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PRINCIPLES and
BIOMECHANICS of ALIGNER TREATMENT
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PRINCIPLES and
BIOMECHANICS of ALIGNER TREATMENT Ravindra Nanda, BDS, MDS, PhD Professor Emeritus Department of Orthodontics University of Connecticut Health Center Farmington, Connecticut, USA
Tommaso Castroorio, DDS, PhD, Ortho. Spec. Department of Surgical Sciences, Postgraduate School of Orthodontics Dental School, University of orino orino, taly
Francesco Garino, MD, Ortho. Spec. Private Practice orino, taly
Kenji Ojima, DDS, MDSc Private Practice oyo, apan
Elsevier 3251 Riverport Lane St. Louis, Missouri 63043 PRINCIPLES AND BIOMECHANICS OF ALIGNER TREATMENT, FIRST EDITION Copyright © 2022 by Elsevier, Inc. All rights reserved.
ISBN: 978-0-323-68382-1
No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).
Notices Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds or experiments described herein. Because of rapid advances in the medical sciences, in particular, independent verication of diagnoses and drug dosages should be made. To the fullest extent of the law, no responsibility is assumed by Elsevier, authors, editors or contributors for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. ISBN: 978-0-323-68382-1
Content Strategist: Joslyn Dumas Content Development Manager: Ellen Wurm-Cutter Content Development Specialist: Rebecca Corradetti Publishing Services Manager: Shereen Jameel Project Manager: Nadhiya Sekar Design Direction: Patrick Ferguson Printed in India Last digit is the print number:
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To Catherine, for her love, support, inspiration, and encouragement. RN
To Katia, for showing me what love is and for keeping my feet on the ground. To Alessandro, Matilda, and Sveva, because you made the world a brighter place. To my friends, rancesco and Keni, for your passion, enthusiasm, commitment, and support you are always an eample to follow. To avi, for your trust and friend ship, for your guidance and leadership you have trans lated a vision into reality. t was a wonderful ourney with you thanks for your time and for sharing your eperience. TC
would like to dedicate this book to all my family with a special thought to my dad, mentor and a visionary, who shared with me a passion in aligner orthodontics for years. FG
My thanks to rancesco and Tommaso for sharing their friendship with me over so many years. The time spent writing this book with avi was amaing, like a dream for me. am truly grateful to my family for all of their support. KO
Contributors Masoud Amirkhani, PhD
Aldo iancotti, DDS MS
Institute for Experimental Physics Ulm University Ulm, Germany
Researcher and Aggregate Professor Department of Clinical Sciences and ranslational edicine University of ome “or ergata” ome, taly
Sean K. Carlson, DMD, MS Associate Professor Department of Orthodontics School of Dentistry, University of the Pacic San Francisco, California, USA
Tommaso Castroorio, DDS, PhD, Ortho. Spec. Researcher and Aggregate Professor Department of Surgical Sciences, Postgraduate School of Orthodontics Dental School, University of orino orino, taly Orthodontics Unit San Giovanni attista ospital orino, taly
uan Palo ome Arano, DDS, MSc Associate Professor Orthodontics Program Universidad Autonoma de aniales aniales, Colomia
Mario reco, DDS, PhD Visiting Professor University of ’Auila ’Auila, taly Visiting Professor University of Ferrara Ferrara, taly
Chisato Dan, DDS
uis uanca, DDS, MS, PhD
Private Practice Smile nnovation Orthodontics oyo, apan
Research Associate Department of Orthodontics University of Geneva Geneva, Siterland
Iacopo Ciof, DDS, PhD Associate Professor Division of Graduate Orthodontics and Centre for ultimodal Sensorimotor and Pain esearch Faculty of Dentistry University of oronto oronto, Ontario, Canada
Daid Couchat, DDS, Ortho. Spec. Private Practice Cainet d’Orthodontie du dr Couchat arseille, France
osef Kucˇera, MDr., PhD Assistant Professor Department of Orthodontics Clinic of Dental edicine First edical Faculty Charles University Prague, Cech epulic Lecturer Department of Orthodontics Clinic of Dental edicine Palacý University Olomouc, Cech epulic
ae lkhol, DDS Senior Physician Department of Orthodontics Ulm University Ulm, Germany
rancesco arino, MD Ortho. Spec. Private Practice Studio Associato dottri Garino orino, taly
vi
ernd . apatki, DDS, PhD Department Head and hair Department of Orthodontics Ulm University Ulm, Germany
Contributors
vii
uca omardo, DDS, Ortho. Spec.
Simone Parrini, DDS, Ortho. Spec.
hairman and Professor Postgraduate School of Orthodontics University of Ferrara Ferrara, taly
Research Associate Department of Surgical Sciences, Postgraduate School in Orthodontics Dental School, University of orino orino, taly
Tianton ou, DMD, MSc Division of Gradual Orthodontics and Centre for ultimodal Sensorimotor and Pain esearch Faculty of Dentistry University of oronto oronto, Ontario, Canada
Serena aera, DDS, PhD, Ortho. Spec. Research Associate Department of Surgical Sciences, Postgraduate School in Orthodontics Dental School, University of orino orino, taly
Kam Malekian, DDS, MSc Private Practice Clinica io adrid, Spain
ianluca Mampieri, DDS, MS, PhD Researcher and Aggregate Professor Department of Clinical Sciences and ranslational edicine University of ome “or ergata” ome, taly
doardo Mantoani, DDS, Ortho. Spec. Research Associate Department of Surgical Sciences, Postgraduate School in Orthodontics Dental School, University of orino orino, taly
ariele ossini, DDS, PhD, Ortho. Spec. Research Associate Department of Surgical Sciences, Postgraduate School in Orthodontics Dental School, University of orino orino, taly
addah Saouni, DDS, Ortho. Spec. Private Practice Cainet d’Orthodontie du dr Saouni andol ivage Sanarysurer, France
Sila Schmidt, DDS Department of Orthodontics Ulm University Ulm, Germany
Io Marek, MDr., PhD Assistant Professor Department of Orthodontics Clinic of Dental edicine Palacý University Oloumouc, Cech epulic onsultant Department of Orthodontics Clinic of Dental edicine First edical Faculty Charles University Prague, Cech epulic
ör Schare, DDS, PhD, Ortho. Spec. Private Practice ieferorthopädische Prais Dr örg Schare Cologne, Germany
iuseppe Siciliani, MD, DDS hairman and Professor School of Dentistry University of Ferrara Ferrara, taly
Ali Tassi, Sc, DDS, MClD Ortho aindra anda, DS, MDS, PhD Professor Emeritus Division of Orthodontics Department of Craniofacial Sciences University of Connecticut School of Dental edicine Farmington, Connecticut, USA
Assistant Dean and hair Division of Graduate Orthodontics Schulich School of edicine and Dentistry he University of estern Ontario ondon, Ontario, Canada
ohnn Tran, DMD, MClD Keni Oima, DDS, MDSc Private Practice Smile nnovation Orthodontics oyo, apan
Division of Graduate Orthodontics Schulich School of edicine and Dentistry he University of estern Ontario ondon, Ontario, Canada
viii
Contributors
laio rie, DDS, MDentSc
enedict ilmes, DDS, MSc, PhD
onn rthodontics Alumnianda rthodontics Endoed hair Program Director and Chair Division of Orthodontics Department of Craniofacial Sciences University of Connecticut School of Dental edicine Farmington, Connecticut, USA
Professor Department of Orthodontics University of Düsseldorf Düsseldorf, Germany
Foreword Aligners represent the new frontier in the art and science of orthodontics. This new frontier offers new opportunities and challenges, but also requires the need for additional knowledge. A rethinking of biomechanics and force delivery concepts is needed along with the role of materials used for aligners. There is a need for combining established concepts with new tools and technologies which aligner treatment requires. When considering new methodologies, orthodontists should always remember that technology is a tool and not the goal. Diagnosis, treatment plan, and biomechanics are always the key elements of successful treatment, regardless of the treatment methodology. Aligner orthodontics is quite different than traditional methods with brackets and wires. orce delivery with aligners is through plastic materials. Thus, the knowledge of the aligner materials, physical properties, attachment design, and the sequentialiation protocol is crucial for treatment of malocclusions. t is also imperative to understand limitations of aligner treatment and how to overcome them with the use of miniscrews and auiliaries.
Aligner treatment requires new knowledge the number of clinical and scientic reports about all the different aspects of aligner orthodontics is increasing year by year. This book represents an up-to-date summary of the available research in the eld as well as a clinical atlas of treated patients based on the current evidence. We have made an attempt to provide benchmark for clinicians, researchers, and residents who want to improve their skills in aligner orthodontics. We would like to epress our great appreciation to all the friends and colleagues who have contributed to this book. t was a pleasure to work with all these talented orthodontists. We would like to say thank you to the lsevier team for their support, patience, and guidance during the challenging ovid pandemic. avindra anda Tommaso astroorio rancesco arino eni ima
ix
Contents 1 Diagnosis and Treatment Planning in the Three-Dimensional Era 1
12 The rid Approach in Class Malocclusions Treatment 13
TOMMASO CASTROFLORIO, SEAN K. CARLSON, and FRANCESCO GARINO
FRANCESCO GARINO, TOMMASO CASTROFLORIO, and SIMONE PARRINI
2 Current Biomechanical Rationale Concerning Composite Attachments in Aligner Orthodontics 13 JUAN PABLO GOMEZ ARANGO
13 Aligners and mpacted Canines
14 Aligner Orthodontics in Prerestoratie Patients 1
3 Clear Aligners: Material tructures and Properties 3
KENJI OJIMA, CHISATO DAN, and TOMMASO CASTROFLORIO
MASOUD AMIRKHANI, FAYEZ ELKHOLY, and BERND G. LAPATKI
4 nuence o ntraoral actors on Optical and Mechanical Aligner Material Properties 3
15 oncompliance pper Molar Distaliation and Aligner Treatment or Correction o Class Malocclusions 1 BENEDICT WILMES and JÖRG SCHWARZE
FAYEZ ELKHOLY, SILVA SCHMIDT, MASOUD AMIRKHANI, and BERND G. LAPATKI
5 Theoretical and Practical Considerations in Planning an Orthodontic Treatment ith Clear Aligners TOMMASO CASTROFLORIO, GABRIELE ROSSINI, SIMONE PARRINI
6 Class Malocclusion
16 Clear Aligner Orthodontic Treatment o Patients ith Periodontitis TOMMASO CASTROFLORIO, EDOARDO MANTOVANI, and KAMY MALEKIAN
17 urger irst ith Aligner Therap
3
FLAVIO URIBE and RAVINDRA NANDA
1
MARIO GRECO
7 Aligner Treatment in Class Malocclusion Patients TOMMASO CASTROFLORIO, WADDAH SABOUNI, SERENA RAVERA, and FRANCESCO GARINO
8 Aligners in Etraction Cases
1
EDOARDO MANTOVANI, DAVID COUCHAT, TOMMASO CASTROFLORIO
18 Pain During Orthodontic Treatment: Biologic Mechanisms and Clinical Management TIANTONG LOU, JOHNNY TRAN, ALI TASSI, and IACOPO CIOFFI
19 Retention and tailit olloing Aligner Therap
3
JOSEF KUČERA and IVO MAREK
KENJI OJIMA, CHISATO DAN, and RAVINDRA NANDA
9 Open-Bite Treatment ith Aligners
20 Oercoming the imitations o Aligner Orthodontics: A rid Approach
ALDO GIANCOTTI and GIANLUCA MAMPIERI
10 Deep Bite
LUCA LOMBARDO and GIUSEPPE SICILIANI
1
nde
LUIS HUANCA, SIMONE PARRINI, FRANCESCO GARINO, and TOMMASO CASTROFLORIO
11 nterceptie Orthodontics ith Aligners TOMMASO CASTROFLORIO, SERENA RAVERA, and FRANCESCO GARINO
x
11
1
Diagnosis and Treatment Planning in the Three-Dimensional Era TOMMASO CASTROFLORIO, SEAN K. CARLSON, and FRANCESCO GARINO
Introduction rthodontics and dentofacial orthopedics is a specialty area of dentistry concerned with the supervision, guidance, and correction of the growing or mature dentofacial structures, including those conditions that reuire movement of teeth or correction of malrelationships and malformations of their related structures and the adustment of relationships between and among teeth and facial bones by the application of forces andor the stimulation and redirection of functional forces within the craniofacial comple. To accurately diagnose a malocclusion, orthodontics has adopted the problem-based approach originally developed in medicine. very factor that potentially contributes to the etiology and that may contribute to the abnormality or inuence treatment should be evaluated. nformation is gathered through a medical and dental history, clinical eamination, and records that include models, photographs, and radiographic imaging. problem list is generated from the analysis of the database that contains a network of interrelated factors. The diagnosis is established after a continuous feedback between the problem recognition and the database Fig. .. ltimately, the diagnosis should provide some insight into the etiology of the malocclusion. rthodontics diagnosis and treatment planning are deeply changing in the last decades, moving from two-dimensional hard tissue analysis and plaster cast review toward soft tissue harmony and proportions analyses with the support of three-dimensional technology. detailed clinical eamination remains the key of a good diagnosis, where many aspects of the treatment plan reveal themselves as a function of the systematic evaluation of the functional and aesthetic presentation of the patient. The introduction of a whole range of digital data acuisition devices cone-beam computed tomography T, intraoral and desktop scanner and , and face scanner F, planning software computer-assisted design and computer-assisted manufacturing software, new aesthetic materials, and powerful fabrication machines milling machines, printers is changing the orthodontic profession Fig. .. s a result, clinical practice is shifting to virtual-based workows. Today it is common to perform virtual treatment planning and to translate the plans into treatment eecution with digitally driven appliance manufacture and placement using various techniues from
printed models, indirect bonding trays, and custom-made brackets to robotically bend wires or aligners. Furthermore, it is becoming possible to remotely monitor treatment and to control it.5 The introduction of aligners in the orthodontics eld led the digital evolution in orthodontics. The two nouns evolution and revolution both refer to a change; however, there is a distinctive difference between the change implied by these two words. volution refers to a slow and gradual change, whereas revolution refers to a sudden, dramatic, and complete change. hat has been claimed as the “digital revolution” in orthodontics should be claimed as the “digital evolution” in orthodontics. rthodontics and biomechanics have always had the same denitions, and we as clinicians should remember that technology is an instrument, not the goal. This differentiates orthodontists from marketing people. The diagnosis and problem list is the framework that dictates the treatment obectives for the patient. nce formulated, the treatment plan is designed to address those obectives. n aligner orthodontics, software displays treatment animations, helping the clinician to visualie the appearance of teeth and face that is desired as treatment outcome; however, those animations should be deconstructed by the orthodontist frame by frame or stage by stage, to dene how to address the treatment goal from mechanics to seuence. nly an accurate control of every single stage of the virtual treatment plan can produce reliable results. s usual, it is the orthodontist rather than the techniue itself that is responsible for the treatment outcome. ontemporary records should facilitate functional and aesthetic evaluation of the patient.
Intraoral Scans and Digital Models s are uickly replacing traditional impressions and plaster models. These scanners generally contain a source of risk for inaccuracy because multiple single images are assembled to complete a model. ecent studies, however, have shown that the trueness and precision of s of commercially available scanning systems are ecellent for orthodontic applications. igital models are as reliable as traditional plaster models, with high accuracy, reliability, and reproducibility Fig. .. 1
2
Principles and Biomechanics of Aligner Treatment
Database
Models Intraoral scan
Clinical examination Chief complaint Medical history Dental history Extraoral exam Intraoral exam Functional exam
Photographs 3-D facial scan
Radiographic imaging CBCT
Problems
Problem List
Synthesis and diagnosis
Treatment objectives
Mechanics plan: which movements with which auxiliaries
Staging definition
Treatment prescription
Virtual setup Virtual patient
Treatment re-evaluation
Fig. 1.1 Steps in diagnosis and treatment planning in the digital orthodontics era. (Modied from Uribe FA, Chandhoe TK, Nanda R. Indiidaied orhodoni dianoi. In Nanda R, ed. Esthetics and Biomechanics in Orthodontics. nd ed. S Loi, MO Eeier Sander .
Fig. 1.2 Integration of cone-beam computed tomography data, facial three-dimensional scan, digital models from intraoral scans, and virtual orthodontic setup. Courtesy of dr. Alain Souchet, ulhouse, rance.
1 • iagnosis and Treatment Planning in the Three-imensional ra
3
A
B Fig. 1.3 A igital models and measurements obtained from cone-beam computed tomography data. B igital models and measurements obtained from intraoral scans.
Furthermore, the models can also be used in various orthodontic software platforms to allow the orthodontist to perform virtual treatment plans and eplore various treatment plans within minutes as opposed to epensive and time-consuming diagnostic setups and waups. erforming digital setups not only allows the clinician to eplore a number of treatment options in a simple manner but also facilitates better communication with other dental professionals, especially in cases that reuire combined orthodontic and restorative treatments. The virtual treatment planning also allows for better communication with patients and allows them to visualie the treatment outcome and understand the treatment process.5 Further advantages of virtual models of the dental arches are related to study model analysis, which is an essential step in orthodontic diagnostics and treatment planning. ompared to measurements on physical casts using a
measuring loop andor caliper, digital measurements on virtual models usually result in the same therapeutic decisions as evaluations performed the traditional way. Furthermore, with their advantages in terms of cost, time, and space reuired, digital models could be considered the new gold standard in current practice. igital impressions have proven to reduce remakes and returns, as well as increase overall efciency. The patient also benets by being provided a far more positive eperience. urrent development of novel scanner technologies e.g., based on multipoint chromatic confocal imaging and dual wavelength digital holography will further improve the accuracy and clinical practicability of . ecently near infrared technology has been integrated in . The is the region of the electromagnetic spectrum between . and mm Fig. .. The interaction of specic light wavelengths with the hard tissue of the
4
Principles and Biomechanics of Aligner Treatment
NIRI - A reflective concept of light and its mechanism of action
The iTero Element 5D intraoral scanner uses light of 850nm that penetrates into the tooth structure to produce a NIRI image
NIRI image of a healthy tooth
Image interpretation - Healthy tooth Enamel is mostly transparent to NIRI and appears dark
Dentin is mostly scattering to NIRI and appears bright
Image interpretation - Tooth with caries
ealthy enamel appears dark
roimal carious lesions of the enamel appears bright
A Fig. 1.4 e generation of intraoral scanners ith integrated near infrared I technology. A Itero lement Align Technology, San osé, CA, SA decays detection scheme.
1 • iagnosis and Treatment Planning in the Three-imensional ra
5
B Fig. 1.4, cont’ B Shape Trios Shape AS, Copenhagen, enmar uorescent technology for surface decay detection (left) and I technology for interproimal decay detection (right).
tooth provides additional data of its structure. namel is transparent to due to the reduced scattering coefcient of light, allowing it to pass through its entire thickness and present as a dark area, whereas the dentin appears bright due to the scattering effect of light caused by the orientation of the dentinal tubules. ny interferencespathologic lesionsareas of demineraliation appear as bright areas in a image due to the increased scattering within the region. Therefore provides information regarding possible decays without any -ray eposure. Through the use of digital impression making, it has been determined that laboratory products also become more consistent and reuire less chair time at insertion.
3D Imaging CONE-BEAM COMPUTED TOMOGRAPHY imaging has evolved greatly in the last two decades and has found applications in orthodontics as well as in oral and maillofacial surgery. n medical imaging, a set of anatomic data is collected using diagnostic imaging euipment, processed by a computer and then displayed on a monitor to give the illusion of depth. epth perception causes the image to appear in . ver the last 5 years, T imaging has emerged as an important supplemental radiographic techniue for orthodontic diagnosis and treatment planning, especially in situations that reuire an understanding of the comple anatomic relationships and surrounding structures of the maillofacial skeleton. From the introduction of the cephalostat, roadbent stressed the need for a perfect matching of the lateral and posteroanterior -rays to obtain a perfect reproduction of the skull. T imaging provides uniue features and advantages to enhance orthodontic practice over conventional etraoral radiographic imaging. ateral cephalometrics provides information on the sagittal and vertical aspects of the malocclusion with little contribution about unilateral or transversal discrepancies. The latter seem to be related to
urbaniation and industrialiation becoming more freuent in the last decades.-5 Therefore, the need for a diagnostic tool providing information on the aspects of the dentoskeletal malocclusion is increasing. hile the clinical applications span from evaluation of anatomy to pathology of most structures in the maillofacial area, the key advantage of T is its high-resolution images at a relatively lower radiation dose. posing patients to -rays implies the eistence of a clinical ustication and that all the principles and procedures reuired to minimie patient eposure are considered. The concept should always be kept in mind is an acronym used in radiation safety for as low as reasonably achievable. This concept is supported by professional organiations as well as by government institutions. ecogniing that diagnostic imaging is the single greatest source of eposure to ioniing radiation for the population that is controllable, the ational ommission on adiation rotection and easurements has introduced a modication of the concept. represents as low as diagnostically acceptable. mplementation of this concept will reuire evidence-based udgments of the level of image uality reuired for specic diagnostic tasks as well as eposures and doses associated with this level of uality. ittle research is currently available in this area. For imaging modalities used in orthodontics, the radiation dose for panoramic imaging varies between and µv, while a cephalometric eam range is between and 5 µv. full mouth series ranges from to 5 µv based on the type of collimation used. hile and radiation doses are often compared for reference, they cannot truly be compared because the acuisition physics and the associated risks are completely different and cannot be euated. The actual risk for low-dose radiographic procedures such as maillofacial radiography, including T, is difcult to assess and is based on conservative assumptions as there are no data to establish the occurrence of cancer following eposure at these levels. owever, it is generally accepted that any increase in dose, no matter how small,
Principles and Biomechanics of Aligner Treatment
results in an incremental increase in risk. Therefore there is no safe limit or safety one for radiation eposure in orthodontic diagnostic imaging. recent meta-analysis about the effective dose of dental T stated that the mean adult effective doses grouped by eld of view F sie were µv large, µv medium, and µv small. ean child doses were 5 µv combined large and medium and µv small. arge differences were seen between different T units. The merican ental ssociation ouncil on cientic ffairs proposed a set of principles for consideration in the selection of T imaging for individual patient care. ccording to the guidelines, clinicians should perform radiographic imaging, including T, only after professional ustication that the potential clinical benets will outweigh the risks associated with eposure to ioniing radiation. owever, T may supplement or replace conventional dental -rays when the conventional images will not adeuately capture the needed information. ecently, a number of manufacturers have introduced T units capable of providing medium or even full F T acuisition using low-dose protocols. y adustments to rotation arc, m, kp, or the number of basis images or a combination thereof, T imaging can be performed at effective doses comparable with conventional panoramic eaminations range, – µv. This is accompanied by signicant reductions in image uality; however, viewer software can be helpful in improving the clinical eperience with low-uality images. ven at this level, child doses have been reported to be, on average, greater than adult doses. The use of low-dose protocols may be adeuate for low-level diagnostic tasks such as root angulations.
BENEFT OF CBCT FOR ORTHODONTC AEMENT The benets of T for orthodontic assessment include accuracy of image geometry. T offers the distinct advantage of geometry, which allows accurate measurements of obects and dimensions. The accuracy and reliability of measurements from T images have been
demonstrated, allowing precise assessment of unerupted tooth sies, bony dimensions in all three planes of space, and even soft tissue anthropometric measurements— things that are all important in orthodontic diagnosis and treatment planning.- The accurate localiation of ectopic, impacted, and supernumerary teeth is vital to the development of a patientspecic treatment plan with the best chance of success. T has been demonstrated to be superior for localiation and space estimation of unerupted maillary canines compared with conventional imaging methods.5 ne study indicated that the increased precision in the localiation of the canines and the improved estimation of the space conditions in the arch obtained with T resulted in a difference in diagnosis and treatment planning toward a more clinically orientated approach.5 T imaging was proven to be signicantly better than the panoramic radiograph in determining root resorption associated with canine impaction. ne study supported improved root resorption detection rates of with the use of T when compared with imaging. hen used for diagnosis, T has been shown to alter and improve the treatment recommendations for orthodontic patients with impacted or supernumerary teeth. ased on the ndings of a recent review and in accordance with the T entomaillofacial aediatric maging n nvestigation Towards ow ose adiation nduced isks proect, T can be considered also in children for diagnosis and treatment planning of impacted teeth and root resorption Fig. .5. aillary transverse deficiency may be one of the most pervasive skeletal problems in the craniofacial region. ts many manifestations are encountered daily by the orthodontist. lthough many analyses of the lateral cephalometric headlm have been developed for use in orthodontic and orthognathic treatment planning, the posteroanterior cephalogram has been largely ignored. The diagnosis of transverse discrepancy is uite challenging in the daily practice because of several methodologic limitations of the proposed methods.
Fig. 1.5 Cone-beam computed tomography data elaboration for enhancing diagnosis and treatment planning.
1 • iagnosis and Treatment Planning in the Three-imensional ra
Fig. 1. Case of impacted loer canine in hich the cone-beam computed tomography data are helpful in dening the right mechanics.
The maillary and mandibular skeletal widths at different tooth level, buccolingual inclination of each tooth, and root positions in the alveolar bone can be determined and evaluated from the T Fig. .. ith this information, the clinician can make a proper diagnosis and treatment plan for the patient. The temporomandibular oint T can be assessed for pathology more accurately with T images than with conventional radiographs. The T volume for orthodontic assessment will generally include the T and therefore is available for routine review. everal retrospective analyses of T volumes indicate 5 to of incidental ndings are related to T Fig. ., which is signicant enough for further follow-up or referral. T data can also be used to obtain the volumetric rendering of the upper airways. tudies of the upper airway based on T scans are considered to be reliable in dening the border between soft tissues and void spaces i.e., air, thus providing important information about the morphology i.e., cross-sectional area and volume of the pharyngeal airway5 Fig. .. owever, despite the potentials offered by the techniue in this eld and the potential role of orthodontists as sentinel physicians for sleep breathing disorders, limited, poor uality, and low evidence level literature is available on the effect of head posture and tongue position on upper airway dimensions and morphology in imaging. atural head position at T acuisition is the suggested standardied posture. owever, for repeatable measures of upper airway volumes it may clinically be difcult to obtain. ndications and methods related to tongue position and breathing during data acuisition are still lacking. Furthermore, a recent study focusing on the reliability of airway measurements stated that the oropharyngeal airway volume was the only parameter found to have generalied ecellent intra-eaminer and inter-eaminer reliability. n orthognathic surgery, igital maging and ommunications in edicine data from T can be used to fabricate physical stereolithographic models or to generate virtual models. The reconstructions are etremely useful in the diagnosing and treatment planning of facial
asymmetry cases. They can also be used to generate substitute grafts when warranted. T can be useful as a valuable planning tool from initial evaluation to the surgical procedure and then the correction of the dental component in the surgery-rst orthognathic approach. n addition, databases may be interfaced with the anatomic models to provide characteristics of the displayed tissues to reproduce tissue reactions to development, treatment, and function. The systematic summariation of the results presented in the literature suggests that computeraided planning is accurate for orthognathic surgery of the mailla and mandible, and with respect to the benets to the patient and surgical procedure it is estimated that computer-aided planning facilitates the analysis of surgical outcomes and provides greater accuracy Fig. .. recent systematic review was conducted to evaluate whether T imaging can be used to assess dentoalveolar relationships critical to determining risk assessment and help determine and improve periodontal treatment needs in patients undergoing orthodontic therapy. The conclusion was that pretreatment orthodontic T imaging can assist clinicians in selecting preventive or interceptive periodontal corticotomy and augmentation surgical reuirements, especially for treatment approaches involving buccal tooth movement at the anterior mandible or maillary premolars to prevent deleterious alveolar bone changes. This assumption seems more suitable for skeletally mature patients presenting with a thin periodontal phenotype prior to orthodontic treatment Fig. ..
3D FACA RECONTRUCTON TECHNUE The accurate acuisition of face appearance characteristics is important to plan orthognathic surgery, and ecellent work is based on an eact face modeling. precise approach to digital face prole acuiring, which is applied to simulate and design an optimal plan for face surgery by modern technologies such as , is reuired. Three types of face modeling methods are currently used to etract human face proles T technology,
Principles and Biomechanics of Aligner Treatment
Fig. 1. ccasional report of misunderstood right condyle nec fracture results in a -year-old child being prescribed cone-beam computed tomography for orthodontic reasons.
Fig. 1. Airay measurements from cone-beam computed tomography data.
1 • iagnosis and Treatment Planning in the Three-imensional ra
Fig. 1. ample of cone-beam computed tomography data integration in a surgery three-dimensional planning softare. (ohin Imain, Chaorh, CA, USA.
the passive optical sensing techniue, and the active optical sensing techniue. The reconstruction method based on T technology is sensitive to the skeleton and can be conveniently utilied for craniofacial plastics, as well as the oral and maillofacial correction of abnormalities. oft tissue data etraction, or segmentation, can be created using a dedicated software. For orthodontic purposes, the image should be recorded with eyes open and with the patient smiling. The smiling image will permit the use of dental landmarks to superimpose the digital models on the face reconstruction for treatment planning purposes. ovel technologies aiming at acuiring facial surface are available. tereophotogrammetry and laser scanning allow operators to uickly record facial anatomy and to perform a wider set of measurements5 not eposing patients to radiation Fig. .. tereophotogrammetry still represents the gold standard with respect to laser scanning at least for orthodontic applications since it is characteried by good precision and reproducibility, with random errors generally less than mm.5 ith this method, images are acuired by combining photographs captured from various angles with synchronous digital cameras, with the main advantage of reducing possible motion artifacts. The main limitation at this stage is represented by the high cost of the instrumentation. ccording to arver and acobson and arver and ckerman, it may be inappropriate to place everyone in the same esthetic framework and even more problematic to attempt this based solely on hard tissue relationships since the soft tissues often fail to respond predictably to hard tissue changes. ntegrating T data, facial reconstruction,
and digital models with specic simulation software will provide useful indications in relation to orthodontic treatment results and the eventual need of interdisciplinary intervention.
RTUA ETUP everal software programs are available on the market to create virtual setups able to produce the seuence of physical models on which thermoforming plastic foils are used to create aligners. etup accuracy is improved when virtual teeth segmentation is applied on digital models obtained by or digitiation of plaster casts, reducing the loss of tooth structure observed during the cutting process of the plaster in conventional plaster and wa setups. The segmentation process starts with marking mesial and distal points on each tooth or simply indicating the center of the crown on the occlusal view of the arches, depending on the software used. Then the software generally identies the gingival margin. Teeth segmentation and the tooth-tooth-gingiva segmentation are eecuted semiautomatically, but the operator can always correct the automatic process. nce teeth are segmented they are separated from the gingiva, and a mean virtual root shape and length are derived from proprietary databases is applied. ecently, virtual setup software programs are starting to use real root morphologies derived from patient T data when available. Tooth segmentation from T images in those cases is a fundamental step. ecent engineering innovations made the process simple and timesaving with respect to the past.
1
Principles and Biomechanics of Aligner Treatment
Fig. 1.1 Cone-beam computed tomography data used to plan an orthodontic epansion in a subect ith poor periodontal support (upper). rthodontic epansion, corticotomies, and bone grafts ere planned to obtain an ecellent nal result ithout bone dehiscence (lower)
A
B
Fig. 1.11 Stereophotogrammetry A and laser scan B three-dimensional reconstructions of the face of the same patient. (From Gibei , iarei , oa , e a. Threedimeniona faia anaom eaaion reiabii of aer anner oneie an roedre in omarion ih ereohoorammer. J Craniomaxillofac Surg. .
1 • iagnosis and Treatment Planning in the Three-imensional ra
11
Fig. 1.12 Superimposition of the virtual setup on the smile picture of a patient ith unilateral agenesis, visualiing from left to right the initial situation, the postorthodontic situation, and the nal smile ith restorative simulation.
nce the teeth have been segmented and the interproimal contacts dened, the arch form is adusted using software tools that can create an individual arch form. igital arch templates are also available, while several software programs consider the an acronym for ill ndrews and arry ndrews ridge. The occlusal plane as well as the original vertical plane are used as reference. ach tooth can be moved in the space since the reuired nal position has been achieved. t is important to mention that tooth movements on computers are unlimited. Tooth alignment and leveling can be planned on the computer screen, but this result may not be realistic for that specic patient. bviously, tooth movement has its biologic limitations. n the basis of the used system the virtual setup could be prepared by a trained dental technician or by a software epert; however, every setup should be based on biologic principles and on a biomechanics background making the orthodontist the initial designer and the nal reviewer of every setup. s progress in digital imaging techniues accelerates and tools to plan medical treatments improve, the use of virtual setups in orthodontics before and during treatment will become the mainstream in orthodontics Fig. ..
novel superimposition techniues, clinicians are able to simulate the outcome of both the osseous structures and the soft tissue posttreatment. The data integration makes the diagnostic process and the treatment planning more accurate and complete, provides an effective communication tool and a method for patients to visualie the simulated outcomes, instills motivation, and encourages compliance to achieve the desired treatment outcome Fig. .. hat technology is providing to orthodontists is amaing; however, what is still missing is the fourth dimension i.e., the dynamic movements of the mandible and the surrounding tissues integrated in the virtual model. dealistically, the capture of digital data for virtual modeling should happen in a one-step, single-device approach to improve accuracy. Future research will ll this gap and will realie the dream of the real virtual patient.
3D DATA NTEGRATON The creation of a virtual copy of each patient is dependent upon the integration of media les and the possibility of their fusion into a uniue and replicable model. T data can be used as a platform onto which other inputs can be fused with acceptable clinical accuracy. These data sources include light-based surface data such as photographic facial images and high-resolution surface models of the dentition produced by direct scans intraorally or indirectly by scanning impressions or study models. The integration of hard and soft tissues can provide a greater understanding of the interrelationship of the dentition and soft tissues to the underlying osseous frame. ndividual models of tooth are needed for the computer-aided orthodontic treatment planning and simulation. ith the
Fig. 1.13 The virtual patient in hich cone-beam computed tomography data, facial three-dimensional reconstruction, and virtual setup obtained after teeth segmentation are superimposed. Courtesy of dr. Alain Souchet, ulhouse, rance.
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Principles and Biomechanics of Aligner Treatment
References . merican ssociation of rthodontists. linical practice guidelines for orthodontics and dentofacial orthopedics. ; . https www.aaoinfo.orgdappsget-led5 . ribe F, handhoke T, anda . ndividualied orthodontic diagnosis. n anda , ed. Esthetics and iomechanics in Orthodontics. nd ed. t ouis, lsevier aunders; 5-. . arver , anoski . pecial considerations in diagnosis and treatment planning. n raber , anarsdall , ig , eds. Orthodontics urrent Principles and echniues. 5th ed. hiladelphia, osby; 5-. . angano , uongo F, igliario , et al. ombining intraoral scans, cone beam computed tomography and face scans the virtual patient. J raniofac Surg. ;-. 5. Tarraf , aredeliler . resent and the future of digital orthodontics. Semin Orthod. ;-5. . ossini , arrini , astroorio T, et al. iagnostic accuracy and measurement sensitivity of digital models for orthodontic purposes a systematic review. Am J Orthod Dentofacial Orthop. ;-. . laus , adeke , int , et al. eneration of digital models of the dental arches using optical scanning techniues. Semin Orthod. ;-. . ühnisch , öchtig F, itchika , et al. n vivo validation of nearinfrared light transillumination for interproimal dentin caries detection. lin Oral nvestig. ;-. . ayar , ahadevan . paradigm shift in the concept for making dental impressions. J Pharm ioallied Sci. 5;-5. . aeer , illett T, youb F, et al. pplications of imaging in orthodontics part . J Orthod. ;-. . roadbent . new -ray techniue and its application to orthodontia. Angle Orthod. ;5-. . carfe , evedo , Toghyani , et al. one beam computed tomographic imaging in orthodontics. Aust Dent J. ;-5. . orruccini , Flander , aul . outh breathing, occlusion, and moderniation in a north ndian population. n epidemiologic study. Angle Orthod. 5;55-. . amporesi , arinelli , aroni , et al. ental arch dimensions and tooth wear in two samples of children in the 5s and s. r Dent J. ;e. 5. indsten , gaard , arsson . Transversal dental arch dimensions in -year-old children born in the s and the s. Am J Orthod Dentofacial Orthop. ;5-5. . Tadinada , chneider , adav . ole of cone beam computed tomography in contemporary orthodontics. Sem Orthod. ; -5. . merican ental ssociation ouncil on cientic ffairs. The use of cone-beam tomography in dentistry. n advisory statement from the merican ental ssociation ouncil on cientic ffairs. J Am Dent Assoc. ;-. . orner . TT guideline development panel. n one eam for Dental and Maillofacial Radiolog Evidence ased uidelines Radiation Protection Series. uembourg uropean ommission irectorate-eneral for nergy; 5. . udlow , Timothy , alker , et al. ffective dose of dental T—a meta-analysis of published data and additional data for nine T units. Dentomaillofac Radiol. 5;. . alentin . The recommendations of the nternational ommission on adiological rotection. ublication . Ann RP. ;-. . udlow , alker . ssessment of phantom dosimetry and image uality of i-T F cone-beam computed tomography. Am J Orthod Dentofacial Orthop. ;-. . erco , igali r , iner , et al. ccuracy and reliability of linear cephalometric measurements from cone-beam computed tomography scans of a dry human skull. Am J Orthod Dentofacial Orthop. ;,e-e. . Fourie , amstra , errits , et al. ccuracy and repeatability of anthropometric facial measurements using cone beam computed tomography. left Palate raniofac J. ;-. . agravère , arey , Toogood , et al. Three-dimensional accuracy of measurements made with software on cone-beam computed tomography images. Am J Orthod Dentofacial Orthop. ;-. 5. otticelli , erna , attaneo , et al. Two-versus three-dimensional imaging in subects with unerupted maillary canines. Eur J Orthod. ;-.
. odges , tchison , hite . mpact of cone-beam computed tomography on orthodontic diagnosis and treatment planning. Am J Orthod Dentofacial Orthop. ;5-. . go TT, Fishman , ossouw , et al. orrelation between panoramic radiography and cone-beam computed tomography in assessing maillary impacted canines. Angle Orthod. ;-. . awad , armichael F, oughton , et al. review of cone beam computed tomography for the diagnosis of root resorption associated with impacted canines, introducing an innovative root resorption scale. Oral Surg Oral Med Oral Pathol Oral Radiol. ;5-. . aney , ansky , ee , et al. omparative analysis of traditional radiographs and cone-beam computed tomography volumetric images in the diagnosis and treatment planning of maillary impacted canines. Am J Orthod Dentofacial Orthop. ;5-5. . e rauwe , ya , huaat , et al. T in orthodontics a systematic review on ustication of T in a paediatric population prior to orthodontic treatment. Eur J Orthod. ;-. doi.eocy. . enning , acobs , auwels , et al. one-beam T in paediatric dentistry T proect position statement. Pediatr Radiol. ;-. . camara . aillary transverse deciency. Am J Orthod Dentofacial Orthop. ;5-5. . iner , l abandi , igali , et al. one-beam computed tomography transverse analysis. art normative data. Am J Orthod Dentofacial Orthop. ;-. . arson . one-beam computed tomography is the imaging techniue of choice for comprehensive orthodontic assessment. Northwest Dent. ;-. 5. hokri , iresmaeili , hmadi , et al. omparison of pharyngeal airway volume in different skeletal facial patterns using cone beam computed tomography. J lin Ep Dent. ;ee. . urani F, i arlo , attaneo , et al. ffect of head and tongue posture on the pharyngeal airway dimensions and morphology in three-dimensional imaging a systematic review. J Oral Maillofac Res. ;e. . immerman , ora , liska T. eliability of upper airway assessment using T. Eur J Orthod. ;-. . aas r , ecker , de liveira . omputer-aided planning in orthognathic surgery-systematic review. nt J Oral Maillofac Surg. ;-5-5. . andelaris , eiva , hambrone . one-beam computed tomography and interdisciplinary dentofacial therapy an merican cademy of eriodontology best evidence review focusing on risk assessment of the dentoalveolar bone changes inuenced by tooth movement. J Periodontol. ;-. . chmeleisen , chramm . omputer-assisted reconstruction of the facial skeleton. Arch acial Plast Surg. ;5. . ell . omputer planning and intraoperative navigation in craniomaillofacial surgery. Oral Maillofac Surg lin North Am. ;5-5. . irshmüller , nnocent , aribaldi . eal-time correlation-based stereo vision with reduced border errors. nt J omput is. ;-. . ou , hen , hang , et al. eal-time and high-resolution face measurement via a smart active optical sensor. Sensors asel. ;e. . Troulis , verett , eldin , et al. evelopment of a three-dimensional treatment planning system based on computed tomographic data. nt J Oral Maillofac Surg. ;-5. 5. ibelli , ucciarelli , oppa , et al. Three-dimensional facial anatomy evaluation reliability of laser scanner consecutive scans procedure in comparison with stereophotogrammetry. J raniomaillofac Surg. ;-. . arver , acobson . The aesthetic dentofacial analysis. lin Plast Surg. ;-. . arver , ckerman . ynamic smile visualiation and uantication part . mile analysis and treatment strategies. Am J Orthod Dentofacial Orthop. ;-. . ia , an , hang , et al. ndividual tooth segmentation from T images scanned with contacts of maillary and mandible teeth. omput Methods Programs iomed. ;-. . amardella T, othier , ilella , et al. irtual setup application in orthodontic practice. J Orofac Orthop. ;-.
2
Current Biomechanical Rationale Concerning Composite Attachments in Aligner Orthodontics JUAN PABLO GOMEZ ARANGO
Introduction he orthodontic techniue that we now call “aligner orthodontics” has evolved considerably over the last years. mprovements in behavior of aligner plastics, treatment planning software, and three-dimensional 3 printing have served one basic but fundamental intention to mitigate the biomechanical limitations inherent to aligner-based tooth movement. nother signicant development designed to overcome the aforementioned biomechanical shortcomings of aligner systems has been the continuous improvement of biomechanically complementary composite attachments. ttachments were conceived to produce supplementary force vectors that, when applied to teeth by the aligner material, transform the resultant system, allowing complex tooth movements. he application of one of the initial geometric congurations was initially presented by the clinical team from lign echnology nc., as basic x 3 mm rectangular structures, bonded to the lower incisor buccal surface, in an attempt at controlling undesired tipping during space closure after incisor extraction ig. .. s the incisors adacent to the extraction space begin to incline mesially, the rigid, xed structure of the attachment collides with aligner plastic, producing force couples that counteract the initial moment, reducing undesired tipping see ig. .. rthodontic tooth movement with conventional bracket techniues can deliver sophisticated force systems due to the manner in which the rigid ligature-archwire-bracket scheme “grasps” the malaligned tooth. his particular arrangement allows broad control of magnitude and direction of applied force vectors, and, conseuentially, of tooth movement ig. .. t is important to keep in mind that attachments work, not as active agents that produce forces, but by passively “getting in the way” of plastic as it elastically deforms due to lack of coincidence between tooth position and aligner material “mismatch”, establishing the force vector that subseuently affects the tooth ig. .3. iomaterials used for attachment fabrication must assure that reuirements in adhesion, wear resistance, and esthetics are fullled. recent study suggests that contemporary microlled resin composites provide sufcient
wear resistance to deliver a stable attachment shape during treatment, assuring its functionality. Mantovani et al.3 also concluded that the use of bulk-lled resins for attachment fabrication improved dimensional stability when compared to low-viscosity resins, which experience higher polymerization shrinkage. he use of translucent composites generally provides sufcient esthetic acceptance and stain resistance as long as an adeuate bonding techniue is executed, in which voids bubbles in attachment surface and excessive residue ash left on tooth surface are avoided. everal considerations come into play when determining the optimal attachment design for a specic clinical obective geometry, location, and size.
Geometry (Active Surface Orientation) t the time of aligner insertion, orthodontic forces will be produced in response to the particular complex pattern of mismatches between plastic and tooth structure. his pattern of mismatch–plastic deformation–orthodontic force is critical for attachment design during digital simulation to produce specic areas active surfaces that will contact aligner plastic with predetermined force magnitudes, producing the desired force vectors and conseuent tooth movements. ot all the surface area of attachments will be in direct contact with the aligner. he active or functional surfaces can and should be determined with thoughtful biomechanical intentionality, in accordance with clinical obectives ig. .. hile the magnitude of the force produced is determined by the amount of mismatch along with the characteristics of aligner material, the direction of the force will depend on the orientation of the active surface. he principles of mechanics state that the direction of the normal component of the contact force the vector that in this case acts upon the active surface of the attachment will always be perpendicular to that surface see ig. .. dentifying the direction of these complementary force vectors is essential for treatment planning, especially when more than one force acts simultaneously. n these cases, the resultant forces must be properly recognized to deliver predictable tooth movements see ig. .. 13
14
Principles and Biomechanics of Aligner Treatment
A
A
B
C B Fig. 2.1 (A) Mesial tipping moments (red curved arrows) produced by aligner forces (red arrows) occurring during space closure. Antitipping moments (blue curved arrows) produced by forces (blue arrows) acting at rectangular vertical attachments (B). Opposing moments are canceled out, promoting bodily movement.
Fig. 2.3 (A) Alignertooth mismatch. (B) lastic aligner deformation and activation of forces upon aligner insertion. () Tooth alignment after aligner seuence.
Location
Fig. 2.2 The typical force couple generated during bracetbased alignment of rotated tooth ith a fully engaged . iTi archire consists of to force vectors one that pushes against the posterior all of the slot (red arrow) and a second that pulls aay from the same all (blue arrow)
ased on the premise that the magnitude of a moment is proportional to the perpendicular distance between the line of action and the center of resistance, to fully understand the effect of aligner-based orthodontic forces being applied in any particular moment, it is essential to establish this distance in the three planes of space. nce this correlation has been clearly established and uantied, there will be a much clearer picture of the effectiveness of expected rotational moments as well as the possibility of anticipating undesired occurrences such as buccolingual and mesiodistal tipping and intrusion. n a case in which mesiolingual rotation of the tooth is reuired, localization of attachment will produce a strong mesial tipping moment and a weak mesiolingual rotational moment ig. .. n this specic clinical situation, a better alternative would be with attachment location , in which modication in distance from line of action to center of resistance would reduce tipping
2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics
A
15
C
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Fig. 2.4 (A) Active surfaces of attachments. (B) irection of forces acting at active surfaces. () esultant force affecting the rst premolar ill produce etrusion and clocise, secondorder rotation.
A
Distal
Mesial
B
Distal
Mesial
Fig. 2.5 (A) ue to the distance beteen the center of resistance (blue dot) and the line of action (red dotted line), large mesial tipping and negligible mesiolingual rotational moments should be epected. (B) A more mesial and apical attachment location ill result in reduced mesial tipping and increased mesiolingual rotational moments, increasing clinical efcacy.
tendency as well as increase mesiolingual rotational capacity see ig. .. nother example of the inuence of attachment localization is observed during transverse arch expansion, when buccal tipping of posterior segments is detrimental to treatment obectives. recent unpublished nite element analysis study of the mechanical effects of the bonding position of rectangular horizontal attachments found that the resultant tipping moment acting on the molars was greater when located on the lingual surface of the rst upper molars versus the labial surface ig. ..
Size ttachment size is important because of its mechanical and esthetic implications. mall congurations are desirable because they are less noticeable however, as size diminishes, so does the ability to produce predictable forces due to reduced active surface area. n the other hand, larger attachment designs are desirable because of their increased biomechanical capabilities, but they result in increased aligner retention with subseuent patient discomfort and negative esthetic perception, especially with highprole congurations in anterior teeth.
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Principles and Biomechanics of Aligner Treatment
B
A
Fig. 2.6 uring epansion, labial attachment location (A) produced smaller net buccal molar tipping moments than lingually bonded attachments (B).
Functions PROVIDING ALIGNER RETENTION or aligner-based orthodontic forces to affect teeth as conceived in digital simulation, the aligner must be stably seated after insertion and remain so for the duration of treatment. ccasionally, decient adaptation of the aligner may occur, usually resulting from faulty fabrication, but may also occur due to the many reactive forces produced once properly tted. or example, as a freuent response to intrusive forces acting on the posterior teeth, the aligner will tend to be dislodged in the anterior segment, and vice versa. he use of intermaxillary elastics, especially when they are engaged directly to the aligner, will also tend to vertically dislodge it in the direction of the elastic force. onding retentive attachments on teeth adacent to those receptors of the elastic force is recommended to maintain proper aligner engagement ig. .. study by ones et al. suggests that the optimal attachment conguration, when high aligner retention is imperative, is a
A
nongingivally beveled such as a horizontal rectangular or occlusally beveled design, as close to the gingival margin as possible see ig. .. s a general rule of attachment design, occlusal beveling will facilitate aligner insertion due to the inclined plane conguration as well as increase force and discomfort reuired for aligner removal.
AVOIDING ALIGNER “SLIPPING” specially when rotating rounded teeth, the sum of a series of tangential forces is responsible for tooth movement ig. ., causing inconvenient displacement slipping of the aligner in relation to the tooth surface, reducing the system’s efcacy and predictability, and resulting in lack of full expression of digitally planned rotation with the tooth lagging behind the corresponding aligner stage. linically, incomplete rotation and loss of tracking will be observed, manifesting as a space between tooth and plastic see ig. .. ppropriately designed attachments can help the aligner lock in to the tooth crown, greatly reducing this undesired slipping effect.
B Fig. 2.7 (A) Attachments located on teeth adacent to force application increase aligner retention hen using inter maillary elastics. (B) Attachment position close to the gingival margin and occlusally beveled geometry is ideal for aligner retention.
2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics
A
B
Fig. 2.8 (A) Multiple tangential forces (red arrows) acting during alignerbased, bicuspid rotation. (B) ue to slipping effect, incomplete epression of epected rotation ith space beteen tooth and aligner (in yellow) ill be observed.
DELIVERING PREDETERMINED FORCE VECTORS he fundamental purpose of composite attachments in aligner orthodontics is to produce specic, complementary force vectors reuired for predictable tooth movement, which are not possible with the sole use of aligners thermoformed with existing materials ig. ..
17
nfortunately, to harness the full clinical potential of bonded attachments, current polymers have yet to resolve limitations associated with their viscoelastic and hygroscopic nature. nce inserted, the initial force produced by the aligner after it is elastically deformed is not constant and will decline with time. his time-dependent reduction of force under constant deformation is called stress relaxation. ot infreuently, due to unwarranted localized stress caused by excessive mismatch, lack of compliance, or shortcomings inherent to the polymer, the aligner is not able to accommodate the attachment. hen forces exerted upon the aligner exceed its capability to adust to the new position, unintended forces will appear, the tooth will lag behind, and control will be lost see ig. .. ig. . illustrates how this phenomenon is responsible for the incomplete expression of the expected tooth movement, where only 3 of the degrees of predicted rotation were achieved after completion of the entire seuence of stages. n this case, after the aligner is removed, plastic deformation of the aligner material is evident. his time-dependent plastic deformation under constant force is called creep and is attributed to reorganization of polymer chains. t is important to underline that this permanent deformation, so detrimental to clinical performance of plastic aligners, is not caused by a violation of the materials’ elastic limit but is due to a time-dependent, mechanochemical phenomenon of a different nature. his inherent aw of aligner plastics is the maor cause behind the inconsistent force levels and plastic deformation that result in one of the most dreaded occurrences for orthodontists practicing aligner orthodontics, now commonly referred to as loss of tracking. ig. . illustrates an example of the clinical manifestations of this complex reality in which mesiolingual rotation and extrusion of a rst upper left bicuspid were incorporated in the digital treatment plan but did not fully occur. he lack of coincidence between the attachment and its corresponding recess in the aligner is unambiguous evidence of loss of tracking, a contingency that in many cases must be resolved by obtaining updated digital dental models from which a new treatment seuence must be designed.
Basic Attachment Conurations in Current Ainer Orthodontics he evolution of attachments, derived from a better understanding of the effect of geometry, location, and size of the composite structure, has resulted in a diverse array of congurations with well-dened biomechanical obectives.
VERTICAL CONTROL
A
B
Fig. 2.9 (A) Properly designed attachments produce complementary force vectors reuired for predictable tooth movement. (B) Polymer stress relaation and creep, along ith incomplete rotation and unin tended force (blue arrow), may occur during seuence of aligner based, tooth rotation stages.
he tendency of conventional xed orthodontics to increase vertical dimension, especially in open-bite patients with increased anterior facial height, has been studied. ligner-based treatment has proven to be an effective alternative for open-bite correction-3 with encouraging results.3 uccessful treatment often includes the sum of complementary clinical strategies such as the combined effect of counterclockwise mandibular rotation, posterior intrusion, and anterior extrusion.
18
Principles and Biomechanics of Aligner Treatment
A
B Fig. 2.1 (A) mage from linhec treatment plan. (B) oss of tracing ith incomplete epression of rotation and etrusion of left upper bicuspid. ac of coincidence beteen attachment (green shaded area) and its corresponding recess in the aligner (green outline) is observed.
ANTERIOR ETRSION orrection of open bite based solely on anterior extrusion is to be viewed with caution because of possible negative effects such as root resorption, periodontal deterioration, instability, and unfavorable esthetics. long with these clinical restrictions, aligner extrusion poses mechanical limitations in anterior teeth in which buccal and lingual crown surfaces converge towards the incisal edge ig. ., facilitating aligner dislodgement and rendering this type of tooth movement virtually impossible see ig. . without the use of supplementary composite attachments. gingivally oriented, inclined plane conguration ig. . provides a force system that improves predictability of this type of movement. he importance of attachment design can be illustrated with a graphic simplication of a complex interaction of vectors. he resultant force acting on the
A
A
B B
Fig. 2.11 (A) onverging buccal and lingual cron surfaces. (B) nde sired aligner dislodgment during etrusive movement.
Fig. 2.12 (A) Optimied trusion Attachments (Align Technology, anta lara, A) on central incisors. (B) ingivallyoriented inclined plane ith optimal active surface angulation.
2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics
19
150° 110°
A
B
Fig. 2.13 (A) orces transmitted by the aligner (red arrows) and resultant forces (purple arrows) acting on the tooth. (B) A reduction of the angle beteen active attachment surface and buccal tooth surface produces stronger resul tant etrusive forces.
incisor is derived from the two red arrows that represent buccal and lingual forces present during aligner-based extrusion ig. .3. educing the angle formed by the active surface of the attachment and the buccal surface of the tooth will result in a stronger resultant force see ig. .3. linicians must be wary of excessive reduction of this angle, which along with excessive force may produce difculty of aligner-attachment engagement with the ensuing localized plastic deformation.
POSTERIOR INTRSION ecent studies suggest that the presence of interocclusal plastic during aligner treatment may produce a bite-block effect that potentiates bite closure and posterior intrusion capabilities. his improves treatment outlook, especially in cases in which anterior extrusion is not desirable and intrusion of posterior teeth, with the conseuent mandibular rotation, are to be considered as part of the strategy for bite closure. s mentioned previously, intrusive forces acting in the posterior region will tend to dislodge the aligner in the occlusal direction. ven with light posterior intrusive forces, an opposite, reactive force should be expected in the anterior arch that will tend to vertically dislodge the aligner ig. .. ingivally positioned rectangular horizontal or occlusally attachments beveled towards the incisal edge should provide the necessary aligner stability for optimal treatment progress.
FIRSTORDER CONTROL Ri otation of teeth with rounded anatomies such as bicuspids and molars is another movement particularly difcult to accomplish with plastic aligners without the help
Fig. 2.14 ntrusion in the posterior segment (red arrows) produces reactive forces that ill tend to dislodge the aligner anteriorly (blue arrows). Adeuate attachment selection on anterior teeth ill counter act this undesired occurrence.
of specialized attachments, which improve biomechanical capabilities. he limitations associated with rounded crown morphologies are due to some extent to three particular realities n
s mentioned previously, in rounded crown congurations, the tangential nature of the forces produced during aligner-based tooth rotation, along with very
2
n
n
Principles and Biomechanics of Aligner Treatment
low coefcient of friction between the two surfaces, facilitates a slipping effect between the aligner and tooth. he line of action of the normal force vectors resultant from tangential forces delivered during rotation of rounded crowns crosses at a short distance from the center of resistance, resulting in weaker rotational moments ig. .. hese difculties are overcome by means of specically designed composite attachments, with properly oriented active surfaces, reconguring resultant force vectors with increased intervector distance see ig. . and resulting in stronger, more effective rotational moments. dditionally, the attachment structure blocks the slipping effect between aligner and tooth surface, allowing a fuller expression of desired tooth movement. nother effect observed in laboratory experimentation as well as in clinical practice is unintended intrusion
during rotational tooth movement. n another study using nite element analysis, researchers demonstrated that during aligner-based rotation of an upper canine without attachment, not only did the tooth lag behind the corresponding aligner stage almost by 3, but it also displayed clinically signicant intrusive forces that were found to be 3. times greater without than with attachments ig. .. he same numeric model, from an incisal perspective, revealed distinct pressure areas on the mesial and distal slopes of the incisal ridge ig. ., to which this undesirable effect can be attributed and corresponds to the normal components of the forces imparted by the aligner. ue to the orientation of With ATT Without ATT 30
Canine rotational lag (%)
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B Fig. 2.15 (A) otational forces produced by the aligner (purple arrows) are transmitted to the tooth as normal force components (red arrows), hich are perpendicular to tooth surface tangents (purple dotted lines). (B) ncorporation of bonded attachment increases the magnitude and efcacy of rotational moment by increasing the perpendicular distance (green dotted line) beteen the line of action (red dotted line) and the center of resistance (es)
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3.5
Rotation (°)
Fig. 2.16 (A) ithout attachment, the tooth lagged behind the aligner almost by . ith attachment incorporation, this lag dropped to . (B) ntrusive forces observed at the periodontal ligament ithout attachments as . for every degree of rotation, hile ith attachments the load as reduced to . for every degree. ATT, Attachment. (Adapted from óme P, Peña M, alencia , et al. ffect of composite attachment on initial force system generated during canine rotation ith plastic aligners a three dimensional nite elements analysis. J Align Orthod. .)
4
2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics
21
Buccal Distal
Mesial
Mesial Distal
A
Lingual Fig. 2.18 Optimied otation Attachment (Align Technology, anta lara, A) ith active surface oriented to provide a compensatory etrusive force.
B Fig. 2.17 (A) igital image of occlusal vie of right upper canine. Occlusal vie of nite element method simulation of upper right ca nine during mesiolingual rotation. (B) istinctly intrusive pressure ar eas (red) on mesiolabial and distolingual aspects of the tooth cron appear upon aligner insertion. The dotted line represents the aligner’s prole. (Adapted from óme P, Peña M, alencia , et al. ffect of composite attachment on initial force system generated during canine rotation ith plastic aligners a three dimensional nite elements analysis. J Align Orthod. .)
A
the surface area, these forces are clearly intrusive. his undesirable intrusive effect can be reduced with appropriate attachment design, orienting the active surface at an angle in which the normal component of the force transmitted by the aligner will express an extrusive tendency ig. ..
SECONDORDER CONTROL ipping movements are easily achieved with bracket-based biomechanics ig. .. n the other hand, aligners lack control of mesiodistal root position due to the system’s inability to produce the reuired force couples, explaining why modication of anterior teeth angulation is so challenging. o improve second-order capabilities, aligner-based systems rely on specialized attachments that generate euivalent force couples see ig. ..
B Fig. 2.19 (A) orce couple produced during bracetbased correction of ecessive mesial tip. (B) uivalent force couple produced at Opti mied oot ontrol Attachments (Align Technology, anta lara, A) during alignerbased tipping.
22
Principles and Biomechanics of Aligner Treatment
Ai T uccessful closure of extraction spaces with aligners is also particularly difcult without excessive tipping in the direction of tooth movement. umeric models describing tooth displacement ig. . and periodontal ligament strain ig. . patterns during distal tooth movement have shown that ptimized oot ontrol ttachments lign echnology, anta lara, , when bonded to upper cuspids, produce force systems capable of controlling undesired inclination during extraction space closure. Pi T n the posterior segment, tipping movements are not easily obtained with aligner-based mechanics without combining xed auxiliaries such as buccal tubes, power arms, etc., and these tooth movements, although possible, reuire sophisticated treatment planning, clinical expertise, and patient cooperation. dditionally, as with most complex force systems, specialized attachments must be designed to enhance the biomechanical capabilities of the aligner. he goal of this conguration of composite attachments is to produce a force couple and its corresponding moment that will incline the tooth in the desired direction ig. .. lternatively, the rectangular, horizontal attachment can be replaced with two shorter attachments, with variable distance separating them according to the clinician’s plan see ig. .. t is important to remember that the magnitude of the moment will depend on the amount of activation and corresponding mismatch prescribed in the digital treatment plan. n the other hand, the magnitude of the individual force vectors acting at the
A
B
Fig. 2.21 Periodontal ligament strain patterns during alignerbased distaliation of upper right canine. (A) ithout attachments, distocervi cal pressure (in blue) and distoapical tension (in red) areas ere observed, typical of uncontrolled distal tipping. (B) ith attachments, uniform pressure along the distal root surface (in blue) and uniform tension (in red) along the medial surface, typical of distal bodily move ment, ere observed. (Adapted from ome P, Peña M, Martíne , et al. nitial force systems during bodily tooth movement ith plastic aligners and composite attachments a threedimensional nite element analysis. Angle Orthod. .)
A
A
B
Fig. 2.2 Tooth displacement patterns during alignerbased distalia tion of upper right canine. (A) ithout attachments, distinct uncon trolled distal tipping as observed, ith center of rotation beteen apical and middle thirds of the root (red arrow). (B) ith attachments, the canine epressed distal bodily movement. (Adapted from ome P, Peña M, Mart√≠ne , et al. nitial force systems during bodily tooth movement ith plastic aligners and composite attachments a three dimensional nite element analysis. Angle Orthod. .)
B Fig. 2.22 (A) prighting moment produced at single rectangular hori ontal attachment. (B) Alternative tin attachment conguration.
2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics
23
B
A
Fig. 2.23 Producing euivalent moments (curved arrows), an increase in intervector distance proportionately reduces force magnitude (blue arrows) acting at attachment surface. To degrees of distal tipping ith a mm rectangular attachment (A) ill produce higher forces on the aligner than ith a toattachment conguration that signicantly separates the force vectors (B) of the acting couple.
aligner-attachment contact will depend on the distance between these two vectors. s the distance between the vectors decreases, the forces produced at the active surfaces of the attachments to produce an eual uprighting moment will increase ig. .3. his is an extremely important detail, considering aligner polymers’ high susceptibility to creep-related plastic deformation, which reuires the use of the lowest forces possible.
Dii M n effective strategy for controlling anchorage during extraction space closure is anterior and posterior moment to
A
force ratio manipulation in favor of the segment that reuires anchorage.3 s shown in ig. ., a reciprocal moment to force ratio between anterior alpha and posterior beta segments will result in group space closure, in which both segments will meet at the middle of the extraction space resulting in class malocclusion see ig. .. o obtain class occlusion, posterior anchorage must be reinforced. onding rectangular horizontal attachments on the buccal surface of posterior teeth ig. . will result in clockwise moments that will resist mesialization of posterior teeth, resulting in group space closure and the desired class occlusal outcome see ig. ..
B Fig. 2.24 lass case in hich reciprocal moments beteen anterior and posterior segments during etraction space closure (A) ill result in anchorage loss and class occlusion (B).
24
Principles and Biomechanics of Aligner Treatment
A
B Fig. 2.25 locise moments (blue curved arrows) produced by attachments bonded to posterior teeth (A) ill counteract posterior anchorage loss, reducing it to , resulting in class occlusion (B).
TIRDORDER CONTROL Ai T orue modication of anterior teeth with conventional brackets is easily achieved by means of preactivation of the rectangular archwire, producing a complex, highforce couple when fully engaged in the rectangular slot ig. .. ccomplishing the same type of movement with plastic aligners demands an euivalent couple, derived from horizontal, parallel, and opposing forces applied on buccal and lingual surfaces see ig. .. ecause of the relatively ample distance between the couple vectors, force
A
magnitudes reuired for third-order control are signicantly lower than those reuired in euivalent bracketbased force systems.
Pi T orrection of transverse deciencies by expansion of the dental arch continues to be a challenging clinical obective with current aligner-based techniues. his has led to a widespread tendency of clinicians to overcorrect expansive movements in 3 treatment planning. he main reasons for lack of efcacy and predictability in the transverse plane are excess buccal tipping and insufcient force levels.
B
Fig. 2.26 (A) By preactivating (red shaded) and subseuently inserting (red) the archire, a force couple (blue arrows) and its corresponding counterclocise moment (blue curved arrow) ill be produced. (B) The same positive torue can be achieved ith aligners by producing an euivalent couple, ith loer forces and increased intervec tor distance.
2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics
Excess Buccal Tipping ecause forces act at a distance from the molar’s center of resistance ig. ., buccal tipping must always be expected when expansive forces are applied, especially when aligner-based forces are used. ith negligible friction and conseuent pervasive sliding effect between plastic and tooth crown, and relatively low stiffness as uncontrolled tipping occurs during expansion, the aligner will tend to are, losing control as dissociation between tooth and plastic occurs see ig. .. he use of attachments horizontal rectangular or occlusally beveled bonded to the buccal surface of posterior teeth helps improve third-order control by counteracting the undesired tipping moment as a result of a couple with opposite forces acting at the occlusal surface and at the gingival aspect of the attachment ig. ..
Lingual
Insufcient Force Levels ue to their horseshoe-shaped geometry, orthodontic aligners deliver expansive forces in a particular manner in which an anteroposterior decreasing force gradient will be observed ig. .. ecause of this distinct mode of force transmission, researchers have found that efcacy planned vs. nal increase in arch width of upper arch expansion dropped from at rst premolars to at the second molar. ncreasing force levels during arch expansion by using thicker or lower elastic modulus polymers for aligner fabrication would improve this shortcoming, but not without the inconvenient increase in force levels of all other tooth movements programmed during the expansive stages. n alternative solution is the use of intermaxillary elastics, especially in cases with reduced anterior facial height, in which buccolingual tipping and
Buccal Lingual
Buccal
B
A
Fig. 2.27 (A) Alignerbased epansive force (red arrow) applied at a distance from the center of resistance (CRes) ill produce counterclocise moment (red curved arrow). (B) ithout preventive measures, buccal tipping ith center of rotation (CRot) above the furcation ill occur, folloed by aligner deformation and loss of control.
Lingual
A
Buccal
25
Lingual
Buccal
B
Fig. 2.28 (A) Opposing forces (blue arrows) acting at the occlusal surface and gingival aspect of a rectangular hori ontal buccal attachment ill provide a clocise moment (blue curved arrow) that reduces buccal tipping, ith apical migration of the center of rotation (CRot) (B).
26
Principles and Biomechanics of Aligner Treatment
A
B Fig. 2.29 (A) Programmed epansive mismatch beteen aligner and dental arch. (B) Once inserted, the resultant epansive forces ill have a distally decreasing magnitude gradient.
A
B
C
D Fig. 2.3 o angle patient (A), ith bilateral posterior crossbite (B, ) and midline discrepancy ().
extrusion of posterior segments are acceptable ig. .3. lastic forces originated from buttons bonded to palatal upper and buccal lower aspects of molars ig. .3 will produce a force vector with vertical and horizontal components of clinically relevant magnitudes that must be considered during treatment planning. n the example in ig. .3, a -gmf vector produced by a crossed intermaxillary elastic will be transmitted to the system as
gmf of horizontal and gmf of vertical force. s mentioned previously, horizontal rectangular attachments are effective in mitigating undesired tipping by counteracting excessive rotational moments ig. .33. y controlling vertical and transverse force levels, as well as desired and undesired tipping moments, predictable aligner-based treatment of different types of transverse discrepancies is possible ig. .3.
2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics
A
C
B
Fig. 2.31 (A) nitial linhec stage. (B) Aligners inserted, prior to bonding of upper palatal and loer buccal buttons. () rossbite elastic.
90 gmf 42 gmf 100 gmf
Fig. 2.32 A gmf intermaillary elastic force ill produce a gmf effective transverse force, epanding the upper arch and compressing the loer arch. Additionally, gmf of etrusive force ill eually in§u ence upper and loer arches.
Fig. 2.33 n the upper arch, the moments provided by upper buccal attachments (blue curved arrows) ill counteract moments (red curved arrows) produced by elastic epansive forces (red arrows), reducing undesired upper tipping. n the loer arch, unopposed lingual elastic forces (dotted red arrows) ill result in epected lingual tipping (dotted red curved arrows)
27
28
Principles and Biomechanics of Aligner Treatment
A
B
D
C Fig. 2.34 (A, B) nitial bilateral crossbite and midline discrepancy. (, ) Alignerbased correction ith complemen tary use of intermaillary elastics.
References . Miller , uong , erakhshan M. ower incisor extraction treatment with the nvisalign system. J Clin Orthod. 3-. . arreda , zierewianko , Muñoz , et al. urface wear of resin composites used for nvisalign® attachments. Acta Odontol Latinoam. 3-. 3. Mantovani , astroorio , ossini , et al. canning electron microscopy analysis of aligner tting on anchorage attachments. J Orofac Orthop. Mar-. . einberg , ouccar M, au , et al. ranslucency, stain resistance, and hardness of composites used for nvisalign attachments. J Clin Orthod. 3-. . ristizabal , arcía , eña M. aloracion del efecto biomecánico en el ligamento periodontal durante la expansión en el arco maxilar, de canino a molar, usando alineadores termo-formados con aditamentos biomecánicos complementarios, mediante métodos computacionales Mc thesis. ali, olombia niversidad del alle . ones M, Mah , ’oole . etention of thermoformed aligners with attachments of various shapes and positions. J Clin Orthod. 33-. . ombardo , Martines , Mazzanti , et al. tress relaxation properties of four orthodontic aligner materials a -hour in vitro study. Angle Orthod. -. . ang , hang , hen , et al. ynamic stress relaxation of orthodontic thermoplastic materials in a simulated oral environment. ent Mat . 33-. . lexandropoulos , l abbari , inelis , et al. hemical and mechanical characteristics of contemporary thermoplastic orthodontic materials. Aust Orthod J. 3-. . Moshiri , ra√∫o , Mcray , et al. ephalometric evaluation of adult anterior open bite non-extraction treatment with nvisalign. Dental Press J Orthod. 3-3.
. uarneri M, liverio , ilvestre , et al. pen bite treatment using clear aligners. Angle Orthod. 333-. . iancotti , arino , Mampieri . se of clear aligners in open bite cases an unexpected treatment option. J Orthod. –. 3. au , einberg , hristou . ffectiveness of clear aligners in treating patients with anterior open bite a retrospective analysis. J Clin Orthod. -. . arnett , Mahood , guyen M, et al. ephalometric comparison of adult anterior open bite treatment using clear aligners and xed appliances. Angle Orthod. an3-. . herwood , urch , hompson . losing anterior open bites by intruding molars with titanium miniplate anchorage. Am J Orthod Dentofacial Orthop. 3-. . roft . Contemporary Orthodontics. oronto lsevier 3. . oyd . omplex orthodontic treatment using a new protocol for the nvisalign appliance. J Clin Orthod. - uiz 3. . lein M. cephalometric study of adult mild class nonextraction treatment with the nvisalign system master’s thesis. aint ouis, M aint ouis niversity 3. . ossini , arrini , astroorio , et al. fcacy of clear aligners in controlling orthodontic tooth movement a systematic review. Angle Orthod. -. . lkholy , Mikhaiel , chmidt , et al. Mechanical load exerted by - aligners during mesial and distal derotation of a mandibular canine an in vitro study. J Orofac Orthop. 3-3. . ómez , eña M, alencia , et al. ffect of composite attachment on initial force system generated during canine rotation with plastic aligners a three dimensional nite elements analysis. J Align Orthod. 3-3. . omez , eña M, Martínez , et al. nitial force systems during bodily tooth movement with plastic aligners and composite
2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics
attachments a three-dimensional nite element analysis. Angle Orthod. 3-. 3. anda . Biomechanics and Esthetic Strategies in Clinical Orthodontics. t. ouis, M lsevier . . olano-Mendoza , onnemberg , olano-eina , et al. ow effective is the nvisalign® system in expansion movement with x3’ aligners Clin Oral Investig. -.
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. oule , iedade , odescan r , et al. he predictability of transverse changes with nvisalign. Angle Orthod. -. . hao , ang , ang M, et al. Maxillary expansion efciency with clear aligner and its possible inuencing factors. honghua ou iang i ue a hi. 3-.
3
Clear Aligners: Material Structures and Properties MASOUD AMIRKHANI, FAYEZ ELKHOLY, and BERND G. LAPATKI
Introduction The continued improement of medical treatment demands easy to use, cheaper, and more durable products without compromising the treatment outcome itself. ue to inherent properties and aailability, polymeric materials show high potential for medical applications. olymeric materials are lightweight, easy to manufacture, cheap, and ersatile. These properties allow them to be used in dierse medical applications such as implants, prostheses, and orthodontic appliances. s of any material used for medical applications and intraoral applications in particular, the polymer must be biocompatible and must not induce aderse reactions., The restrictions and the standard in choosing a polymer depend on the type of application. In orthodontic applications, polymers are exposed to the intraoral enironment, which comprises seeral different substances including water, electrolytes, enymes, bacteria, among other components. dditionally, consuming different food and drin changes the acidity and ion concentration and may temporarily introduce organic solent e.g., alcohol to the polymer enironment. This means that the polymer must be resistant to chemical corrosion. rincipally, corrosion causes a particle release, which—depending on the sie and form of particles—might inuence the mechanical properties of the polymer as well. nother important aspect is the thermal properties of the polymer. lthough the intraoral temperature remains relatiely constant near °, a polymer could be subected to arying temperature during intraoral application. This means that the intraoral temperature might change from a subero range e.g. while eating ice cream to alues as high as 6° e.g., while drining tea. uch temperature ariations lead to expansion or contraction of the material, which might hae an inuence on the interaction between the polymer and the teeth. Thus, a polymer must be able to tolerate temperature alteration without a pronounced olume and mechanical performance change. The mechanical stability of the polymer also plays an important role in orthodontic applications. or instance, a polymer used for aligners must withstand high occlusal forces otherwise, fractures or deformation might occur. change in the mechanical properties of the polymer during the intraoral application period could also lead to unwanted changes of the mechanical loads applied to the teeth. en for a chemically stable material i.e., a material showing no corrosion, the mechanical properties of the polymer can still ary oer time due to aging and creep.5- 30
There are two types of aging: physical and chemical aging.5 6 Both chemical and physical aging render the polymer brittle and stiffer, thus a lower strain may be generated during the application. This chapter will focus on the basic properties of polymers typically used for aligners. It will also include an explanation of the chemical structure and thermal properties of these polymers. s the effectieness of a polymer for dental use depends on thermal, chemical, and mechanical stability, these issues also will be discussed briey. inally, future perspecties of polymers used for aligners are described.
Polymer Molecular Structure and Thermal Properties olymers are ery long and entangled molecules with nonconentional thermal and mechanical behaior. In this section, the structure of a polymer and its thermal behaior will be described. This comprises the specication of glass transition, aspects of aging, and the stability of the polymer in the intraoral milieu.
WHAT IS A POLYMER? The word polymer is deried originally from the ree words poly “many” and méros “units”. This indicates that polymers consist of many repeating units connected to each another through chemical bonding. ormally, if a substance contains ust a few molecules, an addition or remoal of only a few atoms would change the material properties signicantly. or example, if one would add ust to heptane 6, then the boiling point of the resulting molecule increases by °. ith polymers, in contrast, the number of repeating units could be changed by one or more units without any noticeable change in the polymer properties. Typically, a polymer chain is made of seeral thousand repeating units with a length of seeral micrometers and a diameter ust around nm. The polymer chain is usually exible, twisted, and intertwined. The molecular weight and chemical structure of the polymer determine most of its properties. In contrast to small molecules haing a specic sie and molecular weight expressed in gmol or gmol, a polymer bul contains polymer chains with many different sies and molecular weights. ence the molecular weight of the polymer reects an aerage of many different polymer chains.
3 • Clear Aligners: Material Structures and Properties
31
O C
C
O
CH2
CH2
O
O
n
Fig. 3.1 Chemical structure of polyethylene terephthalate glycol material (PET).
H
O C
N
O
C
N
H
H
C
O
H
H
C
C
O
HH H
n
Fig. 3.2 Chemical structure of polyurethane material (PU).
GLASS TRANSITION-THE MACROMOLECULAR BASIS OF VISCOELASTICITY epending on the temperature, most materials exist in a solid, liuid, or gas state. ach of these states could be precisely described by thermodynamics laws. oweer, the inestigation of polymers reealed that most of them do not follow these basic material states. Instead, they show uid or solidlie, time-dependent characteristics.
ore specically, if a polymer is obsered in a short time scale, it behaes lie a solid material. If the experiment, howeer, is performed during a longer time period, polymers may ow and show a liuidlie behaior. This phenomenon is to be exemplied on the basis of the behaior of a simple liuid ethanol, which normally crystallies. et us assume that the liuid is cooled below its melting point. ig. . illustrates the change of the specic olume of the material ersus its temperature. The specic olume, dened as olume diided by mass, is the reerse of the density. uring cooling, the specic olume of the liuid decreases continually as long as it is still in the liuid phase. There exists, howeer, a point the freeing point at which the specic olume will decrease drastically and form a crystalline solid. uch olume discontinuity is related to the reduction of specic olume due to the crystalliation. Below the freeing point, the specic olume remains almost constant een though the cooling process is continued. The freeing or melting point is a material property and does not depend on the cooling rate or method of the measurement. It also has a clear thermodynamic denition without any room for interpretation. nder certain conditions, small molecules and many types of polymers, howeer, do not follow the mentioned
Liq Specific volume
Based on their thermal behaior, the three different classes of polymers are thermoplastic, elastomer, and thermoset. lear aligners belong to the thermoplastic group. Thermoplastic polymers melt and flow upon heating aboe a certain temperature. Two widely used polymers for aligners are polyethylene terephthalate glycol T- and thermoplastic polyurethane T.- The latter is a special thermoplastic form of polyurethane which melts by heating, facilitating the thermoforming process. Both of these thermoplastic materials are transparent in the isible light spectrum, are impact-resistant, and highly ductile. ust these properties in particular mae them ery suitable for use as aligner material. T- is a copolymer that constitutes two repeating units ig. .: polyethylene terephthalate and glycol. The addition of glycol preents the crystalliation of the T upon heating. This maes T- less brittle and more resistant to mechanical stress. T- is a ersatile polymer used in many other applications such as protectie coer e.g., smart card, electronic deices, food containers, and medical instruments. ne can thermoform, print, drill, bend, polish, and cut T- easily without noticeable impact on its stability and physical properties. s T- can be easily thermoformed and also recycled, it is also the material of choice for three-dimensional printing. The building bloc of polyurethane is urethane ig. .. is aailable in both soft and rigid form, maing it ideal for automotie interiors, pacaging, coating, exible foam, and construction. is impact resistant, is a good electrical isolator, bonds well with other material, and is chemically stable in the presence of water and oil. The ersatility of is due to the fact that one can lin urethane molecules using different chemicals in ery different structures. This allows tailoring the hardness of to the specic application. In general, is biocompatible, but to mae it applicable as aligners, is usually combined with other material.
p Su
erc
oo
-l led
iqu
uid
id
Amorphous Crystalline
Temperature
Tg
Tm
Fig. 3.3 Specic olume ersus temperature. Tm represents the melting temperature and Tg the glass transition temperature.
32
Principles and iomechanics of Aligner Treatment 0.34 0.33 0.32
Heat flow/mass (m/m)
0.31 0.30 0.29 0.28 0.27 0.26 0.25 0.24 0.23 0.22 45
50
55
60
65
70
75
80
85
90
95
100
105
110
Temperature (°C) Fig. 3.4 ifferential scanning calorimetry of polyethylene terephthalate glycol (PET).
scenario but demonstrate another behaior. This is een applicable to simple liuids such as ethanol small molecules. If a ery pure ethanol is stored in a bowl with no corner and in a refrigerator without ibration, it can be cooled to below freeing temperature without freeing. ence there exists a temperature range below the melting point called the supercooled region in which the substance remains liuid. If the cooling process is continued, a temperature range will be reached at which the supercooled liuid transforms into a glassy state called the glass transition temperature Tg. In this solidlie form, the substance has ery different properties than the crystalline state. lassy material is an amorphous material, which does not hae a long-range order. The structure of material in the glassy form is therefore more similar to a liuid than to a crystalline structure. xcept for only a few examples, solid polymeric materials mainly exist in such an amorphous state. This is primarily related to the fact that the polymer’s long chain is entangled with other chains. ence it is usually difcult for the polymer chains to orientate and build an ordered crystalline structure. It has to be noted that simple polymers may actually show crystalliation if the cooling rate is low enough so that the polymer chains are allowed to nd their minimum state of energy i.e., their euilibrium. oweer, for many polymers with entangled chains, moements of polymer chains are hindered too much, maing it physically impossible to reach the crystalline state. The usual state of polymers is, conseuently, solidlie with an amorphous structure. eertheless, the polymer chains retain their tendency to orient and to achiee an euilibrium state. This tendency is the source of the specic behaior of amorphous polymers, which is plastic and elastic-lie, and might alter between these characteristics throughout time.
These aspects explain why the glass transition temperature plays an important role in dening a polymer’s properties, though it must be mentioned that the glass transition temperature is an ill-dened transition. The latter means that different measurement techniues may lead to different Tg alues. ifferential scanning calorimetry is a widely accepted techniue for determination of the Tg alue. ig. . shows results of measurements for T-. sually the middle of this range i.e., 5° for T- is taen as the determined Tg alue. rom an application-oriented iew, any thermoforming must occur aboe the Tg temperature. The exemplied cure further indicates that, if T- is heated aboe 6°, its mechanical properties will change drastically. ore specically, around a temperature of 6°, T- will start to get softer and deform easier. Intraorally, this temperature is usually not exceeded for a sufciently long time, so T- stays mechanically stable during dental applications.
Physical and Chemical Aging of Aligner Polymers In the fabrication process, aligners go through thermoforming. uring subseuent clinical application, they are in contact with salia, food, drins, among other chemicals. onseuently, as the orthodontist reuires a reliable appliance, sufcient material stability is needed under arying conditions. The stability of the aligner is measured by its aging i.e., the change of its properties oer time. olymer aging has seeral sources. ith respect to intraoral application of polymers, two aspects of aging should be considered in particular: physical and chemical aging.5 6
3 • Clear Aligners: Material Structures and Properties
PHYSICAL AGING OF POLYMERS hysical aging of polymers principally occurs, as mentioned earlier, in an amorphous i.e., noneuilibrium form. ery system with the noneuilibrium state tends to decrease its energy to thus approach its euilibrium state. If enough mobility is obtained, the chains may rearrange themseles to their lowest energy state, which might be compared to crystalliation. This in turn will lead to a decrease of the specic olume, a decrease of the enthalpy, an increase of the hardness and brittleness, and changes to other properties.5 This effect particularly changes the mechanical properties of the polymer. ccordingly, physical aging can be dened as the relaxation of a polymer toward a more stable energy state. If the usage of a polymer occurs far below its Tg temperature, the polymer chains will not hae enough inetic energy to moe and rearrange. ence, by choosing an aligner with a Tg alue much higher than the intraoral temperature, physical aging might be largely aoided. It is important to note in this context that a polymer’s Tg alue may also change due to enironmental inuences. hysical aging of polymers can be inuenced by exposure to water and many other inds of molecules in the intraoral medium. s mentioned, the specic olume of an amorphous polymer is high in comparison to a crystalline polymer. This means there exists a lot of free olume in the amorphous polymer below the Tg temperature. onseuently, for prolonged exposure of such a polymer to water, water molecules could diffuse into the material alongside other molecules. The latter is one of the reasons for discoloration of aligners. It is important to note that the absorption of these molecules may also change the properties of the polymer. typical change is called the plasticiing effect.6 To explain further, consider using spaghetti as an example. roided that a bowl contains spaghetti without sauce, the noodles cannot moe as easily because they stic together. oweer, by adding a sauce to the bowl, the spaghetti noodles separate, which enables them to slip along each other. In polymers, the plasticiing effect follows almost the same logic: the small, embedded molecules are placed between the polymer chains to increase the mobility of the chains. The plasticiing effect will reduce the glass transition, and therefore the polymer will be more affected by physical aging. rom a clinical perspectie, physical aging can affect an aligner in two ways. Initially, the polymer will become softer due to the plasticiing effect. s a result, force magnitudes applied to the indiidual teeth are reduced. In the long run, howeer, due to the effect of classical physical aging, aligner polymers become harder which will increase the applied forces and more brittle increasing the ris of breaage.
CHEMICAL AGING OF POLYMERS s introduced, aligners may also suffer from chemical aging, which is the result of a chemical interaction between a polymer and its medium. t present, none of the aailable aligner materials is inert, which means that these materials do react with certain chemicals included in salia, drin, or food. hemical aging can affect a polymer ia different mechanisms. or example, water molecules can brea the
33
polymer chains and shorten them hydrolysis, or a similar reaction can occur due to the interaction between the oxygen and polymer oxidation. polymer suffering from chemical aging is more liely to deelop cracs and induce notch effects. ote, too, the time dependency of the mechanical properties of an aligner might be related to creep which will be explained in the next chapter. reep is different from aging phenomenon. It occurs due to application of mechanical stress to the material, whereas aging is the result of a polymer’s noneuilibrium state or medium, which occurs without any external stress application. Both phenomena are similar to each other, but they are related to uite different mechanisms and should therefore not be confused.
Conclusions and Outlook The two aligner materials mainly used i.e., T and T- hae a distinct chemical structure leading to different responses to thermoforming, exposure to the intraoral milieu, and mechanical stress. ence it is of great importance not to generalie the characteristics determined for one aligner material een one brand. ethodologic conditions for material tests must be as realistic as possible. or example, the mechanical properties of aligner materials differ greatly before and after thermoforming. Thus a realistic test should include the thermoformed material specimen or aligners. urthermore, stress measurements should be performed in a simulated intraoral medium. lso, the production process the method of molding, cooling, etc. affects polymer structure, which in turn might alter the performance of aligner materials. To obtain alid comparisons between tested materials and to achiee reliable treatment results, test procedures and clinical application protocols should be standardied. nly then will the full potential of clear aligners be reealed. ligner manufacturers or dental suppliers should inform users i.e., orthodontists about any changes in the chemical composition and production process. eertheless, it is often rather difcult to obtain such information.
References . illiams . n the mechanisms of biocompatibility. Biomaterials. :-5. . ires , erreira , odrigues , et al. eural stem cell differentiation by electrical stimulation using a cross-lined T substrate: expanding the use of biocompatible conugated conductie polymers for neural tissue engineering. Biochim Biophys Acta. 55:5–6. . umphrey , illiamson T. reiew of salia: normal composition, ow, and function. J Prosthet Dent. 5:6–6. . idaa , Iwasai , aito , et al. Inuence of clenching intensity on bite force balance, occlusal contact area, and aerage bite pressure. J Dent Res. :6-. 5. odge I. hysical aging in polymer glasses. Science. 56: 5–. 6. rissman , cenna B. hysical and chemical aging in and their effects on creep and creep rupture behaior. J Polym Sci B Polym Phys. :6-. . iggleman , chweier , ablo d. onlinear creep in a polymer glass. Macromolecules. :6-6. . Bower I. An Introduction to Polymer Physics. ambridge: ambridge niersity ress .
34
Principles and iomechanics of Aligner Treatment
. ombardo , artines , aanti , et al. tress relaxation properties of four orthodontic aligner materials: a -hour in itro study. Angle Orthod. :-. . ancini , arinci , ollino I, et al. implicity and reliability of Inisalign® system. ur J Inamm. :-5. . lexandropoulos , l abbari , inelis , et al. hemical and mechanical characteristics of contemporary thermoplastic orthodontic materials. Aust Orthod J. 5:65-. . lesandro , aurin . study of polymers. I. ighly elastic deformation of polymers. Ruer hem Technol. :6-.
. edde . Polymer Physics. ordrecht: pringer etherlands . . oi , dwards . The Theory o Polymer Dynamics. xford: larendon ress 6. 5. trui . Physical Aging in Amorphous Polymers and Other Materials. lseier cience . 6. mirhani , orini , eporini . econd harmonic generation studies of intrinsic and extrinsic relaxation dynamics in polymethy methacrylate. J on ryst Solids. 55: -.
4
Inuence of Intraoral Factors on Optical and Mechanical Aligner Material Properties FAYEZ ELKHOLY, SILVA SCHMIDT, MASOUD AMIRKHANI, and BERND G. LAPATKI
Introduction
Water Absorption
he triad of success of orthodontic therapy comprises patient compliance, biomechanical nowledge, and, for the therapy with aligners, sufcient understanding of the thermoplastic material used. hapter addressed the basic chemical and mechanical properties of commonly used aligner materials. his chapter will focus on the inuence of different intraoral factors on the mechanical and optical properties of aligner materials. o achieve an efcient orthodontic tooth movement, single aligners are usually worn for a period of to days and approimately hours per day. uring their period of use, aligners are subjected to a prolonged eposure to different factors that are inuencing their properties. hey can be subdivided into two main categories. n the one hand, there are factors inducing optical material changes, either in the form of discoloration or increased opacity such effects are related to the presence of salivary enymes, plaue, and food and beverage coloring.- n the other hand, there are factors affecting the mechanical properties of aligners, including the periodic loading and unloading of the material during its clinical handling, combined with uneven local stress and strain distribution. t must be noted, too, that ecessive occlusal forces e.g., during involuntary clenching or grinding and intraoral temperature uctuations may inuence an aligner’s properties., As this appliance, however, is to be removed during food or liuid intae and worn for only a relatively short period, the clinical relevance of the latter two factors may not be overemphasied. he following sections will discuss the mechanisms of how intraoral factors influence optical and mechanical aligner properties and describe the clinical implications. articular attention will be given to describing the material-specific characteristics of the two aligner materials mainly used i.e., thermoplastic polyurethane and polyethylene terephthalate glycol -. is used, for instance, in the nvisalign system Align echnology, anta lara, A, nited tates or Aligner weden artina, ue arrare, adova, taly, whereas - is used in the lear Aligner system uran, cheu ental mbH, serlohn, ermany and the ssi system ssi A1, entsply aintree ssi, arasota, , nited tates.
Aligners are constantly subjected to saliva, which consists of 99% water. Hence it is crucial to understand the mechanism and effects of water absorption as well as the inuence of water absorption on the mechanical material properties. As stated in hapter , amorphous polymers such as and - possess relatively low molecular density, which provides free volume for water intae. A previous study comparing these two materials showed that shows higher water absorption characteried by a weight increase of .% after a -wee water storage than - showing only a .% increase.9 esides this weight effect, penetration of thermoplastic materials by water molecules also leads to modication of their internal structure. As eplained in hapter , this will result in plasticiation because lins between polymer chains are weaened or even destroyed, which reduces the internal cohesion and increases the molecular mobility. he resulting loss of elasticity might eplain the appearance of internal cracs observed in aligners after clinical usage. t is interesting to note in this contet that own studies on - material characteristics using three-point bending of thermoformed rectangular specimens revealed that the sole water storage without subjecting the material to any mechanical loads has only a minor impact on the mechanical material characteristics ig. .. n contrast, if - is subjected to both water and a continuous mechanical load, the effect on the mechanical properties is much more pronounced, as indicated by the reduction of the bending forces of up to % see ig. .. rincipally, water absorption could also induce dimensional changes of the aligners, nown as hygroscopic epansion. n theory, this factor—besides other factors such as the initial play between the aligner and the setup model-—might affect the t of the aligners and, conseuently, might also induce an alteration of the forces applied to the individual teeth.9 A previous study on water adsorption of thermoplastic materials, however, did not nd signicant and plausible correlations between the rate of water absorption and the amount of hygroscopic epansion.9 or instance, showed a lower hygroscopic epansion, although it showed the highest water absorption rates. 35
36
Principles and Biomechanics of Aligner Treatment
Bending forces for PETG specimens
Force (N)
8 7 6 5 4 3 2 1 Dry (unloaded)
24 h loaded under dry conditions 24 h loaded + immersed in water
24 h immersed in water (unloaded)
Fig. 4.1 Bending forces depending on the (dry or wet) storage conditions and the unloaded or loaded condition. Note 0.75mm polyethylene terephthalate glycol (PET-G) specimens were inestigated in a threepoint ending set ting with a span length of mm at a deection of 0. mm. The specimens were either only thermoformed and then underwent only one short deection with simultaneous force stored for hours in water without loading loaded continuously for hours without water immersion or loaded continuously for hours with water immersion. The error ars represent the standard deiation for the different measurements.
Optical Changes ne of the main reasons for the popularity of aligners with patients lies in the invisibility or better the transparency of this appliance.- hese characteristics should be maintained throughout the treatment period because a discolored or opaue aligner ig. . might jeopardie the patient’s motivation and compliance. Aligner discoloration is primarily related to supercial absorption or penetration of pigmentations in food and beverages. offee i.e., the highest chromogenic agent, blac tea, and red wine play a prominent role. t is noticeable in this contet that the rate and etent of discoloration is material-specic. t seems that -based aligners might ehibit faster discoloration rates than - aligners. A possible eplanation for this difference is the higher water absorption capability of facilitating the accumulation of the pigments.9 n addition, the higher surface roughness of might also facilitate the adhesion of pigments on the polymer lm’s surface. Aligners might also lose translucency by the development of internal microcracs, formation of calcic
A
integuments, or the accumulation of plaue on the aligner surface.-,9 bviously, the two latter changes do not have a signicant impact on the treatment success due to the short application period of each single aligner of maimally wees. oreover, the loss of translucency can be minimied by maintaining good aligner hygiene through regular brushing with neutral soap and the use of denturecleaning effervescent tablets containing sodium bicarbonate or sodium sulfate.
Short-Term Mechanical Loading of Aligner Materials SINGLE SHORT-TERM LOADINGS or viscoelastic materials, it is nown that during very short loading periods the elastic component dominates. his thesis was also conrmed by unpublished investigation of - specimens by our group, consisting of two short loadingmeasuring cycles with a duration of only ca. . second each and a -minute brea in between. he comparison of the
B Fig. 4.2 nisalign aligners. (A) Prior to rst intraoral application. (B) After a wee wearing period.
4 • nuence of ntraoral actors on ptical and echanical Aligner aterial Properties
Force measured at short-term deflection 8 7
Force (N)
6 5 4 3 2 1 0 First loading
Second loading
Fig. 4.3 orces measured for 0.75mm polyethylene terephthalate glycol (PT) specimens in a threepoint ending setup with a span length of mm. The central support was deected y 0. mm. Two short loadingmeasuring cycles with 0.second duration separated y a minute recoery rea were performed.
forces obtained by the rst and second measurements did not show a signicant difference ig. ..
MULTIPLE SHORT-TERM LOADING CYCLES uring clinical application, aligners are removed multiple times for food and liuid intae as well as during the regular oral hygiene procedures. o simulate or eemplify such scenarios, our group conducted an in vitro study, including cyclic loading of .-mm-thic specimens using a three-point bending setup. ach of the cycles consisted of a -minute loading interval, followed by a nearly unloaded interval of minutes during which the deection was reduced to a level at which the remaining force was just above to maintain contact between the force-measuring device and the specimen. As revealed by ig. ., the - specimen showed a continuous stress relaation behavior during the -minute loading periods with a force reduction of ca. % average over the loading-unloading cycles. t was also observed that during the -minute uasi unloaded period, a slight average increase of the deection forces by ca. .% occurred. uch force increase indicates a slight recovery of the - material see ig. .. n some studies, such recovery is described as “relaation” the latter epression, however, should not be mistaen for “stress relaation,” which describes a completely opposite phenomenon. t is noteworthy that a similar material behavior was found in another in vitro study in which --aligners were repeatedly removed from a test model. his previous study observed a clear decrease of aligner force delivery in the course of the aligner seating-removal procedures. oreover, the force reduction showed a nearly linear relation with the freuency of the cycles, with force values dropping down to % of the initial forces after cycles ig. .. urther wor is reuired to systematically eamine this aspect for other materials than -.
37
OCCLUSAL FORCES n addition to the specic loading of aligners related to repeated intraoral seating and removal, aligners are also potentially eposed to relatively high mechanical loads occurring during occlusal contacting. uch bite forces are particularly relevant in patients showing clenching or grinding where they may reach force values up to per single molar. Although possesses higher abrasion resistance than -, available studies indicate that both materials showed delamination and abrasion as well as an increased icers hardness, particularly in the posterior region of the dental arch.,,,9,, he latter was observed after a -wee wear period and was traced bac to the changes in the crystalline structure of the polymer under cold wor. evertheless, the clinical impact of these changes appears unproblematic for two reasons irst, those teeth mainly affected by the altered material behavior i.e., the buccal teeth are moved to a minor etent during aligner therapy second, the wearing period of an aligner ranging between and wees seems too short for the mechanical destruction of an aligner by contact forces.
Long-Term Loading Aligner materials such as and - show a viscoelastic behavior. Hence they show both elastic and viscous characteristics when undergoing loading, resulting in a time-dependent deformation. uring very short loading periods, the elastic component dominates. he timedependent viscous component, in contrast, reveals primarily during prolonged loading. he viscoelastic behavior can be mathematically described as standard linear solid models ig. .. uch models consist of springs and dashpots representing the elastic and viscous material components, respectively. perimental description of the mechanical behavior of a viscoelastic material is possible by two variables creep or stress relaation. t is important to clarify the difference between these two parameters ig. .. reep describes the phenomenon of increasing mechanical strain over time in case of a constantly applied stress or force, respectively. ince the mechanical load stress is maintained at a constant level, creep eperiments induce a continuous deformation strain see ig. .A until a maimum strain is reached. tress relaation, in contrast, describes the gradual stress decrease over time under a constant strain and deformation, respectively see ig. .. As a result, the force level drops continually until a certain euilibrium state is reached at a reduced stress level. o ensure a better understanding of the viscoelastic properties of polymers, it is important to consider the specic test method applied. reep is usually eamined either by tensile measurements or by instrumental indentation tests. ensile measurements are usually performed by loading the specimens at a certain force level, which is then maintained for a certain period. he rate of elongation of the specimen describes the creep rate of the tested material. nstrumental indentation is more common and usually uantitatively evaluated by calculating the percentage difference between
Principles and Biomechanics of Aligner Treatment
Short-term repeated loading 7 B 6
Force (N)
5 4 3 2 1 0
C 0
60
A
120
180
Time (min)
6.75
0.5 x Force (N)
y
Force (N) 6.25
0 0
10
B
20
35
C
Time (min)
45
55 Time (min)
Fig. 4.4 (A) orces measured during multiple 5minute loading and 5minute loading cycles for a 0.5mm polyeth ylene terephthalate glycol (PT) specimen in a threepoint ending setup with a span length of mm and a deec tion of 0. mm. (B) nlargement of a data segment (see top of A) showing the gradual force decrease during the 5minute loading time. () nlargement of a data segment (see bottom of A) showing the slight force increase during the 0minute minimal load time at the corresponding deections.
Change in the mean force for different aligner removal frequencies 18 16 Mean force in (n)
38
14 12 10 8 6 4 2 0
0
10
20 30 40 Removal frequency (x times)
50
Fig. 4.5 Aerage force reduction reported for polyethylene terephthalate glycol (PT) aligners in the course of 50 aligner seatingremoal procedures ased on the data pulished y ai et al. 0 The error ars indicate the standard deiation.
65
4 • nuence of ntraoral actors on ptical and echanical Aligner aterial Properties
A
3
B
Fig. 4.6 chematic modeling of iscoelastic material ehaior using a standard linear solid model. (A) awell representation of a standard linear solid model. (B) elin representation of a standard linear solid model. uch models comine springs and dashpots in a certain arrangement to descrie the oerall ehaior of a system under different loading conditions. prings represent the elastic component of a iscoelastic material whereas dashpots represent the iscous component.0 ue to comination of such elements an applied stress aries with the time dependent change of the strain.
Stress relaxation
Creep
Stress
Strain
Stress-strain
Stress-strain
Strain
Stress
A
Time
B
Time
Fig. 4.7 Two fundamentally different eperiments and parameters respectiely descriing the timedependent ehaior of a iscoelastic aligner material. (A) The creep phenomenon is osered if the load (and stress leel respectiely) is ept constant oer time. (B) The stress relaation ehaior is characteried y loading the material under constant strain and deection respectiely.
the initial and nal indentation depth during the constant force application period. Hence it is determined how deep the material has been penetrated over the designated period. tress relaation, on the other hand, can be tested either by three-point bending or in tensile eperimental setups.,9 A common feature of both setups is the constant deection strain of the specimen for a dened period during which the time-dependency of the stress is registered. he difference between the initial and residual values over time denes the stress relaation rate. Aligner materials with lower creep resistance tend to a faster strain deformation under constant mechanical stress. hen transferred to the clinical situation, such behavior would reduce the mechanical load applied to the
teeth because the relative discrepancy between the actual tooth position and its position in the aligner would diminish. A previous study investigated the creep behavior of the different thermoplastic raw lms used in the nvisalign Align echnology, anta lara, A, A, lear Aligner cheu ental mbH, serlohn, ermany, and ssi A1 entsply aintree ssi, arasota, , A systems by means of indentation creep eperiments. he indentation creep behavior was characteried by the percentage increase of the indentation depth within an interval of minutes in with the specimens were subjected to a constant indentation force., esults of this study revealed more pronounced creep for modied , which is the material of nvisalign aligners .% compared to
Principles and Biomechanics of Aligner Treatment
the corresponding percentage for - .%. Another study observed that the creep of was even more pronounced after aging, with an increased indentation depth of %. revious research determining the stress relaation behavior of commercial aligner materials revealed that most materials show a relatively high stress relaation rate in the rst hours of loading, followed by a nearly steady plateau. he stated stress decay, however, showed a material-dependent pattern with the highest stress relaation for - with % of the initial stress values, followed by the stress relaation of with .%. After the -hour loading period, a similar material-dependent pattern was observed with residual stresses of .% and % of the initial values for the and the - materials, respectively. imilar stress relaation patterns were found by our group investigating - specimens lear Aligner, cheu ental mbH, serlohn, ermany during a -wee constant deection period with water immersion of the specimens. ur results also indicated relatively rapid stress relaation during the rst day, followed by a slower stress reduction. At the end of the longer -wee loading period, stress values approimated a residual stress value of only % of the initial stress ig. ..
Clinical Loading atterns of Aligner Materials As mentioned, aligner materials possess elastic elements, which are of utmost importance for maintaining a certain force level on the teeth. f their load-deection behavior would be purely elastic, and the strain would be ept within the elastic range, then the force and moment components applied to the teeth would be directly proportional to the discrepancy between the actual tooth position and the programmed tooth position in the aligner. urthermore, the stiffness of the aligner material would describe the slope of this interrelation. As pointed out earlier, in case the load is maintained for a longer time, these materials also show a
Stress relaxation for Duran® PET-G specimens over a 7-day period 100% Nomralized stress relaxation (%)
4
80% 60% 40% 20% 0% 2
0
3 4 Time (days)
Unloading interval
60%
Loading interval
Force decay (%)
80%
0% 1
2
7
viscous behavior that can be uantied, for instance, by stress relaation eperiments. t is important to note that both the amount and the rate of deformation of thermoplastic materials depend on the loading time scheme and the stress magnitude, and both are affected by collateral factors such as the temperature and material-specic water absorption properties. Another important characteristic of thermoplastic aligner materials is observed in cases where the load is removed. nder this condition, thermoplastic materials may show a certain rebound effect. bviously such a phenomenon might be of practical importance as during clinical therapy, aligners are usually removed periodically e.g., for food intae. o investigate this characteristic, recent research in our lab aimed at the eamination of the inuence of repeated -hour loading-hour unloading cycles on the force application of - aligner materials over a total period of wee. An eample of a measurement curve is presented in ig. .9. imilar to the eperiments with constant strain, the results indicated a relatively high force decay in the rst few hours to a level less than % of the initial
100%
20%
6
Fig. 4.8 Normalied stress relaation for polyethylene terephthalate glycol (PET-G) materials loaded for wee in a threepoint ending setup with a constant deection of the specimen leading to a constant strain.
Stress relaxation of PET-G
40%
5
3 4 Measurement time (days)
6
Fig. 4. ecay of the forces measured after the loading and unloading periods during the wee oseration time.
4 • nuence of ntraoral actors on ptical and echanical Aligner aterial Properties
force indicating a clear stress relaation. After the -hour periods without loading, only slight force increases were observed. ven though after the second and following loading periods stress relaation could be observed, the latter was much less pronounced than that occurring in the rst loading period. ased on these ndings, we concluded that the stress relaation behavior of -, which is related to repeated loading and unloading intervals with similar lengths as those typically occurring during clinical therapy, tends to stabilie at a level between % and % of the initial stress.
. . . . .
References . oyd , iller , lasalic . he nvisalign system in adult orthodontics mild crowding and space closure cases. J Clin Orthod. -. . iu , un , iao , et al. olour stabilities of three types of orthodontic clear aligners eposed to staining agents. Int J Oral Sci. -. . afeiriadis AA, aramouos A, Athanasiou A, et al. n vitro spectrophotometric evaluation of ivera clear thermoplastic retainer discolouration. Aust Orthod J. 9-. . ernandes A, uellas A, Ara√∫jo A, et al. Assessment of eogenous pigmentation in colourless elastic ligatures. J Orthod. -. . evrini , ovara , argherini , et al. canning electron microscopy analysis of the growth of dental plaue on the surfaces of removable orthodontic aligners after the use of different cleaning methods. Clin Cosmet Investig Dent. -. . liades , ourauel . ntraoral aging of orthodontic materials the picture we miss and its clinical relevance. Am J Orthod Dentofacial Orthop. -. . chuster , liades , inelis , et al. tructural conformation and leaching from in vitro aged and retrieved nvisalign appliances. Am J Orthod Dentofacial Orthop. -. . Aleandropoulos A, Al abbari , inelis , et al. hemical and mechanical characteristics of contemporary thermoplastic orthodontic materials. Aust Orthod J. -. 9. yoawa H, iyaai , ujishima A, et al. he mechanical properties of dental thermoplastic materials in a simulated intraoral environment. Orthod Waves. -. . oubari A, lleuch , uermai , et al. nvestigations on hygrothermal aging of thermoplastic polyurethane material. Mater Des. 99-9. . lholy , anchaphongsapha , ilic , et al. orces and moments delivered by - aligners to an upper central incisor for labial and palatal translation. J Orofac Orthop. -. . lholy , chmidt , äger , et al. orces and moments applied during derotation of a maillary central incisor with thinner aligners
. 9. .
. . . . . . . . 9. .
41
an in-vitro study. Am J Orthod Dentofacial Orthop. -. lholy , ihaiel , chmidt , et al. echanical load eerted by - aligners during mesial and distal derotation of a mandibular canine an in vitro study. J Orofac Orthop. -. hang , ai , ing , et al. reparation and characteriation of thermoplastic materials for invisible orthodontics. Dent Mater J. 9-99. eremiah H, ister , ewton . ocial perceptions of adults wearing orthodontic appliances a cross-sectional study. Eur J Orthod. -. osvall , ields H, iuchovsi , et al. Attractiveness, acceptability, and value of orthodontic appliances. Am J Orthod Dentofacial Orthop. 9, e- discussion -. halish , ooper-aa , vgi , et al. Adult patients’ adjustability to orthodontic appliances. art a comparison between abial, ingual, and nvisalign™. Eur J Orthod. -. chott , ö . olor fading of the blue compliance indicator encapsulated in removable clear nvisalign een® aligners. Angle Orthod. -9. racco A, aoli A, avoni , et al. hort-term chemical and physical changes in invisalign appliances. Aust Orthod J. 9-. ai A, ei , Abusama , et al. ffects of time and clear aligner removal freuency on the force delivered by different polyethylene terephthalate glycol-modied materials determined with thin-lm pressure sensors. Am J Orthod Dentofacial Orthop. 99-. Hattori , atoh , unieda , et al. ite forces and their resultants during forceful intercuspal clenching in humans. J Biomech. 9-. ejaovic´ , isa , rane . Abrasion resistance of selected commercially available polymer materials. Finn J riol. -. oomali , uresha , ee H. echanical and three-body abrasive wear behaviour of A blends. Mat Sci Eng AStruct. 9-9. ust . ichtlineare FiniteElementeBerechnungen ontat, eometrie, aterial. nd ed. iesbaden ieweg1eubner erlag pringer achmedien iesbaden mbH iesbaden . ombardo , artines , aanti , et al. tress relaation properties of four orthodontic aligner materials a -hour in vitro study. Angle Orthod. -. i , en , ang , et al. hanges in force associated with the amount of aligner activation and lingual bodily movement of the maillary central incisor. orean J Orthod. -. radley , ese , liades , et al. o the mechanical and chemical properties of nvisalign appliances change after use A retrieval analysis. Eur J Orthod. -. ondo’ , aini , erroni , et al. echanical properties of “two generations” of teeth aligners change analysis during oral permanence. Dent Mater J. -. ang , hang , hen H, et al. ynamic stress relaation of orthodontic thermoplastic materials in a simulated oral environment. Dent Mater J. 9-9. oylance . Engineering iscoelasticit. ambridge, A assachusetts nstitute of echnology 9.
5
Theoretical and Practical Considerations in Planning an Orthodontic Treatment with Clear Aligners TOMMASO CASTROFLORIO, GABRIELE ROSSINI, and SIMONE PARRINI
Introduction After the Stone Age, the Iron Age, and the Bronze Age, are we switching to the Polymer Age? This question is legitimate when examining the increase of plastic materials produc tion during the last halfcentury In the last decades, plastics hae permeated industrial technology Plastic materials hae replaced many materials used in the past, and they hae made possile industrial and medical applications that would not hae een possile with older technologies The ey to the widespread dissemi nation of these materials is their incredile ersatility urthermore, we are liing in the personalized medicine era Personalized medicine represents the natural eolution of health care hen medicine is informed solely y clinical practice guidelines, the patient is not treated as an indiid ual ut as a memer of a group Personalized or precision medicine characterizes unique iologic characteristics of the indiidual to tailor diagnostics and therapeutics to a specic patient Personalized medicine uses additional in formation aout the indiidual deried from nowing the patient as a person rthodontists hae always een educated in collecting and analyzing patients’ indiidual characteristics to per form a diagnosis and dene a personalized treatment plan In this iew, orthodontics will e the pioneer in guiding dentistry into the personalized medicine process hat is still missing is the integration of iologic marers into the diagnostic process and treatment planning, ut researchers are going to ll the gap In the last century, orthodontics was mostly a matter of metals and predened prescriptions In the last decades, the introduction of clear aligners moed the attention toward thermoplastic materials and their possile applications and personalized prescriptions In clear aligner therapy AT, eery aligner is uilt for a specic stage of orthodontic tooth moement T of a specic patient Aligners are com fortale, less isile, and more aesthetically pleasant com pared with uccal xed appliances they can e remoed for eating and oral hygiene procedures, reducing the occur rence of emergencies espite those adantages maing clear aligner increasingly requested y patients in our eautyconscious society, there was always a great deate 42
inoling efcacy and efciency of this appliance in con trolling T or instance, questions hae een raised re garding the extent to which aligners can control extrusion, rotation, odily moement, and torque As stated y Proft in , effectieness, efciency, and predictaility are the three things orthodontists need to now aout the treatment they are proiding A recent reiew stated that AT can control complex moements as maxillary molars odily distalization and extraction spaces close and that the uccolingual inclination of inci sors is well controlled in mild to moderate malocclusions urthermore, in a recent research paper, rünheid et al analyzed the differences etween predicted and achieed tooth positions and found statistically signicant differ ences for all teeth except maxillary lateral incisors, ca nines, and rst premolars In general, anterior teeth were positioned more occlusally than predicted, rotation of rounded teeth was incomplete, and moement of posterior teeth in all dimensions was not fully achieed oweer, except for excessie posttreatment of uccal crown torque of maxillary second molars, these differences were not large enough to e clinically releant Therefore, with respect to what was possile a few years ago when the recommendation was to treat only simple malocclusions with aligners, the growing ase of common nowledge regarding the control of T made it possile to use this technique een in more complex cases with good results when compared to conentional xed orthodontics Those results were made possile thans to orthodontists who started to consider the irtual setup not only to isual ize moing teeth ut as an instrument to design the proper iomechanics, starting to transfer wellnown concepts in this eld As stated y Burstone during a JCO interiew The nice thing about scientic biomechanics is that it is not dependent on any given appliance or technique. No matter what appliance you use, it allows you to use it better with more predictable results. Today, we have much too much commercialism in orthodontics a healthy dose o science in understanding appliances and how they wor is a good antidote. t is interesting to note that many o the new appliances that are suggested are nothing more than reinventions o old appliances.
5 • Theoretical and Practical Considerations in Planning an Orthodontic Treatment with Clear Aligners
Theoretical and Practical Considerations in CAT Based on these assumptions and on clinical and laoratory research, the iomechanics of clear aligners could e de scried as a sequence of crown tipping and root uprighting The rst part of moement occurs in the occlusal part of the tooth ecause the aligner enelopes the entire tooth crown, while the interactions etween aligner and attachments de termine root moement Therefore, when designing a irtual treatment plan, we must always rememer which is the inter action surface etween the aligner and the tooth, which is the effect of the force application at the crown leel, and which is the anchorage unit required to aoid undesired moements The analysis of a irtual treatment plan using dedicated software should e ased on the following steps
43
egarding the nal position of upper maxillary molars, it is recommendale to refer to the position indicated y icetts in in which the line connecting the distouc cal and the mesiolingual cusps of the upper rst molar is passing through the cusp of the opposite canine at the end of treatment This nal position is ased on precise anatomic landmars and can preent misunderstandings etween the prescriing clinician and the technician trans ferring the information in the irtual treatment plan urthermore, when dening the nal position, the clini cian should always consider the uccal and the frontal limits of the arches, considering one and periodontal sup port and the cephalometric information Those indications are ery important to aoid excessie expansion andor proclination moements that can result in seere periodontal iatrogenic effects
Analysis of the nal position Analysis of the moements occurring at each stage for each tooth
ANALYSIS OF THE MOVEMENTS OCCURRING AT EACH STAGE FOR EACH TOOTH
ANALYSIS OF THE FINAL POSITION
Aligner auxiliaries Anchorage management and moement sequentialization T staging
According to Sarer et al it may e inappropriate to place eeryone in the same esthetic framewor and een more prolematic to attempt this ased solely on hard tis sue relationships since the soft tissues often fail to respond predictaly to hard tissue changes eertheless, it is ac cepted that esthetic considerations are paramount in plan ning appropriate treatment ut that rigid rules cannot e applied to this process In iew of our inaility to apply rules dening optimal esthetics, the use of scientic methods to plan the most esthetic treatment may therefore e compli cated eertheless, it is clear that laypeople can identify arious factors affecting smile esthetics Thus clinicians can expect their patients to e more attentie to some dental esthetic factors than they are to others A recent reiew was conducted to dene the minimum leel of esthetic harmony that can e approed as pleasur ale y an external oserer The indications proided in ig represent the threshold of acceptance of smile es thetics proided y laypeople that should e considered when analyzing the nal position of front teeth
The analysis of moements occurring in eery stage should consider three different aspects
Aligner Auxiliarie Since the introduction of orthodontic aligners in early s, seeral auxiliaries hae een adopted from manufac turing companies and from clinicians to preent anchorage loss and maximize treatment efciency The most commonly adopted auxiliaries could e classi ed as follows n n n n
Attachments and pressure areas Intraoral elastics Interproximal enamel reduction IP Temporary anchorage deices TAs
Attachments and Pressure Areas. sing aligners without attachments is something lie or thodontics ut not orthodontics Attachments are useful to guide teeth in a determined direction ut are also useful in proiding anchorage control depending on the type of
Fig Thresholds of acceptance of smile esthetics from laypeople point of view.
44
Principles and Biomechanics of Aligner Treatment
planned orthodontic moement The use of attachments is crucial to achiee effectie treatments aera et al and arino et al demonstrated the importance of using at tachments to improe the root control of distalizing molars in class II treatments In an in itro study, Simon et al dem onstrated that load transfer from aligners to teeth without the use of attachment is possile only to a limited extent Attachments are diided into two categories onentional attachments rectangular, eeled, or ellipsoid ptimized attachments onentional attachments igs , , and can e positioned y the clinician on eery tooth compatily with tooth dimension and can e oriented in any direction ectangular attachments are usually placed to increase anchorage in posterior teeth or to reinforce the retention of the aligner ptimized attachments ig are positioned y tech nicians, and the orthodontist is not ale to modify their position, dimension, and orientation This ind of attach ment was introduced to generate a dedicated couple of force during rotations, especially in canines and premolars The “play” of aligners on teeth and attachments is an other ey factor in producing desired outcomes, which is strictly related to attachment application An in itro study y asy et al demonstrated that attachment shape affects retention ectangular attachments are more retentie
Fig 4 Rectangular attachments on posterior teeth in Align Technology ClinCheck software.
Fig Optimied and conventional attachments in Align Technology ClinCheck software.
Fig 2 Rectangular attachments on posterior teeth in CA Digital software.
Fig 3 Rectangular attachments on anterior teeth in CA Digital software.
than ellipsoid ones Two in itro studies demonstrated that aligners produced y different companies Inisalign, Align Technology, San osé, A, SA A lear Aligner, Scheu ental, Iserlohn, ermany Aligner, Sweden ar tina, ue arrare, Italy showed excellent tting on teeth and attachments, aligners seem to hae the est alues in terms of tting on attachments the alues range from to mm The Inisalign tting ranges from to mm The measured alues for A lear Aligner analy sis range from to mm asy et al demonstrated that edgeless aligners generated signicantly lower forces than those with a wider edge The increased force might e due to the enhanced stiffness caused y material shape onse quently, the enhanced stiffness may reduce the tting of the aligner on the attachments This could e the reason why A aligners showed the worst results in terms of tting oweer, despite the statistical signicance, measured dif ferences might not e clinically releant Therefore the play of aligners on teeth and attachments is minimal, resulting in a precise transfer of the mechanical properties of the thermoplastic material to teeth rom a iomechanical point of iew, only a few studies in existing literature hae analyzed the interaction etween aligners and attachments An efcient method for studying aligner mechanics is the nite element method Ap plications of on aligner studies will e presented in the next parts of this chapter xcept for the ooi et al study, reported results will refer to the initial instance of
5 • Theoretical and Practical Considerations in Planning an Orthodontic Treatment with Clear Aligners
aligner wearing thus these results should e considered in terms of initial force systems and displacements, not taing into account such precise measurements of the amount of moement expressed y the aligner on teeth sing , omez et al inestigated a theoretical mm displacement of an isolated upper canine with and without a composite attachment The attachment considered for this analysis was inspired y the “optimized attachments” adopted y Align Technology to increase root control during distaliza tion The authors osered uncontrolled distal crown tipping without the attachment and a displacement similar to odily moement with the attachment Thus the authors highlighted the difculty to otain a controlled moement in AT using only aligners and suggested the use of composite attachments to increase root control The iomechanical explanation of attachments useful ness in controlling tooth moement could e related to the role of races in xed orthodontics hile in xed appliance orthodontics the moment is deeloped in the racet itself y the engagement of the wire, in AT it is deeloped y the interaction of aligner and auxiliaries The aligner with out attachments tends to moe away from the teeth in its gingial edge In such eentuality, all force is concentrated only in the occlusal part, and no couple of force could e generated hen recurring to attachments, the interaction etween the displacement applied to the aligner and the at tachment generates the adequate forces and moments to otain a more controlled moement ooi et al in pulished a paper that demonstrated these concepts using to compare upper incisor dia stema closure without attachments and with optimized ones As reported y authors, the initial displacement cor responded to uncontrolled crown tipping for oth the simu lations howeer, after hundreds of iterations that simu lated the one remodeling process, the simulation without attachments resulted in uncontrolled tipping, while odily moement was osered in the simulation with optimized attachments egarding pressure areas, the ind of moements in which they are adopted depends on the aligner manufacturer su ally, pressure areas are adopted to improe efciency in crown tipping, rotations, and root torquing Barone et al in their study from reported that pressure areas are
4
the most effectie auxiliaries in lower incisors tipping, een more than rectangular attachments A study y astro§orio et al regarding control of root moement demonstrated the efcacy of pressure areas to improe this type of moement The force couple gener ated y an aligner torquing a tooth consists of a force near the gingial margin and a resulting force produced y moement of the tooth against the opposite inner surface of the appliance near the incisal edge Since the gingial edge of the aligner is elastic, it is difcult to control the forces applied in this region without an altered geometry Intraoral Elastics. egarding intraoral elastics, three main ariales could in§uence the right choice for the planned treatment orcelength Application point Application surface igs through refer to upper molar distalization, which will e thoroughly analyzed in the following chap ters, and present the effects of elastics on teeth and aligners while changing application point The same elastic in, oz was applied so that the forcelength ariale would not affect the analyzed ones The difference in aligner defor mation and teeth initial displacement during second upper molar distalization could e osered In the preiously cited study, omez et al osered an intrusie effect on the canine due to an unexpected defor mation of the aligner during distalization A loose tting etween aligner and tooth would achiee inadequate con tact with the gingial optimized attachment and thus fail to produce a correct couple of force This eentuality could e aoided y class II elastic that assists during distalization moement proiding anchorage with the sagittal compo nent of elastic force and preenting intrusion thans to its ertical component Interproximal Reduction. Since rst descried y Ballard in , IP has een a procedure dedicated to mildtomoderate crowning cases oweer, in the last years, the digitalization of treatment planning increased the adoption of this technique to otain
Fig nitial tooth displacement of second molar distaliation with class elastics applied directly on upper canine (sagittal view).
4
Principles and Biomechanics of Aligner Treatment
Fig nitial tooth displacement of second molar distaliation with class elastics applied directly on upper canine (occlusal view)
Fig nitial tooth displacement of second molar distaliation with class elastics applied on aligner at upper canine level (occlusal view).
Fig nitial tooth displacement of second molar distaliation with class elastics applied on aligner at upper canine level (sagittal view).
Fig nitial aligner displacement of second molar distaliation with class elastics applied directly on upper canine.
space during orthodontic treatment, also improing its ac curacy and precision uring AT digital planning, the IP amount is calculated ased on digitally performed dental index scores Bolton index, ittle index, space analysis, etc, and the timing of IP is programmed to otain the est in terproximal surface access and to aoid premature tooth surface collisions As demonstrated y seeral authors, IP is a safe procedure for tooth health, which does not increase
the riss of interproximal caities and tooth demineraliza tion, egarding IP maximum amount, in Sarig et al analyzed extracted intact anterior and posterior teeth from oth maxilla and mandile The authors re ported that the existing guidelines of mm max IP for each interproximal space could e conrmed for anterior region, while in the posterior region it could e increased to mm
5 • Theoretical and Practical Considerations in Planning an Orthodontic Treatment with Clear Aligners
4
Fig nitial aligner displacement of second molar distaliation with class elastics applied on aligner at upper canine level.
Temporary Anchorage Devices. Aligner treatment with TAs is thoroughly analyzed in hapter
Anrage Manageen an Meen Seuenialiain Anchorage management represents the ey for a successful orthodontic treatment In xed orthodontic treatment, auxiliaries such as laceacs, tieacs, and elastics are ad opted to reinforce anchorage when needed, principally dur ing the woring phase of treatment espite the widespread use of aligner orthodontics, no iomechanical studies are present to date to erify the efciency of aligners alone in maintaining anchorage In aligner orthodontics, as well as in conentional ortho dontics, anchorage loss could result in inefcacy of pro grammed moements or in undesired moements of anchor age unit A paper y ortona et al reported the effects of anchorage loss on a contralateral premolar during rotation of a lower premolar without attachments Anchorage in aligner orthodontics depends on two ey factors sequentialization of moements and aligner defor mation Sequentialization in aligner orthodontics is intended as the order in which teeth are moed during the treatment oement sequentialization allows a proper anchorage control, reducing the ris of undesired displacements ul tiple moements at the same time should e aoided unless we are referring to small amounts of moement on seeral teeth, as in such cases when we are aligning and leeling the arches in mild class I malocclusions, for example ul tiple complex moements as well as lingual root torque moement associated with rotation and extrusion or intru sion moements of an upper incisor, as an example, should e always aoided In cases when multiple moements hae een planned on a specic tooth, the est option is to split moements ased on their complexity Therefore, torque moement should e performed a second time, at least once rotational and tipping moements hae een completed ore detailed sequentialization protocols will e analyzed in dedicated chapters Among sequentialization resides also the concept of “differential forces and moments” This concept is the result of the iomechanical design of a force system, which y the way of its application can distriute the reciprocal forces and moments oer signi cantly different root areas with the oectie of eliciting a
differential response Seeral studies demonstrated the efciency of this method in presering anchorage and ante rior torque during space closure after a premolar extrac tion, In aligner orthodontics, these concepts hae een introduced y Align Technology with the socalled pro tocol for rst premolar extraction ifferential moments are produced with a comination of optimized attachments and aligner actiation howeer, no detailed force systems are pulicly aailale and to date no trials hae een con ducted to measure the outcomes of this clinical protocol Aligner deformation is intended as the response of the whole aligner to the stress caused y tting it on teeth uring aligner wearing, a push and pull force system in oles not only the teeth for which moements are planned ut also adacent teeth and the aligner itself ig shows the tooth displacement during upper second molar distalization in an efcient force conguration note that while mm of moement was planned for tooth , mm is efciently applied on the tooth, while the other amount results in mesial displacement of the aligner An other example of anchorage loss due to aligner deforma tion is reported in ig , in which mesial displacement of molars is highlighted during sequential distalization of premolars irst and second molars, in this simulation, were set as an anchorage unit oweer, without proper auxiliaries to increase anchorage and manage aligner de formation, een a good moement sequentialization could e not adequate
OTM Saging In aligner orthodontics, staging is intended as the amount of programmed moement per tooth in each aligner Stag ing amount is determined y each aligner company ased on internal research, thus default staging settings may differ etween one another egarding scientic literature, ei denceased data aout staging are ery poor Simon et al, in their in itro study, tested different amounts of stag ing for premolar rotation The accuracy for this moement was haled when a rotation greater than degrees per aligner was planned , degrees 12 . degrees 12 The importance of staging for tooth rotation could e highlighted in the paper y ortona et al A simulation, including an ideal dental arch with element rotated degrees mesially, was tested with dif ferent staging and attachment congurations for premolar distal rotation Staging of and degrees of rotation per
4
Principles and Biomechanics of Aligner Treatment
Fig 2 nitial tooth displacement of second molar distaliation with class elastics applied on aligner at rst premolar level. nitial displacement amount is shown in the attached legend.
Fig 3 nitial tooth displacement of rst molar and second premolar distaliation without class elastics. The mesial shift of posterior teeth is clinically relevant.
aligner was compared and the difference in periodontal liga ment P pressure on tooth etween the different amount of staging with rectangular attachments from tooth to was reported Planned rotation of de grees produced mmg of pressure on periodontal liga ment, while degrees of planned rotation otained pressure of mmg Thus the model with attachments from to and degrees of actiation was the most reli ale and efcient conguration for lower premolar rotation idenceased data regarding staging for other moe ments may e deried from in itro and clinical studies, ut there is a lac of dedicated trials Tale reports the sug gested amount of moement per aligner ased on scientic literature and clinical expertise of the authors
Table 5.1 uggested Amount of ovement per Aligner Rotation
,.°
ntrusiontrusion
. mm
inear ovement
. mm
Root Torue
°
Biologic Considerations in Aligner Orthodontics As stated at the eginning of this chapter, personalized medicine applied to orthodontics is ased not only on dedi cated mechanics ut also on the nowledge of each pa tient’s iology The application of an orthodontic force produces a tissue reaction resulting from the perturation generated y the orthodontic appliance and the modeling and remodeling of the aleolar one uncio et al suggested that teeth moed with aligners did not undergo the typical stages of moement, as descried y rishnan and aidoitch, e cause of the intermittent forces applied y the aligners oweer, light, continuous forces seem to e perceied as intermittent forces y the periodontium due to its iscoelas tic nature, and orthodontic intermittent forces can produce T with less cell damage in the periodontium astro§o rio et al, in analyzing the iologic response to the applica tion of aligners distalizing a maxillary molar in a single tooth moement design study, showed that the force deli ery produces an increased concentration of one modeling
5 • Theoretical and Practical Considerations in Planning an Orthodontic Treatment with Clear Aligners
and remodeling mediators at oth pressure sites interleu in eta Ib, receptor actiator of nuclear factor appaB ligand A and tension sites transforming growth factor eta Tb, osteopontin P In other words, aligners seem to e capale of inducing the same iologic responses descried for other appliances at least in the ery early stages of orthodontic treatment
Patient Compliance espite all iologic and iomechanical aspects, the success of an orthodontic treatment strictly depends on patient compliance ompliance with remoale orthodontic align ers is fundamental for the efciency and success of AT in the short and long term A systematic reiew uilt on preious primary re search conrmed suoptimal leels of compliance with a ariety of remoale orthodontic aduncts, alluding to ac tual wear durations of hours per day less than recom mended The in§uence of treatment progress appeared to e signicant to motiate compliance, although it could e argued that facial and occlusal improement is most liely in more compliant patients anyway otwithstand ing this, demonstrale change was frequently reported as a facilitator of appliance wear As such, the importance of encouragement and positie reinforcement y clini cians and family memers in encouraging appliance wear is clear Pilot studies in the eld hae demonstrated that nown monitoring increases patient compliance, The use of an app was effectie in increasing patient compliance in a xedappliance population ustomized reminders may help to promote enhanced leels of compliance with align ers thans to teleorthodontics Teleorthodontics is a road term that encompasses remote proision of orthodontic care, adice, or treatment through the medium of informa tion technology Teleorthodontics platforms using articial intelligence to remotely monitor patient adherence to the prescried wearing time are aailale eg, ental onitor ing, Paris, rance and hae een demonstrated to e effec tie in enhancing patient compliance
CAT Fundamentals Recap onsidering all the premises, aligner orthodontics is a ma ture orthodontic technique requiring orthodontists to man age it properly Some limitations in the appliance system remain, ut they in no way suggest unsatisfactory treat ment results iagnosis and treatment plans still remain the responsiility of clinicians and cannot yet e oercome y articial intelligence It is clear that treatment progress is not as easy and predictale as dictated y computer animation Therefore, giing priority to technology instead of orthodontics is dangerous The nowledge of iomechanics is crucial to properly manage clear aligner therapy oreoer, lie any other orthodontic technique, auxiliaries are manda tory to perform an efcient and predictale orthodontic treatment
4
References Seymour B Polymers are eerywhere J Chem duc iegelstein Personomics the missing lin in the eolution from precision medicine to personalized medicine J ers ed doipm an , ia , heng , et al Saliary exosomes emerging roles in systemic disease nt J iol ci doi is de Aguiar , Perinetti , apelli r The gingial creicular §uid as a source of iomarers to enhance efciency of orthodontic and functional treatment of growing patients iomed es nt ashin , alci , Almuzian , et al arers in lood and salia for prediction of orthodontically induced in§ammatory root resorption a retrospectie case controlledstudy rog Orthod Proft , ields Contemporary Orthodontics th ed St ouis osy ossini , Parrini S, eregius A, et al ontrolling orthodontic tooth moement with clear aligners an updated systematic reiew regarding efcacy and efciency J ligner Orthod rünheid T, oh , arson B ow accurate is Inisalign in nonex traction cases? Are predicted tooth positions achieed? ngle Orthod Burstone harles Burstone, S Part iomechanics Interiew y r anda J Clin Orthod Simon , eilig , Schwarze , et al Treatment outcome and efcacy of an aligner technique—regarding incisor torque, premolar derota tion and molar distalization C Oral ealth doi Simon , eilig , Schwarze , et al orces and moments generated y remoale thermoplastic aligners incisor torque, premolar dero tation, and molar distalization m J Orthod entoacial Orthop Barone S, Paoli A, azionale A, et al omputational design and engineering of polymeric orthodontic aligners nt J Numer ethod iomed ng e ennessy , arey T, AlAwadhi A A randomized clinical trial comparing mandiular incisor proclination produced y xed laial appliances and clear aligners ngle Orthod ayes , Sarer , acoson A The quantication of soft tissue cericomental changes after mandiular adancement surgery m J Orthod entoacial Orthop Sarer , Acerman rthodontics aout face the reemergence of the esthetic paradigm m J Orthod entoacial Orthop loresir , Sila , Barriga I, et al ay person’s perception of smile aesthetics in dental and facial iews J Orthod Parrini S, ossini , astro§orio T, et al aypeople’s perceptions of frontal smile esthetics a systematic reiew m J Orthod entoacial Orthop camara r A, Brudon Orthodontic and Orthopedic Treatment in the ied entition Ann Aror eedham Press auddin S, g P, Biswas S, et al Iatrogenic damage to the peri odontium caused y orthodontic treatment procedures an oeriew Open ent J ati AS, urquim , onsolaro A ingial recession its causes and types, and the importance of orthodontic treatment ental ress J Orthod aera S, astro§orio T, arino , et al axillary molar distalization with aligners in adult patients a multicenter retrospectie study rog Orthod dois arino , astro§orio T, aher S, et al ffectieness of composite attachments in controlling uppermolar moement with aligners J Clin Orthod asy , asy A, Asatrian , et al ffects of ariale attachment shapes and aligner material on aligner retention ngle Orthod doi antoani , astro§orio , ossini , et al Scanning electron microscopy ealuation of aligner t on teeth ngle Orthod doi antoani , astro§orio , ossini , et al Scanning electron micros copy analysis of aligner tting on anchorage attachments J Oroac Orthop dois
Principles and Biomechanics of Aligner Treatment
ooi , Arai A, awamura , et al ffects of attachment of plastic aligner in closing of diastema of maxillary dentition y nite element method J ealthc ng omez P, Peña , artínez , et al Initial force systems during odily tooth moement with plastic aligners and composite attach ments a threedimensional nite element analysis ngle Orthod Breznia The clear plastic appliance a iomechanical point of iew ngle Orthod astro§orio T, arino , azzaro A, et al pperincisor root control with Inisalign appliances J Clin Orthod rünheid T, aalaas S, amdan , et al ffect of clear aligner ther apy on the uccolingual inclination of mandiular canines and the intercanine distance ngle Orthod Ballard Asymmetry in tooth size, a factor in the etiology, diagnosis, and treatment of malocclusion ngle Orthod oretsi , hatzigianni A, Sidiropoulou S namel roughness and in cidence of caries after interproximal enamel reduction a systematic reiew Orthod Cranioac es achrisson B, yøygaard , oarac ental health assessed more than years after interproximal enamel reduction of man diular anterior teeth m J Orthod entoacial Orthop Sarig , ardimon A, Sussan , et al Pattern of maxillary and mandiular proximal enamel thicness at the contact area of the permanent dentition from rst molar to rst molar m J Orthod entoacial Orthop ortona A, ossini , Parrini S, et al lear aligner orthodontic ther apy of rotated mandiular conical teeth a nite element study ngle Orthod Sumitted for pulication minor reision anda r aindra anda on orthodontic mechanics Interiew y oert eim J Clin Orthod uhlerg A, Priee Testing force systems and iomechanics— measured tooth moements from differential moment closing loops ngle Orthod aoody A, Posada , trea A, et al A prospectie comparatie study etween differential moments and miniscrews in anchorage control ur J Orthod
ie P Treating imaxillary protrusion and crowding with the inisalign rst premolar extraction solution and inisalign aligners O Trends Orthod iu , u orce changes associated with different intrusion strategies for deepite correction y clear aligners ngle Orthod rishnan , aidoitch iological echanisms o Tooth ovement nd ed ooen, ileyBlacwell uncio , aganzini A, Shelton , et al Inisalign and traditional orthodontic treatment postretention outcomes compared using the American Board of rthodontics oectie grading system ngle Orthod attaneo P, alstra , elsen B Strains in periodontal ligament and aleolar one associated with orthodontic tooth moement analyzed y nite element rthod raniofac es astro§orio T, amerro , aiglia P, et al Biochemical marers of one metaolism during early orthodontic tooth moement with aligners ngle Orthod Aloghrai , Salazar , Pandis , et al ompliance with remo ale orthodontic appliances and aduncts a systematic reiew and metaanalysis m J Orthod entoacial Orthop luni A, olonio Salazar B, Sharma P, et al nderstanding factors in§uencing compliance with remoale functional appli ances a qualitatie study m J Orthod entoacial Orthop Pauls A, ienemper , Panayotidis A, et al ffects of wear time recording on the patient’s compliance ngle Orthod Arreghini A, Trigila S, omardo , et al ectie assessment of compliance with intra and extraoral remoale appliances ngle Orthod i , u , Tang , et al ffect of interention using a messaging app on compliance and duration of treatment in orthodontic patients Clin Oral nvestig ansa I, Semaan S, aid , et al emote monitoring and “tele orthodontics” concept, scope and applications emin Orthod
6
Class I Malocclusion MARIO GRECO
Introduction Class I malocclusions represent one of the most common conditions in the daily clinical practice and one of the most elective conditions to be treated with aligners, since the primary patients’ concern is often represented by crowded anterior teeth, especially in the mandibular arch.1 Working with clear aligners challenges the paradigm on which we, as orthodontists, based the traditional ed me chanics approach. Working with aligners means that we need to plan everything in advance and not on a monthly basis, dening nal teeth position from the beginning and spending more time in treatment plan design and staging than at the chairside.
Diagnostic Reference When dealing with class I malocclusion, the rst step to con sider is the denition of the biologic limits of the arches. We should identify anterior, frontal, and vertical limits. ll the limits represent both a morphologic limit torue posterior and anterior strictly connected to bone and teeth pattern of movement and an esthetic indication to dene eactly the ideal teeth positioning in relationship to lips and face. ore specically, during treatment plan in class I maloc clusion a very schematic approach could be focused on the observation and respect of the following key points n
n
sthetic key points face midline, smile arc, intraarch symmetry cclusal key points olton analysis, overet, incisors inclination
ubstantially the esthetic indicators represent the limits in which teeth need to be moved on the horiontal plane arch symmetry, face midline and on the vertical plane smile arc the occlusal indicators are useful to dene the proper veret needed to ensure anterior clearance and avoiding premature anterior contacts causing posterior open bite in relation ship to dental sie and anterior limit of dentition.
Treatment Plan he development of proper treatment plan in class I maloc clusion starts from the denition of correct staging of movement to create a reliable digital setup and to reach a predictable result with high superimposition between the real and the digital settings. he ideal approach in terms of treatment staging should be based on curve of pee level ing, incisor control, arch development, rotation control, attachment choice, and interproimal reduction I.
CURVE OF SPEE LEVELING o avoid anterior premature contacts, to create the proper cuspids and molars intercuspations, and to allow lower incisor leveling and correct anterior relationship related to guidance function, attening of the curve of pee is reuired. oreover, the assessment of the amount of lev eling will give information about the space needed for curve attening.
INCISOR CONTROL aving in mind the precise angular inclination of lower incisors according to the cephalometric references and us ing the superimposition tool andor the movement table tool, together with the grid tool of digital setup software, is possible to determine the amount of proclination or retro clination reuired to properly locate the lower incisors on the sagittal plane.
ARCH DEVELOPMENT In terms of treatment approach, epansion represents a very common solution to treat crowding and transverse discrepancy. uccal tipping movement is more predictable than bodily movement when planning arch epansion with aligners. his should be kept in mind when dening the buccolingual inclination of canine premolars and molars respecting the periodontal condition.
ROTATION CONTROL otation of small teeth or round teeth such as premolars could be considered a difcult movement to achieve be cause of the reduced tooth surface on which the force can be applied. Comple rotations should be managed by rst creating the mesial and distal spaces reuired to rotate teeth and then choosing the proper attachment.
ATTACHMENT CHOICE ttachments represent a useful tool to increase the surface on which orthodontic forces could be applied ig. .1. ee previous chapters for more details.
INTERPROXIMAL REDUCTION ne common procedure in aligner techniue is represented by the I, which ideally should be limited to . mm per in terproimal point to avoid too wide enamel reduction. he management of I is fundamental not only for ing crowd ing problems and nding more space but also to control the 51
52
Principles and Biomechanics of Aligner Treatment
A
B Fig. 6.1 Biomechanical design of conventional attachments for extrusion (A) and distal rotation (B)
incisor inclination i.e., creating space with I could rep resent a reliable system to upright upper or lower incisors, to compensate olton discrepancy by reducing teeth ecess, and to create symmetric dimension between left and right sides.1
I could represent a reliable solution to recreate ideal alignment, but some options during the digital setup plan ning need to be controlled to avoid collateral effects, as follows n
Class I Conditions Class I malocclusions can be divided into different catego ries following the principal condition that affects speci cally one or more dimensions of the space transverse or vertical or which creates a determinate discrepancy. or this reason they will be discussed separately.
n
n
DENTOALVEOLAR DISCREPANCY he most common condition is represented by crowding in the upper or lower arch or both. he clear aligner treatment C of crowding is highly predictable when approached with the proper staging such as epansion, small proclina tion, reduced I, and torue correction. ormally, being able to avoid etractions means that treatment options available are related to epansion mm per uadrant and I . mm maimum per interproimal space. he se verity of crowding, particularly in the lower aw, signi cantly affects the possibility of avoiding etraction treat ment. Conditions in which it is reasonable to treat without etraction are as follows n
n
n
n
n
void ecessive proclination of lower incisors by means of using the superimposition tool and the grid tool of the software and by favoring transverse epansion and con seuently a more uprighted position of lower incisors ig. .. lace the lower premolars to a buccal crown torue net to ero to recreate space without changing the interca nine width when on the occlusal picture of lower aw, it is possible to observe the labial surface of premolars, torue correction could be achieved ig. .. Combine class III elastics to create the proper 1. mm and to favor the correction of crowding also in absence of real class III relationship ig. .. Create upper and lower aw ideal shape to avoid black triangles and buccal facial corridors ig. .. lan specic attachments see Chapter ig. ..
ight crowding, with normal amount of I .1 . mm ild to moderate crowding, with combination of epan sion without changing intercanine width and maimum rate of . mm of I per interproimal space oderately severe crowding, combining the .mm I per interproimal space with torue correction of lower premolars to create a positive torue up to a maimum of degrees of buccal torue inclination
his means that when the crowding is lower than mm per uadrant, the possibility to combine epansion and
Fig. 6.2 ClinCheck tools to check incisor inclination.
6 • Class I Malocclusion
A
B
C
D
53
E Fig. 6.3 Pretreatment records oung adult patient ith severe croding and negative premolar torue. (A intraoral pictures)
TOOTH SIZE DISCREPANCY he olton analysis is important because it allows the im mediate visualiation of the interarch and intraarch dis crepancies. hese discrepancies can affect the nal overet. ot considering the olton analysis in our treatment plans could lead to several unfavorable outcomes anterior prema ture contacts with posterior open bite without reaching a proper class I intercuspation on both sides, ecessive procli nation of incisors, and uncorrected closure of upper diaste mas. herefore, the tooth sie discrepancy analysis is crucial when designing orthodontic treatment. thman and arra dine recommended a threshold of mm discrepancy to be
of clinical signicance for restorative intervention igs. . and ..111 nother common condition of tooth sie discrepancy is represented by dental anomalies in number bilateral or monolateral agenesis and dental anomalies in shape mi crodontia, pegshaped lateral incisors. In the case of a monolateral agenesis in the anterior area missing upper lateral incisor, the olton analysis can provide the precise dimension of the contralateral incisor helping the clinician in dening the right space that needs to be preserved for the nal restoration. In case of pegshaped contralateral incisor the olton analysis provides information regarding the
54
Principles and Biomechanics of Aligner Treatment
A
B
C
D
E Fig. 6.4 Posttreatment records oung adult patient ith severe croding and negative premolar torue treated ith torue correction and interproximal reduction. (A intraoral pictures)
A
B
Fig. 6.5 (A) Pretreatment records oung adult patient ith narro up per arch and smile lack corridors. (B) Posttreatment records oung adult patient ith narro upper arch and smile lack corridors treated ith upper expansion and loer torue correction.
Fig. 6.6 oule conventional attachment in case of severe rotation.
6 • Class I Malocclusion
A
B
C
D
Fig. 6. Pretreatment records tooth sie discrepanc A intraoral pictures.
A
B
C
D
E
Fig. 6. Posttreatment records toothsie discrepanc treated space opening and interproximal reduction A igital proect B intraoral pictures.
55
56
Principles and Biomechanics of Aligner Treatment
golden proportion between the anterior si teeth helping the clinician in determining the right space to be preserved for the nal restorations. In the case of bilateral agenesis in which the treatment is designed to close the space of later als with mesial movement of canines, premolars, and mo lars, the tooth sie discrepancy values are fundamental to reduce the dimension of canines that will become laterals and to increase the dimension of premolars that will be come canines.11
TRANSVERSE DISCREPANCY ne of the most duple conditions to be treated with aligners is represented by the transverse discrepancy the term duplex refers to the different compleity in the treat ment of anterior crossbite and posterior crossbite, since anterior crossbite represents an elective condition to be treated with aligners while the posterior relies its possibil ity to be successful on the severity of posterior crossbite and on the use of supporting auiliary devices cross elastics ig. .. he anterior crossbite central, lateral, or canine in bilat eral or monolateral conguration is a perfect condition to be approached with Invisalign aligners since the thickness of the aligner itself avoids any need of bite turbos to create disclu sion, a condition needed during traditional ed orthodontics. or this reason, the treatment of one single element of anterior crossbite could be predictably ed with a lite lite is the com mercial name of Invisalign with reduced number of aligners. or this reason is not light but lite. reatment if the rest of
Fig. 6.1 Anterior contact during uccal movement for crossite resolution.
malocclusion conditions permits this simplied approach. he following should be done to increase predictable results n
n
n
uring treatment the buccal movement of laterals or centrals will create an edgetoedge contact to overcome this traumatic contact, it may be convenient to change aligners more rapidly to reduce the time eposed to trauma ig. .1. ogether with labial movement to the crossbite, some millimeters of etrusion should be planned to create normal overbite. enerally, in case of anterior crossbite, the ape of the element is located more buccal compared to the crown for this reason, unparticular root movement is reuired igs. .11 and .1.
he correction of posterior crossbite represents a vari able, predictable correction with aligners according to the severity of the crossbite one single element crossbite could be easily managed only by the system, while for the correc tion of severe maillary contraction with multiple elements in crossbite the use of auiliaries is widely suggested. In particular, these indications should be followed to create a reliable correction n
A
n
n
n
n
B n
Fig. 6. Cross (AB intraoral pictures) elastics to support posterior expansion.
In case of single element crossbite, more crown torue should be planned instead of buccal epansion. In case of multielement crossbite, buttons for crisscross elastics should be planned to help the correction and sup port the elastic modication of the aligners by using di rect bonding on the teeth and cooperation with 1 hours of elastics o, mm. o simplify the correction, some minimal I in the in terproimal spaces could be helpful only to remove pos sible initial interferences while starting the epansion. he use of bite ramps even in the absence of deep bite is strongly suggested. It could simplify the posterior move ment creating disclusion, favoring the buccal movement and the vertical etrusion moment in combination with crisscross elastics igs. .1 and .1. ccording to the malocclusion, further elastics for sagit tal control should be planned class II or III ig. .1. In case of severe maillary contraction, a crown torue inclination assessment should be done to understand the amount of possible correction only with dental epansion.
6 • Class I Malocclusion
A
B
C
D Fig. 6.11 Pretreatment records of lateral incisor in anterior crossite. A intraoral pictures
A
B
C
D Fig. 6.12 Posttreatment records ith complete correction of crossite in reduced numer of aligners. AB intraoral pictures
5
5
Principles and Biomechanics of Aligner Treatment
A
B
C
D
E Fig. 6.13 Pretreatment records of severe posterior crossite ith maxillar contraction. A intraoral pictures
he predictable plan for posterior crossbite is basically focused on epansion up to . mm per uadrant. If the crown torue of lateral elements and the periodontal condi tion could allow this kind of correction, the combined use of bite ramps and crisscross elastics could predictably in crease the outcome achievement.
MORPHOLOGIC DISCREPANCY ess common conditions of class I malocclusions are repre sented by those situations of teeth with morphologic anom alies, such as single or multiple anterior agenesis and microdontia conoid laterals, that affect the orthodontic
treatment and ideal outcome according to the therapeutic choice. ll morphologic discrepancies are strictly connected to olton discrepancy, and for this reason the same approach described later should be followed to achieve proper occlu sal outcome and normal overet. oreover, an important consideration should be done on the microesthetics and macroesthetics when teeth show a different shape. In the case of monolateral dental morphologic anomaly conoid or agenesis, it becomes necessary to leave the proper space to concentrate on the opposite normal shape element dimension. he olton button could provide infor mation about teeth sie, and on the ClinCheck it is possible
6 • Class I Malocclusion
A
B
C
D
E
F Fig. 6.14 Posttreatment records after expansion 1 torue correction 1 interproximal reduction 1 ite ramps. A intraoral pictures igital setup shoing ite ramps for posterior disocclusion.
A
B Fig. 6.15 Class III elastics. A intraoral pictures B igital etup
5
6
Principles and Biomechanics of Aligner Treatment
to plan space opening mesial and distal to the conoid ele ment to organie the nal restoration ig. .1. In case of single agenesis, one further assessment should be done con cerning the space between the roots. ince the nal restora tion will be an implant, it is fundamental to measure the space between the apees to realie if the outcome could be achieved only with aligners or some auiliaries will be needed. When the apical distance is around mm, no other special auiliaries will be needed, ust the space opening between crowns, while when the distance is less than mm, some auiliaries lingual sectional or power arm could be necessary to achieve the proper space for implant insertion igs. .1 and .1. In the case of agenesis of both lateral incisors, the choice of space closure with total mesial movement of posterior teeth or space opening for implant insertion has long been discussed in the literature.11 ctually, in case of young patients, the ideal solution seems to be the space closure with reshaping of the canines both additive and subtrac tive enamel plastic to simulate laterals combined with re shaping of rst premolars simulating canines additive enamel plastic. he advantages of approaching with
aligners are the possibility to have all the information about sie of the teeth olton tool, balancing I on ca nines and space opening on rst premolars to create ideal anterior relationship between the si anterior teeth com bined with leveling the anterior gingival margins to create a harmonic smile igs. .1 and ..
PREPROSTHETIC NEED he last common condition analyed of class I malocclu sion is strongly related to those situations in which the orthodontic treatment could be helpful in creating more favorable conditions for prosthetic solution, thus gaining space where it was missing for nal restoration. eing very schematic, two conditions in adult patients with missing teeth commonly reuire the orthodontic support to achieve an ideal prosthetic solution, namely 1. ipping in the edentulous space . vereruption in the edentulous space he mesial tipping of molars, in particular the tipping of second molars because of missing rst molar, represents a
1.0 1.0
A
B
C Fig. 6.16 pace opening for Peg shaped restoration. A pretreatment B digital plan C post treatment
6 • Class I Malocclusion
A
B
C
D
61
E Fig. 6.1 Pretreatment records of lateral incisor agenesis ith apical distance less than mm. A intraoral pictures panoramic xra
freuent condition sometimes combined with distal tipping of premolars.11 pproaching this problem with the align ers is highly predictable because of the following n
n
he force to upright the second molar creates a reaction force, which upright the premolars and this reciprocal force work properly together in opening the space ig. .1. he amount of space can be decided in advance on the software according to the dimension of the contralateral element.
n
n
o be more efcient, it is possible to ask to avoid pontics in the edentulous area to leave the aligner to embrace more surfaces of the molar to upright delivering more homogeneous force. In the ClinCheck plan it is fundamental to combine distal inclination of crown with distal movement to put the center of rotation net to the ape.
or the same reason when one or more teeth are missing, the problem could happen in another dimension of the
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Principles and Biomechanics of Aligner Treatment
A
B
C
D
E Fig. 6.1 Posttreatment records of monolateral lateral incisor agenesis ith Invisalign and xed sectional for root control. A intraoral pictures
space affecting the vertical movement overeruption of molars. pproaching this problem with traditional orthodontics means that an auiliary device for skeletal anchorage in the bone will be strongly needed. he traditional biomechanics to intrude molars are highly comple for anchorage lack.11 he opportunity to solve the overeruption with aligners simplies the treatment because the vertical force
of intrusion is applied to the teeth by means of labial, lin gual, occlusal, and distal surface not only on side, and it generates a reaction force that tends to etrude the ada cent tooth blocked by the occlusion and the thickness of aligners. his biomechanical system is more in balance when compared to traditional, and if no other movements in different planes are reuired, it can be accomplished in reduced number of aligners igs. . and ..
6 • Class I Malocclusion
A
B
C
D Fig. 6.1 Pretreatment records of ilateral lateral incisors agenesis. A intraoral pictures
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B
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D Fig. 6.2 Posttreatment records of ilateral lateral incisors agenesis treated space closure and teeth reshaping. A intraoral pictures
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Principles and Biomechanics of Aligner Treatment
A
B
Fig. 6.21 pace opening distal tipping of molars. A pretreatment intraoral picture B posttreatment intraoral picture ith implant inserted
A
B
C Fig. 6.22 Pretreatment records of overerupted upper second molar. AB intraoral pictures C panoramic xra
A
B
C Fig. 6.23 Posttreatment records of overerupted upper second molar treated aligners onl. AB intraoral picture C panoramic xra
6 • Class I Malocclusion
References 1. ossini , arrini , Castroorio , et al. fcacy of clear aligners in controlling orthodontic tooth movement a systematic review. Angle Orthod. 11. . achdeva . Integrating digital and robot technologies diagnosis, treatment planning, and therapeutics. In raber , anarsdall , ig, W, eds. Orthodontics Current Principles and Techniques. th ed. lsevier 11. . chol , achdeva C. Interview with an innovator uremile chief clinical ofcer ohit C. . achdeva. Am J Orthod Dentofacial Orthop. 111. . imon , eilig , chware , et al. reatment outcome and efcacy of an aligner techniue—regarding incisor torue, premolar derotation and molar distaliation. BMC Oral Health. 11. . eli I, turk , ysal . Curve of pee and its relationship to vertical eruption of teeth among different malocclusion groups. Am J Orthod Dentofacial Orthop. 111. . epedino , ranchi , abbro , et al. ostorthodontic lower incisor inclination and gingival recession—a systematic review. Prog Orthod. 1111. . apadimitriou , ousoulea , kantidis , et al. Clinical effective ness of Invisalign® orthodontic treatment a systematic review. Prog Orthod. 111. . imon , eilig , chware , et al. orces and moments generated by removable thermoplastic aligners incisor torue, premolar derotation, and molar distaliation. Am J Orthod Dentofacial Orthop. 11 . . ravit , usnoto , gran , et al. Inuence of attachments and interproimal reduction on the accuracy of canine rotation with Invisalign. prospective clinical study. Angle Orthod. .
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1. eredith , arella , owrey , et al. tomic force microscopy anal ysis of enamel nanotopography after interproimal reduction. Am J Orthod Dentofacial Orthop. 111. 11. thman , arradine W. oothsie discrepancy and olton’s ratios the reproducibility and speed of two methods of measurement. J Orthod. . 1. Cançado , onçalves únior W, alarelli , et al. ssociation between olton discrepancy and angle malocclusions. Braz Oral es. 11. 1. osa , achrisson . Integrating space closure and esthetic dentistry in patients with missing maillary lateral incisors. J Clin Orthod. 1. 1. osa , ucchi , errari , et al. Congenitally missing maillary lat eral incisors longterm periodontal and functional evaluation after orthodontic space closure with rst premolar intrusion and canine etrusion. Am J Orthod Dentofacial Orthop. 11. 1. amilian , erillo , osa . issing upper incisors a retrospective study of orthodontic space closure versus implant. Prog Orthod. 11. 1. iancotti , arina . reatment of collapsed arches using the Invisalign system. J Clin Orthod. 11. 1. ampieri , iancotti . Invisalign techniue in the treatment of adults with prerestorative concerns. Prog Orthod. 11. 1. rslan , demir , ursoyert , et al. Intrusion of an over erupted mandibular molar using miniscrews and miniimplants a case report. Aust Dent J. 11. 1. ripathi , alra , ai , et al. rue intrusion of maillary rst mo lars with ygomatic and palatal miniscrew anchorage a case report. Aust Orthod J. 1.
7
Aligner Treatment in Class II Malocclusion Patients TOMMASO CASTROFLORIO, WADDAH SABOUNI, SERENA RAVERA, and FRANCESCO GARINO
Introduction Since the introduction of clear aligner treatment (CAT), controversy has existed over whether moderate to difcult orthodontic treatment can be routinely accomplished with aligner techniue hen dealing with class malocclu sions, CAT offers different possible therapeutic options
istaliation olar derotation lastic ump xtractions andibular advancement rthognathic surgery
MAXILLARY MOLAR DISTALIZATION n some nonextraction cases, maxillary molar distaliation is the method of choice to gain to mm of space in the dental arch to obtain a class relationship in both teens and adults The upper molars can be distalied by means of extraoral or intraoral forces xtraoral traction with headgear has a long history of use in class treatment since it has been designed to push distally the maxilla and the maxillary mo lars, n recent years, several techniues have been devel oped to reduce the dependence on patient compliance, such as intraoral appliances with and without seletal anchor age owever, even these devices can produce undesirable tipping of the maxillary molars andor loss of anterior an chorage during distaliation, To achieve a tooth bodily movement implies that the applied force must pass through the center of resistance of the tooth or a sophisticated euivalent system of forces and moments needs to be ap plied to the tooth crown A recent review of the existing literature assessed the efcacy of aligners in aligning and straightening the arches, with better results for mild to moderate crowding when compared to the results obtained with xed appliances ore recently, it was stated that the overall available evidence regarding orthodontic tooth movement (T) control during CAT increased signi cantly, with three randomied controlled trials (CTs) at grade A and an overall uality of evidence of moderate high level, and that maxillary molar distaliation of mm and premolar extraction space closure ( mm) are the most predictable and controlled movements with CAT n , Simon et al stated that maxillary molar dis taliation was the most predictable movement () to
66
perform with CAT The authors started to focus on the ey role of a correct staging of the planned movement and of the adoption of proper attachments during the whole dis taliation phase Thus a highly signicant element of bias in the study by rae et al was the staging of mm per aligner instead of the mm recommended n , avera et al conrmed the results of Simon et al and demonstrated that distaliation is efciently achievable up to mm on the rst and second maxillary molars, with optimal vertical control of posterior teeth and any loss of anchorage on the anterior teeth These results were obtained through the combination of staging, vertical rectangular attachments, and class elastics (– o) for anchorage reinforcement The use of attachments and elastics was previously described by expert clinicians The application of composite attachments could be useful to improve the biomechanic efciency of aligner therapy ong vertical attachments located on the buccal aspect of the molars can create a sufcient moment to oppose the tipping movement Thus long vertical attachments can provide good tipping control while molars are moving and then can increase posterior anchorage while retracting anterior teeth The need for a determined attachment combination was conrmed in a CT by arino et al, who ob served signicant differences in the amount of distalia tion when comparing a veattachment conguration (second and rst molars, second and rst premolars, and canine) with a threeattachment conguration (rst mo lar, second and rst premolars), with the rst ones being most efcient Controlling the tipping movement during molar distaliation can be difcult because of the limited alignertooth surface in the direction of force application The absence of long rectangular attachments on the sec ond molar resulted in a probable loss of anchorage during the distaliation of the rst molar, with conseuent re duced amount of distal movement of the second molar at the end of the treatment and signicant tipping of the rst molar urthermore, the absence of a proper anchorage preparation in the distal portion reduced the possibility of an adeuate control of the retracting anterior teeth As a result, the central incisors showed an uncontrolled tip ping movement in the group with a threeattachment conguration ecently ome et al demonstrated that when the aligner segment was displaced distally without attach ments, a clocwise moment and distal inclination were
7 • Aligner Treatment in Class II Malocclusion Patients
produced on the upper canine The presence of composite attachments helped counteract this inclination, producing a countermoment that in turn favored a bodily movement n another nite element analysis study, Comba et al demonstrated that the use of attachments on tooth surface counteracts the uncontrolled tipping during distaliation through the generation of a countermoment that ends in the root uprighting This moment is dependent from a com plex force system and is generated by the active surfaces of attachments hen analying a couple of attachments located on the buccal surface of an upper canine, one located at the distocervical portion and the other located at the mesioincisal portion, compression areas were found on the mesial face of the cervical attachments and on the distal face of the incisal attachment These outcomes validate ome ndings The vertical pattern is an important point to consider while planning molar distaliation The distal movement measured in our study was associated with signicant in trusion movements of the molars The thicness of the aligners and the conseuent occlusal force exerted on them might facilitate intrusion and explain the absence of any change of anterior vertical dimension while distaliing urthermore, ome et al reported a mared tendency of “aring” of the buccal and palatal ans of the aligner seg ment during distal displacement This nding is interesting because it could suggest an intrusive effect on the tooth The aligner therapy is a customied orthodontic treat ment for both the patient and the orthodontist The pres ence of composite attachments for the control of the maxillary molars during the distaliation process is a choice of the prescribing clinician for most of the avail able systems in the maret
67
The effect of elastics is simulated as a onestage antero posterior movement at the end of treatment, which enables verication of the nal arch coordination and occlusion ewer aligners are reuired when simultaneous stag ing is used along with use of elastics as compared with distaliation owever, a preparation phase in which all the possible interarch interferences are removed is re uired in the virtual setup planning to create enough room in which the class elastics can promote their effects espite the large use of class elastics in everyday prac tice, little evidence is nown about their effects A recent systematic review stated that the current literature sug gests using light forces (average, o) obtained with a in diameter elastic and a rectangular to in stainless steel archwire n aligner orthodon tics, the use of in diameter o was recom mended, on the basis of expert clinician experience owever, as shown in Chapter , nite element analysis has shown the need for stronger class elastics in CAT ecause class elastics heavily rely on patient compliance, fulltime usage is recommended t has been described as an average period of months for the correction of the class discrepancy with elastics only, and the correction is usually obtained with predominant dentoalveolar effects This is the average treatment time reuired to correct an endtoend class malocclusion according to existing lit erature
EXTRACTIONS lease refer to Chapter for specics on extractions
MANDIBULAR ADVANCEMENT MAXILLARY MOLAR ROTATION esiopalatal rotation of the upper rst molar is present in about of patients with angle class , division maloc clusion and in of them as a whole esiopalatal rotation of upper rst molars often ends up in an intraarch loss of space reuently, this crowding occurs in the pre molar and canine segments, thus potentially preventing the correct mesiodistal position of these teeth n this basis, buccodistal rotation of maxillary molars can be considered a useful procedure to partially improve class dental rela tionship olar rotation was indicated as one of the predict able movements controlled by aligners
lease refer to Chapter for specifics on mandibular advancement
ORTHOGNATHIC SURGERY rthognathic surgery consists of surgical procedures performed on the maxilla andor the mandible to correct serious basal malocclusions and to harmonie the prole t is benecial in adults since the most difcult cases cannot be treated by orthopedic and orthodontic therapy alone lease refer to Chapter for specics on orthognathic surgery
THE ELASTIC EFFECT The elastic effect can be dened as class correction using interarch mechanics t is simulated on virtual setups by a umplie shift of the occlusion from class to class to al low easier visualiation of the anticipated treatment goal ndividual tooth movements reuired to align teeth are set up to proect the effect of this bite correction using buttons and elastics lastic wear is recommended from the start of treatment, continuing until the desired anteroposterior correction has been achieved
The Clinical Protocol istaliation is performed to correct average to moderate class malocclusions (, mm) by retracting the maxillary teeth istaliation should be preferred in patients present ing a class malocclusion due to maxillary protrusion or in adult patients undergoing compromise treatment uring distaliation, it is essential to use class elastics or miniscrews to avoid loss of anchorage at the anterior teeth,,
68
Principles and Biomechanics of Aligner Treatment
epending on the severity of the sagittal malocclusion, we can use different clinical approaches n
n
n
or dental sagittal discrepancies where less than mm of distaliation are needed, we can safely perform aligner driven seuential distaliation or dental discrepancies ranging between and mm, depending on the clinical situation, we perform seuen tial distaliation combined, or not, with stripping, molar derotation, or an elastic effect f dental discrepancy exceeds mm, we opt for either extrac tion treatment or orthognathic surgery, once again depend ing on the clinical situation and the patient’s decision
Maxillary Distalization Case Reports CASE SUMMARY 1 A yearold female patient ased for an aesthetic orth odontic treatment easy to manage considering her ob as a maeup artist traveling across urope
She presented a class , division relationship, mild crowding in the lower arch, and moderate crowding in the upper arch The overet was increased to mm The prole analysis revealed protruded lip position (ig ) Considering the aesthetics reuest of the patient and her refuse for surgical interventions or extractions, the treatment plan was designed to obtain a nal molar and canine class relationship through a seuential dis taliation of the maxillary teeth using nvisalign (Align Technology nc, San osé, CA, SA) aligners, composite attachments on all the distaliing teeth, and class elastics (ig ) The patient was instructed to wear the aligners and the class elastics for at least hours per day urthermore, she used the Acceleent device for minutes every day of the orthodontic treatment Aligners were changed ev ery wees until the maxillary second molars were fully distalied, then every days until the rst molars were in their nal position, and then every days until the end of treatment The ClinChec (Align Technology nc, San osé, CA, SA) software revealed the need for aligners to obtain the prescribed results (distaliation planned for
Fig. 7.1 Case 1 initial clinical and radiographic records.
7 • Aligner Treatment in Class II Malocclusion Patients
69
Fig. 7.1, ’
mm) with the prescribed seuence of stages, attach ments, and class elastics Thus the estimated treatment time was approximately months The patient chose to use Acceleent, and the case was closed in months of treatment without further aligner with respect to the prescribed (ig ) The clinical results were excellent and revealed nal molar and canine class relationships with functional overbite and overet The prole of the lower third of the
face was highly improved with respect to the beginning (ig ) The superimposition of the cephalometric tracings re vealed a maxillary molar distaliation of about mm without signicant tipping and an excellent control of the buccolingual inclination of the incisors (ig ) The class elastics were responsible for a mandibular protraction of about mm etention was provided by ivera (Align Technology nc, San osé, CA, SA) retainers
7
Principles and Biomechanics of Aligner Treatment
Fig. 7. Case 1 frontal and sagittal views of initial ClinCheck.
Fig. 7. Case 1 nal clinical and radiographic records.
7 • Aligner Treatment in Class II Malocclusion Patients
Fig. 7., ’
71
7
Principles and Biomechanics of Aligner Treatment
Fig. 7. Case 1 frontal and sagittal views of nal ClinCheck.
Fig. 7. Case 1 lateral ra comparison and cephalometric maillar superimposition efore and after therap.
CASE SUMMARY A yearold female patient ased for an aesthetic orth odontic treatment easy to manage She presented a class , division relationship, moderate crowding in the upper arch, and mild crowding in the lower arch The overet was increased to mm The prole analy sis revealed an acceptable lip position (ig ) Considering the aesthetics reuest of the patient and her refuse for orthognathic surgery, the treatment plan was designed to obtain a nal molar and canine class relation ship by a seuential distaliation of the maxillary teeth using nvisalign (Align Technology nc, San osé, CA, SA) aligners, composite attachments on all the distaliing teeth, and class elastics The average distaliation movement prescribed was mm (ig )
The patient was instructed to wear the aligners and the class elastics for at least hours per day Aligners were changed every wees until the maxillary second molars were fully distalied, then every days until the rst molars were in their nal position, and then every days until the end of treatment The ClinChec (Align Technology nc, San osé, CA, SA) software revealed the need for aligners to obtain the prescribed results with the prescribed seuence of stages, attachments, and class elastics The estimated treatment time was approximately months n an intermediate phase, rst outcomes of seuential distaliation were clearly visible As shown in igs and , molars already distalied in a correct class relation ship were spaced apart from premolars
7 • Aligner Treatment in Class II Malocclusion Patients
The clinical results were excellent and revealed nal molar and canine class relationships with correct overbite and overet The prole of the lower third of the face was slightly improved with respect to the beginning, since the aesthetic analysis and cephalometric measurements showed acceptable values at the beginning of the treatment already (igs and )
7
The superimposition of the cephalometric tracings revealed a maxillary molar distaliation of about mm without significant tipping and an excellent control of the buccolingual inclination of the incisors (ig )
Fig. 7.6 Case initial clinical and radiographic records. Continued
7
Principles and Biomechanics of Aligner Treatment
Fig. 7.6, ’
Fig. 7.7 Case frontal and sagittal views of initial ClinCheck.
7 • Aligner Treatment in Class II Malocclusion Patients
Fig. 7.8 Case upper occlusal views at the eginning after molar distaliation and at the end of therap.
Fig. 7.9 Case end of distaliation intraoral frontal occlusal and sagittal views.
7
76
Principles and Biomechanics of Aligner Treatment
Fig. 7.1 Case nal clinical and radiographic records.
7 • Aligner Treatment in Class II Malocclusion Patients
Fig. 7.1, ’
Fig. 7.11 Case frontal and sagittal views of nal ClinCheck.
77
78
Principles and Biomechanics of Aligner Treatment
Fig. 7.1 Case lateral ra comparison and cephalometric maillar superimposition efore and after therap.
CASE SUMMARY This yearold female patient has no previous orthodontic history, a full mm left and rightside molar class maxil lary alveolar arch width deciency, mm of maxillary crowding, a mm overbite, and an mm overet Seletally she presented a hypodivergent class and a cervical verte brae maturation (C) stage sthetically her face was harmonious in both frontal and lateral views (ig ) esidual growth was insufcient to consider orthopedic treatment Conseuently, taing into account the aesthetics reuest of the patient, the treatment plan was designed to correct the class , achieving nal molar and canine class relationship by molar derotation, seuential distaliation, and elastic ump using nvisalign (Align Technology nc,
San osé, CA, SA) aligners, composite attachments on all the distaliing teeth, and class elastics The average distal iation movement prescribed was mm The patient was instructed to wear the aligners and the class elastics for at least hours per day Aligners were changed every wees until the maxillary second molars were fully distalied, then every days until the rst molars were in their nal position, and then every days till the end of treatment To obtain the prescribed results, aligners were needed (ig ) The clinical results were good and showed nal molar and canine class relationships with correct overbite and overet The prole of the lower third of the face was improved with respect to the initial records (ig )
Fig. 7.1 Case initial clinical and radiographic records.
7 • Aligner Treatment in Class II Malocclusion Patients
Fig. 7.1, ’ Continued
79
8
Principles and Biomechanics of Aligner Treatment
Fig. 7.1, ’
Fig. 7.1 Case sagittal views of initial intermediate nal pre and postump ClinCheck.
Fig. 7.1 Case nal clinical and radiographic records.
7 • Aligner Treatment in Class II Malocclusion Patients
Fig. 7.1, ’
81
8
Principles and Biomechanics of Aligner Treatment
References oyd sthetic orthodontic treatment using the nvisalign appliance for moderate to complex malocclusions J Dent Educ anda S, Tosun S Correction of Anteroposterior Discrepancies anover ar uintessence ublishing Co rec , anson , ranco C, et al ntraoral distalier effects with conventional and seletal anchorage a metaanalysis Am J Orthod Dentofacial Orthop ontana , Coani , Caprioglio A oncompliance maxillary molar distaliing appliances an overview of the last decade Prog Orthod golf , eole A, pshaw S actors associated with orthodontic patient compliance with intraoral elastic and headgear wear Am J Orthod Dentofacial Orthop uiy A, odrigues de Almeida , anson , et al Sagittal, vertical, and transverse changes conseuent to maxillary molar distaliation with the pendulum appliance Am J Orthod Dentofacial Orthop ontana , Coani , Caprioglio A Soft tissue, seletal and dentoal veolar changes following conventional anchorage molar distaliation therapy in class nongrowing subects a multicentric retrospective study Prog Orthod usy nuence of force systems on archwirebracet combinations Am J Orthod Dentofacial Orthop ossini , arrini S, Castroorio T, et al fcacy of clear aligners in controlling orthodontic tooth movement a systematic review Angle Orthod ossini , arrini S, eregibus A, et al Controlling orthodontic tooth movement with clear aligners An updated systematic review regarding efcacy and efciency J Aligner Orthod Simon , eilig , Schware , et al orces and moments generated by removable thermoplastic aligners incisor torue, premolar dero tation, and molar distaliation Am J Orthod Dentofacial Orthop
rae CT, corray S, olce C, et al rthodontic tooth movement with clear aligners ISRN Dent avera S, Castroorio T, arino , et al axillary molar distaliation with aligners in adult patients a multicenter retrospective study Prog Orthod Simon , eilig , Schware , et al Treatment outcome and efcacy of an aligner techniue—regarding incisor torue, premolar derota tion and molar distaliation BMC Oral ealth aher S Dr Sam Daher’s echniues for Class II Correction ith Inis align and Elastics httpssamaonawscomlearninvisalign docspxAACpdf auette xtraction treatment with nvisalign n Tuncay , ed he Inisalign Sstem ew alden uintessence ublishing Co arino , Castroorio T, aher S, et al ffectiveness of composite attachments in controlling uppermolar movement with aligners J Clin Orthod ome , eña , artíne , et al nitial force systems during bodily tooth movement with plastic aligners and composite attach ments a threedimensional nite element analysis Angle Orthod Comba , arrini S, ossini , et al Threedimensional nite element analysis of uppercanine distaliation with clear aligners, composite attachments, and class elastics J Clin Orthod Solanoendoa , Sonnemberg , Solanoeina , et al ow effec tive is the nvisalign® system in expansion movement with x’ aligners Clin Oral Inestig anson , Sathler , ernandes T, et al Correction of class mal occlusion with class elastics a systematic review Am J Orthod Dentofacial Orthop ohamed , asha S, AlThomali axillary molar distaliation with miniscrewsupported appliances in class malocclusion a systematic review Angle Orthod amada , uroda S, eguchi T, et al istal movement of maxillary molars using miniscrew anchorage in the buccal interradicular region Angle Orthod
8
Aligners in Extraction Cases KENJI OJIMA, CHISATO DAN, and RAVINDRA NANDA
Introduction The demand for inconspicuous and natural-feeling orthodontic appliances has been rising over time. The introduction of the Invisalign system marked a signicant step forward in orthodontics in that it allowed for inconspicuous orthodontic correction using appliances with a natural feel. The original Invisalign system, however, came with serious limitations: the control of root movement was not possible and it was difcult to move large teeth over signicant distances.1-1 ecent advances in the uality of materials, the use of attachments, and the introduction of a new force system have epanded the range of applications of the Invisalign system from mild crowding to more difcult etraction cases.11-1 s is the case with all orthodontic procedures, one of the greatest sources of dissatisfaction among adult patients with aligner therapy is the long treatment time. This report describes the treatment of a patient with severe anterior crowding who was treated with Invisalign appliances after the etraction1- of her three remaining premolars. er lower left premolar had already been removed. photobiomodulation device was used to possibly accelerate tooth movement.
Diagnosis and Treatment Plan hen this -year-old female presented at our clinic, she epressed a desire to correct her maillary anterior crowding and improve the aesthetic appearance of her smile. hile the patient’s facial prole was straight, both lips were slightly recessive with regard to the -line ig. .1. n intraoral eamination showed a class II molar relationship with a -mm overet, a -mm overbite, and coincident midlines. The arch-length discrepancy was 1 mm in the mailla and 1 mm in the mandible. Infralabioversion was noted for both upper canines and a marked buccal shift of the upper left second molar ig. .. ephalometric analysis indicated a skeletal class II relationship with a steep mandibular plane angle ig. .. The upper central incisors were slightly inclined lingually and the lower central incisors were inclined labially. The lateral gap in the mandibular head conrmed by her panoramic -ray did not impede mandibular function. There was evidence of slight regression in the periodontal tissue around the upper canines with no tooth mobility, the maimum pocket depth was mm. ased on these observations, the patient was diagnosed as a skeletal class II case with infralabioversion of the
maillary canines and a steep mandibular plane angle. The treatment plan called for the retraction of both upper and lower incisors: 1. mm of movement was reuired in the mailla and 1. mm in the mandible. irst, the two upper rst premolars and lower right second premolar were etracted. er lower left second premolar had been removed in her early teens. Therefore, to allow for mesial movement, her upper left second molar and upper right third molar were etracted, too. ecause the patient epressed concern about the poor aesthetics of ed orthodontic appliances over a potentially long period of time, the decision was made to implement the Invisalign system in conunction with photobiomodulation rthoulse to possibly speed up treatment.1- linheck software was used to analye the location, angle, and need for the recontouring of the canine in relation to the nal desired occlusion ig. .. deuate incisor retraction in this class II malocclusion reuired the -mm distal movement of the upper rst molars and -mm mesial movement of the lower rst molars. ven after the etractions, there was insufcient space to move the maillary anterior teeth by premolar etraction alone. To create more space, the overepansion of the dental arches was reuired. Tooth movements were simulated on the linheck software ig. ., the amount of epansion reuired in each arch was estimated, the positions were planned, and the shapes of the reuired attachments were decided.
Treatment Progress Three third molars were removed ecept the upper left third molar before treatment. fter the etraction of the upper premolars and lower left rst premolar, aligner treatment was initiated. e used all the maillary teeth from rst molar to rst molar as anchorage for the distaliation of the second molars. In the mandible, we used all the teeth ecluding the canines and second premolars as anchorage for the mesial movement of the canines. ince the root of the lower right canine was angled outward, we moved the tooth simply by tipping the lower left canine was moved bodily along with its root. The distaliation of the upper second molars was completed in 1 weeks and distal movement of the upper rst molars was completed weeks later. The closure of the lower etraction space continued during this period with mesial movement of the lower rst molars. fter months of treatment, retraction movement of the upper canines was completed, with the incisors of the midline corrected. t this point, we recalculated the retraction 83
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Principles and Biomechanics of Aligner Treatment
A
B
C
D
E
F
Fig. 8.1 (A) Smile appearance of the patient. (B) Frontal picture at rest. (C) Three-quarter picture at rest. (D) Three-quarter smile appearance. () Prole smiling. (F) Prole at rest.
8 • Aligners in traction Cases
Fig. 8.2 nitial intraoral pictures.
A
B Fig. 8.3 (A) nitial orthopantomograph. (B) nitial lateral -ra.
85
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Principles and Biomechanics of Aligner Treatment
A
B
C
D
Fig. 8.4 ClinChec initial stage. (A) Frontal ie. (B) ight ie. (C) eft ie. (D) pper arch ie. () oer arch ie.
E
A
B Fig. 8.5 Schematic representation of ertical orthodontic tooth moement design in the frontal plane (A). Amount of ertical moements for upper canines and central incisors (B).
8 • Aligners in traction Cases
space for the maillary incisors by means of a panoramic -ray. ince the mandibular etraction spaces were closed, we could use all the teeth from second premolar to second premolar, including the canines, as anchorage for the mesial movement of the lower rst molars. The aligner margins were trimmed about mm to accommodate direct-bonded hooks on the upper rst canines. ingual buttons were bonded to the distobuccal edges of the lower rst molars, and class II elastics . in, o were prescribed to be worn hours per day. To prevent the mesial tipping of the lower rst molars, vertical rectangular attachments were added to their mesiobuccal edges ig. .. Improvement was seen in the anteroposterior relationship after use of the class II elastics, and a class I relationship was established in the buccal segments. The net phase involved the retraction of the upper anterior teeth. fter
87
months of treatment, the rst linheck phase was nished igs. . and .. The distaliation of the upper rst molars was complete, with space visible at the mesial edge of the upper left rst molar. The movement of the lower second premolars and canines had closed all the mandibular spaces. The shapes and positions of the attachments were modied for the renement phase. The crown positions were considered together with the root positions to decide the optimal conditions. fter months of treatment, the aligner compatibility and the crown and root positions were all consistent with the computer-simulated predictions igs. . and .1. In the nal stages of renement, the occlusal contact of all upper and lower molars and a one-to-two-tooth occlusal relationship in the buccal segments were conrmed. oth the overbite and overet were 1 mm. fter a total 1 months of treatment, all buttons, hooks, and attachments were removed ig. .11. The patient was instructed to wear class II elastics at night for an additional 1 months.
Treatment Results
Fig. 8.6 Schematic representation of attachments and auiliaries required in etraction cases.
A
The patient’s chief complaint—the infralabioversion of the canines—was resolved, and the improvement in gingival esthetics yielded a pleasant smile igs. .1, .1, and .1. ue to the retraction of the maillary incisors, the upper lip was particularly natural and relaed, and the lips were positioned appropriately in relation to the -line. class I molar relationship with symmetric arches was achieved, and all spaces were closed ig. .1. The physiologically correct overbite and overet were coincident with the dental and facial midlines.
B Fig. 8.7 (A) nitial smile esthetic analsis. (B) ClinChec simulation into the smile frame of the Digital Smile Design softare.
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Principles and Biomechanics of Aligner Treatment
Fig. 8.8 Treatment progresses in the frontal ie.
Fig. 8.9 Treatment progresses in the right ie.
8 • Aligners in traction Cases
Fig. 8.9, cont’d
Fig. 8.10 Treatment progresses in the occlusal ies. Continued
89
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Principles and Biomechanics of Aligner Treatment
Fig. 8.10, cont’d
Fig. 8.11 Posttreatment pictures.
8 • Aligners in traction Cases
91
A
B Fig. 8.12 Final smile esthetic analsis.
Fig. 8.13 (A) Final orthopantomograph. (B) Final lateral -ra.
The posttreatment protrusive and lateral movements of the mandible were smooth and linear. It is likely that the patient was using considerable force when biting in centric occlusion due to nervousness during the initial eamination. anoramic -rays conrmed that there was no change in the level of the alveolar bone, which remained stable and in a healthy condition. o signs of root resorption were noted. cephalometric analysis indicated that the mandibular plane angle was slightly reduced. uperimpositions showed that while the upper and lower incisors were retruded, their aes were upright and closer to the norm.
class II elastics to enhance intermaillary anchorage. If an elastic is attached directly to an aligner, however, the plastic will separate from the teeth, making it more difcult to maintain control over mesial and distal tooth movements. In the case shown here, direct-bonded hooks were attached to the upper canines to allow the teeth to rotate both mesially and distally within the aligners, leaving a margin of more than mm between the incisal edges and the aligners. ather than attach the elastics in the mandibular arch which was serving as anchorage directly to the aligners, they were attached to buttons on the buccal surfaces of the rst molars. This kept the aligners from lifting off the teeth, while vertical rectangular attachments on the mesial edges of the molars prevented mesial angulation. This avoided the tipping of the teeth adacent to the mandibular etraction sites. ecause the patient found the original predicted length of treatment unacceptable, rthoulse- was used in conunction with the aligners to possibly accelerate treatment time. espite the lack of published accounts of the effectiveness of this device beyond its application to fied appliances, the patient was instructed to use it for 1 minutes every evening. e were able to shorten the interval between aligner changes to days, resulting in a remarkable reduction in the treatment time to ust
Discussion ligners appeal to adults because of their pleasing aesthetics and their ability to produce gradual tooth movements with light forces over the course of time. The focus of previous reports has been on cases that did not reuire etractions or those with only partial etractions. This is perhaps due more to the difculty of closing spaces without crown tipping than to the difculty of moving teeth. hen etraction spaces are closed with aligners, a bowing effect is often caused by the sagging of the plastic around the etraction sites. This effect can be prevented by using
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Principles and Biomechanics of Aligner Treatment
Fig. 8.14 Posttreatment etraoral pictures.
8 • Aligners in traction Cases
93
Fig. 8.15 Final stage of the ClinChec renement.
Conclusion 1 months. The patient eperienced no discomfort from the rthoulse device or from the faster aligner changes. he finished treatment with no interferences in protrusive or lateral mandibular movements and no esthetic concerns.
ot only are aligners aesthetically pleasing to adult patients, but the ease with which they can be removed makes them etremely safe. In the future, aligners are likely to be used in more comple cases involving rotations, deep
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Principles and Biomechanics of Aligner Treatment
overbites, open bites, and unusual etractions. urther clinical investigations into the effects of accelerated tooth movement in such cases are reuired.
References 1. laskalic , oyd, . rthodontic treatment of a mildly crowded malocclusion using the Invisalign system. Austral Orthod J. 11:1-. . oyd , iller , laskalic . The Invisalign system in adult orthodontics: mild crowding and space closure cases. J Clin Orthod. :-1. . iancotti , i irolamo . Treatment of severe maillary crowding using Invisalign and ed appliances. J Clin Orthod. :-. . chupp , aubrich , ermens . . glichkeiten und grenen der schienentherapie in der kieferorthop. die Zahnmed. 1:11-1. . chupp , aubrich , eumann I. Treatment of anterior open bite with the Invisalign system. J Clin Orthod. 1:1-. . uarneri , liverio T, ilvestre I, et al. pen bite treatment using clear aligners. Angle Orthod. 1:1-1. . rieger , eiferth , arinello I, et al. Invisalign treatment in the anterior region. J Orofac Orthop. 1:-. . iancotti , arina . Treatment of collapsed arches using the Invisalign system. J Clin Orthod. 1:1-. . achan , haturvedi T. rthodontic management of buccally erupted ectopic canine with two case reports. Contemp Clin Dent. 1:1-1. 1. oyd . sthetic orthodontic treatment using the Invisalign appliance for moderate to comple malocclusions. J Dent Educ. :-. 11. astro£orio T, arino , aaro , et al. pper-incisor root control with Invisalign appliances. J Clin Orthod. 1:-1. 1. ahn , apf , athe , et al. Toruing an upper central incisor with aligners: acting forces and biomechanical principles. Eur J Orthod. 1:-1. 1. chupp , aubrich , eumann I. Invisalign treatment of patients with craniomandibular disorders. Int rthod. 1:-. 1. iller , corray , omack , et al. comparison of treatment impacts between Invisalign aligner and ed appliance therapy during the rst week of treatment. Am J Orthod. 11:e1-. 1. oyd . omple orthodontic treatment using a new protocol for the Invisalign appliance. J Clin Orthod. 1:-. 1. laskalic , oyd . linical evolution of the Invisalign appliance. J Calif Dent Assoc. :-. 1. omack . our-premolar etraction treatment with Invisalign. J Clin Orthod. :-. 1. ima , an , ishiyama , et al. ccelerated etraction treatment with Invisalign. J Clin Orthod. 1:-.
1. owman , elena , paraga , et al. reative aduncts for clear aligners, part : etraction and interdisciplinary treatment. J Clin Orthod. 1:-. . iorillo , esta , rassi . pper canine etraction in adult cases with unusual malocclusions. J Clin Orthod. 1:1-11. 1. omíngue , elásue . ffect of low-level laser therapy on pain following activation of orthodontic nal archwires: a randomied controlled clinical trial. Photomed Laser Surg. 11:-. . au , antarci , haughnessy T, et al. hotobiomodulation accelerates orthodontic alignment in the early phase of treatment. Prog Orthod. 11:. . oas , onale-ima . ow-level light therapy of the eye and brain. Eye Brain. 11:-. . ells T, ong-iley T, eroeve , et al. itochondrial signal transduction in accelerated wound and retinal healing by nearinfrared light therapy. Mitochondrion. :-. . atanabe , ohensky , reeman T, et al. ypoic induction of in the growth plate: suppresses chondrocyte autophagy. J Cell Physiol 1:1-. . asha T, oureld , brahamse . ow-intensity laser irradiation at nm stimulates transcription of genes involved in the electron transport chain. Photomed Laser Surg. 11:-. . akabayashi , amba , atsumoto , et al. ffect of irradiation by semiconductor laser on responses evoked in trigeminal caudal neurons by tooth pulp stimulation. Laser Surg Med. 11: -1. . awasaki , himiu . ffects of low-energy laser irradiation on bone remodeling during eperimental tooth movement in rats. Laser Surg Med. :-1. . antiwong ., de la uente , krenes , et al. hotobiomodulation accelerates orthodontic alignment in the early phase of treatment. Prog Orthod. 11:. . haughnessy T, antarci , au , et al. Intraoral photobiomodulation-induced orthodontic tooth alignment: a preliminary study. BMC Oral ealth. 11:. 1. ahas , amara , astegar-ari T. ecrowding of lower anterior segment with and without photobiomodulation: a single center, randomied clinical trial. Lasers Med Sci. 1:1-1. . arvalho-obato , arcia , asem , et al. Tooth movement in orthodontic treatment with low-level laser therapy: a systematic review of human and animal studies. Photomed Laser Surg. 1:-. . ima , an , umagai , et al. Invisalign treatment accelerated by photobiomodulation. J Clin Orthod. 1:-1. . ima , an , umagai , et al. pper molar distaliation with Invisalign treatment accelerated by photobiomodulation. J Clin Orthod. 11:-. . ima , an , umagai , et al. ccelerated etraction treatment with the Invisalign system and photobiomodulation. J Clin Orthod. :11-1.
9
Open-Bite Treatment with Aligners ALDO GIANCOTTI and GIANLUCA MAMPIERI
In recent years, aligners have shown to be an extraordinary and effective tool to correct open-bite cases. Such unexpected results make them the gold standard in the treatment of malocclusions characterized by vertical excess as in open-bite cases. Open bite is challenging to treat for its multifactorial etiology and for high incidence of relapse. he aim of this chapter is to show strategies and protocols for the treatment of anterior open bite by clear aligners.
Diagnosis of Anterior Open Bite Obviously, a proper diagnosis is essential in determining the appropriate corrective measures. It is possible to classify three types of open bite . ental . entoskeletal . Skeletal enerally, skeletal open bite reuires an orthosurgical approach. Instead, dental and dentoskeletal open-bite cases can be treated only by means of orthodontics.
Biomechanics for Anterior Open-Bite Correction he biomechanics for anterior open-bite correction can be achieved either by extruding the incisors or intruding the posterior teeth, or by a combination of both. or the nonsurgical treatment of adult patients, some guidelines consider extraction and retraction for dental open-bite correction. limited number of open-bite cases is suitable for such type of treatment. ental open-bite cases are mostly associated with the following characteristics n n n n n
ormal craniofacial pattern Incisor proclination ndererupted anterior teeth ittle or no gingival display on smile o more than to mm of upper incisor exposure at rest
If the anterior open bite depends only on tooth position, it is a relative open bite the biomechanics for the correction are easy, as follows n n
educing incisor proclination to produce a relative extrusion ure extrusion of incisors by extrusive attachments
he amount of incisal and gingival display needs to be assessed clinically prior to deciding if pure extrusion is desired from a smile esthetics point of view.
hen dentoskeletal factors are important in determining the cause of open bite, it is often caused by posterior dentoalveolar excess as well as by both downward and backward mandibular rotation.- hese types of open bite with a skeletal component caused by heredity andor supererupted posterior teeth reuire complex orthodontic treatments with active molar intrusion or even maor orthognathic surgery., In case of a dentoskeletal open bite, specic procedures have been designed to intrude posterior teeth or, at least, prevent molar eruption or extrusion in the attempt to reduce or control anterior facial height, especially during the growing age high-pull headgear, lower transpalatal arch with resin button, and posterior bite blocks. he introduction of temporary anchorage devices s has allowed an active intrusion of posterior teeth also in adult patients with a conseuent mandibular counterclockwise rotation and improvement of anterior open bite. xtraction of posterior teeth is another strategic approach to correct anterior open bite. Indeed, when indicated, molar extraction for caries or periodontal reasons could be highly effective in reducing facial height. orward movement of the terminal molars allows the mandible to hinge upward and forward. It has been postulated that mm of intrusive vertical movement of the molars results in approximately to mm of bite closure by mandibular counterclockwise rotation. In the treatment of a dentoskeletal open-bite case, one shall observe some biomechanical principles. ny procedure meant to increase facial height by means of extrusion of posterior teeth must be avoided. eveling the arches is usually not to be considered appropriate, and the maintenance or creation of a curve of Spee would be desirable. urthermore, banding of second molars should be avoided to prevent any extrusion movement when molars are engaged on the arch wire. he abovementioned scenario can be easily avoided by using aligners, which allow for nonextrusion and represent a great advantage during open-bite treatment. his is why a number of researchers consider aligners as the gold standard.
Aligner Protocols for Open-Bite Treatment CLINCHECK SOFTWARE DESIGN he clear aligner treatment of open-bite cases depends on the type of malocclusion reuiring correction, and specic biomechanics have to be reuested by checking the appropriate 95
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Principles and Biomechanics of Aligner Treatment
boxes on the prescription form of the linheck software program to generate a predictable linheck plan. ental open bite, also known as relative open bite, clinically features excessive incisor proclination it can be treated only by reducing incisor proclination, producing a relative extrusion of anterior teeth. or these movements, attachments are not strictly reuired. he rst step consists of recovering the needed space in both arches. Space can be gained by arch expansion andor interproximal reduction I. he decision depends on the shape of the arches, tooth dimension, periodontal structure, and condition. ligners can easily modify the shape of the arch, and it is later possible to retract the incisors obtaining enough relative extrusion in mild open bite to solve the issue.
ATTACHMENTS IN OPEN-BITE CORRECTION In case of more severe dental open bites, anterior teeth extrusion can be strategic. ndoubtedly, extrusion is the
most difcult movement to reproduce with aligners. In such conditions, attachments play an important role to determine tooth extrusion. ttachments and anchorage optimized anterior extrusive attachments are automatically placed on the incisors by the software when pure extrusion of . mm or more is detected igs. . and .. onventional extrusion attachments have a rectangular shape with beveled edge toward the gingiva to allow for optimal pressure from the aligner and then achieve proper extrusion ig. .. hese attachments could be positioned also on the palatal surface if aesthetic reasons are a priority ig. .. Our experience suggests that the use of rectangular-shaped attachments with beveled edge toward the gingiva with the largest possible dimensions in relation to the incisor and most incisal possible allowed for an optimal control of relative and absolute incisor extrusion. nchorage attachments can have different shapes and dimensions, according to the type andor number of teeth involved.
Fig. 9.1 Optimized extrusive attachments of the Invisalign system.
Fig. 9.2 The anterior extrusive forces and reciprocal posterior intrusive forces work in synergy to correct the anterior open ite.
9 • OpenBite Treatment with Aligners
Fig. 9. ectangular shape attachments with eveled edge toward gingiva.
he dentoskeletal open-bite treatment complies to a more complex protocol to correct the malocclusion. Indeed, in this type of open bite, the skeletal structure shows a dentoalveolar posterior vertical excess, which is responsible for an increased lower facial height. or this reason, anterior tooth extrusion alone is not enough for correction, and one shall reduce the posterior vertical excess by dental intrusion. osterior dental intrusion results in a mandibular counterclockwise rotation mainly responsible for the open bite’s correction, which can be veried by nal cephalometric values. he anterior extrusive forces and reciprocal posterior intrusive forces work in synergy to close the anterior open bite see ig. .. he amount of posterior intrusion may range from less than . mm to a maximum of . mm. eyond the range of predictability for aligner movements, it may be necessary to use s. olar intrusion can be planned with aligners, and therefore we dene it as selective intrusion. he rst and second molars in the upper arch and rst molars and bicuspids in the lower arch are involved in the plan. he protocol related to attachment placement for anchorage usually envisages rectangular attachments on the molars and optimized ones on bicuspids. s for intrusion teeth, the ofcial Invisalign protocol does not include the use of attachments. Some experienced clinicians prefer to add occlusal rectangular attachments to increase intrusive components and thus increase effectiveness see ig. .. In more severe open-bite malocclusions, some clinicians prefer to stage posterior intrusion seuentially for a more predictable clinical outcome rst the maxillary second molars, then the rst molars, and then the second premolars. n important aspect to make predictable planning with aligners is to design an overcorrection. In the linheck we have to see the nal virtual occlusion with
97
Fig. 9. Palatal attachments and occlusal attachments on upper molars.
heavy anterior occlusal contacts and at least mm of positive overbite. Our point of view concerning dental intrusion is that the most important effect of aligners in reducing posterior vertical excess is the bite-block effect, which is caused by two layers of aligner material between posterior teeth. It allows to effectively intrude posterior teeth, hence enabling subseuent autorotation of the mandible and reducing anterior facial height. he bite-block effect cannot be uantitatively priorly planned or displayed in the virtual digital setup by linheck, but we can routinely observe it clinically, especially in patients with a normal or larger mandible. In nal, to guarantee the maintenance of the result over time, it is essential to use ivera, the clear retainer produced by lign, because the posterior occlusal coverage will prevent the reeruption of posterior teeth.
Case Report 1 CASE SUMMAR -year-old female patient presented a severe crowding, an unpleasant smile, as well as speech issues. linical extraoral examination showed a convex skeletal soft tissue prole due to a retrognathic mandible and incompetent lips at rest with mentalis and lip strain when the lips were pursed together. Intraoral examination evidenced class II canine and class I molar relationship on both sides, an anterior open bite, an excessive incisor proclination, and crowding on both arches ig. . able .. ephalometric analysis showed increased mandibular plane angle and increased lower anterior facial height see able . later. osterior maxillary dentoalveolar heights were dened as excessive ig. ..
9
Principles and Biomechanics of Aligner Treatment
Fig. 9.5 ase tudy Initial clinical records.
9 • OpenBite Treatment with Aligners
99
PROBLEM LIST Table 9.1 ase tudy Prolem ist Dimension
Seletal
Anteroposterior
n
onvex skeletal prole due to retrognathic mandile
n
lass II canine relationship
n
keletal class II
n
xcessive incisor proclination
n
Increased lower anterior facial height
n
Overite mm
n
Increased mandiular plane angle
n
arrow upper arch
n
Increased maxillary posterior dentoalveolar heights
ertical
Dental
Transverse
n
Soft Tisse n
etrusive lower lip and chin
n
entalis muscle strain at rest
n
Incompetent lips
arrow upper and lower arch
Fig. 9.6 ase tudy Pretreatment xray records.
TREATMENT OBECTIES
TREATMENT ALTERNATIES
he main treatment obectives were to close the anterior open bite, obtain class I canine relationships, correct the excessive incisor proclination, and improve smile arc able ..
he treatment alternatives consisted of the following
TREATMENT PLAN he treatment of dentoskeletal open bite reuires closure of anterior open bite through a combination of retraction and extrusion of the upper incisors and by intrusion of posterior maxillary dentition to enable subseuent autorotation of the mandible with an improvement of vertical and sagittal relationship. dditional treatment goals included leveling and aligning, optimizing the posterior occlusion, aiming at class I canine relationships, as well as ideal overbite and overet to improve the facial prole and obtain natural lip competence without mentalis strain.
. Orthosurgical treatment, including a eort I osteotomy with posterior maxillary impaction . onventional treatment with intrusion of the posterior maxillary dentition by using s for skeletal anchorage . xtraction treatment to reduce the vertical dimension while easing reduction of the anterior protrusion and mandibular crowding
TREATMENT SEUENCE orrection was achieved by means of the expansion of the upper arch by mm that allowed tooth alignment and the correction of upper incisor proclination. In the lower arch, molar and premolar torue was corrected. he optimized attachments on cuspids and rst bicuspids in the upper arch were programmed to perform the anchorage unit necessary
1
Principles and Biomechanics of Aligner Treatment
Table 9. ase tudy Treatment Oectives Dimension
Seletal
Anteroposterior
n
ertical
n
Dental
Soft Tisse
educe skeletal convexity with autorotation of the mandile
n
Improve class II canine relationship y autorotation of the mandile
n
Improve soft tissue prole
educe lower facial height and man diular plane angle y intruding the maxillary and mandiular posterior teeth and autorotating the mandile
n
Improve anterior overite and smile arc y intruding upper posterior teeth and maintaining the vertical position of the anterior teeth.
n
educe interlaial gap
n
Improve the prole y intruding maxillary dentoalveolar sites.
n
Achieve lip closure without activation of mentalis muscles
Transverse
n
xpand upper and lower arch
to achieve the reuired reduction of incisor proclination gaining enough space by means of I and arch expansion. Intrusion of posterior teeth determined by aligners would have favored a counterclockwise rotation of the mandible, thus promoting the anterior open-bite correction ig. .. Open-bite correction occurred by means of a rst phase of aligners and a nishing stage including aligners. In addition, the expansion, together with the correction of the tipping of cuspids and bicuspids, allowed for coordination of both arches and a slight mesial mandibular repositioning with an optimization of the occlusal relationships and correction of class II canine malocclusion.
TREATMENT RESULTS fter months of therapy, treatment obectives set in the pretreatment plan were achieved. he anterior open bite had been completely closed, a proper overbite and overet
had been corrected, and class I canine relationship had been established ig. .. he extraoral records show an evident improvement in the patient’s smile. he pre- and posttreatment cephalometric showed mm of intrusion of the upper molars determined by aligners. Such dental movement resulted in a mandibular counterclockwise rotation mainly responsible for the closure of the anterior open bite and the reduction of vertical skeletal values in the nal cephalometric assessment. aused by two layers of aligner material between the posterior teeth, molar intrusion is identied by clinicians as the bite-block effect and enables not only the correction of anterior open bite by means of the mandible’s counterclockwise rotation, but also an improvement of the class II relationship, thanks to mandibular repositioning ig. . able .. ollow-up after months showed the great stability of the results ensured by means of ivera retainers. he use of aligners for retention provides a long-term posterior intrusive
Fig. 9.7 ase tudy Pre and postlinheck superimposition.
9 • OpenBite Treatment with Aligners
Fig. 9. ase tudy inal clinical records.
11
12
Principles and Biomechanics of Aligner Treatment
Fig. 9.9 ase tudy Posttreatment xray records.
Table 9. ase tudy ummary of ephalometric hanges Cephalometric orphologic Assessment
ean SD
Pretreatment
Posttreatment
axillary position A
° 6 .
°
°
andiular position B
° 6 .
°
°
agittal aw relation AB
° 6 .
°
°
axillary Inclination AP
° 6 .
°
°
andiular inclination O
° 6 .
°
°
ertical aw relation APO
° 6 .
°
°
axillary incisor inclination AP
° 6 .°
°
°
andiular incisor inclination oge
° 6 .°
°
°
6 .
. 6 .
6 .
° 6 .
°
°
SAGITTAL SKELETAL RELATIONS
ERTICAL SKELETAL RELATIONS
DENTOBASAL RELATIONS
andiular incisor compensation AP DENTAL RELATIONS Overet Overite Interincisal angle
force similar to that of posterior bite blocks, which is recommended for vertical control after anterior open-bite treatment.
Case Report CASE SUMMAR -year-old female presented with a mild skeletal class II, division malocclusion, moderate lower and
mild upper crowding, moderate anterior open bite, a severely hyperdivergent skeletal pattern, and an unbalanced transverse relationship. linical examination indicated excessive lower facial height with a gummy smile and a typical long-face appearance ig. . able .. he patient had a -mm anterior open bite, with posterior occlusion only on the second molars. adiographic examination confirmed the vertical excess in the lower face ig. .. wo treatment options were presented surgical correction or aligner therapy with s.
9 • OpenBite Treatment with Aligners
Fig. 9.1 ase tudy Initial clinical records.
1
1
Principles and Biomechanics of Aligner Treatment
PROBLEM LIST Table 9. ase tudy Prolem ist Dimension
Seletal
Anteroposterior
n
ertical
Transverse
Dental
keletal class II division malocclusion
Soft Tisse
n
Occlusal contacts only on the second molars
n
xcessive incisors proclination
n
oderate anterior open ite mm
n
etrusive lower lip and chin
n
Increased lower anterior facial height
n
ong face type
n
xcessive maxillary posterior growth
n
ummy smile
n
evere hyperdivergent pattern
n
entalis muscle strain at rest
n
Transversal skeletal deciency
n
oderate lower and mild upper crowding
n
nalanced occlusion relationships
Fig. 9.11 ase tudy Pretreatment xray records.
TREATMENT OBECTIES he treatment aim was to close anterior open bite, correct excessive vertical facial height, obtain balanced occlusal contacts with a class I molar relationship, and improve patient’s smile able ..
he treatment also included the achievement of class I molar relationships, dental alignment and leveling, optimization of posterior transversal occlusion, as well as reaching ideal overbite and overet to improve the facial prole and smile arc. he pre- and postvirtual plan is shown in ig. .
TREATMENT PLAN
TREATMENT ALTERNATIES
he skeletal class II and the anterior open bite reuired correction by counterclockwise rotation of the mandible allowed by maxillary molar intrusion, without moving the vertical position of anterior teeth. Such upward and forward rotation would reduce facial height and improve vertical and sagittal relationships with proper dental torue and inclination.
he treatment alternatives consisted of the following . Invisalign therapy with intrusion of the posterior maxillary and mandibular dentition by using s as skeletal anchorage . Orthosurgical treatment including a eort I osteotomy with posterior maxillary impaction
9 • OpenBite Treatment with Aligners
15
Table 9. ase tudy Treatment Oectives Dimension
Seletal
Anteroposterior
n
ertical
Transverse
Dental
Soft Tisse
Improve class II y counterclockwise mandiular rotation induced y molar intrusion
n
Improve class II molar relationship and incisor inclination y counterclockwise mandiular rotation induced y molar intrusion
n
Improve soft tissue prole
n
educe lower facial height maxillary downward clockwise rotation and hyperdivergent pattern y intruding upper posterior teeth and conse uent autorotation of the mandile
n
Improve anterior overite and smile arc y intruding upper posterior teeth and maintain ing the vertical position of the anterior teeth
n
Improve the prole y intruding maxillary dentoalveolar sites
n
xpand maxillary arch dentally
n
Improve alanced occlusion relationships y mandile autorotation
n
educe upper and lower crowding y contact points stripping
TREATMENT SEUENCE he patient chose the second option. osterior maxillary dentoalveolar intrusion for vertical correction was achieved by miniscrew mechanics. uccal mm 3 mm Spider in miniscrews were placed mesially to each maxillary rst molar. n auxiliary . in 3 . in stainless steel sectional wire was placed on each side of the working cast coated at the ends with composite resin for easier placement in the mouth. surgical hook was crimped at each rst molar and -g nickel titanium coil springs were tied from these to the s. o avoid the development of undesirable molar labial torue due to the force application on the buccal side only, the plan included use of upper and lower aligners to control it. he digital treatment plan was designed for alignment, I, and, if needed, tooth retrusion. Instead, posterior intrusion and anterior extrusion, or other vertical movements as in ase , were carefully avoided because the difference between and aligner mechanics could lead to imperfect aligner t and inadeuate torue control ig. .. he aligner treatment consisted of upper and lower aligners, plus upper and lower renement aligners. ustomized, precise cuts of the aligners were designed on the linheck to accommodate the auxiliary wires, usually affecting two or three teeth on each side.
TREATMENT RESULTS
Fig. 9.12 ase tudy Pre and postlinheck superimposition.
deuate intrusion and conseuent closing of open bite were achieved in months with dental alignment and leveling ig. .. oals set in the pretreatment plan were totally reached after months of therapy ig. . able .. he anterior open bite had been completely corrected, resulting in a proper overbite and overet. class I molar relationship had been established. atient’s smile positively changed by improving vertical lower facial height and gummy smile. he values in the nal cephalometric assessment show a -mm intrusion of the upper molars and reduction of the vertical skeletal determined by aligners ig. . see able ..
16
Principles and Biomechanics of Aligner Treatment
Fig. 9.1 ase tudy Invisalign with temporary anchorage devices for posterior intrusion.
Fig. 9.1 ase tudy nd of posterior intrusion.
9 • OpenBite Treatment with Aligners
Fig. 9.15 ase tudy inal clinical records.
17
1
Principles and Biomechanics of Aligner Treatment
Table 9. ase tudy ummary of ephalometric hanges Cephalometric orphologic Assessment
ean SD
Pretreatment
Posttreatment
axillary position A
° 6 .
°
°
andiular position P
° 6 .
°
°
agittal aw relation AP
° 6 .
°
°
SAGITTAL SKELETAL RELATIONS
ERTICAL SKELETAL RELATIONS axillary inclination AP
° 6 .
°
°
andiular inclination O
° 6 .
°
°
ertical aw relation APO DENTOBASAL RELATIONS
° 6 .
°
°
axillary incisor inclination AP
° 6 .
°
°
andiular incisor inclination O
6 .
°
°
andiular incisor compensation AP
6 .
DENTAL RELATIONS Overet
. 6 .
Overite
6 .
° 6 .
°
°
Interincisal angle
Fig. 9.16 ase tudy adiographic control and cephalometric superimposition.
References . gan , ields . Open bite a review of etiology and management. Pediatr Dent. -. . Subtelny , Sakuda . Open bite diagnosis and treatment. Am J Orthod. -. . angialosi . Skeletal morphologic features of anterior open bite. Am J Orthod. -. . opez-avito , allen , ittle , et al. nterior open-bite malocclusion a longitudinal -year post-retention evaluation of orthodontically treated patients. Am J Orthod. -. . anda S. atterns of vertical growth in the face. Am J Orthod Dentofacial Orthop. -. . ozza , ucedero , accetti , et al. arly orthodontic treatment of skeletal open bite malocclusion a systematic review. Angle Orthod. -. . etzenberger , uf S, ancherz . he compensatory mechanism in high angle malocclusions a comparison of subects in the mixed and permanent dentition. Angle Ortho. -.
. Sarver , eissman S. onsurgical treatment of open bite in nongrowing patients. Am J Orthod Dentofacial Orthop. -. . uhn . ontrol of anterior vertical dimension and proper selection of extraoral anchorage. Angle Orthod. -. . earson . reatment of vertical backward rotating type growth pattern patients in todays’ environment. eeting of Southern ssoc of Orthodontists, irmingham, , October -, conrmed by personal communication. . ahoum I. ertical proportions a guide for prognosis and treatment in anterior open bite. Am J Orthod. -. . eilsen I. ertical malocclusions etiology, development, diagnosis and some aspects of treatment. Angle Orthod. -. . aralabakis , iagtzis S, outounzakis . ephalometric characteristics of open bite in adults a three-dimensional cephalometric evaluation. Int J Adult Orthod Orthognath Surg. -. . iancotti , arino , ampieri . se of clear aligners in open bite cases an unexpected treatment option. J Orthod. -. . ay S. Clear Aligner Technique. atavia, I uintessence ublishing .
10
Deep Bite LUIS HUANCA, SIMONE PARRINI, FRANCESCO GARINO, and TOMMASO CASTROFLORIO
Introduction Deep bite is dened as an increase of the overbite, and it is measured as vertical overlap of the incisors perpendicular to the occlusal plane.1,2 It can be divided into dentoalveolar origin (overeruption of frontal teeth) and skeletal origin (decreased lower face height, low mandibular plane angle). Deep bite prevalence varies from to 1 depending on the threshold values applied, ethnic group, and gender.– correlation between deep bite and sagittal molar mal occlusion was described. In particular, class II molar maloc clusion is signicantl associated with increased overbite compared with class I malocclusion. egarding treatment strategies in deep bite patients, there is not a complete consensus in the eisting literature. 21 review published b illet et al. assessed that it is not possible to provide an evidencebased guidance to rec ommend or discourage an tpe of orthodontic treatment to correct class II, division 2 malocclusion in children. s assessed b anda,1 it is possible to adopt three differ ent therapeutic strategies etrusion of posterior teeth, intru sion of upper andor lower incisors, and aring of anterior teeth (also known as relative intrusion). ll these effects can be obtained together depending on the clinical case. using clear aligners instead of ed appliance, the orthodontist can start correcting the overbite on both arches from the beginning rather than wait a few months to bond the lower arch after the upper teeth have been aredintruded to open the bite. he alternative would be to bond bite ramps since the beginning, but these ma prove uncomfortable for patients and reuire adustments and etra cleanup at some point in the future.
Leveling of the Curve of Spee deep curve of pee is often associated with severe anterior deep bite. etruding posterior teeth, mainl premolars, and intruding anterior teeth, it is possible to atten the arches and achieve an ideal overbite.1 It is difcult to dene the net contribution of molar and premolar etrusion versus canine and incisor intrusion to the overall curve of pee attening, as the act as a recipro cal source of anchorage. henever attempting to etrude the premolars, canines and incisors will serve as an anchor age unit, and the will pa the price of a most welcome in trusion side effect. n the contrar, ever time clinicians would love to achieve intrusion of the anterior teeth, the premolars represent the primar source of anchorage, and the ma etrude a benecial side effect of anterior intru sion. ven if, b using clear aligners and an attentive plani
cation of tooth movements, clinicians ma be persuaded that the can achieve specic tooth movements (i.e., intru sion of the anteriors onletrusion of the posteriors onl), the should be aware that ewton’s third law of phsics (action and reaction) plas an important role in distin guishing the real world from the virtual onscreen world of setup, where the laws of phsics are often violated. It is a common belief that deep bite correction and curve of pee attening is easier to achieve in growing patients, as etrusion of molars and premolars can be supported b vertical growth while grow is still happening. n the contrar, curve of pee correction in adults ma be much harder, as the orthodontist cannot hope in an inuence or help from the vertical skeletal dimension. ur thermore, curve of pee tends to deepen with aging, with supererupted lower incisors and canines that ma also show lingual inclination (upper incisors can also show lingual incli nation as a conseuence). his becomes clinicall evident in a twostep mandibular occlusal plane with a net step between the rst premolars and canines. cessive wearing of the inci sal edges ma also be evident in such circumstances. hile planning deep bite correction in an adult, the orthodontist should also plan an eventual restorative treatment that is needed to reestablish the proper crown anatom. lign echnolog has created a proprietar protocol for deep bite correction called Invisalign . his protocol in volves incisor and canine intrusion through a combination of intrusion forces eerted b the aligners on the occlusal edge of the teeth and a pressure area on the lingual surface (igs. 1.1 and 1.2). his combination of force sstems eerts a nal intrusive force that is supposed to be parallel to the tooth long ais. o achieve the desired intrusion on the anterior teeth, an adeuate anchorage should be pro vided in the premolar and molar area. retention attach ments have been specicall designed for premolars, and the ma serve as pure anchorage attachments or as active etrusion attachments in case of etrusion of the premo lars. oth movement of anterior intrusion and posterior etrusion are automaticall activated if the threshold of movement is more than . mm. olar anchorage should be provided with conventional attachments (rectangular and horiontal) to counteract the occlusal movement of the aligner determined b the anterior intrusion design. linicians working with other clear aligner sstems than Invisalign, or those who feel the need for alternative ap proaches even when using Invisalign aligners, ma create a similar protocol using standard attachments and a person alied staging of intrusion. ingival beveled attachments ma be used as an alterna tive to retention attachments on premolars to achieve retention and etrusion. hen planning etrusion, it is 109
110
Principles and Biomechanics of Aligner Treatment
Fig. 10.1 Schematic representation of the optimized bite ramps designed by Align Technology (San José, CA, SA and embedded into aligners They change shape and positioning along the treatment to proide optimal spport to loer incisors at eery stage of treatment
Pressure area Aligner forces
Resultant force
Fig. 10.2 Schematic representation of pressre areas designed by Align Technology (San José, CA, SA and incorporated into the aligner to redirect the intrsie force along the long ais of the incisor
useful to ask for a slower etrusion rate (e.g., .1 mm per stage instead of the classic .2 mm) to avoid lack of track ing within the aligner b respecting the phsiologic toler ance of the periodontal ligament. ome clinicians recommend a superiorl conve (reverse) curve of pee as nal obective of the alternative. hile this is not the real clinical goal, the assumption behind this pre scription is that the elasticit and resilience of the plastic material will ver unlikel allow a full epression of the prescribed movement. the wa the lack of epression of certain movements can be compensated b this reuested hpercorrection, that is the aligner euivalent of the re verse curve ii wires.1 he clinician who has the feeling that the hpercorrection is reall happening ma alwas stop the use of the aligners to avoid unwanted side effects. urve of pee correction should alwas begin with lower incisor proclination to obtain a relative intrusion and start to recover the space reuired during the real intrusion movement. ince the epression of the lingual root torue information on lower incisors has not et been investigated, it can be useful to prescribe etra lingual root torue. gain, it is important to remember that interproimal spac ing ma help the intrusion movements. paper b iu and u11 eplained how force changes as a conseuence of different intrusion strategies for deep bite correction with clear aligners. ith the same activation (.2 mm of intrusion) and rectangular attachments placed
on the premolars and rst molars, the canines eperienced the largest intrusive force when intruded alone. hen ap pling contemporar intrusion of canines and incisors, the canines received a larger intrusive force than incisors. he incisors received similar forces of intrusion if intruded alone or together with canines. irst premolars eperienced the largest etrusive forces when all anterior teeth were in truded. trusion forces were eerted also on canines and lateral incisors when differential staging for intrusion of canines and incisors was used. It is not surprising that the intrusive force eerted b clear aligners is higher when less elements are involved, and it is partiall lost when multiple elements are intruded at the same time. he incisors show an overall scarce tendenc to feel intrusion forces. his ma lead to the clinical suggestion of a staggered approach, al ternating canine and incisor intrusion to eert higher and more specic forces on canines and incisors. herefore, a clinical suggestion in prescribing anterior intrusion with an clear aligner sstem could consider the following 1. Intrusion from canine to canine at a rate of .1 mm per stage (rst create an etra space of . mm to hold until the movement has been completed) 2. oriontal rectangular beveled gingival attachments on lower bicuspids those attachments should be mm wide, 1. mm high, 1.2 mm thick at the gingival mar gin, and tapered to .2 mm thickness at the occlusal margin . oriontal rectangular beveled occlusal attachments on lower canines those attachments should be mm wide, 1. mm high, 1.2 mm thick at the occlusal margin, and tapered to .2 mm at the gingival margin . oriontal rectangular attachments on molars to increase anchorage . lternate intrusion of canines and incisors . lace the attachments occlusall avoiding an interarch interferences
Leveling the Upper Incisors linical observation of patient face and smile and gingival displa guide the clinician in the choice of how to correct an ecessive overbite.12 In fact, in man clinical cases, a pure lower posterior etrusioncurve of pee attening ma not be the best option, but the mechanics in the lower arch should be accompanied b vertical movements on the upper anteriors. During treatment planning with aligner orthodontics, it is possible to prescribe a selective upper or lower incisor intrusion. It is not surprising that when tring to correct an eces sive overbite, the upper smile arch needs special care, as Dr. David arver taught to the whole profession. he intrusion of the upper incisors should be limited to preserve conveit of the smile and enough crown eposure to preserve a outhful smile while aging. pper incisors and canines ma be intruded b relative intrusion (i.e., b providing vestibular crown torue, some intrusion happens as a geometric conseuence of this move ment). o allow a full epression of this movement, it is strongl suggested to prescribe an etra lingual root torue. ower idge (lign echnolog, an osè, , ) at the gingival third of the crown ma also help in achieving
10 • eep Bite
labial crown torue. imon et al.1 demonstrated that even a buccal attachment on upper incisors could provide lingual root torue control. pper relative intrusion and incisor crown vestibularia tion is often needed in those adults who have a ver deep curve of pee, where the correction starts with labial move ment of the lower incisors. nough clearance (anterior overet with no contacts) should be provided to avoid poste rior disclusion due to hard collisions among upper and lower incisors due to occlusal interferences. nce achievement of the correct amount of relative intrusion occurs, pure intrusion can be applied. ith lign echnolog protocol, when the intrusion reuest overpasses the .mm threshold, a lingual pressure area will be added to enhance the parallelism of the nal vector of intrusive force to the long ais of the tooth. ite ramps ma be added on the lingual part of the teeth to help during deep bite correction (see ig. 1.1). he are optimied—in other words, the can change shape and position during the different stages of treatment to keep contact with the lower incisors as a conseuence of upper incisor buccal crown torue (the get longer while the up per incisor crowns get ared). hen bite ramps are present, no palatal pressure areas can be added at the same time on the same tooth as the two features need some space on the lingual surfaces of incisors andor canines. here are some claims of a possible intrusive effect of bite ramps on upper incisors because of the imposed precontact. hile this claim ma answer a logical thought, it is important to re member that we pass most of the time in a discluded posi tion of the aw respecting our vertical freewa space. s a conseuence, patients bite over the bite ramps for a few seconds per da onl when swallowing, thus the real effect of bite ramps as booster of upper intrusion is uestionable. he wa bite ramps keep the aws constantl discluded is the same principle of man functional appliances, whose main obective is to enhance lower posterior etrusion b providing an anterior precontact. In this sense, bite ramps, supported b class II elastics, ma favor lower posterior teeth etrusion, especiall in growing patients. It is impor tant to notice that, with aligners, elastics are recommended to boost posterior etrusion, as the clear aligner is other wise creating a selflimiting barrier that can limit posterior etrusion. n the contrar with functional appliances, where the molars and premolars are left free to erupt, the posterior vertical correction happens naturall. eviewing the eisting literature about deep bite correc tion with aligners, hosravi et al.1 showed that in their sample of deep bite patients treated with Invisalign aligners, the cephalometric analses performed to deter mine the mechanism b which the Invisalign appliance corrects deep bites suggest that proclination of mandibular incisors, along with intrusion of maillar incisors and etrusion of mandibular molars, is the primar source of deep bite correction with the Invisalign appliance.
Case Report 1 he patient presented at the age of 1 with a severe over bite, a deep curve of pee associated with lower crowding, and important lingualiation of the lower right canine (igs. 1. and 1.). is chief complaint was to avoid the
Fig. 10.3 nitial etraoral photos
111
112
Principles and Biomechanics of Aligner Treatment
Fig. 10.4 nitial intraoral photos
traumatism he felt ever time he bit on the palatal mucosa close to the retroincisal papilla. s visible on tracings, he had a slight class II while the skeletal vertical dimension was not as severel reduced as the dental deep bite could have suggested. e had agenesis of the second lower premolars (ig. 1.). he treatment plan included the preservation of the lower second deciduous molars and eventual implant substitution of second premolars later in life. he treatment lasted 2 months with four sets of correc tions of decreasing length. he length of the treatment was
due to the severe curve of pee that needed a big effort to be attened. ligner change was planned ever das from the beginning. he curve of pee attening was obtained rst with proclination of the lower incisor and relative in trusion, then space was created mesial and distal to lower incisors and canines, and maintained while performing in trusion with staggered alternate movements (frog protocol) (ig. 1.). nchorage attachments (rectangular horion tal) were used on the premolars but also on the canines, as at moments the served as anchorage unit for incisor intrusion (ig. 1.).
10 • eep Bite
A
C
113
B
Fig. 10.5 (A nitial orthopantomography (B nitial lateral -ray (C nitial tracing
Fig. 10.6 Treatment stages scheme illstrating the frog protocol in hich alternate intrsion moements of canines and incisors are planned n the ais teeth are displayed, hile on the ais treatment stages are displayed eery stage corresponds to e aligners The blue lines indicate actie moements, brown lines indicate oercorrection stages Red arrows down indicate hen attachments shold be placed, hile red arrows p indicate hen attachments shold be remoed
114
Principles and Biomechanics of Aligner Treatment
A
B Fig. 10.7 (A nitial cre of Spee (B inal cre of Spee
he deep bite was full corrected on the lower arch (igs. 1., 1., and 1.1), as superimpositions on the ellaasion plane (ig. 1.11) show an unaltered verti cal position of the upper incisors. n important intrusion of the lower incisors is associated with a slight advance ment of the point of the mandible probabl due to the use of class II elastics.
Due to the presence of the lower deciduous molars, the patient ended into a canine class I and molar headtohead relationship. he lower right deciduous molar responded perfectl to the therap, while the left one was uite unre sponsive to vertical movement, and a slight underbite was left at this level. he patient’s chief complaint of retroinci sal traumatism was full achieved.
Fig. 10.8 inal etraoral photos
10 • eep Bite
115
Fig. 10.9 inal intraoral photos
Case Report 2 n 1earold male patient presented with molar class II malocclusion, skeletal class II, low mandibular plane angle, deep bite with an increased curve of pee, and crowding in the incisor area (igs. 1.12 and 1.1). atient’s main concern was the deep overbite and crowding in the upper incisors area. he treatment plan was designed to obtain bodil distal movements of upper molars, premolars, and canines to achieve a dental molar and canine class I.
seuential distaliation protocol was applied together with the use of class II elastics (.1 in, . o) during the distaliation process (see hapter ). ttachments were placed on all distaliing teeth to con trol bodil distal movements (igs. 1.1 and 1.1). he deep bite was corrected mainl through intrusion of the lower anterior teeth, using the protocol, and the presence of bite ramps on the upper incisors. he amount of lower intrusion in the incisor area was .1 mm, and to reinforce the posterior anchorage, attach ments were placed on bicuspids.
116
Principles and Biomechanics of Aligner Treatment
A
B
Fig. 10.10 (A inal orthopantomography (B inal lateral -ray (C inal tracing
C
Fig. 10.11 Tracing sperimposition
set of Invisalign aligners was produced to perform the distaliation movements on the upper arch and to cor rect the lower curve of pee. ligner change was planned ever 2 weeks at the beginning of treatment, ever 1 das after months of treatment, then ever das after months of treatment. During the distaliation phase, the patient was instructed to wear class II elastics (.2 in, . o) bilaterall to reinforce anterior anchorage while distaliing premolars. o anchor class II elastics, hooks were planned on upper canines while buccal tubes were bonded on the lower rst molars. n additional set of 1 upper and lower aligners was reuested to nalie the treatment obtaining good nal intercuspation in the molar and bicuspid areas and a nal overet of 2 mm. he treatment was concluded with bilateral class I molar and canine relationship, ecellent upper and lower align ment, and good leveling of the curve of pee (igs. 1.1, 1.1, and 1.1). he total treatment duration was 2 months.
10 • eep Bite
Fig. 10.12 nitial etraoral photos
Fig. 10.13 nitial intraoral photos
117
118
Principles and Biomechanics of Aligner Treatment
A
B Fig. 10.14 (A nitial orthopantomography (B nitial lateral -ray
Fig. 10.15 n progress intraoral photos olar tbes ere sed on loer rst molars for class elastic anchorage
10 • eep Bite
Fig. 10.16 inal etraoral photos
Fig. 10.17 inal intraoral photos
119
120
Principles and Biomechanics of Aligner Treatment
A
B Fig. 10.18 (A inal orthopantomography (B inal lateral -ray
References 1. anda . Biomechanics and Esthetic Strategies in Clinical Orthodontics. aunders 2. 2. Dan , reuter , ifakakis I, et al. tabilit and relapse after orth odontic treatment of deep bite cases—a longterm followup stud. Eur J Orthod. 21222. . ielsen I. ertical malocclusions etiolog, development, diagnosis and some aspects of treatment. Angle Orthod. 111()22. . u , Dücker , ritsch , et al. cclusal status and prevalence of occlusal malocclusion traits among earold schoolchildren. Eur J Orthod. 2122. . roft r , ields , arver D. Contemporary Orthodontics. th ed. lsevier 21. . ausche , uck , arer . revalence of malocclusions in the earl mied dentition and orthodontic treatment need. Eur J Orthod. 22()22. . illett D, unningham , ’rien D, et al. rthodontic treatment for deep bite and retroclined upper front teeth in children. Cochrane Database Syst Rev. 21(2)D2.
. ans , nlow D. Essential of Facial roth. eedham ress 1. . arshall D, aspersen , ardinger , et al. Development of the curve of pee. Am J Orthod Dentofac Orthop. 21() 2. 1. lifford , rr , urden D. he effects of increasing the reverse curve of pee in a lower archwire eamined using a dnamic photoelastic gelatine model. Eur J Orthod. 121()21222. 11. iu , u . orce changes associated with different intrusion strategies for deepbite correction b clear aligners. Angle Orthod. 21()1. 12. arver D. he importance of incisor positioning in the esthetic smile the smile arc. Am J Orthod Dentofac Orthop. 2112(2) 111. 1. imon , eilig , chware , et al. reatment outcome and efcac of an aligner techniue—regarding incisor torue, premolar derotation and molar distaliation. BC Oral ealth. 211. 1. hosravi , ohanim , uoel , et al. anagement of overbite with the Invisalign appliance. Am J Orthod Dentofac Orthop. 2111()1,e2.
11
Interceptive Orthodontics with Aligners TOMMASO CASTROFLORIO, SERENA RAVERA, and FRANCESCO GARINO
Introduction Early orthodontic treatment is still a debated argument. According to the existing literature, the usefulness of interceptive orthodontics is controversial even if many sagittal, vertical, and transversal malocclusions are clearly visible and diagnosed in the early mixed dentition.1 Some authors recommend interceptive treatment because many malocclusions tend to worsen with age.2 Some other studies have underlined that orthodontic treatment during the pubertal phase may positively inuence malocclusion improvements, contributing to the stability of nal results.3 However, a recent review stated that removable functional appliances can produce short-term good dentoalveolar effects rather than skeletal improvements.4 Furthermore, a recent update of a Cochrane review claimed that on the basis of low to moderate quality evidence, providing early orthodontic treatment for children with prominent upper front teeth is more effective for reducing the incidence of incisal trauma than providing one course of orthodontic treatment in adolescence. There appear to be no other advantages of providing early treatment when compared to late treatment.5 The reduction of upper incisor proclination should not be underestimated because the smile appearance is important among overall esthetics for adolescents as well as for children younger than 10 years of age. Correcting smile alterations, even in young children, may be fundamental in preventing bullying or teasing from others and in improving the quality of social interactions, preserving healthy psychologic development.6 Interceptive orthodontics could be also recommended when detecting bad oral habits as atypical swallowing and mouth breathing have been found to be strictly related to malocclusion worsening.7 Moreover, early orthodontic treatment mainly consisting in maxillary expansion and mandibular advancement has been indicated to treat pediatric sleep apnea patients.8 The controversial results deriving from the existing literature in terms of effectiveness of interceptive orthodontics are mainly related to the lack of specic indicators of the right biologic timing of intervention. Although no skeletal maturity indicator may be considered to have a full diagnostic reliability in the identication of the maxillary growth peak and of the pubertal growth spurt or mandibular growth peak, treatment timing according to available indicators (mainly hand and wrist maturation [HWM] and cervical vertebral maturation [CVM] methods) has yielded more favorable outcomes. The use of the HWM or CVM methods (or others) may still be recommended for treatment planning, even though large individual responsiveness and dentoalveolar compensations have been reported, even in pubertal patients.9
In this chapter, we focus on clear aligner interceptive orthodontics of class II retrognathic patients and of patients with maxillary constrictions, highlighting the recommendations for case selection and treatment planning, showing some case reports.
Maxillary Expansion Transverse maxillary constriction and maxillary crowding in children are problems commonly encountered and treated by orthodontists.10-12 Interceptive orthodontics with maxillary expansion (ME) is one of the treatment options recommended for children with transverse deciencies with the intent to increase the transverse widths of the maxilla. This approach is particularly important in children with posterior crossbite because it has been shown to determine abnormal chewing patterns and the development of skeletal asymmetries.13,14 Expansion is especially desirable for young class II division I patients who have constricted maxillae because the transverse deciency does not self-correct between the deciduous, mixed, and permanent dentitions.15 Increasing maxillary arch width could improve class II with retrognathic mandible, inducing a spontaneous forward repositioning of the mandible, even if there is still a lack of general consensus on this issue.16,17 Maxillary arches are also expanded routinely to solve anterior crowding and improve the smile esthetics of kids.6,18-20 Crowding of the permanent incisors, with associated rotations and/or anterior crossbite, is commonly observed during eruption of the permanent lateral incisors. The rationale of interceptive treatment in the early mixed dentition is to generate adequate space for the spontaneous alignment of the permanent upper lateral incisors prior to complete eruption. When crowding is limited to a few millimeters, normal growth could provide adequate space, but when the palate is narrow and the crowding exceeds this amount, maxillary expansion could represent an effective procedure.21 As stated by Rosa et al.,21 when planning interceptive rapid maxillary expansion (RME) in absence of posterior crossbite, the clinician should consider that rst permanent molars are often tilted buccally, and a further buccal movement will produce periodontal problems and posterior occlusal interferences related to the deepening of the Wilson curve. Furthermore, the amount of anterior expansion could not be enough to solve the anterior crowding. Ideally the expansion should be limited to the anterior region of the arch, while permanent molars should move in a palatal direction. Considering these aspects, maxillary expansion by anchorage on deciduous teeth has been proposed. The benet 121
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Principles and Biomechanics of Aligner Treatment
of anchoring the expander on second deciduous molars and deciduous canines was the gain of 5 to 6 mm in upper arch perimeter. The gained space is sufcient to solve anterior crowding without tilting buccally permanent molars. However, those teeth spontaneously follow the buccal movement of deciduous molars for about 60% of their movement. When thinking about differences between several activation protocols for maxillary expansion, a recent systematic review22 helps us to understand some outcomes comparing slow maxillary expansion (SME) and RME; there is moderate evidence showing that maxillary transverse diameters increase signicantly within both groups in the shortterm,23 but SME protocol is more predictive of bodily upper molar movement, while the RME protocol produces more tipping movement in the molar region.24 RME uses heavier interrupted forces to maximize orthopedic effects, and slow palatal expansion uses lighter continuous forces to move teeth at rates purported to be more physiologic.11 Aligners use intermittent light forces to move teeth, and intermittent forces are able to produce orthodontic tooth movement with less cell damage in the periodontium.25 Since it has been stated that light, continuous forces seem to be perceived as intermittent forces by the periodontium due to its viscoelastic nature,26 the expansion produced by aligners could be described as SME. A clear aligner maxillary expansion protocol has been recently proposed (Invisalign First, Align Technology, Inc., San José, CA, USA). Aligners could overcome some of the limitations presented by palatal expander particularly in non-crossbite cases. With these appliances, it is possible to control the movement of all the teeth in the maxillary arch, aiming to produce an initial alignment and leveling while expanding the arch. Aligners can be really helpful in controlling maxillary rst molars not only on the frontal plane but on the horizontal and sagittal planes, too, avoiding all the issues mentioned earlier in relation to potential periodontal problems. Furthermore, aligners can control the expansion limited to the anterior region of the arch to generate adequate space for the spontaneous alignment of the permanent upper lateral incisors prior to complete eruption. Because of the short clinical crowns of deciduous teeth, specic attachment shapes were designed to increase aligner retention and control the tipping movement to obtain torque compensation and avoid a deepening of the curve of Wilson (Fig. 11.1). Regarding staging, two options are available at the moment: (1) Permanent molars (if required by the treatment plan) will be moved buccally, using the rest of the arch as anchorage, and only once they have reached their nal position will the deciduous molars and canines be moved buccally using permanent molars and incisors as anchorage units. (2) Permanent molars and deciduous teeth are moved buccally in a simultaneous manner (Fig. 11.2). Because of the geometry of the aligners, their distal portions are not stiff enough to support a predictable buccal movement of so many teeth at the same time, making this staging not the rst-line treatment option. Timing is another important factor to be considered. The best timing to expand maxillary arch is during the early mixed dentition, before upper permanent lateral incisor eruption and after the permanent molars are fully erupted and in occlusion. This timing is favorable as the midpalatal suture is more immature.27 In young children, up to age 8 or 9 years, little force is needed. Up to that age, a transpalatal
Fig. 11.1 Invisalign First optimized attachments for maxillary expansion.
F
F
Fig. 11.2 Invisalign First maxillary expansion protocol staging.
lingual arch releasing light continuous forces for dental expansion also will open the midpalatal suture.28 Therefore, it can be assumed that intermittent forces released by aligners can be sufcient in children up to 8 or 9 years of age to act on the transversal dimension of the maxilla. A recent clinical trial conducted at the University of Torino (Torino, Italy) in which clear aligners and RPE effects in patients with maxillary constriction were measured on digital models, suggests that: n
n
n
A signicant increase in palatal volume, so as in the other parameters, has been proved for both treatments. The RPE slightly outperform clear aligners considering all the parameters tested. The compliance and the clinical condition could affect the potential results achievable by the clear aligners.
The Clear Aligners demonstrated a reasonable ability to achieve palatal expansion. Since the materials have improved over the last years, so as the academic efforts to better understand the potential of CAT, substantial advances can be expected in the near future.58
Expansion Case Reports For the following case reports, three-dimensional (3D) evaluation of upper arch and palate morphology was performed according to a previous study by Bizzarro et al.29 The upper arches were scanned using a 3D scanner (iTero Element). The 3D data were imported to a reverse modeling software package called Geomagic Studio (3D Systems, Inc).30 Intermolar, intersecond deciduous molar, and intercanine transverse widths at the cusps and gingival levels were measured (Fig. 11.3), as well as anterior and posterior palatal depths at the cusp level, palatal surface area (Fig. 11.4), and volume (Fig. 11.5).
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123
CC
CG
cC
cG MC
MG
GP Line 7
DP
Fig. 11.3 CG intercanine widths assessed at gingival level, CC intercanine widths assessed at cusp level, cG inter-E widths assessed at gingival level, cC inter-E widths assessed at cusp level, MG intermolar widths assessed at gingival level, MC intermolar widths assessed at cusp level.
GP MSP DP
Fig. 11.5 The palatal surface area was dened by the median sagittal (MSP), distal (DP), and gingival (GP) planes as boundaries of the palate. The distal plane (DP) passed through two points at the distal of the rst upper permanent molars.
was planned within the ClinCheck, along with alignment of central and lateral incisors. The patient was instructed to change the aligners every week, and control examinations were planned every 6 weeks. Pre- and postexpansion scan screenshots are shown in Fig. 11.6. The expansion phase lasted 8 months. The palatal volume increased from 3843.54 mm3 to 5330.89 mm3 due not only to the vestibular dental tipping but also increased interarch widths measured at both gingival and a cuspal levels. Quantitative evaluations of intraarch widths, palatal areas, and volumes for this case are summarized in Table 11.1 as Case 1 reports.
CASE STUDY 2
Fig. 11.4 The anterior and posterior depth of the palatal vault is dened as the vertical distance from the contact line between the cusp of the right and left canine and mesiopalatal cusp tips of the right and left rst molars to the palatal vault, respectively. The palatal volume was dened by the median sagittal, distal, and gingival planes as boundaries of the palate. The distal plane (DP) passed through two points at the distal of the rst upper permanent molars. The gingival plane (GP) was created by intersecting the distal and median sagittal planes (MSP) through the center of incisive papilla, which is considered a stable point structure.31 All planes were perpendicular to each other.
Consider a 9-year-old girl with upper anterior crowding and deep bite. Invisalign First was adopted, and sequential expansion of molars rst and then deciduous teeth was planned within the ClinCheck, along with the alignment of central and lateral incisors. The patient was instructed to change the aligners every week and control examinations were planned every 2 months. Pre- and postexpansion scan screenshots are shown in Fig. 11.7. The expansion phase lasted 6 months. The palatal volume increased from 4342.64 mm3 to 6948.68 mm3 due not only to the vestibular dental tipping but also increased interarch widths measured at both a gingival and a cuspal level. Quantitative evaluations of intraarch widths, palatal areas, and volumes for this case are summarized in Table 11.1 as Case 2 reports.
CASE STUDY 1 Consider an 8-year-old boy with upper central incisor protrusion, mild upper anterior crowding, and palatal tipping of deciduous teeth. Invisalign First was adopted, and sequential expansion of molars rst and then deciduous teeth
Class II Malocclusion Class II malocclusion is the most frequent skeletal sagittal disharmonies in the white population.32 Diagnosis using
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A A
B Fig. 11.7 Case 2 pre- (A) and post (B) therapy scans of the maxillary arch.
B Fig. 11.6 Case 1 pre- (A) and post (B) therapy scans of the maxillary arch.
Table 11.1 Pre- and post-treatment volumetric and linear measurements obtained in the reported cases. A mm2
V mm3
CG mm
CC mm
cG mm
cC mm
MG mm
MC mm
Case 1 pre
1105.91
3843.54
22.6
29.1
28.2
32.2
32.6
36.8
Case 1 post
1316.57
5330.89
27.6
36.7
33.4
39.7
36
42.1
Case 2 pre
1111.67
4342.64
24.4
32.1
29.8
34.5
35.1
39.7
Case 2 post
1478.69
6948.68
26.3
37.5
32.9
39.5
35.4
42.1
A, Palatal surface area; CC, intercanine widths assessed at cusp level; cC, inter-E widths assessed at cusp level; CG, intercanine widths assessed at gingival level; cG, inter-E widths assessed at gingival level; MC, intermolar widths assessed at cusp level; MG, intermolar widths assessed at gingival level; V, palatal volume.
cephalometric tracings may highlight different dental or skeletal components of class II malocclusion: upper incisor proclination, lower incisor retroclination, mandibular retrognathia, ipomandibulia, maxillary protrusion, ipermaxillia, or different combinations of these components.
Mandible retrusion has been found to be the main factor in most basal class II malocclusions.33,34 One orthopedic approach developed to treat mandibular skeletal retrusion in growing patients is the forward repositioning of the mandible,35,36 even if a general consensus about the efcacy and
11 • Interceptive Orthodontics with Aligners
efciency of this approach is still missing36 37 (probably for inconsistent evidence of homogeneous interventions,37 38 wide variations in individual responsiveness,39 and different timings in orthodontic intervention9), and undergoing mandibular advancement in specic growth phases has been reported to have a key role in successful treatment outcomes. Several studies have shown that the optimal biologic timing for the achievement of skeletal effects is the circumpubertal growth period,40-43 when the greater mandibular growth response occurs, so that treatment can start in the early mixed dentition.41 The pubertal peak can be identied by several growth indicators, including skeletal maturation (cervical vertebrae maturation method, hand-wrist radiographs), dental maturation, and chronologic age,42 44 45 and more recently the reliability of gingival crevicular uid (GCF) biomarkers specic for growth spurt characterization has been under investigation.46 47 A morphologic predictive factor in successful mandible repositioning with functional appliances is the pretreatment mandibular angle (Co-Go-Me angle ,125.5 degrees). As shown by Franchi and Baccetti39 as well as previous animal and human studies,43 a small mandibular angle is correlated with an enhanced responsiveness to mandibular forward positioning, and vice versa. The usual main limitation for removable functional appliances is patient noncompliance, rated by O’Brien as 18% in children, raising to 30% in adolescence.48 Noncompliance can depend on bulky and invasive devices, difculties in speech, impact on social life, esthetics, and public perception, not precise and predicted orthodontic tooth movements. To overcome these limitations, aligner therapy may be considered a good, reliable, and comfortable alternative. The use of the compliance indicators embedded in the aligner represents a good attempt to monitor patient compliance.49 More recently articial intelligence has been introduced in the orthodontic eld to remote monitor patient compliance (Dental Monitoring, Paris, France). Functional treatment of growing class II patients during their pubertal growth spurt can bring about signicant skeletal and dentoalveolar modications. According to Cozza et al.,37 the twin block is the most efcient removable functional appliance because it can stimulate 0.23 mm/month of mandibular growth (for a total of 3.4 mm in 13 months), followed by the Bionator (0.17 mm/month, total 2.8 mm in 12 months), and then the Frankel II (0.09 mm/month, total 2.8 mm in 18 months). The mechanism behind the Clark twin block is based on the presence of an inclined plane, which pushes the mandible forward, liberates the arches, and redirects the occlusal forces to drive the mandibular advancement and arrest maxillary growth.50 Two companies (Align Technology Inc, San José, CA, USA and Leone SPA Company, Sesto Fiorentino, Firenze, Italy) have developed a new feature within aligner appliances,51 combining the twin block and the aligner advantages to stimulate growth of the mandible while aligning and leveling in growing patients. The Leone company appliance called Runner (Fig. 11.8) consists of a series of clear aligners with incorporated occlusal blocks for mandibular advancement, joining the
125
A
B Fig. 11.8 Runner appliance. Upper arch aligner (A) and lower arch aligner (B). (From Arreghini A, et al. Class II treatment with the Runner in adolescent patients: combining twin block efciency with aligner aesthetics. J World Fed Orthod. 2014;3[2]:71–79.)
Fig. 11.9 Intraoral Invisalign First with mandibular advancement feature.
efciency of the twin block with the esthetics and low bulk of clear aligners.52 The Align Technology company appliance is the Invisalign aligner incorporating lateral wings (Figs. 11.9 and 11.10) engaging the mandible in a forward position.
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Principles and Biomechanics of Aligner Treatment
A
B Fig. 11.10 Invisalign First with mandibular advancement feature. Upper arch aligner (A) and lower arch aligner (B)
The mandibular advancement system is divided into three clinical phases: n
n
n
Pre–mandibular advancement phase: the occlusal locks, which prevent expression of mandibular growth, are removed (correction of overbite, maxillary molar rotations, and overjet) Mandibular advancement phase: 2-mm advancement every eight aligners is performed Transition phase (or stabilization phase): maintains the class II correction
Mandibular advancement can be reached only if other eventual occlusal features have been modified (i.e., maxillary molar derotation, dentoalveolar expansion of the upper arch, deep bite and consequent leveling of the curve of Spee, and retroclination of the incisors), so that a prior preparation phase is required before starting mandibular advancement. While the Runner appliance, the twin block, and other functional appliances are built with a single jump repositioning the mandible, the Invisalign appliance is designed to obtain progressive advancement of the mandible with steps of 2 mm every eight aligners. The progressive advancement of the mandible has been demonstrated to be more effective in producing skeletal outcomes both in animal53 54 and human studies.55 At the end of treatment, mandibular advancement is maintained by arch coordination and anterior interference removal.
In class II treatments, assessment of skeletal age and auxologic potential and predicting the direction of mandibular growth constitute strategic factors determining treatment efcacy. Concerning the importance of right timing to choose the beginning of the interceptive class II correction phase, recent perspective-controlled studies by the University of Turin (Italy) aim to compare dental and skeletal effects of 12 months of therapy with the mandibular advancement feature by Invisalign, when performed on growing patients both at CVM2 and CVM3. When used in the pre-pubertal stage of growth, Invisalign® aligners, with Mandibular Advancement feature, have mainly dentoalveolar effects in the short-term period. When used in the pubertal growth phase, the shortterm effects of Mandibular Advancement feature are dento-skeletal, with an annual rate of change comparable to what has been previously described for the Twin Block appliance.59 According to the existent literature, early treatment of class II division I malocclusion should be provided only to reduce the risk of incisal trauma.56 Additionally, dental injuries have been reported to have a negative impact on the emotional and social domains of the oral health–related quality of life. Since this impact is considerable especially for children having active lifestyles, parents will consider that early orthodontic treatment is worth the nancial costs and burden of care.57 Furthermore, there are young patients for whom the malocclusion is esthetically distressing, and they are bullied for this reason. The use of aligners provided for functional and orthopedic adjuncts can have a positive impact on the self-esteem of those patients even during the orthodontic treatment, providing excellent orthodontic care for such children.
Mandibular Advancement Case Reports CASE STUDY 3 Consider a 9-year-old girl, in mixed dentition, with molar class II relationship, deep bite, proclined upper incisors, and retruded mandible. Cephalometric analysis shows a moderate skeletal class II malocclusion, with an ANB angle value of 5 degrees, and Wits value of 7 mm (Fig. 11.11–11.13). According to Baccetti et al.,42 the patient was in a pubertal growth spurt, which is why the treatment plan was designed to focus on mandibular advancement. An Invisalign Teen treatment with the mandibular advancement feature was performed (Fig. 11.14). The appliance was prescribed to determine an advancement of the mandible together with deep bite correction. The ClinCheck plan forecasted 2 mm of advancement every eight stages, and aligners were changed every week. After 6 months of treatment, a bilateral class I molar relationship was achieved (Figs. 11.15–11.16 and 11.17), and dentoskeletal improvements were achieved.
11 • Interceptive Orthodontics with Aligners
Fig. 11.11 Case 3 Initial extraoral pictures.
Fig. 11.12 Case 3 initial intraoral pictures.
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Principles and Biomechanics of Aligner Treatment
Fig. 11.13 Case 3 initial radiographic records.
Fig. 11.14 Case 3 sagittal view of ClinCheck.
Fig. 11.15 Case 3 nal clinical records.
11 • Interceptive Orthodontics with Aligners
129
Fig. 11.16
CASE STUDY 4 Consider a 10-year-old girl in mixed dentition with psychological issues, reporting bullying episodes due to the protrusion of upper incisors and the retrusion of the mandible. The clinical examination showed a molar class II relationship, severe deep bite, skeletal class II with ANB angle of 6 degrees, and Wits value of 5 mm (Fig. 11.18–11.20).
Analyzing the cervical vertebrae maturation on the lateral x-ray, the patient resulted in a CVM3 phase, according to Baccetti et al,42 and is therefore in a phase of accelerated condylar growth. Since the girl was psychologically stressed because of her bad-looking teeth, an additional stress due to a bulky appliance would not have been the best choice. Thus Invisalign Teen with the mandibular advancement feature was adopted (Fig. 11.21).
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Principles and Biomechanics of Aligner Treatment
Initial
12 months later
Wits = 7 mm SNB = 72° Co-Gn = 92 mm U1^PP = 127°
Wits = 3 mm SNB = 74° Co-Gn = 98 mm U1^PP = 107°
Fig. 11.17 Case 3 changes of mandibular prole and cephalometric values before and after therapy.
Fig. 11.18 Case 4 initial clinical and radiographic records.
11 • Interceptive Orthodontics with Aligners
Fig. 11.19
131
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Principles and Biomechanics of Aligner Treatment
Fig. 11.20
In 6 months of treatment, an important correction of the molar relationship and of the proclination of upper incisors was obtained. During the mandibular advancement phase treatment, improvement of the facial prole was the most important motivational factor acting on the patient’s and the parents’ compliance (Figs. 11.22–23 and 11.24).
Conclusions The timing of orthodontic treatment has long been debated. Among the proposed benets of early intervention are the potential for improved response to growth modication. Transversal alterations are frequently seen in general dental practices. Aligners can control the expansion limited to the
Fig. 11.21 Case 4 sagittal view of ClinCheck and superimposition of initial ClinCheck with final ClinCheck (occlusal view).
11 • Interceptive Orthodontics with Aligners
anterior region of the arch to generate adequate space for the spontaneous alignment of the permanent upper lateral incisors prior to complete eruption, helping the future arch development. Researchers in the elds are recommended to dene possibilities and limitations of the approach. Routine early treatment for class II division I malocclusion with retrognathic mandible should not be provided according to the existing quality of evidence. However, there are patients for whom the malocclusion is so esthetically
133
distressing and/or who are bullied signicantly because of it that treatment is certainly indicated. In those cases, the use of a discrete and noninvasive appliance like an aligner with mandibular forward repositioning wings or planes could represent an excellent possibility. Another group of patients for whom the early treatment could be indicated is represented by children with active sports schedules and lifestyles, putting them at risk of incisal trauma because of their large overjet.
Fig. 11.22 Case 4 nal clinical records and changes of mandibular prole.
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Principles and Biomechanics of Aligner Treatment
Fig. 11.23
Initial
12 months later
Wits = 5 mm SNB = 71° Co-Gn = 91 mm U1^PP = 137°
Fig. 11.24 Case 4 cephalometric values before and after therapy.
Wits = 1 mm SNB = 74° Co-Gn = 96 mm U1^PP = 119°
11 • Interceptive Orthodontics with Aligners
References 1. Keski-Nisula KLR, Lusa V, Keski-Nisula L, et al. Occurrence of malocclusion and need of orthodontic treatment in early mixed dentition. Am J Orthod Dentofacial Orthop. 2003;124(6):631-638. 2. Tausche E, Luck O, Harzer W. Prevalence of malocclusions in the early mixed dentition and orthodontic treatment need. Eur J Orthod. 2004;26:237-244. 3. Pavlow SS, McGorray SP, Taylor MG, et al. Effect of early treatment on stability of occlusion in patients with class II malocclusion. Am J Orthod Dentofacial Orthop. 2008;133(2):235-244. 4. Koretsi V, Zymperdikas VF, Papageorgiou SN, et al. Treatment effects of removable functional appliances in patients with class II malocclusion: a systematic review and meta-analysis. Eur J Orthod. 2015;37(4):418-434. 5. Thiruvenkatachari B, Harrison J, Worthington H, et al. Early orthodontic treatment for class II malocclusion reduces the chance of incisal trauma: results of a Cochrane systematic review. Am J Orthod Dentofacial Orthop. 2015;148(1):47-59. 6. Rossini G, Parrini S, Castroorio T, et al. Children’s perceptions of smile esthetics and their inuence on social judgment. Angle Orthod. 2016;86(6):1050-1055. 7. Grippaudo C, Paolantonio EG, Antonini G, et al. Association between oral habits, mouth breathing and malocclusion. Acta Otorhinolaryngol Ital. 2016;36(5):386-394. 8. Huang YS, Guilleminault C. Pediatric obstructive sleep apnea: where do we stand? Adv Otorhinolaryngol. 2017;80:136-144. 9. Perinetti G, Primožiˇc J, Franchi L, et al. Treatment effects of removable functional appliances in pre-pubertal and pubertal class II patients: a systematic review and meta-analysis of controlled studies. PLoS One. 2015;10(10):e0141198. 10. Salzmann JA. An assessment of the occlusion of the teeth of children 6–11 years, United States: National Center for Health Statistics Vital and Health Statistics, Series 11, no. 130, DHEW Publication no. (HRA) 74–1612, Health Resources Administration, Department of Health Education and Welfare. Washington, DC, 1974, US Government Printing Ofce. Am J Orthod Dentofacial Orthop. 1974;66(4): 462-463. 11. Corbridge JK, Campbell PM, Taylor R, et al. Transverse dentoalveolar changes after slow maxillary expansion. Am J Orthod Dentofacial Orthop. 2011;140(3):317-325. 12. Ciuffolo F, Manzoli L, D’Attilio M, et al. Prevalence and distribution by gender of occlusal characteristics in a sample of Italian secondary school students: a cross-sectional study. Eur J Orthod. 2005;27(6): 601-606. 13. Pirttiniemi P, Kantomaa T, Lahtela P. Relationship between craniofacial and condyle path asymmetry in unilateral cross-bite patients. Eur J Orthod. 1990;12(4):408-413. 14. Piancino MG, Talpone F, Dalmasso P, et al. Reverse-sequencing chewing patterns before and after treatment of children with a unilateral posterior crossbite. Eur J Orthod. 2006;28(5):480-484. 15. Bishara SE, Bayati P, Jakobsen JR. Longitudinal comparisons of dental arch changes in normal and untreated class II, division 1 subjects and their clinical implications. Am J Orthod Dentofacial Orthop. 1996;110(5):483-489. 16. Feres MFN, Raza S, Alhadlaq A, et al. Rapid maxillary expansion effects in class II malocclusion: a systematic review. Angle Orthod. 2015;85(6):1070-1079. 17. Lione R, Brunelli V, Franchi L, et al. Mandibular response after rapid maxillary expansion in class II growing patients: a pilot randomized controlled trial. Prog Orthod. 2017;18(1):36. 18. Haas AJ. Palatal expansion: just the beginning of dentofacial orthopedics. Am J Orthod. 1970;57(3):219-255. 19. Martin AJ, Buschang PH, Boley JC, et al. The impact of buccal corridors on smile attractiveness. Eur J Orthod. 2007;29(5):530-537. 20. Maulik C, Nanda R. Dynamic smile analysis in young adults. Am J Orthod Dentofacial Orthop. 2007;132(3):307-315. 21. Rosa M, Lucchi P, Manti G, et al. Rapid palatal expansion in the absence of posterior cross-bite to intercept maxillary incisor crowding in the mixed dentition: a CBCT evaluation of spontaneous changes of untouched permanent molars. Eur J Paediatr Dent. 2016;17(4):286-294. 22. Algharbi M, Bazargani F, Dimberg L. Do different maxillary expansion appliances inuence the outcomes of the treatment? Eur J Orthod. 2017;40(1):97-106.
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23. Martina R, Farella CM, Leone P, et al. Transverse changes determined by rapid and slow maxillary expansion–a low-dose CT-based randomized controlled trial. Orthod Craniofac Res. 2012;15(3): 159-168. 24. Brunetto M, Andriani JDA, Ribeiro GL, et al. Three-dimensional assessment of buccal alveolar bone after rapid and slow maxillary expansion: a clinical trial study. Am J Orthod Dentofacial Orthop. 2013;143(5):633-644. 25. Nakao K, Goto T, Gunjigake KK, et al. Intermittent force induces high RANKL expression in human periodontal ligament cells. J Dent Res. 2007;86(7):623-628. 26. Cattaneo PM, Dalstra M, Melsen B. Strains in periodontal ligament and alveolar bone associated with orthodontic tooth movement analyzed by nite element. Orthodo Craniofac Res. 2009;12(2):120-128. 27. Melsen B. Palatal growth studied on human autopsy material: a histologic microradiographic study. Am J Orthod. 1975;68(1):42-54. 28. De Clerck HJ, Proft WR. Growth modication of the face: a current perspective with emphasis on class III treatment. Am J Orthod Dentofacial Orthop. 2015;148(1):37-46. 29. Bizzarro M, Generali C, Maietta S, et al. Association between 3D palatal morphology and upper arch dimensions in buccally displaced maxillary canines early in mixed dentition. Eur J Orthod. 2018;40(6):592-596. 30. Martorelli M, Maietta S, Gloria A, et al. Design and analysis of 3D customized models of a human mandible. Procedia CIRP. 2016;49:199-202. 31. Shah M, Verma AK, Chaturvedi S. A comparative study to evaluate the vertical position of maxillary central incisor and canine in relation to incisive papilla line. J Forensic Dent Sci. 2014;6(2):92-96. 32. Alhammadi MS, Halboub E, Fayed MS, et al. Global distribution of malocclusion traits: a systematic review. Dental Press J Orthod. 2018; 23(6):40.e1-40.e10. 33. Li P, Feng J, Shen G, et al. Severe class II division 1 malocclusion in an adolescent patient, treated with a novel sagittal-guidance twin-block appliance. Am J Orthod Dentofacial Orthop. 2016;150(1):153-166. 34. McNamara Jr JA. Components of class II malocclusion in children 8–10 years of age. Angle Orthod. 1981;51(3):177-202. 35. Marsico E, Gatto E, Burrascano M, et al. Effectiveness of orthodontic treatment with functional appliances on mandibular growth in the short term. Am J Orthod Dentofacial Orthop. 2011;139(1):24-36. 36. Chen JY, Will LA, Niederman R. Analysis of efcacy of functional appliances on mandibular growth. Am J Orthod Dentofacial Orthop. 2002;122(5):470-476. 37. Cozza P, Baccetti T, Franchi L, et al. Mandibular changes produced by functional appliances in class II malocclusion: a systematic review. Am J Orthod Dentofacial Orthop. 2006;129(5):599.e1-12; discussion e1-6. 38. Antonarakis GS, Kiliaridis S. Short-term anteroposterior treatment effects of functional appliances and extraoral traction on class II malocclusion: a meta-analysis. Angle Orthod. 2007;77(5):907-914. 39. Franchi L, Baccetti T. Prediction of individual mandibular changes induced by functional jaw orthopedics followed by xed appliances in class II patients. Angle Orthod. 2006;76(6):950-954. 40. Perinetti G, Contardo L, Primozic J. Diagnostic accuracy of the cervical vertebral maturation method. Eur J Orthod. 2018;40(4):453-454. 41. McNamara JA, Brudon WL, Kokich VG. Orthodontics and Dentofacial Orthopedics. Needham Press; 2001. 42. Baccetti T, Franchi L, McNamara Jr JA. The cervical vertebral maturation (CVM) method for the assessment of optimal treatment timing in dentofacial orthopedics. Semin Orthod. 2005;11(3):119-129. 43. Petrovic A, Stutzmann J, Lavergne J. Mechanism of craniofacial growth and modus operandi of functional appliances: a cell-level and cybernetic approach to orthodontic decision making. Craniofacial growth theory and orthodontic treatment. Monograph. 1990;23: 13-74. 44. Beit P, Peltomäki T, Schätzle M, et al. Evaluating the agreement of skeletal age assessment based on hand-wrist and cervical vertebrae radiography. Am J Orthod Dentofacial Orthop. 2013;144(6): 838-847. 45. Franchi L, Baccetti T, McNamara Jr JA. Mandibular growth as related to cervical vertebral maturation and body height. Am J Orthod Dentofacial Orthop. 2000;118(3):335-340. 46. Perinetti G, Baccetti T, Contardo L, et al. Gingival crevicular uid alkaline phosphatase activity as a non-invasive biomarker of skeletal maturation. Orthod Craniofac Res. 2011;14(1):44-50.
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47. de Aguiar MC, Perinetti G, Capelli Jr J. The gingival crevicular uid as a source of biomarkers to enhance efciency of orthodontic and functional treatment of growing patients. Biomed Res Int. 2017;2017:3257235. 48. O’Brien K, Wright J, Conboy F, et al. Early treatment for class II division 1 malocclusion with the twin-block appliance: a multi-center, randomized, controlled trial. Am J Orthod Dentofacial Orthop. 2009;135(5):573-579. 49. Tuncay OC, Bowman SJ, Nicozisis JL, et al. Effectiveness of a compliance indicator for clear aligners. J Clin Orthod. 2009;43(4):263-268. 50. Clark WJ. The twin block technique. A functional orthopedic appliance system. Am J Orthod Dentofacial Orthop. 1988;93(1):1-18. 51. Rossini G, Parrini S, Castroorio T, et al. Efcacy of clear aligners in controlling orthodontic tooth movement: a systematic review. Angle Orthod. 2014;85(5):881-889. 52. Arreghini A, Carletti I, Ceccarelli MC, et al. Class II treatment with the Runner in adolescent patients: combining twin block efficiency with aligner aesthetics. J World Fed Orthod. 2014; 3(2):e71-e79. 53. Wang S, Ye L, Li M, et al. Effects of growth hormone and functional appliance on mandibular growth in an adolescent rat model. Angle Orthod. 2018;88(5):624-631.
54. Kim JY, Jue S-S, Bang H-J, et al. Histological alterations from condyle repositioning with functional appliances in rats. J Clin Pediatr Dent. 2018;42(5):391-397. 55. Aras I, Pasaoglu A, Olmez S, et al. Comparison of stepwise vs singlestep advancement with the functional mandibular advancer in class II division 1 treatment. Angle Orthod. 2017;87(1):82-87. 56. Batista KB, Thiruvenkatachari B, Harrison JE, et al. Orthodontic treatment for prominent upper front teeth (class II malocclusion) in children and adolescents. Cochrane Database Syst Rev. 2018;3(3): CD003452. 57. Brierley CA, DiBiase A, Sandler PJ. Early class II treatment. Aust Dent J. 2017;62:4-10. 58. Bruni A. (2021). Clear aligner treatment for transverse maxillary deciency: in vitro study and randomized controlled trial. Doctoral Dissertation, University of Torino, Torino, Italy. 59. Ravera S, Castroorio T, Galati F, Cugliari G, Garino F, Deregibus A, Quinzi V. Short term dentoskeletal effects of mandibular advancement clear aligners in Class II growing patients. A retrospective controlled study according to STROBE Guidelines. Eur J Paediatr Dent. 2021 Jun; 22(2):119-124.
12
The Hybrid Approach in Class II Malocclusions Treatment FRANCESCO GARINO, TOMMASO CASTROFLORIO, and SIMONE PARRINI
Introduction Several protocols have been proposed for treatment of class II malocclusions. In nonextraction protocols, maxillary molar distalization can be used to correct molar relationships in patients with maxillary dentoalveolar protrusion and minor skeletal discrepancies.1 The upper molars can be distalized by means of extraoral or intraoral forces. In recent years, several techniues have been developed to reduce the dependence on patient compliance, such as intraoral appliances with and without skeletal anchorae. owever, even these devices can produce undesirable tippin of the maxillary molars andor loss of anterior anchorae durin distalization. In the last decades, increasin numbers of adult patients have souht orthodontic treatment and expressed a desire for esthetic and comfortable alternatives to conventional xed appliances. lear aliner therapy T was introduced to answer this reuest. In a review by ossini et al. it has been stated that maxillary molar distalization up to . mm is one of the most predictable movements with T. This hih predictability was obtained throuh combination of stain, the use of proper attachment conuration, and full-day class II elastics . in, . oz see hapters about lass II treatment and see hapters and . These results conrm what every orthodontist knows Treatment success reuires technical knowlede from the orthodontist as well as the cooperation of the patient. lass II treatments with T reuire mean treatment times of 1 to months durin which class II elastics need to be used all day from treatment beinnin until class I canine relationship has been established. orrective devices should be comfortable, provide rapid and effective treatment, and favor patient compliance with orthodontic treatment. lear aliners are comfortable and aesthetically acceptable as already discussed in the previous chapters, and reuire stron patient compliance since they are removable. The existin literature showed that the mean duration of obectively measured wear was considerably lower than stipulated wear time amon all removable appliances. urthermore, compliance was found to be better in the early staes of treatment.1 Startin from these premises, the possible combined use of aliners and other orthodontic devices aimed to optimize patient adherence to therapy reducin the time reuired to wear class II elastics has been proposed. This kind of combined approach has been named hybridization of aliner therapy. mon others, temporary anchorae devices
bone-borne hybrid approach see hapter about miniscrews and tooth-borne distalization devices are the most popular hybridization approaches in T. The application of forces in such distalizin appliances could be from buccal reion, palatal reion, or both, and they could be based on slidin mechanics or be friction free e.., in the endulum appliance.
Tooth-Borne Hybrid Approach With Distalizing Device arious types of molar distalization appliances are available and presented in the orthodontic literature, such as the endulum device, the istal et, and the arriere otion ppliance enry Schein rthodontics, arlsbad, , S. These appliances are considered easy to install and can promote distal movement of the maxillary molars without the effect of maxillary orthopedic restriction.11 owever, most of these intraoral devices show undesirable reciprocal anchorae loss in the premolars and incisors durin distal molar movement.1 urthermore, molar tippin is freuently observed in most of the cases. The istal et appliance is composed of two bilateral tubes connected to a ance appliance. bayonet wire is inserted into the linual sheath of the rst molar bands. n the tube there is a stainless steel coil sprin and a clamp. The clamp can slide toward the molar and be tihtened to compress the coil. The force exerted by the sprin beins at 1 and decreases as space is opened.1 The endulum appliance was introduced by ilers in 11 and is still one of the most used distalizin devices.1 It is a xed appliance composed of a plastic pad– contacted palatal ruae. The distalizin force is produced by beta-titanium sprins that extend from the palatal acrylic and t into linual sheaths on the molar tube, which ives reater control of these teeth.1 oth the istal et and endulum appliances produce an increase in vertical dimension due to a backward rotation of the mandible.1-1 These vertical chanes comprise a sliht openin of the mandibular plane anle about 1 deree and an increase in lower anterior facial heiht .–. mm.1 hosh and anda reported that the increase in lower anterior facial heiht was sinicantly reater in patients with hiher pretreatment mandibular plane anles. The increased lower facial heiht and mandibular plane anle could have resulted from drivin the 137
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molars back into the “wede.” These results suest that the endulum may be contraindicated in patients with excessive lower facial heiht andor minimal overbite.1 Similar results were reported for the istal et appliance.1 The maxillary molar distalization obtained with those appliances is characterized by a reat amount of molar distal tippin in averae .1 derees.1 hereas the istal et produces a labial tippin of the upper incisors as a result of the uncontrolled counterforce actin on the premaxillae, the endulum appliance showed a more controlled inclination of the upper incisors with a mild crown buccal tippin. consists of two riid bars bonded bilaterally to the maxillary canines and rst molars. The canine pad with a built-in mesial hook used for placement of intermaxillary elastics is bonded to the anterior third of the clinical crown. osteriorly, the molded pad with a ball-and-socket oint is bonded to the rst molar at the center of its clinical crown to facilitate molar derotation and distalization.1- The activation of the appliance is obtained by the use of two types of elastics the rst one bein . in, oz the second one .1 in, oz, to be used from the second month of treatment until the molar and canine class I relationships are established. lastics should be worn hours per day, chanin elastics three times per day. The principle of this appliance is similar to a cantileverbased xed appliance previously shown by anda. The author described that system as an effective way to correct molar class II in nonrowin patients. n active cantilever with information of molar tipback was applied at the upper arch, while in the lower arch the author used a multibracket xed appliance and class II elastics. The undesired effects of class II elastics were controlled by the xed appliance in lower arch and by the activation of the cantilever in upper arch. revious retrospective clinical studies demonstrated the possibility of obtainin a maxillary molar distalization between 1. and .1 mm with the mean amount of molar tippin not exceedin . derees when was used in combination with xed appliances as anchorae units on the lower arch. urthermore the treatment time had a mean duration of about to months. There is a lack of hih-uality evidence supportin or contrastin the use of . In another retrospective study in which effects were compared to other class II correction methods, showed the same results obtained with class II elastics in terms of molar distalization but in less time. ne clinically and statistically relevant effect of treatment with occurred in lower anterior facial heiht that was associated with a sinicant increase in the mandibular plane anle. roclination of the lower incisors resultin from the class II elastics mechanics was observed and resulted in a sinicant amount . derees. ll the tooth-borne appliances mentioned earlier produce some side effects that need to be controlled durin the hybrid aliner treatment. xcessive upper and lower incisor proclination could be difcult to control with aliners. ccordin to ossini et al., buccolinual tippin and torue control of upper incisors have a mean accuracy of about of the planned movement. The proclination of lower
incisors resultin from the use of could be controlled usin active aliners on the lower arch and applyin a linual radicular torue information on the lower incisors of at least derees. nother side effect that can occur usin tooth-borne distalization devices is the rotation of the occlusal plane due to the increase of the vertical dimension. hosravi et al. in their study about overbite manaement with Invisalin aliners showed that overbite correction is mostly related to anterior teeth movement without any sinicant posterior intrusion andor extrusion. s described by avera et al. bite block effect of the aliner causes an intrusive effect on posterior teeth of . mm. similar value . mm was described by antovani et al. Therefore, only the .- to .-mm bite block effect should be considered to counteract the increase of the vertical dimension produced by tooth-borne distalization devices averae increase – mm. n the basis of these considerations, tooth-borne distalization devices should be avoided in patients with excessive lower facial heiht andor minimal overbite. linicians should be aware of the existin evidence related to the limited control of posterior intrusion, overbite correction, and buccolinual inclination provided by T. Two clinical examples will be presented one in a teen patient and the second in an adult patient.
Case eport 1 DIAGNOSTIC SUMMARY 1-year-old female patient presented with molar class II malocclusion, skeletal class II, normal diverence, protrusion of upper and lower incisors, and unerupted upper left canine is. 1.1, 1., and 1.. The impaction was related to the mesialization of upper left posterior teeth with a conseuent absolute lack of space for the canine eruption. adioraphs conrmed the buccal displacement of the impacted upper canine. The patient’s main concern was lack of the upper left canine. The treatment plan was desined to obtain bodily distal movements of upper molars, premolars, canines, and frontal teeth to achieve a dental molar and canine class I, and recover the proper space for without extractions. endulum appliance was bonded on the upper arch to distalize maxillary molars i. 1.. nce the class I was overcorrected months treatment, the endulum appliance was debonded, and a new intraoral scan was made to start the aliner treatment. The aim of this second phase was to close the remainin spaces in the upper arch, to recover tooth in the arch and to correct lower crowdin. The same day temporary thermoformed retainers were provided to the patient. set of Invisalin aliners was produced to complete the distalization movements on the upper arch and to correct the lower arch mild crowdin. liner chane was planned every week. urin the aliner phase the patient was educated to wear class II elastics . in, . oz bilaterally to reinforce anterior anchorae while distalizin premolars. To anchor class II elastics, buttons were bonded
12 • The Hybrid Approach in Class II Malocclusions Treatment
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Fig. 12.1 Case 1. Etraoral pictures before treatment.
on the lower rst molars, while aliner hooks were used on the upper rst premolars reion. nce enouh space was obtained, the upper left canine was surically exposed with a vestibular ©ap, and a button with stainless steel hook was bonded to the buccal surface of the crown. The tooth was then moved distally rst with
class II elastics to recover a proper position on the saittal plane i. 1.. hen was close enouh to the occlusal plane, new intraoral scans were performed to obtain a new set of 1 aliners to finalize the case is. 1., 1., and 1.. The total treatment duration was months.
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Fig. 12.2 Case 1. Intraoral pictures before treatment.
A
B Fig. 12.3 Case 1. A Panoramic ray before treatment. B ateral ray before treatment.
12 • The Hybrid Approach in Class II Malocclusions Treatment
Fig. 12.4 Case 1. Intraoral pictures at end of sagittal rst phase.
Fig. 12.5 Case 1. Intraoral pictures before additional aligner stage.
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Fig. 12.6 Case 1. Etraoral pictures at end of treatment.
Fig. 12.7 Case 1. Intraoral pictures at end of treatment.
12 • The Hybrid Approach in Class II Malocclusions Treatment
A
143
B Fig. 12.8 Case 1 A Panoramic ray at end of treatment. B ateral ray at end of treatment.
Case eport 2 DIAGNOSTIC SUMMARY -year-old male patient presented with molar class II malocclusion, skeletal class II, low mandibular plane anle, overbite, and crowdin on both upper and lower arches is. 1., 1.1, and 1.11. The patient’s main concern was the excessive upper canine buccal displacement and proclination of upper incisors. The treatment plan was made to obtain bodily distal movements of upper molars, premolars, and canines to achieve a dental molar and canine class I, center midlines, and correct crowdin on both arches. was bonded in the upper arch on both sides to correct saittal relationship on molars, bicuspids, and canines i. 1.1. In the meantime, the lower arch treatment started with a rst set of aliners to correct lower crowdin. buccal
tube was bonded on lower rst molars to allow activation of both throuh the use, for the rst month, of . in, oz elastic placed from the mesial hook of the to the mesial hook of the lower buccal tubes. rom the second month until class I molar and canine resulted, the patient used a .1 in, oz elastic with elastic chanes three times a day. liners were instructed to be chaned every weeks at that stae. nce the class I was obtained on both sides months treatment, the was debonded, and a new intraoral scan was made of the aliner treatment i. 1.1. The aim of this second phase was to close the remainin spaces in the upper arch created durin saittal correction on both sides and to complete crowdin correction in the lower arch. Throuh the same scan and a three-dimensional printin in-office procedure, one temporary thermoformed retainer was provided to the patient who was instructed to wear it day and niht.
Fig. 12.9 Case . Etraoral pictures before treatment.
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Principles and Biomechanics of Aligner Treatment
Fig. 12.10 Case . Intraoral pictures before treatment.
A
B Fig. 12.11 Case . A Panoramic ray before treatment. B ateral ray before treatment.
12 • The Hybrid Approach in Class II Malocclusions Treatment
Fig. 12.12 Case . Intraoral pictures before sagittal rst phase.
Fig. 12.13 Case . Intraoral pictures before additional aligner stage.
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Principles and Biomechanics of Aligner Treatment
set of 1 Invisalin aliners was produced to perform space closure in the upper arch and to correct the lower arch mild crowdin. liner chane was planned every week. fter 1 months of treatment, class I canine and molar resulted on both sides, midlines centered, and deep bite
improved such as upper and lower arch forms. Third molars present, the patient is currently in retention with vacuum-type retainers that are used all nihts. urin the retention period, the patient will be followed up to evaluate third molars is. 1.1, 1.1, and 1.1.
Fig. 12.14 Case . Etraoral pictures at end of treatment.
Fig. 12.15 Case . Intraoral pictures at end of treatment.
12 • The Hybrid Approach in Class II Malocclusions Treatment
147
Fig. 12.15, co’
A
B Fig. 12.16 Case . A Panoramic ray at end of treatment. B ateral ray at end of treatment.
References 1. olla , uratore , arano , et al. valuation of maxillary molar distalization with the distal et a comparison with other contemporary methods. Angle Orthod. 1-. . rec , anson , ranco , et al. Intraoral distalizer effects with conventional and skeletal anchorae a meta-analysis. Am J Orthod Dentofacial Orthop. 11-1.
. avera S, astro©orio T, arino , et al. axillary molar distalization with aliners in adult patients a multicenter retrospective study. Prog Orthod. 111. . ossini , arrini S. ereibus , et al. ontrollin orthodontic tooth movement with clear aliners. n updated systematic review reardin efcacy and efciency. J Aligner Orthod. 11-.
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. arino , astro©orio T, aher S, et al. ffectiveness of composite attachments in controllin upper-molar movement with aliners. J Clin Orthod. 11-. . ichter , anda S, Sinha , et al. ffect of behavior modication on patient compliance in orthodontics. Angle Orthod. 11-1. . ombardo , olonna , arlucci , et al. lass II subdivision correction with clear aliners usin intermaxilary elastics. Prog Orthod. 111. . edwed , iethke . otivation, acceptance and problems of invisalin patients. J Orofac Orthop. 1-1. . osvall , ields , iuchkovski , et al. ttractiveness, acceptability, and value of orthodontic appliances. Am J Orthod Dentofacial Orthop. 1.e1-e1. 1. Shah . ompliance with removable orthodontic appliances. Evid Based Dent. 111-1. 11. arano , Testa . The distal et for upper molar distalization. J Clin Orthod. 1-. 1. ntonarakis S, iliaridis S. axillary molar distalization with noncompliance intramaxillary appliances in class II malocclusion a systematic review. Angle Orthod. 11-11. 1. arano , Testa , Siciliani . The linual distalizer system. Eur J Orthod. 11-. 1. ilers . The pendulum appliance for class II noncompliance therapy. J Clin Orthod. 1-1. 1. roft , ields , Sarver . Contemporary Orthodontics. St. ouis, osby lsevier . 1. arure S, atil , eddy S, et al. The effectiveness of pendulum, -loop, and distal et distalization techniues in rowin children and its effects on anchor unit a comparative study. J Indian Soc Pedod Prev Dent. 11-. 1. yloff , arendeliler , lar , et al. istal molar movement usin the pendulum appliance. art the effects of maxillary molar root uprihtin bends. Angle Orthod. 11-.
1. haués-sensi , alra . ffects of the pendulum appliance on the dentofacial complex. J Clin Orthod. 1-. 1. yloff , arendeliler . istal molar movement usin the pendulum appliance. art 1 clinical and radioloical evaluation. Angle Orthod. 1-. . hosh , anda S. valuation of an intraoral maxillary molar distalization techniue. Am J Orthod Dentofacial Orthop. 111 -. 1. arrière . new class II distalizer. J Clinic Orthod. -1. . artel . The arriere distalizer simple and efcient. Int J Orthod Milauee. 1-. . odríuez . nilateral application of the arriere distalizer. J Clin Orthod. 111-1. . Sandifer , nlish , olville , et al. Treatment effects of the arrière distalizer usin linual arch and full xed appliances. J orld ed Orthod. 1e-e. . anda . Biomechanics in Clinical Orthodontics. Saunders 1. . in , an , uo , et al. valuatin the treatment effectiveness and efciency of arriere distalizer a cephalometric and study model comparison of class II appliances. Prog Orthod. 11. . im-erman , camara r , ints , et al. Treatment effects of the arriere otion ppliance for the correction of class II in adolescents. Angle Orthod. 1-. . hosravi , ohanim , uoel , et al. anaement of overbite with the Invisalin appliance. Am J Orthod Dentofacial Orthop. 1111-. . antovani , arrini S, oda , et al. icro computed tomoraphy evaluation of Invisalin aliner thickness homoeneity. Angle Or thod 1. doi1.1-.1. pub ahead of print. . inziner S, ehrbein , ross , et al. olar distalization with pendulum appliances in the mixed dentition effects on the position of unerupted canines and premolars. Am J Orthod Dentofacial Orthop. 1-1.
13
Aligners and Impacted Canines EDOARDO MANTOVANI, DAVID COUCHAT, TOMMASO CASTROFLORIO
Introduction Except for the third molars, the impaction of the upper canine is the most common in the permanent dentition, and its recovery is nearly always recommended. The importance of canines, both from a functional and an aesthetic point of view, is crucial to set a proper occlusion. Furthermore, possible adverse sequelae of canine impaction1 can be as follows: n
n n n
iration of the neihborin teeth and loss of arch lenth External root resorption of the neihborin teeth entierous cyst formation nfections related to partial eruption
The prevalence of upper canine impaction is ranin between . and ., dependin on the population, ae, sex, and ethnicity.- The impacted maxillary canines are more common in white populations and in female patients, with a male to female ratio of approximately 1:. mpactions are unilateral in the maority of cases, and the occurrence on the palatal side is three times hiher than on the labial side., ome systemic endocrine or infectious diseases are related with failed eruption of one or more teeth Fi. 1.1.1 They act as predisposin factors but always in conunction with a local patholoic condition, such as11: n n n n n n n n
upernumerary teeth dontomas ental anomalies ysts revious trauma Early extractions nylosis left lip and palate
These factors can be associated with impactions of every tooth and are usually related to incisors or premolars. Therefore, other causes can be identied reardin impacted canines. ince impacted upper canines have been diverted or are anulated aberrantly durin development, it has been assumed that eruption of the canine is stronly inuenced by environmental factors.1 1 The maxillary canine has the lonest path of eruption, and a lon time period is needed. This could explain the hiher percentae of inclusion compared to other teeth. The upper canine beins its development from the superior part of the maxilla. t ae years, the crown is located
in correspondence of the apex of deciduous canine, mesially inclined.1 hen the permanent incisors are erupted, the close relationship between the crown of the canine and the distal aspect of the root of lateral incisor is particularly important.1 ince the upper cuspid is one of the last teeth to reach its position, the lac of space in the arch can have a reat inuence on the prevalence of impactions, especially reardin the labial ones.1 The studies that have investiated palatal impactions pointed out the increased incidence of missin or peshaped laterals.11,1 This leads to the formation of two theories: the enetic theory and the uidance theory.,,1 oth theories share the belief that certain enetic features occur in association with the palatal displacement of maxillary canines. The riht side of any patient is enetically identical to the left side. ince many studies indicated to preponderance of unilateral canine impaction, it is reasonable to state that local factors are the prevailin elements.1 ilberman demonstrated that anomalies of the lateral incisors in patients with palatally displaced maxillary canine teeth were found to be four times that of the eneral population.1 The canine impaction has been related with abnormalities reardin the shape and lenth of the root of the lateral incisor rather than its aenesis Fi. 1.. owever, missin, small, and pe-shaped lateral incisors are three varieties of expression of a sinle enetic factor. pe-shaped or small lateral incisor on one side of the mouth and a missin on the other can be frequently seen Fi. 1.. ccordin to the uidance theory of canine impaction, these factors create a enetically determined environment in which the developin canine is deprived of its uidance, thus inuencin it to adopt an abnormal eruption path.
Early Diagnosis and Treatment tooth is impacted when it fails to erupt into the dental arch within the expected developmental window. Therefore, an early dianosis is crucial to reduce the consequent issues. alpation of the labial fornix to assess the crown of the eruptin canine is the rst clinical attempt needed to identify a possible impaction. n case of a well-mared prominence absence in the late mixed dentition, orthopantomoraphy is mandatory Fi. 1..1 The early identication sins on radioraphs of an abnormal pathway of eruption is needed to prevent canine retention and maxillary incisor root resorption. 149
150
Principles and Biomechanics of Aligner Treatment
B
A
C
D
E Fig. 13.1 (A–E) Early deciduous teeth extraction leads to loss of space and canine impaction.
The deciduous canine extraction is recommended when limited or absent resorption of its root can be detected, in class uncrowded malocclusions.1, Ericson and urol,1 to evaluate the need of primary canine extraction and its corrective effect, determined a method for detection of the permanent canines, based on the followin Fi 1.: n n
The anle of the canine and the midline axis a The distance from the cusp tip to the occlusal line d
The position sector s in the frontal view n etween the midline and the axis of the 1 n etween the axis of 1 and n etween the axis of and The success rate of early extractions will vary dependin on the position of the permanent canine on . f the crown of the permanent canine is distal to lateral incisor root axis, the primary canine extraction normalied the eruptin position of the permanent canine in 1 of the cases. n contrast, the success rate decreased to if n
13 • Aligners and Impacted Canines
A
B
C Fig. 13.2 (A–C) mall sie lateral incisors and impacted cuspids.
A
B Fig. 13.3 (A) issing lateral incisors and (B) ilateral cuspid impaction.
151
152
Principles and Biomechanics of Aligner Treatment
A
B
C Fig. 13.4 (A–C) Bac of right canine prominence in late mixeddentition patient.
A
B Fig. 13.5 (A B) The orthopantomography refers to the patient in ig. . Ericson and urol canine impaction analysis.
13 • Aligners and Impacted Canines
91%
153
64%
A
Fig. 13.6 uccess rate of early deciduous canine extraction (from Ericson and urol).
the permanent canine crown were mesial to the midline of the lateral incisor root Fi. 1.. onetti et al. demonstrated that deciduous canine and rst molar extractions are more effective as a preventive approach to promote eruption of retained maxillary permanent canines positioned palatally or centrally. n the lateral cephalometric radioraph the normal inclination of the canine compared to the perpendicular to the Franfurt plane should be about 1 derees Fi. 1.. iher values are related with increased need for orthodontic treatment. on et al., usin cone-beam computed tomoraphy T data, stated that the maxillary transverse dimension had no effect on the occurrence of . accetti demonstrated that, in cases not requirin maxillary expansion, the use of a transpalatal arch T in combination with deciduous canine extraction can be effective for the permanent canine eruption. n the contrary, there is a strict relationship between the lac of space and the labially impacted canines, in particular a transverse maxillary deciency located in the anterior portion of the dental arch. esearch usin the T approach stated that buccal canine impaction is mostly associated with anterior transverse dental and seletal deciency. ubects with unilateral or bilateral impacted maxillary canines have smaller maxillary transverse dimensions than subects without impaction.1 The effect of rapid palatal expansion as a predictor of automatic eruption has been previously demonstrated. Early treatment of impacted canines is mandatory in case of severely resorbed incisors. hen resorption process is halted, the incisors do not suffer from increased mobility or discoloration in the lon term.
B
C
Fig. 13.7 (A–C) Inclination of the canine on lateral cephalometric analysis parents of this patient refused phase treatment and upper left canine impaction occurred years later.
Late Diagnosis ianosis of upper canine impaction after the expected ae of eruption is primarily clinical, with or without the presence of the correspondin deciduous canine. Ectopic or absent canine prominence is usually detected durin the examination. The information provided by ives an overall picture but cannot determine the proper position of the canine. owever, when it is possible to identify the
154
Principles and Biomechanics of Aligner Treatment
cause of failed eruption e.., a mechanical obstacle such as odontoma, its removal can allow the tooth to erupt spontaneously. indauer, in his study usin panoramic x-ray, found that of had their cusp tip distal to the lateral incisor and remained undetected. T systems provide three-dimensional imaes and useful data for a more accurate locatin of impacted teeth. T investiations have proven to be superior in detectin root resorption compared with conventional radioraphic methods intraoral and panoramic radioraphs. The amount of resorption detected by T scannin was approximately hiher. oot resorption of the maxillary permanent incisors caused by ectopic eruption of the permanent canine has an overall prevalence of 1, with a prevalence that is four times as hih in irls as in boys. ental follicles of the ectopically eruptin canines are on averae wider than those of the normally eruptin canines. urin eruption, the follicle of the eruptin maxillary canine frequently resorbs the periodontal contours of adacent permanent teeth but not the hard tissues of the roots. esorption of neihborin permanent teeth durin maxillary canine eruption is most liely an effect of the physical contacts with active pressure durin eruption and cellular activities. The resorptive mechanism seems to be conned to the dental follicle and related to metabolic activation. an found no sinicant difference of resorption prevalence between subects with buccal and palatal impactions. The dominant predictor for resorption was contact relationship less than 1 mm.1 nother recent T study found no sinicant correlation between follicle width and the variables of ender, impaction side, and localiation of maxillary impacted canines. ther factors inuencin dianosis and treatment plannin, such as anylosis and root dilaceration, can be identied mostly on T imaes. Furthermore, T data can provide useful information about shape and sie of the impacted canine, especially if further intraarch space is required Table 1.1. ccordin to ecer, the maor reasons for failure are inadequate anchorae ., mistaen location and directional traction ., and anylosis .. There is no ae limit for orthodontic recoverin of impacted canines, but the chance of success decreases with ae. study undertaen in adult patients found . success rate of impacted maxillary canine treatment amon the adults compared with 1 amon the youner controls, even thouh the overall lenth of orthodontic treatment was similar. ll the failed canines were found in the older adult subroup . years of ae.
Treatment Planning and Orthodontic Management The main oal of every orthodontic treatment is not only the correction of malocclusion but also a ood alinment and healthy periodontal tissues. eardin impacted canines, the eruption should be in the center of the alveolar ride. urin physioloic eruption there is a fusion between eratinied iniva and reduced enamel epithelium with the formation of the unctional epithelium. hen this occurs, a proper arranement of periodontium with an adequate band of eratinied tissue, correct sulcular depth, and connective bers inserted on cementoenamel unction E can be found. f a canine erupts in the alveolar mucosa, lac of unctional epithelium may occur, leadin to further mucoinival issues Fi. 1.., Teeth erupted in a labial position can promote the thinnin of the cortical plate and the formation of bony dehiscence or fenestration. This situation is related to lac of eratinied iniva and hiher prevalence of recessions Fi. 1..1, The adequate amount of eratinied iniva has been reported as between and mm, however, thinner inival tissue is at hiher ris of inival recession development durin orthodontic movement. hen conditions do not allow achievement of the eruption with a ood periodontal
A
Table 13.1 actors Affecting Prognosis n
epth of impaction
n
ac of space in the dental arch
n
Age of the patient
n
Cooperation of the patient
B Fig. 13.8 (A B) Canine eruption in aleolar mucosa.
13 • Aligners and Impacted Canines
155
B
A
Fig. 13.9 (A B) Canine erupted laially ith lac of eratinied gingia and higher ris of recession.
support or in a reasonable treatment time, premolar substitution, retention of the primary canine, or prosthetic rehabilitation must be taen into account Fi. 1.1. ince a proper dianosis is mandatory for correct orthodontic and surical plannin, the rst issue to deal with is depth of impaction. t can be found as a soft tissue impaction, a partial intraosseous impaction, or a deep full bony impaction. method of analyin severity of impactions usin T was proposed by au. This method utilies the entire three views horiontal, vertical, and axial of a T imae. ependin on its anatomic location, the cusp tip and the root tip are each iven a number between and in taen from a pretreatment imae. The sum of the cusp tip and root tip scores in the three views dictated complexity of treatment. To obtain the eruption at the center of the alveolar ride, not only the point of eruption of the cuspid but also the path must be taen into account. irect traction is provided when relationship with adacent teeth is favorable. f not, the canine must be moved in a different direction Fi. 1.11.
A
recent classication has been proposed to cateorie maxillary impacted canines as type hih ris and type low ris. Type teeth represent a hih ris of periodontal damae on neihborin teeth, includin root resorption. They need early exposure to be pulled away from closer roots. ther teeth must not be moved until they reach a safe position. Type canines do not require immediate exposure and can be moved directly in their nal position. Therefore, combined orthoperiodontal treatment aims to uide the canine at the center of the alveolar ride in three steps: 1. nitial orthodontic phase . urical intervention . rthodontic traction and alinment sually, before the intervention, a preliminary orthodontic phase is needed to ain space in the arch with alinin and levelin. The initial orthodontic phase should provide a ood control of the archform and maintain space for the impacted canine.
B Fig. 13.10 (A–E) eep horiontal impaction may undermine the eruption ith a good periodontal support. Continued
156
Principles and Biomechanics of Aligner Treatment
C
E
A
D
Fig. 13.10, cont’d
B Fig. 13.11 (A B) ateral incisor on the eruption path of the impacted canine.
13 • Aligners and Impacted Canines
The sie of the canine should be calculated automatically usin linchec software if a contralateral canine is present. therwise a diital approximation should be made accordin to the sie of the other teeth. To avoid any ris of interference, roots of incisors and premolars close to the canine should be moved carefully. proper anchorae is needed before the surical intervention to support the orthodontic traction the use of temporary anchorae devices Ts can be helpful. im of the surical exposure is the application of a device for the traction, such as button or a mesh, as close as possible to the cusp tip the least amount of bone and eratinied tissue removal is desirable. Two methods of surical-orthodontic traction of impacted teeth can be used: the open ap and closed eruption techniques. The open technique includes surical exposure of the crown by either complete removal of bone and soft tissue directly overlyin the impacted canine or the use of an apically repositioned inival ap without startin orthodontic traction and waitin on the self-eruption. The closed technique involves elevatin a full mucoperiosteal ap, exposin the canine crown to bond an attachment, then suturin. The orthodontic traction is applied until the eruption of the tooth. assina found that open surical exposure seems to be associated with reduced treatment duration and anylosis ris over the closed technique. Furthermore the closed technique does not allow direct control of the eruption path, and the detachment of the orthodontic device may require a second surery. n the other hand, the rst intention wound healin can ensure a better postoperative course. The aim of the postsurical phase is to brin the impacted tooth into the desired position on the arch. nce the canine has been exposed, continuous liht forces – are required usin elastics or elastomeric chains. The aliner can be modied with burs or pliers to create proper hoos on which elastics or elastomeric chains can be anchored. eavy forces may cause loss of anchorae intrusion and sinicant root resorption of the adacent anchorae teeth. hen traction is provided directly by elastomeric chains, if the patient does not wear aliners adequately, unwanted forces can develop and unwanted movement of anchorae teeth can occur. The patient must wear the intraarch elastics for hours a day alon with the aliners.
Labial Impactions ince the amount of attached iniva after eruption and therefore the nal periodontal health is affected by the surical technique, labial impactions are more challenin to manae. ased on the relationship between the impacted canine heiht and the mucoinival unction , three different surical techniques are traditionally used to uncover labially impacted canines: inivectomy, apically positioned ap, and closed eruption. The inivectomy is indicated when there is a soft tissue impaction, more than a third of the crown is below the , and a proper amount of eratinied iniva about – mm is preserved above the exposed crown. The apically positioned ap is used in shallow labial impactions when most of the crown is located apically to the
157
, especially when a little amount of attached iniva is detected. minimum of mm of attached iniva should be embedded in the ap desin. The closed eruption technique is recommended when the position of the crown is coronal to the mucoinival unction, or if the labiolinual position of the impacted canine is toward the center of the alveolar ride, to avoid massive inival and bone removal. ermette et al. stated that labially impacted teeth mostly need closed eruption technique to reduce unaesthetic sequelae such as increased clinical crown lenth. n a recent split-mouth study, ee et al. found that after the closed eruption technique, impacted canines exhibited sliht but clinically insinicant periodontal recession compared with the contralateral normal tooth. ccurrence of recession is related to the root developmental stae and pretreatment depth and anle.
Palatal Impactions ccordin to ecer and ilberman1 the ideal treatment approach is from the palatal side. nitial traction should be applied in a linually downward direction to prevent interference with the neihborin teeth. recent review by arin stated that when a unilateral is exposed and alined, there is a small periodontal impact with no clinical relevance in the short term they found no difference in periodontal health when the open and closed techniques were compared. efore orthodontic treatment, the open technique involves surical exposure of the canine and the overlyin palatal tissue removal. ealin is attained by secondary intention. lare removal of bone and inival tissue can lead to a sinicative loss of clinical attachment and inival recession so that this technique should be avoided in cases of deep impaction. Furthermore, damae of the E can promote an increased ris of anylosis. The closed technique involves uncoverin the canine, attachin an eyelet and old chain, and then suturin the palatal mucosa bac over the tooth., n this case, a force is applied on the tooth to speed up the eruption. riticality of this method is the possible detachment of the orthodontic device. owever, the rst intention wound healin can lead to better periodontal and aesthetic outcomes with lower morbidity for the patient.
linical ase FIRST VISIT ate: --1 ender: ale e: 1y m
ORTHODONTI DINOSIS eletal n , ental n olar , canine nonassessible, deep bite, increased , spaces between teeth
158
Principles and Biomechanics of Aligner Treatment
Facial n Flat prole ultiple aenesis: 1, 1, , , 1, , mpacted: 1, , Fis. 1.1, 1.1, and 1.1 are provided.
. urical exposure . Final alinment
TRTNT RORSS Fis. 1.1 and 1.1 show details of the treatment proress.
TRTNT N 1. ral hyiene instructions and motivation . nterior diastemas closure and anchorae preparation
A
FIN Fis. 1.1, 1.1, and 1.1 show nal treatment results.
C
B
Fig. 13.12 (A–C) Clinical case study aseline extraoral.
A
B Fig. 13.13 (A–E) Clinical case study aseline intraoral.
13 • Aligners and Impacted Canines
C
159
D
E Fig. 13.13, cont’d
A
B Fig. 13.14 (A–) Clinical case study aseline xrays. Continued
160
Principles and Biomechanics of Aligner Treatment
C
D Fig. 13.14, cont’d
13 • Aligners and Impacted Canines
E
F Fig. 13.14, cont’d Continued
161
162
Principles and Biomechanics of Aligner Treatment
G Fig. 13.14, cont’d
A
B Fig. 13.15 (A–E) Clinical case study progression.
13 • Aligners and Impacted Canines
C
163
D
E Fig. 13.15, cont’d
A
B Fig. 13.16 (A–) Clinical case study progression. Continued
164
Principles and Biomechanics of Aligner Treatment
C
D
E
F Fig. 13.16, cont’d
A
B
C
Fig. 13.17 (A–C) Clinical case study extraoral nal.
13 • Aligners and Impacted Canines
A
B
C
D
E
Fig. 13.18 (A–E) Clinical case study intraoral nal.
165
166
Principles and Biomechanics of Aligner Treatment
A
B Fig. 13.19 (A B) Clinical case study nal xrays.
References 1. hafer , ine , evy . A Textbook of Oral Pathology. nd ed. hiladelphia: aunders 1. . achi F, owell F. survey of routine full mouth radioraphs. . study of impacted teeth. Oral Surg Oral Med Oral Pathol. 111:11-11. . acerdoti , accetti T. entoseletal features associated with unilateral or bilateral palatal displacement of maxillary canines. Angle Orthod. :-. . Ericson , urol . adioraphic assessment of maxillary canine eruption in children with clinical sins of eruption disturbance. Eur J Orthod. 1:1-1. . an , i T, v , uan , han , Tao , i , ou , uan . is factors for maxillary impacted canine-lined severe lateral incisor root resorption: cone-beam computed tomoraphy study. Am J Orthod Dentofacial Orthop. ep1:1-1. . conald F, ap . The surical exposure and application of direct traction of unerupted teeth. Am J Orthod. 1:1-. . ec , ec , ataa . The palatally displaced canine as a dental anomaly of enetic oriin. Angle Orthod. 1:-. . ooe , an . anine impactions: incidence and manaement. nt J Periodontic etoratie Dent. :-1. . oich . urical and orthodontic manaement of impacted maxillary canines. m rthod entofacial rthop. 1:-. 1. assina , apaeoriou , Eliades T. pen versus closed surical exposure for permanent impacted canines: a systematic review and meta-analyses. Eur J Orthod. 11:1-1.
11. ishara E, ommer , ceil , et al. anaement of impacted canines. Am J Orthod. 1:1-. 1. ecer , mith , ehar : The incidence of anomalous maxillary lateral incisors in relation to palatally-displaced cuspids. Angle Orthod 11:-, 11. 1. oich , athews . urical and orthodontic manaement of impacted teeth. Dent lin orth Am. 1:11-. 1. ecer , haushu . Etioloy of maxillary canine impaction: a review. Am J Orthod Dentofacial Orthop. 11:-. 1. ewel F. linical observations on the axial inclination of teeth. Am J Orthod. 1:-11. 1. van der inden F. Deelopment of the uman Dentition. uintessence 1. 1. acoby . The etioloy of maxillary canine impactions. Am J Orthod. 1:1-1. 1. iu , live , rifn , et al. axillary lateral incisor morpholoy and palatally displaced canines: a case-controlled cone-beam volumetric tomoraphy study. Am J Orthod Dentofacial Orthop. 11:-. 1. ec , ec , ataa . oncomitant occurrence of canine malposition and tooth aenesis: evidence of orofacial enetic elds. Am J Orthod Dentofacial Orthop. 1:-. . ilberman , ohen , ecer . Familial trends in palatal canines, anomalous lateral incisors, and related phenomena. Eur J Orthod. 11:1-1. 1. rin , ecer , halhav . osition of the maxillary permanent canine in relation to anomalous or missin lateral incisors: a population study. Eur J Orthod. 11:1-1.
13 • Aligners and Impacted Canines . Ericson , urol . adioraphic assessment of maxillary canine eruption in children with clinical sins of eruption disturbance. Eur J Orthod. 1:1-1. . arib , anson , aldo Tde , et al. omplications of misdianosis of maxillary canine ectopic eruption. Am J Orthod Dentofacial Orthop. 11:-. . illiams . ianosis and prevention of maxillary cuspid impaction. Angle Orthod. 1111:-. . Ericson , urol . Early treatment of palatally eruptin maxillary canines by extraction of the primary canines. Eur J Orthod. 11:-. . lessandri onetti , anarini , ncerti arenti , et al. reventive treatment of ectopically eruptin maxillary permanent canines by extraction of deciduous canines and rst molars: a randomied clinical trial. Am J Orthod Dentofacial Orthop. 111:1-. . rescini . Trattamento hirurgicoOrtodontico dei anini nclui. olona: Ed artina 1. . on , adfar , hun . elationship between the maxillary transverse dimension and palatally displaced canines: a cone-beam computed tomoraphic study. nle Orthod. 1:-. . accetti T, iler , camara r . n T on treatment of palatally displaced canines with E andor a transpalatal arch. Eur J Orthod. 11:1-. . connell T, offman , Forbes , et al. axillary canine impaction in patients with transverse maxillary deciency. ASD J Dent hild. 1:1-1. 1. an , un , Fields , et al. Etioloic factors for buccal and palatal maxillary canine impaction: a perspective based on cone-beam computed tomoraphy analyses. Am J Orthod Dentofacial Orthop. 11:-. . rboleda-ria , chillin , rriola-uillén E, et al. axillary transverse dimensions in subects with and without impacted canines: a comparative cone-beam computed tomoraphy study. Am J Orthod Dentofacial Orthop. 11:-. . eran , camara r , accetti T, et al. prospective lon-term study on the effects of rapid maxillary expansion in the early mixed dentition. Am J Orthod Dentofacial Orthop. 1:1-. . outolou , ostai . Effect of surical exposure technique, ae, and rade of impaction on anylosis of an impacted canine, and the effect of rapid palatal expansion on eruption: a prospective clinical study. Am J Orthod Dentofacial Orthop. 11:-. . ecer , haushu . on-term follow-up of severely resorbed maxillary incisors after resolution of an etioloically associated impacted canine. Am J Orthod Dentofacial Orthop. 1:-. . indauer , ubenstein , an , et al. anine impaction identied early with panoramic radioraphs. J Am Dent Aoc. 11:1-, -. . otticelli , erna , attaneo , et al. Two- versus three-dimensional imain in subects with unerupted maxillary canines. Eur J Orthod. 11:-. . erlin , Ericson . ow a computeried tomoraphy examination chaned the treatment plans of children with retained and ectopically positioned maxillary canines. Angle Orthod. 1:-1. . Ericson , urol . adioraphic examination of ectopically eruptin maxillary canines. Am J Orthod Dentofacial Orthop. 11:-. . Ericson , erlin . The dental follicle in normally and ectopically eruptin maxillary canines: a computed tomoraphy study. Angle Orthod. 11:-. 1. Ericson , erlin , Falahat . oes the canine dental follicle cause resorption of permanent incisor roots computed tomoraphic study of eruptin maxillary canines. Angle Orthod. :-1. . an , un , Fields , et al. axillary canine impaction increases root resorption ris of adacent teeth: a problem of physical proximity. Am J Orthod Dentofacial Orthop. 11:-.
167
. . aˇsuyu , ahraman F, şayan . Three-dimensional evaluation of anular, linear, and resorption features of maxillary impacted canines on cone-beam computed tomoraphy. Oral adiol. 11:-. . Evans . anaement of impacted maxillary canines. n: Eliades T, atsaros . The OrthoPerio Patient linical Eidence Therapeutic uideline. 1st ed. uintessence 1. . ecer , haushu , haushu . nalysis of failure in the treatment of impacted maxillary canines. Am J Orthod Dentofacial Orthop. 1:-. . ecer , haushu . uccess rate and duration of orthodontic treatment for adult patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop. 1:-1. . ermette E, oich , ennedy . ncoverin labially impacted teeth: apically positioned ap and closed-eruption techniques. Angle Orthod. 11:-. . rban . Orban’ Oral itology and Embryology. th ed. t ouis, : The 1. . aynard r , chsenbein . ucoinival problems, prevalence and therapy in children. J Periodontol. 1:-. . an , öe . The relationship between the width of eratinied iniva and inival health. J Periodontol. 11:-. 1. chsenbein , aynard . The problem of attached iniva in children. ASD J Dent hild. 11:-. . orman . revalence and etioloy of inival recession. J Periodontol. 1:1-. . perry T, peidel T, saacson , et al. The role of dental compensations in the orthodontic treatment of mandibular pronathism. Angle Orthod. 1:-. . iyasato , rier , Eelber . inival condition in areas of minimal and appreciable width of eratinied iniva. J lin Peri odontol. 1:-. . ennström , indhe , yman . ole of eratinied iniva for inival health. linical and histoloic study of normal and reenerated inival tissue in dos. J lin Periodontol. 11:11-. . ennström , indhe , inclair F, et al. ome periodontal tissue reactions to orthodontic tooth movement in moneys. J lin Periodontol. 11:11-1. . rescini , ieri , uti , et al. rthodontic and periodontal outcomes of treated impacted maxillary canines. Angle Orthod. :1-. . au , an , allerano , et al. novel classication system for canine impactions—the index. nt J Med obot. : 1-. . evin , ’mico . Flap desin in exposin unerupted teeth. Am J Orthod. 1:1-. . ecer , hpac , hteyer . ttachment bondin to impacted teeth at the time of surical exposure. Eur J Orthod. 11:-. 1. ee , hoi , hoi , et al. abially impacted maxillary canines after the closed eruption technique and orthodontic traction: a split-mouth comparison of periodontal recession. J Periodontol. 11:-. . ecer , ilberman . The palatally impacted canine: a new approach to treatment. Am J Orthod. 1:-. . arin , enson E, Thind , et al. pen versus closed surical exposure of canine teeth that are displaced in the roof of the mouth. ochrane Databae Syt e. 11:. . ohavi , ecer , ilberman . urical exposure, orthodontic movement, and nal tooth position as factors in periodontal breadown of treated palatally impacted canines. Am J Orthod. 11:-. . rescini , ieri , uti , et al. hort- and lon-term periodontal evaluation of impacted canines treated with a closed suricalorthodontic approach. J lin Periodontol. :-.
14
Aligner Orthodontics in Prerestorative Patients KENJI OJIMA, CHISATO DAN, and TOMMASO CASTROFLORIO
Introduction According to a recent American Association of Orthodontists statement, today one in four orthodontic patients is an adult.1 In this specic category of patients, orthodontics can be called on to treat either primary malocclusions that have not been treated before or secondary malocclusions due to orthodontic relapse or pathologic tooth migration related to periodontal disease (see Chapter 1. Advances in orthodontics have also made treatment more comfortable and less noticeable than ever for individuals of all ages. any of today’s treatment options are designed to minimie the appearance of the appliance to better t any lifestyle. Apart from the innovations in the eld, the increasing demand of orthodontic treatment from adult patients is due to an increased aareness by patients of the need for good oral health, enabling the patient to reach adulthood ith a greater number of teeth in the mouth. It also happens by the increase on esthetic reuirement from society. espite possible functional problems, many of those seeing orthodontic treatment are een to improve dental esthetics and, potentially, their uality of life regarding both functional aspects and appearance. he relative importance of esthetics in current society is understood hen analying the positive attributes associated ith physical attractiveness. any of the adults looing for orthodontic treatment have orn or abraded teeth, previous restorations, missing teeth, supraeruption and occlusal plane discrepancies, malformed teeth, collapse of the vertical dimension due to the loss of posterior teeth, and many other problems reuiring an interaction beteen orthodontics and restorative dentistry. oever, the connection beteen the to specialties is reuired for young patients hen agenesis spaces should be managed or hen the recovery of a proper smile esthetics reuires cron shape modications. Orthodontic diagnosis aims, among others, to determine the degree of harmoniation reuired to correct dental or dentomaillary disorders and to indicate hether prosthetic or restorative compensation is needed and hat form it should tae. ental professionals should alays carefully consider tooth position in prosthodontic treatment to determine hether orthodontic treatment can improve prosthodontic treatment outcomes. Controlling tooth position ith orthodontics can help the prosthodontist in creating restorations that are more stable, functional, and esthetic. 168
Space Management in the Anterior Region pace management represents the eld in hich the cooperation beteen orthodontist and prosthodontists is very common. he most freuent reason is represented by agenesis, especially of the upper lateral incisor, because of its relative high prevalence and impact on a high esthetic value area. atients ith congenitally missing maillary lateral incisors often need a challenging interdisciplinary treatment, hether canine substitution, single implants, or tooth-supported restorations are chosen. Currently, it ould be inappropriate to remove enamel and dentin to place crons on adacent teeth in patients ith dental agenesis, mainly if these individuals have no restorations or ear of their eisting teeth. In case of unilateral agenesis of the maillary lateral incisor, space closure should not be used, ecept in eceptional cases, because of subseuent esthetical and functional problems. If the treatment plan calls for opening of the edentulous spaces, implants ould be an ideal alternative for replacing the missing teeth. esearch has shon that the success rate of implants is very high. oever, maillary lateral incisor implants are challenging aesthetically. he amount of space is often small, the alveolar ridge may be decient, the papillae are occasionally short, the adacent roots could be too close, the gingival levels may be uneven, and the patient could be too young. Any of these issues could compromise the aesthetic outcome of even the nest surgical implant placement. In this approach, orthodontic treatment combines 1. unctional placement of the canine . Creation of sufcient space to accommodate a cosmetic replacement for the missing lateral incisor oring ith aligners, the functional placement of the canine reuires the use of attachments to properly control the movement of the root in the three dimensions. A good option to obtain predictable movements is alays represented by their seuentialiation. If the canine reuires distaliation, mesiodistal root tipping, and torue control, then a good suggestion is to plan distaliation steps of mm, application of mesial root tipping of at least degrees every mm of distaliation, and (only once distaliation and mesiodistal root tipping have been completed planning the root torue information.1 he control of all those movements can be achieved ith the use of rectangular and vertical attachments. If a patient is congenitally missing one maillary lateral incisor, the amount of space to accommodate a cosmetic replacement is determined by opposite lateral incisor. oever, in some patients the contralateral incisor could be peg
14 • Aligner Orthodontics in Prerestorative Patients
shaped. If this is the case, management of spaces should be performed on the basis of surrounding teeth and tissue esthetics and function. he same approach should be used hen both lateral incisors are congenitally missing. he fundamental criteria for esthetic analysis should include facial, dentogingival, and dental esthetics.11 In recent years, several computer softare programs for digital smile design ( have been introduced to clinical practice and research. hey are multiuse conceptual tools that can strengthen diagnostic vision, improve communication, and enhance treatment predictability by permitting careful analysis of the patient’s facial and dental characteristics that may have been overlooed by clinical, photographic, or diagnostic cast-based evaluation procedures.1 ith today’s implant technology, assuming a .-mm lateral incisor implant, most surgeons ould probably be comfortable placing a maillary lateral incisor implant in a patient ith an interradicular space greater than . mm, leaving at least 1 mm of alveolar bone on either side of the implant. If the interradicular space ere less than mm,
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many surgeons ould suggest orthodontic retreatment. herefore, speaing specically to minimiing the ris of root movement during retention that ould impede implant placement, Olsen and oich1 recommend leaving etra space for the surgeon (i.e., a minimum of . mm beteen the crons and . mm beteen the roots. his correlates ell ith the space traditionally suggested for implant placement of 1 mm on either side of the implant.
Case Study A -year-old female presented ith the chief complaint of an unaesthetic lateral prole due to protruded upper teeth, in addition to loer dental croding. he had a short face, an acute nasolabial angle, a mildly conve prole, and lip incompetence, ith class I canine and molar relationships and signicant overet and overbite (ig. 1.1. urthermore multiple restorations ere present. he panoramic radiograph conrmed that 1. as missing (ig. 1..
Fig. 14.1 Initial intraoral pictures showing multiple restorations.
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Fig. 14.2 Initial orthopantomograms.
his patient did not ish to change her facial esthetics but to merely improve the appearance of her anterior teeth. herefore the goals of esthetic interdisciplinary treatment ere to reduce the protrusive prole and obtain a class I canine occlusion, ith normal overet and overbite, by means of orthodontic treatment enhance dental esthetics and the smile line ith orthodontics and prosthetic restorations and replace the upper right lateral incisor ith an implant. rior to clear aligner treatment, the dental bridge from the upper right canine to the upper left lateral incisor as sectioned and polyvinyl siloane ( impressions ere taen. Clear aligner treatment in the upper arch as designed to intrude and retract the anterior teeth, supported by class II elastics to bonded buttons on the upper canines and loer rst molars. In the loer arch, intrusion and
proclination of the anterior teeth ere planned. A temporary resin pontic replaced the missing upper right lateral incisor during aligner treatment (igs. 1., 1., and 1.. At the conclusion of 1 months of aligner treatment, the severe overet and overbite ere improved, and the original vertical dimension as unaltered. An upper right lateral incisor implant as placed, folloed by nal esthetic restorations (igs. 1., 1., and 1..
Space Management in the Posterior Region he mesial tipping of mandibular second molars is a freuent source of reuest for orthodontic intervention by restorative dentists. Inadeuate mandibular arch length,
14 • Aligner Orthodontics in Prerestorative Patients
Fig. 14.3 Clear aligner treatment with attachments and buttons was started. The upper front xed restoration was sectioned prior the orthodontic treatment start. Class II elastics anchored on upper canines and lower rst molars were used to reinforce canine class I relationship.
Fig. 14.4 An implant was placed in . area. Continued
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Principles and Biomechanics of Aligner Treatment
Fig. 14.4, cont’d
A
B Fig. 14.5 rontal view of . implant with A and without B aligner.
Fig. 14.6 rontal view of the nal upper anterior restoration.
14 • Aligner Orthodontics in Prerestorative Patients
Fig. 14.7 inal intraoral pictures.
Fig. 14.8 inal extraoral pictures and xras. Continued
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Principles and Biomechanics of Aligner Treatment
Fig. 14.8, cont’d
ecessive teeth sie, loss of the adacent rst molar, premature eruption of the mandibular third molar, and unusually mesial eruption pathay of the second molar can also cause its partial or total impaction.1 achrisson1 stated that in case of severe mesial tipping of loer second molars, periodontal status can be aggravated, ith angular bone loss, and an apparent pocet at the mesial surface of a tipped mandibular molar. In ecessive inclination cases, overeruption of the antagonist molar ith subseuent premature contacts and occlusal interferences hamper prosthetic intervention. epositioning of the second molar eliminates pathologic condition and facilitates the placement of a prosthetic restoration. Among the limitations of aligners, severely tipped teeth (. degrees ere included.1 prighting a severe mesial tipped molar using aligners could be uite risy since the tting loss could produce a orsening of the mesial tipping. As ell described by renia,1 if the tooth is not performing the desired movement, the aligner ill surrender to the stiffer teeth and become distorted. Its gingival edges move aay from the teeth, and no force can be eerted in the gingival area hile the force is concentrated only in the occlusal part. his distortion prevents any possible couple to be developed, and no bodily movement of the tooth is possible. his occlusal force encourages intrusion that, for a severe mesial tipped molar, means orsening of its tipping. herefore hen planning, uprighting of molars ith aligners is preferable to reduce the velocity of the angular movement and to accurately control the tting of
aligners at every appointment (igs. 1. through 1.. he intrusion effect and thus the orsening of the mesial tipping could be accelerated if a large attachment has been displayed on the buccal surface of the molar and if the aligner is losing tting. Attachments are helpful especially in those cases ith rounded shape teeth but close controls in the ofce are reuired. o increase the efciency of the uprighting mechanics and to increase the stiffness of the aligner, pontics mesially to the tipped teeth should be avoided. ontics are euivalent to loops bent on an archire. hey increase elasticity and then a potential undesired distortion of the aligner if it is going to lose tting. he use of temporary anchorage devices (As can support the uprighting of severe mesially tipped molars. or this instance, cutouts should be planned on the aligner portion covering the tipped teeth to permit the placement of bonded buttons or bracets or tubes on the tooth cron, hich can be connected ith sectional mechanics or elastic moduli to As. A systematic revie indicated mandibular molar uprighting as a freuent and complicated procedure, hich reuires good anchorage control.1 ven a small amount of anchorage loss can result in aligner distortion ith adverse effects, not only on the moving tooth but also on other tooth units. he introduction of As as anchorage control auiliaries as a “game changer” in orthodontics, maing, among others as discussed in other chapters of this boo, molar uprighting easier and reliable ith aligner orthodontics.
14 • Aligner Orthodontics in Prerestorative Patients
Fig. 14.9 Initial orthopantomogram of a patient for which a prerestorative orthodontic treatment was reuired. . and . were congenitall missing. The interdisciplinar treatment plan was designed to recover a proper interarch relationship and preparing the case for future restorations on upper front teeth and in the lower arch after the uprighting of . and intrusion of overerupted ..
Fig. 14.10 Initial intraoral and ClinChec lateral views in relation to the mesial tipping of . caused b the premature loss of ..
Fig. 14.11 Initial intraoral and ClinChec occlusal views in relation to the mesial tipping of ..
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Principles and Biomechanics of Aligner Treatment
Fig. 14.12 Attachment conguration used to recover a proper alignment and leveling of the arches and the uprighting of .. Pontic was not prescribed in . area to increase the stiffness of the aligner.
Fig. 14.13 inal intraoral and ClinChec lateral views with successful uprighting of ..
Fig. 14.14 inal intraoral and ClinChec occlusal views with successful uprighting of ..
14 • Aligner Orthodontics in Prerestorative Patients
Fig. 14.15 Initial intraoral and ClinChec lateral views in relation to the overeruption of . caused b the pre mature loss of ..
Fig. 14.16 Initial intraoral and ClinChec occlusal views of the upper arch.
Fig. 14.17 Attachment conguration used to recover a proper alignment and leveling of the arches.
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Principles and Biomechanics of Aligner Treatment
Fig. 14.18 inal lateral intraoral and ClinChec views of the right side showing intrusion and leveling of . obtained with the aid of a buccal miniscrew and a segmented auxiliar arch bonded on . and . after proper modication of the aligners. Intrusion of . was planned to level gingival edge to the . one. An implant was placed in . area during the nal stages of the orthodontic treatment.
Fig. 14.19 inal intraoral and ClinChec occlusal views of the upper arch.
Fig. 14.20 inal orthopantomogram.
14 • Aligner Orthodontics in Prerestorative Patients
Management of Posterior ererupted Moars It is common for adult patients ith dental loss, particularly of molars and premolars, to have an etrusion of the antagonist. An early loss of any molar is bound to cause supraeruption of the opposing molar into the available space. Overeruption of such a molar can lead to occlusal interference and functional disturbances and cause great difculty during prosthetic reconstruction.1 Orthodontic treatment of overerupted molars has alays been considered challenging by orthodontists, even more hen considering aligner treatment. his is primary due to the great volume of these teeth and to the need for ecellent anchorage control to have the reuired forces directed through the center of resistance of the tooth. urthermore molar intrusion is one of the less predictable movements to be performed ith aligners. According to a recent paper, posterior intrusion could be taen into account ith aligners if a maimum .- to 1-mm molar intrusion has been planned.1 In these cases, the use of As along ith orthodontic biomechanics incorporated into the aligner treatment plan is used to obtain better case control hile minimiing unanted side effects. o avoid tipping of the molar that should be intruded, forces need to be applied both buccally and lingually, and interproimal spaces are reuired to obtain intrusion. herefore, hen planning the mechanics reuired to obtain intrusion of an overerupted molar ith aligners, it is important to have interproimal spaces open to permit the intrusion movement, planning interproimal reduction and controlling that at every stage of movement the tooth has no interproimal friction. Attachments should be prescribed on adacent teeth to provide anchorage (rectangular and horiontal attachments but not on the tooth reuiring intrusion. oever, if the tooth reuiring intrusion is the most distal one, then a buccal attachment should be placed. As can be of help in increasing the amount of molar intrusion over the maimum value of predictability ith aligners only (see igs. 1. through 1.. o miniimplants can be installed on each side, one buccally and another palatally, to have more controlled movement and to mae it less comple for the professional, ith more predictable results.1 or pure intrusion, a total of three miniimplants could be used in a tooth, in agreement ith accini et al. he seletal anchorage can be used connecting it to buttons bonded on the tooth cron ith elastic chains or ii coils, and, in this case, cutouts should be planned on the aligner. Another option could be represented by the use of elastic chains or other elastic modulus connecting the palatal and buccal miniscres, passing over the occlusal surface of the aligner. A nite element study investigating the use of As for molar intrusion shoed that unilateral force unleashed higher stress in root ape and higher evidence for dental tipping directed to mini-implant sites the bilateral force promoted a more homogeneous stress distribution ithout evidence of dental tipping. ilateral intrusion techniue suggested a vertical movement of intrusion and loer probability of root ape resorption.1
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Management of Patients With a History of Temporomandiuar isorders emporomandibular disorders (s are a group of musculoseletal and neuromuscular conditions involving the temporomandibular oints (s, the masticatory muscles, and associated tissues. Current understanding and evidence-based literature failed to demonstrate a relationship beteen various occlusal factors and signs and symptoms. has moved from a dental and mechanicalbased model to a biopsychosocial and medical model that integrates a host of biologic, behavioral, and social factors to the onset, maintenance, and progression of . anagement of is typically symptomatic, aimed at decreasing pain, decreasing loading on the muscles and oints, and facilitating the restoration of function and uality of life of patients. Orthodontics is generally described as neutral in that it neither causes, cures, nor mitigates . ome early case reports shoed for some patients treated ith aligners, a muscle tenderness and ear facets on their aligners. everal clinicians speculated about the ear facets concluding that aligners may have acted as occlusal splints. A more credible hypothesis is related to an adaptation mechanism involving repetitive tooth clenching. erhaps it is possible that patients are triggered to clench on the aligners to alleviate orthodontic pain. As previously reported, orthodontic pain can be reduced by repetitive cheing of gum or plastic afers during the rst hours after the appliance is activated. Aligner cheing and clenching can result in ear facets and muscle tenderness in some patients treated ith aligners. herefore it is a possibility that patients undergoing clear aligner treatment may have transient symptoms of facial muscular pain and as a result of repetitive clenching to relieve orthodontic pain. his is the reason hy aligners should not be used in patients ith active s. As a general rule, needs to be managed before starting any orthodontic treatment. reatment should address not only the physical diagnosis but also the psychologic distress and the psychosocial dysfunction. he rst stage in treatment is symptom focused and behavioral, and it includes (as determined by the problem list patient education, physiotherapy, pharmacotherapy, psychologic therapy (e.g., cognitive behavioral therapy, stress management, and self-regulatory sills, control of overuse behaviors, and intraoral appliances. Only once symptoms have been controlled and ith the aareness that s are cyclic in nature (therefore ith a proper informed consent available, an orthodontic treatment can be planned. he folloing case is helpful in eplaining a possible aligner orthodontics approach to a patient after a rst conservative phase and pain relief.
DIAGNOSIS AND TRATNT AN he reasons hy aligners could be used to move teeth orthodontically in a patient ith a history of are represented by the possibility of accurately planning the seuence of movements, thus reducing and preventing
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Principles and Biomechanics of Aligner Treatment
phases in hich premature contacts can trigger the occlusal hypervigilance of some patients and by the possibility of using the aligners as physical pro memoria to help the patient to avoid clenching and gnashing of the teeth at least during the aae part of the day. ince the possibility of involuntary clenching or gnashing to alleviate orthodontic pain has been described, the orthodontic treatment plan should consider small amounts of movement from the very early stages of treatment to reduce orthodontic pain as much as possible.
Case Study A -year-old female patient presented ith anterior open bite, shift of the loer midline and of the mandible toard the left side, canine class II on the left side, and canine class I on the right side. urthermore diastemas ere present in the loer arch, and posterior ed prosthodontic restorations ere present (ig. 1.1. he patient had a history of
ith headaches in the temple region, nec pain, and bac. All these symptoms ere controlled ith physiotherapy, cognitive behavioral therapy, and pharmacotherapy only once the pain as relieved as the treatment plan designed. he panoramic -ray highlighted the presence of interproimal spaces in the loer arch and the missing of both loer rst molars ith conseuent installation of bridges (ig. 1.. A cone-beam computed tomography (CC scan highlighted a protruded position of the right condyle (ig. 1.. he first step of the interdisciplinary treatment consisted in the substitution of the old prosthetic restorations ith provisional ones built in a stabilied mandible position thans to a repositioning splint built by the prosthodontist in centric relation (igs. 1., 1., and 1.. Once the provisional bridges ere ed, an intraoral scan as performed to start aligner treatment. he virtual treatment plan is illustrated in igs. 1. and 1.
Fig. 14.21 Initial intraoral pictures.
14 • Aligner Orthodontics in Prerestorative Patients
Fig. 14.22 Initial extraoral pictures and orthopantomogram.
Fig. 14.23 Initial conebeam computed tomograph scans highlighting the asmmetric condles position.
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Principles and Biomechanics of Aligner Treatment
Fig. 14.24 ower occlusal splint.
Fig. 14.25 Conebeam computed tomograph scans showing condle repositioning due to the splint effect.
Fig. 14.26 Acrlic provisionals used to eep the new mandible position during the orthodontic treatment.
14 • Aligner Orthodontics in Prerestorative Patients
Fig. 14.26, cont’d
Fig. 14.27 Initial stage of the ClinChec.
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Principles and Biomechanics of Aligner Treatment
Fig. 14.28 inal stage of the rst ClinChec.
A phase I treatment as planned ith aligners and concluded in months ith a -day aligner change regimen (supported by additional vibrational forces ith Acceleent Aura, OrthoAccel Inc., ellair, , A. ig. 1. illustrates the intraoral situation at the end of phase I. o complete the orthodontic treatment, the pontic sections of the loer left and right bridges ere cut and a ne intraoral scan as performed to design the biomechanics reuired for the nal phase of the
orthodontic treatment. hen aligners ere planned and a - to -day aligner change regimen as applied to close the treatment in 1 months. Additional vibrational forces ere used in this phase, too (igs. 1. and 1.1. pace for the installation of a rst molar implant as secured (igs. 1. and 1.. inal pictures sho the alignment of the midlines and the set of a functional occlusion ith good esthetic results (igs. 1. and 1..
14 • Aligner Orthodontics in Prerestorative Patients
Fig. 14.29 Intraoral pictures at the end of the rst set of aligners.
A
B Fig. 14.30 A ateral and B posteroanterior xras at the end of the rst set of aligners.
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Principles and Biomechanics of Aligner Treatment
Fig. 14.31 Intraoral pictures at the end of the second set of aligners.
Fig. 14.32 inal stage of the second ClinChec.
14 • Aligner Orthodontics in Prerestorative Patients
A
187
B Fig. 14.33 A inal orthopantomogram and B lateral xra.
Fig. 14.34 Intraoral pictures showing the lower implants and the nal prosthodontic restorations. Continued
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Principles and Biomechanics of Aligner Treatment
Fig. 14.34, cont’d
Fig. 14.35 inal extraoral pictures.
14 • Aligner Orthodontics in Prerestorative Patients
References 1. American Association of Orthodontists. Adult orthodontics. https .aaoinfo.orgadult-orthodontics. Accessed ebruary , 1. . attrass C, andy . Adult orthodontics a revie. r J Orthod. 11-. . amdan A. he relationship beteen patient, parent and clinician perceived need and normative orthodontic treatment need. Eur J Orthod. -1. . osney . An investigation some of the factors in©uencing the desire for orthodontic treatment. r J Orthod. 11-. . arrini , ossini , Castro©orio , et al. aypeople’s perceptions of frontal smile esthetics a systematic revie. A J Orthod Dentofacial Orthop. 11-. . oich , pear . uidelines for managing the orthodonticrestorative patient. ein Orthod. 1-. . anama . he lin beteen orthodontics and prosthetics. In elsen , ed. Adult Orthodontics. Chichester, lacell ub td 1. . de Avila É, de olon , de Assis ollo r , et al. ultidisciplinary approach for the aesthetic treatment of maillary lateral incisors agenesis thining about implants Oral urg Oral Med Oral Pathol Oral Radiol. 111(e-e. . oich . aillary lateral incisor implants planning ith the aid of orthodontics. Te Dent J. 1-. 1. amoto , lasalic . A customied staging procedure to improve the predictability of space closure ith seuential aligners. J Clin Orthod. 1-. 11. agne , elser . atural oral esthetics. In onded Porcelain Resto rations in the Anterior Dentition A ioietic Approach. 1st ed. unitessence ub 1-. 1. Coachman C, Calamita . igital smile design a tool for treatment planning and communication in esthetic dentistry. uintessence Dent Technol. 11-111. 1. Olsen , oich r . ostorthodontic root approimation after opening space for maillary lateral incisor implants. A J Orthod Dentofacial Orthop. 111.e1 discussion 1-1. 1. agavali-ria , mmanouilidis , apadopoulos A. andibular molar uprighting using orthodontic miniscre implants a systematic revie. Prog Orthod. 111. 1. achrisson , antleon . Optimal mechanics for mandibular molar uprighting. orld J Orthod. -.
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1. han , ing . Clinical limitations of Invisalign. J Can Dent Assoc. -. 1. renia . he clear plastic appliance a biomechanical point of vie. Angle Orthod. 1-. 1. affarel I, eira , uimarães , et al. iomechanics for orthodontic intrusion of severely etruded maillary molars for functional prosthetic rehabilitation. Case Rep Dent. 111. 1. eir . Clear aligners in orthodontic treatment. Aust Dent J. 1(suppl 1-. . accini , Cotrim-erreira A, erreira , et al. fciency of to protocols for maillary molar intrusion ith mini-implants. Dental Press J Orthod. 11-. 1. ugii , arreto C, rancisco ieira-únior , et al. truded upper rst molar intrusion comparison beteen unilateral and bilateral miniscre anchorage. Dental Press J Orthod. 1 -. . andasamy , inchuse . Orthodontics and . In andasamy , reene C, inchuse , et al., eds. TMD and Orthodontics. A Clinical Guide for the Orthodontist. pringer ub 11-. . anfredini , tellini , racco A, et al. Orthodontics is temporomandibular disorder-neutral. Angle Orthod. 1-. . oyd . sthetic orthodontic treatment using the Invisalign appliance for moderate to comple malocclusions. J Dent Educ. -. . chupp , aubrich , eumann I. Invisalign treatment of patients ith craniomandibular disorders. Int Orthod. 1-. . ran , ou , ebiolo , et al. Impact of clear aligner therapy on tooth pain and masticatory muscle soreness. J Oral Rehabil. 11-1. . ou , ran , Castro©orio , et al. valuation of masticatory muscle response to clear aligner therapy using ambulatory electromyographic recording. A J Orthod Dentofacial Orthop. 11 e-e. . Ohrbach . isability assessment in temporomandibular disorders and masticatory system rehabilitation. J Oral Rehabil. 1-. . reene C, inchuse , andasamy , et al. anagement of signs and symptoms in the orthodontic practice. In andasamy , reene C, inchuse , et al., eds. TMD and Orthodontics. A Clinical Guide for the Orthodontist. pringer ub 111-1. . iancotti A, ermano , ui , et al. A miniscre-supported intrusion auiliary for open-bite treatment ith Invisalign. J Clin Orthod. 1-.
15
Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions BENEDICT WILMES and JÖRG SCHWARZE
Upper Molar Distalization in Aligner Treatment The distalization of the upper molars may be considered as a treatment option for patients with an angle class II malocclusion characterized with an increased overjet and/or anterior crowding. There has been an increasing trend in the clinical use of purely intraoral appliances, which require minimal need for patient cooperation. nfortunately, most tooth-borne appliances for upper molar distalization produce an unwanted side effect of anchorage loss resulting in maillary incisor proclination, reported to be to of observed tooth movement. ure bodily tooth movement with sequential plastic aligner therapy is challenging to achieve to a high degree of predictability. s a consequence, molar distalization is limited when relying on aligner movement alone. hile there are limited reports of successful upper molar distalization of up to . mm in the literature, a very long treatment time and high level of patient compliance are epected with requirement for intermaillary class II elastics to be worn during the long period of the sequential upper molar distalization. oreover, the potential side effects of class II elastics must be considered in terms of mesial shift of the lower anchorage teeth. To minimize anchorage loss and need for class II elastics, mini-implants have been incorporated into the design of maillary distalization appliances. ini-implants can be positioned intraorally with minimal degrees of surgical invasiveness, are readily integrated with concomitant biomechanical initiatives, and are relatively cost effective.- arious designs of implant supported distalization appliances have been published. The retromolar region is an unsuitable area for mini-implant insertion due to the unfavorable anatomic conditions poor bone quality and thic soft tissue. dditionally, the alveolar process has also been shown to be inappropriate in cases of a desired molar distalization since the mini-implants are in the direct path of the moving teeth resulting in a failure rate that is much higher as compared to the anterior palate. Therefore, the palatal area posterior from the rugae T zone seems to be the preferred insertion site for mini-implants where the treatment objective is for distal movement of the maillary molars without associated anchorage loss and maillary incisor displacement. urthermore, good bone quality with 190
thin attached mucosa implies minimal ris of tooth-root injuries and a very high success rate in the anterior palatal region. In contrast to treatment strategies involving the interradicular positioning of mini-implants, the molar teeth can be distalized, and the premolars are free to move distally due to the stretch of the interdental bers without any interference since the palatally positioned miniimplants are not in the path of moving teeth. ithin the T zone, the mini-implants can be inserted in a median or paramedian orientation, with both insertion sites showing a similar stability.
Clinical Procedure and Rational of the Beneslider The eneslider- is a maillary molar tooth distalization appliance, principally designed on the use of one or two mini-implants coupled in a median or paramedian orientation in the anterior palate ig. .. y modifying the angulation of the .-mm stainless steel wire, it is possible to achieve a simultaneous intrusion or etrusion of the molars.- The distalization forces are transferred to the molars by the use of bonded tubes. The advantages of a bonded tube are esthetics, and the adaptability and t of the aligners is not undermined by the presence of stainless steel molar bands. The aligner material could cover this bonded connection ig. . or the aligner could be cut out in this connection area “button cutout” ig. .. It seems advantageous that the eneslider appliance can be tted directly without the requirement for adjunctive laboratory wor in terms of welding or soldering, or the need to record an intraoral impression. lternatively, the clinician has the choice to record an intraoral impression and transfer the clinical setup to a plaster cast model using an impression cap and laboratory analogue from the enet system. ollowing distalization of the maillary molar teeth, steel ligatures can be used see ig. . or springs removed see ig. . to modify the eneslider from an active distalization device to a passive molar anchorage device. The primary objective is to stabilize the maillary molar teeth during the retraction of the maillary anterior teeth. ur eperience in using the eneslider appliance in conjunction with aligners commenced with a two-phase approach
15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions
Fig. 15.1 The Beneslider appliance is based on one or two miniimplants with echangeable abutments
191
the initial phase involving molar distalization and the secondary phase for the nal detailing of the occlusion with sequential thermoplastic aligners. ith a two-phase approach, an impression or scan is recorded after distalization. To reduce the total treatment time, we now recommend simultaneous distalization with the eneslider and alignment with sequential aligners. ith a single-phase approach, the impressions for aligners are taen prior to distalization of the maillary molars, and the anticipated tooth movement to be produced by the eneslider appliance is programmed in the digital software platform. or distalization, either a sequential step-by-step distalization or an entire maillary arch can be chosen since the stretch of the interdental bers supports the simultaneous distal drift of maillary anterior teeth. If the aligner material should cover the connection area with the molars see ig. ., the impressions for aligners should be done after the insertion of the eneslider appliance. The eneslider should be not activated prior to the delivery of the aligners. If the aligners have a cutout area see ig. ., the impressions for aligners are able to be recorded either before or after insertion of the eneslider appliance. istalization forces can be applied to the rst or second maillary molar teeth. ur clinical eperiences have shown that force application to the rst molar is a superior approach, as direct force application to the second molar teeth is associated with precocious distalization of the second molars, leading to improper tracing and tting of the sequential plastic aligners, a ris that is reduced if the maillary rst molar teeth are connected to the eneslider.
Clinical Case Fig. 15.2 The aligners can coer the bonded connection lie a big attachment After distalization steel ligatures are to modif the actie Beneslider into a passie anchorage deice
Fig. 15.3 The aligners can be cut out in this connection area “button cutout” prings are remoed in this case to modif the actie Beneslider into a passie anchorage deice
-year-old female patient presented with anterior crowding class II malocclusion ig. . Table .. The maillary teeth were migrated mesially, especially on the left side. ue to the absence of the second lower right molar, the upper second right molar was elongated. The patient was very unhappy with the protrusion of the upper front teeth and specically requested an invisible orthodontic treatment option to be performed on a nonetraction basis. ollowing the insertion of two enet mini-implants in the anterior palate ig. ., the eneslider appliance was passively installed see ig. . note springs are not activated. ith the goal to distalize and intrude the upper right second molar simultaneously, the guiding wire of the eneslider was angulated apically see ig. .. econdly, intraoral scans were recorded for fabrication of clear aligners Invisalign, lign Technology, Inc.. sing the aligner planning software e.g., linhec, the molar movements have to be planned parallel to the guiding wires of the eneslider, including the intrusive vertical component in the rst quadrant. uring the distalization period, molar derotations and uprighting movements were not allowed see ig. .. In this patient, a sequential distalization was chosen. The aligner material should cover the connection area ig. .. fter delivery and insertion of the aligners, the eneslider was activated by pushing the -g iTi springs distally using the activation loc see ig. .. The maillary molars were to be distalized
192
rinciples and Biomechanics of Aligner Treatment
Fig. 15.4 A -ear-old female patient with an angle class II malocclusion characterized b anterior crowding and a deep bite
15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions
Fig. 15.4, cont’d
Tale 151 Cephalometric ummar
NBa
Pretreatment
Posttreatment
°
°
N-N
°
°
M-N
°
°
M-N
°
°
NA
°
°
NB
°
°
ANB
°
°
its
mm
mm
U-N
°
-M
°
° °
U-
°
°
eret
mm
mm
erbite
mm
mm
193
194
rinciples and Biomechanics of Aligner Treatment
A
B
C Fig. 15.5 After insertion of two Benet mini-implants in the anterior palate A and installation of the Beneslider mechanics B uperimposition of an intraoral picture of the maillar arch and the ClinChec to demonstrate desired tooth moement directions C
Fig. 15.6 Beneslider was actiated b pushing open springs distall after delier of the aligners Connection areas of the Beneslider with the molars are coered b the aligner “big attachment”
approimately to mm. The patient reportedly adapted to the appliance without issue. The panoramic radiograph denotes bodily distalization of all maillary posterior teeth after months ig. .. uring the follow-up controls, molar distalization is visible with small spaces between molars and bicuspids igs. ., ., ., and . note sequential distalization. s soon as the maillary molar teeth were distalized into an angle class I occlusion, steel ligatures were used between the bonded tube and the activation loc to deactivate the eneslider ig. . see igs. . and .. The eneslider was converted from a distalization device to a molar anchorage device. fter all spaces were closed to the distal, the eneslider was removed and scans for a renement and molar derotation were recorded. omprehensive treatment was completed after months, and the palatal mini-implants were removed without the adjunctive use of local anesthesia ig. .. pper incisors were reclined signicantly - has changed from . to
15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions
Fig. 15.7 adiographs after months of treatment rtopantomograph and lateral -ra after months of treatment
Fig. 15.8 Intraoral pictures after months
195
196
rinciples and Biomechanics of Aligner Treatment
Fig. 15.9 Intraoral pictures after months showing man small spaces due to the semiseuential distalization
Fig. 15.10 Intraoral pictures after months Molars are distalized in a Class I occlusion The Beneslider is modied into a molar anchorage deice b two steel ligatures which are deactiating the Beneslider rom this moment bicuspid canine and incisor retractions are following
15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions
Fig. 15.10, cont’d
Fig. 15.11 Intraoral pictures after months Continued
197
198
rinciples and Biomechanics of Aligner Treatment
Fig. 15.11, cont’d
Fig. 15.12 Upper arch after months All spaces were to be closed to the distal ubseuentl the Beneslider was remoed for renement
Fig. 15.13 Treatment result after months
15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions
Fig. 15.13, cont’d
199
200
rinciples and Biomechanics of Aligner Treatment
Fig. 15.14 uperimposition of before and after cephalograms -N Upper incisor retraction is signicant
. degrees ig. ., and the patient was very happy with the achieved result.
Clinical Considerations or distalization, either a sequential step-by-step distalization or an entire maillary arch can be chosen. In this case, a sequential distalization was chosen. The advantage of sequential distalization is the aligner tting is probably better because all teeth are enclosed by aligner material, and therefore bodily retractions of bicuspids and canines can be achieved easier. isadvantage is the longer treatment time, which is visible in the case shown in this chapter. ur initial approach to combine aligner therapy and the eneslider appliance involved a two-phase protocol distalization, and after distalization of the maillary molar, impression/scan and nishing with aligners. dvantages of this two-phase procedure are as follows n
n
o need for coordination of tooth movement with eneslider and aligners n epected requirement for fewer aligners to achieve treatment objectives disadvantage of the two-phase procedure is
n
n epected increased treatment time
The potential drawbac of the one-phase method is the coordination between the eneslider appliance and planned aligner tooth movements. If the distalization force and/or the rate of distal molar movement are ecessive compared to the aligner staging, the t and accuracy of the aligner may be undermined with the appearance of maillary interdental spacing. second factor to be considered is the possibility of insufcient aligner wear by the patient. If this is recognized during active treatment, the rate of distalization may be reduced or the wear time of on aligner
may be prolonged e.g., wearing each aligner for wees instead of one. The rate of the maillary molar distal movement associated with the use of a eneslider appliance is approimately . mm per month this rate of molar distalization speed should be ept in mind when determining the appropriate aligner staging linhec. The distalization force can be directly applied to the rst or second molar teeth. To achieve a maimum retention with the teeth that are to be moved distally, we recommend bonding the eneslider to the rst molar teeth instead of the second molars. If the distalization forces are applied to the second molars and the aligner tting at the second molars is not perfect, small unepected spaces can develop in between the upper rst and second molar teeth. In this situation, the distalization force must be reduced to regain aligner tting. The anterior palate has proven to be the most convenient region of the mailla for insertion of mini-implants. ince there are no roots, blood vessels, or nerves, the ris of a complication associated with the placement of a miniimplant is minimal. ven the penetration of the nasal cavity does not result in any problems. ecently, a /manufactured insertion guide was introduced asy river, arma, Italy, which facilitates safe and precise insertion of mini-implants in the anterior hard palate, availing the opportunity for the use of palatal implants to the less eperienced clinician. econdly, these insertion guides allow for the insertion of mini-implants and installation of the appliance in a single ofce visit.
Conclusions n
n
n
y using palatal mini-implants and a eneslider device, unilateral or bilateral distal tooth movement can be realized without anchorage loss and need for class II elastics. The eneslider can be easily integrated in aligner therapy by using bonded tubes on the palatal surfaces. combined, single-phase treatment approach with simultaneous distalization and alignment is possible.
References . ortini , upoli , iuntoli , et al. entoseletal effects induced by rapid molar distalization with the rst class appliance. Am J Orthod Dentofacial Orthop. - discussion -. . imon , eilig , chwarze , et al. orces and moments generated by removable thermoplastic aligners incisor torque, premolar derotation, and molar distalization. Am J Orthod Dentofacial Orthop. -. . imon , eilig , chwarze , et al. Treatment outcome and efcacy of an aligner technique—regarding incisor torque, premolar derotation and molar distalization. BMC Oral Health. . . inzinger , ulden , ildizhan , et al. nchorage efcacy of palatally-inserted miniscrews in molar distalization with a periodontally/ miniscrew-anchored distal jet. J Orofac Orthop. -. . aboud , ad , bbott , et al. earch for dar matter at ormula see tet in nal states containing an energetic photon and large missing transverse momentum with the T detector. Eur Phys J C Part Fields. . . osta , affaini , elsen . iniscrews as orthodontic anchorage a preliminary report. Int J Adult Orthodon Orthognath urg. -. . anomi . ini-implant for orthodontic anchorage. J Clin Orthod. -.
15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions
. elsen , osta . Immediate loading of implants used for orthodontic anchorage. Clin Orthod es. -. . udwig , lasl , owman , et al. natomical guidelines for miniscrew insertion palatal sites. J Clin Orthod. -. . ourfar , ister , anavais , et al. Inªuence of interradicular and palatal placement of orthodontic mini-implants on the success survival rate. Head Face Med. . . ilmes , udwig , asudavan , et al. The T-zone median vs. paramedian insertion of palatal mini-implants. J Clin Orthod. -. . ienemper , auls , udwig , et al. tability of paramedian inserted palatal mini-implants at the initial healing period a controlled clinical study. Clin Oral Implants es. -. . ilmes , rescher . miniscrew system with interchangeable abutments. J Clin Orthod. - quiz . . ilmes , rescher , ienemper . miniplate system for improved stability of seletal anchorage. J Clin Orthod. -.
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. ilmes , rescher . pplication and effectiveness of the eneslider molar distalization device. orld J Orthod. -. . ilmes , ienemper , udwig , et al. sthetic class II treatment with the eneslider and aligners. J Clin Orthod. -. . ilmes , euschulz , afar , et al. rotocols for combining the eneslider with lingual appliances in class II treatment. J Clin Orthod. -. . ilmes , atyal , illmann , et al. ini-implant-anchored esialslider for simultaneous mesialisation and intrusion of upper molars in an anterior open bite case a three-year follow-up. Aust Orthod J. -. . ienemper , ilmes , auls , et al. Treatment efciency of mini-implant-borne distalization depending on age and secondmolar eruption. J Orofac Orthop. -. . e abriele , allatana , iva , et al. The easy driver for placement of palatal mini-implants and a maillary epander in a single appointment. J Clin Orthod. -.
16
Clear Aligner Orthodontic Treatment of Patients with Periodontitis TOMMASO CASTROFLORIO, EDOARDO MANTOVANI, and KAMY MALEKIAN
Malocclusions Related to Periodontal Disease There is no direct inuence between malocclusion and periodontal breakdown; however, quicker progression of periodontal disease is associated with occlusal discrepancies and is reduced by occlusal treatment.1, t has been demonstrated that in crowded areas plaque accumulation increases and, with respect to noncrowded areas, an increased number of periopathogenic species can be found. urthermore, an altered topography of the gingiva and the alveolar bone is commonly found when teeth are crowded. There is a strict relationship between crowding and periodontitis because anterior teeth migration is enhanced by periodontal disease, leading to a further crowding in lower arch, which then hinders a proper periodontal health. anavi demonstrated that deep bite is directly related to periodontal breakdown due to soft tissue impingement on the upper and lower incisors ig. 1.1. urthermore, multiple types of occlusal contacts have been associated with deeper probing depths premature contacts in centric relation, posterior protrusive contacts, balancing contacts, combined working and balancing contacts, and length of slide between centric relation and centric occlusion. nother correlation was found in mesially inclined molars where the periodontal destruction was 1 greater than that found in normally inclined teeth.
Orthodontic Treatment in Patients With Periodontal Disease rthodontics is needed in combination with periodontal and prosthodontic treatment to treat patients with a secondary malocclusion or in whom there is aggravation of an eisting malocclusion related to periodontal disease. espite the high number of published articles, there is still a lack of good evidence about many of the treatments, including orthodontics and periodontal therapy.1 The prevalence of pathologic tooth migration T among periodontal patients has been reported to range from . to .; periodontal bone loss appears to be the maor factor in the etiology of T.11 n a recent study, horshidi et al. found that pathologic migration prevalence was 11. 1 patients; however, there was no pathologic migration in patients with mild chronic periodontitis. T prevalence is increased by the severity of periodontal disease, and no statistically signicant difference between males and females was found.1 202
n early stages of T, spontaneous correction of migrated teeth sometimes occurs after periodontal therapy. hen only a light degree of pathologic migration is considered, it has been hypothesied that this is due to wound contraction during healing ig. 1..1 oft tissue forces of the tongue, cheeks, and lips are known to cause tooth movement and in some situations can cause T. The transseptal bers play a key role in T by forming a chain from tooth to tooth and helping maintain contacts between teeth. f the continuity of the chain is weakened by periodontal disease, the balance of forces is upset, and displacement of the teeth can occur ig. 1.. cclusal factors such as posterior bite collapse, shortened dental arches, occlusal interferences, and bruism are connected to the etiology of T. atients with periodontal issues are commonly characteried by general aring with spacing between the upper incisors, deepening of the bite sometimes etrusion of a single tooth can occur, increased overet, and crowding in the lower incisor region.1 nterposition of the lower lip behind the ared incisors can worsen the situation. n orthodontic treatment provided without a proper oral hygiene can result in iatrogenic damages oving a tooth into an infected infrabony defect can enhance the destruction of connective tissue.1 owever, a combined ortho-perio treatment is efcient in the treatment of periodontitis and could effectively decrease the levels of inammatory cytokines.1 urthermore, the treatment should aim for the patient’s epectations and aesthetic goals. rthodontic treatment can allow the optimiation of clinical situations1 such as n n n
eveling of bone peaks ringing a tooth back to the alveolar ridge mplant site preparation
rthodontic treatment is indicated when the worsening of periodontal status can be promoted by tooth malposition such as n n n
n
n
n
evere tooth crowding remature contacts evere deep bite associated with direct trauma on periodontal tissues esial inclination of molars associated with angular bony defect rthodontic treatment is mandatory when The periodontal disease has caused T and abnormal tooth mobility. previous orthodontic therapy made with unskillfulness has created further periodontal tissue damage.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
Fig. 16.1 Pathologic tooth migration in an old man.
203
204
Principles and Biomechanics of Aligner Treatment
A
Granulation tissue Gingival enlargement Upper lip
B Tongue
Mastication Occlusal forces Lower lip
C
Habits Fig. 16.2 Pathologic tooth migration in a young woman. (A) Intraoral picture highlighting the tissue breadown. (B) traoral picture (please note the position of element .). (C) cheme representing tissue breadown. (rom Brunsold A. Pathologic tooth migration. Periodontol. . doi.op.....)
A
B Fig. 16.3 Transseptal bers balance loss and pathologic tooth migration. (A) Scheme from Brnod MA ahooc ooh mraon (B) Occa e of he aen of re J Periodontol do o)
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
Preliminary discussion
Introduce complexity
Interest?
Comprehension Biology Risk benefit Cost
Therapeutic diagnosis
Hygiene response Control phase Compliance
205
between specialists is mandatory, and roundtable discussion is required to discuss complicated cases.1
PERIODONTAL ASSESSMENT ain concept orthodontic tooth movement without preeisting inammation. eriodontitis is characteried by microbially associated, host-mediated inammation that results in loss of periodontal attachment. The bacterial biolm formation initiates gingival inammation and promotes tissue breakdown Tables 1.1 and 1.. The primary goal is to eliminate periodontal disease and stabilie the dentition. The clinical and radiologic assessments of the periodontal situation are mandatory before treatment planning. ssessment also enables the identication of recessions, horiontal bone loss, and lesions such as crater defects one-, two-, and three-wall defects and furcation defects. imiting factors are
Interdisciplinary consultations Fig. 16.4 Preliminary ealuation of an orthoperio patient. (From Nanda R Esthetics and Biomechanics in Orthodontics nd ed S Lo, MO Eeer )
n n n
Diagnosis and Treatment Planning
n n
eriodontal pockets . mm laque inde and bleeding on probing .1 Thin-scalloped gingival biotype iabetes out of control moking .1day evere tooth mobility
PATIENT EXPECTATIONS
n
very careful consideration of the patient’s chief complaint is due in order to clearly determine the patient’s needs and plan realistic treatment goals.1 These obectives generally should be economically, occlusally, periodontally, and restoratively realistic.1 The preliminary periodontal assessment is a fundamental screening process during which adherence to issues of home oral hygiene and regular appointment attendance is determined ig. 1..1
rior to orthodontic treatment, the following can be performed
MULTIDISCIPLINARY TEAM ince several skills and knowledge are needed to provide full treatment planning, in addition to a periodontist and an orthodontist, a restorative dentist, prosthodontist, and oral or maillofacial surgeon can be involved. The importance of the team approach in achieving the best possible results in the management of adult orthodontic patients with bone loss cannot be overstated. n this phase, good communication
n n n n n n
ral hygiene motivation rophylais or therapy to control inammation urgery to eliminate deep pockets ugmentation of attached gingiva renectomy limination of gingival clefts
t is mandatory that the orthodontist and periodontist discuss the management of periodontal issues and plan the correction. atients with a malocclusion may present with preeisting mucogingival problems or fragile periodontal support that is susceptible to attachment loss during or after orthodontic treatment ig. 1.. proper amount of attached gingiva is needed to dissipate the mechanical trauma induced by mastication and tooth brushing. f teeth are inside the alveolar ridge, predictable soft tissue grafting
Table 16.1 ramewor for taging and rading of Periodontitis IA IT A COPIT O AAT
Stage I: Initial Periodontitis idence or ris of rapid progression anticipated treat ment response and effects on systemic health
Stage II: Moderate Periodontitis
Stage III: Seere Periodontitis With Potential or dditional Tooth oss
rade A rade B rade C
Indiidual Stage and rade ssignment
Stage I: danced Periodontitis With tensie Tooth oss and Potential or oss o Dentition
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Principles and Biomechanics of Aligner Treatment
Table 16. Periodontitis tage PRIODOTITIS ST Seerit
omleit
Stage I
Stage II
Stage III
Stage I
Interdental at site o greatest loss
– mm
– mm
mm
mm
Radiograhic bone loss
Coronal third (,)
Coronal third (–)
tending to midthird of root and beyond
tending to midthird of root and beyond
Tooth loss
o tooth loss due to periodontitis
Tooth loss due to periodontitis # teeth
Tooth loss due to periodontitis of teeth
ocal
aimum probing # mm ostly horiontal bone loss
In addition to stage II compleity Probing depth mm ertical bone loss mm urcation inolement class II and III oderate ridge defect
In addition to stage III compleity eed for comple rehabilitation due to asticatory dysfunction econdary occlusal trauma (tooth mobility ) eere ridge defect
aimum probing depth # mm ostly horiontal bone loss
Bite collapse drifting ¤aring , remaining teeth ( opposing pairs) tent and Distribution
dd to stage as descritor
or each stage describe etent as localied (, of teeth inoled) generalied or molarincisor patter
CAL, Cnca aachmen ee
Fig. 16.5 In this class II adult patient incisors are crowded etruded and proclined. oft and hard tissue grafting can be helpful before orthodontic treatment to preent the deelopment of recessions.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
207
Fig. 16.5, c’
procedures such as the subepithelial connective tissue graft T and the free gingival graft may be performed prior to tooth movement to prevent gingival recession. n a systematic review, loukos et al. investigated the indication and timing of soft tissue augmentation in orthodontic patients. o randomied controlled trial was identied, and only limited data were available. urthermore, osseous defects cannot allow many adult patients to clean teeth adequately and require correction prior to or during orthodontic therapy. These osseous defects include interproimal craters; one-, two-, and three-wall defects; furcation defects; and horiontal defects. nterproimal craters are two-wall defects, where attachment loss occurs on the mesial and distal surfaces of the adacent roots and the remaining walls are the buccal and lingual ones. rthodontic movement cannot improve interproimal craters; if the crater is mild to moderate, then resective surgery and bone recontouring should be eecuted. n one-wall defects, there has been destruction of three of the four interproimal walls, leaving one wall remaining. These defects are difcult for a periodontist to manage because resection could be too destructive and regeneration is inappropriate. rthodontic eruption of the tooth can eliminate the defect associated with occlusal reduction.
Three-wall defects must be treated prior to orthodontics with regenerative therapy. provisional splinting of the teeth undergoing periodontal surgery is needed to provide stabiliation. occuo et al. demonstrated that the enamel matri derivative alone and in association with various grafts give the best results for the treatment of intrabony defects, with improvements in terms of clinical attachment level gain and pocket depth reduction. n this study, the orthodontic treatment was initiated to 1 months after guided tissue regeneration T procedures and aimed at correcting malposition, creating contact points, and providing nontraumatic occlusion. ince the broblastic and osteoblastic turnover is necessary to heal the defect before moving the adacent teeth, the timing of orthodontic treatment after regenerative therapy is still debated.- an et al. recommended waiting to begin orthodontic therapy until at least months after the completion of periodontal regenerative therapy to carry out the movement in fully healed sites. urcation defects are typically divided into three classications class 1, , or . lass 1 furcation defects are usually monitored during orthodontic therapy. lass and furcation defects should be treated by the periodontist before the orthodontic treatment to allow a proper hygiene.
20
Principles and Biomechanics of Aligner Treatment
ometimes, if the periodontal health of adacent teeth can be maintained, hopeless teeth are used during orthodontic treatment to provide anchorage and occlusal function for the patient. The orthodontist must evaluate the horiontal bone loss because there is an alteration of crownroot ratios. f horiontal bone loss has occurred in only one area, reduction of crown length will avoid the creation of bony defects between adacent teeth after leveling. uring orthodontic treatment, the following can be performed n
n
n
rophylais and plaque removal every month to control inammation urgical eposure of impacted teeth according to periodontal concepts ibrotomy every 1 days during forced eruption
fter orthodontic treatment, the following can be performed n n n n
upportive therapy linical crown lengthening ingivoplasty oot coverage
ORTODONTIC ASSESSMENT DETERMINATION OF FINAL OCCLUSION ental history in adult patients should not be overlooked and, along with restorative requirements, is a key factor in determining the nal occlusion. specic evaluation of parafunctional habits, temporomandibular disorders, cracked teeth, and wear facets is mandatory Table 1.. articular focus is on the following n n
n n
Tooth movements within bone limits val-shaped roots buccolingual dimension wider than the mesiodistal dimension resence of fremitus valuation of tongue pressure
CONSIDERATIONS n n
valuate teeth with intact or reduced periodontal support. revent plaque buildup avoid ed appliances.
Table 16. Orthodontic oements And alocclusion eatures Issues
oals
Crowding
Alignment
laring
Closure of diastemas and retraction intrusion
Blac triangles
eshaping by interproimal reduction retraction intrusion
Bone peas and gingial margins need leeling
Intrusionetrusion
emoal of occlusal interference
etraction and intrusion selectie grinding
ornlost teeth
Prosthetic rehabilitationspace closure
Preention of relapse
etention
n n
void ecessive ridge epansion. void ecessive proclination.
very orthodontic tooth movement beyond the cortical plate should be avoided. ingival recessions can be related to ecessive epansions and movements outside the alveolar bone housing i.e., when an alveolar bone dehiscence has been created ig. 1.. anarsdall suggested that patients with a transverse skeletal maillomandibular discrepancy greater than mm are susceptible to recessions, especially if palatal epansion is needed. ith the introduction of three-dimensional imaging in orthodontics, a diagnosis in three planes of space can be obtained with relative ease and minimal radiation. n a recent study on adolescent patients, an evaluation using cone-beam computed tomography T scans before and after orthodontic alignment stated that bone thickness T decreased and height from the cementoenamel unction to the alveolar crest increased signicantly for the incisors and mesiobuccal root of the rst molars. rch dimensions generally increased together with tipping, and epansion related to alignment resulted in horiontal and vertical bone loss at the incisors and mesiobuccal root of the rst molars. Thinner Ts and more severe crowding before treatment increased the risk for buccal bone loss. s etraction may worsen the soft tissue prole, especially in adult patients, protraction of the lower incisors is an alternative dealing with cases of lower crowding or increased overet. benecial effect on the soft tissue prole through smoothing of the mentolabial sulcus can be achieved, but the optimal position of the lower incisors is still not clear. o association between proclination and gingival recession has been found by rtun and robéty, while others consider lower incisor proclination a risk. iedrich stated that the specic anatomy must be taken into consideration, such as the gingival health and the force system. The morphology of mandibular anterior alveolus differs in hypodivergent, hyperdivergent, and norm divergent patients, but the evaluation of symphysis morphology on cephalometric radiographs might not be a solid method aimed at predicting gingival recession in the anterior region of the mandible. The relationship between periodontal status of mandibular incisors and selected cephalometric parameters has recently been investigated the width of keratinied gingiva T was found to correlate with , T, and symphysis length, while gingival thickness T was associated with T and symphysis length. oth T and T are regarded as signicant risk factors for gingival recession. n a recent study, no higher occurrence of gingival recession in cases of pronounced proclination of lower incisors without violating the osseous envelope of the alveolar process has been found. t can be speculated that if the gingiva maintains appropriate thickness, it is more resistant and less affected by tension from large proclination.1 n a retrospective study, elsen found that gingival recession on mandibular incisors was not signicantly increased during orthodontic treatment. Thin gingival biotype, visual plaque, and inammation are useful predictors of gingival recession.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
20
Fig. 16.6 In this adult patient a preious ecessie orthodontic epansion promoted a gingial recession on teeth and . The occlusal instability has led to orthodontic relapse.
Teeth can be moved with their surrounding periodontium when careful attention is paid to local anatomy and periodontal health. urthermore, tooth movement with or through bone can be provided using different force systems. hen an optimal oral hygiene has been achieved, it is possible to apply orthodontic forces, even if the periodontal tissue has reduced connective tissue attachment and alveolar bone height., Traditional ed orthodontic appliances induce microbial changes toward periodontopathogenic anaerobic bacteria because of the increased plaque accumulation. These effects are normalied after removal of orthodontic appliances without lasting detrimental effects, but in some patients there is a signicant risk for irreversible periodontal destruction. Thus the use of clear aligners that promote a better periodontal health when compared to ed appliances- may be the optimal choice in patients with periodontal involvement. ith clear aligners, it is possible for good control of oral hygiene throughout treatment, while the rst months with ed appliances are always difcult to manage.1 The forces and moments generated by aligners of the nvisalign system are always within the range of orthodontic forces. The forces and couples delivered by aligners are determined by the shape of the crown and the type and amount of displacement of the particular tooth and therefore the contacts between tooth and the inner surface of the appliance. Tipping movement is predictable with
thermoplastic appliances, but difculties about root control have been reported. ince the gingival margin of the aligner is elastic, it is not surprising that an aligner would have difculty controlling the forces applied in this region. The introduction of ower idges demonstrates that when a torque correction of about 1 degrees is required, torque loss is negligible. The force couple generated by a thermoplastic aligner torquing an upper incisor consists of a tipping force near the gingival margin and a resulting force produced by movement of the tooth against the opposite inner surface of the appliance, near the incisal edge. The undesirable mesial movement of rst molar compensation requires programmed forward mesial root rotation, in effect producing crown tipback rotation. n an in vitro study, imon et al. investigated the influence of auiliaries, such as attachments and ower idges, on performing root movements of upper central incisor torque. loss of torque up to must be considered; however, it must be noted that the efficacy of fied orthodontic appliances does not reach 1 either. onventional orthodontic brackets and wires do not completely fill the bracket slots so that the wire is able to twist, leading to a loss of moment known as torque play. The loss of torque between an arch of .1 3 . in. section usual sie for the final stages of orthodontic treatment and a . 3 . in. slot is about 1 degrees.
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Principles and Biomechanics of Aligner Treatment
more recent study stated that nvisalign is able to achieve predicted tooth positions with high accuracy in nonetraction cases. ombardo et al. stated that some tooth movements can be achieved with aligners more easily than others. n particular, vestibulolingual tipping and rotation reached . and . of the prescribed movement, respectively. n a retrospective study, fondrini et al. found no differences between aligners and brackets about buccolingual inclination control on upper incisors. These studies led to different conclusions probably because of the development and improvements in materials, technologies, and treatment protocols. everal factors are involved in determining successful tooth movement the attachment’s shape and position, the aligner’s material and thickness, the amount of activation present in each aligner, and the techniques used for the production of the aligners. Treatment outcomes depend also on the patient’s characteristics, bone density and morphology, crown and root morphology of teeth, as well as on factors related to the clinician such as the accuracy in performing the requested amount of interproimal reduction , which is usually underestimated. The plastic foil used for the fabrication is thinned out by thermoforming at the gingival edge of the aligners, thus representing the area where they are less rigid. urthermore, to avoid loss of anchorage, simultaneous movement of multiple teeth should not be performed. lanning clear aligner therapy T with virtual setup software facilitates choosing an appropriate number of anchor teeth and the proper sequence of tooth movement to minimie the risk of anchorage loss.1 owever, an aligner alone cannot provide proper anchorage control, especially in situations in which tooth morphology is not favorable i.e., small clinical crowns, reduced undercuts. To overcome clear aligner limitations, the development of effective attachments rectangular and vertical, for both anchorage management and better root control, is increasing. The use of conventional bulk-ll resins for the attachment creation leads to a higher precision. The planning, especially when associated with T data, can allow a proper control; moreover, the velocity of movements can be selectively slow .1 mm g1 days. T eamination is useful to evaluate the spatial position of the teeth within bone. They may be positioned off-ais and present radiographically with fenestrations and dehiscences. nticipated orthodontic treatment can improve tooth position in the bone so that mucogingival deciencies can be subsequently reevaluated ig. 1.. n periodontal patients there is interproimal bone loss, and the periodontal obectives are more valuable than the occlusal ones. The role of the orthodontist should be leveling the bone peaks. The marginal ridges are not always helpful for positioning the posterior teeth. f they are worn or abraded, it is more important to nd the best position to facilitate restoration. Tooth shape is another factor with great importance in treatment planning. n the maority of patients, we nd three main tooth shapes rectangular, triangular, and barrel-shaped teeth. specially when the crown has a triangular shape, the distance between the bone crest and the contact point is relatively large, and the interproimal papilla tends to be absent. Tarnow demonstrated that the papilla is present in 1 of cases when the distance from
the contact point to the interdental bone crest is mm or less. ince adults have narrower pulp chambers, can be performed and black triangles closed ig. 1..
Orthodontic Moements ith a healthy periodontal tissue, the supracrestal bers control the etrusive component of forces applicated horiontally to teeth. hen the bone support is reduced, forces are distributed over a smaller area, and the resistance to etrusion is lower. urthermore, the center of resistance of a periodontally involved tooth is shifted apically because of the bone resorption. That is why occlusal forces induce tipping and etrusion of the incisors. hen planning the orthodontic treatment, the apical displacement of the center of resistance should be taken into account, and the moment-to-force ratio therefore must be adapted to the individual situation igs. 1. and 1.1. To provide a uniform loading on periodontal ligament, translation and controlled tipping movements should be preferred. The orthodontic treatment with clear aligners in periodontal patients should be similar to the segmented arch approach. The active and reactive units should be identied and force delivery planned .
OPTIMAL CONTROL OF IOMECANICS n n n n n n
se of light forces enter of resistance void roundtrip low movements elective movements eed for further anchorage implants, temporary anchorage devices Ts free anchorage lost teeth
Taking the tooth long ais as a reference, three kinds of movement can be performed.
Mii M esiodistal movements are mainly used to close diastemas and eliminate the black triangles, after providing and the creation of a surface of contact. pace opening for implant placement is a predictable movement that can be carried out both in anterior and posterior regions. urgical bone augmentation could be needed at the end of orthodontics due to high interindividual variability of neoformed bone thickness. mesially inclined molar is not a cause of periodontal disease itself; however, molars uprighting alone can be performed to achieve root parallelism before implant placement. n presence of an infraosseous defect, T should be eecuted prior to orthodontics. strict control of oral hygiene on the distal side of an uprighting tooth is mandatory to avoid subgingival plaque formation. dditional anchorage using miniscrews may be needed in case of tricky malpositions. The mesialiation of molars is a translation movement that can be performed using light forces ig. 1.11; however, considering the high risk of complications such as bone fenestration, bone loss, and radicular resorption, it should be managed carefully.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
Fig. 16.7 Orthodontic relapse in a young patient teeth and are located outside the buccal bone. The twisted retainer prob ably not passie allowed a radicular torue moement on tooth that promoted a gingial recession with lac of adherent gingia.
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Principles and Biomechanics of Aligner Treatment
Fig. 16. ifferent tooth shapes. (From Nanda R Esthetics and Biomechanics in Orthodontics nd ed S Lo, MO Eeer )
Fig. 16. Center of resistance ariation in case of bone loss. (From Nanda R Esthetics and Biomechanics in Orthodontics nd ed S Lo, MO Eeer )
Fig. 16.10 In this patient a stainless steel powerarm has been bonded to tooth and retraction has been performed using maimum anchorage.
Fig. 16.11 esialiation of lower third molars.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
iig M estibulolingual movements are needed to position teeth inside the alveolar bone. fter a proper evaluation of bone thickness, typical localied recessions on incisors can be improved through retraction of teeth within the alveolar walls.1 The most effective movements, translation and lingual root torque, must be carried out on lower incisors only after a previous evaluation of mandibular symphyseal dimensions height, depth, and angle. rthodontics can be subsequently followed by mucogingival surgery for complete root covering. n selected cases, bodily movements can be associated with corticotomies and bone tissue grafting to prevent further periodontal damage. n efcient torque control is also needed, in combination with intrusion, during retraction of ared incisors after pathologic tooth migration. ic M The vertical movements are the main issue in periodontal patients since they are used to restore the correct alveolar bone and gingival margin levels. oving a tooth with a vertical defect can increase the risk of further attachment loss. f intrusion is needed, the probing depth has to be reduced before orthodontics. Three-wall defects can be successfully treated with regenerative surgery followed by orthodontic intrusion. ntrusion is indicated when vital teeth are etruded, in both anterior and posterior regions. n an animal study, elsen demonstrated that intrusion can improve the quantity of new attachment if carried out under healthy conditions. proper intrusive force should be to g per tooth and is affected by the periodontal support. efore providing
213
vertical movements, a correct diagnosis should take into account the presence of recession and the labial sulcular depth of the maillary incisors. f no recession has occurred, the gingival margins are used as a guide in tooth positioning. f the sulcular depth is uniformly 1 mm, the discrepancy in gingival margins may be due to uneven wear or trauma of the incisal edges ig. 1.1. Treatment for this problem is the intrusion. hen the gingival margins are aligned, the discrepancy in the incisal edges presents itself, and restoration of the short teeth can be provided. rthodontic intrusion should be planned to also properly treat lower incisors with incisal edge abrasion. These teeth typically are overerupted to maintain contact, and no space for restoration is left. ndodontic treatment and periodontal crown lengthening with bone removal are avoided by orthodontics that provides the correct restorative space. eriodontal patients are usually characteried by ared and etruded upper incisors and horiontal bone loss.11 combination of retraction and intrusion is needed, while a simple retroclination would deepen the bite. The available molars and premolars are used as anchorage units. dditional scaling and root planning every weeks are mandatory during active intrusion. espite contrasting evidence about intrusion in patients with reduced periodontal support, elsen found creation of new attachment with a consequent reduction of root to crown ratio and ardaropoli et al. demonstrated the reduction of probing pocket depth and the gain of clinical attachment after combined ortho-perio treatment of etruded teeth with infrabony defects. The use of light 1– g and continuous forces together with proper
Fig. 16.12 electie intrusion of worn teeth. (From Nanda R Esthetics and Biomechanics in Orthodontics nd ed S Lo, MO Eeer )
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Principles and Biomechanics of Aligner Treatment
torque control seems to be relevant.-1 evertheless, there can be transformation of supragingival plaque in subgingival and risk of angular defect formation. oreover, attention must be paid to root morphology, since there is a higher risk of resorption of short and pipette-shaped roots. hen a periodontally involved tooth needs prosthetic rehabilitation or the gingival margin is more apical than the others, orthodontic etrusion has a benecial effect on the bone level. trusion movements can be eecuted to level gingival margins, recover the interdental papilla, and reduce probing depth. trusion can be performed either with light or heavy forces. undamentals are direction of movement and torque control because uncontrolled tipping can lead to vestibulariation of the root. constant occlusal grinding is due to avoid premature contacts. t the end of the movement, a ed retention should be performed for at least months to prevent relapse. n case of healthy periodontium, when the crown is lost because of decay or trauma, etrusion is performed associated with brotomy every 1 days or followed by surgical crown lengthening. n case of attachment loss, etrusion is eecuted to level gingival margins and reduce angular defects. llow to months for connective bers to heal after regenerative therapy. single compromised tooth can be etruded for leveling of gingival margins, providing hard and soft tissue augmentation before the implant placement. n this case, the use of light forces 1 mmmonth is recommended. f a patient is missing multiple teeth, treatment plans can eventually include placement of dental implants to have a further anchorage for the orthodontics. efore the orthodontic loading, a proper amount of time is needed for the osteointegration. Ts such as microscrews and bone plates are also effective in enhancing tooth movements without the biomechanical side effects.
FINAL FLOCART n n n
n n n n
eestablish periodontal health eriodontal reassessment f possible, regenerative andor mucogingival surgery and implant placement rthodontic treatment eriodontal maintenancesupportive therapy rthodontic retention rosthodontic naliation
Retention educed periodontal tissues are a risk factor for orthodontic relapse. n addition, the periodontally involved teeth could be signicantly mobile. The purpose of retention is to stabilie them and reduce mobility. very action that intends to prevent relapse should be performed immediately after the completion of orthodontic movement. ince the presence of retainers bonded to all anterior teeth can increase plaque accumulation and gingivitis, the use of removable retainers should be recommended when ecessive mobility is not an issue. oreover, ed retainers can produce inadvertent tooth movement, and regular observation is needed. arafunctional habits, such as onychophagia, might be involved. The orthodontic patient with periodontal involvement may be missing one or more teeth. ince pathologic tooth migration is worsened by lack of posterior occlusal support, a nal prosthetic
rehabilitation should always be planned. ed or removable prosthesis can help stabilie the remaining teeth in the arch and provide an occlusal stop for teeth in the opposing arch. cclusal splint, can be eventually used as orthodontic retention in patients with parafunctional habits, including n n
n n
emovable retainers hen mobility is ecessive n ower ed retainer -, - in case of deep bite n ntra- or etracoronal ed retainer in other setant rosthetic rehabilitation of edentulous sellae cclusal night guard
onclusions lear aligners are safer than conventional orthodontics for stable periodontal patients. ligners allow patients to have ecellent hygiene control, especially during long treatments. linheck software is a diagnostic tool that provides a virtual setup both for orthodontics and prosthodontics. t offers a precise plan control of each movement and the possibility of selective anchorage. The keys to success are based on both lifelong supportive periodontal treatment and orthodontic retention. atient adhesion to the supportive periodontal treatment is mandatory to maintain stable long-term results.1-
linical ase FIRST ISIT ate 1--1 ender ale ge y rofession mployed hief complaint leeding gums and drifting of front teeth ttitude atient is concerned about his dentition and is positive about keeping his teeth pectations atient has realistic epectations and wants to restore his dentition in health edical anamnesis eneral appraisal of patient it and healthy amily medical anamnesis ast pathologic anamnesis ypertensive ecent pathologic anamnesis one rug therapy llergies or sensitivities one abits ormer smoker who quit months back ccupation and stress level mployed in a multinational company; medium stress level ast physical eamination months back, nothing signicant ental anamnesis igs. 1.1 and 1.1 ate and reason for the last dental visit months back for bleeding gums aor dental treatments o issing teeth reason 1. caries dverse dental eperiences one istory of periodontal disease es revious periodontal treatments nly supragingival scaling ral habits one ral hygiene practices rushes twice daily with a manual toothbrush rophylais frequency nce every year T and muscles of mastication oth unremarkable
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
215
Fig. 16.13 Baseline intraoral iew.
INTRAORAL CLINICAL EXAM
Fig. 16.14 Baseline smile.
ental analysis n ngle class olar and canine class 1 n issing teeth 1. n ental malpositions 1.1 etruded and proclined n ecays one n nadequate restorations . premature contacts in centric occlusion one n cclusal trauma one n cclusal wear one orking contacts on right side 1. canine guided ig. 1.1 n alancing contacts on left side one
216
Principles and Biomechanics of Aligner Treatment
Fig. 16.15 oring contacts.
orking contacts on left side . canine guided n alancing contacts on right side one rotrusive contacts 1.1, 1. n osterior interferences ., .
n n
n n
XRAY STATUS n
n
mount of bone resorption bone loss vertical and horiontal ig. 1.1
n n
nterradicular translucencies one amina dura and periodontal ligament enlargements one eriapical pathologies one etained teeth one oot fragmentsforeign bodies one ecays one evitalied teeth one
Fig. 16.16 Baseline status.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
ASELINE PERIODONTAL CART (I. .)
Fig. 16.17 Baseline periodontal chart.
217
21
Principles and Biomechanics of Aligner Treatment
PERIODONTAL EXAMINATION . teeth . teeth with mm n # mm n – mm n mm 1 n n
PERIODONTAL REEALUATION (I. . and .) DIANOSIS eneralied chronic severe periodontitis level presence of proimal attachment loss of mm in two or more nonadacent teeth tage grade Tables 1. and 1.
Fig. 16.1 eealuation chart.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
21
A
B Fig. 16.1 (A) Toothbytooth diagnosis. (B) Toothbytooth prognosis. (From Ko V, Caon Commenar rono reed a em for ann erodona rono J Periodontol )
Table 16. tages of Periodontitis PRIODOTITIS ST
Stage I
Stage II
Stage III
Stage I
Seerit
Interdental at site o greater loss
– mm
– mm
mm or etending to the middle third of the root
mm or etending to the apical third of the root
Radiograhic bone loss
Coronal (,)
Coronal third (–)
tending to middle third
tending to the apical third
Tooth loss
o tooth loss due to periodontitis
Tooth loss due to peri odontitis of # teeth
Tooth loss due to periodonti tis of teeth
ocal
n
In addition to stage II compleity n Probing depth mm n ertical bone loss mm n urcation inolement n Class II or III moderate ridge defect
In addition to stage III compleity n eed for comple rehabili tation due to masticatory dysfunction n econdary occlusal trauma (tooth mobility degree ) n Bite collapse n rifting n laring n , remaining teeth n eere ridge defect
omleit
n
tent and Distribution
dd to stage as descritor
CAL, Cnca aachmen ee
aimum probing depth of – mm ostly horiontal bone loss
n
n
aimum probing depth – mm ostly horiontal bone loss
or each stage describe etent as localied (, of teeth inoled) generalied or molar incisor pattern
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Principles and Biomechanics of Aligner Treatment
Table 16. rades of Periodontitis
PRIODOTITIS RD Primar riteria
rade Modiers
rade Slo Rate o Progression
rade Moderate Rate o Progression
rade Raid Rate o Progression
irect eidence of progression
ongitudinal data (PA radiographs or CA loss)
idence of no loss oer years
, mm oer years
mm oer years
Indirect eidence of progression
Bone lossage
,.
.–.
..
Case phenotype
eay biolm deposits with low leel of destruction
estruction commensurate with biolm deposits
estruction eceeds epectation gien biolm deposits specic clinical patterns sugges tie of periods of rapid progression andor early onset disease lac of epected response to standard bacterial control therapies
is factors
moing
onsmoer
moer , cigarettesday
moer cigarettes day
iabetes
iabetes
ormoglycemic with or without prior diagnosis of diabetes
bAc ,. in diabetes patients
bAc . in diabetes patients
CAL, Cnca aachmen o PA, eraca HbA1c, refer o caed haemoon
PERIO TREATMENT OALS 1. . . .
ontrol of supragingival and subgingival infection , rrest of the progression of periodontitis traction of hopeless teeth
TREATMENT PLAN tiologic therapy 1. ral hygiene instructions and motivation . onsurgical therapy caling and root planing quadrant by quadrant protocol . traction of 1., ., . . hange of lling ., .
CLINICAL EXAMINATION REEALUATION (I. .) . teeth . teeth with mm n # mm 1 n – mm n mm n n
TREATMENT PLAN AFTER ETIOLOIC TERAPY n n n n
egenerative therapy 1., etraction 1., 1. egenerative surgery 1.1, 1., . traction ., mesial root resection . egenerative surgery ., .
n n
sseous resective surgery with tunnel preparation . upportive periodontal treatment
Oic lignment and space closure on upper arch I T n 1., 1., . Pi Si T very months igs. 1.1 through 1. The periodontal therapy was performed by rof. ario imetti, head of the epartment of eriodontology of the ental chool of the niversity of Torino, Torino, taly. Oic Digi (ig. .) keletal n 1, ental n olar nonassessable, canine 1, deep bite, increased , spaces between teeth and black triangles, medial line deviated acial n onve prole Scic Oci T igs. . through .) n ailla lign and intrude the teeth, close spaces, correct the midline n andible lose spaces, intrude lower incisors, correct the midline n acial esthetics mprove esthetic smile line
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
Fig. 16.20 Periodontal status and chart at reealuation.
221
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Principles and Biomechanics of Aligner Treatment
3 mm
3 mm
3 mm
3 mm
3 mm
4 mm
8 mm
3 mm
A
B
C Fig. 16.21 egeneratie therapy on tooth . (A) Bone sounding (B) incisional photos (C) ¤ap photos.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
A
B
C
D Fig. 16.22 egeneratie therapy on tooth biomaterial photos. (A) efect cleaning. (B) mdogain (s). (C) Pref el (TA). () BioOss.
Fig. 16.23 egeneratie therapy on tooth suture photos.
223
224
Principles and Biomechanics of Aligner Treatment
A
B Fig. 16.24 egeneratie therapy on incisors. (A) Incision pfotos and (B) ¤ap photos.
A
B
C
D Fig. 16.25 egeneratie therapy on incisors biomaterial photos. (A) efect cleaning. (B) mdogain (s). (C) Pref el (TA). () BioOss.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
Fig. 16.26 Osseous resectie surgery degree setant. Alternatie therapies periodontal supportie therapy conseratie surgery resectie bone surgery.
225
226
Principles and Biomechanics of Aligner Treatment
Fig. 16.27 esectie surgery bone remodeling.
Fig. 16.2 Orthodontic records.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
A
B Fig. 16.2 ClinChec beginning (A) and end (B) frontal iew.
A
B Fig. 16.30 ClinChec beginning (A) and end (B) upper arch.
A
B Fig. 16.31 ClinChec beginning (A) and end (B) lower arch.
227
22
A
Principles and Biomechanics of Aligner Treatment
B Fig. 16.32 ClinChec beginning (A) and end (B) right side.
A
B Fig. 16.33 ClinChec beginning (A) and end (B) left side.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
Fig. 16.34 nd of preprosthetic orthodontics.
Fig. 16.35 Implant . ..
22
230
Principles and Biomechanics of Aligner Treatment
Fig. 16.36 Implant placement.
Fig. 16.37 Implant placement photos.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis
A
B
C
D Fig. 16.3 Implant placement biomaterials. (A) Bony window. (B) inus membrane eleation. (C) BioOss. () BioOss and membrane positioning.
Fig. 16.3 inal orthodontic rays. Continued
231
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Principles and Biomechanics of Aligner Treatment
Fig. 16.3, c’
References 1. eiger , asserman , Thompson r , et al. elationship of occlusion and periodontal disease. . elation of classication of occlusion to periodontal status and gingival inammation. J Periodontol. 1;-. . elsen . Adult Orthodontics. 1st ed. oboken, lackwell; 1. . uckley . The relationships between malocclusion, gingival inammation, plaque and calculus. J Periodontol. 11;-. . hung , anarsdall , avalcanti , et al. omparison of microbial composition in the subgingival plaque of adult crowded versus non-crowded dental regions. Int J Adult Orthod Orthog Surg. ;11-. . iedrich . eriodontal relevance of anterior crowding. J Orofac Orthop. ;1-. . Towghi , runsvold , torey T, et al. athologic migration of anterior teeth in patients with moderate to severe periodontitis. J Periodontol. 1;-. . anavi , eisgold , ose . iologic width and its relation to periodontal biotypes. J Esthet Dent. 1;11-1. . arrel , unn . The association of occlusal contacts with the presence of increased periodontal probing depth. J Clin Periodontol. ;1-1. . eiger , asserman . elationship of occlusion and periodontal disease part -incisor inclination and periodontal status. Angle Orthod. 1;-11. 1. orbunkova , agni , rihak , et al. mpact of orthodontic treatment on periodontal tissues a narrative review of multidisciplinary literature. Int J Dent. 1;1. 11. runsvold . athologic tooth migration. J Periodontol. ;-. 1. horshidi , oaddeli , olkari , et al. The prevalence of pathologic tooth migration with respect to the severity of periodontitis. J Int Soc Prev Community Dent. 1;1-1. 1. aumet , runsvold , cahan . pontaneous repositioning of pathologically migrated teeth. J Periodontol. 1;111-11. 1. iedrich . The eleventh hour or where are our orthodontic limits ase report. J Orofac Orthop. 1;-. 1. ennström , tokland , yman , et al. eriodontal tissue response to orthodontic movement of teeth with infrabony pockets. Am J Orthod Dentofacial Orthop. 1;11-1.
1. hang , hang , hang , et al. fcacy of combined orthodontic-periodontic treatment for patients with periodontitis and its effect on inammatory cytokines a comparative study. Am J Orthod Dentofacial Orthop. 1;1-. 1. icci , imetti . Diagnosi e Terapia Parodontale. 1st ed. ho uintessence; 1-. 1. anda . Esthetics and Biomechanics in Orthodontics. nd ed. t. ouis, lsevier; 1. 1. abari , oles , unningham . ssessment of motivation and psychological characteristics of adult orthodontic patients. Am J Orthod Dentofacial Orthop. 11;1-. . ao T, u , hi , et al. ombined orthodontic-periodontal treatment in periodontal patients with anteriorly displaced incisors. Am J Orthod Dentofacial Orthop. 1;1-1. 1. athews , okich . anaging treatment for the orthodontic patient with periodontal problems. Semin Orthod. 1;11-. . Tonetti , reenwell , ornman . taging and grading of periodontitis framework and proposal of a new classication and case denition. J Periodontol. 1;11-1. . okich , pear . uidelines for managing the orthodontic restorative patient. Semin Orthod. 1;1-. . vans . guided comprehensive approach to mucogingival problems in orthodontics. Semin Orthod. 1;-. . anchit , anger , asperini . eriodontal soft tissue non-root coverage procedures practical applications from the regeneration workshop. Clin Adv Periodontics. 1;11-. . loukos , liades T, culean , et al. ndication and timing of soft tissue augmentation at maillary and mandibular incisors in orthodontic patients. systematic review. Eur J Orthod. 1; -. . okich . nhancing restorative, esthetic and periodontal results with orthodontic therapy. n chluger , oudelis , age , et al., eds. Periodontal Therapy. hiladelphia, ea and ebiger; 1 -. . ecker , ecker . Treatment of mandibular -wall intrabony defects by ap debridement and epanded polytetrauoroethylene barrier membranes long-term evaluation of treated patients. J Periodontol. 1;11-11. . occuo , archese , almasso , et al. eriodontal regeneration and orthodontic treatment of severely periodontally compromised teeth 1-year results of a prospective study. Int J Periodontics estorative Dent. 1;1-.
16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis . atarasso , orio-iciliano , lasi , et al. namel matri derivative and bone grafts for periodontal regeneration of intrabony defects. systematic review and meta-analysis. Clin Oral Investig. 1;111-1. 1. gihara , ang . eriodontal regeneration with or without limited orthodontics for the treatment of - or -wall infrabony defects. J Periodontol. 1;111-1. . raúo , armagnola , erglundh T, et al. rthodontic movement in bone defects augmented with io-ss. n eperimental study in dogs. J Clin Periodontol. 1;1-. . an , artin . Tooth movement in the periodontally compromised patient. n ang , indhe , eds. Clinical Periodontology and Implant Dentistry. th ed. oboken, ohn iley ons; 1 vol . . ennström . ucogingival considerations in orthodontic treatment. Semin Orthod. 1;1-. . anarsdall , ecchi . eriodontal-orthodontic interrelationship. n raber , anarsdall , ig , eds. Orthodontics Current Principles and Techniues. hiladelphia, osby; 1-1. . iner , l abandi , igali , et al. one-beam computed tomography transverse analysis. art normative data. Am J Orthod Dentofacial Orthop. 1;1-. . orais , elsen , de reitas , et al. valuation of maillary buccal alveolar bone before and after orthodontic alignment without etractions a cone beam computed tomographic study. Angle Orthod. 1;-. . rtun , robéty . eriodontal status of mandibular incisors after pronounced orthodontic advancement during adolescence a followup evaluation. Am J Orthod Dentofacial Orthop. 1;111-1. . teiner , earson , inamo . hanges of the marginal periodontium as a result of labial tooth movement in monkeys. J Periodontol. 11;1-. . iedrich . uided tissue regeneration associated with orthodontic therapy. Semin Orthod. 1;-. 1. alina , adurska , obieska , et al. elationship between periodontal status of mandibular incisors and selected cephalometric parameters preliminary results. J Orofac Orthop. 1; 1-11. . elsen , llais . actors of importance for the development of dehiscences during labial movement of mandibular incisors a retrospective study of adult orthodontic patients. Am J Orthod Dentofacial Orthop. ;1-1. . elsen . iological reaction of alveolar bone to orthodontic tooth movement. Angle Orthod. 1;11-1. . rtun , rbye . The effect of orthodontic treatment on periodontal bone support in patients with advanced loss of marginal periodontium. Am J Orthod Dentofac Orthop. 1;1-1. . e , orrente , bundo , et al. rthodontic treatment in periodontally compromised patients a 1-years report. Int J Periodontics estorative Dent. ;1-. . Thornberg , iolo , ayirli , et al. eriodontal pathogen levels in adolescents before, during, and after ed orthodontic appliance therapy. Am J Orthod Dentofacial Orthop. ;11-. . omes , arela , da eiga , et al. eriodontal conditions in subects following orthodontic therapy. preliminary study. Eur J Orthod. ;-1. . ossini , arrini , astroorio T, et al. eriodontal health during clear aligners treatment a systematic review. Eur J Orthod. 1;-. . aripour , eusmann , ahmoodi , et al. races versus nvisalign gingival parameters and patients’ satisfaction during treatment a cross-sectional study. BC Oral ealth. 1;; 1. . bbate , aria , ontanari , et al. eriodontal health in teenagers treated with removable aligners and ed orthodontic appliances. J Orofac Orthop. 1;-. 1. hhibber , garwal , adav , et al. hich orthodontic appliance is best for oral hygiene randomied clinical trial. Am J Orthod Dentofacial Orthop. 1;11-1. . imon , eilig , chware , et al. orces and moments generated by removable thermoplastic aligners incisor torque, premolar derotation, and molar distaliation. Am J Orthod Dentofacial Orthop. 1;1-. . ahn , apf , athe , et al. Torquing an upper central incisor with aligners—acting forces and biomechanical principles. Eur J Orthod. 1;-1.
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. astroorio T, arino , aaro , et al. pper-incisor root control with nvisalign appliances. J Clin Orthod. 1; -1. . owman , elena , paraga , et al. reative aduncts for clear aligners, part etraction and interdisciplinary treatment. J Clin Orthod. 1;-. . imon , eilig , chware , et al. Treatment outcome and efcacy of an aligner technique—regarding incisor torque, premolar derotation and molar distaliation. BC Oral ealth. 1;1. . rünheid T, oh , arson . ow accurate is nvisalign in nonetraction cases re predicted tooth positions achieved Angle Orthod. 1;-1. . ombardo , rreghini , amina , et al. redictability of orthodontic movement with orthodontic aligners a retrospective study. Prog Orthod. 1;1;11. . fondrini , andini , astroorio T, et al. uccolingual inclination control of upper central incisors of aligners a comparison with conventional and self-ligating brackets. Biomed es Int. 1;111. . Tepedino , aoloni , oa , et al. ovement of anterior teeth using clear aligners a three-dimensional, retrospective evaluation. Prog Orthod. 1;11. 1. antovani , astroorio , ossini , et al. canning electron microscopy evaluation of aligner t on teeth. Angle Orthod. 1; -1. . antovani , astroorio , ossini , et al. canning electron microscopy analysis of aligner tting on anchorage attachments. J Orofac Orthop. 1;-. . atsaros , ivas , enkema . nepected complications of bonded mandibular lingual retainers. Am J Orthod Dentofacial Orthop. ;1-1. . Tarnow , agner , letcher . The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproimal dental papilla. J Periodontol. 1;1 -. . erna , assarelli T. rthodontic mechanics in patient with periodontal disease. n liades T, atsaros , eds. The OrthoPerio Patient. atavia, uintessence; 11. . achrisson , indhe . rthodontics and periodontics tooth movements in the periodontally compromised patient. n indhe , ed. Clinical Periodontology and Implant Therapy. th ed. iley lackwell; 11-1. . pear , athews , okich . nterdisciplinary management of single tooth implants. Semin Orthod. 1;-. . ribe , hau , adala , et al. lveolar ridge width and height changes after orthodontic space opening in patients congenitally missing maillary lateral incisors. Eur J Orthod. 11;1. doi1.1eocr. . undgreen , urol , Thorstensson , et al. eriodontal conditions around tipped and upright molars in adults. intra-individual retrospective study. Eur J Orthod. 1;1-. . indskog-tokland , enstrom , yman , et al. rthodontic tooth movement into edentulous areas with reduced bone height. n eperimental study in the dog. Eur J Orthod. 1;1-. 1. oss-assalli , rebenstein , Topouelis , et al. rthodontic therapy and gingival recession a systematic review. Orthod Craniofac es. 1;11-11. . il , aas r , énde-anón , et al. lveolar corticotomies for accelerated orthodontics a systematic review. J Craniomaillofac Surg. 1;-. . iedrich , rit , ininger , et al. ovement of periodontally affected teeth after guided tissue regeneration T—an eperimental pilot study in animals. J Orofac Orthop. ; 1-. . elsen , gerbaek , riksen , et al. ew attachment through periodontal treatment and orthodontic intrusion. Am J Orthod Dentofacial Orthop. 1;1-11. . elsen , gerbaek , arkenstam . ntrusion of incisors in adult patients with marginal bone loss. Am J Orthod Dentofacial Orthop. 1;-1. . ardaropoli , e , orrente , et al. ntrusion of migrated incisors with infrabony defects in adult periodontal patients. Am J Orthod Dentofacial Orthop. 1;11-. . orrente , e , bundo , et al. rthodontic movement into infrabony defects in patients with advanced periodontal disease a clinical and radiological study. J Periodontol. ;11-11.
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. elsen , iorelli . pper molar intrusion. J Clin Orthod. 1; 1-. . e , ardaropoli , bundo , et al. eduction of gingival recession following orthodontic intrusion in periodontally compromised patients. Orthod Craniofac es. ;-. . ardaropoli , e , orrente , et al. ntrusion of migrated incisors with infrabony defects in adult periodontal patients. Am J Orthod Dentofacial Orthop. 1;11-. 1. orrente , bundo , e , et al. rthodontic movement into infrabony defects in patients with advanced periodontal disease a clinical and radiological study. J Periodontol. ;11-11. . ricsson , Thilander , indhe . eriodontal condition after orthodontic tooth movements in the dog. Angle Orthod. 1;1-1. . yama , otoyoshi , irabayashi , et al. ffects of root morphology on stress distribution at the root ape. Eur J Orthod. ; 11-11. . otashnick , osenberg . orced eruption principles in periodontics and restorative dentistry. J Prosthet Dent. 1;11-1. . ontoriero , elena , icci , et al. apid etrusion with ber resection a combined orthodontic-periodontic treatment modality. Int J Periodontics estorative Dent. 1;-. . elsen , osta . mmediate loading of implants used for orthodontic anchorage. Clin Orthod es. ;-. . othe , ollen , ittle , et al. Trabecular and cortical bone as risk factors for orthodontic relapse. Am J Orthod Dentofacial Orthop. ;1-. . kantidis , hristou , Topouelis . The orthodontic-periodontic interrelationship in integrated treatment challenges a systematic review. J Oral ehail. 1;-. . ody r , lmaraghy , ceight , et al. ffects of different orthodontic retention protocols on the periodontal health of mandibular incisors. Orthod Craniofac es. 1;11-. . haughnessy T, roft , amar . nadvertent tooth movement with ed lingual retainers. Am J Orthod Dentofacial Orthop. 1; 1-.
1. atuliene , etursson , alvi . nuence of residual pockets on progression of periodontitis and tooth loss results after 11 years of maintenance. J Clin Periodontol ;-. . alvi , ischler , chmidlin . isk factors associated with the longevity of multi-rooted teeth. ong-term outcomes after active and supportive periodontal therapy. J Clin Periodontol. 1;1 1-. . ee T, uang , un T, et al. mpact of patient compliance on tooth loss during supportive periodontal therapy a systematic review and metaanalysis. J Dent es. 1;-. . chsenbein . sseous resection in periodontal surgery. J Periodontol. 1;11-. . arnevale , aldahl . sseous resective surgery. Periodontol . ;-. doi1.1.1-.. 1.. . arnevale . ibre retention osseous resective surgery a novel conservative approach for pocket elimination. J Clin Periodontol. ;1-1. doi1.1111.1-1..1.. . envert , ersson . systematic review on the use of residual probing depth, bleeding on probing and furcation status following initial periodontal therapy to predict further attachment and tooth loss. J Clin Periodontol. ;-1. doi1.1 .1-1..s-... . amford , issle . The modied idman ap. J Periodontol. 1;1-. doi1.1op.1....1. . ang . ocus on intrabony defects—conservative therapy. Periodontol . ;1-. doi1.1.1-. .1.. 1. eit-ayeld , Trombelli , eit , et al. systematic review of the effect of surgical debridement vs non-surgical debridement for the treatment of chronic periodontitis. J Clin Periodontol. ;-1. doi1.1.1-1..s... 11. Trombelli , arina , ranceschetti , et al. ingle-ap approach with buccal access in periodontal reconstructive procedures. J Peri odontol. ;-. doi1.1op...
17
Surgery First with Aligner Therapy FLAVIO URIBE and RAVINDRA NANDA
HISTORIC BACKGROUND The treatment of moderate to severe dentofacial deformity is usually addressed by means of orthognathic surgery. The objectives of orthognathic surgery are to accomplish adequate facial esthetics while achieving a functional occlusion. The occlusal relationship serves as a guide for the skeletal movements and therefore is an important element in orthognathic surgery. Fixed orthodontic appliances in the presurgical phase have historically been used to prepare the dentition for the skeletal movements and to ne-tune the occlusion after orthognathic surgery. pecically labial xed appliances in the presurgical phase eliminate dental compensations and prepare the arches for surgery. onded orthodontic brackets on the labial surfaces of the teeth and wires are the orthodontic appliances of choice by clinicians in orthognathic surgery as treatment complexity is high in these patients. lear aligner therapy T with nvisalign lign Technologies an ose at the forefront has become a treatment modality in orthodontics that has gained acceptance by practitioners after the signicant improvements in the appliance over the last few years. ore complex malocclusions have been able to be treated with this appliance with the addition of attachments that optimie tooth movements. n example of more complex approaches with the nvisalign appliance is evident in its use in tandem with orthognathic surgery instead of the conventional labial xed appliances. rthognathic surgery in conjunction with the nvisalign appliance is well accepted by patients with dentofacial deformity for two main reasons. First most of these patients are usually adults who understandably favor the inconspicuousness of clear aligners over xed labial appliances. econd often patients undergoing orthognathic surgery have received orthodontic treatment with xed appliances during their early teenage years. This treatment has usually been long as the orthodontic therapy may have tried to camouage the effects of abnormal growth. The net effect is a burnout of the patient who does not want to receive any more orthodontic therapy. rthognathic surgery has three specic stages which include a presurgical orthodontic phase the surgical procedure and a postsurgical orthodontic nishing phase. The incorporation of nvisalign in orthognathic surgery can be accomplished in different ways depending on which stage of treatment it will be used and the type surgical approach surgery rst or conventional approach. For example one of the approaches is to limit the nvisalign appliance to the presurgical phase. Typically this phase is the longest in orthognathic surgery lasting approximately from to months. Therefore if patients receive T on the
presurgical phase xed appliances will be only used for a short period of time during the postsurgical phase. This approach is often preferred since the labial xed appliances used in the postsurgical phase typically have better nishing control of the occlusion. The labial orthodontic appliances are placed just before surgery thereby facilitating the conventional approach during surgery that ties the interocclusal surgical splint to the orthodontic bonded appliances required for xation of the proximal and distal bone segments after the osteotomies. The second approach uses the nvisalign system for both pre- and postsurgical phases with no xed labial appliances which has the challenge of limited areas available to securely tie the surgical splint for maxillary and mandibular xation. lthough clinicians are using nvisalign in conjunction with orthognathic surgery no studies have been conducted evaluating the outcomes with this approach. n fact most of the published literature has been in the form of case reports. The rst report of this approach was published in using nvisalign in combination to orthognathic surgery. The treatment of two patients was described in which nvisalign was used for the presurgical phase of aligning and leveling the arches. egmental xed appliances were also used as adjuncts to the clear aligners to derotate some teeth since at that point in time the nvisalign appliance had not developed the optimied attachments that facilitated these corrections. Fixed appliances were placed just before the surgical procedure and maintained through the postsurgical detailing phase. The total treatment time for one patient was months months for the presurgical phase with nvisalign and months for the other months for the presurgical phase with nvisalign. The reason for one of the patients having undergone almost years of treatment was attributed to insurance approval and scheduling the surgery date. dditionally the patients were changing aligners every weeks. Finally the author suggested that in patients with single jaw surgery xed appliances would not be necessary being managed fully with the nvisalign appliance. n omack and ay reported on another patient treated with nvisalign and orthognathic surgery who had class malocclusion and sleep apnea. n this report bimaxillary advancement with a two-piece-maxilla for transverse correction was executed. oth the pre- and postsurgical phases were completed with the nvisalign appliance. The duration of the presurgical phase was months for this patient. The xation during surgery of the maxilla and the mandible after the osteotomies was achieved by means of archbars tied to the splint. ince the maxilla was split for transverse expansion a soft tissue splint was placed during 235
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surgery and left for weeks for stabiliation of the two maxillary halves. fter the surgical procedure polyvinyl siloxane impressions were taken for renement of the occlusion which took another months of treatment. The total treatment time was months which included a period in which the patient was not seen due to unavailability related to a work schedule. uring this nishing phase buttons were bonded to the posterior teeth to settle the occlusion with elastics. ancui et al. in reported on the treatment of a patient who had multiple missing teeth and class malocclusion who underwent orthognathic surgery with nvisalign. oth pre- and postsurgical phases were performed with the nvisalign appliance. The presurgical phase lasted months. For the xation of the maxilla and mandible into their new positions buttons were bonded to the labial surfaces of the majority of the posterior teeth. The authors maintained the patient on the splint for weeks after surgery and then delivered a dynamic functional positioner for months. ome ceramic brackets were bonded to help with the seating of the occlusion. The total treatment time was months. agani et al. in reported on another patient with a class malocclusion treated with nvisalign in the preand postsurgical phases. total of months was the duration of the presurgical alignment phase. The day before surgery xed appliances were bonded which were removed month after surgery. The total duration of treatment was months.
Splint-Aided Maxillary and Mandiblar ixatin itt abial ixed Appliane hen labial xed orthodontic appliances are not present the stabiliation of the surgical splint after the osteotomies can be troublesome. The maxilla and mandible need to be securely tied to the surgical splint to ensure proper referencing the jaws to each other to achieve the planned outcome after surgery. The surgical splint transfers the information of the virtual three-dimensional plan to guide the free osteotomied segment to a stable reference skeletal region. The splint must be tied to the dentition or denture bases to reference maxilla and mandible to each other. The connection of the splint to the teeth is usually facilitated when orthodontic appliances are bonded to the labial surfaces of the teeth. ith nvisalign there are no labial appliances to enable this connection Fig. .. ifferent approaches have been described in the literature to overcome this problem. rchbars used for maxillary and mandibular fracture xation are one of the earliest adopted approaches. The problem with this approach is it is time consuming thereby extending the duration of time the patient is under anesthesia which increases the risks of the surgical procedure. nother approach is to bond multiple buttons on the labial surfaces of teeth specically to be used for the surgical procedure. This was reported by ong et al. when using lingual orthodontic appliances in orthognathic surgery.
Fig. 17.1 Surgical splint with holes to be used in a patient undergoing orthognathic surgery using Invisalign as the only appliance for orthodontic treatment. Note that no labial orthodontic appliances are present.
17 • Surgery First with Aligner Therapy
owever since no archwires are present connecting the bonded buttons bonding failure could occur during the operation while the jaws are being tractioned to seat them into the splint. Furthermore the breakage of one of these attached buttons may end up entrapped in the mucoperiosteal aps causing a signicant complication to the surgical procedure. ith the advent of miniscrews in orthodontics the connection of the dentition to the surgical splint has been facilitated. This was reported by aik et al. who added two miniscrews in each of the quadrants mesial to the rst molars and premolars. These miniscrews are used to secure the splint tightly to the teeth and can be used after surgery to support the use of intermaxillary elastics to keep the teeth in the postsurgical planned occlusion. more complex setup that connects the miniscrews through a bar framework is commercially available. The martlock hybrid F from tryker alamaoo and the atrix F from epuy ynthes raniomaxillofacial est hester are similar bone-supported archbars to be used during surgery. This framework is secured to the labial alveolar bone of the dentition through four to six miniscrews per arch. The main advantage of these two products over an approach that uses only the miniscrews is that more locations are available to connect the surgical splint to the maxilla and mandible through ligatures. This may facilitate more tight adaptation of the osteotomied segments into the surgical splint. Typically the mesh including the miniscrews is removed after the osteotomied maxilla and mandible are secured with hardware which has the drawback that intermaxillary elastic wear in the postsurgical stage will require to be delivered from the teeth which could have an unfavorable extrusive effect on the specic teeth from which the elastics are being worn.
Tranitinin Int and Ot Srery it Clear Aliner s mentioned the major difference in the execution of surgery in patients with T is the absence of labial xed orthodontic appliances typically necessary for securing the surgical splint. These patients are typically wearing a series of sequential aligners as part of the presurgical phase and will transition to the aligners in the postsurgical phase to complete orthodontic treatment. f the patient is wearing aligners in the presurgical phase the surgical plan will consist of maxillomandibular movements that will achieve a result close to the nal idealied occlusion. rior to surgery a scan or impression is taken to plan the tooth movements after surgery to detail the occlusion which will be used for fabrication of the aligners. n alternative is to take this scan or impression after surgery. owever the acquisition of a scan or impression after surgery is somewhat difcult due the limited mouth opening observed during the rst months after surgery. Therefore taking the scan prior to surgery may be advocated to be able to start wearing the aligners soon after surgery approximately weeks after. lthough this approach may expedite treatment there still may be a slight unpredictability in the planned occlusion and the actual postsurgical occlusion if different may
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require different movements than originally planned. owever since the teeth would be usually well aligned after the presurgical phase any inaccuracies between the planned and the obtained occlusion can be managed with intermaxillary elastics. n the other hand the predictability of the planned nal occlusal outcome for the fabrication of the postsurgical aligners could be more difcult in patients where the maxilla will require segmentation in two or more pieces. n these situations it is still possible that the presurgical dental models could be segmented to the planned outcome and a scan of this model could be used for the fabrication of the surgical splint and the postsurgical aligners. owever it is better recommended to take the scan or impressions after the surgery to ensure a more precise t of the aligners especially if the segmentation is more that two pieces. nother important consideration when segmenting the maxilla is that the patient typically will have to maintain the splint after surgery for to weeks prior to resuming orthodontic movements. splint covering the incisal and occlusal surfaces of the teeth is bulky and cumbersome for a patient in recovery after surgery. splint not covering the occlusal surfaces is typically recommended for the postsurgical phase prior to resuming the new aligners Fig. .. n example of management of a patient with nvisalign appliances into and out of the surgical procedure is illustrated in Figs. . . and .. This patient received a eForte osteotomy with a three-piece segmentation for transverse expansion and vertical impaction of the posterior segments see Fig. .. The occlusion weeks after surgery at the splint removal visit shows a slight discrepancy between the surgical plan and the achieved outcome see Fig. .. The patient was scanned weeks later when she was able to achieve enough range of motion. The aligners were delivered in conjunction with vertical elastics from the miniscrews used during surgery. The occlusion was nicely established to the projected outcome approximately months after surgery see Fig. .. surgical intermaxillary splint has been designed by ystems ockville which consists of -printed thin hard acrylic templates of the maxillary and mandibular arches attached together registering the nal occlusion after the osteotomies. There is no need for wires or miniscrews to tie the osteotomied dentition to the splint. The teeth t into the splint by snapping physically into place. y using this splint a transition to the postsurgical aligners may be more easily achieved. This clear aligner orthodontic splint was recently reported by aminiti and ou who also described a reduced cost version produced by splinting ssix-type trays through clear denture repair acrylic. ne major disadvantage of this new type of intermaxillary splint is that the miniscrews are typically not placed therefore intermaxillary elastics to maintain the occlusal result after surgery require either hooks on the clear aligners or cutouts for bonding buttons or brackets to the labial surfaces of some teeth.
Srery irt and CAT very novel approach to the application of the nvisalign system in orthognathic surgery is its integration to the
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Fig. 17.2 Surgical nal splint without occlusal coverage to be left for to wees postsurgically due to a three piecemailla osteotomy.
Fig. 17.3 Threedimensional virtual surgical plan. A Presurgery.
17 • Surgery First with Aligner Therapy
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Fig. 17.3, cont’d B Planned osteotomies consisting of threepiecemailla with impaction of the posterior segments and mandibular advancement with genioplasty.
Fig. 17.4 Postsurgical occlusion deviating slightly from the planned occlusion. A ight buccal B eft buccal frontal occlusal views.
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Fig. 17.5 cclusion seated with intermaillary elastics and clear aligners to the planned outcome after months. A ight buccal B eft buccal frontal occlusal views.
surgery rst approach F. erhaps this is one of the most attractive options for patients with dentofacial deformity where the facial and smile esthetics drive their chief complaint. urgery rst addresses the dentofacial deformity from the beginning of treatment without any presurgical orthodontics. y performing orthognathic surgery in this manner it has been shown that patient satisfaction is higher than with the conventional approach. This is understandable since obviating the presurgical phase the typical decompensations that accentuate the dentofacial deformity are eliminated. Furthermore the chief complaint of the patient is immediately addressed without being postponed for a year or more as is the case with the conventional approach. nother condition where the combination of F and T is largely indicated is in the treatment of patients with obstructive sleep apnea who will undergo maxillomandibular advancement surgery. First the surgery addresses immediately the medical functional condition without a delayed presurgical orthodontic phase secondly these patients can achieve a good occlusion after surgery with the use of clear appliances which are more acceptable to this population particularly composed of adult patients. n the FT nvisalign approach two common treatment modalities have been applied. The rst consists of placing labial orthodontic appliances including a wire prior to surgery – weeks before. These xed appliances are used for to months after surgery during which time major intraarch movements are accomplished and intermaxillary vertical elastics are used to seat the occlusion. This approach also has the advantage for the surgeon of being able to tie the surgical splint to the orthodontic appliances during maxillary and mandibular osseous xation.
The appliances are then removed after this short phase of orthodontic xed therapy and nvisalign trays are given to the patient until treatment completion. The second treatment modality uses nvisalign as the only appliance for orthodontic movement after surgery without the use of any xed labial appliances. This approach unfortunately poses the same challenge on maxillary and mandibular xation for patients who do not have labial orthodontic appliances during surgery. onetheless different alternatives have been designed to facilitate and increase the predictability of the xation with nvisalign appliances as described earlier. patient who underwent F in conjunction with nvisalign is presented to illustrate this specic approach. This case report also illustrates how the virtual plan for the surgical treatment can be integrated to the orthodontic dental plan represented in the linheck lign Technologies an ose .
Cae Stdy -year-old female patient presented to the oral maxillofacial surgeon with the goal of improving her facial esthetics Fig. .. he had received orthodontic treatment during her adolescence consisting of camouage treatment for a class skeletal relationship addressed through the extraction of maxillary rst premolars. The patient had close to adequate arch alignment and a class occlusion with a -mm overjet Fig. . however there was a signicant facial convexity related to a large mandibular deciency. The denture base was anteriorly positioned to the apical base in the mandible and the lower incisors were signicantly labially inclined. The patient also had steep
17 • Surgery First with Aligner Therapy
A
B
D
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C
E
Fig. 17.6 Pretreatment etraoral photos. A Frontal lips relaed B smile prole bliue bliue smiling views. (A-C from Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. –
Fig. 17.7 Pretreatment intraoral photos. A ight buccal B Frontal Continued
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Fig. 17.7, cont’d eft buccal occlusion. aillary and andi bular occlusal views. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. –
lower mandibular and occlusal planes. The maxillary position of the incisors was overall adequate in the vertical and anteroposterior dimensions and included a good inclination in reference to the cranial base Fig. .. ll third molars had been extracted and the roots had adequate root parallelism Fig. .. To maximie the mandibular projection two options were available. The rst one required the extraction of two mandibular premolars to retract the mandibular incisors
Fig. 17.8 Pretreatment digitied lateral cephalogram. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod -
Fig. 17.9 Pretreatment panoramic radiograph. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod -
17 • Surgery First with Aligner Therapy
achieving a large overjet to obtain a signicant mandibular advancement with surgery. The second option was a nonextraction approach with a counterclockwise rotation of the maxillomandibular complex in conjunction with a genioplasty. The patient opted for the second option as she did not want any more tooth extractions and did not want a prolonged presurgical orthodontic phase of space closure. dditionally with a nonextraction approach surgery rst was indicated as it addressed her chief complaint of optimiing her facial esthetics. virtual plan was made for the surgical movements Fig. .. hen her stone models were occluded in the planned occlusion after surgery no transverse problems were observed therefore no maxillary segmentation was planned Fig. .. Figures . and shows the specic movements that were planned for this patient. The counterclockwise rotation of the maxillomandibular complex in conjunction with the genioplasty gave her approximately mm of projection at menton. rior to surgery impressions were taken for fabrication of the aligners that would address the mild crowding and would also serve to detail the occlusion in the postsurgical phase. The patient was advanced into an edge-to-edge incisor overcorrection relationship. Four miniscrews on each
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quadrant were placed interradicularily to be used during surgery for intermaxillary xation. Two weeks after surgery facial esthetics were greatly improved with the surgical procedure Fig. .. t the occlusal level a slight lateral open bite was noticed on the right side which was expected based on the planned postsurgical occlusion Fig. .. The patient was wearing intermaxillary elastics in a class direction from the more anterior miniscrews in the maxilla to the most posterior miniscrews in the mandible. Two months after surgery the facial swelling had reduced signicantly Fig. . and the patient had almost of mandibular range of motion. ll the attachments from the nvisalign appliance were bonded and small tubes bonded to the mandibular rst molars. The patient started the rst phase of aligners changing them on a weekly basis. ntermaxillary elastics from the right maxillary miniscrew implants were used to erupt the mandibular teeth on this opposing quadrant into occlusion Fig. .. Five months after surgery the lateral open bite on the right buccal segment was still evident Fig. .. cantilever arm was extended from the lower right rst molar to engage an elastic extending from the maxillary right posterior miniscrew Fig. .. The objective of this cantilever arm was to provide an uprighting moment to the right lower molar which was mesially tipped. ntermaxillary elastics were also
Fig. 17.10 A Threedimensional virtual surgical plan presurgery. Continued
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Principles and Biomechanics of Aligner Treatment
i 171 nt’d B andmar changes with the planned surgery in . ounterclocwise rotation of the maillomandibular comple. (A from Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -
worn from two mandibular buttons on the premolars to a hook in the maxillary aligner. istal to the mandibular right canine the aligner was cut to allow for extrusion on the mandibular buccal segment. Twelve months after surgery the swelling had completely resolved Fig. .. The occlusion was almost ideal at this point with some minor renement required Fig. .. fter another aligner renement phase the orthodontic treatment was nished to a good occlusal and facial result Figs. . and .. The lateral cephalogram depicts the sagittal soft and hard tissue changes Fig. . while the panoramic radiograph shows adequate root parallelism Fig. .. The superimposition reveals the
remarkable soft and hard tissue mandibular advancement Fig. .. s part of her enhancing the patient’s facial esthetics a rhinoplasty was performed approximately months after orthognathic surgery. very nice esthetic and occlusal outcome was achieved in this patient with the FT approach. nterestingly this patient was attending college in a location that was at a far distance from our institution. ost of her visits were carried during the summer when she was off school. uring the academic year she was provided with the aligners and her progress was monitored through photos she provided to our ofce every months. The patient had approximately orthodontic visits.
17 • Surgery First with Aligner Therapy
Fig. 17.11 Planned postsurgical occlusion with overcorrection. A ight buccal B Frontal eft Buccal views of the planned occlusion
Fig. 17.12 traoral photos wees postsurgery. A Frontal B Prole and Smiling views.
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Principles and Biomechanics of Aligner Treatment
Fig. 17.13 Intraoral photos wees postsurgery. A ight buccal B Frontal and eft buccal views of patient in occlusion.
Fig. 17.14 eduction of facial swelling months postsurgery. A Frontal B Prole and Smiling views. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -
17 • Surgery First with Aligner Therapy
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Fig. 17.15 Intraoral photos months postsurgery. A ight buccal B Frontal and eft buccal views. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -
Fig. 17.16 ateral open bite on the right is still present months after surgery. A ight buccal B Frontal and eft buccal views of patient in occlusion.
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Principles and Biomechanics of Aligner Treatment
Fig. 17.17 antilever arm etended from bonded lower right molar tube to upright this tooth using an elastic from the maillary miniscrews aligner cut distal to the lower right canine to allow eruption of the buccal segment.
Fig. 17.18 traoral photos months postsurgery.
Fig. 17.19 Intraoral photos months postsurgery. A ight buccal B Frontal and eft buccal views of patient in occlusion.
17 • Surgery First with Aligner Therapy
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Fig. 17.20 Posttreatment etraoral photos. A Frontal B Smiling and Prole views. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -
Fig. 17.21 Posttreatment intraoral photos. A ight buccal B Frontal and eft buccal views of patient in occlusion. Continued
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Fig. 17.21, cont’d aillary and andibular occlusal views. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -
Fig. 17.23 Posttreatment panoramic radiograph. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -
Fig. 17.22 Posttreatment lateral cephalogram. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -
Fig. 17.24 Superimposition of the seletal and soft tissue changes. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -
17 • Surgery First with Aligner Therapy
Cnlin FT is a very appealing approach for adult patients undergoing orthognathic surgery. plan for the skeletal movements in conjunction with a plan for the dental movements can be interconnected to achieve excellent occlusal and esthetic results. Furthermore the presurgical orthodontic phase can be obviated with the immediate resolution of the dentofacial deformity. This approach may become mainstream in the future as renements in the techniques and improvements in the nvisalign appliance are developed to increase predictability.
References . owling speland rogstad et al. uration of orthodontic treatment involving orthognathic surgery. Int J Adult Orthodon Orthognath Surg. -. . uther F orris art . rthodontic preparation for orthognathic surgery how long does it take and why retrospective study. Br J Oral Maxillofac Surg. -.
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. oyd . urgical-orthodontic treatment of two skeletal class patients with nvisalign and xed appliances. J Clin Orthod. -. . omack ay . urgical-orthodontic treatment using the nvisalign system. J Clin Orthod. -. . arcui alassini rocopio et al. urgical-nvisalign treatment of a patient with class malocclusion and multiple missing teeth. J Clin Orthod. -. . agani ignorino F oli et al. The use of nvisalign system in the management of the orthodontic treatment before and after class surgical approach. Case Rep Dent. . . Taub alermo . rthognathic surgery for the nvisalign patient. Semin Orthod. -. . ong ee unwoo et al. ingual orthodontics combined with orthognathic surgery in a skeletal class patient. J Clin Orthod. -. . aik oo im et al. se of miniscrews for intermaxillary xation of lingual-orthodontic surgical patients. J Clin Orthod. - qui . . aminiti ou T. lear aligner orthognathic splints. J Oral Maxillofac Surg. . . elo asparini aragiola et al. urgery-rst orthognathic approach vs traditional orthognathic approach oral health-related quality of life assessed with questionnaires. Am J Orthod Dentofacial Orthop. -.
18
Pain During Orthodontic Treatment: Biologic Mechanisms and Clinical Management TIANTONG LOU, JOHNNY TRAN, ALI TASSI, and IACOPO CIOFFI
The Importance of Orthodontic Pain Pain, as dened by the International Association for the Study of Pain, is “an unpleasant and emotional experience associated with actual or potential tissue damage or described in terms of such damage.” he maority of patients will experience arying intensities and freuencies of pain during their course of orthodontic treatment. Pain is a highly complex experience and is freuently an area of concern among patients undergoing orthodontic treatment. - he experience of pain is modulated by seeral factors, such as the magnitude of noxious stimuli, emotions, cognition, past experience and memories of pain, and other concomitant sensory experiences. rthodontic pain i.e., dental pain associated with orthodontic tooth moement can negatiely impact patient compliance and oral hygiene,- lead to increased freuency of missed appointments, and compromise the oerall treatment result. ear of pain is a maor reason for patients to forego orthodontic treatment. In one particular surey, patients rated pain as the highest area of dislie in regard to orthodontic treatment and raned pain fourth among maor fears and apprehensions. ot surprisingly, patients who experience reduced leels of orthodontic pain tend to hae an improed leel of cooperation in treatment. herefore, practitioners should aim to reduce the pain experience to improe patient compliance, decrease treatment times, and increase oerall patient satisfaction. er the last few decades, there has been an increased demand from prospectie orthodontic patients for more esthetic alternaties to traditional metal bracets and wires. rthodontic appliances that are less isible may lead to improed patient acceptance and improed uality of life.- ore recent adancements in the specialty hae led to the use of computer-aided design and computer-aided manufacturing AA technology to fabricate orthodontic appliances. his has allowed clear aligner therapy A to become aailable to the mass maret and emerge as a desirable treatment option for orthodontic patients. Since its initial introduction in , A has rapidly increased in popularity, and many orthodontists are utiliing clear aligners instead of conentional multibracet appliances to treat patients with a wide ariety of malocclusions. 252
his chapter aims to proide an oeriew regarding orthodontic pain, its relation to clear aligner therapy, as well as the pharmacologic and nonpharmacologic clinical management of pain experienced during orthodontic treatment.
Biologic Mechanisms of Orthodontic Pain and Clinical Correlates he underlying mechanism of pain during orthodontic tooth moement is a result of the complex interplay between ast numbers of neurons and chemical mediators in both the central and peripheral nerous systems. It is well nown that orthodontic pain is primarily due to an inammatory reaction in the periodontium, which accompanies orthodontic tooth moement. he application of orthodontic force results in a localied region induces ischemia, inammation, and edema in the periodontal ligament space and actiates a cascade of proinammatory mediators. ne of these mediators is the enyme cyclooxygenase- -, a critical component in the synthesis of prostaglandin, which is targeted by nonsteroidal antiinammatory drugs SAIs. ociceptie stimuli exerted by orthodontic appliances are primarily detected by sensory bers such as bers unmyelinated and thinly myelinated Ad bers in the pulp and periodontal ligament. ther substances that either actiate or sensitie nociceptors during inammation include tumor necrosis factor-a -a, interleuin I-, I-b, bradyinin, enephalin, serotonin, dopamine, glutamate g-amino butyric acid, and histamine.- Studies hae demonstrated that eleated leels of these compounds are associated with hyperalgesia., In addition, the actiated proinammatory mediators can stimulate the release of neuropeptides from the afferent nere endings into the surrounding tissues. Substance P and calcitonin gene-related peptide P are two potent neuropeptides that cause neurogenic inammation.- hese sensory neuropeptides enhance inflammation through interactions with epithelial cells to induce asodilation and increase blood essel permeability., hey also lead to mast cell degranulation and further release of proinammation mediators such as histamine and serotonin. hese inammatory mediators trigger the release of more
18 • Pain During Orthodontic Treatment: Biologic Mechanisms and Clinical Management
Pain
neuropeptides, contributing to a continuation and intensication of the inammatory process. Substance P also increases the leels of arious cytoines, such as - a, I-b, and I-. P stimulates the release of I-, I-, and -a hese cytoines sere as signaling messengers between immune cells and are important in bone resorption, deposition, and remodeling. I-b is released by broblasts of the gingia surrounding the teeth during orthodontic tooth moement and is inoled in bone remodeling. I- is a regulator of the immune response during inammation and the formation and actiity of osteoclasts.- -a is synthesied and released by monocytes and macrophages and may be related to bone remodeling. he afferent bers hae their cell bodies residing in the trigeminal ganglion of ecel cae and transmit electrical signals to the central nerous system. hey ascend the trigeminal spinal tract and enter the trigeminal sensory nuclear complex. rom the trigeminal brainstem complex, the nociceptie signal is transmitted to the thalamus and eentually to the cerebral primary somatosensory cortex, where the location of the signal is discriminated. op-down neural pathways modulate the nociceptie stimuli coming from the periphery. Although seeral brain areas are inoled in pain processing, still little is nown about how pain is encoded in the brain. oweer, it is clear that the pain and salience brain networs oerlap. he initial pattern of pain experienced by patients undergoing traditional multibracet orthodontic appliance therapy has been long studied and well documented. - Pain appears approximately to hours after orthodontic forces are applied to the teeth, with pea leels freuently occurring within the rst hours after archwire placement, followed by a steady decrease toward baseline leels within days ig. .. - hese ndings hae been conrmed in seeral racial and ethnic groups - and through the use of ecologic momentary assessment. here also appears to be a diurnal ariation in pain experienced by patients, with higher leels occurring in the eenings and nights. erall, patients are generally able to tolerate and adapt to new appliances within wee after placement. oweer, female patients in middle adolescence hae been reported to experience more pain than age-matched males and younger patients when exposed to orthodontic procedures. In addition, orthodontic pain is signicantly affected by menstrual phase, with the pain leels being higher
24h 48h 72h
7 days
Fig. 18.1 Trajectory of dental pain after orthodontic procedures.
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in the luteal phase. hile there is conicting reports on the effect of age on orthodontic pain perception, there is substantial eidence that the type of malocclusion and the amount of crowding hae little effect on pain experienced during orthodontic treatment. hese ndings suggest that pain is liely most affected by other factors, including hormonal and psychological ariables. ne such example is anxiety, which among other things can be dependent on the relationship with the orthodontic care proider.
Orthodontic Tooth Pain in Clear Aligner Therapy rthodontic pain associated with A has been inestigated in a limited number of studies. A appears to follow a similar pattern of pain progression in terms of peaing at hours and trending toward baseline leels after days.,-, oweer, to date, A has mainly been associated with more intermittent forces as compared to conentional treatment with multibracet appliances, although seeral companies are focusing on deeloping materials that may proide more gentle and continuous forces. nly a limited number of studies exist that examine orthodontic pain in patients undergoing A with Inisalign’s latest generation multilayered polyurethane-based polymer, Smartrac. hese studies show a maximum patient-reported pain score of mm on a -mm isual analogue scale AS, which may be considered mild and of limited clinical signicance. In preious literature, xceed- thermoplastic material was used in the older generation, and coincidently these studies showed signicantly higher reported pain scores in the rst wee of treatment up to mm on AS. imited eidence suggests Smartrac may be more comfortable than older generation materials, but further studies are needed to alidate this. Interestingly, with continued actie tooth moements of the subseuent aligner stages, there is less pain reported by patients compared to the rst stage aligners een if the rst stage aligners are programmed to be passie without actie tooth moements. his perhaps could be a result of the accuracy, t, and deformation of the rst trays, the introduction of iatrogenic posterior occlusal interferences, or the apprehension and stress inoled with starting orthodontic treatment with a new appliance. Indeed, pain perception with A, especially during the rst stage, is signicantly related to an indiidual’s psychological stress and anxiety. In general, when compared to traditional multibracet appliances, A results in less reported pain and improed patient experience. iller et al. conducted the rst study ealuating the differences in pain and impact on uality of life experienced by patients undergoing A ersus multibracet appliance therapy. his was a prospectie longitudinal cohort study with A patients and multibracet appliance patients. he participants were ased to use a daily diary for days, measuring functional, psychosocial, and pain-related impacts. he diary consisted of uestions adapted from the eriatric ral ealth Assessment Index, a -point iert scale for demographic data, and a isual analog scale for pain. he results showed that the
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progression of pain in aligner treatment followed a similar pattern to multibracet appliances, in which pain peaed after hours and gradually returned to normal. Additionally, although the initial leels of pain were higher for the multibracet appliance group, along with higher leels of analgesic consumption, both groups recoered to baseline within days. In a subseuent study by Shalish et al., patients being treated by either buccal multibracet appliances, lingual multibracet appliances, or A were recruited to complete a health-related uality of life uestionna ire - and a -point scale for dysfunction during the rst wee and on day . heir results showed the aerage initial pain leels were consistently higher in the lingual multibracet appliance and clear aligner groups, with analgesic consumption paralleling the dynamics of the pain leels although the difference did not reach statistical signicance. In all groups, the pain leels subsided within wee. hese results contradict the ndings by iller et al., which the authors attributed to a greater mechanical force being applied in the aligner group compared to the buccal multibracet appliance group. o further elucidate and compare pain leels between these orthodontic treatment modalities, uiyama et al. conducted a prospectie clinical trial with patients receiing either A, multibracet appliance therapy, or a hybrid treatment combining both modalities. sing AS, the participants were ased to record their pain leels at time points of seconds, hours, hours, and to days post appliance insertion. his was repeated at wees and after appliance deliery. heir results illustrated a similar pattern of pain progression during the rst wee of appliance deliery for all groups studied. oweer, the oerall pain leels were signicantly more intense and longer lasting for the multibracet appliance group than either the aligner or the hybrid group. In a recent study by hite et al., patients were randomly allocated to either clear aligner or multibracet appliance treatment groups to inestigate differences in their pain leels. he participants were ased to complete a daily diary with pain measured on AS. he diary was completed at initial appliance deliery, daily for the rst wee, as well as the rst days after their next two follow-up appointments. he pattern of pain progression during the rst wee following initial appliance actiation was in general agreement with preious studies.,,,,, he clear aligner group experienced consistently lower discomfort than the multibracet appliance group during most of the rst wee, with statistically signicant differences obsered after to days. oreoer, analgesic consumption was more freuent in the multibracet appliance group, and their rate of consumption closely mirrored the pattern of pain progression during the rst wee. Similarly, oer a relatiely longer term of months, the leel of pain was less in the aligner group than the multibracet appliance group. he patients in the multibracet appliance group may hae experienced an increased initial inammatory response, which led to increased sensitiation of the nociceptors and higher pain sensation in subseuent follow-up appointments. he results of hite et al., uiyama et al., and iller et al. comparing pain and discomfort between A and
multibracet appliances are in general agreement with one another, as well as with past studies that demonstrated multibracet appliances may cause more pain than remoable appliances.,,, As mentioned earlier, these results were in contrast to the ndings from Shalish et al., who reported the pain was greater in patients treated with aligners than multibracet appliances. ne possible explanation for this discrepancy could be the ariations in the initial archwires used between the studies. or example, the classic nicel titanium ii or nitinol wires used in the Shalish et al. study hae been shown to display higher pea discomfort than the superelastic copper ii wires used in hite et al., urthermore, the hite et al. study was the only one to utilie Smartrac, a new aligner material brought to maret by Align echnology in ,, whereas the preious studies used the older xceed- aligner material. imited eidence suggests Smartrac may be more comfortable than preious materials, although further studies are needed to erify this. astly, Shalish et al. speculated that the differences in pain leels obsered may possibly hae been due to a higher leel of mechanical force being applied early in treatment for the aligner group. In summary, although orthodontic pain exists with A, the current eidence seems to suggest it is of a lesser degree than multibracet appliances, especially during the rst wee. oweer, additional studies proiding more substantial data are needed. As would be expected, actiation in the aligner tray has been reported as the most freuent cause of pain and discomfort. oweer, other issues leading to pain in association with clear aligners might include nonsmooth edges, tray, and attachment deformation.
Modulators of Pain: Psychological actors linical and pain assessment literature continues to be focussed on identifying and managing specic cognitie and psychological factors that are related to the indiidual’s experience of pain. In orthodontics, pain is a common seuela and expected with treatment. oweer, it is apparent clinically that the perception of pain aries considerably across indiiduals when the same stimulus, such as an initial light archwire, is actiated. he expected pain from an orthodontic adustment is generally belieed to be relatiely minor and self-limiting howeer, some patients will report a much different experience. It is generally accepted that particular affectie and cognitie behaioral factors contribute to these differences in indiidual pain perception. Specically releant to medical and dental settings, pain perception is inuenced by factors such as somatosensory amplication, anxiety, depression, and catastrophiing.- It has been shown that patients with prolonged pain during orthodontic treatment exhibit higher leels of anxiety than indiiduals with pain of short duration. urthermore, experimentally induced orthodontic pain ia elastomeric separators is greater in indiiduals who exhibit higher leels of trait anxiety and somatosensory amplication—a tendency to perceie normal somatic and isceral sensations as being relatiely intense, noxious, and
18 • Pain During Orthodontic Treatment: Biologic Mechanisms and Clinical Management
disturbing—as compared to indiiduals with low leels of both. f importance, anxiety and other mood disorders hae been found to be related to increased freuencies of waing-state oral parafunctional behaiors, such as waetime tooth clenching,- which are also associated with temporomandibular disorders.,, herefore, it might be uestioned whether anxiety, orthodontic pain, and aw motor behaior are intertwined. ecently, we performed a large web surey and recruited indiiduals subdiided into groups with high, intermediate, and low leels of trait anxiety., lastomeric separators were applied to the molars and pain and freuency of tooth clenching episodes were recorded for days. A signicant correlation orthodontic pain and freuency of tooth clenching was obsered. In participants with high anxiety, the decrease in orthodontic pain was paralleled by a decrease in the freuency of waetime tooth clenching episodes. hese results suggest that indiiduals with high trait anxiety may respond with an aoidance behaior decrease of aw motor actiity to orthodontic stimuli as a method to reducing their pain experience. he relationship between aw motor actiity and orthodontic pain is supported by a recent study that demonstrated a reduced masticatory performance in orthodontic patients during the period in which they reported the maximum leels of pain and creicular I-b. oweer, there is some eidence of increased aw muscle actiity with A,, leading to aw muscle tenderness of limited clinical signicance. ec et al. estimated the contribution of psychological factors to orthodontic pain. f interest, for eery pain catastrophiing scale PS magnication score of unit higher, the relatie ris of being a high-pain responder was .. agnication refers to an indiidual’s tendency to exaggerate the threat alue of nociceptie inputs. In this study, the authors showed that cold sensitiity signicantly predicts the pain experienced, with those reporting greater scores for cold sensitiity haing greater orthodontic pain. his result supports the hypothesis that somatosensory amplication plays a maor role in orthodontic pain experience. aluation of the aboementioned psychological constructs in a clinical setting utiliing alidated uestionnaires is adisable to identify indiiduals who may be more sensitie to pain and discomfort during orthodontic therapy. Anxiety and symptom perception management might be recommended for those susceptible indiiduals.
Clinical Considerations for the Management of Orthodontic Pain In the last decade, seeral reiews and clinical studies hae been published on the management of orthodontic pain. It is well nown that pharmacologic approaches with oerthe-counter analgesics are effectie in managing orthodontic pain. In particular, acetaminophen paracetamol is usually prescribed in place of SAIs to aoid possible effects on the rate of tooth moement., Indeed, SAIs hae been reported to interfere with the synthesis of prostaglandin P, which is nown to be an important chemical mediator during the bone remodeling
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process., A recent ochrane reiew, including randomied controlled trials s and , participants aged to years, did not nd any eidence of a difference in efcacy between SAIs and paracetamol at , , or hours postinterention. hey concluded that analgesics are more effectie at reducing orthodontic pain than placebo or no treatment. Sandhu and ecie examined the diurnal ariation of pain in orthodontic patients. onsistent with the aboementioned studies, pain was reported to pea after hours. Interestingly, during the pea period, orthodontic pain was lower during the afternoon as compared to the night and morning. herefore, the authors suggested that patients should be adised to tae analgesics accordingly and need not be prescribed routine analgesics to be taen eery to hours. In addition, they suggested that preemptie administration of analgesics may be more effectie than posttreatment administration, as the traditional administration at regular interals does not consider temporal ariations in orthodontic pain. oweer, the preiously mentioned reiew indicated there is ery low eidence suggesting preemptie ibuprofen gies better pain relief at hours than ibuprofen taen posttreatment. inally, it must be noted that the combination of acetaminophen plus ibuprofen proides greater analgesic efcacy than acetaminophen or ibuprofen alone. Special considerations should be made for patients with a history of regularly taing pain medications. Indeed, a recent literature reiew which included animal studies suggested that long-term consumption of pain relieers can signicantly affect the rate of orthodontic tooth moement. Surprisingly, they found that animals in treatment with ibuprofen did not show a signicant decrease in orthodontic tooth moement, as some preious human studies had shown. n the other hand, long-term administration of indomethacin, etorolac, and high doses of etoricoxib decreased the amount of tooth moement. oweer, caution should be taen when interpreting these results due to the uestionable uality of eidence that is aailable. Seeral nonpharmacologic approaches hae been considered to manage orthodontic pain. In another recent ochrane reiew, leming et al. included s with participants and analyed the effects of low-leel laser therapy , ibratory aduncts, experimental chewing aduncts e.g., bite wafers and chewing gum, and psychosocial and physical interentions on orthodontic pain. hey concluded that laser irradiation may help reduce orthodontic pain in the short term. n the other hand, eidence to support other methods is of low uality. It is the opinion of the authors that nonpharmacologic interentions should be used wheneer possible to reduce orthodontic pain able ., proided they do not expose patients to harm or additional costs during treatment they should be used especially when a medical condition preents the use of recommended analgesics. f foremost importance, clinicians should establish a relationship of trust with patients and improe their communication sills to reduce nocebo and faor placebo effects. erall, a proper pain management approach would reuire a careful baseline assessment of pain predictors, psychological factors, and patient expectations. oreoer, placebo and nocebo effects should be considered when communicating with
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Tale 181 Strategies to educe Pain During Orthodontic Treatment Pharmacologic
onpharmacologic
Doctorpatient communication
Acetaminophen or iuprofen P
n
Cheing adjuncts
n
oleel laser therapy
n
iratory stimulation
mproe pre and posttreatment communication
igh leel of eidence to support pain reduction ith this treatment o leel of eidence to support orthodon tic pain reduction ith this treatment igh leel of eidence to support pain re duction ith this approach
PRN, Pro re nata (As necessary).
patients. lasini et al. highlighted that negatie patientpractitioner interaction should be aoided and that communication with patients should be well-balanced by not proiding excessie negatie information with regard to side effects and limiting information regarding benets.
References . ersey , Albe essard , onica , et al. Pain terms a list with definitions and notes on usage. ecommended by the IASP Subcommittee on axonomy. Pain. . . Scheurer PA, irestone A, ürgin . Perception of pain as a result of orthodontic treatment with xed appliances. Eur J Orthod. -. . oayedi , ais . heories of pain from specicity to gate control. J europhysiol. -. . am , erdet , ondei . raumatic ulcers and pain during orthodontic treatment. Community Dent Oral Epidemiol. -. . ew . Attitudes and perceptions of adults towards orthodontic treatment in an Asian community. Community Dent Oral Epidemiol. -. . lier , napman . Attitudes to orthodontic treatment. r J Orthod. -. . luemper , iser , ayens , et al. fcacy of a wax containing benocaine in the relief of oral mucosal pain caused by orthodontic appliances. Am J Orthod Dentofacial Orthop. -. . how , iof I. Pain and orthodontic patient compliance a clinical perspectie. Semin Orthod. -. . Sergl , lages , entner A. Pain and discomfort during orthodontic treatment causatie factors and effects on compliance. Am J Orthod Dentofacial Orthop. -. . ra A, ennani , arella . Psychological aspects of orthodontics in clinical practice. Part one treatment-specic ariables. Prog Orthod. -. . ruemeyer A, Arruda A, Inglehart . Pain and orthodontic treatment. Angle Orthod. -. . rishnan . rthodontic pain from causes to management—a reiew. Eur J Orthod. -. . oani , againi , elucchi A, et al. Self-reported pain after orthodontic treatments a randomied controlled study on the effects of two follow-up procedures. Eur J Orthod. -. . Asham AA. eaders’ forum orthodontic pain. Am J Orthod Dentofacial Orthop. A. . eim . anaging orthodontic pain. J Clin Orthod. -. . ’onnor P. Patients’ perceptions before, during, and after orthodontic treatment. J Clin Orthod. -. . Albino , awrence S, opes , et al. ooperation of adolescents in orthodontic treatment. J ehav Med. -.
. iannopoulou , udic A, iliaridis S. Pain discomfort and creicular uid changes induced by orthodontic elastic separators in children. J Pain. -. . iuchosi P, ields , ohnston , et al. Assessment of perceied orthodontic appliance attractieness. Am J Orthod Dentofacial Orthop. S-S. . osall , ields , iuchosi , et al. Attractieness, acceptability, and alue of orthodontic appliances. Am J Orthod Dentofacial Orthop. , e-e, discussion -. . Shalish , ooper-aa , Igi I, et al. Adult patients’ adustability to orthodontic appliances. Part I a comparison between labial, lingual, and Inisalign. Eur J Orthod. -. . ’rien , ay , ox , et al. Assessing oral health outcomes for orthodontics—measuring health status and uality of life. Community Dent Health. -. . unningham S, unt P. uality of life and its importance in orthodontics. J Orthod. -. . ong . Inisalign A to . Am J Orthod Dentofacial Orthop. -. . orton , erahshan , aa S, et al. esign of the Inisalign system performance. Semin Orthod. -. . Par , ae , ee , et al. ypoxia inducible factor- alpha directly induces the expression of receptor actiator of nuclear factor-appa ligand in periodontal ligament broblasts. Mol Cells. -. . ee , atsuiaa , hashi S, et al. ypoxia actiates the cyclooxygenase--prostaglandin synthase axis. Carcinogenesis. -. . yranides S, uang , aber . eurologic regulation and orthodontic tooth moement. In antarci A, ill , en S, eds. Tooth Movement. asel arger -. . oreall I, atsson , orsgren S. ain sensory neuropeptides, but not IP and P, are inoled in bone remodeling during orthodontic tooth moement in the rat. Ann Acad Sci. -. . amasai , Shibata , Imai S, et al. linical-application of prostaglandin- P upon orthodontic tooth moement. Am J Orthod. -. . aler A, aner S, arris , et al. he enephalin response in human tooth-pulp to orthodontic force. Am J Orthod Dentofacial Orthop. -. . aidoitch , icolay , gan P, et al. eurotransmitters, cytoines, and the control of aleolar bone remodeling in orthodontics. Dent Clin orth Am. -. . icolay , aidoitch , Shanfeld , et al. Substance-P immunoreactiity in periodontal tissues during orthodontic tooth moement. one Miner. -. . Alhashimi , rithiof , rudi P, et al. rthodontic tooth moement and de noo synthesis of proinammatory cytoines. Am J Orthod Dentofacial Orthop. -. . riee III , ohnson , oore , et al. Prostaglandin P and interleuin- beta I- beta leels in gingial creicular uid during human orthodontic tooth moement. Am J Orthod Dentofacial Orthop. -. . andesa-adunoic . eural modulation of inammatory reactions in dental tissues incident to orthodontic tooth moement. A reiew of the literature. Eur J Orthod. -. . ato , Ichiawa , aisaa S, et al. he distribution of asoactie intestinal polypeptides and calcitonin gene-related peptide in the periodontal-ligament of mouse molar teeth. Arch Oral iol. -. . innsland I, eyeraas , yers . ffects of dental trauma on pulpal and periodontal nere morphology. Proc inn Dent Soc Suomen Hammaslaaariseuran Toimitusia. S-S. . innsland I, innsland S. hanges in P-immunoreactie nere-bers during experimental tooth moement in rats. Eur J Orthod. -. . innsland S, eyeraas , ford S. ffect of experimental tooth moement on periodontal and pulpal blood-ow. Eur J Orthod. -. . Saito I, Ishii , anada , et al. esponses of calcitonin gene-related peptide-immunopositie nere-bers in the periodontal-ligament of rat molars to experimental tooth moement. Arch Oral iol. -.
18 • Pain During Orthodontic Treatment: Biologic Mechanisms and Clinical Management . oreall I, orsgren S, atsson . xpression of neuropeptides P, substance P during and after orthodontic tooth moement in the rat. Eur J Orthod. -. . aggi A, iuliani S, Santicioli P, et al. Peripheral effects of neuroinins— functional eidence for the existence of multiple receptors. J Auton Pharma col. -. . ray , arshall I. uman alpha-calcitonin gene-related peptide stimulates adenylate-cyclase and guanylate-cyclase and relaxes rat thoracic aorta by releasing nitric-oxide. r J Pharmacol. -. . Assem S, hanem S, Abdullah A, et al. Substance-P and Arg-Pro-ys-Pro----induced mediator release from different mast-cell subtypes of rat and guinea-pig. mmunopharmacology. -. . amaguchi , asai . Inammation in periodontal tissues in response to mechanical forces. Arch mmunol Ther Ep ars. -. . owen , ood , Ihrie , et al. An interleuin- lie factor stimulates bone-resorption initro. ature. -. . Stasheno P, bernesser S, ewhirst . ffect of immune cytoines on bone. mmunol nvest. -. . Ishimi , iyaura , in , et al. I- is produced by osteoblasts and induces bone-resorption. J mmunol. -. . urihara , ertolini , Suda , et al. I- stimulates osteoclast-lie multinucleated cell-formation in long-term human marrow cultures by inducing I- release. J mmunol. -. . owi , an der Pluim , loys , et al. Parathyroid-hormone P and P-lie protein PP stimulate interleuin- production by osteogenic cells—a possible role of interleuin- in osteoclastogenesis. iochem iophys es Commun. -. . aeichi , Saito I, surumachi , et al. xpression of inammatory cytoine genes in io by human aleolar bone-deried polymorphonuclear leuocytes isolated from chronically inamed sites of bone resorption. Calcif Tissue nt. -. . Sessle . he neurobiology of facial and dental pain present nowledge, future directions. J Dent es. -. . ais , oayedi . entral mechanisms of pain reealed through functional and structural I. J euroimmune Pharmacol. -. . ones , han . he pain and discomfort experienced during orthodontic treatment a randomied controlled clinical trial of two initial aligning arch wires. Am J Orthod Dentofacial Orthop. -. . gan P, ess , ilson S. Perception of discomfort by patients undergoing orthodontic treatment. Am J Orthod Dentofacial Orthop. -. . ilson S, gan P, ess . ime course of the discomfort in young patients undergoing orthodontic treatment. Pediatr Dent. -. . Stewart , err , aylor P. Appliance wear the patient’s point of iew. Eur J Orthod. -. . Shalish , ooper-aa , Igi I, et al. Adult patients’ adustability to orthodontic appliances. Part I a comparison between labial, lingual, and Inisalign. Eur J Orthod. -. . iller , corray SP, omac , et al. A comparison of treatment impacts between Inisalign aligner and xed appliance therapy during the rst wee of treatment. Am J Orthod Dentofacial Orthop. , -e. . uiyama , ono , Suui , et al. Analysis of pain leel in cases treated with Inisalign aligner comparison with multibracet edgewise appliance therapy. Prog Orthod. . . hite , ulien , acob , et al. iscomfort associated with Inisalign and traditional bracets a randomied, prospectie trial. Angle Orthod. -. . ergius , iliaridis S, erggren . Pain in orthodontics. A reiew and discussion of the literature. J Orofac Orthop. -. . gan P, ilson S, Shanfeld , et al. he effect of ibuprofen on the leel of discomfort in patients undergoing orthodontic treatment. Am J Orthod Dentofacial Orthop. -. . irestone A, Scheurer PA, ürgin . Patients’ anticipation of pain and pain-related side effects, and their perception of pain as a result of orthodontic treatment with multibracet appliances. Eur J Orthod. -. . rdinç A, inçer . Perception of pain during orthodontic treatment with xed appliances. Eur J Orthod. -.
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. Polat , araman A. Pain control during xed orthodontic appliance therapy. Angle Orthod. -. . Sew oy , Anoun S, in , et al. cological momentary assessment of pain in adolescents undergoing orthodontic treatment using a smartphone app. Semin Orthod. -. . ones , han . Pain in the early stages of orthodontic treatment. J Clin Orthod. -. . Sergl , entner A. A comparatie assessment of acceptance of different types of functional appliances. Eur J Orthod. -. . Sandhu SS, Sandhu . rthodontic pain an interaction between age and sex in early and middle adolescence. Angle Orthod. -. . ong , ao , hu , et al. he effects of menstrual phase on orthodontic pain following initial archwire engagement. Oral Dis. -. . Abdelrahman Sh, Al-imri S, Al aaitah . Pain experience during initial alignment with three types of nicel-titanium archwires a prospectie clinical trial. Angle Orthod. -. . iof I, Piccolo A, agliaferri , et al. Pain perception following rst orthodontic archwire placement—thermoelastic s superelastic alloys a randomied controlled trial. uintessence nt. -. . iof I, ichelotti A, Perrotta S, et al. ffect of somatosensory amplication and trait anxiety on experimentally induced orthodontic pain. Eur J Oral Sci. -. . oy , empster . ental anxiety associated with orthodontic care prealence and contributing factors. Semin Orthod. -. . ran , ou , ebiolo , astroorio , assi A, iof I. Impact of clear aligner therapy on tooth pain and masticatory muscle soreness. J Oral ehail. -. . rascher A, uran , eldmann , et al. Patient surey on Inisalign treatment compare the Smartrac material to the preious aligner material. J Orofac Orthop. -. . ichelotti A, iof , andino , et al. ffects of experimental occlusal interferences in indiiduals reporting different leels of wae-time parafunctions. J Orofac Pain. -. . lar , suiyama , aba , et al. Sixty-eight years of experimental occlusal interference studies what hae we learned J Prosthet Dent. -. . arp , arp A. he alidity, reliability and generaliability of diary data. Ep Aging es. -. . Atchison A, olan A. eelopment of the geriatric oral health assessment index. J Dent Educ. -. . ooic A, ocer , Stephens , et al. alidity and reliability of a uestionnaire for measuring child oral-health-related uality of life. J Dent es. -. . ocer . Applications of self-reported assessments of oral health outcomes. J Dent Educ. -. . ocer , ooic A. sing subectie oral health status indicators to screen for dental care needs in older adults. Community Dent Oral Epidemiol. -. . oung A, aylor , aylor S, et al. aluation of preemptie aldecoxib therapy on initial archwire placement discomfort in adults. Angle Orthod. -. . anilioglu , tür . Patient discomfort a comparison between lingual and labial multibracet appliances. Angle Orthod. -. . u A, crath , ong , et al. A comparison of pain experienced by patients treated with labial and lingual orthodontic appliances. Eur J Orthod. -. . ernandes , gaard , Soglund . Pain and discomfort experienced after placement of a conentional or a superelastic ii aligning archwire. A randomied clinical trial. J Orofac Orthop. -. . aano , Satoh , orris , et al. echanical properties of seeral nicel-titanium alloy wires in three-point bending tests. Am J Orthod Dentofacial Orthop. -. . Align echnology. Align echnology receies .S. patents for Smartrac Inisalign aligner material. httpswww.inisalign.catheinisalign-differencesmarttrac-material. Accessed ay , . . Align echnology. Align echnology announces anuary st aailability of Smartrac Inisalign aligner material. httpsinestor. aligntech.comnews-releasesnews-release-detailsalign-technologyreceies-us-patents-smarttracr-inisalignr. Accessed anuary , . . rascher A, uran , eldmann r , et al. Patient surey on Inisalign treatment compare the Smartrac material to the preious aligner material. J Orofac Orthop. -.
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. Sturgeon A, autra A. Psychological resilience, pain catastrophiing, and positie emotions perspecties on comprehensie modeling of indiidual pain adaptation. Curr Pain Headache ep. . . Sullian , ishop S, Pii . he pain catastrophiing scale deelopment and alidation. Psychol Assess. -. . ec , arella , handler P, et al. actors associated with pain induced by orthodontic separators. J Oral ehail. -. . aea-elasco , ely-argeot , ilarrasa A, et al. oint hypermobility syndrome problems that reuire psychological interention. heumatol nt. -. . Sullian , horn , aythornthwaite A, et al. heoretical perspecties on the relation between catastrophiing and pain. Clin J Pain. -. . acobsen P, utler . elation of cognitie coping and catastrophiing to acute pain and analgesic use following breast cancer surgery. J ehav Med. -. . ur , udy . Assessment of cognitie-factors in chronic pain—a worthwhile enterprise. J Consult Clin Psychol. -. . eyneman , remouw , ano , et al. Indiidual-differences and the effectieness of different coping strategies for pain. Cognit Ther es. -. . aton . linical and health serices relationships between maor depression, depressie symptoms, and general medical illness. iol Psychiatry. -. . ec A. A systematic inestigation of depression. Compr Psychiatry. -. . ang , ian , hen , et al. ognitie behaioral therapy for orthodontic pain control a randomied trial. J Dent es. -. . ergius , roberg A, aeberg , et al. Prediction of prolonged pain experiences during orthodontic treatment. Am J Orthod Dento facial Orthop. , e-e. . arsy A, oodson , ane S, et al. he amplication of somatic symptoms. Psychosom Med. -. . ariewic , hrbach , call . ral behaiors checlist reliability of performance in targeted waing-state behaiors. J Orofac Pain. -. . ndo , anemura , anabe , et al. lenching occurring during the day is inuenced by psychological factors. J Prosthodont es. -. . inocur , iel , isha , et al. Self-reported bruxism—associations with perceied stress, motiation for control, dental anxiety and gagging. J Oral ehail. -. . ichelotti A, iof I, esta P, et al. ral parafunctions as ris factors for diagnostic subgroups. J Oral ehail. -. . Slade , hrbach , reenspan , et al. Painful temporomandibular disorder decade of discoery from PPA studies. J Dent es. -.
. how , iof I. ffects of trait anxiety, somatosensory amplication, and facial pain on self-reported oral behaiors. Clin Oral nvestig. -. . Spielberg , orsuch , e . Manual of the StateTrait Aniety nventory. Palo Alto onsulting Psychologists Press . . how . Effects of Aniety and Daytime Clenching on Orthodontic Pain Perception. niersity of oronto . . ameiro , Schult , rein P, et al. Association among pain, masticatory performance, and proinammatory cytoines in creicular uid during orthodontic treatment. Am J Orthod Dentofacial Orthop. -. . astroorio , argellini A, ucchese A, et al. ffects of clear aligners on sleep bruxism randomied controlled trial. J iol egul Homeost Agents. -. . ou , ran , astroorio , assi A, iof I. aluation of masticatory muscle response to clear aligner therapy using ambulatory electromyographic recording. Am J Orthod Dentofacial Orthop. e-e. . Arias , arue-roco . Aspirin, acetaminophen, and ibuprofen their effects on orthodontic tooth moement. Am J Orthod Dentofacial Orthop. -. . oche , isneros , Acs . he effect of acetaminophen on tooth moement in rabbits. Angle Orthod. -. . eier , anda S, urrier , et al. he effects of exogenous prostaglandins on orthodontic tooth moement in rats. Am J Orthod Dentofacial Orthop. -. . yroola , Spyropoulos . ffects of drugs and systemic factors on orthodontic treatment. uintessence nt. -. . on A, arrison , orthington , et al. Pharmacological interentions for pain relief during orthodontic treatment. Cochrane Dataase Syst ev. . . Sandhu S, ecie . iurnal ariation in orthodontic pain clinical implications and pharmacological management. Semin Orthod. -. . ng , Seymour A, ir P, et al. ombining paracetamol acetaminophen with nonsteroidal antiinammatory drugs a ualitatie systematic reiew of analgesic efcacy for acute postoperatie pain. Anesth Analg. -. . arygiannais A, alamanos , Athanasiou A. oes longterm use of pain relieers hae an impact on the rate of orthodontic tooth moement A systematic reiew of animal studies. Eur J Orthod. -. . leming PS, Strydom , atsaros , et al. on-pharmacological interentions for alleiating pain during orthodontic treatment. Cochrane Dataase Syst ev. . . lasini , osas S, olloca . Placebo hypoalgesic effects in pain potential applications in dental and orofacial pain management. Semin Orthod. -.
19
Retention and Stability Following Aligner Therapy JOSEF KUČERA and IVO MAREK
Retention and Stability in Orthodontic Treatment INTRODUCTION Orthodontic treatment is an area of medicine and dentistry that has to address not just health and function but also aesthetics. It is usually the aesthetic considerations that make patients seek out orthodontic treatment in the rst place. Achieving an excellent aesthetic and functional result can be lengthy and expensive, therefore it is in the interests of both the patient and the clinician that the result of orthodontic treatment remains stable in the long term. Unfortunately the importance of the retention phase is often underestimated, hen in reality it is as important to the patients as the active orthodontic treatment itself. he period after the completion of active treatment can be divided into a retention period and a postretention period. he purpose of the retention phase folloing active orthodontic treatment is to prevent relapse dened as the natural tendency of the teeth to migrate into their original position in the dental arch and to eliminate the inuence of other factors that might destabilie the result. It is very dif cult to say ho long the retention phase should last. he literature offers many recommendations, although they vary considerably and are often vague. ome authors sug gest that, folloing orthodontic treatment, teeth should be held in the position achieved by treatment for as long as it is necessary to sustain the result, or that the retention phase should be as long as needed and as short as possible. Others suggest that retainers should be used until the patient’s groth is complete or the third molars erupt, or for a period of years or even years, or simply as long as the patient ishes to keep the teeth aligned. It is generally recommended that nongroing patients ear retainers for at least year and is biologically dened as the completion of the reorganiation of bone and peri odontal ligaments around the teeth. ollagen bers are reorganied ithin the rst to months. his period is critical, and the earing of retention appliances is essential because relapse is very likely at this stage after this critical period the risk decreases substantially. oever, the reor ganiation of elastic supracrestal bers may take more than year, hich makes the retention of severely rotated teeth particularly difcult some authors recommend adjunctive surgical procedures such as berotomy to decrease the amount of relapse., In groing patients retainers should be orn until the groth is complete. At the time patients stop earing the retention appliances, the postretention period begins, and it is only then that e get a true picture
of the stability of the original result that had been achieved by the orthodontic treatment. uring the postretention period numerous factors and the complexity of their inter actions may ultimately destabilie treatment results.
FACTORS INFLUENCING LONG-TERM STABILITY ith regard to stability there are some general guidelines and recommendations for orthodontic treatment, and so long as these are respected hen making and carrying out the treatment plan they tend to produce stable results ith relatively little risk of relapse. In such cases, longterm changes in dental arches of treated patients are then simi lar to those occurring in untreated subjects. efore starting treatment, orthodontists need to keep in mind that the position of the teeth and the shape of the dental arches are the balanced result of many factors, espe cially the inuence of the forces exerted by the surrounding soft tissues i.e., pressure from the cheeks, lips, and tongue that create a “neutral one” or “one of stability.” Orthodon tic movement of the teeth outside of this neutral one pushes them into an unbalanced one, ith conseuent relapse., he shape of the dental arch, particularly the mandibular arch, should therefore be respected in the plan ning and implementation of treatment because changes in arch shape tend to relapse into the original shape in the long term., he upper dental arch may be expanded more than the loer arch in indicated cases rapid maxillary expansion hoever, even in these cases, the longterm sta bility appears to be uite problematic. Any changes in the loer intercanine distance are also very prone to relapse,, partly because decrease in the loer intercanine distance is due to the natural changes that occur in the dental arch as a result of aging., he uality of articulation and inter cuspation can also be very important for the longterm sta bility.,, he correct intercuspation of the teeth in lateral segments ith high cusps itself provides the best retention, both in sagittal and transverse dimensions. It is also impor tant to achieve the correction in the vertical direction, and especially for sufcient correction of the deep bite, as its deepening reduces the space for the loer incisors. Incisor shape can also be a source of posttreatment instability. In triangularshaped incisors, recontouring of the approximal surfaces i.e., interproximal enamel reduction, stripping provides more stable contact beteen the incisors. Accord ing to some studies, this stabiliing effect of loer incisor stripping is comparable to the efciency of bonded retain ers., imilarly, the adjustment of large proximal enamel ridges on the palatal surfaces of the upper incisors is also important for the stability of the incisor region. 259
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ontinuing groth is a separate issue and needs to be addressed ith particular attention in more pronounced skeletal malocclusions, especially in the sagittal and vertical dimensions, hich continue to gro over a longer period than in the transverse dimension. Unfavorable groth of the jas has a negative impact on the occlusal relationship and on the position of incisors due to the dentoalveolar compensation process. his is one of the reasons hy it is recommended to plan comprehensive treatment of severe skeletal malocclusions after the patient’s groth is com plete. oever, even after groth completion, the dental arches are also subject to changes related to the patient’s aging, and these processes are in fact lifelong and may result in the development of irregularities in the incisor seg ment that often bring patients back for retreatment.
Retention Protocols and the Choice of Retention Appliance RETENTION PROTOCOLS o date, there is no universal retention protocol, and there is insufcient highuality scientic literature to reliably
A
establish such a protocol in terms of the length of the reten tion phase, the earing regime, and the choice of type of retention device. his is because e cannot generalie a single procedure for patients ho differ in diagnosis, sever ity of the malocclusion, age, type of groth, treatment type, and uality of treatment result. hus the choice of retention device should alays be individualied, ith consideration of all the potential factors of instability men tioned earlier. his approach is called “differential reten tion,” meaning that for every patient, orthodontists must focus and aim the retention on those points that pose the greatest threat and risk of relapse in the individual patient ig. .. According to surveys on retention protocols, the most common retention devices are the aley retainers and clear thermoplastic retainers. or the mandible, a xed retainer is often indicated, either on its on or in combina tion ith a removable appliance. An increasing trend has been observed in the use of thermoplastic retainers, hich patients prefer because of their good aesthetics and inconspicuousness. A similar trend can also be observed ith xed retainers in both jas. In terms of the freuency of use of the various retention devices, an indenite use of xed retainers is recommended by many clinicians.
B
C Fig. 19.1 Examples of relapse after orthodontic treatment, where either the patient failed to wear the retention appliances after rapid maxillary expansion (A-C) or the retention regime selected was insufcient for a noncompliant patient the rotational relapse of lateral incisors
19 • etention and taility ollowing Aligner Therapy
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Fig. 19.1, c’ (-) and palatal moement of upper left canine (-) shown could hae een preented y onding a xed retainer and including prolematic teeth
If the decision is made to use a retention appliance long term, a xed retainer seems to be the best option mainly because it prevents relapse of the aesthetically important anterior teeth very efciently and ithout any need for patient cooperation., onded retainers have also been described in the literature as safe, predictable, and posing no health risks to the patient.,, ome studies, hoever, have indicated that there is a tendency toard increased buildup of plaue and calculus around bonded retainers ig. ., having negative conseuences on the periodon tium hoever, this can be minimied ith regular care, exercised by the patient and a dental hygienist.
he biggest disadvantage of bonded retainers that impacts their longterm or lifelong use is failure rate. According to the literature, the failure rate varies idely, from . to ., oever, e believe that the occur rence of common failures, such as abrasion of the layer of adhesive resin caused by food attrition or occlusal contacts, is only a matter of time ig. .. Other considerable risks associated ith prolonged use of bonded retainers are the socalled unexpected complications, here unexpected tooth movement occurs, even hen the integrity of the bonded retainer has not been compromised in any ay. he incidence of these complications is uite small, occurring
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A
B Fig. 19.2 Calculus accumulation and gingial inammation around the lower onded retainer (A and B)
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D Fig. 19. Examples of failures of onded retainers (A) The detachment of a composite resin layer is usually a conseuence of onding errors (B) The loss of the adhesie layer due to mastication or premature contact on the onded retainer (C) Premature contact on the retainer wire, wire fatigue, or selection of a wire with insufcient mechanical properties (small diameter dead-soft wire) resulting in fracture of the wire () Extending the upper retainer to the canines increases the ris of fracture, with conseuent wire actiation and unwanted tooth moement (Kucˇera J, Littlewood SJ, Marek I. Fixed retention: pitfalls and complications. riti ental Journal ( .
in approximately to of cases,, but their clinical conseuences can be very severe. In addition, it is estimated that up to of such cases reuire retreatment. here are to distinct types ig. ., characteried by a torue difference beteen to adjacent incisors effect or op posite inclination of contralateral canines ist effect.,
hese complications are surprising because they may ap pear after a relatively long period of problemfree retention, often occurring after several years.,, he unanted tooth movement can be so pronounced that the root is moved outside of the alveolar bone ig. ., hich is in many cases accompanied by the occurrence of gingival
19 • etention and taility ollowing Aligner Therapy
A
B
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D Fig. 19. Two distinct types of unexpected complication of lower onded retainers opposite torue on two adacent incisors ( effect A, B) and opposite inclination of contralateral canines (Twist effect C, ) Both effect and Twist effect may e accompanied y seere gingial recession (A, C) (, ro Kucera J, Strelo J, Marek I, et al. reat ent o colication aociated wit lower ed retainer. J Clin Orthod. .
A
B
C
Fig. 19.5 nexpected complication of lower onded retainer (Twist effect) lower left canine moing out of the ony enelope (A-C) ignicant ony dehiscence can e identied on dental cone-eam computed tomography (B, C) (Marek I, Kucˇera, J. Twist-effect, X-effect and other unexpected complications of xed retainers – original article. LKS , (.
26
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Principles and Biomechanics of Aligner Treatment
recession. In such severe cases, orthodontic retreatment is necessary, and often a surgical periodontal intervention may also be needed ig. .. ongterm or lifelong retention is not ithout risk. It should be indicated ith caution, and it is essential that xed retainers are regularly checked by an orthodontist or during regular dental or hygiene checkups. It is also very important that dentists and dental hygienists ho see the patients most freuently are informed about the retention devices used and
their associated risks, no matter ho small. his is especially important for the dental health care providers to help their patients manage because many of the patients consider the orthodontic treatment completed hen the xed appliance is removed, and their regular attendance for checkups at the orthodontic ofce in the retention phase can be a problem ig. .. It is needless to say that early detection of these complications can minimie the damage to adjacent tissues and facilitate the subseuent care.
A
B
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F Fig. 19.6 Treatment of a complication associated with a lower onded retainer (A-C) ower left central and lateral incisors seerely proclined y a fractured onded retainer and lingual gingial recessions occurring on oth incisors (-) etreatment with a full lower xed appliance corrected the torue of the incisors and was followed y a periodontal reconstructie surgery
19 • etention and taility ollowing Aligner Therapy
G
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I Fig. 19.6, c’ (-) inal reconstruction with full porcelain crowns and onding of a new lower xed retainer
100% 90%
Attendance of patients at recall
80% 70% 60% 50% 40% 30% 20% 10% 0% 1
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Years in retention Fig. 19. hen long-term retention is indicated, regular recalls are necessary to chec retainers howeer, attendance of patients decreases in the retention period, as seen on this graph (Fro Kucera J, Marek I. Uneected colication aociated wit andiular ed retainer a retroectie tud. Am J Orthod Dentofacial Orthop .
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APPLIANCES FOR RETENTION AND INDICATIONS OF ARIOUS RETENTION DEICES ased on the biologic principles and knoledge of factors that inuence the position of teeth in the retention phase, several combinations of retention appliances have been recommended. ost often a removable aley retainer ith van der inden labial bo and Adams clasps on the rst molars is used for both the upper and loer jas ig. .. aley retainers are orn largely during the nighttime only. he second option is clear thermoplastic retainers, suitable for both night and daytime ear ig. .. aley retainers are indicated especially for patients ho have need for an increased stabiliation of the canine positions. Other typical indications are patients after transverse expansion or after treatment of a deep bite hen the appliance is also serving as a bite plate. In class II cases here intermaxillary elastics or a bitejumping device as used, an activator ith van der inden labial bo and Adams clasps on maxillary molars ig. . or to clear thermoplastic appliances ith class II precision ings should be considered. In the majority of patients, each of these removable retainers is used in combination ith an upper or loer bonded retainer. onded retainers are most often made of thin multistrand exible steel archires of various strengths and ith various cross sections most of ten the cross section varies beteen . and .in. he ire is shaped and passively attached by a o compos ite resin to all anterior teeth in the loer ja canines and incisors on the lingual surface, preferably in the apical third of
teeth. Alternatively, thick monolament stainless steel, cobalt chromium or titaniummolybdenum ires bonded only to the canines can be used cross section ranges beteen . and . in. In the upper arch, xed retainers most often are limited only to the incisor segment, hile in some patients ith increased need for canine stabiliation e.g., palatally or buc cally impacted canines the canines are also included in the bonded retainer ig. .. he use of xed retainers is par ticularly necessary in patients ith compromised periodontal health, here they also serve as periodontal splints, as ell as in patients ith spacing or midline diastemas, after compli cated space closure folloing extractions, severe tooth rota tions, open bite, or ith impacted canines, or even as a space maintainer before dental implants are placed ig. ..
SPECIFICS OF RETENTION FOLLOING CLEAR ALIGNER TERAPY eneral principles that apply in treatment planning and that fundamentally inuence the occurrence of relapse and the stability of treatment are eually relevant in the treat ment by xed or clear aligner appliance treatment. o ever, the retention phase folloing orthodontic treatment using clear aligners is different to some extent from that folloing use of xed appliances. hen planning retention after clear aligner therapy A, the greatest disadvantage is the complicated achieve ment of nal articulation and intercuspation in the poste rior segments, as opposed to xed appliance treatment, here an ideal occlusal contact can be achieved in the nal
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Fig. 19. awley retainer with frontal ite plane in occlusal (A), front (B), and lateral (C) iews
19 • etention and taility ollowing Aligner Therapy
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B Fig. 19.9 acuum-formed thermoplastic retainer in the upper aw in frontal iew (A) and smile (B)
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Fig. 19.10 etention actiator after class treatment in lateral right (A), frontal (B), and lateral left (C) iews
stage of treatment by use of settling elastics. In A, a posterior open bite often occurs. his may be a conseuence of various factors, including premature anterior contact of incisors ig. . due to insufcient intrusion of loer incisors or incorrect torue of upper or even loer incisors. In addition, the intrusive inuence of masticatory forces on aligners in the posterior segments plays an important role. his situation can be solved by additional aligners never theless, even then a slight open bite often persists. In these
cases, posterior teeth need to be alloed to achieve their best possible contact natural settling ith their antagonists. In this regard, the use of clear aligners for retention may not be appropriate, as it might hinder this natural process entirely, thereby making the settling less effective than hen aley appliances are used ig. .. On the other hand, the abovementioned intrusion effect of clear aligners on the posterior segments is advanta geous hen treating openbite cases. ompared to the
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Principles and Biomechanics of Aligner Treatment
A
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F Fig. 19.11 ifferent types of commonly used xed retainers pper retainers can include incisors only (A), or een oth canines, either continuous (B) or segmented (C) the segmented ersion is more suitale ecause premature contact on the retainer can e aoided, therey decreasing oth the incidence of fracture and the adhesie layer () ower xed retainer usually includes canines and incisors estiular retainers can e used after difcult extraction space closure (E) or as a space maintainer prior to implant placement ()
xed appliance treatment, clinically signicant intrusion of molars and premolars can be achieved even ithout using temporary anchorage devices. hese intrusion movements also seem to be very stable, though valid data to verify this premise are lacking currently ig. . In openbite cases here incisor extrusion is a part of the treatment, it is important that both upper and loer xed retainers extending from canine to canine are used as part of the retention protocol. Additionally, it is essential that
all teeth in the upper and loer arches are included in thermoplastic retainers to prevent unanted eruption of the last molars and conseuent reopening of the bite ig. .. he apparent advantage of A is the nal position of the loer incisors can be predicted very precisely during treatment planning, alloing the clinician to predict and reduce unanted proclination of incisors and thus expected relapse as ell ig. .. herefore functions
19 • etention and taility ollowing Aligner Therapy
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H Fig. 19.12 Examples of typical indication in which use of xed retainers is recommended (A, B) ifcult extraction space closure (C, ) arge midline diastema closure in a periodontally compromised patient (E, ) pace closure in a patient with generalied spacing (, ) eere crowding and tooth rotations
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F Fig. 19.1 (A, B) ateral open ite often occurs after aligner treatment (C, ) The clinical picture at the end of treatment may thus differ when compared to the nal situation depicted in the treatment planning software (E, ) oweer, the clinical situation after years in recall shows that the teeth will eentually settle into the desired position
like grip and superimposition in treatment planning softare should be included in the standard protocol hen planning nonextraction therapy in cases of croding or in class II cases here use of elastics is planned. espite providing exact control of the loer incisor position, xed retainers may still be recommended as the most reliable retention method for stabiliing the position of the loer incisors in the long term. After class II treatment, the use of a retention activator in construction bite or thermoplastic retainers ith precision ings should be considered to maintain the interarch occlusal change. In crossbite cases here transverse expansion as performed, it is more suit able to use a removable retention plate because it is more rigid and maintains the nal transverse dimension better and can be easily adjusted by selective grinding here settling is needed to nalie the articulation.
RETENTION PROTOCOL AND SCEDULE OF CECUPS IN TE RETENTION PERIOD In standard cases the folloing retention protocol is used in our institution In the rare cases hen patients do not have a bonded maxillary xed retainer, fulltime ear of the reten tion appliance for the rst months is recommended this most often involves a thermoplastic retainer during the day and a aley appliance overnight, achieving hours of retainer ear, ith the exception of time that the patient spends eating, drinking, teeth brushing, and possibly partici pating in sport activities after the month period, the patients are then asked to ear retention appliances over night for the rest of the rst year of retention, folloed by every other night in the second year, tice a eek in the third year, and once a eek afterards hen a xed retainer is
19 • etention and taility ollowing Aligner Therapy
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D Fig. 19.1 atural settling of teeth after orthodontic treatment in recall after months, as isualied on T scans of a patient wearing a awley retainer at nighttime (A, B) and a thermoplastic retainer (C, )
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Principles and Biomechanics of Aligner Treatment
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F Fig. 19.15 Treatment of an open ite with aligners that was facilitated y intrusie force in the lateral segments
used, the protocol remains the same, except that the remov able appliance is orn only at nighttime from the beginning. xceptions to the general protocol include groing patients ith sagittal or vertical malocclusions, ho should continue to ear retention appliances until their groth is nished, and patients ho have undergone orthognathic surgery or those ith compromised treatment results, here an increased tendency to relapse may be expected, ho are also recommended a prolonged retention period. atients are instructed to attend regular checkups throughout the retention period. he recommended sched ule is once every or months during the rst year, tice a year in the second year, and at least once a year thereaf ter. urrently there is a tendency to maintain the bonded
retainers indenitely and independently of the original malocclusion but only after a prior agreement ith the patient. atients are instructed that the retention may be discontinued at some point but that their dentition is sub ject to continuous change throughout their lives, and this change may manifest itself in the occurrence of various irregularities in the aesthetically exposed anterior segment. hus patients must either accept the risk of these changes or they must continue ith a bonded or removable retainer if they ant to maintain their teeth alignment. oever, ith due respect to the expected and unexpected complica tions associated ith the prolonged use of a bonded retainer, they need to be checked regularly, at least once a year.
19 • etention and taility ollowing Aligner Therapy
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F Fig. 19.16 elapse of anterior open ite due to short retention thermoplastic retainers and conseuent extrusion of second molars ituation after treatment (A-C) and years in recall (-)
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Fig. 19.1 Treatment planning software can e used to plan the position of lower incisors exactly, aoiding unwanted proclination of the lower incisors and thus preenting the ris of relapse
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Principles and Biomechanics of Aligner Treatment
References . oyers . andboo of Orthodontics for the Student and eneral ractitioner. rd ed. hicago earbook edical ublishers . . amínek . Ortodoncie. st ed. raha alén . . achrisson U, üyükyilma . onding in orthodontics. In raber , anarsdall , ig , eds. Orthodontics Current rinciples and echniues. th ed. hiladelphia, A osby lsevier chap . . achrisson U. ongterm experience ith direct bonded retainers update and clinical advice. J Clin Orthod. . . ooth A, delman , roft . entyyear folloup of patients ith permanently bonded mandibular caninetocanine retainers. Am J Orthod Dentofacial Orthop. . . roft , ields , arver . Contemporary Orthodontics. th ed. t. ouis, O osby lsevier . . eitan . linical and histologic observations on tooth movement during and after orthodontic treatment. Am J Orthod. . . van eeuen , altha , uijpersagtman A, et al. he effect of retention on orthodontic relapse after the use of small continuous or discontinuous forces. An experimental study in beagle dogs. Eur J Oral Sci. . . oese . Increased stability of orthodontically rotated teeth follo ing gingivectomy in acaca nemestrina. Am J Orthod. . . dards . A longterm prospective evaluation of the circumferential supracrestal berotomy in alleviating orthodontic relapse. Am J Orthod Dentofacial Orthop. . . einstein , aack , orris , et al. On an euilibrium theory of tooth position. Angle Orthod. . . de la ru A, ampson , ittle , et al. ongterm changes in arch form after orthodontic treatment and retention. Am J Orthod Dentofacial Orthop. . . Alexander . he Aleander Discipline ongerm tability. anover ark uintessence . . agravére O, ajor , loresir . ongterm dental arch changes after rapid maxillary expansion treatment a systematic revie. Angle Orthod. . . ittle , iedel A, Årtun . An evaluation of changes in mandibular anterior alignment from years postretention. Am J Orthod. . . ahlieke , ischbach , chare . ostretention croding and incisor irregularity a longterm folloup evaluation of stability and relaps. r J Orthod. . . inclair , ittle . aturation of untreated normal occlusions. Am Orthod. . . ishara , reder , amon , et al. hanges in the dental arches and dentition beteen and years of age. Angle Orthod. . . de reitas , anson , de reitas , et al. Inuence of the uality of the nished occlusion on postretention occlusal relapse. Am J Orthod Dentofacial Orthop. .e.e. . achrisson U. Important aspects of longterm stability. J Clin Orthod. . . Aasen O, speland . An approach to maintain orthodontic alignment of loer incisors ithout the use of retainers. Eur J Orthod. . . dman ynelius , etrén , ondemark , et al. iveyear postretention outcomes of three retention methods—a randomied controlled trial. Eur J Orthod. . . achrisson U. Important aspects of longterm stability. J Clin Orthod. . . nlo , uroda , eis A. Intrinsic craniofacial compensations. Am J Othod. .
. slambolchi , oodside , ossou . A descriptive study of mandibular incisor alignment in untreated subjects. Am J Orthod Dentofacial Orthod. . . ehrents . roth in the aging craniofacial skeleton. onograph , raniofacial roth series. Ann arbour enter for uman roth and evelopment University of ichigan . In anda , anda . onsiderations of craniofacial groth in longterm retention and stability is active retention needed Am J Orthod Dentofacial Orthop. . . ittleood . videncebased retention here are e no Semin Orthod. . . ittleood , illett , oubleday , et al. etention procedures for stabilising tooth position after treatment ith orthodontic braces. Cochrane Database Syst Rev. . . ratt , luemper , artseld r , et al. valuation of retention protocols among members of the American Association of Orthodontists in the United tates. Am J Orthod Dentofacial Orthop. . . enkema A, ips , ronkhorst , et al. A survey on orthodontic retention procedures in the etherlands. Eur J Orthod. . . oland , ichens , illiams A, et al. he effectiveness of aley and vacuumformed retainers a singlecenter randomied controlled trial. Am J Orthod Dentofacial Orthop. . . ai , rossen , enkema A, et al. Orthodontic retention procedures in iterland. Swiss Dent J. . . admos A, udalej , enkema A. pidemiologic study of orthodontic retention procedures. Am J Orthod Dentofacial Orthop. . . Årtun , padafora A, hapiro A. A year folloup study of various types of orthodontic caninetocanine retainers. Eur J Orthod. . . enkema A, enkema A, ronkhorst , et al. ongterm effectiveness of caninetocanine bonded exible spiral ire lingual retainers. Am J Orthod Dentofacial Orthop. . . Årtun . aries and periodontal reactions associated ith longterm use of different types of bonded lingual retainers. Am J Orthod. . . andis , lahopoulos , adianos , et al. ongterm periodontal status of patients ith mandibular lingual xed retention. Eur J Orthod. . . ogers , Andres . ependable techniue for bonding a x retainer. Am J Orthod Dentofacial Orthop. . . törmann I, hmer U. A prospective randomied study of different retainer types. J Orofac Orthop. . . ucˇera , arek I. Unexpected complications associated ith mandibular xed retainers a retrospective study. Am J Orthod Dentofacial Orthop. . . atsaros , ivas , enkema A. Unexpected complications of bonded mandibular lingual retainers. Am J Orthod Dentofacial Orthop. . . arek I, ucˇera . isteffect, effect and other unexpected complications of xed retainers. LS. . . aera , udalej , atsaros . evere complication of a bonded mandibular lingual retainer. Am J Orthod Dentofacial Orthop. . . ucˇera , treblov , arek I, et al. reatment of complications associated ith loer xed retainers. J Clin Orthod. . . rátná , arek I, ycová . ettling after orthodontic therapy according to type of retention. Ortodoncie. . . annessy , arvey , AlAadhi A. A randomied clinical trial comparing mandibular incisor proclination produced by xed labial appliances and clear aligners. Angle Orthod. .
20
Overcoming the Limitations of Aligner Orthodontics: A Hybrid Approach LUCA LOMBARDO and GIUSEPPE SICILIANI
Introduction Aligners were rst introduced by Kesling1 in 1945 to correct crowding. Later, Ponitz2 reorted te use o a reoable lastic retainer ssi, entsly, or, PA, A. oweer, it was not until te 199s, wen eridan et al. cobined tese retainers wit interroial reduction P, tat tey began to gain oularity. en, in 1999, ia isti and Kelsey irt, togeter wit a couter secialist, ounded Align ecnology in Palo Alto, A, A.4 ince tey launced teir nisalign brand into te aret, te deand or ortodontic aligners as been growing aong atients esecially adults, tans to teir estetic roerties and clinical ecacy.5 At rst, aligners were areted as an alternatie to traditional ed aliances in sile alocclusion cases inoling sligt crowding or inor sace closure. er tie, oweer, te range o alocclusion cases tat can be treated by eans o inisible aligners as broadened. linical researc as deeloed aligner-based solutions or een cole cases inoling aor rotation o te reolars, uer incisor torue, distalization, andor etraction sace closure. esite te claied eciency o aligner treatent, oweer, its clinical otential still reains controersial aong clinicians. ts adocates are coninced by te clinical eidence arising ro successully treated cases, wile setics oint to te signicant liitations o te tecniue, esecially in te treatent o cole alocclusions.-11 rtodontics coanies clai tat aligners can resole, witout te use o additional tecniues, rotations o 4 degrees at te uer and lower central incisors, 45 degrees in canines and reolars, degrees in lateral incisors, and 2 degrees in olars. trusions and intrusions o 2.5 ae been acieed in anterior teet, and root oeents o 4 and 2 ae been reorted in osterior teet.12 eerteless, ew studies ae been ublised to suort tese clais, wic are not always suorted by te eerience o oter clinical ractitioners. n act, soe ortodontists indicate tat te nuber o atients wo reuire soe unlanned correction or een recourse to ed ortodontics is closer to to .5 1 Kraitz reorted tat nisalign aligners ad a ean accuracy o 41 in ters o acieing lanned outcoes, wit te ost redictable oeent being lingual contraction 4.1 and te least redictable etrusion 29..14
n te attet to clariy te situation, Lagraère and lores-ir15 ublised te rst systeatic reiew on te subect in 25. ince ten, seeral autors ae roided udated eidence on aligner ecacy.12,1-1 e ost recent systeatic reiews into te accuracy o ortodontic oeents acieable wit aligners ae concluded tat tey are able to roduce distal oeent o te uer olars and resole anterior crowding issues troug incisor rotrusion and by increasing te intercanine, interreolar, and interolar distances. n te oter and, reoable aligners are ar less eectie at acieing transerse eansion ia bodily oeent o te osterior teet. urterore, tey are unable to eror canine and reolar rotations satisactorily, and see to all sort in ters o etrusion oeents and control o oerbite and occlusal contacts. earing in ind tis eidence, our clinical eerience, and te eer-growing oularity o aligner treatent, we ae deeloed a new ybrid aroac using a cobination o dierent deices to oercoe soe o te ost coon liitations o reoable aliances.
Transverse Expansion of the Posterior Teeth esearc as sown tat aligners are unable to eror redictable bodily reolar and olar eansion. igital setus tend to oerestiate bodily eansion oeents, and ore tiing tan lanned occurs.19-21 oweer, in clinical cases ig. 2.1 in wic te osterior sectors are greatly negatiely inclined, it is ossible to lan uncontrolled tiing o te uer and lower canines, reolars, and olars. urterore, te sace needed to resole crowding can be created by using aligners alone ig. 2.2 to eert ressure on te lingual suraces o te teet tis iroes te arcor by signicantly increasing te intercanine, interreolar, and interolar distances ig. 2.. n act, Lobardo et al.22 ae deonstrated tat tis estibulolingual tiing can be acieed wit a redictability o 2.9. at being said, in young atients wit transerse decits due to yolasia o te uer aw ig. 2.4, it is not realistic to eect aligners to aciee seletal alteration. nly an ortoedic aroac, rst on te deciduous teet ig. 2.5 and ten ia seletal ancorage2 ig. 2., is able to noralize te aillary diensions and tereore 275
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Fig. 20.1 Initial intraoral photographs of adult patient with class I malocclusion dentoalveolar contraction in both arches.
Fig. 20.2 Intraoral photographs during aligner therapy with composite buttons.
20 • Overcoming the Limitations of Aligner Orthodontics: A ybrid Approach
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Fig. 20.3 inal intraoral photographs after step aligner treatment.
erit correct erution and iroe te transerse and sagittal occlusal relationsis. oweer, in suc atients, aligners ig. 2. can be used as an ecacious tool or coleting dental alignent and creating accetable intercusidation witout decoensating te class alocclusion ig. 2.. t is not only in cildren tat suc robles arise, oweer in adult atients,24 te redictability o transerse eansion ia bodily oeent o te reolars and olars is oor, and ay be daaging in atients wit tin eriodontal tissues or gingial recession ig. 2.9. ence in adults it is best to resole issues o seletal aillary contraction ia surgery or seletal ancorage eanders bone-bone raid
alatal eander ig. 2.1. nly ater te transerse decit as been resoled sould crowding be addressed, and in suc cases te occlusion can be iroed by eans o aligners ig. 2.11, wic can guide te etrusion o te teet in a controlled asion. is aroac lessens te ris o reature contacts, unwanted estibular oeent, and worsening gingial recession ig. 2.12.
Canine and Premolar Rotation t as been deonstrated tat te andibular canine is te ost dicult toot to control wit aligners and tat te
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Fig. 20.4 Initial intraoral photographs of a young patient with sel etal and dental class III and narrow upper aw.
Fig. 20.5 apid palatal epansion with arms for elaire mas on de ciduous second molars.
Fig. 20.6 ybrid epander with dental and seletal anchorage in up per aw and arms for elaire mas.
20 • Overcoming the Limitations of Aligner Orthodontics: A ybrid Approach
Fig. 20.7 Intraoral photograph during aligner therapy.
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aount o rotation actually acieable wit te aillary and andibular canines is rougly a tird o tat redicted.25 or reolars, te rotation accuracy o aligners as been reorted witin te range 2.2 to 41..2 e diculty in derotating cylindrical teet by eans o aligners is liely due to te act tat tey are unable to gri tese teet suciently to generate a orce coule. is ay be ascribable to oor aligner tting andor ecessie stiness o te aliance itsel. uerous otential solutions to tis roble ae been roosed in recent years. or eale, in a case o crowding wit a seerely rotated lower canine and uer incisor ig. 2.1, coosite buttons were alied on te lingual side o te aligner ig. 2.14 to increase te gri, and derotation was lanned in only 2 stes. e good elasticity2 and t ig. 2.15 o 22 aligners weden artina, ue arrare, taly, in addition to careul striing,
Fig. 20.8 inal intraoral photographs after step aligner treatment.
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Fig. 20.9 Initial intraoral photographs of adult patient with seletal contraction of upper aw class III tendency and gingival recession in both arches.
Fig. 20.10 apid palatal epansion with seletal anchorage APA method.
Fig. 20.11 Intraoral photograph during aligner therapy.
20 • Overcoming the Limitations of Aligner Orthodontics: A ybrid Approach
Fig. 20.12 inal intraoral photographs after aligner therapy.
Fig. 20.13 Initial occlusal intraoral photographs of an adult patient with severe rotation of the upper incisors A and right lower canine B.
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Fig. 20.14 Occlusal intraoral photographs during treatment with composite buttons on the lingual surfaces of teeth . . . and ..
Fig. 20.15 Intraoral photograph during aligner therapy.
roided satisactory alignent, witout recourse to ultile reneents, witin a liited tierae ig. 2.1. e ae recently deeloed a new ybrid aroac to increase te redictability o rotations, wic is one o te aor liitations o aligner treatent.1-1 n cases o rotations o 2 degrees or aboe ig. 2.1, it is ossible to include icrotubes wit a circular cross section in te setu to be ositioned across te lingual surace o te rotated teet ig. 2.1. e setu can be erored in suc a way tat te aligners coer tese sections witout actually toucing te ig. 2.19. is enables te clear aligner to guide te oeent o te teet, eliinate unwanted oeents, and increase atient coort. y tese eans we acieed correct rotation in only 1 stes witout any reneents or
Fig. 20.16 inal intraoral photographs after step aligner treatment.
20 • Overcoming the Limitations of Aligner Orthodontics: A ybrid Approach
Fig. 20.17 Initial photographs of a young patient with rotation greater than degrees of left upper canine and left second premolar.
Fig. 20.18 Application of microtubes on rotated mesial and distal teeth.
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Fig. 20.19 Occlusal photographs. A pper arch with thermal iTi . sectional. B pper arch with aligner covering thermal iTi . sectional. Lower arch with thermal iTi . sectional. Occlusal photograph of lower arch with aligner covering thermal iTi . sectional.
coosite buttons. n oter words, tis ybrid aroac enabled us to iroe bot redictability and treatent tie ig. 2.2.
Extrusion, Intrusion, and Overbite Control According to Kraitz,14 etrusion and intrusion are aong te least redictable oeents acieable wit clear aligners only 29. etrusion and 41. intrusion o te oeents lanned in te setu are acieed at te end o aligner treatent. oe autors ae deonstrated tat it is ossible to aciee anterior bite closure using clear aligners,14 but in te aority o cases tis will inole uncontrolled lingual tiing o te uer and lower incisors, acieed ia sace creation troug P and transerse aillary eansion. e diculty in acieing ure etrusion is liely due to te oor gri o te aligners on cylindrical teet, wic ay be iroed by te alication o coosite buttons. oweer, we ae also ad soe success in oercoing tis bioecanical liitation, resoling oen bite using auiliaries eiter beore or during aligner
teray. e ae ound, or eale, wen oen bite in growing atients is due to bad abits tub-sucing and as already caused seletal alterations aillary contraction ig. 2.21, it is better to ot or an ortoedic aroac bite-bloc eander wit grille ig. 2.22 to noralize te uer aw and allow correct erution o te uer incisors ig. 2.2. en, once tese iroeents ae been acieed, aligners are te ideal solution or rening te occlusion ig. 2.24, guiding te eruting teet into teir roer ositions witin a liited tierae and wit inial unwanted eects ig. 2.25. At te oosite end o te sectru, dee bite ig. 2.2 cannot generally be resoled by eans o aligners alone, as intrusion o te uer and lower incisors is unredictable, once again resuably due to oor gri on te ancoring teet. ence, in all cases in wic it is indicated class , not ecessie estibular oeent o te lower incisors, it ay be ery useul to eloy class elastics ig. 2.2. e eects o tese deices tat are coonly seen as undesirable lower olar etrusion and estibular oeent o te lower incisors enable rotation o te occlusal lane, areciably aiding oening o te bite, and allow correction o te sagittal relationsis ig. 2.2.
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Fig. 20.20 inal intraoral photographs after sevenstep aligner treatment.
Fig. 20.21 Initial intraoral photographs of young patient with ante rior open bite and maillary contraction.
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Fig. 20.22 Bitebloc epander with anterior grille.
Fig. 20.23 rontal intraoral photograph after the rst stage of treat ment with palatal epander and grille.
Fig. 20.25 inal intraoral photographs after step aligner treatment.
Fig. 20.24 Intraoral photograph during aligner therapy.
olar istaliation t as been deonstrated tat aligners are able to distalize te uer olars wit a ery ig degree o ecacy rougly wen te etent o te lanned oeent is around 2.5 .2 oweer, our clinical eerience as
sown tat bodily olar distalization is not, in act, acieable by eans o aligners, as tey roide only ery liited root control. ln 215, ang29 deonstrated, in a study o 2 atients wo underwent cone-bea couted toogray beore and ater aligner treatent, tat irresectie o te tye o ortodontic oeent lanned, wat was acieed were large crown oeents but ery sall root oeents. is ade it clear tat te aligners were acting to tilt te teet rater tan oe te bodily. it tis in ind, in olar distalization cases ig. 2.29, it is reerable to lan derotation around te alatal root, wit distal inclination o te crown rater tan bodily oeent. Knowing tat derotation o te uer olar is not sucient to correct class , and ay cause ancorage loss, it is better to eloy class elastics ig. 2.. e eect o tese elastics is to esially incline te teet in te lower arc, reenting te uer canines and incisors ro oing esially ig. 2.1.
20 • Overcoming the Limitations of Aligner Orthodontics: A ybrid Approach
287
Fig. 20.28 inal intraoral photographs after step aligner treatment. Fig. 20.26 Initial intraoral photographs of a young patient with deep bite and class II.
Fig. 20.27 Lateral intraoral photograph during aligner therapy com bined with class II elastics.
Fig. 20.29 ight initial intraoral photograph of a patient with class II subdivision and contraction of the upper aw.
288
Principles and Biomechanics of Aligner Treatment
Fig. 20.30 Lateral intraoral photograph during aligner therapy com bined with class II elastics. Fig. 20.33 apid palatal epansion and pendulum with seletal an chorage APA method.
Fig. 20.31 ight lateral intraoral photograph lateral after aligner treatment.
A
B Fig. 20.32 Left initial intraoral photograph of a patient with class II subdivision and contraction of the upper aw.
at being said, tere are cases in wic te class is so seere tat olar distalization alone is not sucient to resole sagittal issues. n tis atient ig. 2.2, or eale, it would be unrealistic to eect to aciee - distalization ia bodily oeent wit aligners. ence we decided to eand te uer aw using a raid alatal eander ancored to our iniscrews, ositioned using te
Fig. 20.34 Lateral intraoral photographs during aligner therapy A and combined with class II elastics B.
APA etod,1- in cobination wit a onolateral endulu ig. 2.. is aroac enabled us to resole rst te transersal issues and ten te sagittal, uicly, unobtrusiely, and witout te need or atient coliance. nce class ad been acieed, a series o 14 aligners was lanned to close te saces in te uer arc and coordinate te arces ig. 2.4. n tis case, te alication o aligners in cobination wit class elastics on te rigt
20 • Overcoming the Limitations of Aligner Orthodontics: A ybrid Approach
Fig. 20.35 Left lateral intraoral photograph after aligner therapy.
side to roote distalization o te uer reolars and canines enabled us to treat te alocclusion wit satisactory results oer a sort eriod o tie ig. 2.5.
Conclusions e scientic and clinical eidence now sows tat aligners are able to resole alocclusion in a growing nuber o cases. n te oter and, teir liitations in ters o acieing transerse eansion ia bodily oeent as been aly docuented. t also aears tat tey are unable to redictably derotate canines and reolars. at is ore, liitations ae been described or etrusion and intrusion oeents and control o oerbite and occlusal contacts. n te basis o tese ndings, and te nowledge tat te solution to tese robles cannot be an endless series o aligners, we roose a ybrid aroac cobining aligner teray wit dierent ortodontic deices to roide satisactory and redictable clinical outcoes.
References 1. Kesling . e ilosoy o toot ositioning aliance. Am J Orthod. 1945129-4. 2. Ponitz . nisible retainers. Am J Orthod. 191592-22. . eridan , Leou , cinn . ssi retainers abrication and suerision or eranent retention. J Clin Orthod. 1992-45. 4. oucez . Clinical Success in Invisalign Orthodontic Treatment. Paris uintessence nternational 21. 5. eridan . e readers’ corner 2 wat ercentage o your atients are being treated wit nisalign aliances J Clin Orthod. 24544-545. . oe L. nisalign early eeriences. J Orthod. 24-52. . aldwin K, King , asay , et al. Actiation tie and aterial stiness o seuential reoable ortodontic aliances. Part reolar etraction atients. Am J Orthod Dentofacial Orthop. 2 1-45. . Kraitz , Kusnoto , eole , et al. ow well does nisalign wor A rosectie clinical study ealuating te ecacy o toot oeent wit nisalign. Am J Orthod Dentofacial Orthop. 291512-5. 9. oac . our-reolar etraction treatent wit nisalign. J Clin Orthod. 2449-5. 1. oac , ay . urgical-ortodontic treatent using te nisalign syste. J Clin Orthod. 24242-245.
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11. Kaatoic . A Retrospective Evaluation of the Effectiveness of the Invisalign Appliance Using the PAR and Irregularit Indices. oronto niersity o oronto anada 24. 12. alan-Loez L, arcia-onzalez , Plasencia . A systeatic reiew o te accuracy and eciency o dental oeents wit nisalign. orean J Orthod. 2194914-149. 1. oyd L. ncreasing te redictability o uality results wit nisalign. Proceedings of the Illinois Societ of Orthodontists. a roo 25. 14. Kraitz , Kusnoto , eole , et al. ow well does nisalign wor A rosectie clinical study ealuating te ecacy o toot oeent wit nisalign. Am J Orthod Dentofacial Orthop. 29152-5. 15. Lagraère , lores-ir . e treatent eects o nisalign ortodontic aligners a systeatic reiew. J Am Dent Assoc. 251124-129. 1. ossini , Parrini , astroªorio , et al. cacy o clear aligners in controlling ortodontic toot oeent a systeatic reiew. Angle Orthod. 21551-9. 1. ossini , Parrini , astroªorio , et al. Periodontal ealt during clear aligners treatent a systeatic reiew. Eur J Orthod. 21559-54. 1. eng , Liu , i , et al. ciency, eectieness and treatent stability o clear aligners a systeatic reiew and eta-analysis. Orthod Craniofac Res. 21212-1. 19. olano-endoza , onneberg , olano-eina , et al. ow eectie is te nisalign syste in eansion oeent wit ’ aligners Clin Oral Investig. 21215145-144. 2. oule P, Piedade L, odescan r , et al. e redictability o transerse canges wit nisalign. Angle Orthod. 21119-24. 21. uscang P, oss , aw , et al. Predicted and actual endo-treatent occlusion roduced wit aligner teray. Angle Orthod. 215552-2. 22. Lobardo L, Arregini A, aina , et al. Predictability o ortodontic oeent wit ortodontic aligners a retrosectie study. Prog Orthod. 21115. 2. aino , urci , Arregini A, et al. eletal and dentoaleolar eects o ybrid raid alatal eansion and aceas treatent in growing seletal class atients. Am J Orthod Dentofacial Orthop. 211522-2. 24. Lobardo L, arlucci A, aino , et al. lass alocclusion and bilateral cross-bite in an adult atient treated wit iniscrewassisted raid alatal eander and aligners. Angle Orthod. 21549-4. 25. Kraitz , Kusnoto , Agran , et al. nªuence o attacents and interroial reduction on te accuracy o canine rotation wit nisalign. A rosectie clinical study. Angle Orthod. 24 2-. 2. ion , Keilig L, cwarze , et al. reatent outcoe and ecacy o an aligner tecniue—regarding incisor torue, reolar derotation and olar distalization. C Oral ealth. 21414. 2. Lobardo L, Arregini A, artines , et al. tress relaation roerties o our ortodontic aligner aterials a 24-our in itro study. Angle Orthod. 21111-1. 2. uarneri P, lierio , ilestre , et al. en bite treatent using clear aligners. Angle Orthod. 21591-919. 29. ang , e L, uo , et al. ntegrated tree-diensional digital assessent o accuracy o anterior toot oeent using clear aligners. orean J Orthod. 2154525-21. . Lobardo L, olonna A, arlucci A, et al. lass subdiision correction wit clear aligners using interaillary elastics. Prog Orthod. 211912. 1. aino , Paoletto , Lobardo L, et al. APA a new ig-recision etod o alatal iniscrew laceent. EJCO. 215241-4. 2. aino , Paoletto , Lobardo L, et al. A tree-diensional digital insertion guide or alatal iniscrew laceent. J Clin Orthod. 215112-22. . aino , Paoletto , Lobardo L, et al. ro lanning to deliery o a bone-borne raid aillary eander in one isit. J Clin Orthod. 2151419-2.
Index age numbers folloe by “f” inicate gures an “t” inicate tables
A Afferent bers, 253 Aging, of polymers, 30 Align appliance, 125–126, 125f, 126f Aligner auxiliaries, 43–47 attacments an pressure areas, 43–45, 44f interproximal reuction, 45–46 intraoral elastics, 45 temporary ancorage eices, 47 iscoloration, 36 extrusion, 1–1, 1f, 1f plastics, 17 Aligner material properties clinical loaing patterns, 40–41, 40f longterm loaing, 37–40, 3f, 40f mecanical properties, 35 optical canges, 36, 36f optical material canges, 35 sortterm mecanical loaing multiple cycle, 37, 3f occlusal forces, 37 single, 36–37, 37f ater absorption, 35, 36f Aligner ortoontics ancorage, 47 application, 13 attacments, 13 basic attacment congurations anterior extrusion, 1–1, 1f, 1f rstorer control, 1–21, 20f, 21f posterior intrusion, 1, 1f seconorer control, 21–23, 21f, 22f, 23f, 24f tirorer control, 24–26, 24f, 25f, 26f, 27f, 2f ertical control, 17 biologic consierations, 4–4 biomaterials, 13 functions eliering preetermine force ectors, 17, 17f, 1f proiing aligner retention, 16, 16f slipping aoi, 16, 17f geometry, 13, 15f ybri approac canine an premolar rotation, 277–24, 21f, 22f, 23f, 24f, 25f extrusion, intrusion, an oerbite control, 24, 25f, 26f, 27f molar istaliation, 26–2, 27f, 2f, 2f transerse expansion, 275–277, 276f, 277f, 27f, 27f, 20f, 21f improements, 13 location, 14–15, 15f, 16f in prerestoratie patients, 16–1 seuentialiation, 47 sie, 15 translucent composites, 13 Aligner planning softare, 11–14 Aligner “slipping,” 16, 17f Alignertoot mismatc, 13, 14f American ental Association ouncil on cientic Affairs A, 6 Ancorage management, 47
290
Anterior open bite biomecanics, for correction, 5 iagnosis, 5 treatment alternaties, , 104 attacments, 6–7, 6f, 7f linec softare esign, 5–6 obecties, , 100t, 104, 105t plan, , 104, 105f results, 100–102, 101f, 102f, 102t, 105, 106f, 107f, 10f, 10t seuence, –100, 100f, 105, 106f Arc eelopment, class malocclusions treatment plan, 51
B eneslier, clinical proceure an rational of, 10–11, 11f icuspis, it plastic aligners, 1 iomaterials, for attacment fabrication, 13 iomecanical conentional attacment, class malocclusions treatment plan, 51, 52f olton analysis, 53 racetbase biomecanics, 21 uccal tipping, 25, 25f
C alcitonin generelate peptie , 252–253 anine impaction aerse seuelae of, 14 clinical case, 157–15, 15f, 15f, 162f, 163f, 164f, 165f, 166f early iagnosis an treatment, 14–153, 152f, 153f late iagnosis, 153–154, 154t patologic conition, 14 prealence, 14 treatment, 14–153, 152f, 153f planning, 154–157, 154f, 155f, 156f arriere otion 3 Appliance A, 137, 13 A See lear aligner terapy A See onebeam compute tomograpy epalometric analysis, 3, 7, f erical ertebral maturation , 121 emical aging, of polymers, 30, 32–33 lass elastics, 10 lass malocclusions, 123–126, 125f, 126f clinical protocol, 67–6 elastic effect, 67 extractions, 67 ybri approac in case report, 13–13, 13f, 140f, 141f, 142f, 143–146, 143f, 144f, 145f, 146f, 147f it istaliing eice, 137–13 manibular aancement, 67 maxillary istaliation, 6–7, 6f, 70f, 72f, 73f, 74f, 75f, 76f, 77f, 7f, 0f maxillary molar istaliation, 66–67 maxillary molar rotation, 67 ortognatic surgery, 67 terapeutic options, 66
lass malocclusions, 51 entoaleolar iscrepancy, 52, 52f, 53f, 54f iagnosis, 51 morpologic iscrepancy, 5–60, 61f, 62f, 63f preprostetic nee, 60–62, 64f toot sie iscrepancy, 53–56, 55f transerse iscrepancy, 56–5, 56f, 57f, 5f, 5f treatment, 51–52 lear aligner terapy A, 137, 252 case stuy, 240–244, 241f, 242f, 243–244f, 245f, 246f, 247f, 24f, 24f, 250f complex moements, 42 funamentals recap, 4 it nisalign, 235 patient compliance, 4 surgery rst, 237–240 teoretical an practical consierations, 43–4 analysis of moements occurring, 43–4 nal position analysis, 43, 43f transitioning, 237, 23–23f, 23f, 23f, 240f it irtual setup softare, 210 lear aligner treatment A class malocclusions, 66 of croing, 52 linec softare, 6–6, 3 esign, 5–6 tools, 52f treatment plan, 1f omplementary force ectors, 17, 17f omputerassiste esigncomputerassiste manufacturing AA, 1 onebeam compute tomograpy , 1, 2f, 153 aantages, 5 AAA, 5 AAA concept, 5 benets, 6–7, 6f, 7f, f, f, 10f cepalometrics, 5 it conentional panoramic examinations, 6 loose raiograpic proceures, 5–6 ortoontic iagnosis an treatment planning, 5 ortognatic surgery, 7 upper airay, 7 onentional attacments, of aligner auxiliaries, 44, 44f onentional bracet tecniues ortoontic toot moement it, 13, 14f torue moication of, 24, 24f reep, 17, 33, 37 ure of pee, 10–110, 110f
D eep bite case report, 111–114, 111f, 112f, 113f, 114f, 115f, 116f, 117f, 11f, 11f, 120f correlation beteen, 10 cure of pee leel, 10–110, 110f enition, 10 treatment strategies, 10 upper incisors leel, 110–111
Index
ental arces, 3 entoaleolar iscrepancy, 52, 52f, 53f, 54f entofacial ortopeics, 1 ifferential scanning calorimetry , 32 igital maging an ommunications in eicine , 7 igital imaging tecniues, 11, 11f igital impressions, 3 igital moels, 1–5, 3f igital smile esign , 16 istaliation, 67 ouble conentional attacment, 54f uplex, 56
abial impactions, 157 aser scanning, 7– eone appliance, 125, 125f oss of tracing, 17
M
lastic aligner eformation, 13, 14f lastic effect, of class malocclusions, 67 lastic ear, 67 namel, 3–5 stetic analysis, 16 tanol, 31–32 olution, 1 xtraction iagnosis, 3, 4f, 5f, 6f of posterior teet, 5 treatment plan, 3 progress, 3–7, 7f, f, f, 0f results, 7–1, 1f, 2f, 3f
alocclusion, 1 anibular aancement, 126–132, 127f, 12f, 130f, 132f, 133f, 134f pase, 126 anibular xation, 236–237 axillary istaliation, 6–7, 6f, 70f, 72f, 73f, 74f, 75f, 76f, 77f, 7f, 0f axillary expansion , 121–122, 122f axillary molar istaliation, 66–67 axillary molar rotation, 67 axillary transerse eciency, 6 esioistal moements, 210 iniimplants, 10 olar istaliation aligner ortoontics, in ybri approac, 26–2, 27f, 2f, 2f upper in aligner treatment, 10 clinical case, 11–200, 12f, 13t, 14f, 15f, 16f, 17f, 1f, 200f clinical consierations, 200 olars, it plastic aligners, 1 ucogingial unction , 157
F
N
abrication process, 32 acial treeimensional scan, 2f eer aligners, 67 inite element analysis A, 15, 20–21 inite element meto , 44–45 ree gingial graft , 205–207 urcation efects, 207–20
ational ommission on aiation rotection an easurements, 5 ear infrare tecnology, 3–5, 4–5f
E
G ingial creicular ui biomarers, 125 lass transition temperature, 32 lassy material, 31–32
H an an rist maturation , 121 orsesoesape geometry, 25–26 ygroscopic expansion, 35
I ncisor control, class malocclusions treatment plan, 51 nsufcient force leels, 25–26, 26f, 27f, 2f nterceptie ortoontics, 121 case reports, 122–123, 123f, 124f, 124t maxillary expansion, 121–122, 122f ntermaxillary elastics, 16 nterproximal contacts, 11 nterproximal enamel reuction , 45–46 nterproximal reuction, class malocclusions treatment plan, 51–52 ntraoral scans s, 1–5, 3f nisalign aligners, 13–13 nisalign system, 3
L abial xe ortoontic appliances, 236–237, 236f
O penbite treatment alternaties, , 104 attacments, 6–7, 6f, 7f linec softare esign, 5–6 for correction, biomecanics, 5 obecties, , 100t, 104, 105t plan, , 104, 105f results, 100–102, 101f, 102f, 102t, 105, 106f, 107f, 10f, 10t seuence, –100, 100f, 105, 106f ptimie attacments, of aligner auxiliaries, 44, 44f ptimie oot ontrol Attacments, 22 rtoontic applications, in polymers, 30 rtoontic pain biologic mecanisms of, 252–253 in clear aligner terapy, 253–254 clinical consierations, 255–256, 256t clinical correlates, 252–253 importance of, 252 psycological factors, 254–255 rtoontics, 1 aances in, 16 aligner, 1 iagnosis, 1, 2f igital eolution in, 1 2 imaging moalities, 5–6 rtoontic toot moement , 42 staging, 47–4 rtoontic treatment See etention rtoontists, 42 rtognatic surgery, 7, 67, 235 rtopantomograpy , 116f, 120f, 14, 152f rtoulse, 1–3 ererupte molars, 17
291
P ain, 252 alatal impactions, 157 alatally isplace maxillary canine teet, 14 anoramic xray, 147f atologic toot migration , 202 enulum appliance, 13 erioontal isease clinical case, 214–220, 215f, 216f, 217f, 21f, 21f, 221f, 222f, 223f, 224f, 225f, 226f, 227f, 22f, 22f, 230f, 231f iagnosis, 205–210 malocclusions relate to, 202, 203f optimal control, 210–214 ocart, 214 mesioistal moements, 210, 212f ertical moements, 213–214, 213f estibulolingual moements, 213 ortoontic moements, 210–214, 212f ortoontic treatment in, 202, 204f retention, 214 treatment planning multiisciplinary team, 205 ortoontic assessment, 20, 20t, 20f, 211f, 212f patient expectations, 205, 205f perioontal assessment, 205–20, 205t, 206f, 206t erioontal ligament strain, 22, 22f erioontitis graes, 205t, 220t stages, 206t, 21t See olyetylene tereptalate glycol ysical aging, of polymers, 30, 32–33 lastic foil, 210 lastic materials, 42 olyetylene tereptalate glycol , 31, 35 material, cemical structure of, 31f olymers cemical aging, 30, 32–33 enition, 30 materials, 30 mecanical stability, 30 molecular structure, 30–32, 31f in ortoontic applications, 30 pysical aging, 30, 32–33 termal properties, 30–32 olyuretane , 31 material, cemical structure of, 31f re–manibular aancement pase, 126 See olyuretane
R api maxillary expansion , 121, 122 etention appliances, 266, 266f, 267f, 26f, 26f in ortoontic treatment, 25–260 protocol, 260–261f, 260–264, 262f, 263f, 264–265f, 265f, 270–272 specics, 266–270, 270f, 271f, 272f, 273f eolution, 1 otation control, class malocclusions treatment plan, 51 unner, 125, 125f
S euentialiation, 47 eere entofacial eformity, 235
292
Index
lo maxillary expansion , 122 oft tissue ata extraction, 7– pace management in anterior region, 16–16 case stuy, 16–170, 16f, 170f, 171f, 172f, 173f in posterior region, 170–174, 175f, 176f, 177f, 17f pecic olume, 31 plintaie maxillary, 236–237 tability, 25–260 tereopotogrammetry, 7– tress relaxation, 17, 37–3, 40f ubepitelial connectie tissue graft , 205–207 upercoole region, 31–32 urgery rst, it aligner terapy, 235–251
T angential forces, 16, 17f eet segmentation, emporary ancorage eices As, 47, 5, 157 emporomanibular isorers s case stuy, 10–14, 10f, 11f, 12f, 13f, 14f, 15f, 16f, 17f, 1f iagnosis, 17–10 management, 17 treatment plan, 17–10
emporomanibular oint , 7 ensile measurements, 37–3 ermoplastic aligner materials, 40 ermoplastic polymers, 31 ermoplastic polyuretane , 35 oontics See Aligner ortoontics 3 ata integration, 11, 11f 3 facial reconstruction tecniues, 7–, 10f 3 imaging conebeam compute tomograpy, 5–6 benets, 6–7, 6f, 7f, f, f, 10f 3 ata integration, 11, 11f 3 facial reconstruction tecniues, 7–, 10f irtual setup, –11, 11f s See emporomanibular isorers s oot alignment after aligner seuence, 13, 14f an leeling, 11 oot isplacement patterns, of posterior teet, 22, 22f oot sie iscrepancy, 53–56, 55f oottootgingia segmentation, orue moication, of anterior teet, 24 racing superimposition, 116f ransition pase, 126 ranserse eciency correction of, 24 maxillary, 6
ranserse iscrepancy, 56–5, 56f, 57f, 5f, 5f umor necrosis factora a, 252–253
U pper molar istaliation See also olar istaliation in aligner treatment, 10 clinical case, 11–200, 12f, 13t, 14f, 15f, 16f, 17f, 1f, 200f clinical consierations, 200 prigting moment, of posterior teet, 22f
V ertical moements, 213–214 estibulolingual moements, 213 iscoelasticity, 31–32 iscoelastic material, mecanical beaior of, 37
W ater absorption, of aligner material properties, 35, 36f it of eratinie gingia , 20
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