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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aligner orthodontics orthodontic treatment biomechanics dental treatment

Summary

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 Castroorio, 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 oyo, 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 verication 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 Keni, for your passion, enthusiasm, commitment, and support you are always an eample 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 eperience. 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 amaing, 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 Palo ome Arano, DDS, MSc School of Dentistry, University of the Pacic Associate Professor San Francisco, California, USA Orthodontics Program Universidad Autonoma de aniales Tommaso Castroorio, DDS, PhD, Ortho. Spec. aniales, Colomia 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 ’Auila orino, taly ’Auila, 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 oyo, apan University of Geneva Geneva, Siterland Iacopo Ciof, DDS, PhD Associate Professor osef Kučera, MDr., 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, Cech epulic Daid Couchat, DDS, Ortho. Spec. Lecturer Private Practice Department of Orthodontics Cainet d’Orthodontie du dr Couchat Clinic of Dental edicine arseille, France Palacý University Olomouc, Cech epulic ae 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 dottri Garino orino, taly vi Contributors vii uca omardo, 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 aera, 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 ariele 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 Saouni, DDS, Ortho. Spec. ome, taly Private Practice Cainet d’Orthodontie du dr Saouni doardo Mantoani, DDS, Ortho. Spec. andol ivage Research Associate Sanarysurer, France Department of Surgical Sciences, Postgraduate School in Orthodontics Sila Schmidt, DDS Dental School, University of orino Department of Orthodontics orino, taly Ulm University Ulm, Germany Io Marek, MDr., PhD Assistant Professor ör Schare, DDS, PhD, Ortho. Spec. Department of Orthodontics Private Practice Clinic of Dental edicine ieferorthopädische Prais Dr örg Schare Palacý University Cologne, Germany Oloumouc, Cech epulic 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, Cech epulic Ali Tassi, Sc, DDS, MClD Ortho aindra 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 Keni Oima, DDS, MDSc Division of Graduate Orthodontics Private Practice Schulich School of edicine and Dentistry Smile nnovation Orthodontics he University of estern Ontario oyo, apan ondon, Ontario, Canada viii Contributors laio rie, DDS, MDentSc enedict ilmes, DDS, MSc, PhD onn rthodontics Alumnianda rthodontics Professor Endoed 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 scientic 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 epress 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 sequentialiation avindra anda protocol is crucial for treatment of malocclusions. t is also Tommaso astroorio imperative to understand limitations of aligner treatment rancesco arino and how to overcome them with the use of miniscrews and eni ima auiliaries. 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 Prerestoratie 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 Distaliation 4 nuence 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 tailit olloing Aligner Therap  8 Aligners in Etraction Cases 3 JOSEF KUČERA and IVO MAREK KENJI OJIMA, CHISATO DAN, and RAVINDRA NANDA 20 Oercoming 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 nterceptie Orthodontics ith Aligners 11 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 reuire 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 adustment 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 andor 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- denitions, 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 eami- 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 obectives for the patient. nce formu- analysis of the database that contains a network of inter- lated, the treatment plan is designed to address those obec- 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 visualie 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 dene how to address the treatment goal from me-  hard tissue analysis and plaster cast review toward soft chanics to seuence. 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 niue 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 acuisi- 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- workows. Today it is common to perform virtual treat- mercially available scanning systems are ecellent for orth- ment planning and to translate the plans into treatment odontic applications. igital models are as reliable as tradi- eecution with digitally driven appliance manufacture and tional plaster models, with high accuracy, reliability, and placement using various  techniues 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. (Modied from Uribe FA, Chandhoe TK, Nanda R. Indiidaied orhodoni dianoi. In Nanda R, ed. Esthetics and Biomechanics in Orthodontics. nd ed. S Loi, MO Eeier Sander . 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 andor 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 eplore various sions as evaluations performed the traditional way. Fur- treatment plans within minutes as opposed to epensive thermore, with their advantages in terms of cost, time, and and time-consuming diagnostic setups and waups. er- space reuired, 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 efciency. The patient tal professionals, especially in cases that reuire combined also benets by being provided a far more positive eperi- 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 visualie 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 specic 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 roimal 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 AS, Copenhagen, enmar uorescent technology for surface decay detection (left) and I technology for interproimal decay detection (right). tooth provides additional data of its structure. namel is urbaniation and industrialiation becoming more freuent transparent to  due to the reduced scattering coefcient 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 interferencespathologic most structures in the maillofacial area, the key advantage lesionsareas of demineraliation 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 eistence of a decays without any -ray eposure. clinical ustication and that all the principles and proce- Through the use of digital impression making, it has dures reuired to minimie patient eposure are consid- been determined that laboratory products also become ered. The  concept should always be kept in mind more consistent and reuire 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 organiations as well as by government institu- tions.  ecogniing that diagnostic imaging is the single CONE-BEAM COMPUTED TOMOGRAPHY greatest source of eposure to ioniing 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 modication of the  concept.  represents maillofacial surgery. n  medical imaging, a set of ana- as low as diagnostically acceptable. mplementation of this tomic data is collected using diagnostic imaging euip- concept will reuire evidence-based udgments of the level ment, processed by a computer and then displayed on a  of image uality reuired for specic diagnostic tasks as monitor to give the illusion of depth. epth perception well as eposures 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 techniue for orthodontic diagnosis and treat- diation dose for panoramic imaging varies between  and ment planning, especially in situations that reuire an un-  µv, while a cephalometric eam range is between  and derstanding of the comple anatomic relationships and 5 µv.  full mouth series ranges from  to 5 µv based surrounding structures of the maillofacial 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 acuisition physics and the rior -rays to obtain a perfect  reproduction of the associated risks are completely different and cannot be skull. T imaging provides uniue features and advan- euated. The actual risk for low-dose radiographic proce- tages to enhance orthodontic practice over conventional dures such as maillofacial radiography, including T, is etraoral radiographic imaging. ateral cephalometrics difcult 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 eposure 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 eposure in orth- tooth sies, 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 sie were treatment planning.-  µv large,  µv medium, and  µv small. The accurate localiation of ectopic, impacted, and su- ean child doses were 5 µv combined large and me- pernumerary teeth is vital to the development of a patient- dium and  µv small. arge differences were seen specic treatment plan with the best chance of success. between different T units. T has been demonstrated to be superior for localiation The merican ental ssociation ouncil on cientic and space estimation of unerupted maillary 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 localiation 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- ustication that the potential clinical benets will out- ence in diagnosis and treatment planning toward a more weigh the risks associated with eposure to ioniing radia- clinically orientated approach.5 T imaging was proven tion. owever, T may supplement or replace conven- to be signicantly better than the panoramic radiograph in tional dental -rays when the conventional images will not determining root resorption associated with canine impac- adeuately 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 acuisition using low-dose protocols. y adustments has been shown to alter and improve the treatment recom- to rotation arc, m, kp, 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- eaminations range, – µv. This is accompanied by dance with the T entomaillofacial aediatric signicant reductions in image uality; however, viewer maging n nvestigation Towards ow ose adiation software can be helpful in improving the clinical eperience nduced isks proect, 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 adeuate for aillary 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 BENEFT OF CBCT FOR ORTHODONTC the orthodontist. AEMENT lthough many analyses of the lateral cephalometric headlm have been developed for use in orthodontic and The benets 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 obects 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 loer canine in hich the cone-beam computed tomography data are helpful in dening the right mechanics. The maillary 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 summariation 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 mailla and mandible, and with respect to the benets to ndings are related to T Fig. ., which is signicant 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 dening 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 airway5 Fig. .. owever, despite the potentials offered was that pretreatment orthodontic T imaging can as- by the techniue 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 reuire- 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 maillary pre- on upper airway dimensions and morphology in  imag- molars to prevent deleterious alveolar bone changes. This ing. atural head position at T acuisition is the sug- assumption seems more suitable for skeletally mature pa- gested standardied posture. owever, for repeatable mea- tients presenting with a thin periodontal phenotype prior to sures of upper airway volumes it may clinically be difcult to orthodontic treatment Fig. .. obtain. ndications and methods related to tongue position and breathing during data acuisition are still lacking. Fur- 3D FACA RECONTRUCTON TECHNUE thermore, a recent study focusing on the reliability of air- way measurements stated that the oropharyngeal airway The accurate acuisition of  face appearance character- volume was the only parameter found to have generalied istics is important to plan orthognathic surgery, and ecel- ecellent intra-eaminer and inter-eaminer reliability. lent work is based on an eact  face modeling.  precise n orthognathic surgery, igital maging and ommuni- approach to  digital face prole acuiring, 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 reuired. virtual  models. The  reconstructions are etremely Three types of  face modeling methods are currently useful in the diagnosing and treatment planning of facial used to etract human face proles 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. Airay 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 softare. (ohin Imain, Chaorh, CA, USA. the passive optical  sensing techniue, and the active and digital models with specic simulation software will optical  sensing techniue. 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 utilied for craniofacial plastics, tervention. as well as the oral and maillofacial correction of abnor- malities. oft tissue data etraction, 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 seuence 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 acuiring 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 measurements5 observed during the cutting process of the plaster in con- not eposing 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 characteried 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 acuired by identies the gingival margin. Teeth segmentation and the combining photographs captured from various angles tooth-tooth-gingiva segmentation are eecuted 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 epansion in a subect ith poor periodontal support (upper). rthodontic epansion, 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 Gibei , iarei , oa , e a. Threedimeniona faia anaom eaaion reiabii of aer anner oneie an roedre in omarion ih ereohoorammer. 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, visualiing 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 interproi- novel  superimposition techniues, clinicians are able to mal contacts dened, the arch form is adusted 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 visualie 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 reuired 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 specic 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 epert; however, every setup should accuracy. Future research will ll this gap and will realie 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 techniues 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 NTEGRATON 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 uniue 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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Two-versus three-dimensional . amardella T, othier , ilella , et al. irtual setup application imaging in subects with unerupted maillary canines. Eur J Orthod. in orthodontic practice. 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 techniue 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 sufcient esthetic accep- tion to mitigate the biomechanical limitations inherent tance and stain resistance as long as an adeuate bonding to aligner-based tooth movement. nother signicant techniue 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 specic clinical obec- 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 congura- 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 adacent 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 specic 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 conseuent tooth rthodontic tooth movement with conventional bracket movements. ot all the surface area of attachments will be techniues 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- obectives ig. .. hile the magnitude of the force tion of applied force vectors, and, conseuentially, 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 subseuently 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 reuirements in adhesion, wear resistance, and cially when more than one force acts simultaneously. n esthetics are fullled.  recent study suggests that con- these cases, the resultant forces must be properly recog- temporary microlled resin composites provide sufcient 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) Alignertooth 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 seuence. 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 uantied, 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 reuired, localization of attachment Fig. 2.2 The typical force couple generated during bracetbased  will produce a strong mesial tipping moment and a weak alignment of rotated tooth ith a fully engaged . iTi archire mesiolingual rotational moment ig. .. n this specic consists of to 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 aay from the same ment location , in which modication 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 etrusion and clocise, secondorder rotation. A Distal Mesial B Distal Mesial Fig. 2.5 (A) ue to the distance beteen the center of resistance (blue dot) and the line of action (red dotted line), large mesial tipping and negligible mesiolingual rotational moments should be epected. (B) A more mesial and apical attachment location ill result in reduced mesial tipping and increased mesiolingual rotational moments, increasing clinical efcacy. tendency as well as increase mesiolingual rotational capac- Size ity see ig. .. nother example of the inuence of attachment local- ttachment size is important because of its mechanical ization is observed during transverse arch expansion, and esthetic implications. mall congurations are desir- when buccal tipping of posterior segments is detrimental able because they are less noticeable however, as size di- to treatment obectives.  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 subseuent patient discom- surface of the rst upper molars versus the labial surface fort and negative esthetic perception, especially with high- ig. .. prole congurations in anterior teeth. 16 Principles and Biomechanics of Aligner Treatment A B Fig. 2.6 uring epansion, 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 conguration as well as increase ceived in digital simulation, the aligner must be stably force and discomfort reuired for aligner removal. seated after insertion and remain so for the duration of treatment. ccasionally, decient 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 freuent 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 efcacy 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 adacent 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 adacent to force application increase aligner retention hen using inter maillary 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 infreuently, 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 adust 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 seuence 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 alignerbased, bicuspid rotation. (B) ue to slipping effect, incomplete important to underline that this permanent deformation, epression of epected rotation ith space beteen 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 maor 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 specic, complementary orthodontists practicing aligner orthodontics, now com- force vectors reuired 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 seuence must be designed. Basic Attachment Conurations in Current Ainer 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-dened biomechanical obectives. 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 reuired for predictable tooth movement. (B) Polymer results.3 uccessful treatment often includes the sum of stress relaation and creep, along ith incomplete rotation and unin complementary clinical strategies such as the combined tended force (blue arrow), may occur during seuence 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 linhec treatment plan. (B) oss of tracing ith incomplete epression of rotation and etrusion of left upper bicuspid. ac of coincidence beteen attachment (green shaded area) and its corresponding recess in the aligner (green outline) is observed. ANTERIOR ETRSION 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 conguration 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 simplication of a complex interaction of vectors. he resultant force acting on the B A B Fig. 2.12 (A) Optimied trusion Attachments (Align Technology, Fig. 2.11 (A) onverging buccal and lingual cron surfaces. (B) nde anta lara, A) on central incisors. (B) ingivallyoriented inclined sired aligner dislodgment during etrusive 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

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