in the palatal canal whereas the distal file is in the buccal canal [same lingual, opposite buccal].

Figure 43 Canal straightening; during the therapy, especially in case of curved canals, shaping causes the straightening of the canal. In the picture you can note that the first WL determination was 19 mm, but during the procedure it was double checked in order to avoid over-instrumentation: in fact, it was 18.5 mm

Figure 44 in curved canals, working length can change during Mechanical Preparation Stages.

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Figure 47 The radiographic appearance that the instruments have could be A: if the foramen is at the anatomic apex and therefore at the radiographic apex, which means that the canal was straight. B: if the foramen opens mesially or distally, because the canal curved in that direction. C: if the foramen opens buccally or palatally/lingually, because the canal curved in that direction.

A

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Figure 48 A) radiographic terminus of extracted lower first premolar appears as visibly short (the tooth is radiographed in usual buccolingual projection). B) The tooth radiographed in a mesio-distal projection. Here, the instrument is at the foramen, but it opens buccally on the root surface and would not be identifiable with a normal radiographic projection. C) Note how much the file would need to extrude from the apex to be at the radiographic apex. What would it mean in a case like this to remain 0.5 mm short of the radiographic apex?

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Figure 49 The radiograph illustrates very well how absurd it would be to use the radiographic apex (A) as a reference point, especially when this has nothing to do with the real site of the apical foramen (B), the real root canal terminus and the real terminus of our preparation and obturation.

Figure 46 Superimposition of the Torus Mandibularis over the roots of mandibular premolars.

Figure 45 Superimposition of the zygomatic arch over the roots of maxillary molars.

Non-radiographic method Traditional methods Symptom method Patient’s response to pain is probably the oldest method used. This method is based on patient’s response to pain → File is inserted till the patient feels pain. It is very unreliable in clinical practice because of the following: • This technique is also extremely subjective owing to the individual pain threshold of each patient. • Also, this method depend on state of the tooth →

In the cases of canal with necrotic pulp, instrument can

pass beyond apical constriction and in the case of vital or inflamed pulp, pain may occur several mm before periapex is crossed by the instrument • It is impossible to apply this method when local anesthesia is performed. Tactile method

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CHAPTER 5 Root canal instrumentation contents Objectives of mechanical preparation of root canals

Techniques for shaping root canals Important procedures during any shaping technique

Requirements of shaping procedures

Instruments used for shaping root canals

Errors during shaping root canals

Mechanical preparation in special cases

Motions used for shaping root canals

Final evaluation of root canal preparation

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IMPORTANT PROCEDURES DURING ANY SHAPING TECHNIQUE Initial pulp extirpation • It is recommended to withdrawn the pulp tissue all in one piece as this will allows the clinician to quickly remove the majority of the pulp with the minimum of effort and time because: - This speeds cleaning and shaping. - It allows deeper initial penetration of irrigation - It most importantly prevents "balling up" of the canal contents at the apex which is one of the most common reasons for canal transportation (both external and internal) as well as the inability to reach the apex after previously obtaining an accurate. - Also, this procedure eliminates the future pain in cases of hot teeth after the intra-pulpal anesthesia disappear. • This procedure can be done only in teeth with vital pulp or with ischemic necrotic pulps (e.g. pulp necrosis due to cutting of blood supply due to, for example, trauma) but this is not feasible in teeth with liquefaction necrosis (e.g. necrosis develop as final sequelae to irreversible pulpitis). • Before performing this procedure it is preferable to irrigate the orifice with NaOCl to remove bleeding & Suction to allow visibility of the orifice (fig.32). Then, the pulp tissue can be removed in one piece by either barbed broach or k files as in the following:

Using barbed broach (fig.33) • The basic description of this instrument and how to use it correctly is mentioned earlier in this chapter • First, the correct size must be chosen (it must be wide enough to engage the pulp effectively, but not so wide as to touch the canal walls. If you are unsure, always select a smaller size. You can always move up a size if the pulp does not engage). • Then, it is inserted in the canal. Once it has hooked the pulp filament around itself for two-thirds of its length, the apical third of the pulp will usually become dislodged easily and sectioned without having to thread the instrument to the apex (The broach is introduced for two-thirds of the length of the root canal. The instrument is rotated at least 180°, and it is then extracted).

Using k file or reamer • A K-type instrument with as large a diameter as possible is introduced into the canal to the predetermined apical level of instrumentation. • The instrument is then rotated as much as possible in contact with the root canal wall in an effort to sever the pulp at this level. • If this is successful, the pulp may come out in one piece and a pulp stump with a clean-cut wound is left behind in the root canal. • If it is not successful, the pulp tissue will instead be removed in bits and pieces during the subsequent instrumentation of the canal. Figure 32 before performing pulp xtirpation procedure it is preferable to irrigate the orifice with NaOCl to remove bleeding & Suction to allow visibility of the orifices.

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Figure 33 pulp tissue removed in one piece using barbed broach.

MAINTAINING THE PATENCY OF THE APICAL FORAMEN • A patency file is a small K-file (usually a size #10 or #15) that is passively extended just through the apical foramen. • Taking into consideration the rich collateral blood supply and the elevated healing potential of the attachment apparatus, it is illogical to think that extending a small file passively and accurately beyond the apex will compromise the final result or cause an irreversible condition for the patient. • Rules: - The file used for maintaining the patency should be equal to or smaller than k-file size #15. - If the # 10 file does not descend to the same working length, it must not be forced, screwed, or pushed into the canal. It must be replaced by the next file of smaller size (#8 or #6), so that the path can be better prepared. The second file must also be used with small, back-and-forth movements (watch winding motion) with excursions of about 0.5-2 mm, and the user’s hand must rest securely on the neighboring teeth. - Great care should be taken if the apex of the root(s) appears to be in close proximity to important anatomical structures, for example the inferior alveolar nerve in case of lower molars, mental nerves in case of lower premolars or maxillary sinus in case of upper molars. - The file should not be inserted any further through the constriction than 0.5– 1.0 mm to avoid pushing infected debris into the periapical tissues or potentially damaging any nearby important anatomical structures. • Benefits: - Remove accumulated debris, to help maintain WL, and thereby to translate into greater clinical success (note that the accumulated infected debris at root apex is common cause of failure of root canal treatment). - Also, the patency of the foramen will permit the accumulation of any exudate (which may form in the apical tissues in spite of careful shaping) within the canal rather than among the fibers of the periodontal ligament. This prevents the development of periodontitis postoperatively.

Vital and necrotic canals are negotiated to length and patency is established and maintained to promote the preparation objectives.

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Apical patency aims at keeping the foramen free of debris by intentionally extruding the file tip slightly beyond the apical foramen. Note that the circumference of the foramen is still covered ith debris that could not be removed by use of a patency file instead should be removed using copious irrigation.

A patency file is worked beyond the foramen to make sure that the canal has been cleared, and to allow the irrigating solution to flow into this noninstrumented area.

A patency file just protruding through the apical foramen. Note that no enlargement of the foramen is present.

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B

A) During instrumentation, plugs of dentine chips and debris can accumulate apically, which may prevent adequate shaping, irrigation and potentially deviate instrument tips, resulting in ledges. B) Taking a size ISO 8 or 10 file regularly 0.5 mm beyond the apex helps prevent this.

Preliminary enlargement Preliminary Enlargement of Coronal part of root canal (coronal flaring) (fig.34) • The extension of an access cavity into the coronal-most portion of the root canal has been called “coronal flaring” but may be more appropriately described as orifice modification (Optimal orifice and coronal third shaping is only possible when straight-line access is prepared first). • If a canal is constricted, mineralized, or difficult to access, directed enlargement of the coronal portion prior to any deep entry into the root canal is beneficial. • This canal modification should be preceded by a scouting step, in which a small (e.g., size #10) K-file is passively placed several millimeters into the root canal. • Benefits: - Allow files unimpeded access to the apical one third (fig.35) (If the orifice and coronal third is not enlarged correctly, compromises will occur in subsequent apical treatment). - Give the clinician better tactile control in directing small, adequately precurved negotiating files. - Provide early access of disinfecting irrigation solutions. - Prevention of pushing contaminated coronal debris apically. Methods: coronal flaring can be performed by either H-file, gates-glidden drills or rotary Ni-Ti files. • Gates-glidden (GG) method (fig.36-38): - The sequence of instruments employed in this first phase of preparation would typically be 06, 08, or 10 files for the initial penetration; followed by copious irrigation; recapitulation with 06 or 08 and continued passive enlargement with10 through 30 or 35 files; irrigation; and recapitulation with 10 file. - Gates Glidden drills can now be introduced. The use of this instrument without manual preliminary enlargement, however, often results in ledging. Because these instruments are not flexible, they should only be used in a straight line. - Note that working the gates glidden instrument in a static or stationary position will create eccentricities in the preparation rapidly. - The instrument is carried to the body of the system using a push-pull motion and allowed to work apically until it meets with resistance. - The smallest drill that engages tooth structure is chosen as the initial drill and is followed by the next largest size.

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- The drills should be used sequentially and in a step-back modality and the cutting emphasis is on the outer walls of curvature. The sequence, as well as the frequency with which each drill is used, can vary with the complexity of anatomy of each system. - This phase of preparation would typically include 1, 2, 3, 4, 5, or 6 G-type drills, followed by copious irrigation and recapitulation with the initial file. • Rotary Ni-Ti files method (fig.39): - Rotary Ni-Ti orifice opener is used for coronal flaring. This is a rotary file with greater taper and small tip size (e.g. 20 or 25/.6, .8, .10 or .12) [the role of file tip here is only guiding the file into the canal] - When using this file, regardless of the type, similar actions are needed to maintain tactile control as well as to prevent the instrument from “screwing in” and leading to possible fracture. The clinician should assure an excellent tactile grip on the orifice opener and only insert the file as far as desired based on the anatomy. It is unproductive to force the file to any predetermined depth. Rather, the file should be inserted passively to the point of resistance. Such a tactile motion usually takes about 3 seconds. The file can be inserted again as needed to move further apically. After every insertion of the file, the canal should be irrigated and a stainless steel hand file, for example a #6 or #8 Mani hand K file inserted into the canal to assure patency beyond the level of the orifice opener insertion. - This method is very beneficial in cases involving difficult entry into the root canal system (as in narrow mesiobuccal canals in upper molars) where gates Glidden drills cannot be used. - Note that using this method you can go with the instrument beyond middle third whereas if GG drills used, this cannot be achieved. • H-file method (fig.40): -H-files of different sizes can be used in sequence in filing motion. - Hand files will require more time and are stiff, thereby increasing the risk of altering the natural canal anatomy, but hand instruments can be effective at this level of the canal - This should be done carefully to avoid iatrogenic errors as ledges, perforations, file separation etc.

A

B

C

D

Figure 34 A) The access cavity without any early coronal enlargement. .B to D) Selective coronal enlargement of the orifices during root canal preparation that aims to cut only the amount of dentin needed to allow enlarging files to reach the apex safely without excessive stress. The amount of coronal interference removed is related to the root canal anatomy and the instruments used.

Figure 35 the preliminary enlargement will permit unimpeded access to the apical third and the foramen can be negotiated.

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Figure 36 GG method for coronal flaring.

Figure 37 coronal flaring using GG.

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Figure 39 coronal flaring using orifice opener. Figure 38 A maxillary first molar following straight-line access with the Gates-Glidden drills.

A

B

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D

Figure 40 Progressive enlargement at same length using a push-pull filing motion (a) File with size 10 to 16–18 mm or beginning of the curve; (b) file using Hedström size 15 to same length; (c) Hedström file size 20 to 16–18 mm; (d) Hedström file size 25 to 16–18 mm.

Preliminary Enlargement of whole root canal (glide path) • The file that has reached the apical foramen has already formed a so-called glide path (fig.41). This term relates to securing an open pathway to the canal terminus that subsequent engine-driven instruments can follow. • Nickel-titanium rotaries should not be placed into an unexplored canal, but rather should follow hand instruments, which establish a glide path that then can be followed by rotaries.

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• The presence of a glide path is essential for the predictable use of rotary instruments since it minimizes the so-called screw-in or threading-in effect (taper lock) and risk of torsional failure. It has been considered that taper lock may occur if the canal cross section is smaller than the tip of the instrument; in that regard, a glide path reduces the contact area between subsequent shaping instruments and the canal wall, consequently the torsional loads induced by shaping rotary instruments are lower. • It is advocated to explore and shape a root canal at least to a #15 size instrument before the use of a rotary NiTi instrument to full WL to create a glide path for the safe advancement of the rotary shaping instrument tip (fig.42). • The presence of an appropriate glide path is indicated by the fact that a straight size #15 K-file can passively and smoothly travel to WL with long in-and-out movements. • Classically, a glide path was created and secured with K-file sizes #10 and #15 used in watch-winding or balanced-force motion. However, recently NiTi rotary instruments with small tip diameter have been designed specifically to simplify the process after a size #10 K-file has reached WL (fig.43). The creation of a rotary glide path has demonstrated better preservation of the canal anatomy with fewer shaping aberrations and has shown a less incidence of postoperative pain. However, some studies have also reported acceptable performance of manual instruments for glide path preparation.

Figure 42 after confirmation of a glide path with a No. 20 K-file, rotary file can now be used.

Figure 41 glide path.

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Figure 43 Diagrammatic representation of a mandibular molar tooth undergoing reproducible glide path preparation using nickel-titanium rotary Pathfiles. Note (a) Pathfile #1 (purple) has an ISO 13 tip size. (b) Pathfile #2 (white) has an ISO 16 tip size. (c) Pathfile #3 (yellow) has an ISO 19 tip size

ANTICURVATURE FILING METHOD • This method was proposed for the preparation of curved canals, but in practice the technique should always be performed in preparing the canals of the molars, either upper or lower, particularly in the mesial canals of the lower molars and the mesiobuccal canals of the upper molars, whose roots always present a buccolingual con-cavity on their distal surface. This means that these canals are closer to the distal surface of the respective root than they appear to be radiographically. • In these cases, a circumferential filing should obviously be avoided, since it would as a certain consequence lead to excessive thinning of the root or even to perforation from stripping in the area of the bifurcation. A wall thinned in this way could also fracture vertically during the condensation of the obturating material or later, on mastication. • The anticurvature filing method safeguards against such risks, in addition to providing straighter access to the apical third of the canal. • The anticurvature filing method consists of working the endodontic instruments constantly against the external wall of the curve (The goal of the anticurvature filing method is to prepare the canal, especially at the expense of the thickest portion of the root, staying far away from the area of the curve and from the bifurcation; in other words, from that area in which the root is dangerously thinner). • In round but more or less straight roots, in which the canal is in a central position, the wall thicknesses are approximately the same, buccolingually and mesiodistally. Consequently, the circumferential filing, which requires concentric enlargement of the original canal, can be used confidently.

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A. Cross section of the mesial root of a lower first molar. Note the different thicknesses of the dentin mesial and distal to the two canals. B. Cross section of the mesiobuccal root of an upper first molar. Note the closeness of the two canals with respect to the area of the bifurcation. Note that green arrows point to safety zones whereas red arrows point to danger zones.

In applying the anticurvature filing method, the instruments must be worked in the direction indicated by the arrows.

The furcal region of molars at the level of the curvature (danger zone) is a common site for stripping perforation.

Strip perforation of mesial root of lower molar due to ignorance of anticurvature shaping.

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Failure of root canal treatment due to strip perforation.

Note the furcal view of mesial root of extracted tooth.

Recapitulation • Recapitulation is important regardless of the technique selected. • It is accomplished by taking a small file to the working length to loosen accumulated debris and then flushing it with 1 to 2 mL of irrigant. • Recapitulation is performed between each successive enlarging instrument, regardless of the cleaning and shaping technique. • During recapitulation the canal walls are not planed and the canal is not enlarged. Note that there is difference between recapitulation step and the step of maintaining the patency of apical foramen because: • The main aim of recapitulation is maintaining full working length while the main aim of maintaining the patency step is to ensure that the apical foramen not blocked with dentin debris that may be cause of failure of the treatment. • In the step of maintaining the patency, the file size used is not larger than #15 file while in recapitulation this is not a rule (a file smaller than the already instrumenting file is used). • In the step of maintaining the patency, the file must cross apical foramen to ensure its patency while in recapitulation step it is enough to insert the file to the working length (not cross apical foramen).

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After each instrumentation step, recapitulation is performed using small manual file.

Recapitulation to the working length with a small file. A, Dentin debris may shorten the working length and plug the canal at and beyond the working length. B, Recapitulation with a small file will aid in maintaining the full working length

TECHNIQUES FOR SHAPING ROOT CANAL Basic cleaning and shaping strategies for root canal preparation can be categorized as apical coronal techniques, coronal apical techniques and hybrid techniques: • Apical-coronal techniques: here, the apical third of the root canal is prepared first then middle and coronal thirds in sequence. • Coronal-apical techniques: here, the coronal third of the root canal is prepared first then middle and apical thirds in sequence. • Hybrid techniques: All basic techniques described so far may be combined into a hybrid technique to eliminate or reduce the shortcomings of individual techniques and instruments.

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Different techniques for cleaning and shaping root canal system. a) Apical coronal technique b) corono-apical technique, c) hybrid technique.

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Management of narrow (calcified) canals The most common way in which calcified canals will first be identified is from the pre-op radiograph (For teeth with more than one canal it is therefore recommended to have more than one pre-op radiograph at different angulations) (fig.57).

Protocol for preparation of calcified canals: Locate and visualize the canals: • For this, enhanced magnification and illumination is an absolute must (If you can’t see it, you can’t treat it → Without sufficient visualization and illumination into that little endodontic access, the clinician will likely be spending too much time looking for a calcified canal and/or may not be able to locate it at all . Worse yet, you’ll be more likely to perforate the tooth in the process of drilling and looking for a very narrow canal). • The keys followed to locate the orifices of calcified canals is mentioned before in chapter 3 page 151. Initial canal negotiation using stainless steel hand files: • When trying to manage a calcified canal, the use of very small SS hand files, such as .06, .08, and .10 files, is often a must. However, traditional SS K-files of these sizes will most likely not be able to negotiate calcified and curved canals. They tend to easily unwind, buckle, or—worse yet—fracture. While we worry about NiTi file separation, we must remember that SS files can also separate, especially in tight canals. So I strongly recommend the use of stiff hand files, such as C-files (Dentsply Sirona Endodontics) or EndoSequence Stiff K-Files (Brasseler USA). Consider a #6 hand file that is .06 in diameter but is about as stiff as a traditional .08 or .10 SS hand file. That is how C-files are characterized. • As a general guideline, the calcification process occurs in a coronoapical direction, so if the operator is able to get the initial canal captured, an instrument tends to progress more easily as it advances at the directions apical. • Intra-operative radiograph is beneficial for correct localization of the calcified canal. (fig.58) • A small NiTi rotary instrument designed for coronal flaring can be used to taper the orifice and remove any constriction. The clinician can return to a small ultrasonic tip to penetrate further into the canal. Gates-Glidden burs will not be beneficial here as they have a non-cutting tip. Continue glide path preparation using rotary Ni-Ti files: • With improved metallurgy and engineering, endodontic manufacturers have recently introduced NiTi endodontic files that are specifically designed to manage calcified canals and create or enhance glide paths. These files are able to do what SS files attempt to do, but these instruments do it better and more efficiently. • The following are examples of narrow and flexible NiTi files (fig.59): - XPlorer (Clinical Research/CLINICIAN’S CHOICE Dental Products): This is one of the first glide path NiTi files to come to market. These files are available in .01 and .02 tapers (the same narrow taper as SS hand files). - ESX Scout (Brasseler USA): These are rotary NiTi files, size .15 at the tip, available in .02 and .04 tapers - Pathfiles (Dentsply Sirona Endodontics): These narrow (.02 taper) and flexible NiTi files come in 3 sizes (.13, .16, and .19). The increase in file sizes (from .13 to .16 to .19) makes it easier to go up in file size versus standard ISO file sizes. - WaveOne Gold Glider (Dentsply Sirona Endodontics): This is one of the newest glide path NiTi files on the market. They are size .15 and .02 taper at the tip and have an increasing taper coronally. The file can be pre-curved, which may be helpful in accessing posterior teeth. Studies have shown the benefits of reciprocation, such as that of WaveOne, when it comes to fracture resistance and the ability to follow canal curvatures compared to traditional rotary NiTi filing.

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Canal lubrication throughout the instrumentation: As we focus on tiny canals, we may forget to keep them lubricated. Forgetting to do so will increase the chance of file separation or apical blockage. So, please lubricate and re-lubricate the canals throughout the procedure. Biomechanical Preparation: • Most of the cleaning is done in such cases by the mechanical action of the file, and the irrigation is used only to remove debris and smear layer. • Coronal flaring in a crown-down fashion is preferred. • Incremental instrumentation is achieved by creating new increments between the established widths by cutting off a portion of the file tip, thus making it slightly wider in diameter. For example, if a 1 mm segment is clipped from a size 10 file, the instrument becomes a size 12, by trimming sizes 15, 20 and 25, instruments of sizes 17, 22 and 27 respectively can be created. In extremely sclerotic canals, only 0.5 mm segments are trimmed, increasing the instrument width by 0.01mm and making a size 10 into a size 11, etc. Because cutting the shaft imparts a flat tip, a metal nail file is used to smooth the end and reestablish a bevel after the removal of any segment. • This procedure will take time and patience, and the temptation to try to drill a canal into the root should be resisted as this invariably leads to deviation and potential root perforation.

Figure 57 importance of preoperative radiograph for identification of calcified canals.

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Figure 58 In a tooth with an extensively calcified canal (A) a check radiograph with a probe in the base of the ity will provide guidance for instrument progression. (B) A later radiograph onfirms that the file is in the root canal.

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Figure 59 rotary Ni-Ti glide path file systems. A) XPlorer (Clinical Research/CLINICIAN’S CHOICE Dental Products) NiTi rotary files. B) ESX Scout (Brasseler USA) NiTi rotary files. C) Pathfiles (Dentsply Sirona) NiTi rotary files. D) a WaveOne Gold Glider (Dentsply Sirona) NiTi reciprocating file (pre-curved).

Oval canals • There is a high prevalence of root canals with oval- and long oval-shaped cross sections. They reported an even higher prevalence in distal roots of mandibular molars, mandibular incisors, and maxillary second premolars (fig.60). • Radiographically, from the standard, buccolingual projection, the root canal cross section appears round. The mesiodistal projection and horizontal section of the root more accurately depict the non-round, ovalshaped configuration (fig.61). • They often present with buccal and lingual surface extensions, which may be difficult, if not impossible to access and debride by conventional mechanical preparation techniques. • Considering such canals [have a larger buccal-lingual dimension (oval)] as two separate entities during preparation seemed to be beneficial. • Rotary file systems, which are highly effective in cases of simple root canals with a round cross-section, cannot be expected to perform as effectively in the case of flat-oval canals. The mechanical action of the rotating files is unlikely to affect the entire circumference of the root canal. Naturally, a rotating file can produce a round canal at best; therefore a strategy must be devised for adequately shaping oval canals without overly weakening radicular structure (fig.62-63). Uninstrumented buccal and/or lingual recesses (“fins”) are consequently a common finding. Attempts to overcome this challenge in oval canals by “brushing” or circumferential filing with rotary files are not effective: a high percentage of the canal wall is still untouched by the files. This result may be explained by the tendency of the flexible rotary NiTi files to remain centered in the canal (also, these instruments tend to penetrate along the path of least resistance and the file tip cannot be directed exactly into one direction by manipulation of the handpiece). An additional circumferential filing with more rigid hand stainless-steel (SS) files may help to improve, to a certain extent, the mechanical preparation of such flat-oval canals. • Under-preparation, leaving lateral extensions of the root canal walls untouched, and over-preparation, increasing the risk of strip-perforations (fig.64), are among the major problems. Using hand instruments in a circumferential filing technique is recommended in order to adequately enlarge and clean both lateral extensions without over-preparation in the middle of the root canal. • This lack of effective cleaning may be explained in part by the packing of dentin particles and debris into uninstrumented recesses that is caused by rotary files. This packing may make the pulp tissue or biofilm in these recesses inaccessible to the action of sodium hypochlorite. It should be kept in mind that the dentin particles are actually packed into either pulp tissue or bacterial biofilm that is present in the isthmus, thus forming a composite structure that is difficult to remove. A high percentage of these packed particles cannot be removed by syringe and needle irrigation with either sodium hypochlorite or EDTA. Furthermore, even

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passive ultrasonic irrigation failed to remove all such packed radiopaque material; 50% of it was still retained in the isthmus even when this effective irrigation method was used. • One study has demonstrated that passive ultrasonic irrigation with sodium hypochlorite and a final rinse with chlorhexidine facilitates disinfection of E. faecalis‐infected oval canals.

Figure 60 Long oval root canal ystem in a maxillary premolar.

Figure 61 Two-dimensional radiographs of a human mandibular premolar from buccolingual (left) and mesiodistal (middle) projections, and an axial view of the same premolar, depicting the oval-shaped root canal (right).

Figure 62 Because of their round cutting in cross sections, traditional NiTi rotary and reciprocating files are unable to clean the oval areas of the root canal adequately. The top shows underprepared anal while the bottom shows over prepared canal.

Figure 63 Postoperative image showing uninstrumented canal extensions

Figure 64 Overpreparation (red arrow) on the inner concave side of the root canal may result in a strip-perforation.

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After mechanical preparation with conventional nickel-titanium rotary instruments, non-round root canals often appear as keyholes (A-B) or dumbbells (C). These instruments fail to contact a significant proportion of root canal surfaces, which remain virtually unchanged.

Management of C-shaped canals • These canals are severe examples of flat-oval canal morphology and have high variability. (fig.65) • Melton’s Classification of C-shaped canals: 1. Category I: Continuous uninterrupted C-shaped canal running from the pulp chamber to the apex defines a C-shaped outline without any separation or division. (fig.66) 2. Category II: The semicolon-shaped (;) orifice in which dentine separates a main C-shaped canal from one mesial distinct canal. (fig.67) 3.

Category III: With two or more discrete and separate canals → subdivided into the following: - Subdivision I: C-shaped orifice in the coronal third that divides into two or more discrete and separate canals that join apically. (fig.68) - Subdivision II: C-shaped orifice in the coronal third that divides into two or more discrete and separate canals in the midroot to the apex. (fig.69) - Subdivision III: C-shaped orifice that divides into two or more discrete and separate canals in the coronal third to the apex. (fig.70)

• Fan et al proposed a modified classification by adding two more categories: - Category IV represents a very wide single, round or oval, canal in the cross-section (all in one). (fig.71) - Category V where no canal lumen can be observed (seen near the apex only). • When the orifice is continuous C-shaped or arced, number of canals can vary from one to three, when the orifice is oval, number of canals can be one or two and when orifice is round, one canal is suspected. • Continuous C shaped canal [MB-D] should be negotiated with three or more initial precurved K files No 8 and 10, which decreases the chance of missing canal. • Irregular areas in a C-shaped canal that may house soft-tissue remnants or infected debris may escape thorough cleaning or filling and may be a source of bleeding and severe pain. • To gain access to irregularities in the C-shaped canal system, coronal third is prepared using GG drills. Care should be taken to avoid perforation in C1 (continuous C type) and C2 (semicolon type) type canals. In narrow, interconnecting isthmus areas, GG drills should not be used and cleaning should be using a #25 instrument (the isthmuses should not be instrumented with files larger than size 25 in order to prevent strip perforations). • Anticurvature filing is recommended to avoid danger zones. Caution should be taken to prevent strip perforation during cleaning and shaping of mandibular premolars, which has thin dentinal walls in the radicular groove area. • Cleaning of C-shaped canal with rotary instruments should be assisted by ultrasonic activation of irrigation. Extreme care should be taken to avoid perforation in the C-shaped roots with the narrow isthmus when ultrasonics is used. • C-shaped canals is preferred to be hand instrumented because their anatomy is unpredictable.

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Figure 65 C-shaped root canal, the shape of the canal is observed as the letter “C.”

Figure 66 Category I

Figure 67 Category II

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Figure 68 Category III Subdivision I

Figure 69 Category III Subdivision II

Figure 70 Category III Subdivision III.

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Figure 71 Category IV

Summary of c- shaped classification.

Canals with large apical foramen (open apex) • A minor constriction may not actually be present in the following cases: - Young permanent teeth (fig.72). - External root resorption at apex due to severe chronic periapical inflammation (granuloma or cyst) (fig.73). - Iatrogenic damage during instrumentation of the canal (over instrumentation) (fig.74). • Creation of an apical stop may be impossible if the apical foramen is already very large. An apical seat (ledge) is attempted but with care (fig.75).

Young permanent teeth Young permanent teeth are often characterized by wide canals with wide apical foramen and thin walls. The diameter of the canal may exceed 1.5 mm. The instrumentation procedure for such canals differs substantially from that of mature teeth. Aggressive filing, which may reduce the thickness of the remaining radicular dentin, is contraindicated as it may predispose the teeth to root fracture. The challenge in cleaning such root canals is to remove all tissue debris and bacterial biofilm without compromising the integrity of the tooth. Due to the diverging canal walls, rotary instrumentation with flexible NiTi files is ineffective and cleaning of the canal is largely dependent on the action of the irrigant. For more details about management of immature teeth see chapter 10.

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Figure 72 wide apical foramen in young permanent molar.

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Figure 73 severe apical root resorption that result in loss of apical constriction.

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Figure 75 creation of apical seat. A) Prepared canal with wide apical foramen. B) Creation of apical seat by instrumentation 1 mm beyond working length. C) Apical seat prepared.

Figure 74 Accidental over-instrumentation, resulting in a loss of apical constriction

Root canals with Lateral canals • Lateral canals are mostly inaccessible to most current cleaning and shaping methods. As far as vital cases are concerned, such canals may not present a major problem. Nevertheless, in infected cases, the pulp tissue in lateral canals may also become necrotic and contain bacterial biofilm that may persist and potentially lead to endodontic failure. • The ability of irrigants such as sodium hypochlorite to penetrate into these lateral canals may be limited by: - The high surface tension of this solution. - The presence of debris and smear layer “plugs” that tend to block the entrance of these lateral canals. • Instrumentation and irrigant activation procedures that effectively eliminate debris and the smear layer are therefore likely to result in optimum cleaning of these lateral canals (can be ensured by radiographic appearance of lateral canals filled with sealer or even gutta-percha).

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CHAPTER 6 Root canal disinfection Contents

Main irrigants in endodontics

Importance of root canal irrigation

Lubricants in endodontics

Intra-canal medication

Activation of irrigation

Rules for irrigation

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IMPORTANCE OF ROOT CANAL IRRIGATION • Physical debris cannot be completely removed from the root canal system by mechanical instrumentation alone. That is why, today informed clinicians agree that ‘files shape and irrigants clean’ (areas inaccessible to endodontic Instruments depend only on irrigation) (fig.1-2). • The purpose of cleaning is to remove all intracanal material, whether of pulpal origin, vital or necrotic, or microorganisms, from the root canal system.

Irrigation step is very important in root canal treatment as it provides 3 critical functions:

Washing Removal of pulp tissue& dissolving intracanal contents • If the vital pulp tissue cannot be removed by barbed broach or small k file or the pulp condition is necrosis or degeneration, it must be dissolved using irrigants. • The irrigant should have the ability to dissolve infected organic and non-organic portions contained in root canal especially if their location is inaccessible to mechanical instrumentation (fig.3).

Flushing out debris (fig.4) • Debris is defined as dentin chips or residual vital or necrotic pulp tissue attached to the root canal wall. • The irrigant keeps the dentinal debris in suspension, preventing blockage of the apical portion of the canal. If no irrigant used, this will lead easily to canal blockage by dentin mud.

Opening of dentinal tubules by removal of the smear layer (fig.5-6) • Smear layer was defined as a surface film of debris retained on dentin of canal walls after instrumentation with either rotary instruments or endodontic files. • It consists of dentin particles, remnants of the vital or necrotic pulp tissue, bacterial components, and retained irrigants. • Most researchers emphasize the importance of removing the smear layer for the following reasons: - The smear layer prevents sealer contact with the canal wall, permitting leakage. - Microorganisms in the dentinal tubules may use the smear layer as a substrate for sustained growth. - The presence of a smear layer may also interfere with the action and effectiveness of root canal irrigants and interappointment medications. • Irrigation procedure is the only able to remove this layer.

Antimicrobial action (destruction of microorganisms) • Many irrigants have antimicrobial properties with varying degrees (bactericidal, bacteriostatic or both). • This characteristic is very important to prevent failure of root canal treatment.

Lubrication & Wetting of canal walls • The root canal instruments must never be used in dry canals, but rather should always be completely immersed in irrigating solutions that completely fill the root canal and pulp chamber. • Endodontic instrumentation without the help of an irrigant is also extremely dangerous. This can lead to fracture of the instrument as a result of the greater force required for its use, the lack of lubrication, and possible engagement of the instrument in the dry canal. • Also, insertion of an endodontic file in dry canal without lubricant will lead eventually to canal blockage and loss of working length (described later).

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Figure 1 Root canal system is complicated with fins, webs and anastomosis. It can be cleaned by effective use of an irrigating solution.

Figure 4 sodium hypochlorite dissolving action.

Figure 5 Smear layer on the canal wall occluding the dentinal tubules.

Figure 2 apical third of mesial root of lower molar. Note the complexity of root canal system that cannot be cleaned without irrigation.

Figure 3 Irrigation helps in loosening of debris and removing it from the canal preventing its blockage.

Figure 6 Smear layer removed with 17% EDTA showing open and patent dentinal tubules.

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LUBRICANTS IN ENDODONTICS Either solutions or gel or paste lubricants can be used for lubrication of endodontic instruments in root canals.

Solutions Any irrigating solution (e.g. NaOCl, EDTA solution, saline….) will provide wetting and lubrication of canal walls. When nickel-titanium rotary techniques are used, aqueous solutions (e.g., NaOCl), rather than paste lubricants, should always be present in the root canal to reduce torque.

Gel &paste lubricants (Chelators) The most common chelator used in endodontics is EDTA gel. It is indicated to open calcified canals with hand files. However, when one is making a path in dentin softened by the chelator, it is difficult to know whether one is advancing into the original root canal or whether a new canal is being “made”, that is a false canal. Also, its use is particularly indicated in the initial negotiation of vital cases, as it advantageously promotes the emulsification of organic tissue and facilitates the negotiation of the root canal: • Collagen is a major constituent of vital pulp tissue and can be inadvertently packed into a glue-like mass that contributes to iatrogenic blockages. • In vital cases, attempting to negotiate any portion of a canal with a # 10 file without the aid of a chelator can be very risky. When the instrument is withdrawn, the vital tissue tends to collapse and readhere to itself. The next larger instrument is not able to pierce through the pulp tissue to progress in an apical direction, and pushes the glue-like mass, blocking the canal. • A chelator discourages this tissue phenomenon and accelerates emulsification by leaving a favorable pilot hole that facilitates the introduction of the sequentially larger instrument. Another advantage is that the contact between hypochlorite and the gel chelating agent causes the formation of rising oxygen that kills the anaerobic bacteria and with the. Effervescence that occurs aids the removal of dentin filings. The debris therefore remains in suspension avoiding the formation of excessive smear layer and consequently dentin plugs.

Figure 7 Examples of ethylenediaminetetracetic (EDTA) acid Pastes.

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Figure 8 note that ledge (A), false canal (B) or even perforation (C) can occur due to negotiation of root canal with EDTA gel without care.

The placing of an EDTA gel on an endodontic file before placement in a canal.

MAIN IRRIGANTS IN ENDODONTICS Presently, no solution can be regarded as optimal. However, the combined use of selected irrigation products dramatically contributes to the successful treatment outcomes. There are 3 main irrigants usually used for root canal irrigation that include: • Sodium hypochlorite • Chlorhexidine solution • EDTA solution

0.5:5.25 % Sodium hypochlorite (NaOCl) Benefits NaOCl is the most commonly used irrigating solution because: • It has antibacterial property. • It has the ability to dissolve necrotic tissue, vital pulp tissue, and organic components of dentin and biofilms in a fast manner. (Fig.9) • It has Low surface tension. As sodium hypochlorite has a low surface tension: - It can reach areas beyond the reach of instruments, lateral canals, resorptions and depressions of the endodontic space, including the apical delta. - it is not necessary to generate great force to inject sodium hypochlorite into the root canal to make it reach the proximity of the apex. Hypochlorite passively reaches deeply into the canal, with the help of the endodontic instruments. (fig.10) • It is very cheap.

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Figure 11 Device for heating syringes filled with irrigation solution (e.g. Sodium hypochlorite) before use.

Figure 10 Hypochlorite passively reaches deeply into the canal, with the help of the endodontic instruments.

Figure 12 to warm NaOCl, syringes filled with NaOCl are placed in 60–70°C (140°F) water bath.

Figure 13 Commerciallyvailable bleach (Clorox) is 5.25% sodium hypochlorite.

Figure 15 Forceful irrigation can cause periapical extrusion of sodium hypochlorite solution.

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Figure 16 NaOCl accident showing haemorrhage.

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Figure 14 sodium hypochlorite accident.

Figure 17 A sodium hypochlorite accident during treatment of the maxillary left central incisor. Extensive edema occurred in the upper lip and was accompanied by severe pain.

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Saline and its use It is biocompatible in nature. No adverse reaction even if extruded periapically because osmotic pressure of normal saline is same as that of the blood. The use of saline as a sole irrigant is not considered, as normal solutions are ineffective as antimicrobial agents and will not dissolve organic material. It is used only for: • Flushing out the debris • Separation between different solutions. • Wetting & lubrication of root canals. • It can also be used as final rinse for root canals to remove any chemical irrigant left after root canal preparation to diminish postoperative pain. • Used to make mix with calcium hydroxide powder to be used as intracanal medication.

Normal saline.

RULES FOR IRRIGATION The following rules should be followed: • Use rubber dam while irrigating to avoid swallowing of irrigants, and irritation to mucosa. • For the solution to be mechanically effective in removing all the particles, it has to reach the apex, create a current (force), and carry the particles away. • The irrigants must be renewed constantly after the use of every rotary instrument and the pulp chamber space performs the function of an irrigant reservoir. It is recommended that the minimum volume of irrigant be 1 or 2 ml each time (fig.18). • Volume of irrigant is more important than concentration of irrigant. • To improve the efficiency of irrigation at the apical level suggested using the patency file, (thin file to control the patency of the canal) before each irrigation, with the aim of preventing possible organization of the debris, which under irrigant pressure can become compacted and form dentin plugs. • In passive syringe irrigation, the actual exchange of irrigant is restricted to 1 to 1.5 mm apical to the needle tip, with fluid dynamics taking place near the needle outlet. Placement close to WL is required to guarantee fluid exchange at the apical portion of the canal, but close control of insertion depth is required to avoid extrusion. • The needle should: - Be fine of either 25 or 28 gauge. - Be monojet, side-vented, safe-ended needles (Note that Needle with bevel is not preferred for irrigation because if gets lodged into the canal, there is risk of forcing irrigant past the apex). - Be precurved (bent at 45 degrees) to aid its passage into the canal.

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- Reach the maximum working depth without any obstruction from the canal walls. - If beveled open-ended needle used, it should be kept 3 mm short of working length (the length adjusted with rubber stopper [fig.19]) while if side-vented closed-ended needle used, it should be placed at 0–1 mm short of WL. - In case of large canals, tip of needle should be introduced until resistance is felt, then withdraw the needle 2–3 mm away from that point and irrigate the canal passively. - Not allowed to bind radicular dentin while irrigating (Needle should never be wedged into the canal and should allow an adequate backflow). [fig.21-22]) • As was mentioned previously, the irrigation must be carried out without excessive pressure and with continuous movement of the needle up and down, to reduce to a minimum the risk of pressure extrusion of irrigant. → Use index finger instead of thumb to press plunger while delivery of irrigant to decrease force of irrigation (fig.20) (Solution should be introduced slowly and passively into the canal). • To remove the excess fluid, either the aspirating syringe or 2 × 2 inches folded gauge pad is placed near the chamber. To further dry the canal, remove the residual solution with paper point. • In case of small canals, deposit the solution in pulp chamber. Then file carries the solution into the canal. Capillary action of narrow canal will stain the solution.

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Figure 18 A. The irrigating solution present in the pulp chamber appears turbid after an instrument has worked in the root canal. This is caused by the suspension of dentin mud. B. The irrigating solution has been rejuvenated between the use of one endodontic instrument and the next, to prevent the suspension of dentin mud from becoming too concentrated, which ould increase the risk of blocking the canal.

Figure 19 The needle should be bended at fixed length for easier use, and a silicone stop should be used. Colour-coded needles and syringes are useful for different irrigants.

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Figure 20 Use index finger instead of thumb to press plunger while delivery of irrigant to decrease force of irrigation

Various endodontic irrigating needles

Figure 22 Loose fitting needle providing space for optimal flow of irrigant.

Figure 21 Needle binding encourages extrusion of irrigant

A sterile gauge piece is placed near access opening to absorb excess irrigating solution and to check the debris from root canal.

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Needle with notched tip allows back flow of solution and does not create pressure in periapical area.

Needle with bevel.

Monojet endodontic needle.

ACTIVATION (AGITATION) OF IRRIGATION • Irrigants should be agitated (activated) during and after completion of mechanical preparation of the root canal. Agitation may be achieved manually, sonically, or ultrasonically. • The aims of agitation are to: - Promote irrigant exchange apically (Overcome the Vapor lock in the apical region). - Circulate the irrigant to the uninstrumented portions of the root canal system (apical delta, isthmi, lateral canals… etc) [fig.23]. - Improve irrigant properties (e.g. NaOCl action is improved when activation is used). - Stir up debris, therefore reducing blockages. - Aid smear layer removal. • Note/ apical vapor lock: it is a phenomenon that occurs when air bubbles entrapped in the apical part of the root canal during syringe irrigation and totally block irrigant penetration in that area. This can be overcome by irrigant activation (fig.24).

Manual method (fig.25-27) • A well-matching GP master cone whose taper is slightly less than the taper of the canal is selected. A snug fit is sought after at the working length. • Then 1 ml is trimmed at the tip of the cone in order to get tug-back 1 ml shorter than the canal terminus. • After suction of the primary irrigant NaOCl, the canal is filled with 1 ml of EDTA delivered with a 30 gauge needle. • Manual agitation of the master cone is started with an up and down motion and a 2 mm amplitude at a frequency of 100 strokes during approximately 1 min. After that, 1 ml of EDTA is delivered with the irrigating needle to flush out debris. EDTA is then suctioned to eliminate any residual chelating action. • The canal is flushed with 1 ml of NaOCl, and the same protocol is repeated using 50 in and out strokes during 30 s. A final flush is performed with 3 ml of NaOCl.

Ultrasonic method • The irrigant is delivered to the root canal by a syringe needle. The irrigant is then activated with the use of an ultrasonically oscillating instrument. • Ultrasonic handpieces pass ultrasonic waves to an endodontic file and cause it to vibrate at about 25,000 vibrations per second. • This procedure induces acoustic streaming and cavitation of the irrigant:

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CHAPTER 7 Root canal obturation Contents Objectives of obturation

Pre-obturation procedures

Correct timing of obturation

Techniques of obturation

Obturating materials

Obturation in difficult situations

Conventional instruments used for obturation

post-obturation considerations

Common errors during obturation

Maintaining sterility of root canals

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OBJECTIVES OF OBTURATION (WHY TO OBTURATE ROOT CANALS) Obtaining coronal seal Proper coronal seal will eliminate coronal leakage of microorganisms or potential nutrients to support their growth in dead space of root canal system.

Obtaining apical seal To prevent percolation of periapical fluids into the root canal system and feeding microorganism.

Entombing remaining bacteria Proper obturation will confine any residual microorganisms that have survived the chemo mechanical cleaning and shaping, thereby denying them access to the periapical tissues and any intracanal nutritional sources to prevent their proliferation and pathogenicity.

Diagram showing objectives of obturation. A) Coronal seal. B) Entombing remaining bacteria. C) Apical seal. Note that the blue particles indicate bacteria.

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B C

CORRECT TIMING OF OBTURATION (WHEN TO OBTURATE) Single visit vs. multiple visits Single visit treatment: • The obturation step is performed in the first visit with other steps of root canal treatment (diagnosis, access opening, working length determination and chemo-mechanical preparation) • Obturation at the initial visit precludes contamination as a result of coronal leakage during the period between patient visits. Multiple visits treatment: • Generally the preparation is completed at the first appointment and the root canals are filled at the next appointment. • When root canal treatment is carried out in multiple visits, the root canals should be medicated with an antimicrobial medicament between appointments (inter-appointment medicament). Calcium hydroxide is the interappointment medicament of choice.

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Factors that determine number of treatment visits Status of the pulp and periapical tissues (fig.1) • It is generally accepted that a single visit treatment is appropriate for teeth with vital pulps (e.g. teeth undergoing elective root canal treatment, teeth with irreversible pulpitis, etc). • Necrotic pulp tissue Patients who present with pulp necrosis, with or without asymptomatic periradicular pathosis, for example, asymptomatic apical periodontitis, chronic apical abscess, or condensing osteitis, may also be treated in one visit. However, these cases are more challenging to disinfect. This is particularly true in teeth which require root canal retreatment as they tend to be infected with very persistent microbes, which are especially difficult to eradicate. Scientific evidence has shown that an inter-appointment calcium hydroxide medicament significantly reduces the microbial load of the root canal system when compared to root canal preparation and irrigation with sodium hypochlorite alone. Logically one might therefore expect better endodontic outcome for multiple visit root canal treatment.

Patient’s signs and symptoms • When a patient presents for treatment with acute symptoms, such as pain and swelling associated with pulp necrosis and acute periapical abscess, it may be prudent to prepare the root canals at the first visit and fill the root canals at a subsequent appointment when the patient’s symptoms have resolved. • Postoperative pain and/ or swelling is more likely to occur when single visit treatment performed with patients present with preoperative acute symptoms. In such cases it may be more prudent to carry out root canal treatment over more than one visit. • Sensitivity on percussion indicates inflammation of periodontal ligament space, hence canal should not be obturated before the inflammation has subsided. • If obturation is done in tooth with purulent exudate, pressure and subsequent tissue destruction may occur rapidly. In such cases, calcium hydroxide should be placed as an intracanal medicament (to obturate, the canal must be dry and not exhibit bad odor) (note that Incorporating blood or inflammatory exudate into the root canal filling compromises the seal and provides microbes with nutrient sources and space to multiply).

Procedural difficulty (fig.2-3) • Some teeth may be more difficult to treat than others and the complexity of the case may result in the need for multiple visits due to time constraints. • Examples of cases which may be more time-consuming include those involving teeth with challenging anatomy: - Cases in which there is difficulty achieving effective anesthesia. - Cases with calcified canals or very complex root canal system. - Retreatment cases in which the existing root canal filling material is challenging to remove. - Filling root canals of teeth with open apices can be challenging, as the natural resistance form (i.e. root canal taper) to compaction of the root canal filling is no longer present. The traditional method for creating an apical barrier in these cases (‘Apexification’) involves multiple visits.

Patient management • Patient preference, circumstances, and/or medical conditions may have a bearing on the timing of root canal filling. • For example, a patient with an endodontic problem associated with a mandibular molar who has severe hemophilia may require clotting factor cover prior to the administration of an inferior alveolar nerve block. In this case it would be pragmatic to carry out root canal treatment of a mandibular molar in a single visit, if at all possible. • Some patients may find it difficult to attend several appointments due to work/personal commitments and may request that the treatment is carried out in one visit. If the treatment period would exceed 2 hours and/or

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the clinician believes that he or she may be better prepared to treat the case at subsequent appointments, obturation should be delayed. • Patients with neck/back/TMJ complaints may prefer multiple shorter appointments rather than a single prolonged appointment in order to avoid the discomfort of lying in a dental chair or opening mouth for extended periods.

Figure 1 Nonvital mandibular first premolar with periapical pathology is not indicated for single isit endodontics, whereas uncomplicated mandibular second premolar with carious exposure can be completed in single-visit dodontics.

Figure 2 Root canal treatment of molars with curved canals is a poor candidate for single visit endodontics

Figure 3 simple endodontic treatment of lower second premolar that can be performed in single visit.

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• This should not be used if apical foramen is very wide to avoid sealer extrusion beyond apex.

Figure 44 Sealer can be applied in canal by coating it on guttapurcha cone.

Figure 45 Sealer can be placed in canal by applying it on master apical file and turning counter clockwise.

Figure 46 Injectable syringe for carrying sealer.

TECHNIQUES OF OBTURATION Obturation methods vary by direction of compaction (lateral/vertical) and/or temperature of gutta-percha used either cold or warm (plasticized). The most popular obturation method is lateral compaction, followed by continuous wave warm vertical compaction.

COLD OBTURATION TECHNIQUES These include single cone technique and cold lateral compaction technique.

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Single gutta-percha cone and sealer • Most modern canal preparation techniques advocate the use of a greater taper (typically 6 degree taper). In such cases it has been suggested that gutta-percha points of matching taper may be used (fig.47). It has been further suggested that these fit the prepared canal so well that a single gutta-percha point and sealer may be sufficient for sealing the canal space. • Though this technique appears to be very simple and effective, the fact is that the majority of sealers are soluble and the canal is not perfectly uniform in shape, but in fact an intricate web. A single cone would not sufficiently fill the canal in three dimensions (underfilling) (fig.48), and moreover with dissolution of sealer, we would have apical leakage into the canal over a period of time. This technique cannot therefore be recommended (fig.49).

Figure 48 diagram showing that the canal is not perfectly uniform in shape, but in fact an intricate web. A single cone would not sufficiently fill the canal in three dimensions.

Figure 47 Example of matching ProTaper NEXT size X2 file, paper point, and GP point

Figure 49 failed treatment due to use of single cone technique.

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• Single cone with bioceramic sealer (fig.50): - There has been renewed interest in single-point obturation, driven by a new class of "bioceramic" sealers that create a tight, 3-dimensional seal all along the canal, penetrate the inaccessible portions of the canal, and set well in the presence of moisture due to their hydrophilic nature. - The single cone is coated with sealer and inserted to the apex, resulting in a uniform mass that eliminates the type of failures that are associated with the use of multiple cones. - This simplified technique is more efficient and less time-consuming than any of the traditional methods of compacting gutta-percha. From a clinical perspective, operator and patient fatigue are reduced, preservation of coronal dentin is increased, and lateral pressure on the root is eliminated.

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Figure 50 A) Preoperative radiograph. B) Obturation done with single cone with bioceramic sealer. C) Follow-up, 1-year postoperative radiograph demonstrates complete healing.

Cold lateral compaction It is one of the most common methods used for root canal obturation. It involves placement of tapered guttapercha cones in canal and then compacting them under pressure against the canal walls using a spreader providing space for accessory gutta-percha cones to completely and efficiently obturate the root canal.

Case selection Lateral compaction of GP may be used in most clinical situations. Exceptions are severely curved or abnormally shaped canals (e.g. c-shaped canals) and those with gross irregularities, such as internal resorption.

Step by step (fig.51-55) 1-

Spreader and Master Cone selected. Here, standard master cones are preferred as Standard cones generally have less taper when compared with nonstandard cones and will permit deeper spreader penetration, which will result in a better-quality resultant seal. 2- Dry the canal with paper points and apply sealer in canal. 3- Place master gutta-percha cone in the canal. 4- Place spreader into the canal alongside the cone: - Spreader helps in compaction of gutta-percha. It acts as a wedge to squeeze the gutta-percha laterally under vertical pressure not by pushing it sideways. - Only light pressure is required during lateral compaction because as little as 1.5 kg of pressure is capable of fracturing a root. In addition to the force applied, investigators have noted that removal of excessive amounts of dentin during preparation is a significant factor in root fracture. - It should reach 1–2 mm of the prepared root length (verified using rubber stop).

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- If the root canal is curved, the finger spreader should be inserted along the outermost side of the root canal. This is less likely to result in the sharp tip of the finger spreader engaging the GP point and leading to the inadvertent removal of the point when the finger spreader is withdrawn (fig.56). - The spreader should be left in situ for 30 seconds. This continuous pressure from the spreader is required to deform the gutta-percha point against the canal walls and to overcome its elasticity. - Remove spreader by rotating it back and forth (clockwise and anticlockwise) whilst maintaining apical pressure.

5-

- This compacts the gutta-percha and creates a space for accessory cones lateral to the master cone. - Note that the pressure of lateral compaction may allow up to 1 mm of further apical movement thus caution should be taken to avoid overfilling. Placing accessory cone: - Select an accessory point with locking tweezers and dip its tip into sealer. Do not leave the points in sealer while working as a reaction may occur between the zinc oxide in the points (up to 80%) and the eugenol in the sealer, softening the points and making insertion difficult. - Immediately after withdrawing the spreader, the accessory point is placed alongside the master point. Any delay will allow the master point to relax and space will be lost. - This stage is best carried out using two hands. Assuming the operator is right handed, the tweezers holding the accessory point are aligned above the tooth in the right hand, while the left hand rotates the

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spreader a few times through an arc of 30 to 40° and withdraws it (fig.57). Remove residual sealer from the finger spreader and then repeat the above procedure until spreader no longer penetrates beyond the coronal third of the canal (The accessory cones should therefore be the same size or slightly smaller than the selected spreader). (Optional): A radiograph may be exposed after one or two cones have been placed before searing off the tops. If there are length problems, the cones can be easily retrieved. The entire mass can usually be removed by grasping the cones with fingers or cotton pliers and removing the entire mass. Now sever the protruding gutta-percha points at canal orifice with hot instrument (fig.58). The remaining gutta-percha is firmly compacted by with cold condenser or plugger to seal the coronal access to the canal at the orifice or approximately 1 mm below the orifice in posterior teeth. In anterior teeth, the desired level is the cementoenamel junction on the facial surface to avoid aesthetic issues if the dentin should become stained.

Advantages • It decreases the chances of overfilling. • The technique is simple in application and requires very little infrastructure. • It is cost effective.

Disadvantages • Presence of voids is common if not properly performed. • Increased sealer: GP ratio due to multiple placement of sealer that associated with each accessory cone. • Does not produce homogenous mass (Space may exist between accessory and master cones) • Time-consuming. • Spreader may induce stress on roots sufficient to fracture them. • Not applicable in some cases as in internal root resorption or complex root canal system.

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Figure 51 master ne selected and verified.

Figure 52 The appropriate sized finger spreader is inserted into the root canal beside the master GP point and extends to within 1 mm of the apical extent of the master GP point.

Figure 53 finger spreader is reinserted many times to allow space for accessory cones.

Figure 55 A mid fill periapical radiograph gives the clinician an indication as to how well the root canal filling is compacted. Alterations ca then be made to the filling as necessary.

Figure 54 The root canal has been filled with GP points and cannot accommodate any more.

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Figure 56 If the root canal is curved, the finger spreader hould be inserted along the outermost side of the root canal.

Figure 57 do not leave the points in sealer while working as a reaction may occur between the zinc oxide in the points (up to 80%) and the ugenol in the sealer, softening the points and making insertion difficult.

Figure 58 when no longer space for spreader. (B) A heated instrument is used to sever the gutta percha cones and (C) vertically condensed.

Summary of cold lateral compaction. (A) Check the fit of the spreader; (B) place the master gutta-percha cone in sealer coated canal; (C) place the spreader alongside the master cone to compact the cone; (D and E) Add accessory cones in the prepared space and repeat the step C to create space for more accessory cones; (F) Place accessory cone in this space and repeat the above procedure until spreader no longer penetrates beyond coronal third.

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Cold lateral compaction technique showing unobturated isthmus areas.

Variation of cold lateral compaction →

Warm lateral compaction using ultrasonics (energized

spreading) • This technique is a modification of cold lateral compaction and follows the same protocol as listed above. • A piezoelectric ultrasonic unit is required, as well as a file adaptor and a k type of file. • The ultrasonic unit is set to a higher power setting and is activated only when the file comes into contact with the GP. The file is then gradually introduced into the GP and heat is generated to soften it. The file should ideally pass to 1 mm from the working length while making a tract in the GP. • A spreader is then placed into this tract to the same length, followed by a corresponding accessory point. This can be repeated two to three times. • This technique has a slight advantage over cold lateral compaction, in that the thermoplasticized GP may flow into accessory anatomy and defects caused by internal resorption. It is considered a cost effective technique.

File adaptor and K type file

Energized file contacting GP

Energized file making a tract to 1 mm from working length.

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CHAPTER 8 Root canal retreatment Contents Criteria of failed root canal treatment

Shaping considerations in retreatment

Causes of failed root canal treatment

Cleaning considerations in retreatment

Factors affecting retreatment decision

Obturation considerations in retreatment

Steps of root canal retreatment

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Endodontic retreatment can be defined as further treatment performed because the initial treatment was inadequate or the lesion failed to heal.

CRITERIA OF FAILED ROOT CANAL TREATMENT (WHEN TO CONSIDER THE TREATMENT TO BE FAILED TREATMENT?) Clinical failure (fig.1-2) Persistence or development of signs & symptoms of periapical or periodontal disease after treatment means failure of root canal treatment. These signs and symptoms include some or all of the following: • Continuous pain. • Tenderness to percussion or palpation. • Tenderness to thermal stimuli. • Pain on chewing or mastication. • Increased mobility of the treated tooth. • Loss of periodontal support of the treated tooth. • Development of swelling and or sinus tract. • Radiographically, new periapical or periradicular lesion developed or the initial periapical lesion (existed before primary treatment) increase in size and the root canal filling usually appear deficient.

Theoretical failure (fig.3-5) This situation corresponds to either: a)

b)

A tooth with technical deficiencies in primary treatment (e.g. underfilling, overextension, fractured instrument…..etc), yet there are no clinical signs or symptoms or radiographic evidence of failure. The absence of a lesion is not always synonymous with an absence of microorganisms in the root canal system (e.g. absence of symptoms does not confirm absence of a disease). When microorganisms are in a dormant stage, a balance may exist between the host defenses and the intracanal irritants. This delicate equilibrium can be upset by a change in the microbial flora or in the host resistance, or by microbial recontamination through coronal leakage when there is a deficient coronal restoration. The patient is also asymptomatic, yet a radiographical periapical lesion exists. In these instances, the question is whether these lesions will heal without additional intervention. Usually, when the quality of treatment appears adequate, the healing process will take place after a minimum period of one year. However, it has been shown that some lesions required 10 years or more to heal. An example of such a scenario is a symptom-free endodontically treated tooth which has been restored with a well-fitting post-retained crown which was treated several years previously; however, a periapical radiolucency is detected as an incidental finding. This tooth would be a candidate for root canal retreatment; however, treatment may be deferred until symptoms arise. The patient must be informed that they will require regular reviews to confirm that the existing radiolucency is not increasing in size, and that they should return immediately if symptoms arise. The patient must also be warned of the possibility of an unexpected acute flare-up.

c)

The third situation of theoretical failure is the following. Any root canal treated tooth is failed when the access cavity has been inadequately sealed and has been open to the oral environment for a considerable period of time (3 to 4 months), even if the root filling seems adequate radiographically. Numerous studies over the past 10 years have demonstrated that if the coronal seal is deficient, bacteria can infiltrate and migrate down to the apex even when root canals are adequately filled. Although the reported time for this migration of bacteria varies from study to study In vivo studies have shown that the first signs of periapical pathology can appear 4 months after treatment.

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Figure 1 The presence of a painful swelling is often one of the clinical signs characteristic of periapical lesions of endodontic origin.

Figure 4 theoretical failure root canal treatment (inadequate treatment but there is no symptoms or radiographic lesion).

Figure 2 periapical lesion associated with failed root canal treatment of upper incisor.

Figure 3 Radiographic scenario in a patients of more than 80 years of age. The lesion is t symptomatic; given the general situation, the patient should have an annual x-ray to monitor the progress of the lesion.

Figure 5 theoretical failure of root canal treatment of upper first premolar. Endodontic treatment had been initiated 6 years. The coronal restoration lost since 5 months, then retreatment is indicated although the root filling seems adequate radiographically.

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CAUSES OF FAILED ROOT CANAL TREATMENT (POSTTREATMENT DISEASE) When managing a case of post-treatment endodontic disease, it is important to identify the cause(s) for posttreatment disease. This is an essential step in clinical decision-making and treatment planning as it presents an opportunity for the clinician to improve on previous treatment as well as prevent further recurrence of disease. Care should be taken to identify non-endodontic causes which will clearly not benefit from further endodontic retreatment.

Endodontic (Intraradicular) causes (fig.6-9) Irrespective of the technical inadequacies or errors, all endodontic failures are directly associated with the presence of bacteria and their toxins in the root canal system; these irritants migrate into the periodontal tissues by any route possible (e.g. apical foramen, lateral canals, accessory canals). These remaining bacteria is present due to either some or all of the following: • Contamination of an initially sterile root canal during treatment. This usually occurs due to negligence in placing a good temporary or interim seal during multi-visit endodontics or due to ignoring placement of rubber dam during the whole treatment procedures. • Access cavity related misshapes that not managed properly (for example, underextended cavity walls, perforation in pulpal floor….etc). • Cleaning and shaping related misshapes that not managed properly (for example, instrument fracture, canal transportation, canal ledging, and canal blockage….etc). • Obturation related misshapes that not managed properly (for example, underextended obturation, overextended obturation…etc). • Poor coronal seal due to poor final restoration (either the final restoration is placed late or placed early but not properly provide tight coronal seal). • Bacteria invasion: There are several possible pathways for the infecting microbes to invade the filled root canal. These include caries, crown-root cracks and fractures, leaking fillings, lateral canals from the crevice area or from a periodontal pocket, and dentinal tubules exposed by removal of cementum during root planing or abrasion, through the apical foramen from a periodontal pocket extending to the apex, or via bacteremia.

Non-endodontic (Extraradicular) causes Non-endodontic failures occur due to existence of bacteria outside the root canal systems but result in signs or symptoms similar to endodontic failures. They include: • Radicular cysts: they are usually chronic non-symptomatic lesions that discovered radiographically. They usually need surgical intervention. They can undergo acute exacerbation at any time. • Vertical root fracture: Vertical root fractures are more commonly associated with endodontically treated teeth, with high susceptibility reported in maxillary and mandibular premolars, mesial roots of mandibular molars, mesiobuccal roots of maxillary molars, and mandibular incisors. The early signs and symptoms of vertical root fracture may include dull pain on chewing, swelling, and sinus tract, which mimics post-treatment endodontic disease. Radiographically, an advanced vertical root fracture will exhibit a ‘halo’ or ‘J-shaped’ radiolucency. • Chronic marginal periodontitis: Chronic marginal periodontitis can progress apically along the root surface, and present as a periodontal defect which may therefore be confused with periapical periodontitis. The prognosis of an endodontically treated tooth with chronic marginal periodontitis will depend on the success of the periodontal treatment.

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Importance of preoperative radiograph in identifying the cause of the failure (fig.1014) • Pre-operative Periapical radiographs in retreatment cases were used to assess the problems and failures of root canal treatment. • When there are clinical signs and symptoms of failed root canal treatment, the following problems can be seen in preoperative radiograph that confirm failure: - Fractured (separated) instrument (e.g. file) inside root canal(s). - Apical transportation - Iatrogenic Perforations in root canal system (pulpal floor perforation, strip perforation, lateral perforation, apical perforation and post perforation). - Missed main or accessory canal(s). - Underfilling and underextended obturation (the original cause here can be identified clinically and intraoperatively that may be ledge, calcified canal, under extended working length...etc.) - Overfilling and overextended obturation. - Poor coronal seal. - Vertical root fracture. - Periapical radicular cyst. • Conventional periapical radiograph is the most commonly used method to check the success and failures of endodontic treatment but it has some limitations. Radiographs show two dimensional images of a three dimensional structures and superimposition of adjacent anatomic structures; especially in area of maxillary molars makes it difficult to interpret the radiographs. Thus, multiple periapical radiograph with different angulations should be used (fig.11). • If periapical radiographs are not sufficient to provide the required details, CBCT is very beneficial to identify the hidden cause of root canal treatment failure. This information may not only help in formulating diagnosis but also improves the management (fig.12). • CBCT is three-dimensional imaging method that gives the possibility to view an individual tooth or teeth in any view. Whereas the limitations of CBCT and radiation dose to the patients must always be taken into consideration when selecting them odes of diagnostics. • The importance of preoperative radiograph is invaluable. It must be remembered that in addition to providing information, the radiographs play an essential role in establishing a medico legal record. A preoperative radiograph of the tooth should be kept in the patient’s files to demonstrate, should the need arise, the condition of the tooth before treatment. Without this it could be difficult after treatment to convince a patient that a fractured instrument or perforation was present before the retreatment was conducted (fig.13). • The preoperative radiograph should be clear and should show the root apex with at least 2–3 mm of the periapical region to provide the accurate and detailed information (fig.14).

Figure 7 Microleakage because of defective coronal seal can result in endodontic failure.

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Figure 6 Decay at subgingival area below own can result in contamination of root filling and contribute to endodontic failure.

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Figure 8 Overextension of canal results in endodontic failure due to constant irritation to periapical tissues.

A

Figure 9 Remaining infective tissue, microorganisms, and their byproducts of incompletely filled space act as constant irritant resulting in endodontic failure.

B

Figure 10 importance of angled periapical radiograph in multi-canals tooth. A) A non-angled periapical radiograph of a mandibular molar shows persistent periapical lesions, despite an apparently good root filling. B) An angled radiograph reveals a fractured instrument in the mesial root. The radiograph shows the instrument lying in the mesiobuccal root; there may in fact be two separate apical foramina.

Figure 11 the radiographs play an essential role in establishing a medico legal record. Without this preoperative radiograph, it could be difficult after treatment to onvince a patient that a fractured instrument was present before the retreatment was conducted.

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Figure 12 importance of preoperative periapical radiograph in identifying the possible etiology of post treatment disease that may include the following: A) overextended obturation and poor apical seal (red arrow) & poor coronal seal (yellow arrow). B) Underextended and underfilled obturation. C) missed canal in upper premolar (red arrow) and lower incisor (yellow arrow). D) Perforation in pulp chamber floor. E) Lateral root perforation. F) Strip perforation resulting in loss of control on obturating material. G) Apical perforation (red arrows points to false canal whereas the yellow arrow points to true canal path). H) Root perforation due to improper post placement. I) separated instruments in mesial and distal canals. J) Apical transportation. K) Vertical root fracture (note the J shaped radiolucency indicated by dashed yellow line). L) Apical radicular cyst that need surgery.

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Figure 13 example of limitation of conventional radiographs. The patient, a 26-year-old female, had undergone root canal treatment on tooth 12 as a result of a traumatic event; after about 2 years after treatment, a narrow vestibular fistula was observed on the same tooth. A) Periapical radiograph shows a very extensive lesion secondary to a nonexceptional but acceptable endodontic treatment. B) Presence of sinus opening. C) Periodontal pocket presence. D) The CBCT image brings to light a radically different scenario, because it is the result of a perforation of the middle third with extrusion of the filling material. E) Surgical exposure of the defect. F) The gutta-percha in the perforation was cut.

Figure 14 non-clear preoperative radiograph does not enable the clinician to identify the fractured file before beginning the retreatment procedure. In this case, the patient symptoms are sensitivity to hot stimuli after 2 months of endodontic treatment that increase the possibility of missed canal, thus the retreatment is initiated. During gutta percha removal, an obstruction is encountered in a distal canal which is a separated file (red arrow). Note that the cause of pain is found to be from missed second canal in distal root.

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Example of extending inadequate access cavity. A) Preoperative radiograph of a maxillary second premolar with a lateral radiolucency (arrow). B) Midtreatment photograph (after removal of the post and crown) displaying the inadequate access cavity. C) Extending the access cavity lingually reveals the oval canal. D) Postoperative radiograph demonstrates the presence of a lateral canal.

STEP NO. 2: REMOVAL OF ROOT CANAL FILLING General guidelines for removal of root canal filling: Regardless of the technique adopted for removing obturation material, some simple rules must be followed to avoid further complications: • From the preoperative radiograph we can identify important tip which is that if a canal has been obturated to its full length, removal of the obturation material is relatively easy and should not pose many problems. If a canal has been obturated short of the apex, there are two possible scenarios: 1)

The apical portion of the canal is not calcified or blocked; it needs to be explored and negotiated with small-diameter stainless steel hand files.

2)

A ledge may have been created apically during the initial treatment; such situations can be complicated further by curvature of the canal that may or may not be detected radiographically. Rotary nickel-titanium instruments should never be used to negotiate the canal in such cases.

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• After penetrating just a few millimeters into the canal, the clinician must reassess the angulation of the preparation and modify it as necessary to allow straight-line access and ensure good control of the instruments. Failure to gain straight-line access may lead to coronal blockages, make further instrumentation of the canal difficult, and increase the chances of creating a perforation or obstruction. This first stage in refining the access preparation should be completed with a Gates Glidden bur or with dedicated nickeltitanium instruments designed for this purpose (orifice openers). The instruments must never be forced apically but should be carefully introduced a few millimeters into the canal and then withdrawn, removing dentin on the upstroke (fig.70-72). • The obturation material should be removed progressively as the instruments are advanced further down the canal; this prevents material extrusion through the apex. • All files and instruments should be regularly wiped clean on damp gauze so the clinician can assess them for any signs of damage or loss of threading that could lead to instrument fracture. • If excessive resistance is encountered, instruments should not be forced. A radiograph may reveal the cause of the obstruction. Forcing instruments apically into a ledge is the chief cause of iatrogenic perforations during retreatment procedures. There are two possible causes for resistance: 1. There is obturation material remaining in the canal, but the instrument being used has too large a 2.

diameter. The obturation material has been removed and the resistance is due to a ledge or calcification of the

canal. In both these situations, a fine, precurved file should be used to help negotiate the canal further; careful use of the instrument will either allow the remaining obturation material to be removed or enable the ledge to be bypassed. • Identifying the obturation material: The obturation material may be visible at the level of the canal orifice, but this is not the case in teeth that have been restored with a post-retained crown. A) If the material is not visible at the canal orifice (fig.73): - After the removal of a post, any residual cement in the base of the preparation (e.g., zinc phosphate, zinc polycarboxylate, glass ionomer) hinders access to the canal and interferes with the action of solvents. - The most effective way of removing this material is with the use of ultrasonic instruments (ProUltra Endo 6 to 8, Dentsply-Maillefer; or ET20 and ET25, Acteon) or wide-diameter ultrasonic files (diameter 35/100, Acteon). These instruments should be used only under direct vision in order to avoid perforations or transportation of the canal. - The ultrasonic tip is placed in the canal, resting on the plug of material, and activated for a few seconds. The canal is then irrigated and dried, and a drop of solvent is placed. A stainless steel hand file is used to check whether the cement has been removed; if the plug of material remains in place, the same procedure can be repeated. - Once the residual cement has been eliminated, removal of the obturation material further down the canal can be attempted. B) If the material is visible at the canal orifice, the removal will be straight forward. • The majority of inadequate root canal fillings are unsatisfactory because of insufficient preparation and obturation of the entire root canal system. If the obturation material is soluble, the iatrogenic complications (e.g. obstructions, calcification, and curvature) are the clinician’s main concern; removal of the material should not be difficult.

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Figure 71 eliminating the coronal shoulder of dentin opens up the access preparation, thus ensuring straight-line access for instrumentation.

Figure 70 If coronal access is not modified at the beginning of the procedure, it will be difficult to advance instruments further down the canal. The risk of blockages and perforations is high (arrow).

Figure 72 Removal of obturation material always begins with modification of the access preparation to ensure straight-line access.

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Figure 73 A) Preoperative radiograph of a mandibular second molar (fixed partial denture abutment) with a periapical radiolucency. B) To remove the residual plug of luting agent, an ultrasonic tip is placed on the material and activated for several seconds. C) With the plug of material removed, solvents can be used to dissolve the obturation material.

C

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Removal of Conventional Gutta-percha filling Removal of gutta-percha generally poses no problems; it is usually more easily removed than other obturation materials.

Different methods for removal of gutta-percha filling Manual stainless steel files method The flutes of a Hedström file make it suitable for engaging GP (fig.74). A Hedström file is gently screwed into GP and the file is pulled out grasping GP. The size of the Hedström file is chosen so that it will engage the loose guttapercha root filling but not the canal wall. Hand instruments are mainly used in the apical part of the canal (fig.75). Reamers or files can be used to bypass the gutta-percha sometimes thus, facilitating its removal.

Rotary Ni-Ti files method (fig.78) • Rotary instrumentation is the most efficient method for removing gutta-percha from a previously treated root canal. • There are many dedicated gutta-percha removal instruments, such as the GPX (Brasseler, Savannah, GA), the ProTaper Universal retreatment files (Dentsply, York, PA), and the Mtwo R (Sweden and Martina, Padua, Italy). For example, protaper universal system consists of D1, D2, and D3 files (fig.76): - D1: it removes filling from coronal third. It has the following criteria → 11 mm handle, 16 mm cutting surface, White ring for identification, ISO 30- active tip for easier penetration of obturation material & 9% taper file. - D2: it removes filling from middle third. It has the following criteria → 11 mm handle, 18 mm cutting blades, two white rings for identification, ISO 25, nonactive rounded tip to follow canal path & 8% taper file. - D3: it removes filling from apical third. It has the following criteria → 11 mm handle, 22 mm cutting blades, three white rings for identification, ISO 20 nonactive rounded tip to follow canal path & 7% taper file. • This method can remove gutta-percha by using mechanical principle alone or by using mechanical and thermal principles as follows: - Mechanical principle: here, the rotary files used at the conventional speed (around 300 rpm) and torque values and the files will effectively remove gutta-percha coronally, owing to the fluted design of the instrument. - Mechanical and thermal principles (fig.77): Some authors suggest the use of rotary nickel-titanium instruments, without solvent, at speeds of 700 to 1,200 rpm. When used at these speeds without any form of coolant, the instruments heat the gutta-percha (by friction), thereby softening it; owing to the design of the instruments, the softened obturation material is propelled coronally. This technique should be used only in straight canals and might be dangerous because of the increased risk of the instrument screwing into the canal or fracturing; this technique offers no major advantage over more controlled methods. • Safety precautions: - Rotary instruments are safe to be used in straight canals. - Rotary instruments should be used with caution in underprepared canals and are generally not selected for removing gutta-percha in canals that do not accept them passively (due to high taper of retreatment files). - When attempting gutta-percha removal, it is useful to mentally divide the root into thirds and then select two or three appropriately-sized rotary instruments that will fit passively within these progressively smaller regions. - Care should be taken to use short pecking motions to engage the gutta percha. - The file should be removed and frequently inspected to assure filling material can be visualized on the apical flutes.

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- Following initial engagement of the gutta-percha, a brushing motion on the outstroke helps improve its removal. If resistance to progression is felt, a radiograph should be taken to assess if all material has been removed or not. If there is no radiographic evidence of residual filling material, it is wise to continue the procedure with stainless steel hand K-files. • It is recommended that after rotary gutta-percha removal, subsequent hand instrumentation is needed to remove the residual obturating materials completely from the canal.

Rotary gates Glidden method Gates-Glidden drills are effective for gutta-percha removal but should be limited to straight canals or the coronal portion of curved canals in which rotary NiTi files can then be used to remove GP from the apical portion of the root canal. Gates-Glidden drills usually used to enlarge coronal opening of root canals to allow the deeper gutta-percha filling to be reached and then removed.

Heat method Heat can cause conventional gutta percha to plasticize, thus it can be applied to gutta-percha filling by any of the following different ways: • Hot file or reamer can be used to remove the gutta-percha points. • Flame-heated gutta-percha pluggers can be used to soften the material for removal with hand instruments. The pluggers cool quickly (about two seconds) because the gutta-percha rapidly dissipates the heat; therefore, removal can be done only in short increments. This technique preserves internal canal tooth structure. However, the heated hand plugger technique is time-consuming, and when the apical portion of the canal is approached, it can increase the risk of pushing the gutta-percha beyond the apical foramen. A more predictable alternative method involves using thermostatically heated pluggers that can be placed into the gutta percha without cooling down. • Thermostatically heated pluggers: These devices allow insertion into the gutta-percha toward the apical portion of the canal, increasing the probability that the mass of the material can be removed as the plugger is cooled down. This method also decreases the probability that gutta-percha will be extruded out of the apical foramen. After a large portion of the gutta-percha has been removed, the retreatment can be continued using irrigation and instrumentation in a crown-down manner. The technique is to activate the instrument so that it is red-hot and then plunge it into the coronal-most aspect of the gutta-percha. The heat carrier is then deactivated and, as it cools, will typically freeze a bite of gutta-percha on its working end. Instrument withdrawal generally results in the removal of an attached bite of gutta-percha. This process is repeated as long as it continues to be productive.

Solvent method • Gutta percha can be dissolved chemically using the following solvents (fig.79) → chloroform, Methyl chloroform, xylene, halothane, eucalyptol and orange oil (fig.80): - The most effective solvent has been shown to be chloroform. The solvent works quickly, but care must be taken not to extrude the material out of the apical foramen. Concerns have been raised regarding its cytotoxicity if it comes into contact with periapical tissues; it has been classed as a carcinogen and a potential risk to the dental team. However, there is limited evidence of carcinogenicity and some manufacturers continue to recommend the use of chloroform to assist in the removal of gutta-percha (Since at high concentrations, it has shown to be carcinogenic, its excessive filling in pulp chamber is avoided).

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- An alternative to chloroform is halothane, which is slower to dissolve gutta-percha but shows acceptable results. The increased cost and volatility of halothane and the potential for idiosyncratic hepatic necrosis make it less desirable to use as a gutta-percha solvent. - Methyl chloroform is another alternative to chloroform. It is more effective than eucalyptol and xylol, shows less toxicity, and is not carcinogenic. • The solvent is usually left for 2–3 minutes to dissolve GP, followed by removal with a hand-file or rotary NiTi file. C+ files (which are end-cutting and more rigid) may cut through GP more efficiently. • Use of solvents risk smearing GP along the root canal walls, uninstrumented or difficult to access areas, and potentially entering dentinal tubules. This smear will be difficult or impossible to remove and certainly compromise chemo-mechanical debridement, as well as the adaptation of the final root canal filling. • Solvents should not be used in the middle to apical third in cases where the gutta-percha extends beyond the apex. In such cases, an attempt should be made to retrieve the gutta-percha en masse.

Ultrasonic method (fig.81) • A single cone or poorly condensed gutta-percha root filling may be removed using ultrasonics. • A small size endosonic file will suffice as it is not used to physically engage the root filling. • The technique relies primarily on a combination of irrigation and ultrasonic vibration to loosen the root filling, allowing it to be “floated” passively out of the canal. As a result, the technique carries a very much lower risk of instrument fracture. • However, it should be reiterated that the endosonic file must not be run dry as the gutta-percha will be plasticized by the energized file, making it difficult to remove the root filling intact. • Note that the ultrasonic files can only be used in the straight part of the canal.

Method selection Selecting the method to remove the gutta percha filling depends on the case as follows:

If cold lateral condensation or a single-cone technique (ill-fitting gutta percha) has been used for previous failed obturation (fig.82) It is not advisable to apply a solvent; use of a solvent would cause the gutta-percha and the sealer to form a sticky paste that is difficult to remove. If space exists or can easily be created between the canal wall and the obturation material (bypassing gutta percha by probing the canal using a precurved #10 or #15 K-file), a hand reamer or Hedstrom file can be placed in the canal and the instrument twisted in a gentle clockwise direction until the gutta percha is engaged. The gutta percha can occasionally be removed in one piece in a lifting motion without rotation.

If the canal not previously properly shaped (no taper) Here, the rotary files should not be used as they could not be inserted passively into the root canals. Manual files and solvents should be used here to remove gutta-percha.

If the gutta-percha extended beyond the apical foramen (fig.83) In this case there are 3 options to remove this extended gutta percha as follows: 1.

Removal using H file: - Overextended gutta-percha removal can be attempted by inserting a new Hedstrom file into the extruded apical fragment of root filling using a gentle clockwise rotation to a depth of 0.5 to 1.0 mm beyond the apical constriction. The file is then slowly and firmly withdrawn with no rotation, removing the overextended material.

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- This technique works frequently, but care must be taken not to force the instrument or else further extrusion of the gutta-percha or separation of the file may result.

2.

- The overextended apical fragment should not be softened with solvent as this application can decrease the likelihood of the Hedstrom file getting a solid purchase hindering retrieval. Removal using the XP-3D Shaper rotary file (fig.84): - It can be used to remove gutta-percha extruded up to 3 mm past the apex during obturation. - The serpentine shape of this file creates a corkscrew effect allowing the file to encircle gutta-percha and pull it out of the canal. - This method does not require any extra armamentarium and is a safe, easy and efficient alternative to the other methods that are currently used.

3.

- The XP-3D Shaper could be used at 1000-2000 rpm speed, 2-3 mm short of the radiographic apex. The file is moved up and down a few times until a string of gutta-percha is visible that can be grasped with cotton pliers and removed from the canal. A radiograph should be taken to confirm complete removal of the extruded material. Removal using surgical approach: If the overextended gutta percha cannot be removed using the 2 previous methods or the overextended gutta percha is related or very close to vital structure (e.g. nerve, maxillary sinus….etc.), then surgical approach is indicated.

If the gutta-percha appears as a compact & dense mass • If the coronal gutta-percha appears as a compact mass, a Gates Glidden drill is used without solvent to open up the canal orifice and clear the first few millimeters of the canal. Then the rotary Ni-Ti files can be used. • Also combination of manual files and gutta-percha solvent can be used as follows: - This option is best utilized to remove gutta-percha from densely filled canals when they are narrow &curved. - A pilot hole is first created in the coronal portion of the canal with either a hot heat carrier or by using the Protaper Retreatment D1 instrument. - Two or three drops of chloroform are then introduced into the newly created reservoir inside the root canal. - A sequential technique is advocated to remove the filling material. It involves the use of H-type files, 21 mm in descending order to gently “pick” into the chemically softened gutta-percha. Shorter instruments are preferred since they provide more stiffness and have less tendency to flex. Without trying to engage the more apical material, a lateral motion is used with the H-file to remove gutta-percha remnants at this level. - This method is repeated to progress apically until gutta-percha is no longer evident on the cutting flutes of the file when it is withdrawn from a solvent-filled canal. - Such a progressive removal technique helps prevent the needless extrusion of chemically softened guttapercha periapically.

Removal of residual materials The residual gutta-percha and sealer are, invariably, not considered separately but together as debris, as it is impossible to evaluate and quantify them individually. After using any method mentioned previously, remnants and debris of gutta-percha in addition to sealer remnants can still be present inside root canal. Thus, the following is suggested: • Paper Point and gutta percha solvent (fig.85-86): - Drying solvent-filled canals with paper points is known as “wicking” and is always the final step of guttapercha removal. - The wicking action is essential in removing residual gutta-percha and sealer out of fins, cul-de-sacs, and aberrations of the root canal systems.

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- In this technique, after the bulk of gutta percha filling is removed, the canal is flushed with chloroform and the solution is then absorbed and removed with appropriately-sized paper points. - Paper points “wick” by pulling dissolved materials laterally into the shaped canal. - Following chloroform wicking procedures, the canal is liberally flushed with 70% isopropyl alcohol and wicked to further encourage the elimination of chemically softened gutta-percha residues. - Frequent replenishment of the solvent should be used, and when the last loose-fitting instrument is removed clean, the canal is flooded with the solvent, which then acts as an irrigant. The solvent is then removed with paper points. Note that remaining gutta-percha and sealer are also removed during a crown-down instrumentation approach while using appropriate irrigants (The effectiveness of the debridement may be enhanced by combining sodium hypochlorite with ultrasonic activation). • Removal of hard sealers: It should be noted that there exists a glass ionomer-based endodontic sealer & bioceramic sealers that are used in conjunction with gutta-percha. These sealers are virtually insoluble in both chloroform and halothane, and must be retreated by removing the gutta-percha and then by using ultrasonics to debride the canal walls. Conventional retreatment techniques are not always able to fully remove these hard sealers.

Figure 74 The flutes of a Hedström file make it suitable for engaging GP Figure 75 Smaller sized Hedström files (e.g. 10 and 15) should used in the apical portion of the

Figure 76 Protaper retreatment files D1, D2 , and D3

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Figure 77 Nickeltitanium rotary Profile thermoplasticizing and removing gutta-percha.

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A

B

C

D

E

F

Figure 78 rotary retreatment files method for removal of gutta percha. A) Removal of coronal obturation material with ProTaper D1. B) Removal of middle obturation material with ProTaper D2. C) Removal of apical obturation material with ProTaper D3. D) If an obstruction is encountered, the instruments must not be forced apically. A radiograph is taken to verify the cause of the blockage. E) The apical part of the canal is negotiated with precurved stainless steel hand files, and the working length is established. F) The apical part of the canal is prepared and cleaned.

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Figure 79 note the effect of chemical solvents on gutta percha.

Figure 81 small endosonic file can be used for removal of gutta percha.

Figure 80 Solvents most commonly employed for removal of gutta-percha root fillings.

Figure 82 poorly adapted and ill-fitting obturation can be easily removed using hand files.

Figure 83 Removal of overextended gutta-percha using small H file.

Figure 84 XP-3D Shaper rotary file used to remove overextended gutta percha.

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Figure 85 the wicking procedure. The pulp chamber is filled with solvent and a paper point absorbs the residual sealer. Note the Cleanliness of the pulp chamber and canals before obturation.

Figure 86 wicking procedure. As we move from left to right, paper points introduced into the canal system remove remaining remnants of gutta-percha until none of the solvent is left.

Removal of Carrier based Gutta-Percha Obturators Successful removal in these cases is enhanced by recognizing that the carrier is frozen in a sea of hardened guttapercha. The nature of the carrier will determine the method used and complexity of the retrieval. There are three types of carriers found in these systems: metal (stainless steel or titanium), plastic, and modified gutta-percha core. It is advantageous to determine prior to initiating treatment if there is a solid core obturation in the root-filled tooth. Unfortunately, in most instances, the clinician finds that they are dealing with a carrier-based obturator after initial access to the pulp chamber. This is why, as was stated in an earlier section, careful access and probing of the root filling material is necessary when entering a canal. If there is a carrier, it will be detected as either a metallic structure embedded in the gutta-percha mass or a black or gray spot indicating a plastic or modified gutta percha carrier (fig.87). Potential problem with retrieval is present if the carrier has been overextended beyond the apical foramen during the previous root canal treatment. This overextension may make it prone to separation and unable to be retrieved, potentially resulting in the need for apical surgery.

Removal of plastic carriers • In large or oval canals, they are removed using either:

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CHAPTER 9 perio-endo lesions Contents Why perio-endo lesions could happen

Causes of individual endodontic and periodontal diseases

Pathogenesis and types of perio-endo lesions

Differential diagnosis and management of perio-endo lesions 504

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DEFINITION The endo-perio lesion is a lesion occurs due to inflammatory products found in varying degrees in both periodontium and pulpal tissues in the same dental element.

WHY ENDO-PERIO LESIONS COULD HAPPEN? The endodontium and periodontium are closely related and diseases of one tissue may lead to the involvement of the other. It is a known fact that endodontic disease can cause significant damage to the periodontal tissue apparatus, but the effect of periodontal inflammation on dental pulp is controversial and conflicting studies abound. It has been suggested that periodontal disease has no effect on the pulp before it involves the apex or cementum protecting dentinal tubules is lost. There are 2 types of Channels of Communication between the endodontium and periodontium: 1)

Anatomical (developmental) communications (fig.1) - Apical foramen: it is the most direct route of communication to the periodontium. The apical foramen is the main route of communication between the pulp and the periodontal tissues. In case of pulp infection, the bacteria and their by-products may exit through the apical foramen causing periapical inflammation. In certain cases, the associated periapical tissue destruction can spread coronally and involve the marginal periodontium. On the other hand, in case of severe periodontal disease with deep periodontal pockets the vice versa may happen. - Accessory and lateral canals: Lateral and accessory canals, mainly in the apical area and in the furcation of molars, also connect the dental pulp with the periodontal ligament. It is difficult to identify lateral canals on radiographs. These can be identified by isolated defects on the lateral surface of roots or by postobturation radiographs showing sealer puffs.

2)

- Dentinal tubules: Tubular communication between the pulp and periodontium may occur when dentinal tubules become exposed to the periodontium by the absence of overlying cementum. Pathological and iatrogenic communications (fig.2) - Idiopathic resorption (internal and external resorption) that lead to pathological perforation of root. - Perforation resulted from caries invading through the floor of the pulp chamber. - Iatrogenic perforation: Perforation creates an artificial communication between the root canal system and periodontium. - Vertical root fracture.

Figure 1 The normal pathways of communication between the endodontium and the periodontium (1 -the apical foramen, 2, 3 - lateral and accessory canals, 4 - dentinal tubules).

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Figure 2 Pathological and iatrogenic communications

CAUSES OF INDIVIDUAL ENDODONTIC AND PERIODONTAL DISEASES To identify the original cause of perio-endo lesions, you should first know the etiology of individual endodontic and periodontal diseases. The major causes of endodontic disease include deep Caries and exposed pulp, deep restorative procedures close to pulp, traumatic injuries and Poor root canal treatment. The major causes of periodontal disease include accumulated dental plaque and calculus, trauma from occlusion, overhanging restorations & systemic conditions such as uncontrolled diabetes and heavy smoking.

PATHOGENESIS AND TYPES OF PERIO-ENDO LESIONS Endodontic etiology (fig.3-6) Noxious agents present in the root canal system of necrotic tooth communicate with the periodontium resulting in either • Primary endodontic lesion with pseudo periodontal lesion (suppuration / drainage through gingival crevice): A periapical lesion may perforate the cortical bone close to the apex, elevate the periosteum and overlying soft tissues, and drain into the gingival sulcus, and form pseudopockets that simulate periodontal disease without necessarily permanent damaging of the cementum and its fibers. • Primary endodontic lesion with secondary true periodontal lesion (pocket and bone destruction): If the acute periapical drainage becomes chronic and drainage through the gingival sulcus continues a downgrowth of epithelium along the tract can result in a periodontal pocket in which secondary periodontal disease may complicate the lesion (Plaque and calculus gets deposited in the pocket, due to the long-term existence of the pathology and the defect with subsequent advancement of the periodontal disease). The routes of communication in these cases can be ordered decreasingly as follows: apical foramen > accessory and lateral canals > dentinal tubules.

Periodontal etiology (fig.7-8) Accumulation of dental plaque and calculus on the external root surfaces result in either • Primary periodontal lesion with pseudo-endodontic lesion (tooth hypersensitivity): Progression of periodontal lesion apically cause some pulpal degenerative changes (pulp is still vital).

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• Primary periodontal lesion with secondary true endodontic lesion (irreversible pulpitis or pulp necrosis): Periodontal disease causes a resultant pulpal necrosis as it progresses apically either because - Bacterial plaque involves the main apical foramina, compromising the vascular supply. - Or the exposure of dentinal tubules by the removal of cementum due to rigorous scaling and rootplanning for the treatment of periodontal disease will allow bacterial invasion of the tubules.

Combination of endodontic and periodontal etiologies (fig.9) • Both an endodontic and periodontal lesion developing independently and progressing concurrently which meet and merge at a point along the root surface resulting in true combined endo-perio lesion (e.g. a coronally progressing endodontic disease joins an infected periodontal pocket progressing apically). • These lesions are often indistinguishable from an advanced primary endodontic lesion with secondary periodontal involvement and/or a primary periodontal lesion with secondary endodontic involvement. • True combined endodontic-periodontal disease occurs with less frequency (very rare).

Iatrogenic etiology Usually endodontic lesions produced as a result of treatment modalities that if ignored or poorly managed can lead to secondary periodontal lesion. These include root perforations, overfilling of root canals, coronal leakage and vertical root fractures: • Root perforations: At the site of perforation (furcation, pulpal floor, lateral or apical root canal walls etc…), an inflammatory reaction in periodontal ligament produces a degradation of surrounding tissues and formation of a lesion which can progress as a conventional primary endodontic lesion with secondary periodontal lesion. Closer is the perforation to gingival sulcus, greater is the chances of apical migration of gingival epithelium in initiating a periodontal lesion (fig.10-11). • Overfilling of root canals: The overfilling of root canals produces a lesion in exactly the same way as the lesion originating adjacent to the apical foramen. • Coronal leakage: exposure of root canals to the oral environment allowed coronal leakage to occur, and in some cases along the entire length of the root canal thus initiating lesion similar to primary endodontic lesion. • Vertical root fractures: it is very serious issue that make the tooth hopeless. Vertical root fracture is a slow dynamic process, and after an incomplete fracture is exposed to masticatory forces for a long time, it may propagate to become a complete fracture. Once it occurs, a pathological communication result between root canal system and periodontium resulting in severe secondary periodontal lesion that cannot be treated (The fracture site provides a portal of entry for irritants from the root canal system to the surrounding periodontal ligament). The periodontal destruction resulting from the communication of the root canal space with the periodontium and its contamination is a slow process. Thus it may take a long time for the signs and symptoms to be clinically evident.

Figure 3 Routes of endodontic infection to periodontium through the apex or lateral canals of a tooth.

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Figure 4 Primary endodontic lesion

Figure 5 primary endodontic lesion with secondary periodontal lesion. Note the white arrow indicates caries that lead eventually to pulp necrosis.

Figure 6 Primary endodontic disease with subsequent advancement of the periodontal disease

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Figure 7 Primary periodontal lesion

Figure 8 primary periodontal lesion with secondary endodontic lesion.

Figure 9 True combined lesion

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Figure 11 Radiograph of uppe lateral incisor with fiber post placed outside the root canal space, resulting in a midroot perforation and severe lateral periodontal bone loss. The tooth as extracted

Figure 10 Mandibular molar showing endodontic filling material extending into the furcation and along the lateral root surface because of strip perforation that result in destruction of periodontal tissues.

DIFFERENTIAL DIAGNOSIS AND MANAGEMENT OF PERIO-ENDO LESIONS Differential diagnosis The differential diagnosis of endodontic and periodontal diseases can sometimes be difficult but it is of vital importance to make a correct diagnosis so that the appropriate treatment can be provided (e.g. the most important factor in the treatment is a correct diagnosis).

Common criteria of all perio endo lesions The following signs and symptoms can occur in any perio-endo lesion: • Pain (a more chronic response may sometimes occur without pain) • Swelling • Sinus tract in adjacent gingival or vestibular tissues • Pus exudate & bleeding on probing • Pocket formation • Tooth mobility • Lateral or apical radiolucency on radiograph

Individual criteria of perio endo lesions Primary endodontic perio endo lesions: • Pain →

pain of endodontic origin is usually acute in onset and severe. Pulpal pain can be spontaneous and

in the early stages localization is often difficult. Over time the symptoms tend to intensify and the spread of inflammation to the periodontal tissues helps in localizing the pain. • Swelling → endodontic infections can cause swellings in the mucobuccal fold, which in turn may spread to the facial planes. • Vitality tests →

non-vital teeth with no pulp response to cold or electric tests and possible response to heat.

• Gutta percha tracing test →

when sinus opening is present, The gutta percha cone is inserted through the

sinus opening and gently manipulated along the sinus tract till resistance is met. A radiograph is taken to

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CHAPTER10 Pulp thearpy in childern Contents Difference between primary and permanent pulps

Clinical assessment and general considerations

Pulp therapy for primary teeth

Pulp thearpy for young permenant teeth 522

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DIFFERENCE BETWEEN PRIMARY AND PERMANENT PULPS • Pulp chamber in a deciduous teeth is larger compared to the crown size. Mesial pulp horns extend closer towards outer surface. This increases the risk of pulp exposure during cavity preparation. • Ribbon shaped root canals (difficult to instrument). • Thin walls of root canals (relative increase risk of perforation). • Physiological apical root resorption (wide open apical regions). • Close proximity of the permanent tooth germ to the apex of primary tooth (relative risk of damaging successor tooth). • Accessory canals extend from pulpal chamber to the interradicular area at the furcation. Therefore the radiographic changes (radiolucency that is caused due to widening of periodontal space and resorption of bone) is seen in the interradicular region rather than the periapical region. Also, many lateral and furcal communications result in difficulty to clean and obdurate). • Deciduous pulp is highly vascularized. Thus it exhibits typical inflammatory response to any irritating stimulus, and is at high-risk for internal and external resorption. Localization of infection and inflammation is very poor for the same reason.

Longitudinal section of permanent and deciduous molars

CLINICAL ASSESSMENT AND GENERAL CONSIDERATIONS Indications of pediatric endodontics Pain • Symptoms of severe, prolonged, spontaneous or nocturnal pain suggest irreversible pulpitis or a dental abscess • Dental pain will frequently resolve once a sinus tract establishes drainage, and thus relieves pressure. In these cases, the underlying pathology is still present and must be resolved, despite the lack of obvious discomfort (history of repeated need for analgesics is also suggestive of pulp necrosis).

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Coronal discoloration: Tooth that is non-vital tend to have a darker color (fig.1). Swelling Intraoral or extra oral swelling are indicators of pulp necrosis and abscess formation. Sometimes one of the canals may contain inflamed but vital pulp. From the treatment point of view the tooth is considered non-vital. Intraoral swelling • It is usually apparent on the buccal aspect of the alveolus (fig.2). There is less bone on the buccal aspect than on the lingual or palatal side, through which the inflammatory products from the periapical or inter radicular regions penetrate, taking the path of least resistance. The pressure of the swelling will eventually result in spontaneous drainage if treatment is not rendered • Drainage occurs through the formation of fistula, usually seen at the junction of the attached gingiva and alveolar mucosa, corresponding to the site adjacent to the interradicular region. The tissue adjacent to the fistula is inflamed. Once the fistula is formed, drainage is established and lesion is seldom acute and becomes a chronic lesion (fig.1). Extra oral swelling/cellulitis • It is due to the spread of exudate into various spaces along the fascial planes. • In the mandibular arch, submandibular region is commonly involved (fig.3) and in the maxillary arch, the swelling may extend up to the infraorbital margin, may involve the upper eye lid or may be so severe as to close the child’s eye (fig.4). The drainage occurs through the path of least resistance, which is through the skin.

Mobility & palpation • Inappropriate tooth mobility, tenderness to palpation or a sensation of occlusal interference also suggests abscess formation. • Note that palpation should be used instead of percussion in children.

Other clinical signs • Marginal ridge fracture in a primary tooth is suggestive of carious pulpal involvement (Approximal caries where 2/3 of the marginal ridge has been destroyed) (fig.5). • Fracture of the occlusal triangular ridges or carious undermining of the cusps in pit and fissure caries also suggests carious involvement (Occlusal caries extending more than 4mm in depth) (fig.6). • Persistent symptoms occurring soon after placement of a restoration indicate pulpal pathology. Lack of coronal seal will inevitably lead to pulpal pathology. • Pulp polyp: Hyperplastic pulpitis is a form of irreversible pulpitis that originates from overgrowth of a chronically inflamed young pulp onto the occlusal surface. It occurs in tooth with extensive carious exposure of the pulp, associated with long standing, low grade irritation. It is usually asymptomatic but pain may be present during mastication (fig.7). Notes ✓ Pulp vitality tests, either thermal (cold or hot tests) or electrical, are of little value in primary teeth. ✓ Recording the blood flow in the pulp is an accurate indicator with regards to its status. Laser Doppler Flow meter and transmitted light photoplethysmography are devices used for the same purpose. They transmit a laser or light beam through the crown of the tooth and the signal is picked by an optical fiber and photocell from the other side of the tooth.

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Figure 1 discoloration, pulp necrosis, and sinus tract related to tooth upper A. note that sinus seen at the junction of the attached gingiva and alveolar mucosa.

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Figure 2 intraoral swelling due to abscess related to upper primary incisor.

Figure 3 (A) Six-year-old male with facial welling caused by deep carious lesion and infection involving Lower E. (B) Lateral view of same patient, showing dness and extent of cellulitis. (C) Preoperative Periapical radiograph taken

B Figure 4 (A) Five-yearold male with facial swelling caused by a primary maxillary tooth. Note swelling involving the left eye. (B) Clinical view of grossly decayed teeth upper D & E(C) Periapical radiograph of affected teeth.

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Figure 5 Loss of marginal ridge of first primary molar suggests carious pulpal involvement.

Figure 6 Undermined triangular ridge or cusp suggests carious pulpal involvement.

Figure 7 Hyperplastic pulpitis (pulp polyp) seen in the pulp of a primary molar.

Factors that can modify treatment planning (pulp therapy or extraction) Medical factors The following medical conditions are considered poor candidates for pulp therapy and must be treated by extraction: • Congenital cardiac disease. Patients who are considered to be at risk of bacterial endocarditis should be free of oral infection and any primary tooth with clinical signs of infection should be extracted. • Immunosuppressed patients and those with poor healing potential (e.g. poorly controlled diabetic patients & oncology patients). The following medical conditions should be managed by pulp therapy (instead of extraction): • Bleeding disorders and coagulopathies • Hypodontia (i.e. ectodermal dysplasia): it is necessary to maintain a primary tooth without a successor (fig.8).

Behavioral factors Effective endodontic treatment requires a high level of patient compliance. If a child is unable to cooperate with pre-treatment diagnostic procedures including radiographs, they are unlikely to cope with complex endodontic and associated restorative procedures. Where cooperation cannot be obtained or is fragile, it is reasonable to consider the elective use of general anesthesia, or even elective extraction of the affected tooth rather than complex endodontic and restorative procedures. Note that the use of the rubber dam to isolate the tooth undergoing treatment, and to protect the patient from instruments and medicaments is essential.

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Difference between Pulpal treatment plan in Young Permanent Teeth & in primary teeth • Spontaneous pain and/or provoked pain which continues long after the stimulus is removed (over shoot) are usually associated with extensive, irreversible pulpal inflammation extending into the root canals. Although in primary teeth pulpectomy is the treatment of choice in this cases, immature permanent teeth should be carefully considered for pulpotomy, apexogenesis, or even regenerative treatment because of the destructive nature of losing vital pulp functions. • The interpretation of radiographs of young, immature permanent teeth can be difficult, due to their normally large and open apex and radiolucent apical papilla. Less experienced dentists treating these teeth should avoid confusing pathologic changes with normal apical anatomy. • It is Important to remember that the root canals of permanent teeth are wider in the bucco-lingual plane than the mesio-distal. Therefore it is difficult to determine the extent of apical closure in a regular radiograph showing only the mesio-distal plane.

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Chapter 10. Pulp thearpy in childern

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The first situation: vital Pulp Therapy for Normal Pulp or Reversible Pulpitis without Pulp Exposure The condition can be managed using Indirect Pulp capping (IPC) (fig.75-80) • Caries excavation and indirect pulp treatment for immature permanent teeth is similar to that of primary teeth. • The indication for IPT should be limited to teeth without signs of irreversible pulpitis.

Figure 75 Preoperative radiograph of lower second molar with deep caries and incomplete closure of root apex

Figure 76 Rubber dam placement

Figure 77 Initial excavation with #8 round bur and slow speed handpiece.

Figure 78 Caries excavation nearly completed

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Figure 79 placement of light cured resinmodified glass ionomer over the remaining caries.

Figure 80 final restoration with composite.

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References Textbooks

❖ The Principles of Endodontics THIRD EDITION ❖ Cohen’s Pathways of the Pulp: TWELFTH EDITION ❖ Clinical success in Endodontic Retreatment ❖ Endodontic Radiology, Second Edition ❖ Endodontic Irrigation: Chemical Disinfection of the Root Canal System ❖ Common Complications in Endodontics: Prevention and Management ❖ Current Therapy in Endodontics ❖ Endodontic Treatment, Retreatment, and Surgery: Mastering Clinical Practice ❖ ENDODONTICS: ARNALDO CASTELLUCCI MD, DDS (Volume 1&2) ❖ Endodontics: Principles and Practice; Dr. Arvind Shenoy, MDS & Dr. Kundabala Mala, MDS ❖ Endodontics: Principles and Practice 6th Edition (Mahmoud Torabinejad, Ashraf Fouad, Shahrkh Shabahang) ❖ Ingle's Endodontics 7th Edition ❖ Retreatments Solutions for Periapical Diseases of Endodontic Origin ❖ The Guidebook to Molar Endodontics

❖ Textbook of Endodontics: Fourth Edition: Nisha Garg& Amit Garg ❖ Practical Lessons in Endodontic Treatment

❖ Harty’s endodontics in clinical practice: Sixth edition

❖ Endodontics: Problem-Solving in Clinical Practice

❖ Clinical Cases in Endodontics ❖ A Concise Guide to Endodontic Procedures ❖ ENDODONTICS: Fourth edition; Kishor Gulabivala & Yuan-Ling Ng ❖ Clinical operative dentistry with illustrated colour atlas ❖ Handbook of Clinical Techniques in Pediatric Dentistry ❖ Principles and Practice of PEDODONTICS ❖ Pediatric Endodontics: Current Concepts in Pulp Therapy for Primary and Young Permanent Teeth ❖ Pediatric Dentistry Infancy Through Adolescence SIXTH EDITION ❖ Paediatric Cariology ❖ Paediatric dentistry FIFTH EDITION; Oxford University Press

Websites ❖ American Association of Endodontists ❖ Inside Dentistry ❖ Dentistry Today ❖ International academy for rotary endodontics ❖ Europe PMC plus ❖ STYLE ITALIANO endodontics ❖ Endomontreal ❖ Intech Open ❖ Case masters ❖ Endodontic practice US ❖ The Journal of the American Dental Association

❖ Research Gate ❖ Indian Journal of Conservative and Endodontics ❖ Endodontic topics ❖ Restorative dentistry & endodontics (RDE) ❖ Case reports in dentistry: Hindawi ❖ Dental Update ❖ Saudi Journal of Oral and Dental Research ❖ ADVANCED ENDODONTICS www.endoruddle.com ❖ Iowa Research Online ❖ Journal of IMAB ❖ International Endodontic Journal ❖ Pocket Dentistry

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