Principles and Biomechanics of Aligner Treatment PDF
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University of Connecticut Health Center
2022
Ravindra Nanda,Tommaso Castro,Francesco Garino,Kenji Ojima
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This book covers principles and biomechanics of aligner treatment. It is written by orthodontists from several countries and focuses on the technical aspects of the topic.
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Access to the eBook is limited to the first individual who redeems the PIN, located on the inside cover of this book, at expertconsult.inkling.com and may not be transferred to another party by resale, lending, or other means. 2020_PC PRINCIPLES and BIOMECHANICS of ALIGNER TREATMENT This page intentionally left blank 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, ISBN: 978-0-323-68382-1 FIRST EDITION Copyright © 2022 by Elsevier, Inc. All rights reserved. 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 con- tributors 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: 9 8 7 6 5 4 3 2 1 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 Researcher and Aggregate Professor Ulm University Department of Clinical Sciences and ranslational Ulm, Germany edicine University of ome “or ergata” Sean K. Carlson, DMD, MS ome, taly Associate Professor Department of Orthodontics uan Palo ome Arano, DDS, MSc School of Dentistry, University of the Pacic Associate Professor San Francisco, California, USA Orthodontics Program Universidad Autonoma de aniales Tommaso Castroorio, DDS, PhD, Ortho. Spec. aniales, Colomia Researcher and Aggregate Professor Department of Surgical Sciences, Postgraduate School of Mario reco, DDS, PhD Orthodontics Visiting Professor Dental School, University of orino University of ’Auila orino, taly ’Auila, taly Orthodontics Unit Visiting Professor San Giovanni attista ospital University of Ferrara orino, taly Ferrara, taly Chisato Dan, DDS uis uanca, DDS, MS, PhD Private Practice Research Associate Smile nnovation Orthodontics Department of Orthodontics oyo, apan University of Geneva Geneva, Siterland Iacopo Ciof, DDS, PhD Associate Professor osef Kučera, MDr., PhD Division of Graduate Orthodontics and Centre for ultimodal Assistant Professor Sensorimotor and Pain esearch Department of Orthodontics Faculty of Dentistry Clinic of Dental edicine University of oronto First edical Faculty oronto, Ontario, Canada Charles University Prague, Cech epulic Daid Couchat, DDS, Ortho. Spec. Lecturer Private Practice Department of Orthodontics Cainet d’Orthodontie du dr Couchat Clinic of Dental edicine arseille, France Palacý University Olomouc, Cech epulic ae lkhol, DDS Senior Physician ernd . apatki, DDS, PhD Department of Orthodontics Department Head and hair Ulm University Department of Orthodontics Ulm, Germany Ulm University Ulm, Germany rancesco arino, MD Ortho. Spec. Private Practice Studio Associato dottri Garino orino, taly vi Contributors vii uca omardo, DDS, Ortho. Spec. Simone Parrini, DDS, Ortho. Spec. hairman and Professor Research Associate Postgraduate School of Orthodontics Department of Surgical Sciences, Postgraduate School in University of Ferrara Orthodontics Ferrara, taly Dental School, University of orino orino, taly Tianton ou, DMD, MSc Division of Gradual Orthodontics and Centre for ultimodal Serena aera, DDS, PhD, Ortho. Spec. Sensorimotor and Pain esearch Research Associate Faculty of Dentistry Department of Surgical Sciences, Postgraduate School in University of oronto Orthodontics oronto, Ontario, Canada Dental School, University of orino orino, taly Kam Malekian, DDS, MSc Private Practice ariele ossini, DDS, PhD, Ortho. Spec. Clinica io Research Associate adrid, Spain Department of Surgical Sciences, Postgraduate School in Orthodontics ianluca Mampieri, DDS, MS, PhD Dental School, University of orino Researcher and Aggregate Professor orino, taly Department of Clinical Sciences and ranslational edicine University of ome “or ergata” addah Saouni, DDS, Ortho. Spec. ome, taly Private Practice Cainet d’Orthodontie du dr Saouni doardo Mantoani, DDS, Ortho. Spec. andol ivage Research Associate Sanarysurer, France Department of Surgical Sciences, Postgraduate School in Orthodontics Sila Schmidt, DDS Dental School, University of orino Department of Orthodontics orino, taly Ulm University Ulm, Germany Io Marek, MDr., PhD Assistant Professor ör Schare, DDS, PhD, Ortho. Spec. Department of Orthodontics Private Practice Clinic of Dental edicine ieferorthopädische Prais Dr örg Schare Palacý University Cologne, Germany Oloumouc, Cech epulic onsultant iuseppe Siciliani, MD, DDS Department of Orthodontics hairman and Professor Clinic of Dental edicine School of Dentistry First edical Faculty University of Ferrara Charles University Ferrara, taly Prague, Cech epulic Ali Tassi, Sc, DDS, MClD Ortho aindra anda, DS, MDS, PhD Assistant Dean and hair Professor Emeritus Division of Graduate Orthodontics Division of Orthodontics Schulich School of edicine and Dentistry Department of Craniofacial Sciences he University of estern Ontario University of Connecticut School of Dental edicine ondon, Ontario, Canada Farmington, Connecticut, USA ohnn Tran, DMD, MClD Keni Oima, DDS, MDSc Division of Graduate Orthodontics Private Practice Schulich School of edicine and Dentistry Smile nnovation Orthodontics he University of estern Ontario oyo, apan ondon, Ontario, Canada viii Contributors laio rie, DDS, MDentSc enedict ilmes, DDS, MSc, PhD onn rthodontics Alumnianda rthodontics Professor Endoed hair Department of Orthodontics Program Director and Chair University of Düsseldorf Division of Orthodontics Düsseldorf, Germany Department of Craniofacial Sciences University of Connecticut School of Dental edicine Farmington, Connecticut, USA Foreword Aligners represent the new frontier in the art and science of Aligner treatment requires new knowledge the number orthodontics. This new frontier offers new opportunities of clinical and scientic reports about all the different as- and challenges, but also requires the need for additional pects of aligner orthodontics is increasing year by year. This knowledge. A rethinking of biomechanics and force deliv- book represents an up-to-date summary of the available ery concepts is needed along with the role of materials used research in the eld as well as a clinical atlas of treated pa- for aligners. There is a need for combining established con- tients based on the current evidence. We have made an cepts with new tools and technologies which aligner treat- attempt to provide benchmark for clinicians, researchers, ment requires. and residents who want to improve their skills in aligner When considering new methodologies, orthodontists orthodontics. should always remember that technology is a tool and not We would like to epress our great appreciation to all the the goal. Diagnosis, treatment plan, and biomechanics are friends and colleagues who have contributed to this book. t always the key elements of successful treatment, regardless was a pleasure to work with all these talented orthodon- of the treatment methodology. Aligner orthodontics is quite tists. different than traditional methods with brackets and wires. We would like to say thank you to the lsevier team for orce delivery with aligners is through plastic materials. their support, patience, and guidance during the challeng- Thus, the knowledge of the aligner materials, physical ing ovid pandemic. properties, attachment design, and the sequentialiation avindra anda protocol is crucial for treatment of malocclusions. t is also Tommaso astroorio imperative to understand limitations of aligner treatment rancesco arino and how to overcome them with the use of miniscrews and eni ima auiliaries. ix Contents 1 Diagnosis and Treatment Planning in the 12 The rid Approach in Class Malocclusions Three-Dimensional Era 1 Treatment 13 TOMMASO CASTROFLORIO, SEAN K. CARLSON, and FRANCESCO GARINO, TOMMASO CASTROFLORIO, and FRANCESCO GARINO SIMONE PARRINI 2 Current Biomechanical Rationale Concerning 13 Aligners and mpacted Canines 1 Composite Attachments in Aligner EDOARDO MANTOVANI, DAVID COUCHAT, TOMMASO CASTROFLORIO Orthodontics 13 JUAN PABLO GOMEZ ARANGO 14 Aligner Orthodontics in Prerestoratie 3 Clear Aligners: Material tructures and Patients 1 KENJI OJIMA, CHISATO DAN, and TOMMASO CASTROFLORIO Properties 3 MASOUD AMIRKHANI, FAYEZ ELKHOLY, and BERND G. LAPATKI 15 oncompliance pper Molar Distaliation 4 nuence o ntraoral actors on Optical and and Aligner Treatment or Correction o Class Mechanical Aligner Material Properties 3 Malocclusions 1 FAYEZ ELKHOLY, SILVA SCHMIDT, MASOUD AMIRKHANI, and BENEDICT WILMES and JÖRG SCHWARZE BERND G. LAPATKI 16 Clear Aligner Orthodontic Treatment o Patients 5 Theoretical and Practical Considerations in ith Periodontitis Planning an Orthodontic Treatment ith Clear TOMMASO CASTROFLORIO, EDOARDO MANTOVANI, and KAMY MALEKIAN Aligners TOMMASO CASTROFLORIO, GABRIELE ROSSINI, SIMONE PARRINI 17 urger irst ith Aligner Therap 3 FLAVIO URIBE and RAVINDRA NANDA 6 Class Malocclusion 1 MARIO GRECO 18 Pain During Orthodontic Treatment: Biologic 7 Aligner Treatment in Class Malocclusion Mechanisms and Clinical Management TIANTONG LOU, JOHNNY TRAN, ALI TASSI, and IACOPO CIOFFI Patients TOMMASO CASTROFLORIO, WADDAH SABOUNI, SERENA RAVERA, and FRANCESCO GARINO 19 Retention and tailit olloing Aligner Therap 8 Aligners in Etraction Cases 3 JOSEF KUČERA and IVO MAREK KENJI OJIMA, CHISATO DAN, and RAVINDRA NANDA 20 Oercoming the imitations o Aligner 9 Open-Bite Treatment ith Aligners Orthodontics: A rid Approach ALDO GIANCOTTI and GIANLUCA MAMPIERI LUCA LOMBARDO and GIUSEPPE SICILIANI 10 Deep Bite 1 nde LUIS HUANCA, SIMONE PARRINI, FRANCESCO GARINO, and TOMMASO CASTROFLORIO 11 nterceptie Orthodontics ith Aligners 11 TOMMASO CASTROFLORIO, SERENA RAVERA, and FRANCESCO GARINO x 1 Diagnosis and Treatment Planning in the Three-Dimensional Era TOMMASO CASTROFLORIO, SEAN K. CARLSON, and FRANCESCO GARINO Introduction printed models, indirect bonding trays, and custom-made brackets to robotically bend wires or aligners. Furthermore, rthodontics and dentofacial orthopedics is a specialty area it is becoming possible to remotely monitor treatment and of dentistry concerned with the supervision, guidance, and to control it.5 correction of the growing or mature dentofacial structures, The introduction of aligners in the orthodontics eld including those conditions that reuire movement of teeth led the digital evolution in orthodontics. The two nouns or correction of malrelationships and malformations of evolution and revolution both refer to a change; however, their related structures and the adustment of relationships there is a distinctive difference between the change im- between and among teeth and facial bones by the applica- plied by these two words. volution refers to a slow and tion of forces andor the stimulation and redirection of gradual change, whereas revolution refers to a sudden, functional forces within the craniofacial comple. dramatic, and complete change. hat has been claimed To accurately diagnose a malocclusion, orthodontics has as the “digital revolution” in orthodontics should be adopted the problem-based approach originally developed claimed as the “digital evolution” in orthodontics. rtho- in medicine. very factor that potentially contributes to the dontics and biomechanics have always had the same etiology and that may contribute to the abnormality or in- denitions, and we as clinicians should remember that uence treatment should be evaluated. nformation is gath- technology is an instrument, not the goal. This differenti- ered through a medical and dental history, clinical eami- ates orthodontists from marketing people. nation, and records that include models, photographs, and The diagnosis and problem list is the framework that dic- radiographic imaging. problem list is generated from the tates the treatment obectives for the patient. nce formu- analysis of the database that contains a network of inter- lated, the treatment plan is designed to address those obec- related factors. The diagnosis is established after a continu- tives. n aligner orthodontics, software displays ous feedback between the problem recognition and the da- treatment animations, helping the clinician to visualie the tabase Fig. .. ltimately, the diagnosis should provide appearance of teeth and face that is desired as treatment some insight into the etiology of the malocclusion. outcome; however, those animations should be decon- rthodontics diagnosis and treatment planning are deeply structed by the orthodontist frame by frame or stage by changing in the last decades, moving from two-dimensional stage, to dene how to address the treatment goal from me- hard tissue analysis and plaster cast review toward soft chanics to seuence. nly an accurate control of every sin- tissue harmony and proportions analyses with the support gle stage of the virtual treatment plan can produce reliable of three-dimensional technology. detailed clinical e- results. s usual, it is the orthodontist rather than the tech- amination remains the key of a good diagnosis, where many niue itself that is responsible for the treatment outcome. aspects of the treatment plan reveal themselves as a function ontemporary records should facilitate functional and of the systematic evaluation of the functional and aesthetic aesthetic evaluation of the patient. presentation of the patient. The introduction of a whole range of digital data acuisi- tion devices cone-beam computed tomography T, Intraoral Scans and Digital intraoral and desktop scanner and , and face scan- Models ner F, planning software computer-assisted design and computer-assisted manufacturing software, s are uickly replacing traditional impressions and plas- new aesthetic materials, and powerful fabrication machines ter models. These scanners generally contain a source of milling machines, printers is changing the orthodon- risk for inaccuracy because multiple single images are tic profession Fig. .. assembled to complete a model. ecent studies, however, s a result, clinical practice is shifting to virtual-based have shown that the trueness and precision of s of com- workows. Today it is common to perform virtual treat- mercially available scanning systems are ecellent for orth- ment planning and to translate the plans into treatment odontic applications. igital models are as reliable as tradi- eecution with digitally driven appliance manufacture and tional plaster models, with high accuracy, reliability, and placement using various techniues from reproducibility Fig. .. 1 2 Principles and Biomechanics of Aligner Treatment Database Clinical examination Chief complaint Medical history Models Photographs Radiographic imaging Dental history Intraoral scan 3-D facial scan CBCT Extraoral exam Intraoral exam Functional exam Problems Problem List Mechanics plan: Synthesis Treatment which movements Staging Treatment Virtual setup Treatment and diagnosis objectives with which definition prescription Virtual patient re-evaluation auxiliaries 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 measuring loop andor caliper, digital measurements on orthodontic software platforms to allow the orthodontist virtual models usually result in the same therapeutic deci- to perform virtual treatment plans and eplore various sions as evaluations performed the traditional way. Fur- treatment plans within minutes as opposed to epensive thermore, with their advantages in terms of cost, time, and and time-consuming diagnostic setups and waups. er- space reuired, digital models could be considered the new forming digital setups not only allows the clinician to e- gold standard in current practice. plore a number of treatment options in a simple manner igital impressions have proven to reduce remakes and but also facilitates better communication with other den- returns, as well as increase overall efciency. The patient tal professionals, especially in cases that reuire combined also benets by being provided a far more positive eperi- orthodontic and restorative treatments. The virtual treat- ence. urrent development of novel scanner technologies ment planning also allows for better communication with e.g., based on multipoint chromatic confocal imaging and patients and allows them to visualie the treatment out- dual wavelength digital holography will further improve come and understand the treatment process.5 the accuracy and clinical practicability of . Further advantages of virtual models of the dental ecently near infrared technology has been inte- arches are related to study model analysis, which is an es- grated in . The is the region of the electromagnetic sential step in orthodontic diagnostics and treatment plan- spectrum between . and mm Fig. .. The interaction ning. ompared to measurements on physical casts using a 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 NIRI image of a healthy tooth scanner uses light of 850nm that penetrates into the tooth structure to produce a NIRI image 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 urbaniation and industrialiation becoming more freuent transparent to due to the reduced scattering coefcient in the last decades.-5 Therefore, the need for a diagnostic of light, allowing it to pass through its entire thickness and tool providing information on the aspects of the dento- present as a dark area, whereas the dentin appears bright skeletal malocclusion is increasing. hile the clinical ap- due to the scattering effect of light caused by the orienta- plications span from evaluation of anatomy to pathology of tion of the dentinal tubules. ny interferencespathologic most structures in the maillofacial area, the key advantage lesionsareas of demineraliation appear as bright areas in of T is its high-resolution images at a relatively lower a image due to the increased scattering within the re- radiation dose. gion. Therefore provides information regarding possible posing patients to -rays implies the eistence of a decays without any -ray eposure. clinical ustication and that all the principles and proce- Through the use of digital impression making, it has dures reuired to minimie patient eposure are consid- been determined that laboratory products also become ered. The concept should always be kept in mind more consistent and reuire less chair time at insertion. is an acronym used in radiation safety for as low as reasonably achievable. This concept is supported by profes- 3D Imaging sional organiations as well as by government institu- tions. ecogniing that diagnostic imaging is the single CONE-BEAM COMPUTED TOMOGRAPHY greatest source of eposure to ioniing radiation for the population that is controllable, the ational ommission imaging has evolved greatly in the last two decades and on adiation rotection and easurements has introduced has found applications in orthodontics as well as in oral and a modication of the concept. represents maillofacial surgery. n medical imaging, a set of ana- as low as diagnostically acceptable. mplementation of this tomic data is collected using diagnostic imaging euip- concept will reuire evidence-based udgments of the level ment, processed by a computer and then displayed on a of image uality reuired for specic diagnostic tasks as monitor to give the illusion of depth. epth perception well as eposures and doses associated with this level of causes the image to appear in . ver the last 5 years, uality. ittle research is currently available in this area. T imaging has emerged as an important supplemental For imaging modalities used in orthodontics, the ra- radiographic techniue for orthodontic diagnosis and treat- diation dose for panoramic imaging varies between and ment planning, especially in situations that reuire an un- µv, while a cephalometric eam range is between and derstanding of the comple anatomic relationships and 5 µv. full mouth series ranges from to 5 µv based surrounding structures of the maillofacial skeleton. From on the type of collimation used. hile and radia- the introduction of the cephalostat, roadbent stressed the tion doses are often compared for reference, they cannot need for a perfect matching of the lateral and posteroante- truly be compared because the acuisition physics and the rior -rays to obtain a perfect reproduction of the associated risks are completely different and cannot be skull. T imaging provides uniue features and advan- euated. The actual risk for low-dose radiographic proce- tages to enhance orthodontic practice over conventional dures such as maillofacial radiography, including T, is etraoral radiographic imaging. ateral cephalometrics difcult to assess and is based on conservative assumptions provides information on the sagittal and vertical aspects of as there are no data to establish the occurrence of cancer the malocclusion with little contribution about unilateral following eposure at these levels. owever, it is generally or transversal discrepancies. The latter seem to be related to 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 demonstrated, allowing precise assessment of unerupted is no safe limit or safety one for radiation eposure in orth- tooth sies, bony dimensions in all three planes of space, odontic diagnostic imaging. recent meta-analysis about and even soft tissue anthropometric measurements— the effective dose of dental T stated that the mean adult things that are all important in orthodontic diagnosis and effective doses grouped by eld of view F sie were treatment planning.- µv large, µv medium, and µv small. The accurate localiation of ectopic, impacted, and su- ean child doses were 5 µv combined large and me- pernumerary teeth is vital to the development of a patient- dium and µv small. arge differences were seen specic treatment plan with the best chance of success. between different T units. T has been demonstrated to be superior for localiation The merican ental ssociation ouncil on cientic and space estimation of unerupted maillary canines com- ffairs proposed a set of principles for consideration pared with conventional imaging methods.5 ne study in the selection of T imaging for individual patient care. indicated that the increased precision in the localiation of ccording to the guidelines, clinicians should perform radio- the canines and the improved estimation of the space con- graphic imaging, including T, only after professional ditions in the arch obtained with T resulted in a differ- ustication that the potential clinical benets will out- ence in diagnosis and treatment planning toward a more weigh the risks associated with eposure to ioniing radia- clinically orientated approach.5 T imaging was proven tion. owever, T may supplement or replace conven- to be signicantly better than the panoramic radiograph in tional dental -rays when the conventional images will not determining root resorption associated with canine impac- adeuately capture the needed information. tion. ne study supported improved root resorption ecently, a number of manufacturers have introduced detection rates of with the use of T when com- T units capable of providing medium or even full F pared with imaging. hen used for diagnosis, T T acuisition using low-dose protocols. y adustments has been shown to alter and improve the treatment recom- to rotation arc, m, kp, or the number of basis images or mendations for orthodontic patients with impacted or a combination thereof, T imaging can be performed at supernumerary teeth. effective doses comparable with conventional panoramic ased on the ndings of a recent review and in accor- eaminations range, – µv. This is accompanied by dance with the T entomaillofacial aediatric signicant reductions in image uality; however, viewer maging n nvestigation Towards ow ose adiation software can be helpful in improving the clinical eperience nduced isks proect, T can be considered also in with low-uality images. ven at this level, child doses have children for diagnosis and treatment planning of impacted been reported to be, on average, greater than adult teeth and root resorption Fig. .5. doses. The use of low-dose protocols may be adeuate for aillary transverse deficiency may be one of the low-level diagnostic tasks such as root angulations. most pervasive skeletal problems in the craniofacial re- gion. ts many manifestations are encountered daily by BENEFT OF CBCT FOR ORTHODONTC the orthodontist. AEMENT lthough many analyses of the lateral cephalometric headlm have been developed for use in orthodontic and The benets of T for orthodontic assessment include orthognathic treatment planning, the posteroanterior accuracy of image geometry. T offers the distinct ad- cephalogram has been largely ignored. The diagnosis of vantage of geometry, which allows accurate measure- transverse discrepancy is uite challenging in the daily ments of obects and dimensions. The accuracy and reli- practice because of several methodologic limitations of the ability of measurements from T images have been 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 differ- asymmetry cases. They can also be used to generate substi- ent tooth level, buccolingual inclination of each tooth, and tute grafts when warranted. T can be useful as a valu- root positions in the alveolar bone can be determined and able planning tool from initial evaluation to the surgical evaluated from the T Fig. .. ith this information, procedure and then the correction of the dental component the clinician can make a proper diagnosis and treatment in the surgery-rst orthognathic approach. plan for the patient. n addition, databases may be interfaced with the ana- The temporomandibular oint T can be assessed for tomic models to provide characteristics of the displayed tis- pathology more accurately with T images than with sues to reproduce tissue reactions to development, treat- conventional radiographs. The T volume for orthodon- ment, and function. The systematic summariation of the tic assessment will generally include the T and therefore results presented in the literature suggests that computer- is available for routine review. everal retrospective analy- aided planning is accurate for orthognathic surgery of the ses of T volumes indicate 5 to of incidental mailla and mandible, and with respect to the benets to ndings are related to T Fig. ., which is signicant the patient and surgical procedure it is estimated that enough for further follow-up or referral. computer-aided planning facilitates the analysis of surgical T data can also be used to obtain the volumetric ren- outcomes and provides greater accuracy Fig. .. dering of the upper airways. tudies of the upper airway recent systematic review was conducted to evaluate based on T scans are considered to be reliable in dening whether T imaging can be used to assess dentoalveolar the border between soft tissues and void spaces i.e., air, relationships critical to determining risk assessment and thus providing important information about the morphol- help determine and improve periodontal treatment needs in ogy i.e., cross-sectional area and volume of the pharyngeal patients undergoing orthodontic therapy. The conclusion airway5 Fig. .. owever, despite the potentials offered was that pretreatment orthodontic T imaging can as- by the techniue in this eld and the potential role of ortho- sist clinicians in selecting preventive or interceptive peri- dontists as sentinel physicians for sleep breathing disorders, odontal corticotomy and augmentation surgical reuire- limited, poor uality, and low evidence level literature is ments, especially for treatment approaches involving buccal available on the effect of head posture and tongue position tooth movement at the anterior mandible or maillary pre- on upper airway dimensions and morphology in imag- molars to prevent deleterious alveolar bone changes. This ing. atural head position at T acuisition is the sug- assumption seems more suitable for skeletally mature pa- gested standardied posture. owever, for repeatable mea- tients presenting with a thin periodontal phenotype prior to sures of upper airway volumes it may clinically be difcult to orthodontic treatment Fig. .. obtain. ndications and methods related to tongue position and breathing during data acuisition are still lacking. Fur- 3D FACA RECONTRUCTON TECHNUE thermore, a recent study focusing on the reliability of air- way measurements stated that the oropharyngeal airway The accurate acuisition of face appearance character- volume was the only parameter found to have generalied istics is important to plan orthognathic surgery, and ecel- ecellent intra-eaminer and inter-eaminer reliability. lent work is based on an eact face modeling. precise n orthognathic surgery, igital maging and ommuni- approach to digital face prole acuiring, which is ap- cations in edicine data from T can be used to plied to simulate and design an optimal plan for face sur- fabricate physical stereolithographic models or to generate gery by modern technologies such as , is reuired. virtual models. The reconstructions are etremely Three types of face modeling methods are currently useful in the diagnosing and treatment planning of facial 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 pre- scribed 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 and digital models with specic simulation software will optical sensing techniue. The reconstruction provide useful indications in relation to orthodontic treat- method based on T technology is sensitive to the skeleton ment results and the eventual need of interdisciplinary in- and can be conveniently utilied for craniofacial plastics, tervention. as well as the oral and maillofacial correction of abnor- malities. oft tissue data etraction, or segmentation, RTUA ETUP can be created using a dedicated software. For orthodontic purposes, the image should be recorded with eyes open everal software programs are available on the market to and with the patient smiling. The smiling image will per- create virtual setups able to produce the seuence of physi- mit the use of dental landmarks to superimpose the digital cal models on which thermoforming plastic foils are used to models on the face reconstruction for treatment plan- create aligners. ning purposes. ovel technologies aiming at acuiring etup accuracy is improved when virtual teeth segmen- facial surface are available. tereophotogrammetry and tation is applied on digital models obtained by or digiti- laser scanning allow operators to uickly record facial ation of plaster casts, reducing the loss of tooth structure anatomy and to perform a wider set of measurements5 observed during the cutting process of the plaster in con- not eposing patients to radiation Fig. .. tereopho- ventional plaster and wa setups. togrammetry still represents the gold standard with The segmentation process starts with marking mesial respect to laser scanning at least for orthodontic applica- and distal points on each tooth or simply indicating the tions since it is characteried by good precision and repro- center of the crown on the occlusal view of the arches, de- ducibility, with random errors generally less than pending on the software used. Then the software generally mm.5 ith this method, images are acuired by identies the gingival margin. Teeth segmentation and the combining photographs captured from various angles tooth-tooth-gingiva segmentation are eecuted semiauto- with synchronous digital cameras, with the main advan- matically, but the operator can always correct the auto- tage of reducing possible motion artifacts. The main limi- matic process. nce teeth are segmented they are separated tation at this stage is represented by the high cost of the from the gingiva, and a mean virtual root shape and instrumentation. length are derived from proprietary databases is applied. ccording to arver and acobson and arver and ck- ecently, virtual setup software programs are starting to erman, it may be inappropriate to place everyone in the use real root morphologies derived from patient T data same esthetic framework and even more problematic to at- when available. Tooth segmentation from T images tempt this based solely on hard tissue relationships since the in those cases is a fundamental step. ecent engineering soft tissues often fail to respond predictably to hard tissue innovations made the process simple and timesaving with changes. ntegrating T data, facial reconstruction, 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 e- cellent 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 interproi- novel superimposition techniues, clinicians are able to mal contacts dened, the arch form is adusted using soft- simulate the outcome of both the osseous structures and ware tools that can create an individual arch form. igital the soft tissue posttreatment. arch templates are also available, while several software pro- The data integration makes the diagnostic process grams consider the an acronym for ill ndrews and the treatment planning more accurate and complete, and arry ndrews ridge. provides an effective communication tool and a method for The occlusal plane as well as the original vertical plane patients to visualie the simulated outcomes, instills moti- are used as reference. ach tooth can be moved in the vation, and encourages compliance to achieve the desired space since the reuired nal position has been achieved. t treatment outcome Fig. .. is important to mention that tooth movements on comput- hat technology is providing to orthodontists is ama- ers are unlimited. Tooth alignment and leveling can be ing; however, what is still missing is the fourth dimension planned on the computer screen, but this result may not be i.e., the dynamic movements of the mandible and the sur- realistic for that specic patient. bviously, tooth movement rounding tissues integrated in the virtual model. dealisti- has its biologic limitations. n the basis of the used system cally, the capture of digital data for virtual modeling should the virtual setup could be prepared by a trained dental tech- happen in a one-step, single-device approach to improve nician or by a software epert; however, every setup should accuracy. Future research will ll this gap and will realie be based on biologic principles and on a biomechanics the dream of the real virtual patient. 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. .. 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 photo- graphic facial images and high-resolution surface models of the dentition produced by direct scans intraorally or in- directly by scanning impressions or study models. The inte- gration of hard and soft tissues can provide a greater un- derstanding of the interrelationship of the dentition and Fig. 1.13 The virtual patient in hich cone-beam computed tomogra- soft tissues to the underlying osseous frame. ndividual phy data, facial three-dimensional reconstruction, and virtual setup models of tooth are needed for the computer-aided obtained after teeth segmentation are superimposed. Courtesy of dr. orthodontic treatment planning and simulation. ith the Alain Souchet, ulhouse, rance. 12 Principles and Biomechanics of Aligner Treatment References . odges , tchison , hite . mpact of cone-beam computed tomography on orthodontic diagnosis and treatment planning. 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J Orofac Orthop. ;-. ;-. 2 Current Biomechanical Rationale Concerning Composite Attachments in Aligner Orthodontics JUAN PABLO GOMEZ ARANGO Introduction wear resistance to deliver a stable attachment shape during treatment, assuring its functionality. Mantovani he orthodontic techniue that we now call “aligner or- et al.3 also concluded that the use of bulk-lled resins for thodontics” has evolved considerably over the last attachment fabrication improved dimensional stability years. mprovements in behavior of aligner plastics, treat- when compared to low-viscosity resins, which experience ment planning software, and three-dimensional 3 higher polymerization shrinkage. he use of translucent printing have served one basic but fundamental inten- composites generally provides sufcient esthetic accep- tion to mitigate the biomechanical limitations inherent tance and stain resistance as long as an adeuate bonding to aligner-based tooth movement. nother signicant techniue is executed, in which voids bubbles in attach- development designed to overcome the aforementioned ment surface and excessive residue ash left on tooth biomechanical shortcomings of aligner systems has been surface are avoided. the continuous improvement of biomechanically comple- everal considerations come into play when determining mentary composite attachments. ttachments were con- the optimal attachment design for a specic clinical obec- ceived to produce supplementary force vectors that, when tive geometry, location, and size. applied to teeth by the aligner material, transform the resultant system, allowing complex tooth movements. he application of one of the initial geometric congura- Geometry (Active Surface tions was initially presented by the clinical team from Orientation) lign echnology nc., as basic x 3 mm rectangular structures, bonded to the lower incisor buccal surface, in t the time of aligner insertion, orthodontic forces will be an attempt at controlling undesired tipping during space produced in response to the particular complex pattern of closure after incisor extraction ig. .. s the mismatches between plastic and tooth structure. his pat- incisors adacent to the extraction space begin to incline tern of mismatch–plastic deformation–orthodontic force is mesially, the rigid, xed structure of the attachment critical for attachment design during digital simulation to collides with aligner plastic, producing force couples that produce specic areas active surfaces that will contact counteract the initial moment, reducing undesired tip- aligner plastic with predetermined force magnitudes, ping see ig. .. producing the desired force vectors and conseuent tooth rthodontic tooth movement with conventional bracket movements. ot all the surface area of attachments will be techniues can deliver sophisticated force systems due to in direct contact with the aligner. he active or functional the manner in which the rigid ligature-archwire-bracket surfaces can and should be determined with thoughtful scheme “grasps” the malaligned tooth. his particular biomechanical intentionality, in accordance with clinical arrangement allows broad control of magnitude and direc- obectives ig. .. hile the magnitude of the force tion of applied force vectors, and, conseuentially, of tooth produced is determined by the amount of mismatch along movement ig. .. with the characteristics of aligner material, the direction t is important to keep in mind that attachments work, of the force will depend on the orientation of the active not as active agents that produce forces, but by passively surface. he principles of mechanics state that the direction “getting in the way” of plastic as it elastically deforms due of the normal component of the contact force the vector to lack of coincidence between tooth position and aligner that in this case acts upon the active surface of the attach- material “mismatch”, establishing the force vector that ment will always be perpendicular to that surface see subseuently affects the tooth ig. .3. ig. .. dentifying the direction of these complemen- iomaterials used for attachment fabrication must as- tary force vectors is essential for treatment planning, espe- sure that reuirements in adhesion, wear resistance, and cially when more than one force acts simultaneously. n esthetics are fullled. recent study suggests that con- these cases, the resultant forces must be properly recog- temporary microlled resin composites provide sufcient nized to deliver predictable tooth movements see ig. .. 13 14 Principles and Biomechanics of Aligner Treatment A A B C B Fig. 2.3 (A) Alignertooth mismatch. (B) lastic aligner deformation and activation of forces upon aligner insertion. () Tooth alignment Fig. 2.1 (A) Mesial tipping moments (red curved arrows) produced by after aligner seuence. 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. Location 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 mesiodis- tal tipping and intrusion. n a case in which mesiolingual rotation of the tooth is reuired, localization of attachment Fig. 2.2 The typical force couple generated during bracetbased will produce a strong mesial tipping moment and a weak alignment of rotated tooth ith a fully engaged . iTi archire mesiolingual rotational moment ig. .. n this specic consists of to force vectors one that pushes against the posterior clinical situation, a better alternative would be with attach- all of the slot (red arrow) and a second that pulls aay from the same ment location , in which modication in distance from all (blue arrow) line of action to center of resistance would reduce tipping 2 urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics 15 A B C 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 capac- Size ity see ig. .. nother example of the inuence of attachment local- ttachment size is important because of its mechanical ization is observed during transverse arch expansion, and esthetic implications. mall congurations are desir- when buccal tipping of posterior segments is detrimental able because they are less noticeable however, as size di- to treatment obectives. recent unpublished nite minishes, so does the ability to produce predictable forces element analysis study of the mechanical effects due to reduced active surface area. n the other hand, of the bonding position of rectangular horizontal attach- larger attachment designs are desirable because of their ments found that the resultant tipping moment acting increased biomechanical capabilities, but they result in in- on the molars was greater when located on the lingual creased aligner retention with subseuent patient discom- surface of the rst upper molars versus the labial surface fort and negative esthetic perception, especially with high- ig. .. prole congurations in anterior teeth. 16 Principles and Biomechanics of Aligner Treatment A B Fig. 2.6 uring epansion, labial attachment location (A) produced smaller net buccal molar tipping moments than lingually bonded attachments (B). Functions nongingivally beveled such as a horizontal rectangular or occlusally beveled design, as close to the gingival margin PROVIDING ALIGNER RETENTION as possible see ig. .. s a general rule of attachment design, occlusal beveling will facilitate aligner insertion or aligner-based orthodontic forces to affect teeth as con- due to the inclined plane conguration as well as increase ceived in digital simulation, the aligner must be stably force and discomfort reuired for aligner removal. seated after insertion and remain so for the duration of treatment. ccasionally, decient adaptation of the aligner AVOIDING ALIGNER “SLIPPING” may occur, usually resulting from faulty fabrication, but may also occur due to the many reactive forces produced specially when rotating rounded teeth, the sum of a se- once properly tted. or example, as a freuent response to ries of tangential forces is responsible for tooth movement intrusive forces acting on the posterior teeth, the aligner ig. ., causing inconvenient displacement slipping will tend to be dislodged in the anterior segment, and vice of the aligner in relation to the tooth surface, reducing the versa. he use of intermaxillary elastics, especially when system’s efcacy and predictability, and resulting in lack they are engaged directly to the aligner, will also tend to of full expression of digitally planned rotation with the vertically dislodge it in the direction of the elastic tooth lagging behind the corresponding aligner stage. force. onding retentive attachments on teeth adacent to linically, incomplete rotation and loss of tracking will be those receptors of the elastic force is recommended to observed, manifesting as a space between tooth and plas- maintain proper aligner engagement ig. .. study tic see ig. .. ppropriately designed attachments by ones et al. suggests that the optimal attachment con- can help the aligner lock in to the tooth crown, greatly guration, when high aligner retention is imperative, is a reducing this undesired slipping effect. A 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 17 nfortunately, to harness the full clinical potential of bonded attachments, current polymers have yet to resolve limitations associated with their viscoelastic and hygro- scopic 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 relax- ation. 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 deforma- A tion of the aligner material is evident. his time-dependent B plastic deformation under constant force is called creep and Fig. 2.8 (A) Multiple tangential forces (red arrows) acting during is attributed to reorganization of polymer chains. t is alignerbased, bicuspid rotation. (B) ue to slipping effect, incomplete important to underline that this permanent deformation, epression of epected rotation ith space beteen tooth and aligner so detrimental to clinical performance of plastic aligners, is (in yellow) ill be observed. not caused by a violation of the materials’ elastic limit but is due to a time-dependent, mechanochemical phenome- non of a different nature. DELIVERING PREDETERMINED FORCE VECTORS his inherent aw of aligner plastics is the maor cause behind the inconsistent force levels and plastic deformation he fundamental purpose of composite attachments in that result in one of the most dreaded occurrences for aligner orthodontics is to produce specic, complementary orthodontists practicing aligner orthodontics, now com- force vectors reuired for predictable tooth movement, monly referred to as loss of tracking. ig. . illustrates an which are not possible with the sole use of aligners thermo- example of the clinical manifestations of this complex formed with existing materials ig. .. 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 coinci- dence 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 under- standing of the effect of geometry, location, and size of the composite structure, has resulted in a diverse array of con- gurations with well-dened biomechanical obectives. VERTICAL CONTROL he tendency of conventional xed orthodontics to in- crease vertical dimension, especially in open-bite patients with increased anterior facial height, has been studied. A B ligner-based treatment has proven to be an effective Fig. 2.9 (A) Properly designed attachments produce complementary alternative for open-bite correction-3 with encouraging force vectors reuired for predictable tooth movement. (B) Polymer results.3 uccessful treatment often includes the sum of stress relaation and creep, along ith incomplete rotation and unin complementary clinical strategies such as the combined tended force (blue arrow), may occur during seuence of aligner effect of counterclockwise mandibular rotation, posterior based, tooth rotation stages. 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 ef- fects such as root resorption, periodontal deterioration, in- stability, and unfavorable esthetics. long with these clinical restrictions, aligner extrusion poses mechanical lim- itations in anterior teeth in which buccal and lingual crown surfaces converge towards the incisal edge ig. ., fa- cilitating aligner dislodgement and rendering this type of tooth movement virtually impossible see ig. . with- out the use of supplementary composite attachments. gingivally oriented, inclined plane conguration ig. . provides a force system that improves predictability of this A 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 B A B Fig. 2.12 (A) Optimied trusion Attachments (Align Technology, Fig. 2.11 (A) onverging buccal and lingual cron surfaces. (B) nde anta lara, A) on central incisors. (B) ingivallyoriented inclined sired aligner dislodgment during etrusive movement. 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) acti
