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PRINCIPLES and

BIOMECHANICS of ALIGNER TREATMENT

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PRINCIPLES and

BIOMECHANICS of ALIGNER TREATMENT Ravindra Nanda, BDS, MDS, PhD Professor Emeritus Department of Orthodontics University of Connecticut Health Center Farmington, Connecticut, USA

Tommaso 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, FIRST EDITION Copyright © 2022 by Elsevier, Inc. All rights reserved.

ISBN: 978-0-323-68382-1

No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).

Notices Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds or experiments described herein. Because of rapid advances in the medical sciences, in particular, independent 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 contributors for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. ISBN: 978-0-323-68382-1

Content Strategist: Joslyn Dumas Content Development Manager: Ellen Wurm-Cutter Content Development Specialist: Rebecca Corradetti Publishing Services Manager: Shereen Jameel Project Manager: Nadhiya Sekar Design Direction: Patrick Ferguson Printed in India Last digit is the print number:

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To Catherine, for her love, support, inspiration, and encouragement. RN

To Katia, for showing me what love is and for keeping my feet on the ground. To Alessandro, Matilda, and Sveva, because you made the world a brighter place. To my friends, rancesco and 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 Ulm University Ulm, Germany

Researcher and Aggregate Professor Department of Clinical Sciences and ranslational edicine University of ome “or ergata” ome, taly

Sean K. Carlson, DMD, MS Associate Professor Department of Orthodontics School of Dentistry, University of the Pacic San Francisco, California, USA

Tommaso Castroorio, DDS, PhD, Ortho. Spec. Researcher and Aggregate Professor Department of Surgical Sciences, Postgraduate School of Orthodontics Dental School, University of orino orino, taly Orthodontics Unit San Giovanni attista ospital orino, taly

uan Palo ome Arano, DDS, MSc Associate Professor Orthodontics Program Universidad Autonoma de aniales aniales, Colomia

Mario reco, DDS, PhD Visiting Professor University of ’Auila ’Auila, taly Visiting Professor University of Ferrara Ferrara, taly

Chisato Dan, DDS

uis uanca, DDS, MS, PhD

Private Practice Smile nnovation Orthodontics oyo, apan

Research Associate Department of Orthodontics University of Geneva Geneva, Siterland

Iacopo Ciof, DDS, PhD Associate Professor Division of Graduate Orthodontics and Centre for ultimodal Sensorimotor and Pain esearch Faculty of Dentistry University of oronto oronto, Ontario, Canada

Daid Couchat, DDS, Ortho. Spec. Private Practice Cainet d’Orthodontie du dr Couchat arseille, France

osef Kucˇera, MDr., PhD Assistant Professor Department of Orthodontics Clinic of Dental edicine First edical Faculty Charles University Prague, Cech epulic Lecturer Department of Orthodontics Clinic of Dental edicine Palacý University Olomouc, Cech epulic

ae lkhol, DDS Senior Physician Department of Orthodontics Ulm University Ulm, Germany

rancesco arino, MD Ortho. Spec. Private Practice Studio Associato dottri Garino orino, taly

vi

ernd . apatki, DDS, PhD Department Head and hair Department of Orthodontics Ulm University Ulm, Germany

Contributors

vii

uca omardo, DDS, Ortho. Spec.

Simone Parrini, DDS, Ortho. Spec.

hairman and Professor Postgraduate School of Orthodontics University of Ferrara Ferrara, taly

Research Associate Department of Surgical Sciences, Postgraduate School in Orthodontics Dental School, University of orino orino, taly

Tianton ou, DMD, MSc Division of Gradual Orthodontics and Centre for ultimodal Sensorimotor and Pain esearch Faculty of Dentistry University of oronto oronto, Ontario, Canada

Serena aera, DDS, PhD, Ortho. Spec. Research Associate Department of Surgical Sciences, Postgraduate School in Orthodontics Dental School, University of orino orino, taly

Kam Malekian, DDS, MSc Private Practice Clinica io adrid, Spain

ianluca Mampieri, DDS, MS, PhD Researcher and Aggregate Professor Department of Clinical Sciences and ranslational edicine University of ome “or ergata” ome, taly

doardo Mantoani, DDS, Ortho. Spec. Research Associate Department of Surgical Sciences, Postgraduate School in Orthodontics Dental School, University of orino orino, taly

ariele ossini, DDS, PhD, Ortho. Spec. Research Associate Department of Surgical Sciences, Postgraduate School in Orthodontics Dental School, University of orino orino, taly

addah Saouni, DDS, Ortho. Spec. Private Practice Cainet d’Orthodontie du dr Saouni andol ivage Sanarysurer, France

Sila Schmidt, DDS Department of Orthodontics Ulm University Ulm, Germany

Io Marek, MDr., PhD Assistant Professor Department of Orthodontics Clinic of Dental edicine Palacý University Oloumouc, Cech epulic onsultant Department of Orthodontics Clinic of Dental edicine First edical Faculty Charles University Prague, Cech epulic

ör Schare, DDS, PhD, Ortho. Spec. Private Practice ieferorthopädische Prais Dr örg Schare Cologne, Germany

iuseppe Siciliani, MD, DDS hairman and Professor School of Dentistry University of Ferrara Ferrara, taly

Ali Tassi, Sc, DDS, MClD Ortho aindra anda, DS, MDS, PhD Professor Emeritus Division of Orthodontics Department of Craniofacial Sciences University of Connecticut School of Dental edicine Farmington, Connecticut, USA

Assistant Dean and hair Division of Graduate Orthodontics Schulich School of edicine and Dentistry he University of estern Ontario ondon, Ontario, Canada

ohnn Tran, DMD, MClD Keni Oima, DDS, MDSc Private Practice Smile nnovation Orthodontics oyo, apan

Division of Graduate Orthodontics Schulich School of edicine and Dentistry he University of estern Ontario ondon, Ontario, Canada

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Contributors

laio rie, DDS, MDentSc

enedict ilmes, DDS, MSc, PhD

onn rthodontics Alumnianda rthodontics Endoed hair Program Director and Chair Division of Orthodontics Department of Craniofacial Sciences University of Connecticut School of Dental edicine Farmington, Connecticut, USA

Professor Department of Orthodontics University of Düsseldorf Düsseldorf, Germany

Foreword Aligners represent the new frontier in the art and science of orthodontics. This new frontier offers new opportunities and challenges, but also requires the need for additional knowledge. A rethinking of biomechanics and force delivery concepts is needed along with the role of materials used for aligners. There is a need for combining established concepts with new tools and technologies which aligner treatment requires. When considering new methodologies, orthodontists should always remember that technology is a tool and not the goal. Diagnosis, treatment plan, and biomechanics are always the key elements of successful treatment, regardless of the treatment methodology. Aligner orthodontics is quite different than traditional methods with brackets and wires. orce delivery with aligners is through plastic materials. Thus, the knowledge of the aligner materials, physical properties, attachment design, and the sequentialiation protocol is crucial for treatment of malocclusions. t is also imperative to understand limitations of aligner treatment and how to overcome them with the use of miniscrews and auiliaries.

Aligner treatment requires new knowledge the number of clinical and scientic reports about all the different aspects of aligner orthodontics is increasing year by year. This book represents an up-to-date summary of the available research in the eld as well as a clinical atlas of treated patients based on the current evidence. We have made an attempt to provide benchmark for clinicians, researchers, and residents who want to improve their skills in aligner orthodontics. We would like to epress our great appreciation to all the friends and colleagues who have contributed to this book. t was a pleasure to work with all these talented orthodontists. We would like to say thank you to the lsevier team for their support, patience, and guidance during the challenging ovid pandemic. avindra anda Tommaso astroorio rancesco arino eni ima

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Contents 1 Diagnosis and Treatment Planning in the Three-Dimensional Era 1

12 The rid Approach in Class  Malocclusions Treatment 13

TOMMASO CASTROFLORIO, SEAN K. CARLSON, and FRANCESCO GARINO

FRANCESCO GARINO, TOMMASO CASTROFLORIO, and SIMONE PARRINI

2 Current Biomechanical Rationale Concerning Composite Attachments in Aligner Orthodontics 13 JUAN PABLO GOMEZ ARANGO

13 Aligners and mpacted Canines

14 Aligner Orthodontics in Prerestoratie Patients 1

3 Clear Aligners: Material tructures and Properties 3

KENJI OJIMA, CHISATO DAN, and TOMMASO CASTROFLORIO

MASOUD AMIRKHANI, FAYEZ ELKHOLY, and BERND G. LAPATKI

4 nuence o ntraoral actors on Optical and Mechanical Aligner Material Properties 3

15 oncompliance pper Molar Distaliation and Aligner Treatment or Correction o Class  Malocclusions 1 BENEDICT WILMES and JÖRG SCHWARZE

FAYEZ ELKHOLY, SILVA SCHMIDT, MASOUD AMIRKHANI, and BERND G. LAPATKI

5 Theoretical and Practical Considerations in Planning an Orthodontic Treatment ith Clear Aligners  TOMMASO CASTROFLORIO, GABRIELE ROSSINI, SIMONE PARRINI

6 Class  Malocclusion

16 Clear Aligner Orthodontic Treatment o Patients ith Periodontitis  TOMMASO CASTROFLORIO, EDOARDO MANTOVANI, and KAMY MALEKIAN

17 urger irst ith Aligner Therap

3

FLAVIO URIBE and RAVINDRA NANDA

1

MARIO GRECO

7 Aligner Treatment in Class  Malocclusion Patients  TOMMASO CASTROFLORIO, WADDAH SABOUNI, SERENA RAVERA, and FRANCESCO GARINO

8 Aligners in Etraction Cases

1

EDOARDO MANTOVANI, DAVID COUCHAT, TOMMASO CASTROFLORIO

18 Pain During Orthodontic Treatment: Biologic Mechanisms and Clinical Management  TIANTONG LOU, JOHNNY TRAN, ALI TASSI, and IACOPO CIOFFI

19 Retention and tailit olloing Aligner Therap 

3

JOSEF KUČERA and IVO MAREK

KENJI OJIMA, CHISATO DAN, and RAVINDRA NANDA

9 Open-Bite Treatment ith Aligners

20 Oercoming the imitations o Aligner Orthodontics: A rid Approach 



ALDO GIANCOTTI and GIANLUCA MAMPIERI

10 Deep Bite

LUCA LOMBARDO and GIUSEPPE SICILIANI

1

nde

LUIS HUANCA, SIMONE PARRINI, FRANCESCO GARINO, and TOMMASO CASTROFLORIO

11 nterceptie Orthodontics ith Aligners TOMMASO CASTROFLORIO, SERENA RAVERA, and FRANCESCO GARINO

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11



1

Diagnosis and Treatment Planning in the Three-Dimensional Era TOMMASO CASTROFLORIO, SEAN K. CARLSON, and FRANCESCO GARINO

Introduction rthodontics and dentofacial orthopedics is a specialty area of dentistry concerned with the supervision, guidance, and correction of the growing or mature dentofacial structures, including those conditions that reuire movement of teeth or correction of malrelationships and malformations of their related structures and the adustment of relationships between and among teeth and facial bones by the application of forces andor the stimulation and redirection of functional forces within the craniofacial comple. To accurately diagnose a malocclusion, orthodontics has adopted the problem-based approach originally developed in medicine. very factor that potentially contributes to the etiology and that may contribute to the abnormality or inuence treatment should be evaluated. nformation is gathered through a medical and dental history, clinical eamination, and records that include models, photographs, and radiographic imaging.  problem list is generated from the analysis of the database that contains a network of interrelated factors. The diagnosis is established after a continuous feedback between the problem recognition and the database Fig. .. ltimately, the diagnosis should provide some insight into the etiology of the malocclusion. rthodontics diagnosis and treatment planning are deeply changing in the last decades, moving from two-dimensional  hard tissue analysis and plaster cast review toward soft tissue harmony and proportions analyses with the support of three-dimensional  technology.  detailed clinical eamination remains the key of a good diagnosis, where many aspects of the treatment plan reveal themselves as a function of the systematic evaluation of the functional and aesthetic presentation of the patient. The introduction of a whole range of digital data acuisition devices cone-beam computed tomography T, intraoral and desktop scanner  and , and face scanner F, planning software computer-assisted design and computer-assisted manufacturing  software, new aesthetic materials, and powerful fabrication machines milling machines,  printers is changing the orthodontic profession Fig. .. s a result, clinical practice is shifting to virtual-based workows. Today it is common to perform virtual treatment planning and to translate the plans into treatment eecution with digitally driven appliance manufacture and placement using various  techniues from

printed models, indirect bonding trays, and custom-made brackets to robotically bend wires or aligners. Furthermore, it is becoming possible to remotely monitor treatment and to control it.5 The introduction of aligners in the orthodontics eld led the digital evolution in orthodontics. The two nouns evolution and revolution both refer to a change; however, there is a distinctive difference between the change implied by these two words. volution refers to a slow and gradual change, whereas revolution refers to a sudden, dramatic, and complete change. hat has been claimed as the “digital revolution” in orthodontics should be claimed as the “digital evolution” in orthodontics. rthodontics and biomechanics have always had the same denitions, and we as clinicians should remember that technology is an instrument, not the goal. This differentiates orthodontists from marketing people. The diagnosis and problem list is the framework that dictates the treatment obectives for the patient. nce formulated, the treatment plan is designed to address those obectives. n aligner orthodontics,  software displays treatment animations, helping the clinician to visualie the appearance of teeth and face that is desired as treatment outcome; however, those animations should be deconstructed by the orthodontist frame by frame or stage by stage, to dene how to address the treatment goal from mechanics to seuence. nly an accurate control of every single stage of the virtual treatment plan can produce reliable results. s usual, it is the orthodontist rather than the techniue itself that is responsible for the treatment outcome. ontemporary records should facilitate functional and aesthetic  evaluation of the patient.

Intraoral Scans and Digital Models s are uickly replacing traditional impressions and plaster models. These scanners generally contain a source of risk for inaccuracy because multiple single  images are assembled to complete a model. ecent studies, however, have shown that the trueness and precision of s of commercially available scanning systems are ecellent for orthodontic applications. igital models are as reliable as traditional plaster models, with high accuracy, reliability, and reproducibility Fig. .. 1

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Principles and Biomechanics of Aligner Treatment

Database

Models Intraoral scan

Clinical examination Chief complaint Medical history Dental history Extraoral exam Intraoral exam Functional exam

Photographs 3-D facial scan

Radiographic imaging CBCT

Problems

Problem List

Synthesis and diagnosis

Treatment objectives

Mechanics plan: which movements with which auxiliaries

Staging definition

Treatment prescription

Virtual setup Virtual patient

Treatment re-evaluation

Fig. 1.1 Steps in diagnosis and treatment planning in the digital orthodontics era. (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 orthodontic software platforms to allow the orthodontist to perform virtual treatment plans and eplore various treatment plans within minutes as opposed to epensive and time-consuming diagnostic setups and waups. erforming digital setups not only allows the clinician to eplore a number of treatment options in a simple manner but also facilitates better communication with other dental professionals, especially in cases that reuire combined orthodontic and restorative treatments. The virtual treatment planning also allows for better communication with patients and allows them to visualie the treatment outcome and understand the treatment process.5 Further advantages of virtual models of the dental arches are related to study model analysis, which is an essential step in orthodontic diagnostics and treatment planning. ompared to measurements on physical casts using a

measuring loop andor caliper, digital measurements on virtual models usually result in the same therapeutic decisions as evaluations performed the traditional way. Furthermore, with their advantages in terms of cost, time, and space reuired, digital models could be considered the new gold standard in current practice. igital impressions have proven to reduce remakes and returns, as well as increase overall efciency. The patient also benets by being provided a far more positive eperience. urrent development of novel scanner technologies e.g., based on multipoint chromatic confocal imaging and dual wavelength digital holography will further improve the accuracy and clinical practicability of . ecently near infrared  technology has been integrated in . The  is the region of the electromagnetic spectrum between . and  mm Fig. .. The interaction of 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 scanner uses light of 850nm that penetrates into the tooth structure to produce a NIRI image

NIRI image of a healthy tooth

Image interpretation - Healthy tooth Enamel is mostly transparent to NIRI and appears dark

Dentin is mostly scattering to NIRI and appears bright

Image interpretation - Tooth with caries

ealthy enamel appears dark

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 transparent to  due to the reduced scattering coefcient of light, allowing it to pass through its entire thickness and present as a dark area, whereas the dentin appears bright due to the scattering effect of light caused by the orientation of the dentinal tubules. ny interferencespathologic lesionsareas of demineraliation appear as bright areas in a  image due to the increased scattering within the region. Therefore  provides information regarding possible decays without any -ray eposure. Through the use of digital impression making, it has been determined that laboratory products also become more consistent and reuire less chair time at insertion.

3D Imaging CONE-BEAM COMPUTED TOMOGRAPHY  imaging has evolved greatly in the last two decades and has found applications in orthodontics as well as in oral and maillofacial surgery. n  medical imaging, a set of anatomic data is collected using diagnostic imaging euipment, processed by a computer and then displayed on a  monitor to give the illusion of depth. epth perception causes the image to appear in . ver the last 5 years, T imaging has emerged as an important supplemental radiographic techniue for orthodontic diagnosis and treatment planning, especially in situations that reuire an understanding of the comple anatomic relationships and surrounding structures of the maillofacial skeleton. From the introduction of the cephalostat, roadbent stressed the need for a perfect matching of the lateral and posteroanterior -rays to obtain a perfect  reproduction of the skull. T imaging provides uniue features and advantages to enhance orthodontic practice over conventional etraoral radiographic imaging. ateral cephalometrics provides information on the sagittal and vertical aspects of the malocclusion with little contribution about unilateral or transversal discrepancies. The latter seem to be related to

urbaniation and industrialiation becoming more freuent in the last decades.-5 Therefore, the need for a diagnostic tool providing information on the  aspects of the dentoskeletal malocclusion is increasing. hile the clinical applications span from evaluation of anatomy to pathology of most structures in the maillofacial area, the key advantage of T is its high-resolution images at a relatively lower radiation dose. posing patients to -rays implies the eistence of a clinical ustication and that all the principles and procedures reuired to minimie patient eposure are considered. The  concept should always be kept in mind  is an acronym used in radiation safety for as low as reasonably achievable. This concept is supported by professional organiations as well as by government institutions.  ecogniing that diagnostic imaging is the single greatest source of eposure to ioniing radiation for the  population that is controllable, the ational ommission on adiation rotection and easurements has introduced a modication of the  concept.  represents as low as diagnostically acceptable. mplementation of this concept will reuire evidence-based udgments of the level of image uality reuired for specic diagnostic tasks as well as eposures and doses associated with this level of uality. ittle research is currently available in this area. For  imaging modalities used in orthodontics, the radiation dose for panoramic imaging varies between  and  µv, while a cephalometric eam range is between  and 5 µv.  full mouth series ranges from  to 5 µv based on the type of collimation used. hile  and  radiation doses are often compared for reference, they cannot truly be compared because the acuisition physics and the associated risks are completely different and cannot be euated. The actual risk for low-dose radiographic procedures such as maillofacial radiography, including T, is difcult to assess and is based on conservative assumptions as there are no data to establish the occurrence of cancer following eposure at these levels. owever, it is generally accepted that any increase in dose, no matter how small,



Principles and Biomechanics of Aligner Treatment

results in an incremental increase in risk. Therefore there is no safe limit or safety one for radiation eposure in orthodontic diagnostic imaging.  recent meta-analysis about the effective dose of dental T stated that the mean adult effective doses grouped by eld of view F sie were  µv large,  µv medium, and  µv small. ean child doses were 5 µv combined large and medium and  µv small. arge differences were seen between different T units. The merican ental ssociation ouncil on cientic ffairs  proposed a set of principles for consideration in the selection of T imaging for individual patient care. ccording to the guidelines, clinicians should perform radiographic imaging, including T, only after professional ustication that the potential clinical benets will outweigh the risks associated with eposure to ioniing radiation. owever, T may supplement or replace conventional dental -rays when the conventional images will not adeuately capture the needed information. ecently, a number of manufacturers have introduced T units capable of providing medium or even full F T acuisition using low-dose protocols. y adustments to rotation arc, m, kp, or the number of basis images or a combination thereof, T imaging can be performed at effective doses comparable with conventional panoramic eaminations range, – µv. This is accompanied by signicant reductions in image uality; however, viewer software can be helpful in improving the clinical eperience with low-uality images. ven at this level, child doses have been reported to be, on average,  greater than adult doses. The use of low-dose protocols may be adeuate for low-level diagnostic tasks such as root angulations.

BENEFT OF CBCT FOR ORTHODONTC AEMENT The benets of T for orthodontic assessment include accuracy of image geometry. T offers the distinct advantage of  geometry, which allows accurate measurements of obects and dimensions. The accuracy and reliability of measurements from T images have been

demonstrated, allowing precise assessment of unerupted tooth sies, bony dimensions in all three planes of space, and even soft tissue anthropometric measurements— things that are all important in orthodontic diagnosis and treatment planning.- The accurate localiation of ectopic, impacted, and supernumerary teeth is vital to the development of a patientspecic treatment plan with the best chance of success. T has been demonstrated to be superior for localiation and space estimation of unerupted maillary canines compared with conventional imaging methods.5  ne study indicated that the increased precision in the localiation of the canines and the improved estimation of the space conditions in the arch obtained with T resulted in a difference in diagnosis and treatment planning toward a more clinically orientated approach.5 T imaging was proven to be signicantly better than the panoramic radiograph in determining root resorption associated with canine impaction.  ne study supported improved root resorption detection rates of  with the use of T when compared with  imaging. hen used for diagnosis, T has been shown to alter and improve the treatment recommendations for orthodontic patients with impacted or supernumerary teeth.  ased on the ndings of a recent review and in accordance with the T entomaillofacial aediatric maging n nvestigation Towards ow ose adiation nduced isks proect, T can be considered also in children for diagnosis and treatment planning of impacted teeth and root resorption Fig. .5. aillary transverse deficiency may be one of the most pervasive skeletal problems in the craniofacial region. ts many manifestations are encountered daily by the orthodontist. lthough many analyses of the lateral cephalometric headlm have been developed for use in orthodontic and orthognathic treatment planning, the posteroanterior cephalogram has been largely ignored. The diagnosis of transverse discrepancy is uite challenging in the daily practice because of several methodologic limitations of the proposed methods.

Fig. 1.5 Cone-beam computed tomography data elaboration for enhancing diagnosis and treatment planning.

1 • iagnosis and Treatment Planning in the Three-imensional ra



Fig. 1. Case of impacted 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 different tooth level, buccolingual inclination of each tooth, and root positions in the alveolar bone can be determined and evaluated from the T Fig. .. ith this information, the clinician can make a proper diagnosis and treatment plan for the patient. The temporomandibular oint T can be assessed for pathology more accurately with T images than with conventional radiographs. The T volume for orthodontic assessment will generally include the T and therefore is available for routine review. everal retrospective analyses of T volumes indicate 5 to  of incidental ndings are related to T Fig. ., which is signicant enough for further follow-up or referral. T data can also be used to obtain the volumetric rendering of the upper airways. tudies of the upper airway based on T scans are considered to be reliable in dening the border between soft tissues and void spaces i.e., air, thus providing important information about the morphology i.e., cross-sectional area and volume of the pharyngeal airway5 Fig. .. owever, despite the potentials offered by the techniue in this eld and the potential role of orthodontists as sentinel physicians for sleep breathing disorders, limited, poor uality, and low evidence level literature is available on the effect of head posture and tongue position on upper airway dimensions and morphology in  imaging. atural head position at T acuisition is the suggested standardied posture. owever, for repeatable measures of upper airway volumes it may clinically be difcult to obtain. ndications and methods related to tongue position and breathing during data acuisition are still lacking. Furthermore, a recent study focusing on the reliability of airway measurements stated that the oropharyngeal airway volume was the only parameter found to have generalied ecellent intra-eaminer and inter-eaminer reliability. n orthognathic surgery, igital maging and ommunications in edicine  data from T can be used to fabricate physical stereolithographic models or to generate virtual  models. The  reconstructions are etremely useful in the diagnosing and treatment planning of facial

asymmetry cases. They can also be used to generate substitute grafts when warranted. T can be useful as a valuable planning tool from initial evaluation to the surgical procedure and then the correction of the dental component in the surgery-rst orthognathic approach. n addition, databases may be interfaced with the anatomic models to provide characteristics of the displayed tissues to reproduce tissue reactions to development, treatment, and function. The systematic summariation of the results presented in the literature suggests that computeraided planning is accurate for orthognathic surgery of the mailla and mandible, and with respect to the benets to the patient and surgical procedure it is estimated that computer-aided planning facilitates the analysis of surgical outcomes and provides greater accuracy Fig. ..  recent systematic review was conducted to evaluate whether T imaging can be used to assess dentoalveolar relationships critical to determining risk assessment and help determine and improve periodontal treatment needs in patients undergoing orthodontic therapy. The conclusion was that pretreatment orthodontic T imaging can assist clinicians in selecting preventive or interceptive periodontal corticotomy and augmentation surgical reuirements, especially for treatment approaches involving buccal tooth movement at the anterior mandible or maillary premolars to prevent deleterious alveolar bone changes. This assumption seems more suitable for skeletally mature patients presenting with a thin periodontal phenotype prior to orthodontic treatment Fig. ..

3D FACA RECONTRUCTON TECHNUE The accurate acuisition of  face appearance characteristics is important to plan orthognathic surgery, and ecellent work is based on an eact  face modeling.  precise approach to  digital face prole acuiring, which is applied to simulate and design an optimal plan for face surgery by modern technologies such as , is reuired. Three types of  face modeling methods are currently 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 prescribed 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 optical  sensing techniue. The  reconstruction method based on T technology is sensitive to the skeleton and can be conveniently utilied for craniofacial plastics, as well as the oral and maillofacial correction of abnormalities. oft tissue data etraction, or segmentation, can be created using a dedicated software. For orthodontic purposes, the image should be recorded with eyes open and with the patient smiling. The smiling image will permit the use of dental landmarks to superimpose the digital models on the  face reconstruction for treatment planning purposes. ovel technologies aiming at acuiring facial surface are available. tereophotogrammetry and laser scanning allow operators to uickly record facial anatomy and to perform a wider set of measurements5 not eposing patients to radiation Fig. .. tereophotogrammetry still represents the gold standard with respect to laser scanning at least for orthodontic applications since it is characteried by good precision and reproducibility, with random errors generally less than  mm.5 ith this method,  images are acuired by combining photographs captured from various angles with synchronous digital cameras, with the main advantage of reducing possible motion artifacts. The main limitation at this stage is represented by the high cost of the instrumentation. ccording to arver and acobson and arver and ckerman, it may be inappropriate to place everyone in the same esthetic framework and even more problematic to attempt this based solely on hard tissue relationships since the soft tissues often fail to respond predictably to hard tissue changes. ntegrating T data, facial  reconstruction,

and digital models with specic simulation software will provide useful indications in relation to orthodontic treatment results and the eventual need of interdisciplinary intervention.

RTUA ETUP everal software programs are available on the market to create virtual setups able to produce the seuence of physical models on which thermoforming plastic foils are used to create aligners. etup accuracy is improved when virtual teeth segmentation is applied on digital models obtained by  or digitiation of plaster casts, reducing the loss of tooth structure observed during the cutting process of the plaster in conventional plaster and wa setups. The segmentation process starts with marking mesial and distal points on each tooth or simply indicating the center of the crown on the occlusal view of the arches, depending on the software used. Then the software generally identies the gingival margin. Teeth segmentation and the tooth-tooth-gingiva segmentation are eecuted semiautomatically, but the operator can always correct the automatic process. nce teeth are segmented they are separated from the gingiva, and a mean virtual root shape and length are derived from proprietary databases is applied. ecently, virtual setup software programs are starting to use real root morphologies derived from patient T data when available. Tooth segmentation from T images in those cases is a fundamental step. ecent engineering innovations made the process simple and timesaving with respect to the past.

1

Principles and Biomechanics of Aligner Treatment

Fig. 1.1 Cone-beam computed tomography data used to plan an orthodontic 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imal contacts dened, the arch form is adusted using software tools that can create an individual arch form. igital arch templates are also available, while several software programs consider the  an acronym for ill ndrews and arry ndrews ridge. The occlusal plane as well as the original vertical plane are used as reference. ach tooth can be moved in the space since the reuired nal position has been achieved. t is important to mention that tooth movements on computers are unlimited. Tooth alignment and leveling can be planned on the computer screen, but this result may not be realistic for that specic patient. bviously, tooth movement has its biologic limitations. n the basis of the used system the virtual setup could be prepared by a trained dental technician or by a software epert; however, every setup should be based on biologic principles and on a biomechanics background making the orthodontist the initial designer and the nal reviewer of every setup. s progress in digital imaging 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. ..

novel  superimposition techniues, clinicians are able to simulate the outcome of both the osseous structures and the soft tissue posttreatment. The  data integration makes the diagnostic process and the treatment planning more accurate and complete, provides an effective communication tool and a method for patients to visualie the simulated outcomes, instills motivation, and encourages compliance to achieve the desired treatment outcome Fig. .. hat technology is providing to orthodontists is amaing; however, what is still missing is the fourth dimension i.e., the dynamic movements of the mandible and the surrounding tissues integrated in the virtual model. dealistically, the capture of digital data for virtual modeling should happen in a one-step, single-device approach to improve accuracy. Future research will ll this gap and will realie the dream of the real virtual patient.

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 photographic facial images and high-resolution surface models of the dentition produced by direct scans intraorally or indirectly by scanning impressions or study models. The integration of hard and soft tissues can provide a greater understanding of the interrelationship of the dentition and soft tissues to the underlying osseous frame. ndividual  models of tooth are needed for the computer-aided orthodontic treatment planning and simulation. ith the

Fig. 1.13 The virtual patient in hich cone-beam computed tomography data, facial three-dimensional reconstruction, and virtual setup obtained after teeth segmentation are superimposed. Courtesy of dr. Alain Souchet, ulhouse, rance.

12

Principles and Biomechanics of Aligner Treatment

References . merican ssociation of rthodontists. linical practice guidelines for orthodontics and dentofacial orthopedics. ; . https www.aaoinfo.orgdappsget-led5 . ribe F, handhoke T, anda . ndividualied orthodontic diagnosis. n anda , ed. Esthetics and iomechanics in Orthodontics. nd ed. t ouis,  lsevier aunders; 5-. . arver , anoski . pecial considerations in diagnosis and treatment planning. n raber , anarsdall , ig , eds. Orthodontics urrent Principles and echniues. 5th ed. hiladelphia,  osby; 5-. . angano , uongo F, igliario , et al. ombining intraoral scans, cone beam computed tomography and face scans the virtual patient. J raniofac Surg. ;-. 5. Tarraf , aredeliler . resent and the future of digital orthodontics. Semin Orthod. ;-5. . ossini , arrini , astroorio T, et al. iagnostic accuracy and measurement sensitivity of digital models for orthodontic purposes a systematic review. Am J Orthod Dentofacial Orthop. ;-. . laus , adeke , int , et al. eneration of  digital models of the dental arches using optical scanning techniues. Semin Orthod. ;-. . ühnisch , öchtig F, itchika , et al. n vivo validation of nearinfrared light transillumination for interproimal dentin caries detection. lin Oral nvestig. ;-. . ayar , ahadevan .  paradigm shift in the concept for making dental impressions. J Pharm ioallied Sci. 5;-5. . aeer , illett T, youb F, et al. pplications of  imaging in orthodontics part . J Orthod. ;-. . roadbent .  new -ray techniue and its application to orthodontia. Angle Orthod. ;5-. . carfe , evedo , Toghyani , et al. one beam computed tomographic imaging in orthodontics. Aust Dent J. ;-5. . orruccini , Flander , aul . outh breathing, occlusion, and moderniation in a north ndian population. n epidemiologic study. Angle Orthod. 5;55-. . amporesi , arinelli , aroni , et al. ental arch dimensions and tooth wear in two samples of children in the 5s and s. r Dent J. ;e. 5. indsten , gaard , arsson . Transversal dental arch dimensions in -year-old children born in the s and the s. Am J Orthod Dentofacial Orthop. ;5-5. . Tadinada , chneider , adav . ole of cone beam computed tomography in contemporary orthodontics. Sem Orthod. ; -5. . merican ental ssociation ouncil on cientic ffairs. The use of cone-beam tomography in dentistry. n advisory statement from the merican ental ssociation ouncil on cientic ffairs. J Am Dent Assoc. ;-. . orner . TT guideline development panel. n one eam  for Dental and Maillofacial Radiolog Evidence ased uidelines Radiation Protection Series. uembourg uropean ommission irectorate-eneral for nergy; 5. . udlow , Timothy , alker , et al. ffective dose of dental T—a meta-analysis of published data and additional data for nine T units. Dentomaillofac Radiol. 5;. . alentin . The  recommendations of the nternational ommission on adiological rotection. ublication . Ann RP. ;-. . udlow , alker . ssessment of phantom dosimetry and image uality of i-T F cone-beam computed tomography. Am J Orthod Dentofacial Orthop. ;-. . erco , igali r , iner , et al. ccuracy and reliability of linear cephalometric measurements from cone-beam computed tomography scans of a dry human skull. Am J Orthod Dentofacial Orthop. ;,e-e. . Fourie , amstra , errits , et al. ccuracy and repeatability of anthropometric facial measurements using cone beam computed tomography. left Palate raniofac J. ;-. . agravère , arey , Toogood , et al. Three-dimensional accuracy of measurements made with software on cone-beam computed tomography images. Am J Orthod Dentofacial Orthop. ;-. 5. otticelli , erna , attaneo , et al. Two-versus three-dimensional imaging in subects with unerupted maillary canines. Eur J Orthod. ;-.

. odges , tchison , hite . mpact of cone-beam computed tomography on orthodontic diagnosis and treatment planning. Am J Orthod Dentofacial Orthop. ;5-. . go TT, Fishman , ossouw , et al. orrelation between panoramic radiography and cone-beam computed tomography in assessing maillary impacted canines. Angle Orthod. ;-. . awad , armichael F, oughton , et al.  review of cone beam computed tomography for the diagnosis of root resorption associated with impacted canines, introducing an innovative root resorption scale. Oral Surg Oral Med Oral Pathol Oral Radiol. ;5-. . aney , ansky , ee , et al. omparative analysis of traditional radiographs and cone-beam computed tomography volumetric images in the diagnosis and treatment planning of maillary impacted canines. Am J Orthod Dentofacial Orthop. ;5-5. . e rauwe , ya , huaat , et al. T in orthodontics a systematic review on ustication of T in a paediatric population prior to orthodontic treatment. Eur J Orthod. ;-. doi.eocy. . enning , acobs , auwels , et al. one-beam T in paediatric dentistry T proect position statement. Pediatr Radiol. ;-. . camara . aillary transverse deciency. Am J Orthod Dentofacial Orthop. ;5-5. . iner , l abandi , igali , et al. one-beam computed tomography transverse analysis. art  normative data. Am J Orthod Dentofacial Orthop. ;-. . arson . one-beam computed tomography is the imaging techniue of choice for comprehensive orthodontic assessment. Northwest Dent. ;-. 5. hokri , iresmaeili , hmadi , et al. omparison of pharyngeal airway volume in different skeletal facial patterns using cone beam computed tomography. J lin Ep Dent. ;ee. . urani F, i arlo , attaneo , et al. ffect of head and tongue posture on the pharyngeal airway dimensions and morphology in three-dimensional imaging a systematic review. J Oral Maillofac Res. ;e. . immerman , ora , liska T. eliability of upper airway assessment using T. Eur J Orthod. ;-. . aas r , ecker , de liveira . omputer-aided planning in orthognathic surgery-systematic review. nt J Oral Maillofac Surg. ;-5-5. . andelaris , eiva , hambrone . one-beam computed tomography and interdisciplinary dentofacial therapy an merican cademy of eriodontology best evidence review focusing on risk assessment of the dentoalveolar bone changes inuenced by tooth movement. J Periodontol. ;-. . chmeleisen , chramm . omputer-assisted reconstruction of the facial skeleton. Arch acial Plast Surg. ;5. . ell . omputer planning and intraoperative navigation in craniomaillofacial surgery. Oral Maillofac Surg lin North Am. ;5-5. . irshmüller , nnocent , aribaldi . eal-time correlation-based stereo vision with reduced border errors. nt J omput is. ;-. . ou , hen , hang , et al. eal-time and high-resolution  face measurement via a smart active optical sensor. Sensors asel. ;e. . Troulis , verett , eldin , et al. evelopment of a three-dimensional treatment planning system based on computed tomographic data. nt J Oral Maillofac Surg. ;-5. 5. ibelli , ucciarelli , oppa , et al. Three-dimensional facial anatomy evaluation reliability of laser scanner consecutive scans procedure in comparison with stereophotogrammetry. J raniomaillofac Surg. ;-. . arver , acobson . The aesthetic dentofacial analysis. lin Plast Surg. ;-. . arver , ckerman . ynamic smile visualiation and uantication part . mile analysis and treatment strategies. Am J Orthod Dentofacial Orthop. ;-. . ia , an , hang , et al. ndividual tooth segmentation from T images scanned with contacts of maillary and mandible teeth. omput Methods Programs iomed. ;-. . amardella T, othier , ilella , et al. irtual setup application in orthodontic practice. J Orofac Orthop. ;-.

2

Current Biomechanical Rationale Concerning Composite Attachments in Aligner Orthodontics JUAN PABLO GOMEZ ARANGO

Introduction he orthodontic techniue that we now call “aligner orthodontics” has evolved considerably over the last  years. mprovements in behavior of aligner plastics, treatment planning software, and three-dimensional 3 printing have served one basic but fundamental intention to mitigate the biomechanical limitations inherent to aligner-based tooth movement. nother signicant development designed to overcome the aforementioned biomechanical shortcomings of aligner systems has been the continuous improvement of biomechanically complementary composite attachments. ttachments were conceived to produce supplementary force vectors that, when applied to teeth by the aligner material, transform the resultant system, allowing complex tooth movements. he application of one of the initial geometric congurations was initially presented by the clinical team from lign echnology nc., as basic  x 3 mm rectangular structures, bonded to the lower incisor buccal surface, in an attempt at controlling undesired tipping during space closure after incisor extraction ig. .. s the incisors adacent to the extraction space begin to incline mesially, the rigid, xed structure of the attachment collides with aligner plastic, producing force couples that counteract the initial moment, reducing undesired tipping see ig. .. rthodontic tooth movement with conventional bracket techniues can deliver sophisticated force systems due to the manner in which the rigid ligature-archwire-bracket scheme “grasps” the malaligned tooth. his particular arrangement allows broad control of magnitude and direction of applied force vectors, and, conseuentially, of tooth movement ig. .. t is important to keep in mind that attachments work, not as active agents that produce forces, but by passively “getting in the way” of plastic as it elastically deforms due to lack of coincidence between tooth position and aligner material “mismatch”, establishing the force vector that subseuently affects the tooth ig. .3. iomaterials used for attachment fabrication must assure that reuirements in adhesion, wear resistance, and esthetics are fullled.  recent study suggests that contemporary microlled resin composites provide sufcient

wear resistance to deliver a stable attachment shape during treatment, assuring its functionality. Mantovani et al.3 also concluded that the use of bulk-lled resins for attachment fabrication improved dimensional stability when compared to low-viscosity resins, which experience higher polymerization shrinkage. he use of translucent composites generally provides sufcient esthetic acceptance and stain resistance as long as an adeuate bonding techniue is executed, in which voids bubbles in attachment surface and excessive residue ash left on tooth surface are avoided. everal considerations come into play when determining the optimal attachment design for a specic clinical obective geometry, location, and size.

Geometry (Active Surface Orientation) t the time of aligner insertion, orthodontic forces will be produced in response to the particular complex pattern of mismatches between plastic and tooth structure. his pattern of mismatch–plastic deformation–orthodontic force is critical for attachment design during digital simulation to produce specic areas active surfaces that will contact aligner plastic with predetermined force magnitudes, producing the desired force vectors and conseuent tooth movements. ot all the surface area of attachments will be in direct contact with the aligner. he active or functional surfaces can and should be determined with thoughtful biomechanical intentionality, in accordance with clinical obectives ig. .. hile the magnitude of the force produced is determined by the amount of mismatch along with the characteristics of aligner material, the direction of the force will depend on the orientation of the active surface. he principles of mechanics state that the direction of the normal component of the contact force the vector that in this case acts upon the active surface of the attachment will always be perpendicular to that surface see ig. .. dentifying the direction of these complementary force vectors is essential for treatment planning, especially when more than one force acts simultaneously. n these cases, the resultant forces must be properly recognized to deliver predictable tooth movements see ig. .. 13

14

Principles and Biomechanics of Aligner Treatment

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C B Fig. 2.1 (A) Mesial tipping moments (red curved arrows) produced by aligner forces (red arrows) occurring during space closure. Antitipping moments (blue curved arrows) produced by forces (blue arrows) acting at rectangular vertical attachments (B). Opposing moments are canceled out, promoting bodily movement.

Fig. 2.3 (A) Alignertooth mismatch. (B) lastic aligner deformation and activation of forces upon aligner insertion. () Tooth alignment after aligner seuence.

Location

Fig. 2.2 The typical force couple generated during bracetbased alignment of rotated tooth ith a fully engaged . iTi archire consists of to force vectors one that pushes against the posterior all of the slot (red arrow) and a second that pulls aay from the same all (blue arrow)

ased on the premise that the magnitude of a moment is proportional to the perpendicular distance between the line of action and the center of resistance, to fully understand the effect of aligner-based orthodontic forces being applied in any particular moment, it is essential to establish this distance in the three planes of space. nce this correlation has been clearly established and 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 mesiodistal tipping and intrusion. n a case in which mesiolingual rotation of the tooth is reuired, localization of attachment  will produce a strong mesial tipping moment and a weak mesiolingual rotational moment ig. .. n this specic clinical situation, a better alternative would be with attachment location , in which modication in distance from line of action to center of resistance would reduce tipping

2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics

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C

B

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 capacity see ig. .. nother example of the inuence of attachment localization is observed during transverse arch expansion, when buccal tipping of posterior segments is detrimental to treatment obectives.  recent unpublished nite element analysis  study of the mechanical effects of the bonding position of rectangular horizontal attachments found that the resultant tipping moment acting on the molars was greater when located on the lingual surface of the rst upper molars versus the labial surface ig. ..

Size ttachment size is important because of its mechanical and esthetic implications. mall congurations are desirable because they are less noticeable however, as size diminishes, so does the ability to produce predictable forces due to reduced active surface area. n the other hand, larger attachment designs are desirable because of their increased biomechanical capabilities, but they result in increased aligner retention with subseuent patient discomfort and negative esthetic perception, especially with highprole congurations in anterior teeth.

16

Principles and Biomechanics of Aligner Treatment

B

A

Fig. 2.6 uring epansion, labial attachment location (A) produced smaller net buccal molar tipping moments than lingually bonded attachments (B).

Functions PROVIDING ALIGNER RETENTION or aligner-based orthodontic forces to affect teeth as conceived in digital simulation, the aligner must be stably seated after insertion and remain so for the duration of treatment. ccasionally, decient adaptation of the aligner may occur, usually resulting from faulty fabrication, but may also occur due to the many reactive forces produced once properly tted. or example, as a freuent response to intrusive forces acting on the posterior teeth, the aligner will tend to be dislodged in the anterior segment, and vice versa. he use of intermaxillary elastics, especially when they are engaged directly to the aligner, will also tend to vertically dislodge it in the direction of the elastic force. onding retentive attachments on teeth adacent to those receptors of the elastic force is recommended to maintain proper aligner engagement ig. ..  study by ones et al. suggests that the optimal attachment conguration, when high aligner retention is imperative, is a

A

nongingivally beveled such as a horizontal rectangular or occlusally beveled design, as close to the gingival margin as possible see ig. .. s a general rule of attachment design, occlusal beveling will facilitate aligner insertion due to the inclined plane conguration as well as increase force and discomfort reuired for aligner removal.

AVOIDING ALIGNER “SLIPPING” specially when rotating rounded teeth, the sum of a series of tangential forces is responsible for tooth movement ig. ., causing inconvenient displacement slipping of the aligner in relation to the tooth surface, reducing the system’s efcacy and predictability, and resulting in lack of full expression of digitally planned rotation with the tooth lagging behind the corresponding aligner stage. linically, incomplete rotation and loss of tracking will be observed, manifesting as a space between tooth and plastic see ig. .. ppropriately designed attachments can help the aligner lock in to the tooth crown, greatly reducing this undesired slipping effect.

B Fig. 2.7 (A) Attachments located on teeth 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

A

B

Fig. 2.8 (A) Multiple tangential forces (red arrows) acting during alignerbased, bicuspid rotation. (B) ue to slipping effect, incomplete epression of epected rotation ith space beteen tooth and aligner (in yellow) ill be observed.

DELIVERING PREDETERMINED FORCE VECTORS he fundamental purpose of composite attachments in aligner orthodontics is to produce specic, complementary force vectors reuired for predictable tooth movement, which are not possible with the sole use of aligners thermoformed with existing materials ig. ..

17

nfortunately, to harness the full clinical potential of bonded attachments, current polymers have yet to resolve limitations associated with their viscoelastic and hygroscopic nature. nce inserted, the initial force produced by the aligner after it is elastically deformed is not constant and will decline with time. his time-dependent reduction of force under constant deformation is called stress relaxation.  ot 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 deformation of the aligner material is evident. his time-dependent plastic deformation under constant force is called creep and is attributed to reorganization of polymer chains. t is important to underline that this permanent deformation, so detrimental to clinical performance of plastic aligners, is not caused by a violation of the materials’ elastic limit but is due to a time-dependent, mechanochemical phenomenon of a different nature. his inherent aw of aligner plastics is the maor cause behind the inconsistent force levels and plastic deformation that result in one of the most dreaded occurrences for orthodontists practicing aligner orthodontics, now commonly referred to as loss of tracking. ig. . illustrates an example of the clinical manifestations of this complex reality in which mesiolingual rotation and extrusion of a rst upper left bicuspid were incorporated in the digital treatment plan but did not fully occur. he lack of coincidence between the attachment and its corresponding recess in the aligner is unambiguous evidence of loss of tracking, a contingency that in many cases must be resolved by obtaining updated digital dental models from which a new treatment seuence must be designed.

Basic Attachment Conurations in Current Ainer Orthodontics he evolution of attachments, derived from a better understanding of the effect of geometry, location, and size of the composite structure, has resulted in a diverse array of congurations with well-dened biomechanical obectives.

VERTICAL CONTROL

A

B

Fig. 2.9 (A) Properly designed attachments produce complementary force vectors reuired for predictable tooth movement. (B) Polymer stress relaation and creep, along ith incomplete rotation and unin tended force (blue arrow), may occur during seuence of aligner based, tooth rotation stages.

he tendency of conventional xed orthodontics to increase vertical dimension, especially in open-bite patients with increased anterior facial height, has been studied. ligner-based treatment has proven to be an effective alternative for open-bite correction-3 with encouraging results.3 uccessful treatment often includes the sum of complementary clinical strategies such as the combined effect of counterclockwise mandibular rotation, posterior intrusion, and anterior extrusion.

18

Principles and Biomechanics of Aligner Treatment

A

B Fig. 2.1 (A) mage from 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 effects such as root resorption, periodontal deterioration, instability, and unfavorable esthetics.  long with these clinical restrictions, aligner extrusion poses mechanical limitations in anterior teeth in which buccal and lingual crown surfaces converge towards the incisal edge ig. ., facilitating aligner dislodgement and rendering this type of tooth movement virtually impossible see ig. . without the use of supplementary composite attachments.  gingivally oriented, inclined plane conguration ig. . provides a force system that improves predictability of this 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

A

A

B B

Fig. 2.11 (A) onverging buccal and lingual cron surfaces. (B) nde sired aligner dislodgment during etrusive movement.

Fig. 2.12 (A) Optimied trusion Attachments (Align Technology, anta lara, A) on central incisors. (B) ingivallyoriented inclined plane ith optimal active surface angulation.

2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics

19

150° 110°

A

B

Fig. 2.13 (A) orces transmitted by the aligner (red arrows) and resultant forces (purple arrows) acting on the tooth. (B) A reduction of the angle beteen active attachment surface and buccal tooth surface produces stronger resul tant etrusive forces.

incisor is derived from the two red arrows that represent buccal and lingual forces present during aligner-based extrusion ig. .3. educing the angle formed by the active surface of the attachment and the buccal surface of the tooth will result in a stronger resultant force see ig. .3. linicians must be wary of excessive reduction of this angle, which along with excessive force may produce difculty of aligner-attachment engagement with the ensuing localized plastic deformation.

POSTERIOR INTRSION ecent studies suggest that the presence of interocclusal plastic during aligner treatment  may produce a bite-block effect that potentiates bite closure and posterior intrusion capabilities. his improves treatment outlook, especially in cases in which anterior extrusion is not desirable and intrusion of posterior teeth, with the conseuent mandibular rotation, are to be considered as part of the strategy for bite closure. s mentioned previously, intrusive forces acting in the posterior region will tend to dislodge the aligner in the occlusal direction. ven with light posterior intrusive forces, an opposite, reactive force should be expected in the anterior arch that will tend to vertically dislodge the aligner ig. .. ingivally positioned rectangular horizontal or occlusally attachments beveled towards the incisal edge should provide the necessary aligner stability for optimal treatment progress.

FIRSTORDER CONTROL Ri otation of teeth with rounded anatomies such as bicuspids and molars is another movement particularly difcult to accomplish with plastic aligners without the help

Fig. 2.14 ntrusion in the posterior segment (red arrows) produces reactive forces that ill tend to dislodge the aligner anteriorly (blue arrows). Adeuate attachment selection on anterior teeth ill counter act this undesired occurrence.

of specialized attachments, which improve biomechanical capabilities. he limitations associated with rounded crown morphologies are due to some extent to three particular realities n

s mentioned previously, in rounded crown congurations, the tangential nature of the forces produced during aligner-based tooth rotation, along with very

2

n

n

Principles and Biomechanics of Aligner Treatment

low coefcient of friction between the two surfaces, facilitates a slipping effect between the aligner and tooth. he line of action of the normal force vectors resultant from tangential forces delivered during rotation of rounded crowns crosses at a short distance from the center of resistance, resulting in weaker rotational moments ig. .. hese difculties are overcome by means of specically designed composite attachments, with properly oriented active surfaces, reconguring resultant force vectors with increased intervector distance see ig. . and resulting in stronger, more effective rotational moments. dditionally, the attachment structure blocks the slipping effect between aligner and tooth surface, allowing a fuller expression of desired tooth movement. nother effect observed in laboratory experimentation as well as in clinical practice is unintended intrusion

during rotational tooth movement. n another study using nite element analysis, researchers demonstrated that during aligner-based rotation of an upper canine without attachment, not only did the tooth lag behind the corresponding aligner stage almost by 3, but it also displayed clinically signicant intrusive forces that were found to be 3. times greater without than with attachments ig. .. he same numeric model, from an incisal perspective, revealed distinct pressure areas on the mesial and distal slopes of the incisal ridge ig. ., to which this undesirable effect can be attributed and corresponds to the normal components of the forces imparted by the aligner. ue to the orientation of With ATT Without ATT 30

Canine rotational lag (%)

25 20 15 10 5 0 0.25

1.25

A

2.25 Aligner rotation (°)

3.25

With ATT Without ATT

A 0.50 0.45 0.40

Fy (N)

0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 0

B

B Fig. 2.15 (A) otational forces produced by the aligner (purple arrows) are transmitted to the tooth as normal force components (red arrows), hich are perpendicular to tooth surface tangents (purple dotted lines). (B) ncorporation of bonded attachment increases the magnitude and efcacy of rotational moment by increasing the perpendicular distance (green dotted line) beteen the line of action (red dotted line) and the center of resistance (es)

0.5

1.0

1.5

2.0

2.5

3

3.5

Rotation (°)

Fig. 2.16 (A) ithout attachment, the tooth lagged behind the aligner almost by . ith attachment incorporation, this lag dropped to . (B) ntrusive forces observed at the periodontal ligament ithout attachments as .  for every degree of rotation, hile ith attachments the load as reduced to .  for every degree. ATT, Attachment. (Adapted from óme P, Peña M, alencia , et al. ffect of composite attachment on initial force system generated during canine rotation ith plastic aligners a three dimensional nite elements analysis. J Align Orthod. .)

4

2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics

21

Buccal Distal

Mesial

Mesial Distal

A

Lingual Fig. 2.18 Optimied otation Attachment (Align Technology, anta lara, A) ith active surface oriented to provide a compensatory etrusive force.

B Fig. 2.17 (A) igital image of occlusal vie of right upper canine. Occlusal vie of nite element method simulation of upper right ca nine during mesiolingual rotation. (B) istinctly intrusive pressure ar eas (red) on mesiolabial and distolingual aspects of the tooth cron appear upon aligner insertion. The dotted line represents the aligner’s prole. (Adapted from óme P, Peña M, alencia , et al. ffect of composite attachment on initial force system generated during canine rotation ith plastic aligners a three dimensional nite elements analysis. J Align Orthod. .)

A

the surface area, these forces are clearly intrusive. his undesirable intrusive effect can be reduced with appropriate attachment design, orienting the active surface at an angle in which the normal component of the force transmitted by the aligner will express an extrusive tendency ig. ..

SECONDORDER CONTROL ipping movements are easily achieved with bracket-based biomechanics ig. .. n the other hand, aligners lack control of mesiodistal root position due to the system’s inability to produce the reuired force couples, explaining why modication of anterior teeth angulation is so challenging. o improve second-order capabilities, aligner-based systems rely on specialized attachments that generate euivalent force couples see ig. ..

B Fig. 2.19 (A) orce couple produced during bracetbased correction of ecessive mesial tip. (B) uivalent force couple produced at Opti mied oot ontrol Attachments (Align Technology, anta lara, A) during alignerbased tipping.

22

Principles and Biomechanics of Aligner Treatment

Ai T uccessful closure of extraction spaces with aligners is also particularly difcult without excessive tipping in the direction of tooth movement. umeric models describing tooth displacement ig. . and periodontal ligament  strain ig. . patterns during distal tooth movement have shown that ptimized oot ontrol ttachments lign echnology, anta lara, , when bonded to upper cuspids, produce force systems capable of controlling undesired inclination during extraction space closure. Pi T n the posterior segment, tipping movements are not easily obtained with aligner-based mechanics without combining xed auxiliaries such as buccal tubes, power arms, etc., and these tooth movements, although possible, reuire sophisticated treatment planning, clinical expertise, and patient cooperation. dditionally, as with most complex force systems, specialized attachments must be designed to enhance the biomechanical capabilities of the aligner. he goal of this conguration of composite attachments is to produce a force couple and its corresponding moment that will incline the tooth in the desired direction ig. .. lternatively, the rectangular, horizontal attachment can be replaced with two shorter attachments, with variable distance separating them according to the clinician’s plan see ig. .. t is important to remember that the magnitude of the moment will depend on the amount of activation and corresponding mismatch prescribed in the digital treatment plan. n the other hand, the magnitude of the individual force vectors acting at the

A

B

Fig. 2.21 Periodontal ligament strain patterns during alignerbased distaliation of upper right canine. (A) ithout attachments, distocervi cal pressure (in blue) and distoapical tension (in red) areas ere observed, typical of uncontrolled distal tipping. (B) ith attachments, uniform pressure along the distal root surface (in blue) and uniform tension (in red) along the medial surface, typical of distal bodily move ment, ere observed. (Adapted from ome P, Peña M, Martíne , et al. nitial force systems during bodily tooth movement ith plastic aligners and composite attachments a threedimensional nite element analysis. Angle Orthod. .)

A

A

B

Fig. 2.2 Tooth displacement patterns during alignerbased distalia tion of upper right canine. (A) ithout attachments, distinct uncon trolled distal tipping as observed, ith center of rotation beteen apical and middle thirds of the root (red arrow). (B) ith attachments, the canine epressed distal bodily movement. (Adapted from ome P, Peña M, Mart√≠ne , et al. nitial force systems during bodily tooth movement ith plastic aligners and composite attachments a three dimensional nite element analysis. Angle Orthod. .)

B Fig. 2.22 (A) prighting moment produced at single rectangular hori ontal attachment. (B) Alternative tin attachment conguration.

2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics

23

B

A

Fig. 2.23 Producing euivalent moments (curved arrows), an increase in intervector distance proportionately reduces force magnitude (blue arrows) acting at attachment surface. To degrees of distal tipping ith a mm rectangular attachment (A) ill produce higher forces on the aligner than ith a toattachment conguration that signicantly separates the force vectors (B) of the acting couple.

aligner-attachment contact will depend on the distance between these two vectors. s the distance between the vectors decreases, the forces produced at the active surfaces of the attachments to produce an eual uprighting moment will increase ig. .3. his is an extremely important detail, considering aligner polymers’ high susceptibility to creep-related plastic deformation, which reuires the use of the lowest forces possible.

Dii M n effective strategy for controlling anchorage during extraction space closure is anterior and posterior moment to

A

force ratio manipulation in favor of the segment that reuires anchorage.3 s shown in ig. ., a reciprocal moment to force ratio between anterior alpha and posterior beta segments will result in group  space closure, in which both segments will meet at the middle of the extraction space resulting in class  malocclusion see ig. .. o obtain class  occlusion, posterior anchorage must be reinforced. onding rectangular horizontal attachments on the buccal surface of posterior teeth ig. . will result in clockwise moments that will resist mesialization of posterior teeth, resulting in group  space closure and the desired class  occlusal outcome see ig. ..

B Fig. 2.24 lass  case in hich reciprocal moments beteen anterior and posterior segments during etraction space closure (A) ill result in  anchorage loss and class  occlusion (B).

24

Principles and Biomechanics of Aligner Treatment

A

B Fig. 2.25 locise moments (blue curved arrows) produced by attachments bonded to posterior teeth (A) ill counteract posterior anchorage loss, reducing it to , resulting in class  occlusion (B).

TIRDORDER CONTROL Ai T orue modication of anterior teeth with conventional brackets is easily achieved by means of preactivation of the rectangular archwire, producing a complex, highforce couple when fully engaged in the rectangular slot ig. .. ccomplishing the same type of movement with plastic aligners demands an euivalent couple, derived from horizontal, parallel, and opposing forces applied on buccal and lingual surfaces see ig. .. ecause of the relatively ample distance between the couple vectors, force

A

magnitudes reuired for third-order control are signicantly lower than those reuired in euivalent bracketbased force systems.

Pi T orrection of transverse deciencies by expansion of the dental arch continues to be a challenging clinical obective with current aligner-based techniues. his has led to a widespread tendency of clinicians to overcorrect expansive movements in 3 treatment planning. he main reasons for lack of efcacy and predictability in the transverse plane are excess buccal tipping and insufcient force levels.

B

Fig. 2.26 (A) By preactivating (red shaded) and subseuently inserting (red) the archire, a force couple (blue arrows) and its corresponding counterclocise moment (blue curved arrow) ill be produced. (B) The same positive torue can be achieved ith aligners by producing an euivalent couple, ith loer forces and increased intervec tor distance.

2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics

Excess Buccal Tipping ecause forces act at a distance from the molar’s center of resistance ig. ., buccal tipping must always be expected when expansive forces are applied, especially when aligner-based forces are used. ith negligible friction and conseuent pervasive sliding effect between plastic and tooth crown, and relatively low stiffness as uncontrolled tipping occurs during expansion, the aligner will tend to are, losing control as dissociation between tooth and plastic occurs see ig. .. he use of attachments horizontal rectangular or occlusally beveled bonded to the buccal surface of posterior teeth helps improve third-order control by counteracting the undesired tipping moment as a result of a couple with opposite forces acting at the occlusal surface and at the gingival aspect of the attachment ig. ..

Lingual

Insufcient Force Levels ue to their horseshoe-shaped geometry, orthodontic aligners deliver expansive forces in a particular manner in which an anteroposterior decreasing force gradient will be observed ig. .. ecause of this distinct mode of force transmission, researchers have found that efcacy planned vs. nal increase in arch width of upper arch expansion dropped from  at rst premolars to  at the second molar.  ncreasing force levels during arch expansion by using thicker or lower elastic modulus polymers for aligner fabrication would improve this shortcoming, but not without the inconvenient increase in force levels of all other tooth movements programmed during the expansive stages. n alternative solution is the use of intermaxillary elastics, especially in cases with reduced anterior facial height, in which buccolingual tipping and

Buccal Lingual

Buccal

B

A

Fig. 2.27 (A) Alignerbased epansive force (red arrow) applied at a distance from the center of resistance (CRes) ill produce counterclocise moment (red curved arrow). (B) ithout preventive measures, buccal tipping ith center of rotation (CRot) above the furcation ill occur, folloed by aligner deformation and loss of control.

Lingual

A

Buccal

25

Lingual

Buccal

B

Fig. 2.28 (A) Opposing forces (blue arrows) acting at the occlusal surface and gingival aspect of a rectangular hori ontal buccal attachment ill provide a clocise moment (blue curved arrow) that reduces buccal tipping, ith apical migration of the center of rotation (CRot) (B).

26

Principles and Biomechanics of Aligner Treatment

A

B Fig. 2.29 (A) Programmed epansive mismatch beteen aligner and dental arch. (B) Once inserted, the resultant epansive forces ill have a distally decreasing magnitude gradient.

A

B

C

D Fig. 2.3 o angle patient (A), ith bilateral posterior crossbite (B, ) and midline discrepancy ().

extrusion of posterior segments are acceptable ig. .3. lastic forces originated from buttons bonded to palatal upper and buccal lower aspects of molars ig. .3 will produce a force vector with vertical and horizontal components of clinically relevant magnitudes that must be considered during treatment planning. n the example in ig. .3, a -gmf vector produced by a crossed intermaxillary elastic will be transmitted to the system as

 gmf of horizontal and  gmf of vertical force. s mentioned previously, horizontal rectangular attachments are effective in mitigating undesired tipping by counteracting excessive rotational moments ig. .33. y controlling vertical and transverse force levels, as well as desired and undesired tipping moments, predictable aligner-based treatment of different types of transverse discrepancies is possible ig. .3.

2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics

A

C

B

Fig. 2.31 (A) nitial linhec stage. (B) Aligners inserted, prior to bonding of upper palatal and loer buccal buttons. () rossbite elastic.

90 gmf 42 gmf 100 gmf

Fig. 2.32 A gmf intermaillary elastic force ill produce a gmf effective transverse force, epanding the upper arch and compressing the loer arch. Additionally,  gmf of etrusive force ill eually in§u ence upper and loer arches.

Fig. 2.33 n the upper arch, the moments provided by upper buccal attachments (blue curved arrows) ill counteract moments (red curved arrows) produced by elastic epansive forces (red arrows), reducing undesired upper tipping. n the loer arch, unopposed lingual elastic forces (dotted red arrows) ill result in epected lingual tipping (dotted red curved arrows)

27

28

Principles and Biomechanics of Aligner Treatment

A

B

D

C Fig. 2.34 (A, B) nitial bilateral crossbite and midline discrepancy. (, ) Alignerbased correction ith complemen tary use of intermaillary elastics.

References . Miller , uong , erakhshan M. ower incisor extraction treatment with the nvisalign system. J Clin Orthod. 3-. . arreda , zierewianko , Muñoz , et al. urface wear of resin composites used for nvisalign® attachments. Acta Odontol Latinoam. 3-. 3. Mantovani , astroorio , ossini , et al. canning electron microscopy analysis of aligner tting on anchorage attachments. J Orofac Orthop.  Mar-. . einberg , ouccar M, au , et al. ranslucency, stain resistance, and hardness of composites used for nvisalign attachments. J Clin Orthod. 3-. . ristizabal , arcía , eña M. aloracion del efecto biomecánico en el ligamento periodontal durante la expansión en el arco maxilar, de canino a molar, usando alineadores termo-formados con aditamentos biomecánicos complementarios, mediante métodos computacionales Mc thesis. ali, olombia niversidad del alle . ones M, Mah , ’oole . etention of thermoformed aligners with attachments of various shapes and positions. J Clin Orthod. 33-. . ombardo , Martines , Mazzanti , et al. tress relaxation properties of four orthodontic aligner materials a -hour in vitro study. Angle Orthod. -. . ang , hang , hen , et al. ynamic stress relaxation of orthodontic thermoplastic materials in a simulated oral environment. ent Mat . 33-. . lexandropoulos , l abbari , inelis , et al. hemical and mechanical characteristics of contemporary thermoplastic orthodontic materials. Aust Orthod J. 3-. . Moshiri , ra√∫o , Mcray , et al. ephalometric evaluation of adult anterior open bite non-extraction treatment with nvisalign. Dental Press J Orthod. 3-3.

. uarneri M, liverio , ilvestre , et al. pen bite treatment using clear aligners. Angle Orthod. 333-. . iancotti , arino , Mampieri . se of clear aligners in open bite cases an unexpected treatment option. J Orthod.  –. 3. au , einberg , hristou . ffectiveness of clear aligners in treating patients with anterior open bite a retrospective analysis. J Clin Orthod. -. . arnett , Mahood , guyen M, et al. ephalometric comparison of adult anterior open bite treatment using clear aligners and xed appliances. Angle Orthod.  an3-. . herwood , urch , hompson . losing anterior open bites by intruding molars with titanium miniplate anchorage. Am J Orthod Dentofacial Orthop. 3-. . roft . Contemporary Orthodontics. oronto lsevier 3. . oyd . omplex orthodontic treatment using a new protocol for the nvisalign appliance. J Clin Orthod. - uiz 3. . lein M.  cephalometric study of adult mild class  nonextraction treatment with the nvisalign system master’s thesis. aint ouis, M aint ouis niversity 3. . ossini , arrini , astroorio , et al. fcacy of clear aligners in controlling orthodontic tooth movement a systematic review. Angle Orthod. -. . lkholy , Mikhaiel , chmidt , et al. Mechanical load exerted by - aligners during mesial and distal derotation of a mandibular canine an in vitro study. J Orofac Orthop. 3-3. . ómez , eña M, alencia , et al. ffect of composite attachment on initial force system generated during canine rotation with plastic aligners a three dimensional nite elements analysis. J Align Orthod. 3-3. . omez , eña M, Martínez , et al. nitial force systems during bodily tooth movement with plastic aligners and composite

2 • urrent Biomechanical ationale oncerning omposite Attachments in Aligner Orthodontics

attachments a three-dimensional nite element analysis. Angle Orthod. 3-. 3. anda . Biomechanics and Esthetic Strategies in Clinical Orthodontics. t. ouis, M lsevier . . olano-Mendoza , onnemberg , olano-eina , et al. ow effective is the nvisalign® system in expansion movement with x3’ aligners Clin Oral Investig. -.

29

. oule , iedade , odescan r , et al. he predictability of transverse changes with nvisalign. Angle Orthod.  -. . hao , ang , ang M, et al. Maxillary expansion efciency with clear aligner and its possible inuencing factors. honghua ou iang i ue a hi. 3-.

3

Clear Aligners: Material Structures and Properties MASOUD AMIRKHANI, FAYEZ ELKHOLY, and BERND G. LAPATKI

Introduction The continued improement of medical treatment demands easy to use, cheaper, and more durable products without compromising the treatment outcome itself. ue to inherent properties and aailability, polymeric materials show high potential for medical applications. olymeric materials are lightweight, easy to manufacture, cheap, and ersatile. These properties allow them to be used in dierse medical applications such as implants, prostheses, and orthodontic appliances. s of any material used for medical applications and intraoral applications in particular, the polymer must be biocompatible and must not induce aderse reactions., The restrictions and the standard in choosing a polymer depend on the type of application. In orthodontic applications, polymers are exposed to the intraoral enironment, which comprises seeral different substances including water, electrolytes, enymes, bacteria, among other components. dditionally, consuming different food and drin changes the acidity and ion concentration and may temporarily introduce organic solent e.g., alcohol to the polymer enironment. This means that the polymer must be resistant to chemical corrosion. rincipally, corrosion causes a particle release, which—depending on the sie and form of particles—might inuence the mechanical properties of the polymer as well. nother important aspect is the thermal properties of the polymer. lthough the intraoral temperature remains relatiely constant near °, a polymer could be subected to arying temperature during intraoral application. This means that the intraoral temperature might change from a subero range e.g. while eating ice cream to alues as high as 6° e.g., while drining tea. uch temperature ariations lead to expansion or contraction of the material, which might hae an inuence on the interaction between the polymer and the teeth. Thus, a polymer must be able to tolerate temperature alteration without a pronounced olume and mechanical performance change. The mechanical stability of the polymer also plays an important role in orthodontic applications. or instance, a polymer used for aligners must withstand high occlusal forces otherwise, fractures or deformation might occur.  change in the mechanical properties of the polymer during the intraoral application period could also lead to unwanted changes of the mechanical loads applied to the teeth. en for a chemically stable material i.e., a material showing no corrosion, the mechanical properties of the polymer can still ary oer time due to aging and creep.5- 30

There are two types of aging: physical and chemical aging.5 6 Both chemical and physical aging render the polymer brittle and stiffer, thus a lower strain may be generated during the application. This chapter will focus on the basic properties of polymers typically used for aligners. It will also include an explanation of the chemical structure and thermal properties of these polymers. s the effectieness of a polymer for dental use depends on thermal, chemical, and mechanical stability, these issues also will be discussed briey. inally, future perspecties of polymers used for aligners are described.

Polymer Molecular Structure and Thermal Properties olymers are ery long and entangled molecules with nonconentional thermal and mechanical behaior. In this section, the structure of a polymer and its thermal behaior will be described. This comprises the specication of glass transition, aspects of aging, and the stability of the polymer in the intraoral milieu.

WHAT IS A POLYMER? The word polymer is deried originally from the ree words poly “many” and méros “units”. This indicates that polymers consist of many repeating units connected to each another through chemical bonding. ormally, if a substance contains ust a few molecules, an addition or remoal of only a few atoms would change the material properties signicantly. or example, if one would add ust  to heptane 6, then the boiling point of the resulting molecule  increases by °. ith polymers, in contrast, the number of repeating units could be changed by one or more units without any noticeable change in the polymer properties. Typically, a polymer chain is made of seeral thousand repeating units with a length of seeral micrometers and a diameter ust around  nm. The polymer chain is usually exible, twisted, and intertwined. The molecular weight and chemical structure of the polymer determine most of its properties. In contrast to small molecules haing a specic sie and molecular weight expressed in gmol or gmol, a polymer bul contains polymer chains with many different sies and molecular weights. ence the molecular weight of the polymer reects an aerage of many different polymer chains.

3 • Clear Aligners: Material Structures and Properties

31

O C

C

O

CH2

CH2

O

O

n

Fig. 3.1 Chemical structure of polyethylene terephthalate glycol material (PET).

H

O C

N

O

C

N

H

H

C

O

H

H

C

C

O

HH H

n

Fig. 3.2 Chemical structure of polyurethane material (PU).

GLASS TRANSITION-THE MACROMOLECULAR BASIS OF VISCOELASTICITY epending on the temperature, most materials exist in a solid, liuid, or gas state. ach of these states could be precisely described by thermodynamics laws. oweer, the inestigation of polymers reealed that most of them do not follow these basic material states. Instead, they show uid or solidlie, time-dependent characteristics.

ore specically, if a polymer is obsered in a short time scale, it behaes lie a solid material. If the experiment, howeer, is performed during a longer time period, polymers may ow and show a liuidlie behaior. This phenomenon is to be exemplied on the basis of the behaior of a simple liuid ethanol, which normally crystallies. et us assume that the liuid is cooled below its melting point. ig. . illustrates the change of the specic olume of the material ersus its temperature. The specic olume, dened as olume diided by mass, is the reerse of the density. uring cooling, the specic olume of the liuid decreases continually as long as it is still in the liuid phase. There exists, howeer, a point the freeing point at which the specic olume will decrease drastically and form a crystalline solid. uch olume discontinuity is related to the reduction of specic olume due to the crystalliation. Below the freeing point, the specic olume remains almost constant een though the cooling process is continued. The freeing or melting point is a material property and does not depend on the cooling rate or method of the measurement. It also has a clear thermodynamic denition without any room for interpretation. nder certain conditions, small molecules and many types of polymers, howeer, do not follow the mentioned

Liq Specific volume

Based on their thermal behaior, the three different classes of polymers are thermoplastic, elastomer, and thermoset. lear aligners belong to the thermoplastic group. Thermoplastic polymers melt and flow upon heating aboe a certain temperature. Two widely used polymers for aligners are polyethylene terephthalate glycol T- and thermoplastic polyurethane T.- The latter is a special thermoplastic form of polyurethane which melts by heating, facilitating the thermoforming process. Both of these thermoplastic materials are transparent in the isible light spectrum, are impact-resistant, and highly ductile. ust these properties in particular mae them ery suitable for use as aligner material. T- is a copolymer that constitutes two repeating units ig. .: polyethylene terephthalate and glycol. The addition of glycol preents the crystalliation of the T upon heating. This maes T- less brittle and more resistant to mechanical stress. T- is a ersatile polymer used in many other applications such as protectie coer e.g., smart card, electronic deices, food containers, and medical instruments. ne can thermoform, print, drill, bend, polish, and cut T- easily without noticeable impact on its stability and physical properties. s T- can be easily thermoformed and also recycled, it is also the material of choice for three-dimensional printing. The building bloc of polyurethane is urethane ig. ..  is aailable in both soft and rigid form, maing it ideal for automotie interiors, pacaging, coating, exible foam, and construction.  is impact resistant, is a good electrical isolator, bonds well with other material, and is chemically stable in the presence of water and oil. The ersatility of  is due to the fact that one can lin urethane molecules using different chemicals in ery different structures. This allows tailoring the hardness of  to the specic application. In general,  is biocompatible, but to mae it applicable as aligners,  is usually combined with other material.

p Su

erc

oo

-l led

iqu

uid

id

Amorphous Crystalline

Temperature

Tg

Tm

Fig. 3.3 Specic olume ersus temperature. Tm represents the melting temperature and Tg the glass transition temperature.

32

Principles and iomechanics of Aligner Treatment 0.34 0.33 0.32

Heat flow/mass (m/m)

0.31 0.30 0.29 0.28 0.27 0.26 0.25 0.24 0.23 0.22 45

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105

110

Temperature (°C) Fig. 3.4 ifferential scanning calorimetry of polyethylene terephthalate glycol (PET).

scenario but demonstrate another behaior. This is een applicable to simple liuids such as ethanol small molecules. If a ery pure ethanol is stored in a bowl with no corner and in a refrigerator without ibration, it can be cooled to below freeing temperature without freeing. ence there exists a temperature range below the melting point called the supercooled region in which the substance remains liuid. If the cooling process is continued, a temperature range will be reached at which the supercooled liuid transforms into a glassy state called the glass transition temperature Tg. In this solidlie form, the substance has ery different properties than the crystalline state. lassy material is an amorphous material, which does not hae a long-range order. The structure of material in the glassy form is therefore more similar to a liuid than to a crystalline structure. xcept for only a few examples, solid polymeric materials mainly exist in such an amorphous state. This is primarily related to the fact that the polymer’s long chain is entangled with other chains. ence it is usually difcult for the polymer chains to orientate and build an ordered crystalline structure. It has to be noted that simple polymers may actually show crystalliation if the cooling rate is low enough so that the polymer chains are allowed to nd their minimum state of energy i.e., their euilibrium. oweer, for many polymers with entangled chains, moements of polymer chains are hindered too much, maing it physically impossible to reach the crystalline state. The usual state of polymers is, conseuently, solidlie with an amorphous structure. eertheless, the polymer chains retain their tendency to orient and to achiee an euilibrium state. This tendency is the source of the specic behaior of amorphous polymers, which is plastic and elastic-lie, and might alter between these characteristics throughout time.

These aspects explain why the glass transition temperature plays an important role in dening a polymer’s properties, though it must be mentioned that the glass transition temperature is an ill-dened transition. The latter means that different measurement techniues may lead to different Tg alues. ifferential scanning calorimetry  is a widely accepted techniue for determination of the Tg alue. ig. . shows results of  measurements for T-. sually the middle of this range i.e., 5° for T- is taen as the determined Tg alue. rom an application-oriented iew, any thermoforming must occur aboe the Tg temperature. The exemplied  cure further indicates that, if T- is heated aboe 6°, its mechanical properties will change drastically. ore specically, around a temperature of 6°, T- will start to get softer and deform easier. Intraorally, this temperature is usually not exceeded for a sufciently long time, so T- stays mechanically stable during dental applications.

Physical and Chemical Aging of Aligner Polymers In the fabrication process, aligners go through thermoforming. uring subseuent clinical application, they are in contact with salia, food, drins, among other chemicals. onseuently, as the orthodontist reuires a reliable appliance, sufcient material stability is needed under arying conditions. The stability of the aligner is measured by its aging i.e., the change of its properties oer time. olymer aging has seeral sources. ith respect to intraoral application of polymers, two aspects of aging should be considered in particular: physical and chemical aging.5 6

3 • Clear Aligners: Material Structures and Properties

PHYSICAL AGING OF POLYMERS hysical aging of polymers principally occurs, as mentioned earlier, in an amorphous i.e., noneuilibrium form. ery system with the noneuilibrium state tends to decrease its energy to thus approach its euilibrium state. If enough mobility is obtained, the chains may rearrange themseles to their lowest energy state, which might be compared to crystalliation. This in turn will lead to a decrease of the specic olume, a decrease of the enthalpy, an increase of the hardness and brittleness, and changes to other properties.5 This effect particularly changes the mechanical properties of the polymer. ccordingly, physical aging can be dened as the relaxation of a polymer toward a more stable energy state. If the usage of a polymer occurs far below its Tg temperature, the polymer chains will not hae enough inetic energy to moe and rearrange. ence, by choosing an aligner with a Tg alue much higher than the intraoral temperature, physical aging might be largely aoided. It is important to note in this context that a polymer’s Tg alue may also change due to enironmental inuences. hysical aging of polymers can be inuenced by exposure to water and many other inds of molecules in the intraoral medium. s mentioned, the specic olume of an amorphous polymer is high in comparison to a crystalline polymer. This means there exists a lot of free olume in the amorphous polymer below the Tg temperature. onseuently, for prolonged exposure of such a polymer to water, water molecules could diffuse into the material alongside other molecules. The latter is one of the reasons for discoloration of aligners. It is important to note that the absorption of these molecules may also change the properties of the polymer.  typical change is called the plasticiing effect.6 To explain further, consider using spaghetti as an example. roided that a bowl contains spaghetti without sauce, the noodles cannot moe as easily because they stic together. oweer, by adding a sauce to the bowl, the spaghetti noodles separate, which enables them to slip along each other. In polymers, the plasticiing effect follows almost the same logic: the small, embedded molecules are placed between the polymer chains to increase the mobility of the chains. The plasticiing effect will reduce the glass transition, and therefore the polymer will be more affected by physical aging. rom a clinical perspectie, physical aging can affect an aligner in two ways. Initially, the polymer will become softer due to the plasticiing effect. s a result, force magnitudes applied to the indiidual teeth are reduced. In the long run, howeer, due to the effect of classical physical aging, aligner polymers become harder which will increase the applied forces and more brittle increasing the ris of breaage.

CHEMICAL AGING OF POLYMERS s introduced, aligners may also suffer from chemical aging, which is the result of a chemical interaction between a polymer and its medium. t present, none of the aailable aligner materials is inert, which means that these materials do react with certain chemicals included in salia, drin, or food. hemical aging can affect a polymer ia different mechanisms. or example, water molecules can brea the

33

polymer chains and shorten them hydrolysis, or a similar reaction can occur due to the interaction between the oxygen and polymer oxidation.  polymer suffering from chemical aging is more liely to deelop cracs and induce notch effects. ote, too, the time dependency of the mechanical properties of an aligner might be related to creep which will be explained in the next chapter. reep is different from aging phenomenon. It occurs due to application of mechanical stress to the material, whereas aging is the result of a polymer’s noneuilibrium state or medium, which occurs without any external stress application. Both phenomena are similar to each other, but they are related to uite different mechanisms and should therefore not be confused.

Conclusions and Outlook The two aligner materials mainly used i.e., T and T- hae a distinct chemical structure leading to different responses to thermoforming, exposure to the intraoral milieu, and mechanical stress. ence it is of great importance not to generalie the characteristics determined for one aligner material een one brand. ethodologic conditions for material tests must be as realistic as possible. or example, the mechanical properties of aligner materials differ greatly before and after thermoforming. Thus a realistic test should include the thermoformed material specimen or aligners. urthermore, stress measurements should be performed in a simulated intraoral medium. lso, the production process the method of molding, cooling, etc. affects polymer structure, which in turn might alter the performance of aligner materials. To obtain alid comparisons between tested materials and to achiee reliable treatment results, test procedures and clinical application protocols should be standardied. nly then will the full potential of clear aligners be reealed. ligner manufacturers or dental suppliers should inform users i.e., orthodontists about any changes in the chemical composition and production process. eertheless, it is often rather difcult to obtain such information.

References . illiams . n the mechanisms of biocompatibility. Biomaterials. :-5. . ires , erreira , odrigues , et al. eural stem cell differentiation by electrical stimulation using a cross-lined T substrate: expanding the use of biocompatible conugated conductie polymers for neural tissue engineering. Biochim Biophys Acta. 55:5–6. . umphrey , illiamson T.  reiew of salia: normal composition, ow, and function. J Prosthet Dent. 5:6–6. . idaa , Iwasai , aito , et al. Inuence of clenching intensity on bite force balance, occlusal contact area, and aerage bite pressure. J Dent Res. :6-. 5. odge I. hysical aging in polymer glasses. Science. 56: 5–. 6. rissman , cenna B. hysical and chemical aging in  and their effects on creep and creep rupture behaior. J Polym Sci B Polym Phys. :6-. . iggleman , chweier , ablo d. onlinear creep in a polymer glass. Macromolecules. :6-6. . Bower I. An Introduction to Polymer Physics. ambridge: ambridge niersity ress .

34

Principles and iomechanics of Aligner Treatment

. ombardo , artines , aanti , et al. tress relaxation properties of four orthodontic aligner materials: a -hour in itro study. Angle Orthod. :-. . ancini , arinci , ollino I, et al. implicity and reliability of Inisalign® system. ur J Inamm. :-5. . lexandropoulos , l abbari , inelis , et al. hemical and mechanical characteristics of contemporary thermoplastic orthodontic materials. Aust Orthod J. 5:65-. . lesandro , aurin .  study of polymers. I. ighly elastic deformation of polymers. Ruer hem Technol. :6-.

. edde . Polymer Physics. ordrecht: pringer etherlands . . oi , dwards . The Theory o Polymer Dynamics. xford: larendon ress 6. 5. trui . Physical Aging in Amorphous Polymers and Other Materials. lseier cience . 6. mirhani , orini , eporini . econd harmonic generation studies of intrinsic and extrinsic relaxation dynamics in polymethy methacrylate. J on ryst Solids. 55: -.

4

Inuence of Intraoral Factors on Optical and Mechanical Aligner Material Properties FAYEZ ELKHOLY, SILVA SCHMIDT, MASOUD AMIRKHANI, and BERND G. LAPATKI

Introduction

Water Absorption

he triad of success of orthodontic therapy comprises patient compliance, biomechanical nowledge, and, for the therapy with aligners, sufcient understanding of the thermoplastic material used. hapter  addressed the basic chemical and mechanical properties of commonly used aligner materials. his chapter will focus on the inuence of different intraoral factors on the mechanical and optical properties of aligner materials. o achieve an efcient orthodontic tooth movement, single aligners are usually worn for a period of  to  days and approimately  hours per day. uring their period of use, aligners are subjected to a prolonged eposure to different factors that are inuencing their properties. hey can be subdivided into two main categories. n the one hand, there are factors inducing optical material changes, either in the form of discoloration or increased opacity such effects are related to the presence of salivary enymes, plaue, and food and beverage coloring.- n the other hand, there are factors affecting the mechanical properties of aligners, including the periodic loading and unloading of the material during its clinical handling, combined with uneven local stress and strain distribution. t must be noted, too, that ecessive occlusal forces e.g., during involuntary clenching or grinding and intraoral temperature uctuations may inuence an aligner’s properties., As this appliance, however, is to be removed during food or liuid intae and worn for only a relatively short period, the clinical relevance of the latter two factors may not be overemphasied. he following sections will discuss the mechanisms of how intraoral factors influence optical and mechanical aligner properties and describe the clinical implications. articular attention will be given to describing the material-specific characteristics of the two aligner materials mainly used i.e., thermoplastic polyurethane  and polyethylene terephthalate glycol -.  is used, for instance, in the nvisalign system Align echnology, anta lara, A, nited tates or  Aligner weden  artina, ue arrare, adova, taly, whereas - is used in the lear Aligner system uran, cheu ental mbH, serlohn, ermany and the ssi system ssi A1, entsply aintree ssi, arasota, , nited tates.

Aligners are constantly subjected to saliva, which consists of 99% water. Hence it is crucial to understand the mechanism and effects of water absorption as well as the inuence of water absorption on the mechanical material properties. As stated in hapter , amorphous polymers such as  and - possess relatively low molecular density, which provides free volume for water intae. A previous study comparing these two materials showed that  shows higher water absorption characteried by a weight increase of .% after a -wee water storage than - showing only a .% increase.9 esides this weight effect, penetration of thermoplastic materials by water molecules also leads to modication of their internal structure. As eplained in hapter , this will result in plasticiation because lins between polymer chains are weaened or even destroyed, which reduces the internal cohesion and increases the molecular mobility. he resulting loss of elasticity might eplain the appearance of internal cracs observed in aligners after clinical usage. t is interesting to note in this contet that own studies on - material characteristics using three-point bending of thermoformed rectangular specimens revealed that the sole water storage without subjecting the material to any mechanical loads has only a minor impact on the mechanical material characteristics ig. .. n contrast, if - is subjected to both water and a continuous mechanical load, the effect on the mechanical properties is much more pronounced, as indicated by the reduction of the bending forces of up to % see ig. .. rincipally, water absorption could also induce dimensional changes of the aligners, nown as hygroscopic epansion. n theory, this factor—besides other factors such as the initial play between the aligner and the setup model-—might affect the t of the aligners and, conseuently, might also induce an alteration of the forces applied to the individual teeth.9  A previous study on water adsorption of thermoplastic materials, however, did not nd signicant and plausible correlations between the rate of water absorption and the amount of hygroscopic epansion.9 or instance,  showed a lower hygroscopic epansion, although it showed the highest water absorption rates. 35

36

Principles and Biomechanics of Aligner Treatment

Bending forces for PETG specimens

Force (N)

8 7 6 5 4 3 2 1  Dry (unloaded)

24 h loaded under dry conditions 24 h loaded + immersed in water

24 h immersed in water (unloaded)

Fig. 4.1 Bending forces depending on the (dry or wet) storage conditions and the unloaded or loaded condition. Note 0.75mm polyethylene terephthalate glycol (PET-G) specimens were inestigated in a threepoint ending set ting with a span length of  mm at a deection of 0. mm. The specimens were either only thermoformed and then underwent only one short deection with simultaneous force stored for  hours in water without loading loaded continuously for  hours without water immersion or loaded continuously for  hours with water immersion. The error ars represent the standard deiation for the different measurements.

Optical Changes ne of the main reasons for the popularity of aligners with patients lies in the invisibility or better the transparency of this appliance.- hese characteristics should be maintained throughout the treatment period because a discolored or opaue aligner ig. . might jeopardie the patient’s motivation and compliance. Aligner discoloration is primarily related to supercial absorption or penetration of pigmentations in food and beverages. offee i.e., the highest chromogenic agent, blac tea, and red wine play a prominent role.   t is noticeable in this contet that the rate and etent of discoloration is material-specic. t seems that -based aligners might ehibit faster discoloration rates than - aligners. A possible eplanation for this difference is the higher water absorption capability of  facilitating the accumulation of the pigments.9 n addition, the higher surface roughness of  might also facilitate the adhesion of pigments on the polymer lm’s surface. Aligners might also lose translucency by the development of internal microcracs, formation of calcic

A

integuments, or the accumulation of plaue on the aligner surface.-,9 bviously, the two latter changes do not have a signicant impact on the treatment success due to the short application period of each single aligner of maimally  wees. oreover, the loss of translucency can be minimied by maintaining good aligner hygiene through regular brushing with neutral soap and the use of denturecleaning effervescent tablets containing sodium bicarbonate or sodium sulfate.

Short-Term Mechanical Loading of Aligner Materials SINGLE SHORT-TERM LOADINGS or viscoelastic materials, it is nown that during very short loading periods the elastic component dominates. his thesis was also conrmed by unpublished investigation of - specimens by our group, consisting of two short loadingmeasuring cycles with a duration of only ca. . second each and a -minute brea in between. he comparison of the

B Fig. 4.2 nisalign aligners. (A) Prior to rst intraoral application. (B) After a wee wearing period.

4 • nuence of ntraoral actors on ptical and echanical Aligner aterial Properties

Force measured at short-term deflection 8 7

Force (N)

6 5 4 3 2 1 0 First loading

Second loading

Fig. 4.3 orces measured for 0.75mm polyethylene terephthalate glycol (PT) specimens in a threepoint ending setup with a span length of  mm. The central support was deected y 0. mm. Two short loadingmeasuring cycles with 0.second duration separated y a minute recoery rea were performed.

forces obtained by the rst and second measurements did not show a signicant difference ig. ..

MULTIPLE SHORT-TERM LOADING CYCLES uring clinical application, aligners are removed multiple times for food and liuid intae as well as during the regular oral hygiene procedures. o simulate or eemplify such scenarios, our group conducted an in vitro study, including cyclic loading of .-mm-thic  specimens using a three-point bending setup. ach of the  cycles consisted of a -minute loading interval, followed by a nearly unloaded interval of  minutes during which the deection was reduced to a level at which the remaining force was just above   to maintain contact between the force-measuring device and the specimen. As revealed by ig. ., the - specimen showed a continuous stress relaation behavior during the -minute loading periods with a force reduction of ca. % average over the  loading-unloading cycles. t was also observed that during the -minute uasi unloaded period, a slight average increase of the deection forces by ca. .% occurred. uch force increase indicates a slight recovery of the - material see ig. .. n some studies, such recovery is described as “relaation” the latter epression, however, should not be mistaen for “stress relaation,” which describes a completely opposite phenomenon. t is noteworthy that a similar material behavior was found in another in vitro study in which --aligners were repeatedly removed from a test model. his previous study observed a clear decrease of aligner force delivery in the course of the  aligner seating-removal procedures. oreover, the force reduction showed a nearly linear relation with the freuency of the cycles, with force values dropping down to % of the initial forces after  cycles ig. .. urther wor is reuired to systematically eamine this aspect for other materials than -.

37

OCCLUSAL FORCES n addition to the specic loading of aligners related to repeated intraoral seating and removal, aligners are also potentially eposed to relatively high mechanical loads occurring during occlusal contacting. uch bite forces are particularly relevant in patients showing clenching or grinding where they may reach force values up to   per single molar. Although  possesses higher abrasion resistance than -, available studies indicate that both materials showed delamination and abrasion as well as an increased icers hardness, particularly in the posterior region of the dental arch.,,,9,, he latter was observed after a -wee wear period and was traced bac to the changes in the crystalline structure of the polymer under cold wor. evertheless, the clinical impact of these changes appears unproblematic for two reasons irst, those teeth mainly affected by the altered material behavior i.e., the buccal teeth are moved to a minor etent during aligner therapy second, the wearing period of an aligner ranging between  and  wees seems too short for the mechanical destruction of an aligner by contact forces.

Long-Term Loading Aligner materials such as  and - show a viscoelastic behavior. Hence they show both elastic and viscous characteristics when undergoing loading, resulting in a time-dependent deformation. uring very short loading periods, the elastic component dominates. he timedependent viscous component, in contrast, reveals primarily during prolonged loading. he viscoelastic behavior can be mathematically described as standard linear solid models ig. .. uch models consist of springs and dashpots representing the elastic and viscous material components, respectively. perimental description of the mechanical behavior of a viscoelastic material is possible by two variables creep or stress relaation. t is important to clarify the difference between these two parameters ig. .. reep describes the phenomenon of increasing mechanical strain over time in case of a constantly applied stress or force, respectively. ince the mechanical load stress is maintained at a constant level, creep eperiments induce a continuous deformation strain see ig. .A until a maimum strain is reached. tress relaation, in contrast, describes the gradual stress decrease over time under a constant strain and deformation, respectively see ig. .. As a result, the force level drops continually until a certain euilibrium state is reached at a reduced stress level.  o ensure a better understanding of the viscoelastic properties of polymers, it is important to consider the specic test method applied. reep is usually eamined either by tensile measurements or by instrumental indentation tests.   ensile measurements are usually performed by loading the specimens at a certain force level, which is then maintained for a certain period. he rate of elongation of the specimen describes the creep rate of the tested material. nstrumental indentation is more common and usually uantitatively evaluated by calculating the percentage difference between

Principles and Biomechanics of Aligner Treatment

Short-term repeated loading 7 B 6

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Fig. 4.4 (A) orces measured during multiple 5minute loading and 5minute loading cycles for a 0.5mm polyeth ylene terephthalate glycol (PT) specimen in a threepoint ending setup with a span length of  mm and a deec tion of 0. mm. (B) nlargement of a data segment (see top of A) showing the gradual force decrease during the 5minute loading time. () nlargement of a data segment (see bottom of A) showing the slight force increase during the 0minute minimal load time at the corresponding deections.

Change in the mean force for different aligner removal frequencies 18 16 Mean force in (n)

38

14 12 10 8 6 4 2 0

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Fig. 4.5 Aerage force reduction reported for polyethylene terephthalate glycol (PT) aligners in the course of 50 aligner seatingremoal procedures ased on the data pulished y ai et al. 0 The error ars indicate the standard deiation.

65

4 • nuence of ntraoral actors on ptical and echanical Aligner aterial Properties

A

3

B

Fig. 4.6 chematic modeling of iscoelastic material ehaior using a standard linear solid model. (A) awell representation of a standard linear solid model. (B) elin representation of a standard linear solid model. uch models comine springs and dashpots in a certain arrangement to descrie the oerall ehaior of a system under different loading conditions. prings represent the elastic component of a iscoelastic material whereas dashpots represent the iscous component.0 ue to comination of such elements an applied stress aries with the time dependent change of the strain.

Stress relaxation

Creep

Stress

Strain

Stress-strain

Stress-strain

Strain

Stress

A

Time

B

Time

Fig. 4.7 Two fundamentally different eperiments and parameters respectiely descriing the timedependent ehaior of a iscoelastic aligner material. (A) The creep phenomenon is osered if the load (and stress leel respectiely) is ept constant oer time. (B) The stress relaation ehaior is characteried y loading the material under constant strain and deection respectiely.

the initial and nal indentation depth during the constant force application period. Hence it is determined how deep the material has been penetrated over the designated period. tress relaation, on the other hand, can be tested either by three-point bending or in tensile eperimental setups.,9 A common feature of both setups is the constant deection strain of the specimen for a dened period during which the time-dependency of the stress is registered. he difference between the initial and residual values over time denes the stress relaation rate. Aligner materials with lower creep resistance tend to a faster strain deformation under constant mechanical stress. hen transferred to the clinical situation, such behavior would reduce the mechanical load applied to the

teeth because the relative discrepancy between the actual tooth position and its position in the aligner would diminish. A previous study investigated the creep behavior of the different thermoplastic raw lms used in the nvisalign Align echnology, anta lara, A, A, lear Aligner cheu ental mbH, serlohn, ermany, and ssi A1 entsply aintree ssi, arasota, , A systems by means of indentation creep eperiments. he indentation creep behavior was characteried by the percentage increase of the indentation depth within an interval of  minutes in with the specimens were subjected to a constant indentation force., esults of this study revealed more pronounced creep for modied , which is the material of nvisalign aligners .% compared to

Principles and Biomechanics of Aligner Treatment

the corresponding percentage for - .%. Another study observed that the creep of  was even more pronounced after aging, with an increased indentation depth of %. revious research determining the stress relaation behavior of commercial aligner materials revealed that most materials show a relatively high stress relaation rate in the rst  hours of loading, followed by a nearly steady plateau.  he stated stress decay, however, showed a material-dependent pattern with the highest stress relaation for - with % of the initial stress values, followed by the stress relaation of  with .%. After the -hour loading period, a similar material-dependent pattern was observed with residual stresses of .% and % of the initial values for the  and the - materials, respectively. imilar stress relaation patterns were found by our group investigating - specimens lear Aligner, cheu ental mbH, serlohn, ermany during a -wee constant deection period with water immersion of the specimens. ur results also indicated relatively rapid stress relaation during the rst day, followed by a slower stress reduction. At the end of the longer -wee loading period, stress values approimated a residual stress value of only % of the initial stress ig. ..

Clinical Loading atterns of Aligner Materials As mentioned, aligner materials possess elastic elements, which are of utmost importance for maintaining a certain force level on the teeth. f their load-deection behavior would be purely elastic, and the strain would be ept within the elastic range, then the force and moment components applied to the teeth would be directly proportional to the discrepancy between the actual tooth position and the programmed tooth position in the aligner. urthermore, the stiffness of the aligner material would describe the slope of this interrelation. As pointed out earlier, in case the load is maintained for a longer time, these materials also show a

Stress relaxation for Duran® PET-G specimens over a 7-day period 100% Nomralized stress relaxation (%)

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viscous behavior that can be uantied, for instance, by stress relaation eperiments. t is important to note that both the amount and the rate of deformation of thermoplastic materials depend on the loading time scheme and the stress magnitude, and both are affected by collateral factors such as the temperature and material-specic water absorption properties. Another important characteristic of thermoplastic aligner materials is observed in cases where the load is removed. nder this condition, thermoplastic materials may show a certain rebound effect. bviously such a phenomenon might be of practical importance as during clinical therapy, aligners are usually removed periodically e.g., for food intae. o investigate this characteristic, recent research in our lab aimed at the eamination of the inuence of repeated -hour loading-hour unloading cycles on the force application of - aligner materials over a total period of  wee. An eample of a measurement curve is presented in ig. .9. imilar to the eperiments with constant strain, the results indicated a relatively high force decay in the rst few hours to a level less than % of the initial

100%

20%

6

Fig. 4.8 Normalied stress relaation for polyethylene terephthalate glycol (PET-G) materials loaded for  wee in a threepoint ending setup with a constant deection of the specimen leading to a constant strain.

Stress relaxation of PET-G

40%

5

3 4  Measurement time (days)

6



Fig. 4. ecay of the forces measured after the loading and unloading periods during the wee oseration time.

4 • nuence of ntraoral actors on ptical and echanical Aligner aterial Properties

force indicating a clear stress relaation. After the -hour periods without loading, only slight force increases were observed. ven though after the second and following loading periods stress relaation could be observed, the latter was much less pronounced than that occurring in the rst loading period. ased on these ndings, we concluded that the stress relaation behavior of -, which is related to repeated loading and unloading intervals with similar lengths as those typically occurring during clinical therapy, tends to stabilie at a level between % and % of the initial stress.

. . . . .

References . oyd , iller , lasalic . he nvisalign system in adult orthodontics mild crowding and space closure cases. J Clin Orthod. -. . iu , un , iao , et al. olour stabilities of three types of orthodontic clear aligners eposed to staining agents. Int J Oral Sci. -. . afeiriadis AA, aramouos A, Athanasiou A, et al. n vitro spectrophotometric evaluation of ivera clear thermoplastic retainer discolouration. Aust Orthod J. 9-. . ernandes A, uellas A, Ara√∫jo A, et al. Assessment of eogenous pigmentation in colourless elastic ligatures. J Orthod. -. . evrini , ovara , argherini , et al. canning electron microscopy analysis of the growth of dental plaue on the surfaces of removable orthodontic aligners after the use of different cleaning methods. Clin Cosmet Investig Dent. -. . liades , ourauel . ntraoral aging of orthodontic materials the picture we miss and its clinical relevance. Am J Orthod Dentofacial Orthop. -. . chuster , liades , inelis , et al. tructural conformation and leaching from in vitro aged and retrieved nvisalign appliances. Am J Orthod Dentofacial Orthop. -. . Aleandropoulos A, Al abbari , inelis , et al. hemical and mechanical characteristics of contemporary thermoplastic orthodontic materials. Aust Orthod J. -. 9. yoawa H, iyaai , ujishima A, et al. he mechanical properties of dental thermoplastic materials in a simulated intraoral environment. Orthod Waves. -. . oubari A, lleuch , uermai , et al. nvestigations on hygrothermal aging of thermoplastic polyurethane material. Mater Des. 99-9. . lholy , anchaphongsapha , ilic , et al. orces and moments delivered by - aligners to an upper central incisor for labial and palatal translation. J Orofac Orthop. -. . lholy , chmidt , äger , et al. orces and moments applied during derotation of a maillary central incisor with thinner aligners

. 9. .

. . . . . . . . 9. .

41

an in-vitro study. Am J Orthod Dentofacial Orthop.  -. lholy , ihaiel , chmidt , et al. echanical load eerted by - aligners during mesial and distal derotation of a mandibular canine an in vitro study. J Orofac Orthop. -. hang , ai , ing , et al. reparation and characteriation of thermoplastic materials for invisible orthodontics. Dent Mater J. 9-99. eremiah H, ister , ewton . ocial perceptions of adults wearing orthodontic appliances a cross-sectional study. Eur J Orthod. -. osvall , ields H, iuchovsi , et al. Attractiveness, acceptability, and value of orthodontic appliances. Am J Orthod Dentofacial Orthop. 9, e- discussion -. halish , ooper-aa , vgi , et al. Adult patients’ adjustability to orthodontic appliances. art  a comparison between abial, ingual, and nvisalign™. Eur J Orthod. -. chott , ö . olor fading of the blue compliance indicator encapsulated in removable clear nvisalign een® aligners. Angle Orthod. -9. racco A, aoli A, avoni , et al. hort-term chemical and physical changes in invisalign appliances. Aust Orthod J. 9-. ai A, ei , Abusama , et al. ffects of time and clear aligner removal freuency on the force delivered by different polyethylene terephthalate glycol-modied materials determined with thin-lm pressure sensors. Am J Orthod Dentofacial Orthop. 99-. Hattori , atoh , unieda , et al. ite forces and their resultants during forceful intercuspal clenching in humans. J Biomech. 9-. ejaovic´ , isa , rane . Abrasion resistance of selected commercially available polymer materials. Finn J riol. -. oomali , uresha , ee H. echanical and three-body abrasive wear behaviour of A blends. Mat Sci Eng AStruct. 9-9. ust . ichtlineare FiniteElementeBerechnungen ontat, eometrie, aterial. nd ed. iesbaden ieweg1eubner erlag  pringer achmedien iesbaden mbH iesbaden . ombardo , artines , aanti , et al. tress relaation properties of four orthodontic aligner materials a -hour in vitro study. Angle Orthod. -. i , en , ang , et al. hanges in force associated with the amount of aligner activation and lingual bodily movement of the maillary central incisor. orean J Orthod. -. radley , ese , liades , et al. o the mechanical and chemical properties of nvisalign  appliances change after use A retrieval analysis. Eur J Orthod. -. ondo’ , aini , erroni , et al. echanical properties of “two generations” of teeth aligners change analysis during oral permanence. Dent Mater J. -. ang , hang , hen H, et al. ynamic stress relaation of orthodontic thermoplastic materials in a simulated oral environment. Dent Mater J. 9-9. oylance . Engineering iscoelasticit. ambridge, A assachusetts nstitute of echnology 9.

5

Theoretical and Practical Considerations in Planning an Orthodontic Treatment with Clear Aligners TOMMASO CASTROFLORIO, GABRIELE ROSSINI, and SIMONE PARRINI

Introduction After the Stone Age, the Iron Age, and the Bronze Age, are we switching to the Polymer Age? This question is legitimate when examining the increase of plastic materials produc tion during the last halfcentury In the last decades, plastics hae permeated industrial technology Plastic materials hae replaced many materials used in the past, and they hae made possile industrial and medical applications that would not hae een possile with older technologies The ey to the widespread dissemi nation of these materials is their incredile ersatility urthermore, we are liing in the personalized medicine era Personalized medicine represents the natural eolution of health care hen medicine is informed solely y clinical practice guidelines, the patient is not treated as an indiid ual ut as a memer of a group Personalized or precision medicine characterizes unique iologic characteristics of the indiidual to tailor diagnostics and therapeutics to a specic patient Personalized medicine uses additional in formation aout the indiidual deried from nowing the patient as a person rthodontists hae always een educated in collecting and analyzing patients’ indiidual characteristics to per form a diagnosis and dene a personalized treatment plan In this iew, orthodontics will e the pioneer in guiding dentistry into the personalized medicine process hat is still missing is the integration of iologic marers into the diagnostic process and treatment planning, ut researchers are going to ll the gap In the last century, orthodontics was mostly a matter of metals and predened prescriptions In the last decades, the introduction of clear aligners moed the attention toward thermoplastic materials and their possile applications and personalized prescriptions In clear aligner therapy AT, eery aligner is uilt for a specic stage of orthodontic tooth moement T of a specic patient Aligners are com fortale, less isile, and more aesthetically pleasant com pared with uccal xed appliances they can e remoed for eating and oral hygiene procedures, reducing the occur rence of emergencies espite those adantages maing clear aligner increasingly requested y patients in our eautyconscious society, there was always a great deate 42

inoling efcacy and efciency of this appliance in con trolling T or instance, questions hae een raised re garding the extent to which aligners can control extrusion, rotation, odily moement, and torque As stated y Proft in , effectieness, efciency, and predictaility are the three things orthodontists need to now aout the treatment they are proiding A recent reiew stated that AT can control complex moements as maxillary molars odily distalization and extraction spaces close and that the uccolingual inclination of inci sors is well controlled in mild to moderate malocclusions urthermore, in a recent research paper, rünheid et al analyzed the differences etween predicted and achieed tooth positions and found statistically signicant differ ences for all teeth except maxillary lateral incisors, ca nines, and rst premolars In general, anterior teeth were positioned more occlusally than predicted, rotation of rounded teeth was incomplete, and moement of posterior teeth in all dimensions was not fully achieed oweer, except for excessie posttreatment of uccal crown torque of maxillary second molars, these differences were not large enough to e clinically releant Therefore, with respect to what was possile a few years ago when the recommendation was to treat only simple malocclusions with aligners, the growing ase of common nowledge regarding the control of T made it possile to use this technique een in more complex cases with good results when compared to conentional xed orthodontics Those results were made possile thans to orthodontists who started to consider the irtual setup not only to isual ize moing teeth ut as an instrument to design the proper iomechanics, starting to transfer wellnown concepts in this eld As stated y Burstone during a JCO interiew The nice thing about scientic biomechanics is that it is not dependent on any given appliance or technique. No matter what appliance you use, it allows you to use it better with more predictable results. Today, we have much too much commercialism in orthodontics a healthy dose o science in understanding appliances and how they wor is a good antidote. t is interesting to note that many o the new appliances that are suggested are nothing more than reinventions o old appliances.

5 • Theoretical and Practical Considerations in Planning an Orthodontic Treatment with Clear Aligners

Theoretical and Practical Considerations in CAT Based on these assumptions and on clinical and laoratory research, the iomechanics of clear aligners could e de scried as a sequence of crown tipping and root uprighting The rst part of moement occurs in the occlusal part of the tooth ecause the aligner enelopes the entire tooth crown, while the interactions etween aligner and attachments de termine root moement Therefore, when designing a irtual treatment plan, we must always rememer which is the inter action surface etween the aligner and the tooth, which is the effect of the force application at the crown leel, and which is the anchorage unit required to aoid undesired moements The analysis of a irtual treatment plan using dedicated software should e ased on the following steps

43

egarding the nal position of upper maxillary molars, it is recommendale to refer to the position indicated y icetts in  in which the line connecting the distouc cal and the mesiolingual cusps of the upper rst molar is passing through the cusp of the opposite canine at the end of treatment This nal position is ased on precise anatomic landmars and can preent misunderstandings etween the prescriing clinician and the technician trans ferring the information in the irtual treatment plan urthermore, when dening the nal position, the clini cian should always consider the uccal and the frontal limits of the arches, considering one and periodontal sup port and the cephalometric information Those indications are ery important to aoid excessie expansion andor proclination moements that can result in seere periodontal iatrogenic effects 

 Analysis of the nal position  Analysis of the moements occurring at each stage for each tooth

ANALYSIS OF THE MOVEMENTS OCCURRING AT EACH STAGE FOR EACH TOOTH

ANALYSIS OF THE FINAL POSITION

 Aligner auxiliaries  Anchorage management and moement sequentialization  T staging

 

According to Sarer et al it may e inappropriate to place eeryone in the same esthetic framewor and een more prolematic to attempt this ased solely on hard tis sue relationships since the soft tissues often fail to respond predictaly to hard tissue changes eertheless, it is ac cepted that esthetic considerations are paramount in plan ning appropriate treatment ut that rigid rules cannot e applied to this process In iew of our inaility to apply rules dening optimal esthetics, the use of scientic methods to plan the most esthetic treatment may therefore e compli cated eertheless, it is clear that laypeople can identify arious factors affecting smile esthetics Thus clinicians can expect their patients to e more attentie to some dental esthetic factors than they are to others A recent reiew was conducted to dene the minimum leel of esthetic harmony that can e approed as pleasur ale y an external oserer The indications proided in ig  represent the threshold of acceptance of smile es thetics proided y laypeople that should e considered when analyzing the nal position of front teeth

The analysis of moements occurring in eery stage should consider three different aspects

Aligner Auxiliarie Since the introduction of orthodontic aligners in early s, seeral auxiliaries hae een adopted from manufac turing companies and from clinicians to preent anchorage loss and maximize treatment efciency The most commonly adopted auxiliaries could e classi ed as follows n n n n

Attachments and pressure areas Intraoral elastics Interproximal enamel reduction IP Temporary anchorage deices TAs

Attachments and Pressure Areas. sing aligners without attachments is something lie or thodontics ut not orthodontics Attachments are useful to guide teeth in a determined direction ut are also useful in proiding anchorage control depending on the type of

Fig  Thresholds of acceptance of smile esthetics from laypeople point of view.

44

Principles and Biomechanics of Aligner Treatment

planned orthodontic moement The use of attachments is crucial to achiee effectie treatments aera et al and arino et al demonstrated the importance of using at tachments to improe the root control of distalizing molars in class II treatments In an in itro study, Simon et al dem onstrated that load transfer from aligners to teeth without the use of attachment is possile only to a limited extent Attachments are diided into two categories  onentional attachments rectangular, eeled, or ellipsoid  ptimized attachments onentional attachments igs , , and  can e positioned y the clinician on eery tooth compatily with tooth dimension and can e oriented in any direction ectangular attachments are usually placed to increase anchorage in posterior teeth or to reinforce the retention of the aligner ptimized attachments ig  are positioned y tech nicians, and the orthodontist is not ale to modify their position, dimension, and orientation This ind of attach ment was introduced to generate a dedicated couple of force during rotations, especially in canines and premolars The “play” of aligners on teeth and attachments is an other ey factor in producing desired outcomes, which is strictly related to attachment application An in itro study y asy et al demonstrated that attachment shape affects retention ectangular attachments are more retentie

Fig 4 Rectangular attachments on posterior teeth in Align Technology ClinCheck software.

Fig  Optimied and conventional attachments in Align Technology ClinCheck software.

Fig 2 Rectangular attachments on posterior teeth in CA Digital software.

Fig 3 Rectangular attachments on anterior teeth in CA Digital software.

than ellipsoid ones Two in itro studies demonstrated that aligners produced y different companies Inisalign, Align Technology, San osé, A, SA A lear Aligner, Scheu ental, Iserlohn, ermany  Aligner, Sweden  ar tina, ue arrare, Italy showed excellent tting on teeth and attachments,  aligners seem to hae the est alues in terms of tting on attachments the alues range from  to  mm The Inisalign tting ranges from  to  mm The measured alues for A lear Aligner analy sis range from  to  mm asy et al demonstrated that edgeless aligners generated signicantly lower forces than those with a wider edge The increased force might e due to the enhanced stiffness caused y material shape onse quently, the enhanced stiffness may reduce the tting of the aligner on the attachments This could e the reason why A aligners showed the worst results in terms of tting oweer, despite the statistical signicance, measured dif ferences might not e clinically releant Therefore the play of aligners on teeth and attachments is minimal, resulting in a precise transfer of the mechanical properties of the thermoplastic material to teeth rom a iomechanical point of iew, only a few studies in existing literature hae analyzed the interaction etween aligners and attachments An efcient method for studying aligner mechanics is the nite element method  Ap plications of  on aligner studies will e presented in the next parts of this chapter xcept for the ooi et al study, reported  results will refer to the initial instance of

5 • Theoretical and Practical Considerations in Planning an Orthodontic Treatment with Clear Aligners

aligner wearing thus these results should e considered in terms of initial force systems and displacements, not taing into account such precise measurements of the amount of moement expressed y the aligner on teeth sing , omez et al inestigated a theoretical mm displacement of an isolated upper canine with and without a composite attachment The attachment considered for this analysis was inspired y the “optimized attachments” adopted y Align Technology to increase root control during distaliza tion The authors osered uncontrolled distal crown tipping without the attachment and a displacement similar to odily moement with the attachment Thus the authors highlighted the difculty to otain a controlled moement in AT using only aligners and suggested the use of composite attachments to increase root control The iomechanical explanation of attachments useful ness in controlling tooth moement could e related to the role of races in xed orthodontics hile in xed appliance orthodontics the moment is deeloped in the racet itself y the engagement of the wire, in AT it is deeloped y the interaction of aligner and auxiliaries The aligner with out attachments tends to moe away from the teeth in its gingial edge In such eentuality, all force is concentrated only in the occlusal part, and no couple of force could e generated hen recurring to attachments, the interaction etween the displacement applied to the aligner and the at tachment generates the adequate forces and moments to otain a more controlled moement ooi et al in  pulished a paper that demonstrated these concepts using  to compare upper incisor dia stema closure without attachments and with optimized ones As reported y authors, the initial displacement cor responded to uncontrolled crown tipping for oth the simu lations howeer, after hundreds of iterations that simu lated the one remodeling process, the simulation without attachments resulted in uncontrolled tipping, while odily moement was osered in the simulation with optimized attachments egarding pressure areas, the ind of moements in which they are adopted depends on the aligner manufacturer su ally, pressure areas are adopted to improe efciency in crown tipping, rotations, and root torquing Barone et al in their  study from  reported that pressure areas are

4

the most effectie auxiliaries in lower incisors tipping, een more than rectangular attachments A study y astro§orio et al regarding control of root moement demonstrated the efcacy of pressure areas to improe this type of moement The force couple gener ated y an aligner torquing a tooth consists of a force near the gingial margin and a resulting force produced y moement of the tooth against the opposite inner surface of the appliance near the incisal edge Since the gingial edge of the aligner is elastic, it is difcult to control the forces applied in this region without an altered geometry Intraoral Elastics. egarding intraoral elastics, three main ariales could in§uence the right choice for the planned treatment  orcelength  Application point  Application surface igs  through  refer to upper molar distalization, which will e thoroughly analyzed in the following chap ters, and present the effects of elastics on teeth and aligners while changing application point The same elastic  in,  oz was applied so that the forcelength ariale would not affect the analyzed ones The difference in aligner defor mation and teeth initial displacement during second upper molar distalization could e osered In the preiously cited study, omez et al osered an intrusie effect on the canine due to an unexpected defor mation of the aligner during distalization A loose tting etween aligner and tooth would achiee inadequate con tact with the gingial optimized attachment and thus fail to produce a correct couple of force This eentuality could e aoided y class II elastic that assists during distalization moement proiding anchorage with the sagittal compo nent of elastic force and preenting intrusion thans to its ertical component Interproximal Reduction. Since rst descried y Ballard in , IP has een a procedure dedicated to mildtomoderate crowning cases oweer, in the last years, the digitalization of treatment planning increased the adoption of this technique to otain

Fig  nitial tooth displacement of second molar distaliation with class  elastics applied directly on upper canine (sagittal view).

4

Principles and Biomechanics of Aligner Treatment

Fig  nitial tooth displacement of second molar distaliation with class  elastics applied directly on upper canine (occlusal view)

Fig  nitial tooth displacement of second molar distaliation with class  elastics applied on aligner at upper canine level (occlusal view).

Fig  nitial tooth displacement of second molar distaliation with class  elastics applied on aligner at upper canine level (sagittal view).

Fig  nitial aligner displacement of second molar distaliation with class  elastics applied directly on upper canine.

space during orthodontic treatment, also improing its ac curacy and precision uring AT digital planning, the IP amount is calculated ased on digitally performed dental index scores Bolton index, ittle index, space analysis, etc, and the timing of IP is programmed to otain the est in terproximal surface access and to aoid premature tooth surface collisions As demonstrated y seeral authors, IP is a safe procedure for tooth health, which does not increase

the riss of interproximal caities and tooth demineraliza tion, egarding IP maximum amount, in  Sarig et al analyzed  extracted intact anterior and posterior teeth from oth maxilla and mandile The authors re ported that the existing guidelines of mm max IP for each interproximal space could e conrmed for anterior region, while in the posterior region it could e increased to  mm

5 • Theoretical and Practical Considerations in Planning an Orthodontic Treatment with Clear Aligners

4

Fig  nitial aligner displacement of second molar distaliation with class  elastics applied on aligner at upper canine level.

Temporary Anchorage Devices. Aligner treatment with TAs is thoroughly analyzed in hapter 

Anrage Manageen an Meen Seuenialiain Anchorage management represents the ey for a successful orthodontic treatment In xed orthodontic treatment, auxiliaries such as laceacs, tieacs, and elastics are ad opted to reinforce anchorage when needed, principally dur ing the woring phase of treatment espite the widespread use of aligner orthodontics, no iomechanical studies are present to date to erify the efciency of aligners alone in maintaining anchorage In aligner orthodontics, as well as in conentional ortho dontics, anchorage loss could result in inefcacy of pro grammed moements or in undesired moements of anchor age unit A paper y ortona et al reported the effects of anchorage loss on a contralateral premolar during rotation of a lower premolar without attachments Anchorage in aligner orthodontics depends on two ey factors sequentialization of moements and aligner defor mation Sequentialization in aligner orthodontics is intended as the order in which teeth are moed during the treatment oement sequentialization allows a proper anchorage control, reducing the ris of undesired displacements ul tiple moements at the same time should e aoided unless we are referring to small amounts of moement on seeral teeth, as in such cases when we are aligning and leeling the arches in mild class I malocclusions, for example ul tiple complex moements as well as lingual root torque moement associated with rotation and extrusion or intru sion moements of an upper incisor, as an example, should e always aoided In cases when multiple moements hae een planned on a specic tooth, the est option is to split moements ased on their complexity Therefore, torque moement should e performed a second time, at least once rotational and tipping moements hae een completed ore detailed sequentialization protocols will e analyzed in dedicated chapters Among sequentialization resides also the concept of “differential forces and moments” This concept is the result of the iomechanical design of a force system, which y the way of its application can distriute the reciprocal forces and moments oer signi cantly different root areas with the oectie of eliciting a

differential response Seeral studies demonstrated the efciency of this method in presering anchorage and ante rior torque during space closure after a premolar extrac tion, In aligner orthodontics, these concepts hae een introduced y Align Technology with the socalled  pro tocol for rst premolar extraction ifferential moments are produced with a comination of optimized attachments and aligner actiation howeer, no detailed force systems are pulicly aailale and to date no trials hae een con ducted to measure the outcomes of this clinical protocol Aligner deformation is intended as the response of the whole aligner to the stress caused y tting it on teeth uring aligner wearing, a push and pull force system in oles not only the teeth for which moements are planned ut also adacent teeth and the aligner itself ig  shows the tooth displacement during upper second molar distalization in an efcient force conguration note that while  mm of moement was planned for tooth ,  mm is efciently applied on the tooth, while the other amount results in mesial displacement of the aligner An other example of anchorage loss due to aligner deforma tion is reported in ig , in which mesial displacement of molars is highlighted during sequential distalization of premolars irst and second molars, in this simulation, were set as an anchorage unit oweer, without proper auxiliaries to increase anchorage and manage aligner de formation, een a good moement sequentialization could e not adequate

OTM Saging In aligner orthodontics, staging is intended as the amount of programmed moement per tooth in each aligner Stag ing amount is determined y each aligner company ased on internal research, thus default staging settings may differ etween one another egarding scientic literature, ei denceased data aout staging are ery poor Simon et al, in their  in itro study, tested different amounts of stag ing for premolar rotation The accuracy for this moement was haled when a rotation greater than  degrees per aligner was planned , degrees  12  . degrees  12  The importance of staging for tooth rotation could e highlighted in the paper y ortona et al A simulation, including an ideal dental arch with element  rotated  degrees mesially, was tested with dif ferent staging and attachment congurations for premolar distal rotation Staging of  and  degrees of rotation per

4

Principles and Biomechanics of Aligner Treatment

Fig 2 nitial tooth displacement of second molar distaliation with class  elastics applied on aligner at rst premolar level. nitial displacement amount is shown in the attached legend.

Fig 3 nitial tooth displacement of rst molar and second premolar distaliation without class  elastics. The mesial shift of posterior teeth is clinically relevant.

aligner was compared and the difference in periodontal liga ment P pressure on tooth  etween the different amount of staging with rectangular attachments from tooth  to  was reported Planned rotation of  de grees produced  mmg of pressure on periodontal liga ment, while  degrees of planned rotation otained pressure of  mmg Thus the model with attachments from  to  and  degrees of actiation was the most reli ale and efcient conguration for lower premolar rotation idenceased data regarding staging for other moe ments may e deried from in itro and clinical studies, ut there is a lac of dedicated trials Tale  reports the sug gested amount of moement per aligner ased on scientic literature and clinical expertise of the authors

Table 5.1 uggested Amount of ovement per Aligner Rotation  

,.°

ntrusiontrusion

. mm

inear ovement   

. mm

Root Torue

  

°

Biologic Considerations in Aligner Orthodontics As stated at the eginning of this chapter, personalized medicine applied to orthodontics is ased not only on dedi cated mechanics ut also on the nowledge of each pa tient’s iology The application of an orthodontic force produces a tissue reaction resulting from the perturation generated y the orthodontic appliance and the modeling and remodeling of the aleolar one uncio et al suggested that teeth moed with aligners did not undergo the typical stages of moement, as descried y rishnan and aidoitch, e cause of the intermittent forces applied y the aligners oweer, light, continuous forces seem to e perceied as intermittent forces y the periodontium due to its iscoelas tic nature, and orthodontic intermittent forces can produce T with less cell damage in the periodontium astro§o rio et al, in analyzing the iologic response to the applica tion of aligners distalizing a maxillary molar in a single tooth moement design study, showed that the force deli ery produces an increased concentration of one modeling

5 • Theoretical and Practical Considerations in Planning an Orthodontic Treatment with Clear Aligners

and remodeling mediators at oth pressure sites interleu in  eta Ib, receptor actiator of nuclear factor appaB ligand A and tension sites transforming growth factor eta Tb, osteopontin P In other words, aligners seem to e capale of inducing the same iologic responses descried for other appliances at least in the ery early stages of orthodontic treatment

Patient Compliance espite all iologic and iomechanical aspects, the success of an orthodontic treatment strictly depends on patient compliance ompliance with remoale orthodontic align ers is fundamental for the efciency and success of AT in the short and long term A  systematic reiew uilt on preious primary re search conrmed suoptimal leels of compliance with a ariety of remoale orthodontic aduncts, alluding to ac tual wear durations of  hours per day less than recom mended The in§uence of treatment progress appeared to e signicant to motiate compliance, although it could e argued that facial and occlusal improement is most liely in more compliant patients anyway otwithstand ing this, demonstrale change was frequently reported as a facilitator of appliance wear As such, the importance of encouragement and positie reinforcement y clini cians and family memers in encouraging appliance wear is clear Pilot studies in the eld hae demonstrated that nown monitoring increases patient compliance, The use of an app was effectie in increasing patient compliance in a xedappliance population ustomized reminders may help to promote enhanced leels of compliance with align ers thans to teleorthodontics Teleorthodontics is a road term that encompasses remote proision of orthodontic care, adice, or treatment through the medium of informa tion technology Teleorthodontics platforms using articial intelligence to remotely monitor patient adherence to the prescried wearing time are aailale eg, ental onitor ing, Paris, rance and hae een demonstrated to e effec tie in enhancing patient compliance

CAT Fundamentals Recap onsidering all the premises, aligner orthodontics is a ma ture orthodontic technique requiring orthodontists to man age it properly Some limitations in the appliance system remain, ut they in no way suggest unsatisfactory treat ment results iagnosis and treatment plans still remain the responsiility of clinicians and cannot yet e oercome y articial intelligence It is clear that treatment progress is not as easy and predictale as dictated y computer animation Therefore, giing priority to technology instead of orthodontics is dangerous The nowledge of iomechanics is crucial to properly manage clear aligner therapy oreoer, lie any other orthodontic technique, auxiliaries are manda tory to perform an efcient and predictale orthodontic treatment

4

References  Seymour B Polymers are eerywhere J Chem duc    iegelstein  Personomics the missing lin in the eolution from precision medicine to personalized medicine J ers ed  doipm  an , ia , heng , et al Saliary exosomes emerging roles in systemic disease nt J iol ci  doi is  de Aguiar , Perinetti , apelli r  The gingial creicular §uid as a source of iomarers to enhance efciency of orthodontic and functional treatment of growing patients iomed es nt   ashin , alci , Almuzian , et al arers in lood and salia for prediction of orthodontically induced in§ammatory root resorption a retrospectie case controlledstudy rog Orthod   Proft , ields  Contemporary Orthodontics th ed St ouis osy   ossini , Parrini S, eregius A, et al ontrolling orthodontic tooth moement with clear aligners an updated systematic reiew regarding efcacy and efciency J ligner Orthod   rünheid T, oh , arson B ow accurate is Inisalign in nonex traction cases? Are predicted tooth positions achieed? ngle Orthod   Burstone  harles  Burstone, S Part  iomechanics Interiew y r anda J Clin Orthod   Simon , eilig , Schwarze , et al Treatment outcome and efcacy of an aligner technique—regarding incisor torque, premolar derota tion and molar distalization C Oral ealth  doi   Simon , eilig , Schwarze , et al orces and moments generated y remoale thermoplastic aligners incisor torque, premolar dero tation, and molar distalization m J Orthod entoacial Orthop   Barone S, Paoli A, azionale A, et al omputational design and engineering of polymeric orthodontic aligners nt J Numer ethod iomed ng e  ennessy , arey T, AlAwadhi A A randomized clinical trial comparing mandiular incisor proclination produced y xed laial appliances and clear aligners ngle Orthod   ayes , Sarer , acoson A The quantication of soft tissue cericomental changes after mandiular adancement surgery m J Orthod entoacial Orthop   Sarer , Acerman  rthodontics aout face the reemergence of the esthetic paradigm m J Orthod entoacial Orthop   loresir , Sila , Barriga I, et al ay person’s perception of smile aesthetics in dental and facial iews J Orthod    Parrini S, ossini , astro§orio T, et al aypeople’s perceptions of frontal smile esthetics a systematic reiew m J Orthod entoacial Orthop   camara r A, Brudon  Orthodontic and Orthopedic Treatment in the ied entition Ann Aror eedham Press   auddin S, g P, Biswas S, et al Iatrogenic damage to the peri odontium caused y orthodontic treatment procedures an oeriew Open ent J   ati AS, urquim , onsolaro A ingial recession its causes and types, and the importance of orthodontic treatment ental ress J Orthod   aera S, astro§orio T, arino , et al axillary molar distalization with aligners in adult patients a multicenter retrospectie study rog Orthod  dois  arino , astro§orio T, aher S, et al ffectieness of composite attachments in controlling uppermolar moement with aligners J Clin Orthod   asy , asy A, Asatrian , et al ffects of ariale attachment shapes and aligner material on aligner retention ngle Orthod  doi  antoani , astro§orio , ossini , et al Scanning electron microscopy ealuation of aligner t on teeth ngle Orthod  doi  antoani , astro§orio , ossini , et al Scanning electron micros copy analysis of aligner tting on anchorage attachments J Oroac Orthop  dois



Principles and Biomechanics of Aligner Treatment

 ooi , Arai A, awamura , et al ffects of attachment of plastic aligner in closing of diastema of maxillary dentition y nite element method J ealthc ng   omez P, Peña , artínez , et al Initial force systems during odily tooth moement with plastic aligners and composite attach ments a threedimensional nite element analysis ngle Orthod   Breznia  The clear plastic appliance a iomechanical point of iew ngle Orthod   astro§orio T, arino , azzaro A, et al pperincisor root control with Inisalign appliances J Clin Orthod   rünheid T, aalaas S, amdan , et al ffect of clear aligner ther apy on the uccolingual inclination of mandiular canines and the intercanine distance ngle Orthod   Ballard  Asymmetry in tooth size, a factor in the etiology, diagnosis, and treatment of malocclusion ngle Orthod   oretsi , hatzigianni A, Sidiropoulou S namel roughness and in cidence of caries after interproximal enamel reduction a systematic reiew Orthod Cranioac es   achrisson B, yøygaard , oarac  ental health assessed more than  years after interproximal enamel reduction of man diular anterior teeth m J Orthod entoacial Orthop   Sarig , ardimon A, Sussan , et al Pattern of maxillary and mandiular proximal enamel thicness at the contact area of the permanent dentition from rst molar to rst molar m J Orthod entoacial Orthop   ortona A, ossini , Parrini S, et al lear aligner orthodontic ther apy of rotated mandiular conical teeth a nite element study ngle Orthod  Sumitted for pulication minor reision  anda  r aindra anda on orthodontic mechanics Interiew y oert  eim J Clin Orthod   uhlerg A, Priee  Testing force systems and iomechanics— measured tooth moements from differential moment closing loops ngle Orthod   aoody A, Posada , trea A, et al A prospectie comparatie study etween differential moments and miniscrews in anchorage control ur J Orthod 

 ie P Treating imaxillary protrusion and crowding with the inisalign  rst premolar extraction solution and inisalign aligners O Trends Orthod   iu , u  orce changes associated with different intrusion strategies for deepite correction y clear aligners ngle Orthod   rishnan , aidoitch  iological echanisms o Tooth ovement nd ed ooen,  ileyBlacwell   uncio , aganzini A, Shelton , et al Inisalign and traditional orthodontic treatment postretention outcomes compared using the American Board of rthodontics oectie grading system ngle Orthod   attaneo P, alstra , elsen B Strains in periodontal ligament and aleolar one associated with orthodontic tooth moement analyzed y nite element rthod raniofac es    astro§orio T, amerro , aiglia P, et al Biochemical marers of one metaolism during early orthodontic tooth moement with aligners ngle Orthod   Aloghrai , Salazar , Pandis , et al ompliance with remo ale orthodontic appliances and aduncts a systematic reiew and metaanalysis m J Orthod entoacial Orthop   luni A, olonio Salazar B, Sharma P, et al nderstanding factors in§uencing compliance with remoale functional appli ances a qualitatie study m J Orthod entoacial Orthop   Pauls A, ienemper , Panayotidis A, et al ffects of wear time recording on the patient’s compliance ngle Orthod   Arreghini A, Trigila S, omardo , et al ectie assessment of compliance with intra and extraoral remoale appliances ngle Orthod   i , u , Tang , et al ffect of interention using a messaging app on compliance and duration of treatment in orthodontic patients Clin Oral nvestig   ansa I, Semaan S, aid , et al emote monitoring and “tele orthodontics” concept, scope and applications emin Orthod 

6

Class I Malocclusion MARIO GRECO

Introduction Class I malocclusions represent one of the most common conditions in the daily clinical practice and one of the most elective conditions to be treated with aligners, since the primary patients’ concern is often represented by crowded anterior teeth, especially in the mandibular arch.1 Working with clear aligners challenges the paradigm on which we, as orthodontists, based the traditional ed me chanics approach. Working with aligners means that we need to plan everything in advance and not on a monthly basis, dening nal teeth position from the beginning and spending more time in treatment plan design and staging than at the chairside.

Diagnostic Reference When dealing with class I malocclusion, the rst step to con sider is the denition of the biologic limits of the arches. We should identify anterior, frontal, and vertical limits. ll the limits represent both a morphologic limit torue posterior and anterior strictly connected to bone and teeth pattern of movement and an esthetic indication to dene eactly the ideal teeth positioning in relationship to lips and face. ore specically, during treatment plan in class I maloc clusion a very schematic approach could be focused on the observation and respect of the following key points n

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sthetic key points face midline, smile arc, intraarch symmetry cclusal key points olton analysis, overet, incisors inclination

ubstantially the esthetic indicators represent the limits in which teeth need to be moved on the horiontal plane arch symmetry, face midline and on the vertical plane smile arc the occlusal indicators are useful to dene the proper veret needed to ensure anterior clearance and avoiding premature anterior contacts causing posterior open bite in relation ship to dental sie and anterior limit of dentition.

Treatment Plan he development of proper treatment plan in class I maloc clusion starts from the denition of correct staging of movement to create a reliable digital setup and to reach a predictable result with high superimposition between the real and the digital settings. he ideal approach in terms of treatment staging should be based on curve of pee level ing, incisor control, arch development, rotation control, attachment choice, and interproimal reduction I.

CURVE OF SPEE LEVELING o avoid anterior premature contacts, to create the proper cuspids and molars intercuspations, and to allow lower incisor leveling and correct anterior relationship related to guidance function, attening of the curve of pee is reuired. oreover, the assessment of the amount of lev eling will give information about the space needed for curve attening.

INCISOR CONTROL aving in mind the precise angular inclination of lower incisors according to the cephalometric references and us ing the superimposition tool andor the movement table tool, together with the grid tool of digital setup software, is possible to determine the amount of proclination or retro clination reuired to properly locate the lower incisors on the sagittal plane.

ARCH DEVELOPMENT In terms of treatment approach, epansion represents a very common solution to treat crowding and transverse discrepancy. uccal tipping movement is more predictable than bodily movement when planning arch epansion with aligners. his should be kept in mind when dening the buccolingual inclination of canine premolars and molars respecting the periodontal condition.

ROTATION CONTROL otation of small teeth or round teeth such as premolars could be considered a difcult movement to achieve be cause of the reduced tooth surface on which the force can be applied. Comple rotations should be managed by rst creating the mesial and distal spaces reuired to rotate teeth and then choosing the proper attachment.

ATTACHMENT CHOICE ttachments represent a useful tool to increase the surface on which orthodontic forces could be applied ig. .1. ee previous chapters for more details.

INTERPROXIMAL REDUCTION ne common procedure in aligner techniue is represented by the I, which ideally should be limited to . mm per in terproimal point to avoid too wide enamel reduction. he management of I is fundamental not only for ing crowd ing problems and nding more space but also to control the 51

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Principles and Biomechanics of Aligner Treatment

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B Fig. 6.1 Biomechanical design of conventional attachments for extrusion (A) and distal rotation (B)

incisor inclination i.e., creating space with I could rep resent a reliable system to upright upper or lower incisors, to compensate olton discrepancy by reducing teeth ecess, and to create symmetric dimension between left and right sides.1

I could represent a reliable solution to recreate ideal alignment, but some options during the digital setup plan ning need to be controlled to avoid collateral effects, as follows n

Class I Conditions Class I malocclusions can be divided into different catego ries following the principal condition that affects speci cally one or more dimensions of the space transverse or vertical or which creates a determinate discrepancy. or this reason they will be discussed separately.

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DENTOALVEOLAR DISCREPANCY he most common condition is represented by crowding in the upper or lower arch or both. he clear aligner treatment C of crowding is highly predictable when approached with the proper staging such as epansion, small proclina tion, reduced I, and torue correction. ormally, being able to avoid etractions means that treatment options available are related to epansion  mm per uadrant and I . mm maimum per interproimal space. he se verity of crowding, particularly in the lower aw, signi cantly affects the possibility of avoiding etraction treat ment. Conditions in which it is reasonable to treat without etraction are as follows n

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void ecessive proclination of lower incisors by means of using the superimposition tool and the grid tool of the software and by favoring transverse epansion and con seuently a more uprighted position of lower incisors ig. .. lace the lower premolars to a buccal crown torue net to ero to recreate space without changing the interca nine width when on the occlusal picture of lower aw, it is possible to observe the labial surface of premolars, torue correction could be achieved ig. .. Combine class III elastics to create the proper  1. mm and to favor the correction of crowding also in absence of real class III relationship ig. .. Create upper and lower aw ideal shape to avoid black triangles and buccal facial corridors ig. .. lan specic attachments see Chapter  ig. ..

ight crowding, with normal amount of I .1 . mm ild to moderate crowding, with combination of epan sion without changing intercanine width and maimum rate of . mm of I per interproimal space oderately severe crowding, combining the .mm I per interproimal space with torue correction of lower premolars to create a positive torue up to a maimum of  degrees of buccal torue inclination

his means that when the crowding is lower than  mm per uadrant, the possibility to combine epansion and

Fig. 6.2 ClinCheck tools to check incisor inclination.

6 • Class I Malocclusion

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E Fig. 6.3 Pretreatment records oung adult patient ith severe croding and negative premolar torue. (A intraoral pictures)

TOOTH SIZE DISCREPANCY he olton analysis is important because it allows the im mediate visualiation of the interarch and intraarch dis crepancies. hese discrepancies can affect the nal overet. ot considering the olton analysis in our treatment plans could lead to several unfavorable outcomes anterior prema ture contacts with posterior open bite without reaching a proper class I intercuspation on both sides, ecessive procli nation of incisors, and uncorrected closure of upper diaste mas. herefore, the tooth sie discrepancy analysis is crucial when designing orthodontic treatment. thman and arra dine recommended a threshold of mm discrepancy to be

of clinical signicance for restorative intervention igs. . and ..111 nother common condition of tooth sie discrepancy is represented by dental anomalies in number bilateral or monolateral agenesis and dental anomalies in shape mi crodontia, pegshaped lateral incisors. In the case of a monolateral agenesis in the anterior area missing upper lateral incisor, the olton analysis can provide the precise dimension of the contralateral incisor helping the clinician in dening the right space that needs to be preserved for the nal restoration. In case of pegshaped contralateral incisor the olton analysis provides information regarding the

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Principles and Biomechanics of Aligner Treatment

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E Fig. 6.4 Posttreatment records oung adult patient ith severe croding and negative premolar torue treated ith torue correction and interproximal reduction. (A intraoral pictures)

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Fig. 6.5 (A) Pretreatment records oung adult patient ith narro up per arch and smile lack corridors. (B) Posttreatment records oung adult patient ith narro upper arch and smile lack corridors treated ith upper expansion and loer torue correction.

Fig. 6.6 oule conventional attachment in case of severe rotation.

6 • Class I Malocclusion

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Fig. 6. Pretreatment records tooth sie discrepanc A intraoral pictures.

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Fig. 6. Posttreatment records toothsie discrepanc treated  space opening and interproximal reduction A igital proect B intraoral pictures.

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golden proportion between the anterior si teeth helping the clinician in determining the right space to be preserved for the nal restorations. In the case of bilateral agenesis in which the treatment is designed to close the space of later als with mesial movement of canines, premolars, and mo lars, the tooth sie discrepancy values are fundamental to reduce the dimension of canines that will become laterals and to increase the dimension of premolars that will be come canines.11

TRANSVERSE DISCREPANCY ne of the most duple conditions to be treated with aligners is represented by the transverse discrepancy the term duplex refers to the different compleity in the treat ment of anterior crossbite and posterior crossbite, since anterior crossbite represents an elective condition to be treated with aligners while the posterior relies its possibil ity to be successful on the severity of posterior crossbite and on the use of supporting auiliary devices cross elastics ig. .. he anterior crossbite central, lateral, or canine in bilat eral or monolateral conguration is a perfect condition to be approached with Invisalign aligners since the thickness of the aligner itself avoids any need of bite turbos to create disclu sion, a condition needed during traditional ed orthodontics. or this reason, the treatment of one single element of anterior crossbite could be predictably ed with a lite lite is the com mercial name of Invisalign with reduced number of aligners. or this reason is not light but lite. reatment if the rest of

Fig. 6.1 Anterior contact during uccal movement for crossite resolution.

malocclusion conditions permits this simplied approach. he following should be done to increase predictable results n

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uring treatment the buccal movement of laterals or centrals will create an edgetoedge contact to overcome this traumatic contact, it may be convenient to change aligners more rapidly to reduce the time eposed to trauma ig. .1. ogether with labial movement to  the crossbite, some millimeters of etrusion should be planned to create normal overbite. enerally, in case of anterior crossbite, the ape of the element is located more buccal compared to the crown for this reason, unparticular root movement is reuired igs. .11 and .1.

he correction of posterior crossbite represents a vari able, predictable correction with aligners according to the severity of the crossbite one single element crossbite could be easily managed only by the system, while for the correc tion of severe maillary contraction with multiple elements in crossbite the use of auiliaries is widely suggested. In particular, these indications should be followed to create a reliable correction n

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Fig. 6. Cross (AB intraoral pictures) elastics to support posterior expansion.

In case of single element crossbite, more crown torue should be planned instead of buccal epansion. In case of multielement crossbite, buttons for crisscross elastics should be planned to help the correction and sup port the elastic modication of the aligners by using di rect bonding on the teeth and cooperation with 1 hours of elastics  o,  mm. o simplify the correction, some minimal I in the in terproimal spaces could be helpful only to remove pos sible initial interferences while starting the epansion. he use of bite ramps even in the absence of deep bite is strongly suggested. It could simplify the posterior move ment creating disclusion, favoring the buccal movement and the vertical etrusion moment in combination with crisscross elastics igs. .1 and .1. ccording to the malocclusion, further elastics for sagit tal control should be planned class II or III ig. .1. In case of severe maillary contraction, a crown torue inclination assessment should be done to understand the amount of possible correction only with dental epansion.

6 • Class I Malocclusion

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D Fig. 6.11 Pretreatment records of lateral incisor in anterior crossite. A intraoral pictures

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D Fig. 6.12 Posttreatment records ith complete correction of crossite in reduced numer of aligners. AB intraoral pictures

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Principles and Biomechanics of Aligner Treatment

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E Fig. 6.13 Pretreatment records of severe posterior crossite ith maxillar contraction. A intraoral pictures

he predictable plan for posterior crossbite is basically focused on epansion up to . mm per uadrant. If the crown torue of lateral elements and the periodontal condi tion could allow this kind of correction, the combined use of bite ramps and crisscross elastics could predictably in crease the outcome achievement.

MORPHOLOGIC DISCREPANCY ess common conditions of class I malocclusions are repre sented by those situations of teeth with morphologic anom alies, such as single or multiple anterior agenesis and microdontia conoid laterals, that affect the orthodontic

treatment and ideal outcome according to the therapeutic choice. ll morphologic discrepancies are strictly connected to olton discrepancy, and for this reason the same approach described later should be followed to achieve proper occlu sal outcome and normal overet. oreover, an important consideration should be done on the microesthetics and macroesthetics when teeth show a different shape. In the case of monolateral dental morphologic anomaly conoid or agenesis, it becomes necessary to leave the proper space to concentrate on the opposite normal shape element dimension. he olton button could provide infor mation about teeth sie, and on the ClinCheck it is possible

6 • Class I Malocclusion

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F Fig. 6.14 Posttreatment records after expansion 1 torue correction 1 interproximal reduction 1 ite ramps. A intraoral pictures  igital setup shoing ite ramps for posterior disocclusion.

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B Fig. 6.15 Class III elastics. A intraoral pictures B igital etup

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Principles and Biomechanics of Aligner Treatment

to plan space opening mesial and distal to the conoid ele ment to organie the nal restoration ig. .1. In case of single agenesis, one further assessment should be done con cerning the space between the roots. ince the nal restora tion will be an implant, it is fundamental to measure the space between the apees to realie if the outcome could be achieved only with aligners or some auiliaries will be needed. When the apical distance is around  mm, no other special auiliaries will be needed, ust the space opening between crowns, while when the distance is less than  mm, some auiliaries lingual sectional or power arm could be necessary to achieve the proper space for implant insertion igs. .1 and .1. In the case of agenesis of both lateral incisors, the choice of space closure with total mesial movement of posterior teeth or space opening for implant insertion has long been discussed in the literature.11 ctually, in case of young patients, the ideal solution seems to be the space closure with reshaping of the canines both additive and subtrac tive enamel plastic to simulate laterals combined with re shaping of rst premolars simulating canines additive enamel plastic. he advantages of approaching with

aligners are the possibility to have all the information about sie of the teeth olton tool, balancing I on ca nines and space opening on rst premolars to create ideal anterior relationship between the si anterior teeth com bined with leveling the anterior gingival margins to create a harmonic smile igs. .1 and ..

PREPROSTHETIC NEED he last common condition analyed of class I malocclu sion is strongly related to those situations in which the orthodontic treatment could be helpful in creating more favorable conditions for prosthetic solution, thus gaining space where it was missing for nal restoration. eing very schematic, two conditions in adult patients with missing teeth commonly reuire the orthodontic support to achieve an ideal prosthetic solution, namely 1. ipping in the edentulous space . vereruption in the edentulous space he mesial tipping of molars, in particular the tipping of second molars because of missing rst molar, represents a

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C Fig. 6.16 pace opening for Peg shaped restoration. A pretreatment B digital plan C post treatment

6 • Class I Malocclusion

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E Fig. 6.1 Pretreatment records of lateral incisor agenesis ith apical distance less than  mm. A intraoral pictures  panoramic xra

freuent condition sometimes combined with distal tipping of premolars.11 pproaching this problem with the align ers is highly predictable because of the following n

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he force to upright the second molar creates a reaction force, which upright the premolars and this reciprocal force work properly together in opening the space ig. .1. he amount of space can be decided in advance on the software according to the dimension of the contralateral element.

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o be more efcient, it is possible to ask to avoid pontics in the edentulous area to leave the aligner to embrace more surfaces of the molar to upright delivering more homogeneous force. In the ClinCheck plan it is fundamental to combine distal inclination of crown with distal movement to put the center of rotation net to the ape.

or the same reason when one or more teeth are missing, the problem could happen in another dimension of the

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Principles and Biomechanics of Aligner Treatment

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E Fig. 6.1 Posttreatment records of monolateral lateral incisor agenesis ith Invisalign and xed sectional for root control. A intraoral pictures

space affecting the vertical movement overeruption of molars. pproaching this problem with traditional orthodontics means that an auiliary device for skeletal anchorage in the bone will be strongly needed. he traditional biomechanics to intrude molars are highly comple for anchorage lack.11 he opportunity to solve the overeruption with aligners simplies the treatment because the vertical force

of intrusion is applied to the teeth by means of labial, lin gual, occlusal, and distal surface not only on side, and it generates a reaction force that tends to etrude the ada cent tooth blocked by the occlusion and the thickness of aligners. his biomechanical system is more in balance when compared to traditional, and if no other movements in different planes are reuired, it can be accomplished in reduced number of aligners igs. . and ..

6 • Class I Malocclusion

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D Fig. 6.1 Pretreatment records of ilateral lateral incisors agenesis. A intraoral pictures

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D Fig. 6.2 Posttreatment records of ilateral lateral incisors agenesis treated  space closure and teeth reshaping. A intraoral pictures

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Principles and Biomechanics of Aligner Treatment

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Fig. 6.21 pace opening  distal tipping of molars. A pretreatment intraoral picture B posttreatment intraoral picture ith implant inserted

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C Fig. 6.22 Pretreatment records of overerupted upper second molar. AB intraoral pictures C panoramic xra

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C Fig. 6.23 Posttreatment records of overerupted upper second molar treated  aligners onl. AB intraoral picture C panoramic xra

6 • Class I Malocclusion

References 1. ossini , arrini , Castroorio , et al. fcacy of clear aligners in controlling orthodontic tooth movement a systematic review. Angle Orthod. 11. . achdeva . Integrating digital and robot technologies diagnosis, treatment planning, and therapeutics. In raber , anarsdall , ig, W, eds. Orthodontics Current Principles and Techniques. th ed. lsevier 11. . chol , achdeva C. Interview with an innovator uremile chief clinical ofcer ohit C. . achdeva. Am J Orthod Dentofacial Orthop. 111. . imon , eilig , chware , et al. reatment outcome and efcacy of an aligner techniue—regarding incisor torue, premolar derotation and molar distaliation. BMC Oral Health. 11. . eli I, turk , ysal . Curve of pee and its relationship to vertical eruption of teeth among different malocclusion groups. Am J Orthod Dentofacial Orthop. 111. . epedino , ranchi , abbro , et al. ostorthodontic lower incisor inclination and gingival recession—a systematic review. Prog Orthod. 1111. . apadimitriou , ousoulea , kantidis , et al. Clinical effective ness of Invisalign® orthodontic treatment a systematic review. Prog Orthod. 111. . imon , eilig , chware , et al. orces and moments generated by removable thermoplastic aligners incisor torue, premolar derotation, and molar distaliation. Am J Orthod Dentofacial Orthop. 11 . . ravit , usnoto , gran , et al. Inuence of attachments and interproimal reduction on the accuracy of canine rotation with Invisalign.  prospective clinical study. Angle Orthod.  .

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1. eredith , arella , owrey , et al. tomic force microscopy anal ysis of enamel nanotopography after interproimal reduction. Am J Orthod Dentofacial Orthop. 111. 11. thman , arradine W. oothsie discrepancy and olton’s ratios the reproducibility and speed of two methods of measurement. J Orthod. . 1. Cançado , onçalves únior W, alarelli , et al. ssociation between olton discrepancy and angle malocclusions. Braz Oral es. 11. 1. osa , achrisson . Integrating space closure and esthetic dentistry in patients with missing maillary lateral incisors. J Clin Orthod. 1. 1. osa , ucchi , errari , et al. Congenitally missing maillary lat eral incisors longterm periodontal and functional evaluation after orthodontic space closure with rst premolar intrusion and canine etrusion. Am J Orthod Dentofacial Orthop. 11. 1. amilian , erillo , osa . issing upper incisors a retrospective study of orthodontic space closure versus implant. Prog Orthod. 11. 1. iancotti , arina . reatment of collapsed arches using the Invisalign system. J Clin Orthod. 11. 1. ampieri , iancotti . Invisalign techniue in the treatment of adults with prerestorative concerns. Prog Orthod. 11. 1. rslan , demir , ursoyert , et al. Intrusion of an over erupted mandibular molar using miniscrews and miniimplants a case report. Aust Dent J. 11. 1. ripathi , alra , ai , et al. rue intrusion of maillary rst mo lars with ygomatic and palatal miniscrew anchorage a case report. Aust Orthod J. 1.

7

Aligner Treatment in Class II Malocclusion Patients TOMMASO CASTROFLORIO, WADDAH SABOUNI, SERENA RAVERA, and FRANCESCO GARINO

Introduction Since the introduction of clear aligner treatment (CAT), controversy has existed over whether moderate to difcult orthodontic treatment can be routinely accomplished with aligner techniue hen dealing with class  malocclu sions, CAT offers different possible therapeutic options      

istaliation olar derotation lastic ump xtractions andibular advancement rthognathic surgery

MAXILLARY MOLAR DISTALIZATION n some nonextraction cases, maxillary molar distaliation is the method of choice to gain  to  mm of space in the dental arch to obtain a class  relationship in both teens and adults The upper molars can be distalied by means of extraoral or intraoral forces xtraoral traction with headgear has a long history of use in class  treatment since it has been designed to push distally the maxilla and the maxillary mo lars, n recent years, several techniues have been devel oped to reduce the dependence on patient compliance, such as intraoral appliances with and without seletal anchor age owever, even these devices can produce undesirable tipping of the maxillary molars andor loss of anterior an chorage during distaliation, To achieve a tooth bodily movement implies that the applied force must pass through the center of resistance of the tooth or a sophisticated euivalent system of forces and moments needs to be ap plied to the tooth crown A recent review of the existing literature assessed the efcacy of aligners in aligning and straightening the arches, with better results for mild to moderate crowding when compared to the results obtained with xed appliances ore recently, it was stated that the overall available evidence regarding orthodontic tooth movement (T) control during CAT increased signi cantly, with three randomied controlled trials (CTs) at grade A and an overall uality of evidence of moderate high level, and that maxillary molar distaliation of  mm and premolar extraction space closure ( mm) are the most predictable and controlled movements with CAT n , Simon et al stated that maxillary molar dis taliation was the most predictable movement () to

66

perform with CAT The authors started to focus on the ey role of a correct staging of the planned movement and of the adoption of proper attachments during the whole dis taliation phase Thus a highly signicant element of bias in the  study by rae et al was the staging of  mm per aligner instead of the  mm recommended n , avera et al conrmed the results of Simon et al and demonstrated that distaliation is efciently achievable up to  mm on the rst and second maxillary molars, with optimal vertical control of posterior teeth and any loss of anchorage on the anterior teeth These results were obtained through the combination of staging, vertical rectangular attachments, and class  elastics (– o) for anchorage reinforcement The use of attachments and elastics was previously described by expert clinicians The application of composite attachments could be useful to improve the biomechanic efciency of aligner therapy ong vertical attachments located on the buccal aspect of the molars can create a sufcient moment to oppose the tipping movement Thus long vertical attachments can provide good tipping control while molars are moving and then can increase posterior anchorage while retracting anterior teeth The need for a determined attachment combination was conrmed in a  CT by arino et al, who ob served signicant differences in the amount of distalia tion when comparing a veattachment conguration (second and rst molars, second and rst premolars, and canine) with a threeattachment conguration (rst mo lar, second and rst premolars), with the rst ones being most efcient Controlling the tipping movement during molar distaliation can be difcult because of the limited alignertooth surface in the direction of force application The absence of long rectangular attachments on the sec ond molar resulted in a probable loss of anchorage during the distaliation of the rst molar, with conseuent re duced amount of distal movement of the second molar at the end of the treatment and signicant tipping of the rst molar urthermore, the absence of a proper anchorage preparation in the distal portion reduced the possibility of an adeuate control of the retracting anterior teeth As a result, the central incisors showed an uncontrolled tip ping movement in the group with a threeattachment conguration ecently ome et al demonstrated that when the aligner segment was displaced distally without attach ments, a clocwise moment and distal inclination were

7 • Aligner Treatment in Class II Malocclusion Patients

produced on the upper canine The presence of composite attachments helped counteract this inclination, producing a countermoment that in turn favored a bodily movement n another nite element analysis study, Comba et al demonstrated that the use of attachments on tooth surface counteracts the uncontrolled tipping during distaliation through the generation of a countermoment that ends in the root uprighting This moment is dependent from a com plex force system and is generated by the active surfaces of attachments hen analying a couple of attachments located on the buccal surface of an upper canine, one located at the distocervical portion and the other located at the mesioincisal portion, compression areas were found on the mesial face of the cervical attachments and on the distal face of the incisal attachment These outcomes validate ome ndings The vertical pattern is an important point to consider while planning molar distaliation The distal movement measured in our study was associated with signicant in trusion movements of the molars The thicness of the aligners and the conseuent occlusal force exerted on them might facilitate intrusion and explain the absence of any change of anterior vertical dimension while distaliing urthermore, ome et al reported a mared tendency of “aring” of the buccal and palatal ans of the aligner seg ment during distal displacement This nding is interesting because it could suggest an intrusive effect on the tooth The aligner therapy is a customied orthodontic treat ment for both the patient and the orthodontist The pres ence of composite attachments for the control of the maxillary molars during the distaliation process is a choice of the prescribing clinician for most of the avail able systems in the maret

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The effect of elastics is simulated as a onestage antero posterior movement at the end of treatment, which enables verication of the nal arch coordination and occlusion ewer aligners are reuired when simultaneous stag ing is used along with use of elastics as compared with distaliation owever, a preparation phase in which all the possible interarch interferences are removed is re uired in the virtual setup planning to create enough room in which the class  elastics can promote their effects espite the large use of class  elastics in everyday prac tice, little evidence is nown about their effects A recent systematic review stated that the current literature sug gests using light forces (average,  o) obtained with a in diameter elastic and a rectangular  to in stainless steel archwire n aligner orthodon tics, the use of in diameter  o was recom mended, on the basis of expert clinician experience owever, as shown in Chapter , nite element analysis has shown the need for stronger class  elastics in CAT ecause class  elastics heavily rely on patient compliance, fulltime usage is recommended t has been described as an average period of  months for the correction of the class  discrepancy with elastics only, and the correction is usually obtained with predominant dentoalveolar effects This is the average treatment time reuired to correct an endtoend class  malocclusion according to existing lit erature

EXTRACTIONS lease refer to Chapter  for specics on extractions

MANDIBULAR ADVANCEMENT MAXILLARY MOLAR ROTATION esiopalatal rotation of the upper rst molar is present in about  of patients with angle class , division  maloc clusion and in  of them as a whole  esiopalatal rotation of upper rst molars often ends up in an intraarch loss of space reuently, this crowding occurs in the pre molar and canine segments, thus potentially preventing the correct mesiodistal position of these teeth n this basis, buccodistal rotation of maxillary molars can be considered a useful procedure to partially improve class  dental rela tionship olar rotation was indicated as one of the predict able movements controlled by aligners

lease refer to Chapter  for specifics on mandibular advancement

ORTHOGNATHIC SURGERY rthognathic surgery consists of surgical procedures performed on the maxilla andor the mandible to correct serious basal malocclusions and to harmonie the prole t is benecial in adults since the most difcult cases cannot be treated by orthopedic and orthodontic therapy alone lease refer to Chapter  for specics on orthognathic surgery

THE ELASTIC EFFECT The elastic effect can be dened as class  correction using interarch mechanics t is simulated on virtual setups by a umplie shift of the occlusion from class  to class  to al low easier visualiation of the anticipated treatment goal ndividual tooth movements reuired to align teeth are set up to proect the effect of this bite correction using buttons and elastics lastic wear is recommended from the start of treatment, continuing until the desired anteroposterior correction has been achieved

The Clinical Protocol istaliation is performed to correct average to moderate class  malocclusions (, mm) by retracting the maxillary teeth istaliation should be preferred in patients present ing a class  malocclusion due to maxillary protrusion or in adult patients undergoing compromise treatment uring distaliation, it is essential to use class  elastics or miniscrews to avoid loss of anchorage at the anterior teeth,,

68

Principles and Biomechanics of Aligner Treatment

epending on the severity of the sagittal malocclusion, we can use different clinical approaches n

n

n

or dental sagittal discrepancies where less than  mm of distaliation are needed, we can safely perform aligner driven seuential distaliation or dental discrepancies ranging between  and  mm, depending on the clinical situation, we perform seuen tial distaliation combined, or not, with stripping, molar derotation, or an elastic effect f dental discrepancy exceeds  mm, we opt for either extrac tion treatment or orthognathic surgery, once again depend ing on the clinical situation and the patient’s decision

Maxillary Distalization Case Reports CASE SUMMARY 1 A yearold female patient ased for an aesthetic orth odontic treatment easy to manage considering her ob as a maeup artist traveling across urope

She presented a class , division  relationship, mild crowding in the lower arch, and moderate crowding in the upper arch The overet was increased to  mm The prole analysis revealed protruded lip position (ig ) Considering the aesthetics reuest of the patient and her refuse for surgical interventions or extractions, the treatment plan was designed to obtain a nal molar and canine class  relationship through a seuential dis taliation of the maxillary teeth using nvisalign (Align Technology nc, San osé, CA, SA) aligners, composite attachments on all the distaliing teeth, and class  elastics   (ig ) The patient was instructed to wear the aligners and the class  elastics for at least  hours per day urthermore, she used the Acceleent device for  minutes every day of the orthodontic treatment Aligners were changed ev ery  wees until the maxillary second molars were fully distalied, then every  days until the rst molars were in their nal position, and then every  days until the end of treatment The ClinChec (Align Technology nc, San osé, CA, SA) software revealed the need for  aligners to obtain the prescribed results (distaliation planned for

Fig. 7.1 Case 1 initial clinical and radiographic records.

7 • Aligner Treatment in Class II Malocclusion Patients

69

Fig. 7.1, ’

 mm) with the prescribed seuence of stages, attach ments, and class  elastics Thus the estimated treatment time was approximately  months The patient chose to use Acceleent, and the case was closed in  months of treatment without further aligner with respect to the prescribed (ig ) The clinical results were excellent and revealed nal molar and canine class  relationships with functional overbite and overet The prole of the lower third of the

face was highly improved with respect to the beginning (ig ) The superimposition of the cephalometric tracings re vealed a maxillary molar distaliation of about  mm without signicant tipping and an excellent control of the buccolingual inclination of the incisors (ig ) The class  elastics were responsible for a mandibular protraction of about  mm etention was provided by ivera (Align Technology nc, San osé, CA, SA) retainers

7

Principles and Biomechanics of Aligner Treatment

Fig. 7. Case 1 frontal and sagittal views of initial ClinCheck.

Fig. 7. Case 1 nal clinical and radiographic records.

7 • Aligner Treatment in Class II Malocclusion Patients

Fig. 7., ’

71

7

Principles and Biomechanics of Aligner Treatment

Fig. 7. Case 1 frontal and sagittal views of nal ClinCheck.

Fig. 7. Case 1 lateral ra comparison and cephalometric maillar superimposition efore and after therap.

CASE SUMMARY  A yearold female patient ased for an aesthetic orth odontic treatment easy to manage She presented a class , division  relationship, moderate crowding in the upper arch, and mild crowding in the lower arch The overet was increased to  mm The prole analy sis revealed an acceptable lip position (ig ) Considering the aesthetics reuest of the patient and her refuse for orthognathic surgery, the treatment plan was designed to obtain a nal molar and canine class  relation ship by a seuential distaliation of the maxillary teeth using nvisalign (Align Technology nc, San osé, CA, SA) aligners, composite attachments on all the distaliing teeth, and class  elastics The average distaliation movement prescribed was  mm (ig )

The patient was instructed to wear the aligners and the class  elastics for at least  hours per day Aligners were changed every  wees until the maxillary second molars were fully distalied, then every  days until the rst molars were in their nal position, and then every  days until the end of treatment The ClinChec (Align Technology nc, San osé, CA, SA) software revealed the need for  aligners to obtain the prescribed results with the prescribed seuence of stages, attachments, and class  elastics The estimated treatment time was approximately  months n an intermediate phase, rst outcomes of seuential distaliation were clearly visible As shown in igs  and , molars already distalied in a correct class  relation ship were spaced apart from premolars

7 • Aligner Treatment in Class II Malocclusion Patients

The clinical results were excellent and revealed nal molar and canine class  relationships with correct overbite and overet The prole of the lower third of the face was slightly improved with respect to the beginning, since the aesthetic analysis and cephalometric measurements showed acceptable values at the beginning of the treatment already (igs  and )

7

The superimposition of the cephalometric tracings revealed a maxillary molar distaliation of about  mm without significant tipping and an excellent control of the buccolingual inclination of the incisors (ig )

Fig. 7.6 Case  initial clinical and radiographic records. Continued

7

Principles and Biomechanics of Aligner Treatment

Fig. 7.6, ’

Fig. 7.7 Case  frontal and sagittal views of initial ClinCheck.

7 • Aligner Treatment in Class II Malocclusion Patients

Fig. 7.8 Case  upper occlusal views at the eginning after molar distaliation and at the end of therap.

Fig. 7.9 Case  end of distaliation intraoral frontal occlusal and sagittal views.

7

76

Principles and Biomechanics of Aligner Treatment

Fig. 7.1 Case  nal clinical and radiographic records.

7 • Aligner Treatment in Class II Malocclusion Patients

Fig. 7.1, ’

Fig. 7.11 Case  frontal and sagittal views of nal ClinCheck.

77

78

Principles and Biomechanics of Aligner Treatment

Fig. 7.1 Case  lateral ra comparison and cephalometric maillar superimposition efore and after therap.

CASE SUMMARY  This yearold female patient has no previous orthodontic history, a full mm left and rightside molar class  maxil lary alveolar arch width deciency,  mm of maxillary crowding, a mm overbite, and an mm overet Seletally she presented a hypodivergent class  and a cervical verte brae maturation (C) stage  sthetically her face was harmonious in both frontal and lateral views (ig ) esidual growth was insufcient to consider orthopedic treatment Conseuently, taing into account the aesthetics reuest of the patient, the treatment plan was designed to correct the class , achieving nal molar and canine class  relationship by molar derotation, seuential distaliation, and elastic ump using nvisalign (Align Technology nc,

San osé, CA, SA) aligners, composite attachments on all the distaliing teeth, and class  elastics The average distal iation movement prescribed was  mm The patient was instructed to wear the aligners and the class  elastics for at least  hours per day Aligners were changed every  wees until the maxillary second molars were fully distalied, then every  days until the rst molars were in their nal position, and then every  days till the end of treatment To obtain the prescribed results,  aligners were needed (ig ) The clinical results were good and showed nal molar and canine class  relationships with correct overbite and overet The prole of the lower third of the face was improved with respect to the initial records (ig )

Fig. 7.1 Case  initial clinical and radiographic records.

7 • Aligner Treatment in Class II Malocclusion Patients

Fig. 7.1, ’ Continued

79

8

Principles and Biomechanics of Aligner Treatment

Fig. 7.1, ’

Fig. 7.1 Case  sagittal views of initial intermediate nal pre and postump ClinCheck.

Fig. 7.1 Case  nal clinical and radiographic records.

7 • Aligner Treatment in Class II Malocclusion Patients

Fig. 7.1, ’

81

8

Principles and Biomechanics of Aligner Treatment

References  oyd  sthetic orthodontic treatment using the nvisalign appliance for moderate to complex malocclusions J Dent Educ   anda S, Tosun S Correction of Anteroposterior Discrepancies anover ar uintessence ublishing Co   rec , anson , ranco C, et al ntraoral distalier effects with conventional and seletal anchorage a metaanalysis Am J Orthod Dentofacial Orthop   ontana , Coani , Caprioglio A oncompliance maxillary molar distaliing appliances an overview of the last decade Prog Orthod   golf , eole A, pshaw S actors associated with orthodontic patient compliance with intraoral elastic and headgear wear Am J Orthod Dentofacial Orthop   uiy A, odrigues de Almeida , anson , et al Sagittal, vertical, and transverse changes conseuent to maxillary molar distaliation with the pendulum appliance Am J Orthod Dentofacial Orthop    ontana , Coani , Caprioglio A Soft tissue, seletal and dentoal veolar changes following conventional anchorage molar distaliation therapy in class  nongrowing subects a multicentric retrospective study Prog Orthod   usy  nuence of force systems on archwirebracet combinations Am J Orthod Dentofacial Orthop   ossini , arrini S, Castroorio T, et al fcacy of clear aligners in controlling orthodontic tooth movement a systematic review Angle Orthod   ossini , arrini S, eregibus A, et al Controlling orthodontic tooth movement with clear aligners An updated systematic review regarding efcacy and efciency J Aligner Orthod    Simon , eilig , Schware , et al orces and moments generated by removable thermoplastic aligners incisor torue, premolar dero tation, and molar distaliation Am J Orthod Dentofacial Orthop 

 rae CT, corray S, olce C, et al rthodontic tooth movement with clear aligners ISRN Dent   avera S, Castroorio T, arino , et al axillary molar distaliation with aligners in adult patients a multicenter retrospective study Prog Orthod   Simon , eilig , Schware , et al Treatment outcome and efcacy of an aligner techniue—regarding incisor torue, premolar derota tion and molar distaliation BMC Oral ealth   aher S Dr Sam Daher’s echniues for Class II Correction ith Inis align and Elastics httpssamaonawscomlearninvisalign docspxAACpdf  auette  xtraction treatment with nvisalign n Tuncay , ed he Inisalign Sstem ew alden uintessence ublishing Co   arino , Castroorio T, aher S, et al ffectiveness of composite attachments in controlling uppermolar movement with aligners J Clin Orthod   ome , eña , artíne , et al nitial force systems during bodily tooth movement with plastic aligners and composite attach ments a threedimensional nite element analysis Angle Orthod   Comba , arrini S, ossini , et al Threedimensional nite element analysis of uppercanine distaliation with clear aligners, composite attachments, and class  elastics J Clin Orthod   Solanoendoa , Sonnemberg , Solanoeina , et al ow effec tive is the nvisalign® system in expansion movement with x’ aligners Clin Oral Inestig   anson , Sathler , ernandes T, et al Correction of class  mal occlusion with class  elastics a systematic review Am J Orthod Dentofacial Orthop   ohamed , asha S, AlThomali  axillary molar distaliation with miniscrewsupported appliances in class  malocclusion a systematic review Angle Orthod   amada , uroda S, eguchi T, et al istal movement of maxillary molars using miniscrew anchorage in the buccal interradicular region Angle Orthod 

8

Aligners in Extraction Cases KENJI OJIMA, CHISATO DAN, and RAVINDRA NANDA

Introduction The demand for inconspicuous and natural-feeling orthodontic appliances has been rising over time. The introduction of the Invisalign system marked a signicant step forward in orthodontics in that it allowed for inconspicuous orthodontic correction using appliances with a natural feel. The original Invisalign system, however, came with serious limitations: the control of root movement was not possible and it was difcult to move large teeth over signicant distances.1-1 ecent advances in the uality of materials, the use of attachments, and the introduction of a new force system have epanded the range of applications of the Invisalign system from mild crowding to more difcult etraction cases.11-1 s is the case with all orthodontic procedures, one of the greatest sources of dissatisfaction among adult patients with aligner therapy is the long treatment time. This report describes the treatment of a patient with severe anterior crowding who was treated with Invisalign appliances after the etraction1- of her three remaining premolars. er lower left premolar had already been removed.  photobiomodulation device was used to possibly accelerate tooth movement.

Diagnosis and Treatment Plan hen this -year-old female presented at our clinic, she epressed a desire to correct her maillary anterior crowding and improve the aesthetic appearance of her smile. hile the patient’s facial prole was straight, both lips were slightly recessive with regard to the -line ig. .1. n intraoral eamination showed a class II molar relationship with a -mm overet, a -mm overbite, and coincident midlines. The arch-length discrepancy was 1 mm in the mailla and 1 mm in the mandible. Infralabioversion was noted for both upper canines and a marked buccal shift of the upper left second molar ig. .. ephalometric analysis indicated a skeletal class II relationship with a steep mandibular plane angle ig. .. The upper central incisors were slightly inclined lingually and the lower central incisors were inclined labially. The lateral gap in the mandibular head conrmed by her panoramic -ray did not impede mandibular function. There was evidence of slight regression in the periodontal tissue around the upper canines with no tooth mobility, the maimum pocket depth was  mm. ased on these observations, the patient was diagnosed as a skeletal class II case with infralabioversion of the

maillary canines and a steep mandibular plane angle. The treatment plan called for the retraction of both upper and lower incisors: 1. mm of movement was reuired in the mailla and 1. mm in the mandible. irst, the two upper rst premolars and lower right second premolar were etracted. er lower left second premolar had been removed in her early teens. Therefore, to allow for mesial movement, her upper left second molar and upper right third molar were etracted, too. ecause the patient epressed concern about the poor aesthetics of ed orthodontic appliances over a potentially long period of time, the decision was made to implement the Invisalign system in conunction with photobiomodulation rthoulse to possibly speed up treatment.1- linheck software was used to analye the location, angle, and need for the recontouring of the canine in relation to the nal desired occlusion ig. .. deuate incisor retraction in this class II malocclusion reuired the -mm distal movement of the upper rst molars and -mm mesial movement of the lower rst molars. ven after the etractions, there was insufcient space to move the maillary anterior teeth by premolar etraction alone. To create more space, the overepansion of the dental arches was reuired. Tooth movements were simulated on the linheck software ig. ., the amount of epansion reuired in each arch was estimated, the positions were planned, and the shapes of the reuired attachments were decided.

Treatment Progress Three third molars were removed ecept the upper left third molar before treatment. fter the etraction of the upper premolars and lower left rst premolar, aligner treatment was initiated. e used all the maillary teeth from rst molar to rst molar as anchorage for the distaliation of the second molars. In the mandible, we used all the teeth ecluding the canines and second premolars as anchorage for the mesial movement of the canines. ince the root of the lower right canine was angled outward, we moved the tooth simply by tipping the lower left canine was moved bodily along with its root. The distaliation of the upper second molars was completed in 1 weeks and distal movement of the upper rst molars was completed  weeks later. The closure of the lower etraction space continued during this period with mesial movement of the lower rst molars. fter  months of treatment, retraction movement of the upper canines was completed, with the incisors of the midline corrected. t this point, we recalculated the retraction 83

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Principles and Biomechanics of Aligner Treatment

A

B

C

D

E

F

Fig. 8.1 (A) Smile appearance of the patient. (B) Frontal picture at rest. (C) Three-quarter picture at rest. (D) Three-quarter smile appearance. () Prole smiling. (F) Prole at rest.

8 • Aligners in traction Cases

Fig. 8.2 nitial intraoral pictures.

A

B Fig. 8.3 (A) nitial orthopantomograph. (B) nitial lateral -ra.

85

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Principles and Biomechanics of Aligner Treatment

A

B

C

D

Fig. 8.4 ClinChec initial stage. (A) Frontal ie. (B) ight ie. (C) eft ie. (D) pper arch ie. () oer arch ie.

E

A

B Fig. 8.5 Schematic representation of ertical orthodontic tooth moement design in the frontal plane (A). Amount of ertical moements for upper canines and central incisors (B).

8 • Aligners in traction Cases

space for the maillary incisors by means of a panoramic -ray. ince the mandibular etraction spaces were closed, we could use all the teeth from second premolar to second premolar, including the canines, as anchorage for the mesial movement of the lower rst molars. The aligner margins were trimmed about  mm to accommodate direct-bonded hooks on the upper rst canines. ingual buttons were bonded to the distobuccal edges of the lower rst molars, and class II elastics . in,  o were prescribed to be worn  hours per day. To prevent the mesial tipping of the lower rst molars, vertical rectangular attachments were added to their mesiobuccal edges ig. .. Improvement was seen in the anteroposterior relationship after use of the class II elastics, and a class I relationship was established in the buccal segments. The net phase involved the retraction of the upper anterior teeth. fter

87

 months of treatment, the rst linheck phase was nished igs. . and .. The distaliation of the upper rst molars was complete, with space visible at the mesial edge of the upper left rst molar. The movement of the lower second premolars and canines had closed all the mandibular spaces. The shapes and positions of the attachments were modied for the renement phase. The crown positions were considered together with the root positions to decide the optimal conditions. fter  months of treatment, the aligner compatibility and the crown and root positions were all consistent with the computer-simulated predictions igs. . and .1. In the nal stages of renement, the occlusal contact of all upper and lower molars and a one-to-two-tooth occlusal relationship in the buccal segments were conrmed. oth the overbite and overet were 1 mm. fter a total 1 months of treatment, all buttons, hooks, and attachments were removed ig. .11. The patient was instructed to wear class II elastics at night for an additional 1 months.

Treatment Results

Fig. 8.6 Schematic representation of attachments and auiliaries required in etraction cases.

A

The patient’s chief complaint—the infralabioversion of the canines—was resolved, and the improvement in gingival esthetics yielded a pleasant smile igs. .1, .1, and .1. ue to the retraction of the maillary incisors, the upper lip was particularly natural and relaed, and the lips were positioned appropriately in relation to the -line.  class I molar relationship with symmetric arches was achieved, and all spaces were closed ig. .1. The physiologically correct overbite and overet were coincident with the dental and facial midlines.

B Fig. 8.7 (A) nitial smile esthetic analsis. (B) ClinChec simulation into the smile frame of the Digital Smile Design softare.

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Principles and Biomechanics of Aligner Treatment

Fig. 8.8 Treatment progresses in the frontal ie.

Fig. 8.9 Treatment progresses in the right ie.

8 • Aligners in traction Cases

Fig. 8.9, cont’d

Fig. 8.10 Treatment progresses in the occlusal ies. Continued

89

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Principles and Biomechanics of Aligner Treatment

Fig. 8.10, cont’d

Fig. 8.11 Posttreatment pictures.

8 • Aligners in traction Cases

91

A

B Fig. 8.12 Final smile esthetic analsis.

Fig. 8.13 (A) Final orthopantomograph. (B) Final lateral -ra.

The posttreatment protrusive and lateral movements of the mandible were smooth and linear. It is likely that the patient was using considerable force when biting in centric occlusion due to nervousness during the initial eamination. anoramic -rays conrmed that there was no change in the level of the alveolar bone, which remained stable and in a healthy condition. o signs of root resorption were noted.  cephalometric analysis indicated that the mandibular plane angle was slightly reduced. uperimpositions showed that while the upper and lower incisors were retruded, their aes were upright and closer to the norm.

class II elastics to enhance intermaillary anchorage. If an elastic is attached directly to an aligner, however, the plastic will separate from the teeth, making it more difcult to maintain control over mesial and distal tooth movements. In the case shown here, direct-bonded hooks were attached to the upper canines to allow the teeth to rotate both mesially and distally within the aligners, leaving a margin of more than  mm between the incisal edges and the aligners. ather than attach the elastics in the mandibular arch which was serving as anchorage directly to the aligners, they were attached to buttons on the buccal surfaces of the rst molars. This kept the aligners from lifting off the teeth, while vertical rectangular attachments on the mesial edges of the molars prevented mesial angulation. This avoided the tipping of the teeth adacent to the mandibular etraction sites. ecause the patient found the original predicted length of treatment unacceptable, rthoulse- was used in conunction with the aligners to possibly accelerate treatment time. espite the lack of published accounts of the effectiveness of this device beyond its application to fied appliances, the patient was instructed to use it for 1 minutes every evening. e were able to shorten the interval between aligner changes to  days, resulting in a remarkable reduction in the treatment time to ust

Discussion ligners appeal to adults because of their pleasing aesthetics and their ability to produce gradual tooth movements with light forces over the course of time. The focus of previous reports has been on cases that did not reuire etractions or those with only partial etractions. This is perhaps due more to the difculty of closing spaces without crown tipping than to the difculty of moving teeth. hen etraction spaces are closed with aligners, a bowing effect is often caused by the sagging of the plastic around the etraction sites. This effect can be prevented by using

92

Principles and Biomechanics of Aligner Treatment

Fig. 8.14 Posttreatment etraoral pictures.

8 • Aligners in traction Cases

93

Fig. 8.15 Final stage of the ClinChec renement.

Conclusion 1 months. The patient eperienced no discomfort from the rthoulse device or from the faster aligner changes. he finished treatment with no interferences in protrusive or lateral mandibular movements and no esthetic concerns.

ot only are aligners aesthetically pleasing to adult patients, but the ease with which they can be removed makes them etremely safe. In the future, aligners are likely to be used in more comple cases involving rotations, deep

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Principles and Biomechanics of Aligner Treatment

overbites, open bites, and unusual etractions. urther clinical investigations into the effects of accelerated tooth movement in such cases are reuired.

References 1. laskalic , oyd, . rthodontic treatment of a mildly crowded malocclusion using the Invisalign system. Austral Orthod J. 11:1-. . oyd , iller , laskalic . The Invisalign system in adult orthodontics: mild crowding and space closure cases. J Clin Orthod. :-1. . iancotti , i irolamo . Treatment of severe maillary crowding using Invisalign and ed appliances. J Clin Orthod. :-. . chupp , aubrich , ermens . . glichkeiten und grenen der schienentherapie in der kieferorthop. die Zahnmed. 1:11-1. . chupp , aubrich , eumann I. Treatment of anterior open bite with the Invisalign system. J Clin Orthod. 1:1-. . uarneri , liverio T, ilvestre I, et al. pen bite treatment using clear aligners. Angle Orthod. 1:1-1. . rieger , eiferth , arinello I, et al. Invisalign treatment in the anterior region. J Orofac Orthop. 1:-. . iancotti , arina . Treatment of collapsed arches using the Invisalign system. J Clin Orthod. 1:1-. . achan , haturvedi T. rthodontic management of buccally erupted ectopic canine with two case reports. Contemp Clin Dent. 1:1-1. 1. oyd . sthetic orthodontic treatment using the Invisalign appliance for moderate to comple malocclusions. J Dent Educ. :-. 11. astro£orio T, arino , aaro , et al. pper-incisor root control with Invisalign appliances. J Clin Orthod. 1:-1. 1. ahn , apf , athe , et al. Toruing an upper central incisor with aligners: acting forces and biomechanical principles. Eur J Orthod. 1:-1. 1. chupp , aubrich , eumann I. Invisalign treatment of patients with craniomandibular disorders. Int rthod. 1:-. 1. iller , corray , omack , et al.  comparison of treatment impacts between Invisalign aligner and ed appliance therapy during the rst week of treatment. Am J Orthod. 11:e1-. 1. oyd . omple orthodontic treatment using a new protocol for the Invisalign appliance. J Clin Orthod. 1:-. 1. laskalic , oyd . linical evolution of the Invisalign appliance. J Calif Dent Assoc. :-. 1. omack . our-premolar etraction treatment with Invisalign. J Clin Orthod. :-. 1. ima , an , ishiyama , et al. ccelerated etraction treatment with Invisalign. J Clin Orthod. 1:-.

1. owman , elena , paraga , et al. reative aduncts for clear aligners, part : etraction and interdisciplinary treatment. J Clin Orthod. 1:-. . iorillo , esta , rassi . pper canine etraction in adult cases with unusual malocclusions. J Clin Orthod. 1:1-11. 1. omíngue , elásue . ffect of low-level laser therapy on pain following activation of orthodontic nal archwires: a randomied controlled clinical trial. Photomed Laser Surg. 11:-. . au , antarci , haughnessy T, et al. hotobiomodulation accelerates orthodontic alignment in the early phase of treatment. Prog Orthod. 11:. . oas , onale-ima . ow-level light therapy of the eye and brain. Eye Brain. 11:-. . ells T, ong-iley T, eroeve , et al. itochondrial signal transduction in accelerated wound and retinal healing by nearinfrared light therapy. Mitochondrion. :-. . atanabe , ohensky , reeman T, et al. ypoic induction of  in the growth plate:  suppresses chondrocyte autophagy. J Cell Physiol 1:1-. . asha T, oureld , brahamse . ow-intensity laser irradiation at  nm stimulates transcription of genes involved in the electron transport chain. Photomed Laser Surg. 11:-. . akabayashi , amba , atsumoto , et al. ffect of irradiation by semiconductor laser on responses evoked in trigeminal caudal neurons by tooth pulp stimulation. Laser Surg Med. 11: -1. . awasaki , himiu . ffects of low-energy laser irradiation on bone remodeling during eperimental tooth movement in rats. Laser Surg Med. :-1. . antiwong ., de la uente , krenes , et al. hotobiomodulation accelerates orthodontic alignment in the early phase of treatment. Prog Orthod. 11:. . haughnessy T, antarci , au , et al. Intraoral photobiomodulation-induced orthodontic tooth alignment: a preliminary study. BMC Oral ealth. 11:. 1. ahas , amara , astegar-ari T. ecrowding of lower anterior segment with and without photobiomodulation: a single center, randomied clinical trial. Lasers Med Sci. 1:1-1. . arvalho-obato , arcia , asem , et al. Tooth movement in orthodontic treatment with low-level laser therapy: a systematic review of human and animal studies. Photomed Laser Surg. 1:-. . ima , an , umagai , et al. Invisalign treatment accelerated by photobiomodulation. J Clin Orthod. 1:-1. . ima , an , umagai , et al. pper molar distaliation with Invisalign treatment accelerated by photobiomodulation. J Clin Orthod. 11:-. . ima , an , umagai , et al. ccelerated etraction treatment with the Invisalign system and photobiomodulation. J Clin Orthod. :11-1.

9

Open-Bite Treatment with Aligners ALDO GIANCOTTI and GIANLUCA MAMPIERI

In recent years, aligners have shown to be an extraordinary and effective tool to correct open-bite cases. Such unexpected results make them the gold standard in the treatment of malocclusions characterized by vertical excess as in open-bite cases. Open bite is challenging to treat for its multifactorial etiology and for high incidence of relapse. he aim of this chapter is to show strategies and protocols for the treatment of anterior open bite by clear aligners.

Diagnosis of Anterior Open Bite Obviously, a proper diagnosis is essential in determining the appropriate corrective measures. It is possible to classify three types of open bite . ental . entoskeletal . Skeletal enerally, skeletal open bite reuires an orthosurgical approach. Instead, dental and dentoskeletal open-bite cases can be treated only by means of orthodontics. 

Biomechanics for Anterior Open-Bite Correction he biomechanics for anterior open-bite correction can be achieved either by extruding the incisors or intruding the posterior teeth, or by a combination of both. or the nonsurgical treatment of adult patients, some guidelines consider extraction and retraction for dental open-bite correction.  limited number of open-bite cases is suitable for such type of treatment. ental open-bite cases are mostly associated with the following characteristics n n n n n

ormal craniofacial pattern Incisor proclination ndererupted anterior teeth ittle or no gingival display on smile o more than  to  mm of upper incisor exposure at rest

If the anterior open bite depends only on tooth position, it is a relative open bite the biomechanics for the correction are easy, as follows n n

educing incisor proclination to produce a relative extrusion ure extrusion of incisors by extrusive attachments

he amount of incisal and gingival display needs to be assessed clinically prior to deciding if pure extrusion is desired from a smile esthetics point of view.

hen dentoskeletal factors are important in determining the cause of open bite, it is often caused by posterior dentoalveolar excess as well as by both downward and backward mandibular rotation.- hese types of open bite with a skeletal component caused by heredity andor supererupted posterior teeth reuire complex orthodontic treatments with active molar intrusion or even maor orthognathic surgery., In case of a dentoskeletal open bite, specic procedures have been designed to intrude posterior teeth or, at least, prevent molar eruption or extrusion in the attempt to reduce or control anterior facial height, especially during the growing age high-pull headgear, lower transpalatal arch with resin button, and posterior bite blocks. he introduction of temporary anchorage devices s has allowed an active intrusion of posterior teeth also in adult patients with a conseuent mandibular counterclockwise rotation and improvement of anterior open bite. xtraction of posterior teeth is another strategic approach to correct anterior open bite. Indeed, when indicated, molar extraction for caries or periodontal reasons could be highly effective in reducing facial height. orward movement of the terminal molars allows the mandible to hinge upward and forward. It has been postulated that  mm of intrusive vertical movement of the molars results in approximately  to  mm of bite closure by mandibular counterclockwise rotation. In the treatment of a dentoskeletal open-bite case, one shall observe some biomechanical principles. ny procedure meant to increase facial height by means of extrusion of posterior teeth must be avoided. eveling the arches is usually not to be considered appropriate, and the maintenance or creation of a curve of Spee would be desirable. urthermore, banding of second molars should be avoided to prevent any extrusion movement when molars are engaged on the arch wire. he abovementioned scenario can be easily avoided by using aligners, which allow for nonextrusion and represent a great advantage during open-bite treatment. his is why a number of researchers consider aligners as the gold standard.

Aligner Protocols for Open-Bite Treatment CLINCHECK SOFTWARE DESIGN he clear aligner treatment of open-bite cases depends on the type of malocclusion reuiring correction, and specic biomechanics have to be reuested by checking the appropriate 95

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Principles and Biomechanics of Aligner Treatment

boxes on the prescription form of the linheck software program to generate a predictable linheck plan. ental open bite, also known as relative open bite, clinically features excessive incisor proclination it can be treated only by reducing incisor proclination, producing a relative extrusion of anterior teeth. or these movements, attachments are not strictly reuired. he rst step consists of recovering the needed space in both arches. Space can be gained by arch expansion andor interproximal reduction I. he decision depends on the shape of the arches, tooth dimension, periodontal structure, and condition. ligners can easily modify the shape of the arch, and it is later possible to retract the incisors obtaining enough relative extrusion in mild open bite to solve the issue.

ATTACHMENTS IN OPEN-BITE CORRECTION In case of more severe dental open bites, anterior teeth extrusion can be strategic. ndoubtedly, extrusion is the

most difcult movement to reproduce with aligners. In such conditions, attachments play an important role to determine tooth extrusion. ttachments and anchorage optimized anterior extrusive attachments are automatically placed on the incisors by the software when pure extrusion of . mm or more is detected igs. . and .. onventional extrusion attachments have a rectangular shape with beveled edge toward the gingiva to allow for optimal pressure from the aligner and then achieve proper extrusion ig. .. hese attachments could be positioned also on the palatal surface if aesthetic reasons are a priority ig. .. Our experience suggests that the use of rectangular-shaped attachments with beveled edge toward the gingiva with the largest possible dimensions in relation to the incisor and most incisal possible allowed for an optimal control of relative and absolute incisor extrusion. nchorage attachments can have different shapes and dimensions, according to the type andor number of teeth involved.

Fig. 9.1 Optimized extrusive attachments of the Invisalign system.

Fig. 9.2 The anterior extrusive forces and reciprocal posterior intrusive forces work in synergy to correct the anterior open ite.

9 • OpenBite Treatment with Aligners

Fig. 9. ectangular shape attachments with eveled edge toward gingiva.

he dentoskeletal open-bite treatment complies to a more complex protocol to correct the malocclusion. Indeed, in this type of open bite, the skeletal structure shows a dentoalveolar posterior vertical excess, which is responsible for an increased lower facial height. or this reason, anterior tooth extrusion alone is not enough for correction, and one shall reduce the posterior vertical excess by dental intrusion. osterior dental intrusion results in a mandibular counterclockwise rotation mainly responsible for the open bite’s correction, which can be veried by nal cephalometric values. he anterior extrusive forces and reciprocal posterior intrusive forces work in synergy to close the anterior open bite see ig. .. he amount of posterior intrusion may range from less than . mm to a maximum of . mm. eyond the range of predictability for aligner movements, it may be necessary to use s. olar intrusion can be planned with aligners, and therefore we dene it as selective intrusion. he rst and second molars in the upper arch and rst molars and bicuspids in the lower arch are involved in the plan. he protocol related to attachment placement for anchorage usually envisages rectangular attachments on the molars and optimized ones on bicuspids. s for intrusion teeth, the ofcial Invisalign protocol does not include the use of attachments. Some experienced clinicians prefer to add occlusal rectangular attachments to increase intrusive components and thus increase effectiveness see ig. .. In more severe open-bite malocclusions, some clinicians prefer to stage posterior intrusion seuentially for a more predictable clinical outcome rst the maxillary second molars, then the rst molars, and then the second premolars. n important aspect to make predictable planning with aligners is to design an overcorrection. In the linheck we have to see the nal virtual occlusion with

97

Fig. 9. Palatal attachments and occlusal attachments on upper molars.

heavy anterior occlusal contacts and at least  mm of positive overbite. Our point of view concerning dental intrusion is that the most important effect of aligners in reducing posterior vertical excess is the bite-block effect, which is caused by two layers of aligner material between posterior teeth. It allows to effectively intrude posterior teeth, hence enabling subseuent autorotation of the mandible and reducing anterior facial height. he bite-block effect cannot be uantitatively priorly planned or displayed in the virtual digital setup by linheck, but we can routinely observe it clinically, especially in patients with a normal or larger mandible. In nal, to guarantee the maintenance of the result over time, it is essential to use ivera, the clear retainer produced by lign, because the posterior occlusal coverage will prevent the reeruption of posterior teeth.

Case Report 1 CASE SUMMAR  -year-old female patient presented a severe crowding, an unpleasant smile, as well as speech issues. linical extraoral examination showed a convex skeletal soft tissue prole due to a retrognathic mandible and incompetent lips at rest with mentalis and lip strain when the lips were pursed together. Intraoral examination evidenced class II canine and class I molar relationship on both sides, an anterior open bite, an excessive incisor proclination, and crowding on both arches ig. . able .. ephalometric analysis showed increased mandibular plane angle and increased lower anterior facial height see able . later. osterior maxillary dentoalveolar heights were dened as excessive ig. ..

9

Principles and Biomechanics of Aligner Treatment

Fig. 9.5 ase tudy  Initial clinical records.

9 • OpenBite Treatment with Aligners

99

PROBLEM LIST Table 9.1 ase tudy  Prolem ist Dimension

Seletal

Anteroposterior

n

onvex skeletal prole due to retrognathic mandile

n

lass II canine relationship

n

keletal class II

n

xcessive incisor proclination

n

Increased lower anterior facial height

n

Overite  mm

n

Increased mandiular plane angle

n

arrow upper arch

n

Increased maxillary posterior dentoalveolar heights

ertical

Dental

Transverse

n

Soft Tisse n

etrusive lower lip and chin

n

entalis muscle strain at rest

n

Incompetent lips

arrow upper and lower arch

Fig. 9.6 ase tudy  Pretreatment xray records.

TREATMENT OBECTIES

TREATMENT ALTERNATIES

he main treatment obectives were to close the anterior open bite, obtain class I canine relationships, correct the excessive incisor proclination, and improve smile arc able ..

he treatment alternatives consisted of the following

TREATMENT PLAN he treatment of dentoskeletal open bite reuires closure of anterior open bite through a combination of retraction and extrusion of the upper incisors and by intrusion of posterior maxillary dentition to enable subseuent autorotation of the mandible with an improvement of vertical and sagittal relationship. dditional treatment goals included leveling and aligning, optimizing the posterior occlusion, aiming at class I canine relationships, as well as ideal overbite and overet to improve the facial prole and obtain natural lip competence without mentalis strain.

. Orthosurgical treatment, including a eort I osteotomy with posterior maxillary impaction . onventional treatment with intrusion of the posterior maxillary dentition by using s for skeletal anchorage . xtraction treatment to reduce the vertical dimension while easing reduction of the anterior protrusion and mandibular crowding

TREATMENT SEUENCE orrection was achieved by means of the expansion of the upper arch by  mm that allowed tooth alignment and the correction of upper incisor proclination. In the lower arch, molar and premolar torue was corrected. he optimized attachments on cuspids and rst bicuspids in the upper arch were programmed to perform the anchorage unit necessary

1

Principles and Biomechanics of Aligner Treatment

Table 9. ase tudy  Treatment Oectives Dimension

Seletal

Anteroposterior

n

ertical

n

Dental

Soft Tisse

educe skeletal convexity with autorotation of the mandile

n

Improve class II canine relationship y autorotation of the mandile

n

Improve soft tissue prole

educe lower facial height and man diular plane angle y intruding the maxillary and mandiular posterior teeth and autorotating the mandile

n

Improve anterior overite and smile arc y intruding upper posterior teeth and maintaining the vertical position of the anterior teeth.

n

educe interlaial gap

n

Improve the prole y intruding maxillary dentoalveolar sites.

n

Achieve lip closure without activation of mentalis muscles

Transverse

n

xpand upper and lower arch

to achieve the reuired reduction of incisor proclination gaining enough space by means of I and arch expansion. Intrusion of posterior teeth determined by aligners would have favored a counterclockwise rotation of the mandible, thus promoting the anterior open-bite correction ig. .. Open-bite correction occurred by means of a rst phase of  aligners and a nishing stage including  aligners. In addition, the expansion, together with the correction of the tipping of cuspids and bicuspids, allowed for coordination of both arches and a slight mesial mandibular repositioning with an optimization of the occlusal relationships and correction of class II canine malocclusion.

TREATMENT RESULTS fter  months of therapy, treatment obectives set in the pretreatment plan were achieved. he anterior open bite had been completely closed, a proper overbite and overet

had been corrected, and class I canine relationship had been established ig. .. he extraoral records show an evident improvement in the patient’s smile. he pre- and posttreatment cephalometric showed  mm of intrusion of the upper molars determined by aligners. Such dental movement resulted in a mandibular counterclockwise rotation mainly responsible for the closure of the anterior open bite and the reduction of vertical skeletal values in the nal cephalometric assessment. aused by two layers of aligner material between the posterior teeth, molar intrusion is identied by clinicians as the bite-block effect and enables not only the correction of anterior open bite by means of the mandible’s counterclockwise rotation, but also an improvement of the class II relationship, thanks to mandibular repositioning ig. . able .. ollow-up after  months showed the great stability of the results ensured by means of ivera retainers. he use of aligners for retention provides a long-term posterior intrusive

Fig. 9.7 ase tudy  Pre and postlinheck superimposition.

9 • OpenBite Treatment with Aligners

Fig. 9. ase tudy  inal clinical records.

11

12

Principles and Biomechanics of Aligner Treatment

Fig. 9.9 ase tudy  Posttreatment xray records.

Table 9. ase tudy  ummary of ephalometric hanges Cephalometric orphologic Assessment

ean SD

Pretreatment

Posttreatment

axillary position A

° 6 .

°

°

andiular position B

° 6 .

°

°

agittal aw relation AB

° 6 .

°

°

axillary Inclination AP

° 6 .

°

°

andiular inclination O

° 6 .

°

°

ertical aw relation APO

° 6 .

°

°

axillary incisor inclination AP

° 6 .°

°

°

andiular incisor inclination oge

° 6 .°

°

°

 6 .





. 6 .





 6 .





° 6 .

°

°

SAGITTAL SKELETAL RELATIONS

ERTICAL SKELETAL RELATIONS

DENTOBASAL RELATIONS

andiular incisor compensation AP  DENTAL RELATIONS Overet  Overite  Interincisal angle 

force similar to that of posterior bite blocks, which is recommended for vertical control after anterior open-bite treatment.

Case Report  CASE SUMMAR  -year-old female presented with a mild skeletal class II, division  malocclusion, moderate lower and

mild upper crowding, moderate anterior open bite, a severely hyperdivergent skeletal pattern, and an unbalanced transverse relationship. linical examination indicated excessive lower facial height with a gummy smile and a typical long-face appearance ig. . able .. he patient had a -mm anterior open bite, with posterior occlusion only on the second molars. adiographic examination confirmed the vertical excess in the lower face ig. .. wo treatment options were presented surgical correction or aligner therapy with s.

9 • OpenBite Treatment with Aligners

Fig. 9.1 ase tudy  Initial clinical records.

1

1

Principles and Biomechanics of Aligner Treatment

PROBLEM LIST Table 9. ase tudy  Prolem ist Dimension

Seletal

Anteroposterior

n

ertical

Transverse

Dental

keletal class II division  malocclusion

Soft Tisse

n

Occlusal contacts only on the second molars

n

xcessive incisors proclination

n

oderate anterior open ite mm

n

etrusive lower lip and chin

n

Increased lower anterior facial height

n

ong face type

n

xcessive maxillary posterior growth

n

ummy smile

n

evere hyperdivergent pattern

n

entalis muscle strain at rest

n

Transversal skeletal deciency

n

oderate lower and mild upper crowding

n

nalanced occlusion relationships

Fig. 9.11 ase tudy  Pretreatment xray records.

TREATMENT OBECTIES he treatment aim was to close anterior open bite, correct excessive vertical facial height, obtain balanced occlusal contacts with a class I molar relationship, and improve patient’s smile able ..

he treatment also included the achievement of class I molar relationships, dental alignment and leveling, optimization of posterior transversal occlusion, as well as reaching ideal overbite and overet to improve the facial prole and smile arc. he pre- and postvirtual plan is shown in ig. .

TREATMENT PLAN

TREATMENT ALTERNATIES

he skeletal class II and the anterior open bite reuired correction by counterclockwise rotation of the mandible allowed by maxillary molar intrusion, without moving the vertical position of anterior teeth. Such upward and forward rotation would reduce facial height and improve vertical and sagittal relationships with proper dental torue and inclination.

he treatment alternatives consisted of the following . Invisalign therapy with intrusion of the posterior maxillary and mandibular dentition by using s as skeletal anchorage . Orthosurgical treatment including a eort I osteotomy with posterior maxillary impaction

9 • OpenBite Treatment with Aligners

15

Table 9. ase tudy  Treatment Oectives Dimension

Seletal

Anteroposterior

n

ertical

Transverse

Dental

Soft Tisse

Improve class II y counterclockwise mandiular rotation induced y molar intrusion

n

Improve class II molar relationship and incisor inclination y counterclockwise mandiular rotation induced y molar intrusion

n

Improve soft tissue prole

n

educe lower facial height maxillary downward clockwise rotation and hyperdivergent pattern y intruding upper posterior teeth and conse uent autorotation of the mandile

n

Improve anterior overite and smile arc y intruding upper posterior teeth and maintain ing the vertical position of the anterior teeth

n

Improve the prole y intruding maxillary dentoalveolar sites

n

xpand maxillary arch dentally

n

Improve alanced occlusion relationships y mandile autorotation

n

educe upper and lower crowding y contact points stripping

TREATMENT SEUENCE he patient chose the second option. osterior maxillary dentoalveolar intrusion for vertical correction was achieved by miniscrew mechanics. uccal  mm 3  mm Spider in miniscrews were placed mesially to each maxillary rst molar. n auxiliary . in 3 . in stainless steel sectional wire was placed on each side of the working cast coated at the ends with composite resin for easier placement in the mouth.  surgical hook was crimped at each rst molar and -g nickel titanium coil springs were tied from these to the s. o avoid the development of undesirable molar labial torue due to the force application on the buccal side only, the plan included use of upper and lower aligners to control it. he digital treatment plan was designed for alignment, I, and, if needed, tooth retrusion. Instead, posterior intrusion and anterior extrusion, or other vertical movements as in ase , were carefully avoided because the difference between  and aligner mechanics could lead to imperfect aligner t and inadeuate torue control ig. .. he aligner treatment consisted of  upper and lower aligners, plus  upper and lower renement aligners. ustomized, precise cuts of the aligners were designed on the linheck to accommodate the auxiliary wires, usually affecting two or three teeth on each side.

TREATMENT RESULTS

Fig. 9.12 ase tudy  Pre and postlinheck superimposition.

deuate intrusion and conseuent closing of open bite were achieved in  months with dental alignment and leveling ig. .. oals set in the pretreatment plan were totally reached after  months of therapy ig. . able .. he anterior open bite had been completely corrected, resulting in a proper overbite and overet.  class I molar relationship had been established. atient’s smile positively changed by improving vertical lower facial height and gummy smile. he values in the nal cephalometric assessment show a -mm intrusion of the upper molars and reduction of the vertical skeletal determined by aligners ig. . see able ..

16

Principles and Biomechanics of Aligner Treatment

Fig. 9.1 ase tudy  Invisalign with temporary anchorage devices for posterior intrusion.

Fig. 9.1 ase tudy  nd of posterior intrusion.

9 • OpenBite Treatment with Aligners

Fig. 9.15 ase tudy  inal clinical records.

17

1

Principles and Biomechanics of Aligner Treatment

Table 9. ase tudy  ummary of ephalometric hanges Cephalometric orphologic Assessment

ean SD

Pretreatment

Posttreatment

axillary position A

° 6 .

°

°

andiular position P

° 6 .

°

°

agittal aw relation AP

° 6 .

°

°

SAGITTAL SKELETAL RELATIONS

ERTICAL SKELETAL RELATIONS axillary inclination AP

° 6 .

°

°

andiular inclination O

° 6 .

 °

°

ertical aw relation APO DENTOBASAL RELATIONS

° 6 .

°

°

axillary incisor inclination AP

° 6 .

°

°

andiular incisor inclination O

 6 .

°

°

andiular incisor compensation AP 

 6 .





DENTAL RELATIONS Overet 

. 6 .





Overite 

 6 .





° 6 .

°

°

Interincisal angle 

Fig. 9.16 ase tudy  adiographic control and cephalometric superimposition.

References . gan , ields . Open bite a review of etiology and management. Pediatr Dent. -. . Subtelny , Sakuda . Open bite diagnosis and treatment. Am J Orthod. -. . angialosi . Skeletal morphologic features of anterior open bite. Am J Orthod. -. . opez-avito , allen , ittle , et al. nterior open-bite malocclusion a longitudinal -year post-retention evaluation of orthodontically treated patients. Am J Orthod. -. . anda S. atterns of vertical growth in the face. Am J Orthod Dentofacial Orthop. -. . ozza , ucedero , accetti , et al. arly orthodontic treatment of skeletal open bite malocclusion a systematic review. Angle Orthod. -. . etzenberger , uf S, ancherz . he compensatory mechanism in high angle malocclusions a comparison of subects in the mixed and permanent dentition. Angle Ortho. -.

. Sarver , eissman S. onsurgical treatment of open bite in nongrowing patients. Am J Orthod Dentofacial Orthop. -. . uhn . ontrol of anterior vertical dimension and proper selection of extraoral anchorage. Angle Orthod. -. . earson . reatment of vertical backward rotating type growth pattern patients in todays’ environment. eeting of Southern ssoc of Orthodontists, irmingham, , October -,  conrmed by personal communication. . ahoum I. ertical proportions a guide for prognosis and treatment in anterior open bite. Am J Orthod. -. . eilsen I. ertical malocclusions etiology, development, diagnosis and some aspects of treatment. Angle Orthod. -. . aralabakis , iagtzis S, outounzakis . ephalometric characteristics of open bite in adults a three-dimensional cephalometric evaluation. Int J Adult Orthod Orthognath Surg. -. . iancotti , arino , ampieri . se of clear aligners in open bite cases an unexpected treatment option. J Orthod. -. . ay S. Clear Aligner Technique. atavia, I uintessence ublishing .

10

Deep Bite LUIS HUANCA, SIMONE PARRINI, FRANCESCO GARINO, and TOMMASO CASTROFLORIO

Introduction Deep bite is dened as an increase of the overbite, and it is measured as vertical overlap of the incisors perpendicular to the occlusal plane.1,2 It can be divided into dentoalveolar origin (overeruption of frontal teeth) and skeletal origin (decreased lower face height, low mandibular plane angle). Deep bite prevalence varies from  to 1 depending on the threshold values applied, ethnic group, and gender.–  correlation between deep bite and sagittal molar mal occlusion was described. In particular, class II molar maloc clusion is signicantl associated with increased overbite compared with class I malocclusion. egarding treatment strategies in deep bite patients, there is not a complete consensus in the eisting literature.  21 review published b illet et al. assessed that it is not possible to provide an evidencebased guidance to rec ommend or discourage an tpe of orthodontic treatment to correct class II, division 2 malocclusion in children. s assessed b anda,1 it is possible to adopt three differ ent therapeutic strategies etrusion of posterior teeth, intru sion of upper andor lower incisors, and aring of anterior teeth (also known as relative intrusion). ll these effects can be obtained together depending on the clinical case.  using clear aligners instead of ed appliance, the orthodontist can start correcting the overbite on both arches from the beginning rather than wait a few months to bond the lower arch after the upper teeth have been aredintruded to open the bite. he alternative would be to bond bite ramps since the beginning, but these ma prove uncomfortable for patients and reuire adustments and etra cleanup at some point in the future.

Leveling of the Curve of Spee  deep curve of pee is often associated with severe anterior deep bite.  etruding posterior teeth, mainl premolars, and intruding anterior teeth, it is possible to atten the arches and achieve an ideal overbite.1 It is difcult to dene the net contribution of molar and premolar etrusion versus canine and incisor intrusion to the overall curve of pee attening, as the act as a recipro cal source of anchorage. henever attempting to etrude the premolars, canines and incisors will serve as an anchor age unit, and the will pa the price of a most welcome in trusion side effect. n the contrar, ever time clinicians would love to achieve intrusion of the anterior teeth, the premolars represent the primar source of anchorage, and the ma etrude a benecial side effect of anterior intru sion. ven if, b using clear aligners and an attentive plani

cation of tooth movements, clinicians ma be persuaded that the can achieve specic tooth movements (i.e., intru sion of the anteriors onletrusion of the posteriors onl), the should be aware that ewton’s third law of phsics (action and reaction) plas an important role in distin guishing the real world from the virtual onscreen world of setup, where the laws of phsics are often violated. It is a common belief that deep bite correction and curve of pee attening is easier to achieve in growing patients, as etrusion of molars and premolars can be supported b vertical growth while grow is still happening. n the contrar, curve of pee correction in adults ma be much harder, as the orthodontist cannot hope in an inuence or help from the vertical skeletal dimension. ur thermore, curve of pee tends to deepen with aging, with supererupted lower incisors and canines that ma also show lingual inclination (upper incisors can also show lingual incli nation as a conseuence). his becomes clinicall evident in a twostep mandibular occlusal plane with a net step between the rst premolars and canines. cessive wearing of the inci sal edges ma also be evident in such circumstances. hile planning deep bite correction in an adult, the orthodontist should also plan an eventual restorative treatment that is needed to reestablish the proper crown anatom. lign echnolog has created a proprietar protocol for deep bite correction called Invisalign . his protocol in volves incisor and canine intrusion through a combination of intrusion forces eerted b the aligners on the occlusal edge of the teeth and a pressure area on the lingual surface (igs. 1.1 and 1.2). his combination of force sstems eerts a nal intrusive force that is supposed to be parallel to the tooth long ais. o achieve the desired intrusion on the anterior teeth, an adeuate anchorage should be pro vided in the premolar and molar area.  retention attach ments have been specicall designed for premolars, and the ma serve as pure anchorage attachments or as active etrusion attachments in case of etrusion of the premo lars. oth movement of anterior intrusion and posterior etrusion are automaticall activated if the threshold of movement is more than . mm. olar anchorage should be provided with conventional attachments (rectangular and horiontal) to counteract the occlusal movement of the aligner determined b the anterior intrusion design. linicians working with other clear aligner sstems than Invisalign, or those who feel the need for alternative ap proaches even when using Invisalign aligners, ma create a similar protocol using standard attachments and a person alied staging of intrusion. ingival beveled attachments ma be used as an alterna tive to  retention attachments on premolars to achieve retention and etrusion. hen planning etrusion, it is 109

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Fig. 10.1 Schematic representation of the optimized bite ramps designed by Align Technology (San José, CA, SA and embedded into aligners They change shape and positioning along the treatment to proide optimal spport to loer incisors at eery stage of treatment

Pressure area Aligner forces

Resultant force

Fig. 10.2 Schematic representation of pressre areas designed by Align Technology (San José, CA, SA and incorporated into the aligner to redirect the intrsie force along the long ais of the incisor

useful to ask for a slower etrusion rate (e.g., .1 mm per stage instead of the classic .2 mm) to avoid lack of track ing within the aligner b respecting the phsiologic toler ance of the periodontal ligament. ome clinicians recommend a superiorl conve (reverse) curve of pee as nal obective of the alternative. hile this is not the real clinical goal, the assumption behind this pre scription is that the elasticit and resilience of the plastic material will ver unlikel allow a full epression of the prescribed movement.  the wa the lack of epression of certain movements can be compensated b this reuested hpercorrection, that is the aligner euivalent of the re verse curve ii wires.1 he clinician who has the feeling that the hpercorrection is reall happening ma alwas stop the use of the aligners to avoid unwanted side effects. urve of pee correction should alwas begin with lower incisor proclination to obtain a relative intrusion and start to recover the space reuired during the real intrusion movement. ince the epression of the lingual root torue information on lower incisors has not et been investigated, it can be useful to prescribe etra lingual root torue. gain, it is important to remember that interproimal spac ing ma help the intrusion movements.  paper b iu and u11 eplained how force changes as a conseuence of different intrusion strategies for deep bite correction with clear aligners. ith the same activation (.2 mm of intrusion) and rectangular attachments placed

on the premolars and rst molars, the canines eperienced the largest intrusive force when intruded alone. hen ap pling contemporar intrusion of canines and incisors, the canines received a larger intrusive force than incisors. he incisors received similar forces of intrusion if intruded alone or together with canines. irst premolars eperienced the largest etrusive forces when all anterior teeth were in truded. trusion forces were eerted also on canines and lateral incisors when differential staging for intrusion of canines and incisors was used. It is not surprising that the intrusive force eerted b clear aligners is higher when less elements are involved, and it is partiall lost when multiple elements are intruded at the same time. he incisors show an overall scarce tendenc to feel intrusion forces. his ma lead to the clinical suggestion of a staggered approach, al ternating canine and incisor intrusion to eert higher and more specic forces on canines and incisors. herefore, a clinical suggestion in prescribing anterior intrusion with an clear aligner sstem could consider the following 1. Intrusion from canine to canine at a rate of .1 mm per stage (rst create an etra space of . mm to hold until the movement has been completed) 2. oriontal rectangular beveled gingival attachments on lower bicuspids those attachments should be  mm wide, 1. mm high, 1.2 mm thick at the gingival mar gin, and tapered to .2 mm thickness at the occlusal margin . oriontal rectangular beveled occlusal attachments on lower canines those attachments should be  mm wide, 1. mm high, 1.2 mm thick at the occlusal margin, and tapered to .2 mm at the gingival margin . oriontal rectangular attachments on molars to increase anchorage . lternate intrusion of canines and incisors . lace the attachments occlusall avoiding an interarch interferences

Leveling the Upper Incisors linical observation of patient face and smile and gingival displa guide the clinician in the choice of how to correct an ecessive overbite.12 In fact, in man clinical cases, a pure lower posterior etrusioncurve of pee attening ma not be the best option, but the mechanics in the lower arch should be accompanied b vertical movements on the upper anteriors. During treatment planning with aligner orthodontics, it is possible to prescribe a selective upper or lower incisor intrusion. It is not surprising that when tring to correct an eces sive overbite, the upper smile arch needs special care, as Dr. David arver taught to the whole profession. he intrusion of the upper incisors should be limited to preserve conveit of the smile and enough crown eposure to preserve a outhful smile while aging. pper incisors and canines ma be intruded b relative intrusion (i.e., b providing vestibular crown torue, some intrusion happens as a geometric conseuence of this move ment). o allow a full epression of this movement, it is strongl suggested to prescribe an etra lingual root torue. ower idge (lign echnolog, an osè, , ) at the gingival third of the crown ma also help in achieving

10 • eep Bite

labial crown torue. imon et al.1 demonstrated that even a buccal attachment on upper incisors could provide lingual root torue control. pper relative intrusion and incisor crown vestibularia tion is often needed in those adults who have a ver deep curve of pee, where the correction starts with labial move ment of the lower incisors. nough clearance (anterior overet with no contacts) should be provided to avoid poste rior disclusion due to hard collisions among upper and lower incisors due to occlusal interferences. nce achievement of the correct amount of relative intrusion occurs, pure intrusion can be applied. ith lign echnolog  protocol, when the intrusion reuest overpasses the .mm threshold, a lingual pressure area will be added to enhance the parallelism of the nal vector of intrusive force to the long ais of the tooth. ite ramps ma be added on the lingual part of the teeth to help during deep bite correction (see ig. 1.1). he are optimied—in other words, the can change shape and position during the different stages of treatment to keep contact with the lower incisors as a conseuence of upper incisor buccal crown torue (the get longer while the up per incisor crowns get ared). hen bite ramps are present, no palatal pressure areas can be added at the same time on the same tooth as the two features need some space on the lingual surfaces of incisors andor canines. here are some claims of a possible intrusive effect of bite ramps on upper incisors because of the imposed precontact. hile this claim ma answer a logical thought, it is important to re member that we pass most of the time in a discluded posi tion of the aw respecting our vertical freewa space. s a conseuence, patients bite over the bite ramps for a few seconds per da onl when swallowing, thus the real effect of bite ramps as booster of upper intrusion is uestionable. he wa bite ramps keep the aws constantl discluded is the same principle of man functional appliances, whose main obective is to enhance lower posterior etrusion b providing an anterior precontact. In this sense, bite ramps, supported b class II elastics, ma favor lower posterior teeth etrusion, especiall in growing patients. It is impor tant to notice that, with aligners, elastics are recommended to boost posterior etrusion, as the clear aligner is other wise creating a selflimiting barrier that can limit posterior etrusion. n the contrar with functional appliances, where the molars and premolars are left free to erupt, the posterior vertical correction happens naturall. eviewing the eisting literature about deep bite correc tion with aligners, hosravi et al.1 showed that in their sample of  deep bite patients treated with Invisalign aligners, the cephalometric analses performed to deter mine the mechanism b which the Invisalign appliance corrects deep bites suggest that proclination of mandibular incisors, along with intrusion of maillar incisors and etrusion of mandibular molars, is the primar source of deep bite correction with the Invisalign appliance.

Case Report 1 he patient presented at the age of 1 with a severe over bite, a deep curve of pee associated with lower crowding, and important lingualiation of the lower right canine (igs. 1. and 1.). is chief complaint was to avoid the

Fig. 10.3 nitial etraoral photos

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Principles and Biomechanics of Aligner Treatment

Fig. 10.4 nitial intraoral photos

traumatism he felt ever time he bit on the palatal mucosa close to the retroincisal papilla. s visible on tracings, he had a slight class II while the skeletal vertical dimension was not as severel reduced as the dental deep bite could have suggested. e had agenesis of the second lower premolars (ig. 1.). he treatment plan included the preservation of the lower second deciduous molars and eventual implant substitution of second premolars later in life. he treatment lasted 2 months with four sets of correc tions of decreasing length. he length of the treatment was

due to the severe curve of pee that needed a big effort to be attened. ligner change was planned ever  das from the beginning. he curve of pee attening was obtained rst with proclination of the lower incisor and relative in trusion, then space was created mesial and distal to lower incisors and canines, and maintained while performing in trusion with staggered alternate movements (frog protocol) (ig. 1.). nchorage attachments (rectangular horion tal) were used on the premolars but also on the canines, as at moments the served as anchorage unit for incisor intrusion (ig. 1.).

10 • eep Bite

A

C

113

B

Fig. 10.5 (A nitial orthopantomography (B nitial lateral -ray (C nitial tracing

Fig. 10.6 Treatment stages scheme illstrating the frog protocol in hich alternate intrsion moements of canines and incisors are planned n the  ais teeth are displayed, hile on the  ais treatment stages are displayed eery stage corresponds to e aligners The blue lines indicate actie moements, brown lines indicate oercorrection stages Red arrows down indicate hen attachments shold be placed, hile red arrows p indicate hen attachments shold be remoed

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A

B Fig. 10.7 (A nitial cre of Spee (B inal cre of Spee

he deep bite was full corrected on the lower arch (igs. 1., 1., and 1.1), as superimpositions on the ellaasion plane (ig. 1.11) show an unaltered verti cal position of the upper incisors. n important intrusion of the lower incisors is associated with a slight advance ment of the  point of the mandible probabl due to the use of class II elastics.

Due to the presence of the lower deciduous molars, the patient ended into a canine class I and molar headtohead relationship. he lower right deciduous molar responded perfectl to the therap, while the left one was uite unre sponsive to vertical movement, and a slight underbite was left at this level. he patient’s chief complaint of retroinci sal traumatism was full achieved.

Fig. 10.8 inal etraoral photos

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115

Fig. 10.9 inal intraoral photos

Case Report 2 n 1earold male patient presented with molar class II malocclusion, skeletal class II, low mandibular plane angle, deep bite with an increased curve of pee, and crowding in the incisor area (igs. 1.12 and 1.1). atient’s main concern was the deep overbite and crowding in the upper incisors area. he treatment plan was designed to obtain bodil distal movements of upper molars, premolars, and canines to achieve a dental molar and canine class I.

  seuential distaliation protocol was applied together with the use of class II elastics (.1 in, . o) during the distaliation process (see hapter ). ttachments were placed on all distaliing teeth to con trol bodil distal movements (igs. 1.1 and 1.1). he deep bite was corrected mainl through intrusion of the lower anterior teeth, using the  protocol, and the presence of bite ramps on the upper incisors. he amount of lower intrusion in the incisor area was .1 mm, and to reinforce the posterior anchorage, attach ments were placed on bicuspids.

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A

B

Fig. 10.10 (A inal orthopantomography (B inal lateral -ray (C inal tracing

C

Fig. 10.11 Tracing sperimposition

 set of  Invisalign aligners was produced to perform the distaliation movements on the upper arch and to cor rect the lower curve of pee. ligner change was planned ever 2 weeks at the beginning of treatment, ever 1 das after  months of treatment, then ever  das after  months of treatment. During the distaliation phase, the patient was instructed to wear class II elastics (.2 in, . o) bilaterall to reinforce anterior anchorage while distaliing premolars. o anchor class II elastics, hooks were planned on upper canines while buccal tubes were bonded on the lower rst molars. n additional set of 1 upper and lower aligners was reuested to nalie the treatment obtaining good nal intercuspation in the molar and bicuspid areas and a nal overet of 2 mm. he treatment was concluded with bilateral class I molar and canine relationship, ecellent upper and lower align ment, and good leveling of the curve of pee (igs. 1.1, 1.1, and 1.1). he total treatment duration was 2 months.

10 • eep Bite

Fig. 10.12 nitial etraoral photos

Fig. 10.13 nitial intraoral photos

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B Fig. 10.14 (A nitial orthopantomography (B nitial lateral -ray

Fig. 10.15 n progress intraoral photos olar tbes ere sed on loer rst molars for class  elastic anchorage

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Fig. 10.16 inal etraoral photos

Fig. 10.17 inal intraoral photos

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B Fig. 10.18 (A inal orthopantomography (B inal lateral -ray

References 1. anda . Biomechanics and Esthetic Strategies in Clinical Orthodontics. aunders 2. 2. Dan , reuter , ifakakis I, et al. tabilit and relapse after orth odontic treatment of deep bite cases—a longterm followup stud. Eur J Orthod. 21222. . ielsen I. ertical malocclusions etiolog, development, diagnosis and some aspects of treatment. Angle Orthod. 111()22. . u , Dücker , ritsch , et al. cclusal status and prevalence of occlusal malocclusion traits among earold schoolchildren. Eur J Orthod. 2122. . roft r , ields , arver D. Contemporary Orthodontics. th ed. lsevier 21. . ausche , uck , arer . revalence of malocclusions in the earl mied dentition and orthodontic treatment need. Eur J Orthod. 22()22. . illett D, unningham , ’rien D, et al. rthodontic treatment for deep bite and retroclined upper front teeth in children. Cochrane Database Syst Rev. 21(2)D2.

. ans , nlow D. Essential of Facial roth. eedham ress 1. . arshall D, aspersen , ardinger , et al. Development of the curve of pee. Am J Orthod Dentofac Orthop. 21() 2. 1. lifford , rr , urden D. he effects of increasing the reverse curve of pee in a lower archwire eamined using a dnamic photoelastic gelatine model. Eur J Orthod. 121()21222. 11. iu , u . orce changes associated with different intrusion strategies for deepbite correction b clear aligners. Angle Orthod. 21()1. 12. arver D. he importance of incisor positioning in the esthetic smile the smile arc. Am J Orthod Dentofac Orthop. 2112(2) 111. 1. imon , eilig , chware , et al. reatment outcome and efcac of an aligner techniue—regarding incisor torue, premolar derotation and molar distaliation. BC Oral ealth. 211. 1. hosravi , ohanim , uoel , et al. anagement of overbite with the Invisalign appliance. Am J Orthod Dentofac Orthop. 2111()1,e2.

11

Interceptive Orthodontics with Aligners TOMMASO CASTROFLORIO, SERENA RAVERA, and FRANCESCO GARINO

Introduction Early orthodontic treatment is still a debated argument. According to the existing literature, the usefulness of interceptive orthodontics is controversial even if many sagittal, vertical, and transversal malocclusions are clearly visible and diagnosed in the early mixed dentition.1 Some authors recommend interceptive treatment because many malocclusions tend to worsen with age.2 Some other studies have underlined that orthodontic treatment during the pubertal phase may positively inuence malocclusion improvements, contributing to the stability of nal results.3 However, a recent review stated that removable functional appliances can produce short-term good dentoalveolar effects rather than skeletal improvements.4 Furthermore, a recent update of a Cochrane review claimed that on the basis of low to moderate quality evidence, providing early orthodontic treatment for children with prominent upper front teeth is more effective for reducing the incidence of incisal trauma than providing one course of orthodontic treatment in adolescence. There appear to be no other advantages of providing early treatment when compared to late treatment.5 The reduction of upper incisor proclination should not be underestimated because the smile appearance is important among overall esthetics for adolescents as well as for children younger than 10 years of age. Correcting smile alterations, even in young children, may be fundamental in preventing bullying or teasing from others and in improving the quality of social interactions, preserving healthy psychologic development.6 Interceptive orthodontics could be also recommended when detecting bad oral habits as atypical swallowing and mouth breathing have been found to be strictly related to malocclusion worsening.7 Moreover, early orthodontic treatment mainly consisting in maxillary expansion and mandibular advancement has been indicated to treat pediatric sleep apnea patients.8 The controversial results deriving from the existing literature in terms of effectiveness of interceptive orthodontics are mainly related to the lack of specic indicators of the right biologic timing of intervention. Although no skeletal maturity indicator may be considered to have a full diagnostic reliability in the identication of the maxillary growth peak and of the pubertal growth spurt or mandibular growth peak, treatment timing according to available indicators (mainly hand and wrist maturation [HWM] and cervical vertebral maturation [CVM] methods) has yielded more favorable outcomes. The use of the HWM or CVM methods (or others) may still be recommended for treatment planning, even though large individual responsiveness and dentoalveolar compensations have been reported, even in pubertal patients.9

In this chapter, we focus on clear aligner interceptive orthodontics of class II retrognathic patients and of patients with maxillary constrictions, highlighting the recommendations for case selection and treatment planning, showing some case reports.

Maxillary Expansion Transverse maxillary constriction and maxillary crowding in children are problems commonly encountered and treated by orthodontists.10-12 Interceptive orthodontics with maxillary expansion (ME) is one of the treatment options recommended for children with transverse deciencies with the intent to increase the transverse widths of the maxilla. This approach is particularly important in children with posterior crossbite because it has been shown to determine abnormal chewing patterns and the development of skeletal asymmetries.13,14 Expansion is especially desirable for young class II division I patients who have constricted maxillae because the transverse deciency does not self-correct between the deciduous, mixed, and permanent dentitions.15 Increasing maxillary arch width could improve class II with retrognathic mandible, inducing a spontaneous forward repositioning of the mandible, even if there is still a lack of general consensus on this issue.16,17 Maxillary arches are also expanded routinely to solve anterior crowding and improve the smile esthetics of kids.6,18-20 Crowding of the permanent incisors, with associated rotations and/or anterior crossbite, is commonly observed during eruption of the permanent lateral incisors. The rationale of interceptive treatment in the early mixed dentition is to generate adequate space for the spontaneous alignment of the permanent upper lateral incisors prior to complete eruption. When crowding is limited to a few millimeters, normal growth could provide adequate space, but when the palate is narrow and the crowding exceeds this amount, maxillary expansion could represent an effective procedure.21 As stated by Rosa et al.,21 when planning interceptive rapid maxillary expansion (RME) in absence of posterior crossbite, the clinician should consider that rst permanent molars are often tilted buccally, and a further buccal movement will produce periodontal problems and posterior occlusal interferences related to the deepening of the Wilson curve. Furthermore, the amount of anterior expansion could not be enough to solve the anterior crowding. Ideally the expansion should be limited to the anterior region of the arch, while permanent molars should move in a palatal direction. Considering these aspects, maxillary expansion by anchorage on deciduous teeth has been proposed. The benet 121

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Principles and Biomechanics of Aligner Treatment

of anchoring the expander on second deciduous molars and deciduous canines was the gain of 5 to 6 mm in upper arch perimeter. The gained space is sufcient to solve anterior crowding without tilting buccally permanent molars. However, those teeth spontaneously follow the buccal movement of deciduous molars for about 60% of their movement. When thinking about differences between several activation protocols for maxillary expansion, a recent systematic review22 helps us to understand some outcomes comparing slow maxillary expansion (SME) and RME; there is moderate evidence showing that maxillary transverse diameters increase signicantly within both groups in the shortterm,23 but SME protocol is more predictive of bodily upper molar movement, while the RME protocol produces more tipping movement in the molar region.24 RME uses heavier interrupted forces to maximize orthopedic effects, and slow palatal expansion uses lighter continuous forces to move teeth at rates purported to be more physiologic.11 Aligners use intermittent light forces to move teeth, and intermittent forces are able to produce orthodontic tooth movement with less cell damage in the periodontium.25 Since it has been stated that light, continuous forces seem to be perceived as intermittent forces by the periodontium due to its viscoelastic nature,26 the expansion produced by aligners could be described as SME. A clear aligner maxillary expansion protocol has been recently proposed (Invisalign First, Align Technology, Inc., San José, CA, USA). Aligners could overcome some of the limitations presented by palatal expander particularly in non-crossbite cases. With these appliances, it is possible to control the movement of all the teeth in the maxillary arch, aiming to produce an initial alignment and leveling while expanding the arch. Aligners can be really helpful in controlling maxillary rst molars not only on the frontal plane but on the horizontal and sagittal planes, too, avoiding all the issues mentioned earlier in relation to potential periodontal problems. Furthermore, aligners can control the expansion limited to the anterior region of the arch to generate adequate space for the spontaneous alignment of the permanent upper lateral incisors prior to complete eruption. Because of the short clinical crowns of deciduous teeth, specic attachment shapes were designed to increase aligner retention and control the tipping movement to obtain torque compensation and avoid a deepening of the curve of Wilson (Fig. 11.1). Regarding staging, two options are available at the moment: (1) Permanent molars (if required by the treatment plan) will be moved buccally, using the rest of the arch as anchorage, and only once they have reached their nal position will the deciduous molars and canines be moved buccally using permanent molars and incisors as anchorage units. (2) Permanent molars and deciduous teeth are moved buccally in a simultaneous manner (Fig. 11.2). Because of the geometry of the aligners, their distal portions are not stiff enough to support a predictable buccal movement of so many teeth at the same time, making this staging not the rst-line treatment option. Timing is another important factor to be considered. The best timing to expand maxillary arch is during the early mixed dentition, before upper permanent lateral incisor eruption and after the permanent molars are fully erupted and in occlusion. This timing is favorable as the midpalatal suture is more immature.27 In young children, up to age 8 or 9 years, little force is needed. Up to that age, a transpalatal

Fig. 11.1 Invisalign First optimized attachments for maxillary expansion.

F

F

Fig. 11.2 Invisalign First maxillary expansion protocol staging.

lingual arch releasing light continuous forces for dental expansion also will open the midpalatal suture.28 Therefore, it can be assumed that intermittent forces released by aligners can be sufcient in children up to 8 or 9 years of age to act on the transversal dimension of the maxilla. A recent clinical trial conducted at the University of Torino (Torino, Italy) in which clear aligners and RPE effects in patients with maxillary constriction were measured on digital models, suggests that: n

n

n

A signicant increase in palatal volume, so as in the other parameters, has been proved for both treatments. The RPE slightly outperform clear aligners considering all the parameters tested. The compliance and the clinical condition could affect the potential results achievable by the clear aligners.

The Clear Aligners demonstrated a reasonable ability to achieve palatal expansion. Since the materials have improved over the last years, so as the academic efforts to better understand the potential of CAT, substantial advances can be expected in the near future.58

Expansion Case Reports For the following case reports, three-dimensional (3D) evaluation of upper arch and palate morphology was performed according to a previous study by Bizzarro et al.29 The upper arches were scanned using a 3D scanner (iTero Element). The 3D data were imported to a reverse modeling software package called Geomagic Studio (3D Systems, Inc).30 Intermolar, intersecond deciduous molar, and intercanine transverse widths at the cusps and gingival levels were measured (Fig. 11.3), as well as anterior and posterior palatal depths at the cusp level, palatal surface area (Fig. 11.4), and volume (Fig. 11.5).

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123

CC

CG

cC

cG MC

MG

GP Line 7

DP

Fig. 11.3 CG intercanine widths assessed at gingival level, CC intercanine widths assessed at cusp level, cG inter-E widths assessed at gingival level, cC inter-E widths assessed at cusp level, MG intermolar widths assessed at gingival level, MC intermolar widths assessed at cusp level.

GP MSP DP

Fig. 11.5 The palatal surface area was dened by the median sagittal (MSP), distal (DP), and gingival (GP) planes as boundaries of the palate. The distal plane (DP) passed through two points at the distal of the rst upper permanent molars.

was planned within the ClinCheck, along with alignment of central and lateral incisors. The patient was instructed to change the aligners every week, and control examinations were planned every 6 weeks. Pre- and postexpansion scan screenshots are shown in Fig. 11.6. The expansion phase lasted 8 months. The palatal volume increased from 3843.54 mm3 to 5330.89 mm3 due not only to the vestibular dental tipping but also increased interarch widths measured at both gingival and a cuspal levels. Quantitative evaluations of intraarch widths, palatal areas, and volumes for this case are summarized in Table 11.1 as Case 1 reports.

CASE STUDY 2

Fig. 11.4 The anterior and posterior depth of the palatal vault is dened as the vertical distance from the contact line between the cusp of the right and left canine and mesiopalatal cusp tips of the right and left rst molars to the palatal vault, respectively. The palatal volume was dened by the median sagittal, distal, and gingival planes as boundaries of the palate. The distal plane (DP) passed through two points at the distal of the rst upper permanent molars. The gingival plane (GP) was created by intersecting the distal and median sagittal planes (MSP) through the center of incisive papilla, which is considered a stable point structure.31 All planes were perpendicular to each other.

Consider a 9-year-old girl with upper anterior crowding and deep bite. Invisalign First was adopted, and sequential expansion of molars rst and then deciduous teeth was planned within the ClinCheck, along with the alignment of central and lateral incisors. The patient was instructed to change the aligners every week and control examinations were planned every 2 months. Pre- and postexpansion scan screenshots are shown in Fig. 11.7. The expansion phase lasted 6 months. The palatal volume increased from 4342.64 mm3 to 6948.68 mm3 due not only to the vestibular dental tipping but also increased interarch widths measured at both a gingival and a cuspal level. Quantitative evaluations of intraarch widths, palatal areas, and volumes for this case are summarized in Table 11.1 as Case 2 reports.

CASE STUDY 1 Consider an 8-year-old boy with upper central incisor protrusion, mild upper anterior crowding, and palatal tipping of deciduous teeth. Invisalign First was adopted, and sequential expansion of molars rst and then deciduous teeth

Class II Malocclusion Class II malocclusion is the most frequent skeletal sagittal disharmonies in the white population.32 Diagnosis using

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Principles and Biomechanics of Aligner Treatment

A A

B Fig. 11.7 Case 2 pre- (A) and post (B) therapy scans of the maxillary arch.

B Fig. 11.6 Case 1 pre- (A) and post (B) therapy scans of the maxillary arch.

Table 11.1 Pre- and post-treatment volumetric and linear measurements obtained in the reported cases. A mm2

V mm3

CG mm

CC mm

cG mm

cC mm

MG mm

MC mm

Case 1 pre

1105.91

3843.54

22.6

29.1

28.2

32.2

32.6

36.8

Case 1 post

1316.57

5330.89

27.6

36.7

33.4

39.7

36

42.1

Case 2 pre

1111.67

4342.64

24.4

32.1

29.8

34.5

35.1

39.7

Case 2 post

1478.69

6948.68

26.3

37.5

32.9

39.5

35.4

42.1

A, Palatal surface area; CC, intercanine widths assessed at cusp level; cC, inter-E widths assessed at cusp level; CG, intercanine widths assessed at gingival level; cG, inter-E widths assessed at gingival level; MC, intermolar widths assessed at cusp level; MG, intermolar widths assessed at gingival level; V, palatal volume.

cephalometric tracings may highlight different dental or skeletal components of class II malocclusion: upper incisor proclination, lower incisor retroclination, mandibular retrognathia, ipomandibulia, maxillary protrusion, ipermaxillia, or different combinations of these components.

Mandible retrusion has been found to be the main factor in most basal class II malocclusions.33,34 One orthopedic approach developed to treat mandibular skeletal retrusion in growing patients is the forward repositioning of the mandible,35,36 even if a general consensus about the efcacy and

11 • Interceptive Orthodontics with Aligners

efciency of this approach is still missing36 37 (probably for inconsistent evidence of homogeneous interventions,37 38 wide variations in individual responsiveness,39 and different timings in orthodontic intervention9), and undergoing mandibular advancement in specic growth phases has been reported to have a key role in successful treatment outcomes. Several studies have shown that the optimal biologic timing for the achievement of skeletal effects is the circumpubertal growth period,40-43 when the greater mandibular growth response occurs, so that treatment can start in the early mixed dentition.41 The pubertal peak can be identied by several growth indicators, including skeletal maturation (cervical vertebrae maturation method, hand-wrist radiographs), dental maturation, and chronologic age,42 44 45 and more recently the reliability of gingival crevicular uid (GCF) biomarkers specic for growth spurt characterization has been under investigation.46 47 A morphologic predictive factor in successful mandible repositioning with functional appliances is the pretreatment mandibular angle (Co-Go-Me angle ,125.5 degrees). As shown by Franchi and Baccetti39 as well as previous animal and human studies,43 a small mandibular angle is correlated with an enhanced responsiveness to mandibular forward positioning, and vice versa. The usual main limitation for removable functional appliances is patient noncompliance, rated by O’Brien as 18% in children, raising to 30% in adolescence.48 Noncompliance can depend on bulky and invasive devices, difculties in speech, impact on social life, esthetics, and public perception, not precise and predicted orthodontic tooth movements. To overcome these limitations, aligner therapy may be considered a good, reliable, and comfortable alternative. The use of the compliance indicators embedded in the aligner represents a good attempt to monitor patient compliance.49 More recently articial intelligence has been introduced in the orthodontic eld to remote monitor patient compliance (Dental Monitoring, Paris, France). Functional treatment of growing class II patients during their pubertal growth spurt can bring about signicant skeletal and dentoalveolar modications. According to Cozza et al.,37 the twin block is the most efcient removable functional appliance because it can stimulate 0.23 mm/month of mandibular growth (for a total of 3.4 mm in 13 months), followed by the Bionator (0.17 mm/month, total 2.8 mm in 12 months), and then the Frankel II (0.09 mm/month, total 2.8 mm in 18 months). The mechanism behind the Clark twin block is based on the presence of an inclined plane, which pushes the mandible forward, liberates the arches, and redirects the occlusal forces to drive the mandibular advancement and arrest maxillary growth.50 Two companies (Align Technology Inc, San José, CA, USA and Leone SPA Company, Sesto Fiorentino, Firenze, Italy) have developed a new feature within aligner appliances,51 combining the twin block and the aligner advantages to stimulate growth of the mandible while aligning and leveling in growing patients. The Leone company appliance called Runner (Fig. 11.8) consists of a series of clear aligners with incorporated occlusal blocks for mandibular advancement, joining the

125

A

B Fig. 11.8 Runner appliance. Upper arch aligner (A) and lower arch aligner (B). (From Arreghini A, et al. Class II treatment with the Runner in adolescent patients: combining twin block efciency with aligner aesthetics. J World Fed Orthod. 2014;3[2]:71–79.)

Fig. 11.9 Intraoral Invisalign First with mandibular advancement feature.

efciency of the twin block with the esthetics and low bulk of clear aligners.52 The Align Technology company appliance is the Invisalign aligner incorporating lateral wings (Figs. 11.9 and 11.10) engaging the mandible in a forward position.

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Principles and Biomechanics of Aligner Treatment

A

B Fig. 11.10 Invisalign First with mandibular advancement feature. Upper arch aligner (A) and lower arch aligner (B)

The mandibular advancement system is divided into three clinical phases: n

n

n

Pre–mandibular advancement phase: the occlusal locks, which prevent expression of mandibular growth, are removed (correction of overbite, maxillary molar rotations, and overjet) Mandibular advancement phase: 2-mm advancement every eight aligners is performed Transition phase (or stabilization phase): maintains the class II correction

Mandibular advancement can be reached only if other eventual occlusal features have been modified (i.e., maxillary molar derotation, dentoalveolar expansion of the upper arch, deep bite and consequent leveling of the curve of Spee, and retroclination of the incisors), so that a prior preparation phase is required before starting mandibular advancement. While the Runner appliance, the twin block, and other functional appliances are built with a single jump repositioning the mandible, the Invisalign appliance is designed to obtain progressive advancement of the mandible with steps of 2 mm every eight aligners. The progressive advancement of the mandible has been demonstrated to be more effective in producing skeletal outcomes both in animal53 54 and human studies.55 At the end of treatment, mandibular advancement is maintained by arch coordination and anterior interference removal.

In class II treatments, assessment of skeletal age and auxologic potential and predicting the direction of mandibular growth constitute strategic factors determining treatment efcacy. Concerning the importance of right timing to choose the beginning of the interceptive class II correction phase, recent perspective-controlled studies by the University of Turin (Italy) aim to compare dental and skeletal effects of 12 months of therapy with the mandibular advancement feature by Invisalign, when performed on growing patients both at CVM2 and CVM3. When used in the pre-pubertal stage of growth, Invisalign® aligners, with Mandibular Advancement feature, have mainly dentoalveolar effects in the short-term period. When used in the pubertal growth phase, the shortterm effects of Mandibular Advancement feature are dento-skeletal, with an annual rate of change comparable to what has been previously described for the Twin Block appliance.59 According to the existent literature, early treatment of class II division I malocclusion should be provided only to reduce the risk of incisal trauma.56 Additionally, dental injuries have been reported to have a negative impact on the emotional and social domains of the oral health–related quality of life. Since this impact is considerable especially for children having active lifestyles, parents will consider that early orthodontic treatment is worth the nancial costs and burden of care.57 Furthermore, there are young patients for whom the malocclusion is esthetically distressing, and they are bullied for this reason. The use of aligners provided for functional and orthopedic adjuncts can have a positive impact on the self-esteem of those patients even during the orthodontic treatment, providing excellent orthodontic care for such children.

Mandibular Advancement Case Reports CASE STUDY 3 Consider a 9-year-old girl, in mixed dentition, with molar class II relationship, deep bite, proclined upper incisors, and retruded mandible. Cephalometric analysis shows a moderate skeletal class II malocclusion, with an ANB angle value of 5 degrees, and Wits value of 7 mm (Fig. 11.11–11.13). According to Baccetti et al.,42 the patient was in a pubertal growth spurt, which is why the treatment plan was designed to focus on mandibular advancement. An Invisalign Teen treatment with the mandibular advancement feature was performed (Fig. 11.14). The appliance was prescribed to determine an advancement of the mandible together with deep bite correction. The ClinCheck plan forecasted 2 mm of advancement every eight stages, and aligners were changed every week. After 6 months of treatment, a bilateral class I molar relationship was achieved (Figs. 11.15–11.16 and 11.17), and dentoskeletal improvements were achieved.

11 • Interceptive Orthodontics with Aligners

Fig. 11.11 Case 3 Initial extraoral pictures.

Fig. 11.12 Case 3 initial intraoral pictures.

127

128

Principles and Biomechanics of Aligner Treatment

Fig. 11.13 Case 3 initial radiographic records.

Fig. 11.14 Case 3 sagittal view of ClinCheck.

Fig. 11.15 Case 3 nal clinical records.

11 • Interceptive Orthodontics with Aligners

129

Fig. 11.16

CASE STUDY 4 Consider a 10-year-old girl in mixed dentition with psychological issues, reporting bullying episodes due to the protrusion of upper incisors and the retrusion of the mandible. The clinical examination showed a molar class II relationship, severe deep bite, skeletal class II with ANB angle of 6 degrees, and Wits value of 5 mm (Fig. 11.18–11.20).

Analyzing the cervical vertebrae maturation on the lateral x-ray, the patient resulted in a CVM3 phase, according to Baccetti et al,42 and is therefore in a phase of accelerated condylar growth. Since the girl was psychologically stressed because of her bad-looking teeth, an additional stress due to a bulky appliance would not have been the best choice. Thus Invisalign Teen with the mandibular advancement feature was adopted (Fig. 11.21).

130

Principles and Biomechanics of Aligner Treatment

Initial

12 months later

Wits = 7 mm SNB = 72° Co-Gn = 92 mm U1^PP = 127°

Wits = 3 mm SNB = 74° Co-Gn = 98 mm U1^PP = 107°

Fig. 11.17 Case 3 changes of mandibular prole and cephalometric values before and after therapy.

Fig. 11.18 Case 4 initial clinical and radiographic records.

11 • Interceptive Orthodontics with Aligners

Fig. 11.19

131

132

Principles and Biomechanics of Aligner Treatment

Fig. 11.20

In 6 months of treatment, an important correction of the molar relationship and of the proclination of upper incisors was obtained. During the mandibular advancement phase treatment, improvement of the facial prole was the most important motivational factor acting on the patient’s and the parents’ compliance (Figs. 11.22–23 and 11.24).

Conclusions The timing of orthodontic treatment has long been debated. Among the proposed benets of early intervention are the potential for improved response to growth modication. Transversal alterations are frequently seen in general dental practices. Aligners can control the expansion limited to the

Fig. 11.21 Case 4 sagittal view of ClinCheck and superimposition of initial ClinCheck with final ClinCheck (occlusal view).

11 • Interceptive Orthodontics with Aligners

anterior region of the arch to generate adequate space for the spontaneous alignment of the permanent upper lateral incisors prior to complete eruption, helping the future arch development. Researchers in the elds are recommended to dene possibilities and limitations of the approach. Routine early treatment for class II division I malocclusion with retrognathic mandible should not be provided according to the existing quality of evidence. However, there are patients for whom the malocclusion is so esthetically

133

distressing and/or who are bullied signicantly because of it that treatment is certainly indicated. In those cases, the use of a discrete and noninvasive appliance like an aligner with mandibular forward repositioning wings or planes could represent an excellent possibility. Another group of patients for whom the early treatment could be indicated is represented by children with active sports schedules and lifestyles, putting them at risk of incisal trauma because of their large overjet.

Fig. 11.22 Case 4 nal clinical records and changes of mandibular prole.

134

Principles and Biomechanics of Aligner Treatment

Fig. 11.23

Initial

12 months later

Wits = 5 mm SNB = 71° Co-Gn = 91 mm U1^PP = 137°

Fig. 11.24 Case 4 cephalometric values before and after therapy.

Wits = 1 mm SNB = 74° Co-Gn = 96 mm U1^PP = 119°

11 • Interceptive Orthodontics with Aligners

References 1. Keski-Nisula KLR, Lusa V, Keski-Nisula L, et al. Occurrence of malocclusion and need of orthodontic treatment in early mixed dentition. Am J Orthod Dentofacial Orthop. 2003;124(6):631-638. 2. Tausche E, Luck O, Harzer W. Prevalence of malocclusions in the early mixed dentition and orthodontic treatment need. Eur J Orthod. 2004;26:237-244. 3. Pavlow SS, McGorray SP, Taylor MG, et al. Effect of early treatment on stability of occlusion in patients with class II malocclusion. Am J Orthod Dentofacial Orthop. 2008;133(2):235-244. 4. Koretsi V, Zymperdikas VF, Papageorgiou SN, et al. Treatment effects of removable functional appliances in patients with class II malocclusion: a systematic review and meta-analysis. Eur J Orthod. 2015;37(4):418-434. 5. Thiruvenkatachari B, Harrison J, Worthington H, et al. Early orthodontic treatment for class II malocclusion reduces the chance of incisal trauma: results of a Cochrane systematic review. Am J Orthod Dentofacial Orthop. 2015;148(1):47-59. 6. Rossini G, Parrini S, Castroorio T, et al. Children’s perceptions of smile esthetics and their inuence on social judgment. Angle Orthod. 2016;86(6):1050-1055. 7. Grippaudo C, Paolantonio EG, Antonini G, et al. Association between oral habits, mouth breathing and malocclusion. Acta Otorhinolaryngol Ital. 2016;36(5):386-394. 8. Huang YS, Guilleminault C. Pediatric obstructive sleep apnea: where do we stand? Adv Otorhinolaryngol. 2017;80:136-144. 9. Perinetti G, Primožiˇc J, Franchi L, et al. Treatment effects of removable functional appliances in pre-pubertal and pubertal class II patients: a systematic review and meta-analysis of controlled studies. PLoS One. 2015;10(10):e0141198. 10. Salzmann JA. An assessment of the occlusion of the teeth of children 6–11 years, United States: National Center for Health Statistics Vital and Health Statistics, Series 11, no. 130, DHEW Publication no. (HRA) 74–1612, Health Resources Administration, Department of Health Education and Welfare. Washington, DC, 1974, US Government Printing Ofce. Am J Orthod Dentofacial Orthop. 1974;66(4): 462-463. 11. Corbridge JK, Campbell PM, Taylor R, et al. Transverse dentoalveolar changes after slow maxillary expansion. Am J Orthod Dentofacial Orthop. 2011;140(3):317-325. 12. Ciuffolo F, Manzoli L, D’Attilio M, et al. Prevalence and distribution by gender of occlusal characteristics in a sample of Italian secondary school students: a cross-sectional study. Eur J Orthod. 2005;27(6): 601-606. 13. Pirttiniemi P, Kantomaa T, Lahtela P. Relationship between craniofacial and condyle path asymmetry in unilateral cross-bite patients. Eur J Orthod. 1990;12(4):408-413. 14. Piancino MG, Talpone F, Dalmasso P, et al. Reverse-sequencing chewing patterns before and after treatment of children with a unilateral posterior crossbite. Eur J Orthod. 2006;28(5):480-484. 15. Bishara SE, Bayati P, Jakobsen JR. Longitudinal comparisons of dental arch changes in normal and untreated class II, division 1 subjects and their clinical implications. Am J Orthod Dentofacial Orthop. 1996;110(5):483-489. 16. Feres MFN, Raza S, Alhadlaq A, et al. Rapid maxillary expansion effects in class II malocclusion: a systematic review. Angle Orthod. 2015;85(6):1070-1079. 17. Lione R, Brunelli V, Franchi L, et al. Mandibular response after rapid maxillary expansion in class II growing patients: a pilot randomized controlled trial. Prog Orthod. 2017;18(1):36. 18. Haas AJ. Palatal expansion: just the beginning of dentofacial orthopedics. Am J Orthod. 1970;57(3):219-255. 19. Martin AJ, Buschang PH, Boley JC, et al. The impact of buccal corridors on smile attractiveness. Eur J Orthod. 2007;29(5):530-537. 20. Maulik C, Nanda R. Dynamic smile analysis in young adults. Am J Orthod Dentofacial Orthop. 2007;132(3):307-315. 21. Rosa M, Lucchi P, Manti G, et al. Rapid palatal expansion in the absence of posterior cross-bite to intercept maxillary incisor crowding in the mixed dentition: a CBCT evaluation of spontaneous changes of untouched permanent molars. Eur J Paediatr Dent. 2016;17(4):286-294. 22. Algharbi M, Bazargani F, Dimberg L. Do different maxillary expansion appliances inuence the outcomes of the treatment? Eur J Orthod. 2017;40(1):97-106.

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23. Martina R, Farella CM, Leone P, et al. Transverse changes determined by rapid and slow maxillary expansion–a low-dose CT-based randomized controlled trial. Orthod Craniofac Res. 2012;15(3): 159-168. 24. Brunetto M, Andriani JDA, Ribeiro GL, et al. Three-dimensional assessment of buccal alveolar bone after rapid and slow maxillary expansion: a clinical trial study. Am J Orthod Dentofacial Orthop. 2013;143(5):633-644. 25. Nakao K, Goto T, Gunjigake KK, et al. Intermittent force induces high RANKL expression in human periodontal ligament cells. J Dent Res. 2007;86(7):623-628. 26. Cattaneo PM, Dalstra M, Melsen B. Strains in periodontal ligament and alveolar bone associated with orthodontic tooth movement analyzed by nite element. Orthodo Craniofac Res. 2009;12(2):120-128. 27. Melsen B. Palatal growth studied on human autopsy material: a histologic microradiographic study. Am J Orthod. 1975;68(1):42-54. 28. De Clerck HJ, Proft WR. Growth modication of the face: a current perspective with emphasis on class III treatment. Am J Orthod Dentofacial Orthop. 2015;148(1):37-46. 29. Bizzarro M, Generali C, Maietta S, et al. Association between 3D palatal morphology and upper arch dimensions in buccally displaced maxillary canines early in mixed dentition. Eur J Orthod. 2018;40(6):592-596. 30. Martorelli M, Maietta S, Gloria A, et al. Design and analysis of 3D customized models of a human mandible. Procedia CIRP. 2016;49:199-202. 31. Shah M, Verma AK, Chaturvedi S. A comparative study to evaluate the vertical position of maxillary central incisor and canine in relation to incisive papilla line. J Forensic Dent Sci. 2014;6(2):92-96. 32. Alhammadi MS, Halboub E, Fayed MS, et al. Global distribution of malocclusion traits: a systematic review. Dental Press J Orthod. 2018; 23(6):40.e1-40.e10. 33. Li P, Feng J, Shen G, et al. Severe class II division 1 malocclusion in an adolescent patient, treated with a novel sagittal-guidance twin-block appliance. Am J Orthod Dentofacial Orthop. 2016;150(1):153-166. 34. McNamara Jr JA. Components of class II malocclusion in children 8–10 years of age. Angle Orthod. 1981;51(3):177-202. 35. Marsico E, Gatto E, Burrascano M, et al. Effectiveness of orthodontic treatment with functional appliances on mandibular growth in the short term. Am J Orthod Dentofacial Orthop. 2011;139(1):24-36. 36. Chen JY, Will LA, Niederman R. Analysis of efcacy of functional appliances on mandibular growth. Am J Orthod Dentofacial Orthop. 2002;122(5):470-476. 37. Cozza P, Baccetti T, Franchi L, et al. Mandibular changes produced by functional appliances in class II malocclusion: a systematic review. Am J Orthod Dentofacial Orthop. 2006;129(5):599.e1-12; discussion e1-6. 38. Antonarakis GS, Kiliaridis S. Short-term anteroposterior treatment effects of functional appliances and extraoral traction on class II malocclusion: a meta-analysis. Angle Orthod. 2007;77(5):907-914. 39. Franchi L, Baccetti T. Prediction of individual mandibular changes induced by functional jaw orthopedics followed by xed appliances in class II patients. Angle Orthod. 2006;76(6):950-954. 40. Perinetti G, Contardo L, Primozic J. Diagnostic accuracy of the cervical vertebral maturation method. Eur J Orthod. 2018;40(4):453-454. 41. McNamara JA, Brudon WL, Kokich VG. Orthodontics and Dentofacial Orthopedics. Needham Press; 2001. 42. Baccetti T, Franchi L, McNamara Jr JA. The cervical vertebral maturation (CVM) method for the assessment of optimal treatment timing in dentofacial orthopedics. Semin Orthod. 2005;11(3):119-129. 43. Petrovic A, Stutzmann J, Lavergne J. Mechanism of craniofacial growth and modus operandi of functional appliances: a cell-level and cybernetic approach to orthodontic decision making. Craniofacial growth theory and orthodontic treatment. Monograph. 1990;23: 13-74. 44. Beit P, Peltomäki T, Schätzle M, et al. Evaluating the agreement of skeletal age assessment based on hand-wrist and cervical vertebrae radiography. Am J Orthod Dentofacial Orthop. 2013;144(6): 838-847. 45. Franchi L, Baccetti T, McNamara Jr JA. Mandibular growth as related to cervical vertebral maturation and body height. Am J Orthod Dentofacial Orthop. 2000;118(3):335-340. 46. Perinetti G, Baccetti T, Contardo L, et al. Gingival crevicular uid alkaline phosphatase activity as a non-invasive biomarker of skeletal maturation. Orthod Craniofac Res. 2011;14(1):44-50.

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47. de Aguiar MC, Perinetti G, Capelli Jr J. The gingival crevicular uid as a source of biomarkers to enhance efciency of orthodontic and functional treatment of growing patients. Biomed Res Int. 2017;2017:3257235. 48. O’Brien K, Wright J, Conboy F, et al. Early treatment for class II division 1 malocclusion with the twin-block appliance: a multi-center, randomized, controlled trial. Am J Orthod Dentofacial Orthop. 2009;135(5):573-579. 49. Tuncay OC, Bowman SJ, Nicozisis JL, et al. Effectiveness of a compliance indicator for clear aligners. J Clin Orthod. 2009;43(4):263-268. 50. Clark WJ. The twin block technique. A functional orthopedic appliance system. Am J Orthod Dentofacial Orthop. 1988;93(1):1-18. 51. Rossini G, Parrini S, Castroorio T, et al. Efcacy of clear aligners in controlling orthodontic tooth movement: a systematic review. Angle Orthod. 2014;85(5):881-889. 52. Arreghini A, Carletti I, Ceccarelli MC, et al. Class II treatment with the Runner in adolescent patients: combining twin block efficiency with aligner aesthetics. J World Fed Orthod. 2014; 3(2):e71-e79. 53. Wang S, Ye L, Li M, et al. Effects of growth hormone and functional appliance on mandibular growth in an adolescent rat model. Angle Orthod. 2018;88(5):624-631.

54. Kim JY, Jue S-S, Bang H-J, et al. Histological alterations from condyle repositioning with functional appliances in rats. J Clin Pediatr Dent. 2018;42(5):391-397. 55. Aras I, Pasaoglu A, Olmez S, et al. Comparison of stepwise vs singlestep advancement with the functional mandibular advancer in class II division 1 treatment. Angle Orthod. 2017;87(1):82-87. 56. Batista KB, Thiruvenkatachari B, Harrison JE, et al. Orthodontic treatment for prominent upper front teeth (class II malocclusion) in children and adolescents. Cochrane Database Syst Rev. 2018;3(3): CD003452. 57. Brierley CA, DiBiase A, Sandler PJ. Early class II treatment. Aust Dent J. 2017;62:4-10. 58. Bruni A. (2021). Clear aligner treatment for transverse maxillary deciency: in vitro study and randomized controlled trial. Doctoral Dissertation, University of Torino, Torino, Italy. 59. Ravera S, Castroorio T, Galati F, Cugliari G, Garino F, Deregibus A, Quinzi V. Short term dentoskeletal effects of mandibular advancement clear aligners in Class II growing patients. A retrospective controlled study according to STROBE Guidelines. Eur J Paediatr Dent. 2021 Jun; 22(2):119-124.

12

The Hybrid Approach in Class II Malocclusions Treatment FRANCESCO GARINO, TOMMASO CASTROFLORIO, and SIMONE PARRINI

Introduction Several protocols have been proposed for treatment of class II malocclusions. In nonextraction protocols, maxillary molar distalization can be used to correct molar relationships in patients with maxillary dentoalveolar protrusion and minor skeletal discrepancies.1 The upper molars can be distalized by means of extraoral or intraoral forces. In recent years, several techniues have been developed to reduce the dependence on patient compliance, such as intraoral appliances with and without skeletal anchorae. owever, even these devices can produce undesirable tippin of the maxillary molars andor loss of anterior anchorae durin distalization. In the last decades, increasin numbers of adult patients have souht orthodontic treatment and expressed a desire for esthetic and comfortable alternatives to conventional xed appliances. lear aliner therapy T was introduced to answer this reuest. In a review by ossini et al. it has been stated that maxillary molar distalization up to . mm is one of the most predictable movements with T.  This hih predictability was obtained throuh combination of stain, the use of proper attachment conuration, and full-day class II elastics . in, . oz see hapters about lass II treatment and see hapters  and . These results conrm what every orthodontist knows Treatment success reuires technical knowlede from the orthodontist as well as the cooperation of the patient. lass II treatments with T reuire mean treatment times of 1 to  months durin which class II elastics need to be used all day from treatment beinnin until class I canine relationship has been established.  orrective devices should be comfortable, provide rapid and effective treatment, and favor patient compliance with orthodontic treatment. lear aliners are comfortable and aesthetically acceptable as already discussed in the previous chapters,  and reuire stron patient compliance since they are removable. The existin literature showed that the mean duration of obectively measured wear was considerably lower than stipulated wear time amon all removable appliances. urthermore, compliance was found to be better in the early staes of treatment.1 Startin from these premises, the possible combined use of aliners and other orthodontic devices aimed to optimize patient adherence to therapy reducin the time reuired to wear class II elastics has been proposed. This kind of combined approach has been named hybridization of aliner therapy. mon others, temporary anchorae devices

bone-borne hybrid approach see hapter about miniscrews and tooth-borne distalization devices are the most popular hybridization approaches in T. The application of forces in such distalizin appliances could be from buccal reion, palatal reion, or both, and they could be based on slidin mechanics or be friction free e.., in the endulum appliance.

Tooth-Borne Hybrid Approach With Distalizing Device arious types of molar distalization appliances are available and presented in the orthodontic literature, such as the endulum device, the istal et, and the arriere otion  ppliance  enry Schein rthodontics, arlsbad, , S. These appliances are considered easy to install and can promote distal movement of the maxillary molars without the effect of maxillary orthopedic restriction.11 owever, most of these intraoral devices show undesirable reciprocal anchorae loss in the premolars and incisors durin distal molar movement.1 urthermore, molar tippin is freuently observed in most of the cases. The istal et appliance is composed of two bilateral tubes connected to a ance appliance.  bayonet wire is inserted into the linual sheath of the rst molar bands. n the tube there is a stainless steel coil sprin and a clamp. The clamp can slide toward the molar and be tihtened to compress the coil. The force exerted by the sprin beins at 1  and decreases as space is opened.1 The endulum appliance was introduced by ilers in 11 and is still one of the most used distalizin devices.1 It is a xed appliance composed of a plastic pad– contacted palatal ruae. The distalizin force is produced by beta-titanium sprins that extend from the palatal acrylic and t into linual sheaths on the molar tube, which ives reater control of these teeth.1 oth the istal et and endulum appliances produce an increase in vertical dimension due to a backward rotation of the mandible.1-1 These vertical chanes comprise a sliht openin of the mandibular plane anle about 1 deree and an increase in lower anterior facial heiht .–. mm.1 hosh and anda reported that the increase in lower anterior facial heiht was sinicantly reater in patients with hiher pretreatment mandibular plane anles. The increased lower facial heiht and mandibular plane anle could have resulted from drivin the 137

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molars back into the “wede.” These results suest that the endulum may be contraindicated in patients with excessive lower facial heiht andor minimal overbite.1 Similar results were reported for the istal et appliance.1 The maxillary molar distalization obtained with those appliances is characterized by a reat amount of molar distal tippin in averae .1 derees.1 hereas the istal et produces a labial tippin of the upper incisors as a result of the uncontrolled counterforce actin on the premaxillae, the endulum appliance showed a more controlled inclination of the upper incisors with a mild crown buccal tippin.  consists of two riid bars bonded bilaterally to the maxillary canines and rst molars. The canine pad with a built-in mesial hook used for placement of intermaxillary elastics is bonded to the anterior third of the clinical crown. osteriorly, the molded pad with a ball-and-socket oint is bonded to the rst molar at the center of its clinical crown to facilitate molar derotation and distalization.1- The activation of the appliance is obtained by the use of two types of elastics the rst one bein . in,  oz the second one .1 in,  oz, to be used from the second month of treatment until the molar and canine class I relationships are established. lastics should be worn  hours per day, chanin elastics three times per day. The principle of this appliance is similar to a cantileverbased xed appliance previously shown by anda. The author described that system as an effective way to correct molar class II in nonrowin patients. n active cantilever with information of molar tipback was applied at the upper arch, while in the lower arch the author used a multibracket xed appliance and class II elastics. The undesired effects of class II elastics were controlled by the xed appliance in lower arch and by the activation of the cantilever in upper arch. revious retrospective clinical studies demonstrated the possibility of obtainin a maxillary molar distalization between 1. and .1 mm with the mean amount of molar tippin not exceedin . derees when  was used in combination with xed appliances as anchorae units on the lower arch. urthermore the treatment time had a mean duration of about  to  months. There is a lack of hih-uality evidence supportin or contrastin the use of . In another retrospective study in which  effects were compared to other class II correction methods,  showed the same results obtained with class II elastics in terms of molar distalization but in less time. ne clinically and statistically relevant effect of treatment with  occurred in lower anterior facial heiht that was associated with a sinicant increase in the mandibular plane anle. roclination of the lower incisors resultin from the class II elastics mechanics was observed and resulted in a sinicant amount . derees. ll the tooth-borne appliances mentioned earlier produce some side effects that need to be controlled durin the hybrid aliner treatment. xcessive upper and lower incisor proclination could be difcult to control with aliners. ccordin to ossini et al., buccolinual tippin and torue control of upper incisors have a mean accuracy of about  of the planned movement. The proclination of lower

incisors resultin from the use of  could be controlled usin active aliners on the lower arch and applyin a linual radicular torue information on the lower incisors of at least  derees. nother side effect that can occur usin tooth-borne distalization devices is the rotation of the occlusal plane due to the increase of the vertical dimension. hosravi et al. in their study about overbite manaement with Invisalin aliners showed that overbite correction is mostly related to anterior teeth movement without any sinicant posterior intrusion andor extrusion. s described by avera et al. bite block effect of the aliner causes an intrusive effect on posterior teeth of . mm.  similar value . mm was described by antovani et al. Therefore, only the .- to .-mm bite block effect should be considered to counteract the increase of the vertical dimension produced by tooth-borne distalization devices averae increase – mm. n the basis of these considerations, tooth-borne distalization devices should be avoided in patients with excessive lower facial heiht andor minimal overbite. linicians should be aware of the existin evidence related to the limited control of posterior intrusion, overbite correction, and buccolinual inclination provided by T. Two clinical examples will be presented one in a teen patient and the second in an adult patient.

Case eport 1 DIAGNOSTIC SUMMARY  1-year-old female patient presented with molar class II malocclusion, skeletal class II, normal diverence, protrusion of upper and lower incisors, and unerupted upper left canine is. 1.1, 1., and 1.. The impaction was related to the mesialization of upper left posterior teeth with a conseuent absolute lack of space for the canine eruption. adioraphs conrmed the buccal displacement of the impacted upper canine. The patient’s main concern was lack of the upper left canine. The treatment plan was desined to obtain bodily distal movements of upper molars, premolars, canines, and frontal teeth to achieve a dental molar and canine class I, and recover the proper space for  without extractions.  endulum  appliance was bonded on the upper arch to distalize maxillary molars i. 1.. nce the class I was overcorrected  months treatment, the endulum appliance was debonded, and a new intraoral scan was made to start the aliner treatment. The aim of this second phase was to close the remainin spaces in the upper arch, to recover tooth  in the arch and to correct lower crowdin. The same day temporary thermoformed retainers were provided to the patient.  set of  Invisalin aliners was produced to complete the distalization movements on the upper arch and to correct the lower arch mild crowdin. liner chane was planned every week. urin the aliner phase the patient was educated to wear class II elastics . in, . oz bilaterally to reinforce anterior anchorae while distalizin premolars. To anchor class II elastics, buttons were bonded

12 • The Hybrid Approach in Class II Malocclusions Treatment

139

Fig. 12.1 Case 1. Etraoral pictures before treatment.

on the lower rst molars, while aliner hooks were used on the upper rst premolars reion. nce enouh space was obtained, the upper left canine was surically exposed with a vestibular ©ap, and a button with stainless steel hook was bonded to the buccal surface of the crown. The tooth was then moved distally rst with

class II elastics to recover a proper position on the saittal plane i. 1.. hen  was close enouh to the occlusal plane, new intraoral scans were performed to obtain a new set of 1 aliners to finalize the case is. 1., 1., and 1.. The total treatment duration was  months.

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Fig. 12.2 Case 1. Intraoral pictures before treatment.

A

B Fig. 12.3 Case 1. A Panoramic ray before treatment. B ateral ray before treatment.

12 • The Hybrid Approach in Class II Malocclusions Treatment

Fig. 12.4 Case 1. Intraoral pictures at end of sagittal rst phase.

Fig. 12.5 Case 1. Intraoral pictures before additional aligner stage.

141

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Principles and Biomechanics of Aligner Treatment

Fig. 12.6 Case 1. Etraoral pictures at end of treatment.

Fig. 12.7 Case 1. Intraoral pictures at end of treatment.

12 • The Hybrid Approach in Class II Malocclusions Treatment

A

143

B Fig. 12.8 Case 1 A Panoramic ray at end of treatment. B ateral ray at end of treatment.

Case eport 2 DIAGNOSTIC SUMMARY  -year-old male patient presented with molar class II malocclusion, skeletal class II, low mandibular plane anle, overbite, and crowdin on both upper and lower arches is. 1., 1.1, and 1.11. The patient’s main concern was the excessive upper canine buccal displacement and proclination of upper incisors. The treatment plan was made to obtain bodily distal movements of upper molars, premolars, and canines to achieve a dental molar and canine class I, center midlines, and correct crowdin on both arches.   was bonded in the upper arch on both sides to correct saittal relationship on molars, bicuspids, and canines i. 1.1. In the meantime, the lower arch treatment started with a rst set of  aliners to correct lower crowdin.  buccal

tube was bonded on lower rst molars to allow activation of both  throuh the use, for the rst month, of . in,  oz elastic placed from the mesial hook of the  to the mesial hook of the lower buccal tubes. rom the second month until class I molar and canine resulted, the patient used a .1 in,  oz elastic with elastic chanes three times a day. liners were instructed to be chaned every  weeks at that stae. nce the class I was obtained on both sides  months treatment, the  was debonded, and a new intraoral scan was made of the aliner treatment i. 1.1. The aim of this second phase was to close the remainin spaces in the upper arch created durin saittal correction on both sides and to complete crowdin correction in the lower arch. Throuh the same scan and a three-dimensional printin in-office procedure, one temporary thermoformed retainer was provided to the patient who was instructed to wear it day and niht.

Fig. 12.9 Case . Etraoral pictures before treatment.

144

Principles and Biomechanics of Aligner Treatment

Fig. 12.10 Case . Intraoral pictures before treatment.

A

B Fig. 12.11 Case . A Panoramic ray before treatment. B ateral ray before treatment.

12 • The Hybrid Approach in Class II Malocclusions Treatment

Fig. 12.12 Case . Intraoral pictures before sagittal rst phase.

Fig. 12.13 Case . Intraoral pictures before additional aligner stage.

145

146

Principles and Biomechanics of Aligner Treatment

 set of 1 Invisalin aliners was produced to perform space closure in the upper arch and to correct the lower arch mild crowdin. liner chane was planned every week. fter 1 months of treatment, class I canine and molar resulted on both sides, midlines centered, and deep bite

improved such as upper and lower arch forms. Third molars present, the patient is currently in retention with vacuum-type retainers that are used all nihts. urin the retention period, the patient will be followed up to evaluate third molars is. 1.1, 1.1, and 1.1.

Fig. 12.14 Case . Etraoral pictures at end of treatment.

Fig. 12.15 Case . Intraoral pictures at end of treatment.

12 • The Hybrid Approach in Class II Malocclusions Treatment

147

Fig. 12.15, co’

A

B Fig. 12.16 Case . A Panoramic ray at end of treatment. B ateral ray at end of treatment.

References 1. olla , uratore , arano , et al. valuation of maxillary molar distalization with the distal et a comparison with other contemporary methods. Angle Orthod. 1-. . rec , anson , ranco , et al. Intraoral distalizer effects with conventional and skeletal anchorae a meta-analysis. Am J Orthod Dentofacial Orthop. 11-1.

. avera S, astro©orio T, arino , et al. axillary molar distalization with aliners in adult patients a multicenter retrospective study. Prog Orthod. 111. . ossini , arrini S. ereibus , et al. ontrollin orthodontic tooth movement with clear aliners. n updated systematic review reardin efcacy and efciency. J Aligner Orthod. 11-.

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. arino , astro©orio T, aher S, et al. ffectiveness of composite attachments in controllin upper-molar movement with aliners. J Clin Orthod. 11-. . ichter , anda S, Sinha , et al. ffect of behavior modication on patient compliance in orthodontics. Angle Orthod. 11-1. . ombardo , olonna , arlucci , et al. lass II subdivision correction with clear aliners usin intermaxilary elastics. Prog Orthod. 111. . edwed , iethke . otivation, acceptance and problems of invisalin patients. J Orofac Orthop. 1-1. . osvall , ields , iuchkovski , et al. ttractiveness, acceptability, and value of orthodontic appliances. Am J Orthod Dentofacial Orthop. 1.e1-e1. 1. Shah . ompliance with removable orthodontic appliances. Evid Based Dent. 111-1. 11. arano , Testa . The distal et for upper molar distalization. J Clin Orthod. 1-. 1. ntonarakis S, iliaridis S. axillary molar distalization with noncompliance intramaxillary appliances in class II malocclusion a systematic review. Angle Orthod. 11-11. 1. arano , Testa , Siciliani . The linual distalizer system. Eur J Orthod. 11-. 1. ilers . The pendulum appliance for class II noncompliance therapy. J Clin Orthod. 1-1. 1. roft , ields , Sarver . Contemporary Orthodontics. St. ouis,  osby lsevier . 1. arure S, atil , eddy S, et al. The effectiveness of pendulum, -loop, and distal et distalization techniues in rowin children and its effects on anchor unit a comparative study. J Indian Soc Pedod Prev Dent. 11-. 1. yloff , arendeliler , lar , et al. istal molar movement usin the pendulum appliance. art  the effects of maxillary molar root uprihtin bends. Angle Orthod. 11-.

1. haués-sensi , alra . ffects of the pendulum appliance on the dentofacial complex. J Clin Orthod. 1-. 1. yloff , arendeliler . istal molar movement usin the pendulum appliance. art 1 clinical and radioloical evaluation. Angle Orthod. 1-. . hosh , anda S. valuation of an intraoral maxillary molar distalization techniue. Am J Orthod Dentofacial Orthop. 111 -. 1. arrière .  new class II distalizer. J Clinic Orthod.  -1. . artel . The arriere distalizer simple and efcient. Int J Orthod Milauee. 1-. . odríuez . nilateral application of the arriere distalizer. J Clin Orthod. 111-1. . Sandifer , nlish , olville , et al. Treatment effects of the arrière distalizer usin linual arch and full xed appliances. J orld ed Orthod. 1e-e. . anda . Biomechanics in Clinical Orthodontics.  Saunders 1. . in , an , uo , et al. valuatin the treatment effectiveness and efciency of arriere distalizer a cephalometric and study model comparison of class II appliances. Prog Orthod. 11. . im-erman , camara r , ints , et al. Treatment effects of the arriere otion  ppliance for the correction of class II in adolescents. Angle Orthod. 1-. . hosravi , ohanim , uoel , et al. anaement of overbite with the Invisalin appliance. Am J Orthod Dentofacial Orthop. 1111-. . antovani , arrini S, oda , et al. icro computed tomoraphy evaluation of Invisalin aliner thickness homoeneity. Angle Or thod 1. doi1.1-.1. pub ahead of print. . inziner S, ehrbein , ross , et al. olar distalization with pendulum appliances in the mixed dentition effects on the position of unerupted canines and premolars. Am J Orthod Dentofacial Orthop. 1-1.

13

Aligners and Impacted Canines EDOARDO MANTOVANI, DAVID COUCHAT, TOMMASO CASTROFLORIO

Introduction Except for the third molars, the impaction of the upper canine is the most common in the permanent dentition, and its recovery is nearly always recommended. The importance of canines, both from a functional and an aesthetic point of view, is crucial to set a proper occlusion. Furthermore, possible adverse sequelae of canine impaction1 can be as follows: n

n n n

iration of the neihborin teeth and loss of arch lenth External root resorption of the neihborin teeth entierous cyst formation nfections related to partial eruption

The prevalence of upper canine impaction is ranin between . and ., dependin on the population, ae, sex, and ethnicity.- The impacted maxillary canines are more common in white populations and in female patients, with a male to female ratio of approximately 1:. mpactions are unilateral in the maority of cases, and the occurrence on the palatal side is three times hiher than on the labial side., ome systemic endocrine or infectious diseases are related with failed eruption of one or more teeth Fi. 1.1.1 They act as predisposin factors but always in conunction with a local patholoic condition, such as11: n n n n n n n n

upernumerary teeth dontomas ental anomalies ysts revious trauma Early extractions nylosis left lip and palate

These factors can be associated with impactions of every tooth and are usually related to incisors or premolars. Therefore, other causes can be identied reardin impacted canines. ince impacted upper canines have been diverted or are anulated aberrantly durin development, it has been assumed that eruption of the canine is stronly inuenced by environmental factors.1 1 The maxillary canine has the lonest path of eruption, and a lon time period is needed. This could explain the hiher percentae of inclusion compared to other teeth. The upper canine beins its development from the superior part of the maxilla. t ae  years, the crown is located

in correspondence of the apex of deciduous canine, mesially inclined.1 hen the permanent incisors are erupted, the close relationship between the crown of the canine and the distal aspect of the root of lateral incisor is particularly important.1 ince the upper cuspid is one of the last teeth to reach its position, the lac of space in the arch can have a reat inuence on the prevalence of impactions, especially reardin the labial ones.1 The studies that have investiated palatal impactions pointed out the increased incidence of missin or peshaped laterals.11,1 This leads to the formation of two theories: the enetic theory and the uidance theory.,,1 oth theories share the belief that certain enetic features occur in association with the palatal displacement of maxillary canines. The riht side of any patient is enetically identical to the left side. ince many studies indicated  to  preponderance of unilateral canine impaction, it is reasonable to state that local factors are the prevailin elements.1 ilberman demonstrated that anomalies of the lateral incisors in patients with palatally displaced maxillary canine  teeth were found to be four times that of the eneral population.1 The canine impaction has been related with abnormalities reardin the shape and lenth of the root of the lateral incisor rather than its aenesis Fi. 1.. owever, missin, small, and pe-shaped lateral incisors are three varieties of expression of a sinle enetic factor.  pe-shaped or small lateral incisor on one side of the mouth and a missin on the other can be frequently seen Fi. 1.. ccordin to the uidance theory of canine impaction, these factors create a enetically determined environment in which the developin canine is deprived of its uidance, thus inuencin it to adopt an abnormal eruption path.

Early Diagnosis and Treatment  tooth is impacted when it fails to erupt into the dental arch within the expected developmental window. Therefore, an early dianosis is crucial to reduce the consequent issues. alpation of the labial fornix to assess the crown of the eruptin canine is the rst clinical attempt needed to identify a possible impaction. n case of a well-mared prominence absence in the late mixed dentition, orthopantomoraphy  is mandatory Fi. 1..1 The early identication sins on radioraphs of an abnormal pathway of eruption is needed to prevent canine retention and maxillary incisor root resorption. 149

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Principles and Biomechanics of Aligner Treatment

B

A

C

D

E Fig. 13.1 (A–E) Early deciduous teeth extraction leads to loss of space and canine impaction.

The deciduous canine extraction is recommended when limited or absent resorption of its root can be detected, in class  uncrowded malocclusions.1, Ericson and urol,1 to evaluate the need of primary canine extraction and its corrective effect, determined a method for detection of the permanent canines, based on the followin Fi 1.: n n

The anle of the canine and the midline axis a The distance from the cusp tip to the occlusal line d

The position sector s in the frontal view n etween the midline and the axis of the 1 n etween the axis of 1 and  n etween the axis of  and  The success rate of early extractions will vary dependin on the position of the permanent canine on . f the crown of the permanent canine is distal to lateral incisor root axis, the primary canine extraction normalied the eruptin position of the permanent canine in 1 of the cases. n contrast, the success rate decreased to  if n

13 • Aligners and Impacted Canines

A

B

C Fig. 13.2 (A–C) mall sie lateral incisors and impacted cuspids.

A

B Fig. 13.3 (A) issing lateral incisors and (B) ilateral cuspid impaction.

151

152

Principles and Biomechanics of Aligner Treatment

A

B

C Fig. 13.4 (A–C) Bac of right canine prominence in late mixeddentition patient.

A

B Fig. 13.5 (A B) The orthopantomography refers to the patient in ig. . Ericson and urol canine impaction analysis.

13 • Aligners and Impacted Canines

91%

153

64%

A

Fig. 13.6 uccess rate of early deciduous canine extraction (from Ericson and urol).

the permanent canine crown were mesial to the midline of the lateral incisor root Fi. 1.. onetti et al. demonstrated that deciduous canine and rst molar extractions are more effective as a preventive approach to promote eruption of retained maxillary permanent canines positioned palatally or centrally. n the lateral cephalometric radioraph the normal inclination of the canine compared to the perpendicular to the Franfurt plane should be about 1 derees Fi. 1.. iher values are related with increased need for orthodontic treatment. on et al., usin cone-beam computed tomoraphy T data, stated that the maxillary transverse dimension had no effect on the occurrence of . accetti demonstrated that, in  cases not requirin maxillary expansion, the use of a transpalatal arch T in combination with deciduous canine extraction can be effective for the permanent canine eruption. n the contrary, there is a strict relationship between the lac of space and the labially impacted canines, in particular a transverse maxillary deciency located in the anterior portion of the dental arch. esearch usin the T approach stated that buccal canine impaction is mostly associated with anterior transverse dental and seletal deciency. ubects with unilateral or bilateral impacted maxillary canines have smaller maxillary transverse dimensions than subects without impaction.1 The effect of rapid palatal expansion as a predictor of automatic eruption has been previously demonstrated.  Early treatment of impacted canines is mandatory in case of severely resorbed incisors. hen resorption process is halted, the incisors do not suffer from increased mobility or discoloration in the lon term.

B

C

Fig. 13.7 (A–C) Inclination of the canine on lateral cephalometric analysis parents of this patient refused phase  treatment and upper left canine impaction occurred  years later.

Late Diagnosis ianosis of upper canine impaction after the expected ae of eruption is primarily clinical, with or without the presence of the correspondin deciduous canine. Ectopic or absent canine prominence is usually detected durin the examination. The information provided by  ives an overall picture but cannot determine the proper position of the canine. owever, when it is possible to identify the

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Principles and Biomechanics of Aligner Treatment

cause of failed eruption e.., a mechanical obstacle such as odontoma, its removal can allow the tooth to erupt spontaneously. indauer, in his study usin panoramic x-ray, found that  of  had their cusp tip distal to the lateral incisor and remained undetected. T systems provide three-dimensional  imaes and useful data for a more accurate locatin of impacted teeth. T investiations have proven to be superior in detectin root resorption compared with conventional radioraphic methods intraoral and panoramic radioraphs. The amount of resorption detected by T scannin was approximately  hiher. oot resorption of the maxillary permanent incisors caused by ectopic eruption of the permanent canine has an overall prevalence of 1, with a prevalence that is four times as hih in irls as in boys. ental follicles of the ectopically eruptin canines are on averae wider than those of the normally eruptin canines. urin eruption, the follicle of the eruptin maxillary canine frequently resorbs the periodontal contours of adacent permanent teeth but not the hard tissues of the roots. esorption of neihborin permanent teeth durin maxillary canine eruption is most liely an effect of the physical contacts with active pressure durin eruption and cellular activities. The resorptive mechanism seems to be conned to the dental follicle and related to metabolic activation. an found no sinicant difference of resorption prevalence between subects with buccal and palatal impactions. The dominant predictor for resorption was contact relationship less than 1 mm.1 nother recent T study found no sinicant correlation between follicle width and the variables of ender, impaction side, and localiation of maxillary impacted canines. ther factors inuencin dianosis and treatment plannin, such as anylosis and root dilaceration, can be identied mostly on T imaes. Furthermore, T data can provide useful information about shape and sie of the impacted canine, especially if further intraarch space is required Table 1.1. ccordin to ecer, the maor reasons for failure are inadequate anchorae ., mistaen location and directional traction ., and anylosis .. There is no ae limit for orthodontic recoverin of impacted canines, but the chance of success decreases with ae.  study undertaen in adult patients found . success rate of impacted maxillary canine treatment amon the adults compared with 1 amon the youner controls, even thouh the overall lenth of orthodontic treatment was similar. ll the failed canines were found in the older adult subroup . years of ae.

Treatment Planning and Orthodontic Management The main oal of every orthodontic treatment is not only the correction of malocclusion but also a ood alinment and healthy periodontal tissues. eardin impacted canines, the eruption should be in the center of the alveolar ride. urin physioloic eruption there is a fusion between eratinied iniva and reduced enamel epithelium with the formation of the unctional epithelium. hen this occurs, a proper arranement of periodontium with an adequate band of eratinied tissue, correct sulcular depth, and connective bers inserted on cementoenamel unction E can be found. f a canine erupts in the alveolar mucosa, lac of unctional epithelium may occur, leadin to further mucoinival issues Fi. 1.., Teeth erupted in a labial position can promote the thinnin of the cortical plate and the formation of bony dehiscence or fenestration. This situation is related to lac of eratinied iniva and hiher prevalence of recessions Fi. 1..1, The adequate amount of eratinied iniva has been reported as between  and  mm, however, thinner inival tissue is at hiher ris of inival recession development durin orthodontic movement. hen conditions do not allow achievement of the eruption with a ood periodontal

A

Table 13.1 actors Affecting Prognosis n

epth of impaction

n

ac of space in the dental arch

n

Age of the patient

n

Cooperation of the patient

B Fig. 13.8 (A B) Canine eruption in aleolar mucosa.

13 • Aligners and Impacted Canines

155

B

A

Fig. 13.9 (A B) Canine erupted laially ith lac of eratinied gingia and higher ris of recession.

support or in a reasonable treatment time, premolar substitution, retention of the primary canine, or prosthetic rehabilitation must be taen into account Fi. 1.1. ince a proper dianosis is mandatory for correct orthodontic and surical plannin, the rst issue to deal with is depth of impaction. t can be found as a soft tissue impaction, a partial intraosseous impaction, or a deep full bony impaction.  method of analyin severity of impactions usin T was proposed by au. This method utilies the entire three views horiontal, vertical, and axial of a T imae. ependin on its anatomic location, the cusp tip and the root tip are each iven a number between  and  in  taen from a pretreatment imae. The sum of the cusp tip and root tip scores in the three views dictated complexity of treatment. To obtain the eruption at the center of the alveolar ride, not only the point of eruption of the cuspid but also the path must be taen into account. irect traction is provided when relationship with adacent teeth is favorable. f not, the canine must be moved in a different direction Fi. 1.11.

A

 recent classication has been proposed to cateorie maxillary impacted canines as type  hih ris and type  low ris. Type  teeth represent a hih ris of periodontal damae on neihborin teeth, includin root resorption. They need early exposure to be pulled away from closer roots. ther teeth must not be moved until they reach a safe position. Type  canines do not require immediate exposure and can be moved directly in their nal position. Therefore, combined orthoperiodontal treatment aims to uide the canine at the center of the alveolar ride in three steps: 1. nitial orthodontic phase . urical intervention . rthodontic traction and alinment sually, before the intervention, a preliminary orthodontic phase is needed to ain space in the arch with alinin and levelin. The initial orthodontic phase should provide a ood control of the archform and maintain space for the impacted canine.

B Fig. 13.10 (A–E) eep horiontal impaction may undermine the eruption ith a good periodontal support. Continued

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Principles and Biomechanics of Aligner Treatment

C

E

A

D

Fig. 13.10, cont’d

B Fig. 13.11 (A B) ateral incisor on the eruption path of the impacted canine.

13 • Aligners and Impacted Canines

The sie of the canine should be calculated automatically usin linchec software if a contralateral canine is present. therwise a diital approximation should be made accordin to the sie of the other teeth. To avoid any ris of interference, roots of incisors and premolars close to the canine should be moved carefully.  proper anchorae is needed before the surical intervention to support the orthodontic traction the use of temporary anchorae devices Ts can be helpful. im of the surical exposure is the application of a device for the traction, such as button or a mesh, as close as possible to the cusp tip the least amount of bone and eratinied tissue removal is desirable. Two methods of surical-orthodontic traction of impacted teeth can be used: the open ap and closed eruption techniques. The open technique includes surical exposure of the crown by either complete removal of bone and soft tissue directly overlyin the impacted canine or the use of an apically repositioned inival ap without startin orthodontic traction and waitin on the self-eruption. The closed technique involves elevatin a full mucoperiosteal ap, exposin the canine crown to bond an attachment, then suturin. The orthodontic traction is applied until the eruption of the tooth. assina found that open surical exposure seems to be associated with reduced treatment duration and anylosis ris over the closed technique. Furthermore the closed technique does not allow direct control of the eruption path, and the detachment of the orthodontic device may require a second surery. n the other hand, the rst intention wound healin can ensure a better postoperative course. The aim of the postsurical phase is to brin the impacted tooth into the desired position on the arch. nce the canine has been exposed, continuous liht forces –  are required usin elastics or elastomeric chains. The aliner can be modied with burs or pliers to create proper hoos on which elastics or elastomeric chains can be anchored. eavy forces may cause loss of anchorae intrusion and sinicant root resorption of the adacent anchorae teeth. hen traction is provided directly by elastomeric chains, if the patient does not wear aliners adequately, unwanted forces can develop and unwanted movement of anchorae teeth can occur. The patient must wear the intraarch elastics for  hours a day alon with the aliners.

Labial Impactions ince the amount of attached iniva after eruption and therefore the nal periodontal health is affected by the surical technique, labial impactions are more challenin to manae. ased on the relationship between the impacted canine heiht and the mucoinival unction , three different surical techniques are traditionally used to uncover labially impacted canines: inivectomy, apically positioned ap, and closed eruption. The inivectomy is indicated when there is a soft tissue impaction, more than a third of the crown is below the , and a proper amount of eratinied iniva about – mm is preserved above the exposed crown. The apically positioned ap is used in shallow labial impactions when most of the crown is located apically to the

157

, especially when a little amount of attached iniva is detected.  minimum of  mm of attached iniva should be embedded in the ap desin. The closed eruption technique is recommended when the position of the crown is coronal to the mucoinival unction, or if the labiolinual position of the impacted canine is toward the center of the alveolar ride, to avoid massive inival and bone removal. ermette et al. stated that labially impacted teeth mostly need closed eruption technique to reduce unaesthetic sequelae such as increased clinical crown lenth. n a recent split-mouth study, ee et al. found that after the closed eruption technique, impacted canines exhibited sliht but clinically insinicant periodontal recession compared with the contralateral normal tooth. ccurrence of recession is related to the root developmental stae and pretreatment depth and anle.

Palatal Impactions ccordin to ecer and ilberman1 the ideal treatment approach is from the palatal side. nitial traction should be applied in a linually downward direction to prevent interference with the neihborin teeth.  recent review by arin stated that when a unilateral  is exposed and alined, there is a small periodontal impact with no clinical relevance in the short term they found no difference in periodontal health when the open and closed techniques were compared. efore orthodontic treatment, the open technique involves surical exposure of the canine and the overlyin palatal tissue removal. ealin is attained by secondary intention.  lare removal of bone and inival tissue can lead to a sinicative loss of clinical attachment and inival recession so that this technique should be avoided in cases of deep impaction. Furthermore, damae of the E can promote an increased ris of anylosis. The closed technique involves uncoverin the canine, attachin an eyelet and old chain, and then suturin the palatal mucosa bac over the tooth., n this case, a force is applied on the tooth to speed up the eruption. riticality of this method is the possible detachment of the orthodontic device. owever, the rst intention wound healin can lead to better periodontal and aesthetic outcomes with lower morbidity for the patient.

linical ase FIRST VISIT ate: --1 ender: ale e: 1y m

ORTHODONTI DINOSIS eletal n   ,   ental n olar  , canine  nonassessible, deep bite, increased , spaces between teeth

158

Principles and Biomechanics of Aligner Treatment

Facial n Flat prole ultiple aenesis: 1, 1, , , 1, ,  mpacted: 1, ,  Fis. 1.1, 1.1, and 1.1 are provided.

. urical exposure . Final alinment

TRTNT RORSS Fis. 1.1 and 1.1 show details of the treatment proress.

TRTNT N 1. ral hyiene instructions and motivation . nterior diastemas closure and anchorae preparation

A

FIN Fis. 1.1, 1.1, and 1.1 show nal treatment results.

C

B

Fig. 13.12 (A–C) Clinical case study aseline extraoral.

A

B Fig. 13.13 (A–E) Clinical case study aseline intraoral.

13 • Aligners and Impacted Canines

C

159

D

E Fig. 13.13, cont’d

A

B Fig. 13.14 (A–) Clinical case study aseline xrays. Continued

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Principles and Biomechanics of Aligner Treatment

C

D Fig. 13.14, cont’d

13 • Aligners and Impacted Canines

E

F Fig. 13.14, cont’d Continued

161

162

Principles and Biomechanics of Aligner Treatment

G Fig. 13.14, cont’d

A

B Fig. 13.15 (A–E) Clinical case study progression.

13 • Aligners and Impacted Canines

C

163

D

E Fig. 13.15, cont’d

A

B Fig. 13.16 (A–) Clinical case study progression. Continued

164

Principles and Biomechanics of Aligner Treatment

C

D

E

F Fig. 13.16, cont’d

A

B

C

Fig. 13.17 (A–C) Clinical case study extraoral nal.

13 • Aligners and Impacted Canines

A

B

C

D

E

Fig. 13.18 (A–E) Clinical case study intraoral nal.

165

166

Principles and Biomechanics of Aligner Treatment

A

B Fig. 13.19 (A B) Clinical case study nal xrays.

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14

Aligner Orthodontics in Prerestorative Patients KENJI OJIMA, CHISATO DAN, and TOMMASO CASTROFLORIO

Introduction According to a recent American Association of Orthodontists statement, today one in four orthodontic patients is an adult.1 In this specic category of patients, orthodontics can be called on to treat either primary malocclusions that have not been treated before or secondary malocclusions due to orthodontic relapse or pathologic tooth migration related to periodontal disease (see Chapter 1. Advances in orthodontics have also made treatment more comfortable and less noticeable than ever for individuals of all ages. any of today’s treatment options are designed to minimie the appearance of the appliance to better t any lifestyle. Apart from the innovations in the eld, the increasing demand of orthodontic treatment from adult patients is due to an increased aareness by patients of the need for good oral health, enabling the patient to reach adulthood ith a greater number of teeth in the mouth. It also happens by the increase on esthetic reuirement from society.  espite possible functional problems, many of those seeing orthodontic treatment are een to improve dental esthetics and, potentially, their uality of life regarding both functional aspects and appearance. he relative importance of esthetics in current society is understood hen analying the positive attributes associated ith physical attractiveness. any of the adults looing for orthodontic treatment have orn or abraded teeth, previous restorations, missing teeth, supraeruption and occlusal plane discrepancies, malformed teeth, collapse of the vertical dimension due to the loss of posterior teeth, and many other problems reuiring an interaction beteen orthodontics and restorative dentistry. oever, the connection beteen the to specialties is reuired for young patients hen agenesis spaces should be managed or hen the recovery of a proper smile esthetics reuires cron shape modications. Orthodontic diagnosis aims, among others, to determine the degree of harmoniation reuired to correct dental or dentomaillary disorders and to indicate hether prosthetic or restorative compensation is needed and hat form it should tae. ental professionals should alays carefully consider tooth position in prosthodontic treatment to determine hether orthodontic treatment can improve prosthodontic treatment outcomes. Controlling tooth position ith orthodontics can help the prosthodontist in creating restorations that are more stable, functional, and esthetic. 168

Space Management in the Anterior Region pace management represents the eld in hich the cooperation beteen orthodontist and prosthodontists is very common. he most freuent reason is represented by agenesis, especially of the upper lateral incisor, because of its relative high prevalence and impact on a high esthetic value area. atients ith congenitally missing maillary lateral incisors often need a challenging interdisciplinary treatment, hether canine substitution, single implants, or tooth-supported restorations are chosen. Currently, it ould be inappropriate to remove enamel and dentin to place crons on adacent teeth in patients ith dental agenesis, mainly if these individuals have no restorations or ear of their eisting teeth. In case of unilateral agenesis of the maillary lateral incisor, space closure should not be used, ecept in eceptional cases, because of subseuent esthetical and functional problems. If the treatment plan calls for opening of the edentulous spaces, implants ould be an ideal alternative for replacing the missing teeth. esearch has shon that the success rate of implants is very high. oever, maillary lateral incisor implants are challenging aesthetically. he amount of space is often small, the alveolar ridge may be decient, the papillae are occasionally short, the adacent roots could be too close, the gingival levels may be uneven, and the patient could be too young. Any of these issues could compromise the aesthetic outcome of even the nest surgical implant placement. In this approach, orthodontic treatment combines 1. unctional placement of the canine . Creation of sufcient space to accommodate a cosmetic replacement for the missing lateral incisor oring ith aligners, the functional placement of the canine reuires the use of attachments to properly control the movement of the root in the three dimensions. A good option to obtain predictable movements is alays represented by their seuentialiation. If the canine reuires distaliation, mesiodistal root tipping, and torue control, then a good suggestion is to plan distaliation steps of  mm, application of mesial root tipping of at least  degrees every  mm of distaliation, and (only once distaliation and mesiodistal root tipping have been completed planning the root torue information.1 he control of all those movements can be achieved ith the use of rectangular and vertical attachments. If a patient is congenitally missing one maillary lateral incisor, the amount of space to accommodate a cosmetic replacement is determined by opposite lateral incisor. oever, in some patients the contralateral incisor could be peg

14 • Aligner Orthodontics in Prerestorative Patients

shaped. If this is the case, management of spaces should be performed on the basis of surrounding teeth and tissue esthetics and function. he same approach should be used hen both lateral incisors are congenitally missing. he fundamental criteria for esthetic analysis should include facial, dentogingival, and dental esthetics.11 In recent years, several computer softare programs for digital smile design ( have been introduced to clinical practice and research. hey are multiuse conceptual tools that can strengthen diagnostic vision, improve communication, and enhance treatment predictability by permitting careful analysis of the patient’s facial and dental characteristics that may have been overlooed by clinical, photographic, or diagnostic cast-based evaluation procedures.1 ith today’s implant technology, assuming a .-mm lateral incisor implant, most surgeons ould probably be comfortable placing a maillary lateral incisor implant in a patient ith an interradicular space greater than . mm, leaving at least 1 mm of alveolar bone on either side of the implant. If the interradicular space ere less than  mm,

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many surgeons ould suggest orthodontic retreatment. herefore, speaing specically to minimiing the ris of root movement during retention that ould impede implant placement, Olsen and oich1 recommend leaving etra space for the surgeon (i.e., a minimum of . mm beteen the crons and . mm beteen the roots. his correlates ell ith the space traditionally suggested for implant placement of 1 mm on either side of the implant.

Case Study A -year-old female presented ith the chief complaint of an unaesthetic lateral prole due to protruded upper teeth, in addition to loer dental croding. he had a short face, an acute nasolabial angle, a mildly conve prole, and lip incompetence, ith class I canine and molar relationships and signicant overet and overbite (ig. 1.1. urthermore multiple restorations ere present. he panoramic radiograph conrmed that 1. as missing (ig. 1..

Fig. 14.1 Initial intraoral pictures showing multiple restorations.

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Fig. 14.2 Initial orthopantomograms.

his patient did not ish to change her facial esthetics but to merely improve the appearance of her anterior teeth. herefore the goals of esthetic interdisciplinary treatment ere to reduce the protrusive prole and obtain a class I canine occlusion, ith normal overet and overbite, by means of orthodontic treatment enhance dental esthetics and the smile line ith orthodontics and prosthetic restorations and replace the upper right lateral incisor ith an implant. rior to clear aligner treatment, the dental bridge from the upper right canine to the upper left lateral incisor as sectioned and polyvinyl siloane ( impressions ere taen. Clear aligner treatment in the upper arch as designed to intrude and retract the anterior teeth, supported by class II elastics to bonded buttons on the upper canines and loer rst molars. In the loer arch, intrusion and

proclination of the anterior teeth ere planned. A temporary resin pontic replaced the missing upper right lateral incisor during aligner treatment (igs. 1., 1., and 1.. At the conclusion of 1 months of aligner treatment, the severe overet and overbite ere improved, and the original vertical dimension as unaltered. An upper right lateral incisor implant as placed, folloed by nal esthetic restorations (igs. 1., 1., and 1..

Space Management in the Posterior Region he mesial tipping of mandibular second molars is a freuent source of reuest for orthodontic intervention by restorative dentists. Inadeuate mandibular arch length,

14 • Aligner Orthodontics in Prerestorative Patients

Fig. 14.3 Clear aligner treatment with attachments and buttons was started. The upper front xed restoration was sectioned prior the orthodontic treatment start. Class II elastics anchored on upper canines and lower rst molars were used to reinforce canine class I relationship.

Fig. 14.4 An implant was placed in . area. Continued

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Fig. 14.4, cont’d

A

B Fig. 14.5 rontal view of . implant with A and without B aligner.

Fig. 14.6 rontal view of the nal upper anterior restoration.

14 • Aligner Orthodontics in Prerestorative Patients

Fig. 14.7 inal intraoral pictures.

Fig. 14.8 inal extraoral pictures and xras. Continued

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Fig. 14.8, cont’d

ecessive teeth sie, loss of the adacent rst molar, premature eruption of the mandibular third molar, and unusually mesial eruption pathay of the second molar can also cause its partial or total impaction.1 achrisson1 stated that in case of severe mesial tipping of loer second molars, periodontal status can be aggravated, ith angular bone loss, and an apparent pocet at the mesial surface of a tipped mandibular molar. In ecessive inclination cases, overeruption of the antagonist molar ith subseuent premature contacts and occlusal interferences hamper prosthetic intervention. epositioning of the second molar eliminates pathologic condition and facilitates the placement of a prosthetic restoration. Among the limitations of aligners, severely tipped teeth (. degrees ere included.1 prighting a severe mesial tipped molar using aligners could be uite risy since the tting loss could produce a orsening of the mesial tipping. As ell described by renia,1 if the tooth is not performing the desired movement, the aligner ill surrender to the stiffer teeth and become distorted. Its gingival edges move aay from the teeth, and no force can be eerted in the gingival area hile the force is concentrated only in the occlusal part. his distortion prevents any possible couple to be developed, and no bodily movement of the tooth is possible. his occlusal force encourages intrusion that, for a severe mesial tipped molar, means orsening of its tipping. herefore hen planning, uprighting of molars ith aligners is preferable to reduce the velocity of the angular movement and to accurately control the tting of

aligners at every appointment (igs. 1. through 1.. he intrusion effect and thus the orsening of the mesial tipping could be accelerated if a large attachment has been displayed on the buccal surface of the molar and if the aligner is losing tting. Attachments are helpful especially in those cases ith rounded shape teeth but close controls in the ofce are reuired. o increase the efciency of the uprighting mechanics and to increase the stiffness of the aligner, pontics mesially to the tipped teeth should be avoided. ontics are euivalent to loops bent on an archire. hey increase elasticity and then a potential undesired distortion of the aligner if it is going to lose tting. he use of temporary anchorage devices (As can support the uprighting of severe mesially tipped molars. or this instance, cutouts should be planned on the aligner portion covering the tipped teeth to permit the placement of bonded buttons or bracets or tubes on the tooth cron, hich can be connected ith sectional mechanics or elastic moduli to As. A systematic revie indicated mandibular molar uprighting as a freuent and complicated procedure, hich reuires good anchorage control.1 ven a small amount of anchorage loss can result in aligner distortion ith adverse effects, not only on the moving tooth but also on other tooth units. he introduction of As as anchorage control auiliaries as a “game changer” in orthodontics, maing, among others as discussed in other chapters of this boo, molar uprighting easier and reliable ith aligner orthodontics.

14 • Aligner Orthodontics in Prerestorative Patients

Fig. 14.9 Initial orthopantomogram of a patient for which a prerestorative orthodontic treatment was reuired. . and . were congenitall missing. The interdisciplinar treatment plan was designed to recover a proper interarch relationship and preparing the case for future restorations on upper front teeth and in the lower arch after the uprighting of . and intrusion of overerupted ..

Fig. 14.10 Initial intraoral and ClinChec lateral views in relation to the mesial tipping of . caused b the premature loss of ..

Fig. 14.11 Initial intraoral and ClinChec occlusal views in relation to the mesial tipping of ..

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Fig. 14.12 Attachment conguration used to recover a proper alignment and leveling of the arches and the uprighting of .. Pontic was not prescribed in . area to increase the stiffness of the aligner.

Fig. 14.13 inal intraoral and ClinChec lateral views with successful uprighting of ..

Fig. 14.14 inal intraoral and ClinChec occlusal views with successful uprighting of ..

14 • Aligner Orthodontics in Prerestorative Patients

Fig. 14.15 Initial intraoral and ClinChec lateral views in relation to the overeruption of . caused b the pre mature loss of ..

Fig. 14.16 Initial intraoral and ClinChec occlusal views of the upper arch.

Fig. 14.17 Attachment conguration used to recover a proper alignment and leveling of the arches.

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Fig. 14.18 inal lateral intraoral and ClinChec views of the right side showing intrusion and leveling of . obtained with the aid of a buccal miniscrew and a segmented auxiliar arch bonded on . and . after proper modication of the aligners. Intrusion of . was planned to level gingival edge to the . one. An implant was placed in . area during the nal stages of the orthodontic treatment.

Fig. 14.19 inal intraoral and ClinChec occlusal views of the upper arch.

Fig. 14.20 inal orthopantomogram.

14 • Aligner Orthodontics in Prerestorative Patients

Management of Posterior ererupted Moars It is common for adult patients ith dental loss, particularly of molars and premolars, to have an etrusion of the antagonist. An early loss of any molar is bound to cause supraeruption of the opposing molar into the available space. Overeruption of such a molar can lead to occlusal interference and functional disturbances and cause great difculty during prosthetic reconstruction.1 Orthodontic treatment of overerupted molars has alays been considered challenging by orthodontists, even more hen considering aligner treatment. his is primary due to the great volume of these teeth and to the need for ecellent anchorage control to have the reuired forces directed through the center of resistance of the tooth. urthermore molar intrusion is one of the less predictable movements to be performed ith aligners. According to a recent paper, posterior intrusion could be taen into account ith aligners if a maimum .- to 1-mm molar intrusion has been planned.1 In these cases, the use of As along ith orthodontic biomechanics incorporated into the aligner treatment plan is used to obtain better case control hile minimiing unanted side effects. o avoid tipping of the molar that should be intruded, forces need to be applied both buccally and lingually, and interproimal spaces are reuired to obtain intrusion. herefore, hen planning the mechanics reuired to obtain intrusion of an overerupted molar ith aligners, it is important to have interproimal spaces open to permit the intrusion movement, planning interproimal reduction and controlling that at every stage of movement the tooth has no interproimal friction. Attachments should be prescribed on adacent teeth to provide anchorage (rectangular and horiontal attachments but not on the tooth reuiring intrusion. oever, if the tooth reuiring intrusion is the most distal one, then a buccal attachment should be placed. As can be of help in increasing the amount of molar intrusion over the maimum value of predictability ith aligners only (see igs. 1. through 1.. o miniimplants can be installed on each side, one buccally and another palatally, to have more controlled movement and to mae it less comple for the professional, ith more predictable results.1 or pure intrusion, a total of three miniimplants could be used in a tooth, in agreement ith accini et al. he seletal anchorage can be used connecting it to buttons bonded on the tooth cron ith elastic chains or ii coils, and, in this case, cutouts should be planned on the aligner. Another option could be represented by the use of elastic chains or other elastic modulus connecting the palatal and buccal miniscres, passing over the occlusal surface of the aligner. A nite element study investigating the use of As for molar intrusion shoed that unilateral force unleashed higher stress in root ape and higher evidence for dental tipping directed to mini-implant sites the bilateral force promoted a more homogeneous stress distribution ithout evidence of dental tipping. ilateral intrusion techniue suggested a vertical movement of intrusion and loer probability of root ape resorption.1

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Management of Patients With a History of Temporomandiuar isorders emporomandibular disorders (s are a group of musculoseletal and neuromuscular conditions involving the temporomandibular oints (s, the masticatory muscles, and associated tissues. Current understanding and evidence-based literature failed to demonstrate a relationship beteen various occlusal factors and  signs and symptoms.  has moved from a dental and mechanicalbased model to a biopsychosocial and medical model that integrates a host of biologic, behavioral, and social factors to the onset, maintenance, and progression of . anagement of  is typically symptomatic, aimed at decreasing pain, decreasing loading on the muscles and oints, and facilitating the restoration of function and uality of life of patients. Orthodontics is generally described as neutral in that it neither causes, cures, nor mitigates . ome early case reports shoed for some patients treated ith aligners, a muscle tenderness and ear facets on their aligners. everal clinicians speculated about the ear facets concluding that aligners may have acted as occlusal splints. A more credible hypothesis is related to an adaptation mechanism involving repetitive tooth clenching. erhaps it is possible that patients are triggered to clench on the aligners to alleviate orthodontic pain. As previously reported, orthodontic pain can be reduced by repetitive cheing of gum or plastic afers during the rst  hours after the appliance is activated. Aligner cheing and clenching can result in ear facets and muscle tenderness in some patients treated ith aligners. herefore it is a possibility that patients undergoing clear aligner treatment may have transient symptoms of facial muscular pain and  as a result of repetitive clenching to relieve orthodontic pain.  his is the reason hy aligners should not be used in patients ith active s. As a general rule,  needs to be managed before starting any orthodontic treatment. reatment should address not only the physical diagnosis but also the psychologic distress and the psychosocial dysfunction. he rst stage in  treatment is symptom focused and behavioral, and it includes (as determined by the problem list patient education, physiotherapy, pharmacotherapy, psychologic therapy (e.g., cognitive behavioral therapy, stress management, and self-regulatory sills, control of overuse behaviors, and intraoral  appliances. Only once symptoms have been controlled and ith the aareness that s are cyclic in nature (therefore ith a proper informed consent available, an orthodontic treatment can be planned. he folloing case is helpful in eplaining a possible aligner orthodontics approach to a  patient after a rst conservative phase and pain relief.

DIAGNOSIS AND TRATNT AN he reasons hy aligners could be used to move teeth orthodontically in a patient ith a history of  are represented by the possibility of accurately planning the seuence of movements, thus reducing and preventing

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phases in hich premature contacts can trigger the occlusal hypervigilance of some patients and by the possibility of using the aligners as physical pro memoria to help the patient to avoid clenching and gnashing of the teeth at least during the aae part of the day. ince the possibility of involuntary clenching or gnashing to alleviate orthodontic pain has been described, the orthodontic treatment plan should consider small amounts of movement from the very early stages of treatment to reduce orthodontic pain as much as possible.

Case Study A -year-old female patient presented ith anterior open bite, shift of the loer midline and of the mandible toard the left side, canine class II on the left side, and canine class I on the right side. urthermore diastemas ere present in the loer arch, and posterior ed prosthodontic restorations ere present (ig. 1.1. he patient had a history of

 ith headaches in the temple region, nec pain, and bac. All these symptoms ere controlled ith physiotherapy, cognitive behavioral therapy, and pharmacotherapy only once the pain as relieved as the treatment plan designed. he panoramic -ray highlighted the presence of interproimal spaces in the loer arch and the missing of both loer rst molars ith conseuent installation of bridges (ig. 1.. A  cone-beam computed tomography (CC scan highlighted a protruded position of the right condyle (ig. 1.. he first step of the interdisciplinary treatment consisted in the substitution of the old prosthetic restorations ith provisional ones built in a stabilied mandible position thans to a repositioning splint built by the prosthodontist in centric relation (igs. 1., 1., and 1.. Once the provisional bridges ere ed, an intraoral scan as performed to start aligner treatment. he virtual treatment plan is illustrated in igs. 1. and 1.

Fig. 14.21 Initial intraoral pictures.

14 • Aligner Orthodontics in Prerestorative Patients

Fig. 14.22 Initial extraoral pictures and orthopantomogram.

Fig. 14.23 Initial conebeam computed tomograph scans highlighting the asmmetric condles position.

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Fig. 14.24 ower occlusal splint.

Fig. 14.25 Conebeam computed tomograph scans showing condle repositioning due to the splint effect.

Fig. 14.26 Acrlic provisionals used to eep the new mandible position during the orthodontic treatment.

14 • Aligner Orthodontics in Prerestorative Patients

Fig. 14.26, cont’d

Fig. 14.27 Initial stage of the ClinChec.

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Fig. 14.28 inal stage of the rst ClinChec.

A phase I treatment as planned ith  aligners and concluded in  months ith a -day aligner change regimen (supported by additional vibrational forces ith Acceleent Aura, OrthoAccel Inc., ellair, , A. ig. 1. illustrates the intraoral situation at the end of phase I. o complete the orthodontic treatment, the pontic sections of the loer left and right bridges ere cut and a ne intraoral scan as performed to design the biomechanics reuired for the nal phase of the

orthodontic treatment. hen  aligners ere planned and a - to -day aligner change regimen as applied to close the treatment in 1 months. Additional vibrational forces ere used in this phase, too (igs. 1. and 1.1. pace for the installation of a rst molar implant as secured (igs. 1. and 1.. inal pictures sho the alignment of the midlines and the set of a functional occlusion ith good esthetic results (igs. 1. and 1..

14 • Aligner Orthodontics in Prerestorative Patients

Fig. 14.29 Intraoral pictures at the end of the rst set of aligners.

A

B Fig. 14.30 A ateral and B posteroanterior xras at the end of the rst set of aligners.

185

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Principles and Biomechanics of Aligner Treatment

Fig. 14.31 Intraoral pictures at the end of the second set of aligners.

Fig. 14.32 inal stage of the second ClinChec.

14 • Aligner Orthodontics in Prerestorative Patients

A

187

B Fig. 14.33 A inal orthopantomogram and B lateral xra.

Fig. 14.34 Intraoral pictures showing the lower implants and the nal prosthodontic restorations. Continued

188

Principles and Biomechanics of Aligner Treatment

Fig. 14.34, cont’d

Fig. 14.35 inal extraoral pictures.

14 • Aligner Orthodontics in Prerestorative Patients

References 1. American Association of Orthodontists. Adult orthodontics. https .aaoinfo.orgadult-orthodontics. Accessed ebruary , 1. . attrass C, andy . Adult orthodontics a revie. r J Orthod. 11-. . amdan A. he relationship beteen patient, parent and clinician perceived need and normative orthodontic treatment need. Eur J Orthod. -1. . osney . An investigation some of the factors in©uencing the desire for orthodontic treatment. r J Orthod. 11-. . arrini , ossini , Castro©orio , et al. aypeople’s perceptions of frontal smile esthetics a systematic revie. A J Orthod Dentofacial Orthop. 11-. . oich , pear . uidelines for managing the orthodonticrestorative patient. ein Orthod. 1-. . anama . he lin beteen orthodontics and prosthetics. In elsen , ed. Adult Orthodontics. Chichester,  lacell ub td 1. . de Avila É, de olon , de Assis ollo r , et al. ultidisciplinary approach for the aesthetic treatment of maillary lateral incisors agenesis thining about implants Oral urg Oral Med Oral Pathol Oral Radiol. 111(e-e. . oich . aillary lateral incisor implants planning ith the aid of orthodontics. Te Dent J. 1-. 1. amoto , lasalic . A customied staging procedure to improve the predictability of space closure ith seuential aligners. J Clin Orthod. 1-. 11. agne , elser . atural oral esthetics. In onded Porcelain Resto rations in the Anterior Dentition A ioietic Approach. 1st ed. unitessence ub 1-. 1. Coachman C, Calamita . igital smile design a tool for treatment planning and communication in esthetic dentistry. uintessence Dent Technol. 11-111. 1. Olsen , oich r . ostorthodontic root approimation after opening space for maillary lateral incisor implants. A J Orthod Dentofacial Orthop. 111.e1 discussion 1-1. 1. agavali-ria , mmanouilidis , apadopoulos A. andibular molar uprighting using orthodontic miniscre implants a systematic revie. Prog Orthod. 111. 1. achrisson , antleon . Optimal mechanics for mandibular molar uprighting. orld J Orthod. -.

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1. han , ing . Clinical limitations of Invisalign. J Can Dent Assoc. -. 1. renia . he clear plastic appliance a biomechanical point of vie. Angle Orthod. 1-. 1. affarel I, eira , uimarães , et al. iomechanics for orthodontic intrusion of severely etruded maillary molars for functional prosthetic rehabilitation. Case Rep Dent. 111. 1. eir . Clear aligners in orthodontic treatment. Aust Dent J. 1(suppl 1-. . accini , Cotrim-erreira A, erreira , et al. fciency of to protocols for maillary molar intrusion ith mini-implants. Dental Press J Orthod. 11-. 1. ugii , arreto C, rancisco ieira-únior , et al. truded upper rst molar intrusion comparison beteen unilateral and bilateral miniscre anchorage. Dental Press J Orthod. 1 -. . andasamy , inchuse . Orthodontics and . In andasamy , reene C, inchuse , et al., eds. TMD and Orthodontics. A Clinical Guide for the Orthodontist. pringer ub 11-. . anfredini , tellini , racco A, et al. Orthodontics is temporomandibular disorder-neutral. Angle Orthod. 1-. . oyd . sthetic orthodontic treatment using the Invisalign appliance for moderate to comple malocclusions. J Dent Educ.  -. . chupp , aubrich , eumann I. Invisalign treatment of patients ith craniomandibular disorders. Int Orthod. 1-. . ran , ou , ebiolo , et al. Impact of clear aligner therapy on tooth pain and masticatory muscle soreness. J Oral Rehabil. 11-1. . ou , ran , Castro©orio , et al. valuation of masticatory muscle response to clear aligner therapy using ambulatory electromyographic recording. A J Orthod Dentofacial Orthop. 11 e-e. . Ohrbach . isability assessment in temporomandibular disorders and masticatory system rehabilitation. J Oral Rehabil. 1-. . reene C, inchuse , andasamy , et al. anagement of  signs and symptoms in the orthodontic practice. In andasamy , reene C, inchuse , et al., eds. TMD and Orthodontics. A Clinical Guide for the Orthodontist. pringer ub 111-1. . iancotti A, ermano , ui , et al. A miniscre-supported intrusion auiliary for open-bite treatment ith Invisalign. J Clin Orthod. 1-.

15

Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions BENEDICT WILMES and JÖRG SCHWARZE

Upper Molar Distalization in Aligner Treatment The distalization of the upper molars may be considered as a treatment option for patients with an angle class II malocclusion characterized with an increased overjet and/or anterior crowding. There has been an increasing trend in the clinical use of purely intraoral appliances, which require minimal need for patient cooperation. nfortunately, most tooth-borne appliances for upper molar distalization produce an unwanted side effect of anchorage loss resulting in maillary incisor proclination, reported to be  to  of observed tooth movement. ure bodily tooth movement with sequential plastic aligner therapy is challenging to achieve to a high degree of predictability. s a consequence, molar distalization is limited when relying on aligner movement alone. hile there are limited reports of successful upper molar distalization of up to . mm in the literature, a very long treatment time and high level of patient compliance are epected with requirement for intermaillary class II elastics to be worn during the long period of the sequential upper molar distalization. oreover, the potential side effects of class II elastics must be considered in terms of mesial shift of the lower anchorage teeth. To minimize anchorage loss and need for class II elastics, mini-implants have been incorporated into the design of maillary distalization appliances.  ini-implants can be positioned intraorally with minimal degrees of surgical invasiveness, are readily integrated with concomitant biomechanical initiatives, and are relatively cost effective.- arious designs of implant supported distalization appliances have been published. The retromolar region is an unsuitable area for mini-implant insertion due to the unfavorable anatomic conditions poor bone quality and thic soft tissue. dditionally, the alveolar process has also been shown to be inappropriate in cases of a desired molar distalization since the mini-implants are in the direct path of the moving teeth resulting in a failure rate that is much higher as compared to the anterior palate. Therefore, the palatal area posterior from the rugae T zone seems to be the preferred insertion site for mini-implants where the treatment objective is for distal movement of the maillary molars without associated anchorage loss and maillary incisor displacement. urthermore, good bone quality with 190

thin attached mucosa implies minimal ris of tooth-root injuries and a very high success rate in the anterior palatal region. In contrast to treatment strategies involving the interradicular positioning of mini-implants, the molar teeth can be distalized, and the premolars are free to move distally due to the stretch of the interdental bers without any interference since the palatally positioned miniimplants are not in the path of moving teeth. ithin the T zone, the mini-implants can be inserted in a median or paramedian orientation, with both insertion sites showing a similar stability.

Clinical Procedure and Rational of the Beneslider The eneslider- is a maillary molar tooth distalization appliance, principally designed on the use of one or two mini-implants coupled in a median or paramedian orientation in the anterior palate ig. .. y modifying the angulation of the .-mm stainless steel wire, it is possible to achieve a simultaneous intrusion or etrusion of the molars.- The distalization forces are transferred to the molars by the use of bonded tubes. The advantages of a bonded tube are esthetics, and the adaptability and t of the aligners is not undermined by the presence of stainless steel molar bands. The aligner material could cover this bonded connection ig. . or the aligner could be cut out in this connection area “button cutout” ig. .. It seems advantageous that the eneslider appliance can be tted directly without the requirement for adjunctive laboratory wor in terms of welding or soldering, or the need to record an intraoral impression. lternatively, the clinician has the choice to record an intraoral impression and transfer the clinical setup to a plaster cast model using an impression cap and laboratory analogue from the enet system. ollowing distalization of the maillary molar teeth, steel ligatures can be used see ig. . or springs removed see ig. . to modify the eneslider from an active distalization device to a passive molar anchorage device. The primary objective is to stabilize the maillary molar teeth during the retraction of the maillary anterior teeth. ur eperience in using the eneslider appliance in conjunction with aligners commenced with a two-phase approach

15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions

Fig. 15.1 The Beneslider appliance is based on one or two miniimplants with echangeable abutments

191

the initial phase involving molar distalization and the secondary phase for the nal detailing of the occlusion with sequential thermoplastic aligners. ith a two-phase approach, an impression or scan is recorded after distalization. To reduce the total treatment time, we now recommend simultaneous distalization with the eneslider and alignment with sequential aligners. ith a single-phase approach, the impressions for aligners are taen prior to distalization of the maillary molars, and the anticipated tooth movement to be produced by the eneslider appliance is programmed in the digital software platform. or distalization, either a sequential step-by-step distalization or an entire maillary arch can be chosen since the stretch of the interdental bers supports the simultaneous distal drift of maillary anterior teeth. If the aligner material should cover the connection area with the molars see ig. ., the impressions for aligners should be done after the insertion of the eneslider appliance. The eneslider should be not activated prior to the delivery of the aligners. If the aligners have a cutout area see ig. ., the impressions for aligners are able to be recorded either before or after insertion of the eneslider appliance. istalization forces can be applied to the rst or second maillary molar teeth. ur clinical eperiences have shown that force application to the rst molar is a superior approach, as direct force application to the second molar teeth is associated with precocious distalization of the second molars, leading to improper tracing and tting of the sequential plastic aligners, a ris that is reduced if the maillary rst molar teeth are connected to the eneslider.

Clinical Case Fig. 15.2 The aligners can coer the bonded connection lie a big attachment After distalization steel ligatures are to modif the actie Beneslider into a passie anchorage deice

Fig. 15.3 The aligners can be cut out in this connection area “button cutout” prings are remoed in this case to modif the actie Beneslider into a passie anchorage deice

 -year-old female patient presented with anterior crowding class II malocclusion ig. . Table .. The maillary teeth were migrated mesially, especially on the left side. ue to the absence of the second lower right molar, the upper second right molar was elongated. The patient was very unhappy with the protrusion of the upper front teeth and specically requested an invisible orthodontic treatment option to be performed on a nonetraction basis. ollowing the insertion of two enet mini-implants in the anterior palate ig. ., the eneslider appliance was passively installed see ig. . note springs are not activated. ith the goal to distalize and intrude the upper right second molar simultaneously, the guiding wire of the eneslider was angulated apically see ig. .. econdly, intraoral scans were recorded for fabrication of clear aligners Invisalign, lign Technology, Inc.. sing the aligner planning software e.g., linhec, the molar movements have to be planned parallel to the guiding wires of the eneslider, including the intrusive vertical component in the rst quadrant. uring the distalization period, molar derotations and uprighting movements were not allowed see ig. .. In this patient, a sequential distalization was chosen. The aligner material should cover the connection area ig. .. fter delivery and insertion of the aligners, the eneslider was activated by pushing the -g iTi springs distally using the activation loc see ig. .. The maillary molars were to be distalized

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Fig. 15.4 A -ear-old female patient with an angle class II malocclusion characterized b anterior crowding and a deep bite

15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions

Fig. 15.4, cont’d

Tale 151 Cephalometric ummar

NBa

Pretreatment

Posttreatment

°

°

N-N

°

°

M-N

°

°

M-N

°

°

NA

°

°

NB

°

°

ANB

°

°

its

 mm

 mm

U-N

°

-M

°

° °

U-

°

°

eret

 mm

 mm

erbite

 mm

 mm

193

194

rinciples and Biomechanics of Aligner Treatment

A

B

C Fig. 15.5 After insertion of two Benet mini-implants in the anterior palate A and installation of the Beneslider mechanics B uperimposition of an intraoral picture of the maillar arch and the ClinChec to demonstrate desired tooth moement directions C

Fig. 15.6 Beneslider was actiated b pushing open springs distall after delier of the aligners Connection areas of the Beneslider with the molars are coered b the aligner “big attachment”

approimately  to  mm. The patient reportedly adapted to the appliance without issue. The panoramic radiograph denotes bodily distalization of all maillary posterior teeth after  months ig. .. uring the follow-up controls, molar distalization is visible with small spaces between molars and bicuspids igs. ., ., ., and . note sequential distalization. s soon as the maillary molar teeth were distalized into an angle class I occlusion, steel ligatures were used between the bonded tube and the activation loc to deactivate the eneslider ig. . see igs. . and .. The eneslider was converted from a distalization device to a molar anchorage device. fter all spaces were closed to the distal, the eneslider was removed and scans for a renement and molar derotation were recorded. omprehensive treatment was completed after  months, and the palatal mini-implants were removed without the adjunctive use of local anesthesia ig. .. pper incisors were reclined signicantly - has changed from . to

15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions

Fig. 15.7 adiographs after  months of treatment rtopantomograph and lateral -ra after  months of treatment

Fig. 15.8 Intraoral pictures after  months

195

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rinciples and Biomechanics of Aligner Treatment

Fig. 15.9 Intraoral pictures after  months showing man small spaces due to the semiseuential distalization

Fig. 15.10 Intraoral pictures after  months Molars are distalized in a Class I occlusion The Beneslider is modied into a molar anchorage deice b two steel ligatures which are deactiating the Beneslider rom this moment bicuspid canine and incisor retractions are following

15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions

Fig. 15.10, cont’d

Fig. 15.11 Intraoral pictures after  months Continued

197

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rinciples and Biomechanics of Aligner Treatment

Fig. 15.11, cont’d

Fig. 15.12 Upper arch after  months All spaces were to be closed to the distal ubseuentl the Beneslider was remoed for renement

Fig. 15.13 Treatment result after  months

15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions

Fig. 15.13, cont’d

199

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rinciples and Biomechanics of Aligner Treatment

Fig. 15.14 uperimposition of before and after cephalograms -N Upper incisor retraction is signicant

. degrees ig. ., and the patient was very happy with the achieved result.

Clinical Considerations or distalization, either a sequential step-by-step distalization or an entire maillary arch can be chosen. In this case, a sequential distalization was chosen. The advantage of sequential distalization is the aligner tting is probably better because all teeth are enclosed by aligner material, and therefore bodily retractions of bicuspids and canines can be achieved easier. isadvantage is the longer treatment time, which is visible in the case shown in this chapter. ur initial approach to combine aligner therapy and the eneslider appliance involved a two-phase protocol  distalization, and after distalization of the maillary molar,  impression/scan and nishing with aligners. dvantages of this two-phase procedure are as follows n

n

o need for coordination of tooth movement with eneslider and aligners n epected requirement for fewer aligners to achieve treatment objectives  disadvantage of the two-phase procedure is

n

n epected increased treatment time

The potential drawbac of the one-phase method is the coordination between the eneslider appliance and planned aligner tooth movements. If the distalization force and/or the rate of distal molar movement are ecessive compared to the aligner staging, the t and accuracy of the aligner may be undermined with the appearance of maillary interdental spacing.  second factor to be considered is the possibility of insufcient aligner wear by the patient. If this is recognized during active treatment, the rate of distalization may be reduced or the wear time of on aligner

may be prolonged e.g., wearing each aligner for  wees instead of one. The rate of the maillary molar distal movement associated with the use of a eneslider appliance is approimately . mm per month this rate of molar distalization speed should be ept in mind when determining the appropriate aligner staging linhec. The distalization force can be directly applied to the rst or second molar teeth. To achieve a maimum retention with the teeth that are to be moved distally, we recommend bonding the eneslider to the rst molar teeth instead of the second molars. If the distalization forces are applied to the second molars and the aligner tting at the second molars is not perfect, small unepected spaces can develop in between the upper rst and second molar teeth. In this situation, the distalization force must be reduced to regain aligner tting. The anterior palate has proven to be the most convenient region of the mailla for insertion of mini-implants.  ince there are no roots, blood vessels, or nerves, the ris of a complication associated with the placement of a miniimplant is minimal. ven the penetration of the nasal cavity does not result in any problems. ecently, a /manufactured insertion guide was introduced asy river, arma, Italy, which facilitates safe and precise insertion of mini-implants in the anterior hard palate, availing the opportunity for the use of palatal implants to the less eperienced clinician. econdly, these insertion guides allow for the insertion of mini-implants and installation of the appliance in a single ofce visit.

Conclusions n

n

n

y using palatal mini-implants and a eneslider device, unilateral or bilateral distal tooth movement can be realized without anchorage loss and need for class II elastics. The eneslider can be easily integrated in aligner therapy by using bonded tubes on the palatal surfaces.  combined, single-phase treatment approach with simultaneous distalization and alignment is possible.

References . ortini , upoli , iuntoli , et al. entoseletal effects induced by rapid molar distalization with the rst class appliance. Am J Orthod Dentofacial Orthop. - discussion -. . imon , eilig , chwarze , et al. orces and moments generated by removable thermoplastic aligners incisor torque, premolar derotation, and molar distalization. Am J Orthod Dentofacial Orthop. -. . imon , eilig , chwarze , et al. Treatment outcome and efcacy of an aligner technique—regarding incisor torque, premolar derotation and molar distalization. BMC Oral Health. . . inzinger , ulden , ildizhan , et al. nchorage efcacy of palatally-inserted miniscrews in molar distalization with a periodontally/ miniscrew-anchored distal jet. J Orofac Orthop. -. . aboud , ad , bbott , et al. earch for dar matter at ormula see tet in nal states containing an energetic photon and large missing transverse momentum with the T detector. Eur Phys J C Part Fields. . . osta , affaini , elsen . iniscrews as orthodontic anchorage a preliminary report. Int J Adult Orthodon Orthognath urg.  -. . anomi . ini-implant for orthodontic anchorage. J Clin Orthod. -.

15 • Noncompliance Upper Molar Distalization and Aligner Treatment for Correction of Class II Malocclusions

. elsen , osta . Immediate loading of implants used for orthodontic anchorage. Clin Orthod es. -. . udwig , lasl , owman , et al. natomical guidelines for miniscrew insertion palatal sites. J Clin Orthod. -. . ourfar , ister , anavais , et al. Inªuence of interradicular and palatal placement of orthodontic mini-implants on the success survival rate. Head Face Med. . . ilmes , udwig , asudavan , et al. The T-zone median vs. paramedian insertion of palatal mini-implants. J Clin Orthod. -. . ienemper , auls , udwig , et al. tability of paramedian inserted palatal mini-implants at the initial healing period a controlled clinical study. Clin Oral Implants es. -. . ilmes , rescher .  miniscrew system with interchangeable abutments. J Clin Orthod. - quiz . . ilmes , rescher , ienemper .  miniplate system for improved stability of seletal anchorage. J Clin Orthod.  -.

201

. ilmes , rescher . pplication and effectiveness of the eneslider molar distalization device. orld J Orthod. -. . ilmes , ienemper , udwig , et al. sthetic class II treatment with the eneslider and aligners. J Clin Orthod. -. . ilmes , euschulz , afar , et al. rotocols for combining the eneslider with lingual appliances in class II treatment. J Clin Orthod. -. . ilmes , atyal , illmann , et al. ini-implant-anchored esialslider for simultaneous mesialisation and intrusion of upper molars in an anterior open bite case a three-year follow-up. Aust Orthod J. -. . ienemper , ilmes , auls , et al. Treatment efciency of mini-implant-borne distalization depending on age and secondmolar eruption. J Orofac Orthop. -. . e abriele , allatana , iva , et al. The easy driver for placement of palatal mini-implants and a maillary epander in a single appointment. J Clin Orthod. -.

16

Clear Aligner Orthodontic Treatment of Patients with Periodontitis TOMMASO CASTROFLORIO, EDOARDO MANTOVANI, and KAMY MALEKIAN

Malocclusions Related to Periodontal Disease There is no direct inuence between malocclusion and periodontal breakdown; however, quicker progression of periodontal disease is associated with occlusal discrepancies and is reduced by occlusal treatment.1, t has been demonstrated that in crowded areas plaque accumulation increases and, with respect to noncrowded areas, an increased number of periopathogenic species can be found. urthermore, an altered topography of the gingiva and the alveolar bone is commonly found when teeth are crowded. There is a strict relationship between crowding and periodontitis because anterior teeth migration is enhanced by periodontal disease, leading to a further crowding in lower arch, which then hinders a proper periodontal health. anavi demonstrated that deep bite is directly related to periodontal breakdown due to soft tissue impingement on the upper and lower incisors ig. 1.1. urthermore, multiple types of occlusal contacts have been associated with deeper probing depths premature contacts in centric relation, posterior protrusive contacts, balancing contacts, combined working and balancing contacts, and length of slide between centric relation and centric occlusion. nother correlation was found in mesially inclined molars where the periodontal destruction was 1 greater than that found in normally inclined teeth.

Orthodontic Treatment in Patients With Periodontal Disease rthodontics is needed in combination with periodontal and prosthodontic treatment to treat patients with a secondary malocclusion or in whom there is aggravation of an eisting malocclusion related to periodontal disease. espite the high number of published articles, there is still a lack of good evidence about many of the treatments, including orthodontics and periodontal therapy.1 The prevalence of pathologic tooth migration T among periodontal patients has been reported to range from . to .; periodontal bone loss appears to be the maor factor in the etiology of T.11 n a recent study, horshidi et al. found that pathologic migration prevalence was 11. 1 patients; however, there was no pathologic migration in patients with mild chronic periodontitis. T prevalence is increased by the severity of periodontal disease, and no statistically signicant difference between males and females was found.1 202

n early stages of T, spontaneous correction of migrated teeth sometimes occurs after periodontal therapy. hen only a light degree of pathologic migration is considered, it has been hypothesied that this is due to wound contraction during healing ig. 1..1 oft tissue forces of the tongue, cheeks, and lips are known to cause tooth movement and in some situations can cause T. The transseptal bers play a key role in T by forming a chain from tooth to tooth and helping maintain contacts between teeth. f the continuity of the chain is weakened by periodontal disease, the balance of forces is upset, and displacement of the teeth can occur ig. 1.. cclusal factors such as posterior bite collapse, shortened dental arches, occlusal interferences, and bruism are connected to the etiology of T. atients with periodontal issues are commonly characteried by general aring with spacing between the upper incisors, deepening of the bite sometimes etrusion of a single tooth can occur, increased overet, and crowding in the lower incisor region.1 nterposition of the lower lip behind the ared incisors can worsen the situation. n orthodontic treatment provided without a proper oral hygiene can result in iatrogenic damages oving a tooth into an infected infrabony defect can enhance the destruction of connective tissue.1 owever, a combined ortho-perio treatment is efcient in the treatment of periodontitis and could effectively decrease the levels of inammatory cytokines.1 urthermore, the treatment should aim for the patient’s epectations and aesthetic goals. rthodontic treatment can allow the optimiation of clinical situations1 such as n n n

eveling of bone peaks ringing a tooth back to the alveolar ridge mplant site preparation

rthodontic treatment is indicated when the worsening of periodontal status can be promoted by tooth malposition such as n n n

n

n

n

evere tooth crowding remature contacts evere deep bite associated with direct trauma on periodontal tissues esial inclination of molars associated with angular bony defect rthodontic treatment is mandatory when The periodontal disease has caused T and abnormal tooth mobility.  previous orthodontic therapy made with unskillfulness has created further periodontal tissue damage.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

Fig. 16.1 Pathologic tooth migration in an old man.

203

204

Principles and Biomechanics of Aligner Treatment

A

Granulation tissue Gingival enlargement Upper lip

B Tongue

Mastication Occlusal forces Lower lip

C

Habits Fig. 16.2 Pathologic tooth migration in a young woman. (A) Intraoral picture highlighting the tissue breadown. (B) traoral picture (please note the position of element .). (C) cheme representing tissue breadown. (rom Brunsold A. Pathologic tooth migration.  Periodontol. . doi.op.....)

A

B Fig. 16.3 Transseptal bers balance loss and pathologic tooth migration. (A) Scheme from Brnod MA ahooc ooh mraon (B) Occa e of he aen of re  J Periodontol  do o)

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

Preliminary discussion

Introduce complexity

Interest?

Comprehension Biology Risk benefit Cost

Therapeutic diagnosis

Hygiene response Control phase Compliance

205

between specialists is mandatory, and roundtable discussion is required to discuss complicated cases.1

PERIODONTAL ASSESSMENT ain concept orthodontic tooth movement without preeisting inammation. eriodontitis is characteried by microbially associated, host-mediated inammation that results in loss of periodontal attachment. The bacterial biolm formation initiates gingival inammation and promotes tissue breakdown Tables 1.1 and 1.. The primary goal is to eliminate periodontal disease and stabilie the dentition. The clinical and radiologic assessments of the periodontal situation are mandatory before treatment planning. ssessment also enables the identication of recessions, horiontal bone loss, and lesions such as crater defects one-, two-, and three-wall defects and furcation defects. imiting factors are

Interdisciplinary consultations Fig. 16.4 Preliminary ealuation of an orthoperio patient. (From Nanda R Esthetics and Biomechanics in Orthodontics nd ed S Lo, MO Eeer )

n n n

Diagnosis and Treatment Planning

n n

eriodontal pockets . mm laque inde and bleeding on probing .1 Thin-scalloped gingival biotype iabetes out of control moking .1day evere tooth mobility

PATIENT EXPECTATIONS

n

 very careful consideration of the patient’s chief complaint is due in order to clearly determine the patient’s needs and plan realistic treatment goals.1 These obectives generally should be economically, occlusally, periodontally, and restoratively realistic.1 The preliminary periodontal assessment is a fundamental screening process during which adherence to issues of home oral hygiene and regular appointment attendance is determined ig. 1..1

rior to orthodontic treatment, the following can be performed

MULTIDISCIPLINARY TEAM ince several skills and knowledge are needed to provide full treatment planning, in addition to a periodontist and an orthodontist, a restorative dentist, prosthodontist, and oral or maillofacial surgeon can be involved. The importance of the team approach in achieving the best possible results in the management of adult orthodontic patients with bone loss cannot be overstated. n this phase, good communication

n n n n n n

ral hygiene motivation rophylais or therapy to control inammation urgery to eliminate deep pockets ugmentation of attached gingiva renectomy limination of gingival clefts

t is mandatory that the orthodontist and periodontist discuss the management of periodontal issues and plan the correction. atients with a malocclusion may present with preeisting mucogingival problems or fragile periodontal support that is susceptible to attachment loss during or after orthodontic treatment ig. 1..  proper amount of attached gingiva is needed to dissipate the mechanical trauma induced by mastication and tooth brushing. f teeth are inside the alveolar ridge, predictable soft tissue grafting

Table 16.1 ramewor for taging and rading of Periodontitis IA IT A COPIT O AAT

Stage I: Initial Periodontitis idence or ris of rapid progression anticipated treat ment response and effects on systemic health

Stage II: Moderate Periodontitis

Stage III: Seere Periodontitis With Potential or dditional Tooth oss

rade A rade B rade C

Indiidual Stage and rade ssignment

Stage I: danced Periodontitis With tensie Tooth oss and Potential or oss o Dentition

206

Principles and Biomechanics of Aligner Treatment

Table 16. Periodontitis tage PRIODOTITIS ST Seerit

omleit

Stage I

Stage II

Stage III

Stage I

Interdental  at site o greatest loss

– mm

– mm

 mm

 mm

Radiograhic bone loss

Coronal third (,)

Coronal third (–)

tending to midthird of root and beyond

tending to midthird of root and beyond

Tooth loss

o tooth loss due to periodontitis

Tooth loss due to periodontitis # teeth

Tooth loss due to periodontitis of  teeth

ocal

aimum probing # mm ostly horiontal bone loss

In addition to stage II compleity Probing depth  mm ertical bone loss  mm urcation inolement class II and III oderate ridge defect

In addition to stage III compleity eed for comple rehabilitation due to asticatory dysfunction econdary occlusal trauma (tooth mobility ) eere ridge defect

aimum probing depth # mm ostly horiontal bone loss

Bite collapse drifting ¤aring , remaining teeth ( opposing pairs) tent and Distribution

dd to stage as descritor

or each stage describe etent as localied (, of teeth inoled) generalied or molarincisor patter

CAL, Cnca aachmen ee

Fig. 16.5 In this class II adult patient incisors are crowded etruded and proclined. oft and hard tissue grafting can be helpful before orthodontic treatment to preent the deelopment of recessions.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

207

Fig. 16.5, c’

procedures such as the subepithelial connective tissue graft T and the free gingival graft  may be performed prior to tooth movement to prevent gingival recession. n a systematic review, loukos et al. investigated the indication and timing of soft tissue augmentation in orthodontic patients. o randomied controlled trial was identied, and only limited data were available. urthermore, osseous defects cannot allow many adult patients to clean teeth adequately and require correction prior to or during orthodontic therapy. These osseous defects include interproimal craters; one-, two-, and three-wall defects; furcation defects; and horiontal defects. nterproimal craters are two-wall defects, where attachment loss occurs on the mesial and distal surfaces of the adacent roots and the remaining walls are the buccal and lingual ones. rthodontic movement cannot improve interproimal craters; if the crater is mild to moderate, then resective surgery and bone recontouring should be eecuted. n one-wall defects, there has been destruction of three of the four interproimal walls, leaving one wall remaining. These defects are difcult for a periodontist to manage because resection could be too destructive and regeneration is inappropriate. rthodontic eruption of the tooth can eliminate the defect associated with occlusal reduction.

Three-wall defects must be treated prior to orthodontics with regenerative therapy.  provisional splinting of the teeth undergoing periodontal surgery is needed to provide stabiliation. occuo et al. demonstrated that the enamel matri derivative  alone and in association with various grafts give the best results for the treatment of intrabony defects, with improvements in terms of clinical attachment level  gain and pocket depth  reduction. n this study, the orthodontic treatment was initiated  to 1 months after guided tissue regeneration T procedures and aimed at correcting malposition, creating contact points, and providing nontraumatic occlusion. ince the broblastic and osteoblastic turnover is necessary to heal the defect before moving the adacent teeth, the timing of orthodontic treatment after regenerative therapy is still debated.- an et al. recommended waiting to begin orthodontic therapy until at least  months after the completion of periodontal regenerative therapy to carry out the movement in fully healed sites. urcation defects are typically divided into three classications class 1, , or . lass 1 furcation defects are usually monitored during orthodontic therapy. lass  and  furcation defects should be treated by the periodontist before the orthodontic treatment to allow a proper hygiene.

20

Principles and Biomechanics of Aligner Treatment

ometimes, if the periodontal health of adacent teeth can be maintained, hopeless teeth are used during orthodontic treatment to provide anchorage and occlusal function for the patient. The orthodontist must evaluate the horiontal bone loss because there is an alteration of crownroot ratios. f horiontal bone loss has occurred in only one area, reduction of crown length will avoid the creation of bony defects between adacent teeth after leveling. uring orthodontic treatment, the following can be performed n

n

n

rophylais and plaque removal every month to control inammation urgical eposure of impacted teeth according to periodontal concepts ibrotomy every 1 days during forced eruption

fter orthodontic treatment, the following can be performed n n n n

upportive therapy linical crown lengthening ingivoplasty oot coverage

ORTODONTIC ASSESSMENT DETERMINATION OF FINAL OCCLUSION ental history in adult patients should not be overlooked and, along with restorative requirements, is a key factor in determining the nal occlusion.  specic evaluation of parafunctional habits, temporomandibular disorders, cracked teeth, and wear facets is mandatory Table 1.. articular focus is on the following n n

n n

Tooth movements within bone limits val-shaped roots buccolingual dimension wider than the mesiodistal dimension resence of fremitus valuation of tongue pressure

CONSIDERATIONS n n

valuate teeth with intact or reduced periodontal support. revent plaque buildup avoid ed appliances.

Table 16. Orthodontic oements And alocclusion eatures Issues

oals

Crowding

Alignment

laring

Closure of diastemas and retraction intrusion

Blac triangles

eshaping by interproimal reduction retraction intrusion

Bone peas and gingial margins need leeling

Intrusionetrusion

emoal of occlusal interference

etraction and intrusion selectie grinding

ornlost teeth

Prosthetic rehabilitationspace closure

Preention of relapse

etention

n n

void ecessive ridge epansion. void ecessive proclination.

very orthodontic tooth movement beyond the cortical plate should be avoided. ingival recessions can be related to ecessive epansions and movements outside the alveolar bone housing i.e., when an alveolar bone dehiscence has been created ig. 1.. anarsdall suggested that patients with a transverse skeletal maillomandibular discrepancy greater than  mm are susceptible to recessions, especially if palatal epansion is needed. ith the introduction of three-dimensional  imaging in orthodontics, a diagnosis in three planes of space can be obtained with relative ease and minimal radiation. n a recent study on adolescent patients, an evaluation using cone-beam computed tomography T scans before and after orthodontic alignment stated that bone thickness T decreased and height from the cementoenamel unction to the alveolar crest  increased signicantly for the incisors and mesiobuccal root of the rst molars. rch dimensions generally increased together with tipping, and epansion related to alignment resulted in horiontal and vertical bone loss at the incisors and mesiobuccal root of the rst molars. Thinner Ts and more severe crowding before treatment increased the risk for buccal bone loss. s etraction may worsen the soft tissue prole, especially in adult patients, protraction of the lower incisors is an alternative dealing with cases of lower crowding or increased overet.  benecial effect on the soft tissue prole through smoothing of the mentolabial sulcus can be achieved, but the optimal position of the lower incisors is still not clear. o association between proclination and gingival recession has been found by rtun and robéty, while others consider lower incisor proclination a risk. iedrich stated that the specic anatomy must be taken into consideration, such as the gingival health and the force system. The morphology of mandibular anterior alveolus differs in hypodivergent, hyperdivergent, and norm divergent patients, but the evaluation of symphysis morphology on cephalometric radiographs might not be a solid method aimed at predicting gingival recession in the anterior region of the mandible. The relationship between periodontal status of mandibular incisors and selected cephalometric parameters has recently been investigated the width of keratinied gingiva T was found to correlate with , T, and symphysis length, while gingival thickness T was associated with T and symphysis length. oth T and T are regarded as signicant risk factors for gingival recession. n a recent study, no higher occurrence of gingival recession in cases of pronounced proclination of lower incisors without violating the osseous envelope of the alveolar process has been found. t can be speculated that if the gingiva maintains appropriate thickness, it is more resistant and less affected by tension from large proclination.1 n a retrospective study, elsen found that gingival recession on mandibular incisors was not signicantly increased during orthodontic treatment. Thin gingival biotype, visual plaque, and inammation are useful predictors of gingival recession.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

20

Fig. 16.6 In this adult patient a preious ecessie orthodontic epansion promoted a gingial recession on teeth  and . The occlusal instability has led to orthodontic relapse.

Teeth can be moved with their surrounding periodontium when careful attention is paid to local anatomy and periodontal health. urthermore, tooth movement with or through bone can be provided using different force systems. hen an optimal oral hygiene has been achieved, it is possible to apply orthodontic forces, even if the periodontal tissue has reduced connective tissue attachment and alveolar bone height., Traditional ed orthodontic appliances induce microbial changes toward periodontopathogenic anaerobic bacteria because of the increased plaque accumulation. These effects are normalied after removal of orthodontic appliances without lasting detrimental effects, but in some patients there is a signicant risk for irreversible periodontal destruction. Thus the use of clear aligners that promote a better periodontal health when compared to ed appliances- may be the optimal choice in patients with periodontal involvement. ith clear aligners, it is possible for good control of oral hygiene throughout treatment, while the rst months with ed appliances are always difcult to manage.1 The forces and moments generated by aligners of the nvisalign system are always within the range of orthodontic forces. The forces and couples delivered by aligners are determined by the shape of the crown and the type and amount of displacement of the particular tooth and therefore the contacts between tooth and the inner surface of the appliance. Tipping movement is predictable with

thermoplastic appliances, but difculties about root control have been reported. ince the gingival margin of the aligner is elastic, it is not surprising that an aligner would have difculty controlling the forces applied in this region. The introduction of ower idges demonstrates that when a torque correction of about 1 degrees is required, torque loss is negligible. The force couple generated by a thermoplastic aligner torquing an upper incisor consists of a tipping force near the gingival margin and a resulting force produced by movement of the tooth against the opposite inner surface of the appliance, near the incisal edge. The undesirable mesial movement of rst molar compensation requires programmed forward mesial root rotation, in effect producing crown tipback rotation. n an in vitro study, imon et al. investigated the influence of auiliaries, such as attachments and ower idges, on performing root movements of upper central incisor torque.  loss of torque up to  must be considered; however, it must be noted that the efficacy of fied orthodontic appliances does not reach 1 either. onventional orthodontic brackets and wires do not completely fill the bracket slots so that the wire is able to twist, leading to a loss of moment known as torque play. The loss of torque between an arch of .1 3 . in. section usual sie for the final stages of orthodontic treatment and a . 3 . in. slot is about 1 degrees.

210

Principles and Biomechanics of Aligner Treatment

 more recent study stated that nvisalign is able to achieve predicted tooth positions with high accuracy in nonetraction cases. ombardo et al. stated that some tooth movements can be achieved with aligners more easily than others. n particular, vestibulolingual tipping and rotation reached . and . of the prescribed movement, respectively. n a retrospective study, fondrini et al. found no differences between aligners and brackets about buccolingual inclination control on upper incisors. These studies led to different conclusions probably because of the development and improvements in materials, technologies, and treatment protocols. everal factors are involved in determining successful tooth movement the attachment’s shape and position, the aligner’s material and thickness, the amount of activation present in each aligner, and the techniques used for the production of the aligners. Treatment outcomes depend also on the patient’s characteristics, bone density and morphology, crown and root morphology of teeth, as well as on factors related to the clinician such as the accuracy in performing the requested amount of interproimal reduction , which is usually underestimated. The plastic foil used for the fabrication is thinned out by thermoforming at the gingival edge of the aligners, thus representing the area where they are less rigid. urthermore, to avoid loss of anchorage, simultaneous movement of multiple teeth should not be performed. lanning clear aligner therapy T with virtual setup software facilitates choosing an appropriate number of anchor teeth and the proper sequence of tooth movement to minimie the risk of anchorage loss.1 owever, an aligner alone cannot provide proper anchorage control, especially in situations in which tooth morphology is not favorable i.e., small clinical crowns, reduced undercuts. To overcome clear aligner limitations, the development of effective attachments rectangular and vertical, for both anchorage management and better root control, is increasing. The use of conventional bulk-ll resins for the attachment creation leads to a higher precision. The  planning, especially when associated with T data, can allow a proper control; moreover, the velocity of movements can be selectively slow .1 mm g1 days.  T eamination is useful to evaluate the spatial position of the teeth within bone. They may be positioned off-ais and present radiographically with fenestrations and dehiscences. nticipated orthodontic treatment can improve tooth position in the bone so that mucogingival deciencies can be subsequently reevaluated ig. 1.. n periodontal patients there is interproimal bone loss, and the periodontal obectives are more valuable than the occlusal ones. The role of the orthodontist should be leveling the bone peaks. The marginal ridges are not always helpful for positioning the posterior teeth. f they are worn or abraded, it is more important to nd the best position to facilitate restoration. Tooth shape is another factor with great importance in treatment planning. n the maority of patients, we nd three main tooth shapes rectangular, triangular, and barrel-shaped teeth. specially when the crown has a triangular shape, the distance between the bone crest and the contact point is relatively large, and the interproimal papilla tends to be absent. Tarnow demonstrated that the papilla is present in 1 of cases when the distance from

the contact point to the interdental bone crest is  mm or less. ince adults have narrower pulp chambers,  can be performed and black triangles closed ig. 1..

Orthodontic Moements ith a healthy periodontal tissue, the supracrestal bers control the etrusive component of forces applicated horiontally to teeth. hen the bone support is reduced, forces are distributed over a smaller area, and the resistance to etrusion is lower. urthermore, the center of resistance of a periodontally involved tooth is shifted apically because of the bone resorption. That is why occlusal forces induce tipping and etrusion of the incisors. hen planning the orthodontic treatment, the apical displacement of the center of resistance should be taken into account, and the moment-to-force ratio therefore must be adapted to the individual situation igs. 1. and 1.1. To provide a uniform loading on periodontal ligament, translation and controlled tipping movements should be preferred. The orthodontic treatment with clear aligners in periodontal patients should be similar to the segmented arch approach. The active and reactive units should be identied and force delivery planned .

OPTIMAL CONTROL OF IOMECANICS n n n n n n

se of light forces enter of resistance void roundtrip low movements elective movements eed for further anchorage implants, temporary anchorage devices Ts free anchorage lost teeth

Taking the tooth long ais as a reference, three kinds of movement can be performed.

Mii M esiodistal movements are mainly used to close diastemas and eliminate the black triangles, after providing  and the creation of a surface of contact. pace opening for implant placement is a predictable movement that can be carried out both in anterior and posterior regions. urgical bone augmentation could be needed at the end of orthodontics due to high interindividual variability of neoformed bone thickness.  mesially inclined molar is not a cause of periodontal disease itself; however, molars uprighting alone can be performed to achieve root parallelism before implant placement. n presence of an infraosseous defect, T should be eecuted prior to orthodontics.  strict control of oral hygiene on the distal side of an uprighting tooth is mandatory to avoid subgingival plaque formation. dditional anchorage using miniscrews may be needed in case of tricky malpositions. The mesialiation of molars is a translation movement that can be performed using light forces ig. 1.11; however, considering the high risk of complications such as bone fenestration, bone loss, and radicular resorption, it should be managed carefully.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

Fig. 16.7 Orthodontic relapse in a young patient teeth   and  are located outside the buccal bone. The twisted retainer prob ably not passie allowed a radicular torue moement  on tooth  that promoted a gingial recession with lac of adherent gingia.

211

212

Principles and Biomechanics of Aligner Treatment

Fig. 16. ifferent tooth shapes. (From Nanda R Esthetics and Biomechanics in Orthodontics nd ed S Lo, MO Eeer )

Fig. 16. Center of resistance ariation in case of bone loss. (From Nanda R Esthetics and Biomechanics in Orthodontics nd ed S Lo, MO Eeer )

Fig. 16.10 In this patient a stainless steel powerarm has been bonded to tooth  and retraction has been performed using maimum anchorage.

Fig. 16.11 esialiation of lower third molars.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

iig M estibulolingual movements are needed to position teeth inside the alveolar bone. fter a proper evaluation of bone thickness, typical localied recessions on incisors can be improved through retraction of teeth within the alveolar walls.1 The most effective movements, translation and lingual root torque, must be carried out on lower incisors only after a previous evaluation of mandibular symphyseal dimensions height, depth, and angle. rthodontics can be subsequently followed by mucogingival surgery for complete root covering. n selected cases, bodily movements can be associated with corticotomies and bone tissue grafting to prevent further periodontal damage. n efcient torque control is also needed, in combination with intrusion, during retraction of ared incisors after pathologic tooth migration. ic M The vertical movements are the main issue in periodontal patients since they are used to restore the correct alveolar bone and gingival margin levels. oving a tooth with a vertical defect can increase the risk of further attachment loss. f intrusion is needed, the probing depth has to be reduced before orthodontics. Three-wall defects can be successfully treated with regenerative surgery followed by orthodontic intrusion. ntrusion is indicated when vital teeth are etruded, in both anterior and posterior regions. n an animal study, elsen demonstrated that intrusion can improve the quantity of new attachment if carried out under healthy conditions.  proper intrusive force should be  to  g per tooth and is affected by the periodontal support. efore providing

213

vertical movements, a correct diagnosis should take into account the presence of recession and the labial sulcular depth of the maillary incisors. f no recession has occurred, the gingival margins are used as a guide in tooth positioning. f the sulcular depth is uniformly 1 mm, the discrepancy in gingival margins may be due to uneven wear or trauma of the incisal edges ig. 1.1. Treatment for this problem is the intrusion. hen the gingival margins are aligned, the discrepancy in the incisal edges presents itself, and restoration of the short teeth can be provided. rthodontic intrusion should be planned to also properly treat lower incisors with incisal edge abrasion. These teeth typically are overerupted to maintain contact, and no space for restoration is left. ndodontic treatment and periodontal crown lengthening with bone removal are avoided by orthodontics that provides the correct restorative space. eriodontal patients are usually characteried by ared and etruded upper incisors and horiontal bone loss.11  combination of retraction and intrusion is needed, while a simple retroclination would deepen the bite. The available molars and premolars are used as anchorage units. dditional scaling and root planning every  weeks are mandatory during active intrusion. espite contrasting evidence about intrusion in patients with reduced periodontal support, elsen found creation of new attachment with a consequent reduction of root to crown ratio and ardaropoli et al.  demonstrated the reduction of probing pocket depth and the gain of clinical attachment after combined ortho-perio treatment of etruded teeth with infrabony defects. The use of light 1– g and continuous forces together with proper

Fig. 16.12 electie intrusion of worn teeth. (From Nanda R Esthetics and Biomechanics in Orthodontics nd ed S Lo, MO Eeer )

214

Principles and Biomechanics of Aligner Treatment

torque control seems to be relevant.-1 evertheless, there can be transformation of supragingival plaque in subgingival and risk of angular defect formation. oreover, attention must be paid to root morphology, since there is a higher risk of resorption of short and pipette-shaped roots. hen a periodontally involved tooth needs prosthetic rehabilitation or the gingival margin is more apical than the others, orthodontic etrusion has a benecial effect on the bone level. trusion movements can be eecuted to level gingival margins, recover the interdental papilla, and reduce probing depth. trusion can be performed either with light or heavy forces. undamentals are direction of movement and torque control because uncontrolled tipping can lead to vestibulariation of the root.  constant occlusal grinding is due to avoid premature contacts. t the end of the movement, a ed retention should be performed for at least  months to prevent relapse. n case of healthy periodontium, when the crown is lost because of decay or trauma, etrusion is performed associated with brotomy every 1 days or followed by surgical crown lengthening. n case of attachment loss, etrusion is eecuted to level gingival margins and reduce angular defects. llow  to  months for connective bers to heal after regenerative therapy.  single compromised tooth can be etruded for leveling of gingival margins, providing hard and soft tissue augmentation before the implant placement. n this case, the use of light forces 1 mmmonth is recommended. f a patient is missing multiple teeth, treatment plans can eventually include placement of dental implants to have a further anchorage for the orthodontics. efore the orthodontic loading, a proper amount of time is needed for the osteointegration. Ts such as microscrews and bone plates are also effective in enhancing tooth movements without the biomechanical side effects.

FINAL FLOCART n n n

n n n n

eestablish periodontal health eriodontal reassessment f possible, regenerative andor mucogingival surgery and implant placement rthodontic treatment eriodontal maintenancesupportive therapy rthodontic retention rosthodontic naliation

Retention educed periodontal tissues are a risk factor for orthodontic relapse. n addition, the periodontally involved teeth could be signicantly mobile. The purpose of retention is to stabilie them and reduce mobility. very action that intends to prevent relapse should be performed immediately after the completion of orthodontic movement. ince the presence of retainers bonded to all anterior teeth can increase plaque accumulation and gingivitis, the use of removable retainers should be recommended when ecessive mobility is not an issue. oreover, ed retainers can produce inadvertent tooth movement, and regular observation is needed. arafunctional habits, such as onychophagia, might be involved. The orthodontic patient with periodontal involvement may be missing one or more teeth. ince pathologic tooth migration is worsened by lack of posterior occlusal support, a nal prosthetic

rehabilitation should always be planned.  ed or removable prosthesis can help stabilie the remaining teeth in the arch and provide an occlusal stop for teeth in the opposing arch. cclusal splint, can be eventually used as orthodontic retention in patients with parafunctional habits, including n n

n n

emovable retainers hen mobility is ecessive n ower ed retainer -, - in case of deep bite n ntra- or etracoronal ed retainer in other setant rosthetic rehabilitation of edentulous sellae cclusal night guard

onclusions lear aligners are safer than conventional orthodontics for stable periodontal patients. ligners allow patients to have ecellent hygiene control, especially during long treatments. linheck software is a diagnostic tool that provides a virtual setup both for orthodontics and prosthodontics. t offers a precise  plan control of each movement and the possibility of selective anchorage. The keys to success are based on both lifelong supportive periodontal treatment and orthodontic retention. atient adhesion to the supportive periodontal treatment is mandatory to maintain stable long-term results.1-

linical ase FIRST ISIT ate 1--1 ender ale ge y rofession mployed hief complaint leeding gums and drifting of front teeth ttitude atient is concerned about his dentition and is positive about keeping his teeth pectations atient has realistic epectations and wants to restore his dentition in health edical anamnesis eneral appraisal of patient it and healthy amily medical anamnesis ast pathologic anamnesis ypertensive ecent pathologic anamnesis one rug therapy llergies or sensitivities one abits ormer smoker who quit  months back ccupation and stress level mployed in a multinational company; medium stress level ast physical eamination  months back, nothing signicant ental anamnesis igs. 1.1 and 1.1 ate and reason for the last dental visit  months back for bleeding gums aor dental treatments o issing teeth reason 1. caries dverse dental eperiences one istory of periodontal disease es revious periodontal treatments nly supragingival scaling ral habits one ral hygiene practices rushes twice daily with a manual toothbrush rophylais frequency nce every year T and muscles of mastication oth unremarkable

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

215

Fig. 16.13 Baseline intraoral iew.

INTRAORAL CLINICAL EXAM

Fig. 16.14 Baseline smile.

ental analysis n ngle class olar and canine class 1 n issing teeth 1. n ental malpositions 1.1 etruded and proclined n ecays one n nadequate restorations . premature contacts in centric occlusion one n cclusal trauma one n cclusal wear one orking contacts on right side 1. canine guided ig. 1.1 n alancing contacts on left side one

216

Principles and Biomechanics of Aligner Treatment

Fig. 16.15 oring contacts.

orking contacts on left side . canine guided n alancing contacts on right side one rotrusive contacts 1.1, 1. n osterior interferences ., .

n n

n n

XRAY STATUS n

n

mount of bone resorption  bone loss vertical and horiontal ig. 1.1

n n

nterradicular translucencies one amina dura and periodontal ligament enlargements one eriapical pathologies one etained teeth one oot fragmentsforeign bodies one ecays one evitalied teeth one

Fig. 16.16 Baseline status.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

ASELINE PERIODONTAL CART (I. .)

Fig. 16.17 Baseline periodontal chart.

217

21

Principles and Biomechanics of Aligner Treatment

PERIODONTAL EXAMINATION . teeth  . teeth with   mm   n # mm  n – mm  n  mm 1 n n

PERIODONTAL REEALUATION (I. . and .) DIANOSIS eneralied chronic severe periodontitis level  presence of proimal attachment loss of  mm in two or more nonadacent teeth tage  grade  Tables 1. and 1.

Fig. 16.1 eealuation chart.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

21

A

B Fig. 16.1 (A) Toothbytooth diagnosis. (B) Toothbytooth prognosis. (From Ko V, Caon  Commenar rono reed a em for ann erodona rono J Periodontol )

Table 16. tages of Periodontitis PRIODOTITIS ST

Stage I

Stage II

Stage III

Stage I

Seerit

Interdental  at site o greater loss

– mm

– mm

 mm or etending to the middle third of the root

 mm or etending to the apical third of the root

Radiograhic bone loss

Coronal (,)

Coronal third (–)

tending to middle third

tending to the apical third

Tooth loss

o tooth loss due to periodontitis

Tooth loss due to peri odontitis of # teeth

Tooth loss due to periodonti tis of  teeth

ocal

n

In addition to stage II compleity n Probing depth  mm n ertical bone loss  mm n urcation inolement n Class II or III moderate ridge defect

In addition to stage III compleity n eed for comple rehabili tation due to masticatory dysfunction n econdary occlusal trauma (tooth mobility degree ) n Bite collapse n rifting n laring n , remaining teeth n eere ridge defect

omleit

n

tent and Distribution

dd to stage as descritor

CAL, Cnca aachmen ee

aimum probing depth of – mm ostly horiontal bone loss

n

n

aimum probing depth – mm ostly horiontal bone loss

or each stage describe etent as localied (, of teeth inoled) generalied or molar incisor pattern

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Principles and Biomechanics of Aligner Treatment

Table 16. rades of Periodontitis

PRIODOTITIS RD Primar riteria

rade Modiers

rade  Slo Rate o Progression

rade  Moderate Rate o Progression

rade  Raid Rate o Progression

irect eidence of progression

ongitudinal data (PA radiographs or CA loss)

idence of no loss oer  years

, mm oer  years

 mm oer  years

Indirect eidence of progression

Bone lossage

,.

.–.

..

Case phenotype

eay biolm deposits with low leel of destruction

estruction commensurate with biolm deposits

estruction eceeds epectation gien biolm deposits specic clinical patterns sugges tie of periods of rapid progression andor early onset disease lac of epected response to standard bacterial control therapies

is factors

moing

onsmoer

moer , cigarettesday

moer  cigarettes day

iabetes

iabetes

ormoglycemic with or without prior diagnosis of diabetes

bAc ,. in diabetes patients

bAc . in diabetes patients

CAL, Cnca aachmen o PA, eraca HbA1c, refer o caed haemoon

PERIO TREATMENT OALS 1. . . .

ontrol of supragingival and subgingival infection  , rrest of the progression of periodontitis traction of hopeless teeth

TREATMENT PLAN tiologic therapy 1. ral hygiene instructions and motivation . onsurgical therapy caling and root planing quadrant by quadrant protocol . traction of 1., ., . . hange of lling ., .

CLINICAL EXAMINATION REEALUATION (I. .) . teeth  . teeth with   mm   n # mm 1 n – mm  n  mm  n n

TREATMENT PLAN AFTER ETIOLOIC TERAPY n n n n

egenerative therapy 1., etraction 1., 1. egenerative surgery 1.1, 1., . traction ., mesial root resection . egenerative surgery ., .

n n

sseous resective surgery with tunnel preparation . upportive periodontal treatment

Oic lignment and space closure on upper arch I T n 1., 1., . Pi Si T very  months igs. 1.1 through 1. The periodontal therapy was performed by rof. ario imetti, head of the epartment of eriodontology of the ental chool of the niversity of Torino, Torino, taly. Oic Digi (ig. .) keletal n   1,   ental n olar  nonassessable, canine  1, deep bite, increased , spaces between teeth and black triangles, medial line deviated acial n onve prole Scic Oci  T igs. . through .) n ailla lign and intrude the teeth, close spaces, correct the midline n andible lose spaces, intrude lower incisors, correct the midline n acial esthetics mprove esthetic smile line

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

Fig. 16.20 Periodontal status and chart at reealuation.

221

222

Principles and Biomechanics of Aligner Treatment

3 mm

3 mm

3 mm

3 mm

3 mm

4 mm

8 mm

3 mm

A

B

C Fig. 16.21 egeneratie therapy on tooth . (A) Bone sounding (B) incisional photos (C) ¤ap photos.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

A

B

C

D Fig. 16.22 egeneratie therapy on tooth  biomaterial photos. (A) efect cleaning. (B) mdogain (s). (C) Pref el (TA). () BioOss.

Fig. 16.23 egeneratie therapy on tooth suture photos.

223

224

Principles and Biomechanics of Aligner Treatment

A

B Fig. 16.24 egeneratie therapy on incisors. (A) Incision pfotos and (B) ¤ap photos.

A

B

C

D Fig. 16.25 egeneratie therapy on incisors biomaterial photos. (A) efect cleaning. (B) mdogain (s). (C) Pref el (TA). () BioOss.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

Fig. 16.26 Osseous resectie surgery degree setant.  Alternatie therapies periodontal supportie therapy   conseratie surgery resectie bone surgery.

225

226

Principles and Biomechanics of Aligner Treatment

Fig. 16.27 esectie surgery bone remodeling.

Fig. 16.2 Orthodontic records.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

A

B Fig. 16.2 ClinChec beginning (A) and end (B) frontal iew.

A

B Fig. 16.30 ClinChec beginning (A) and end (B) upper arch.

A

B Fig. 16.31 ClinChec beginning (A) and end (B) lower arch.

227

22

A

Principles and Biomechanics of Aligner Treatment

B Fig. 16.32 ClinChec beginning (A) and end (B) right side.

A

B Fig. 16.33 ClinChec beginning (A) and end (B) left side.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

Fig. 16.34 nd of preprosthetic orthodontics.

Fig. 16.35 Implant . ..

22

230

Principles and Biomechanics of Aligner Treatment

Fig. 16.36 Implant placement.

Fig. 16.37 Implant placement photos.

16 • Clear Aligner Orthodontic Treatment of Patients with Periodontitis

A

B

C

D Fig. 16.3 Implant placement biomaterials. (A) Bony window. (B) inus membrane eleation. (C) BioOss. () BioOss and membrane positioning.

Fig. 16.3 inal orthodontic rays. Continued

231

232

Principles and Biomechanics of Aligner Treatment

Fig. 16.3, c’

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1. atuliene , etursson , alvi . nuence of residual pockets on progression of periodontitis and tooth loss results after 11 years of maintenance. J Clin Periodontol ;-. . alvi , ischler , chmidlin . isk factors associated with the longevity of multi-rooted teeth. ong-term outcomes after active and supportive periodontal therapy. J Clin Periodontol. 1;1 1-. . ee T, uang , un T, et al. mpact of patient compliance on tooth loss during supportive periodontal therapy a systematic review and metaanalysis. J Dent es. 1;-. . chsenbein . sseous resection in periodontal surgery. J Periodontol. 1;11-. . arnevale , aldahl . sseous resective surgery. Periodontol . ;-. doi1.1.1-.. 1.. . arnevale . ibre retention osseous resective surgery a novel conservative approach for pocket elimination. J Clin Periodontol. ;1-1. doi1.1111.1-1..1.. . envert , ersson .  systematic review on the use of residual probing depth, bleeding on probing and furcation status following initial periodontal therapy to predict further attachment and tooth loss. J Clin Periodontol. ;-1. doi1.1 .1-1..s-... . amford , issle . The modied idman ap. J Periodontol. 1;1-. doi1.1op.1....1. . ang . ocus on intrabony defects—conservative therapy. Periodontol . ;1-. doi1.1.1-. .1.. 1. eit-ayeld , Trombelli , eit , et al.  systematic review of the effect of surgical debridement vs non-surgical debridement for the treatment of chronic periodontitis. J Clin Periodontol. ;-1. doi1.1.1-1..s... 11. Trombelli , arina , ranceschetti , et al. ingle-ap approach with buccal access in periodontal reconstructive procedures. J Peri odontol. ;-. doi1.1op...

17

Surgery First with Aligner Therapy FLAVIO URIBE and RAVINDRA NANDA

HISTORIC BACKGROUND The treatment of moderate to severe dentofacial deformity is usually addressed by means of orthognathic surgery. The objectives of orthognathic surgery are to accomplish adequate facial esthetics while achieving a functional occlusion. The occlusal relationship serves as a guide for the skeletal movements and therefore is an important element in orthognathic surgery. Fixed orthodontic appliances in the presurgical phase have historically been used to prepare the dentition for the skeletal movements and to ne-tune the occlusion after orthognathic surgery. pecically labial xed appliances in the presurgical phase eliminate dental compensations and prepare the arches for surgery. onded orthodontic brackets on the labial surfaces of the teeth and wires are the orthodontic appliances of choice by clinicians in orthognathic surgery as treatment complexity is high in these patients. lear aligner therapy T with nvisalign lign Technologies an ose   at the forefront has become a treatment modality in orthodontics that has gained acceptance by practitioners after the signicant improvements in the appliance over the last few years. ore complex malocclusions have been able to be treated with this appliance with the addition of attachments that optimie tooth movements. n example of more complex approaches with the nvisalign appliance is evident in its use in tandem with orthognathic surgery instead of the conventional labial xed appliances. rthognathic surgery in conjunction with the nvisalign appliance is well accepted by patients with dentofacial deformity for two main reasons. First most of these patients are usually adults who understandably favor the inconspicuousness of clear aligners over xed labial appliances. econd often patients undergoing orthognathic surgery have received orthodontic treatment with xed appliances during their early teenage years. This treatment has usually been long as the orthodontic therapy may have tried to camouage the effects of abnormal growth. The net effect is a burnout of the patient who does not want to receive any more orthodontic therapy. rthognathic surgery has three specic stages which include a presurgical orthodontic phase the surgical procedure and a postsurgical orthodontic nishing phase. The incorporation of nvisalign in orthognathic surgery can be accomplished in different ways depending on which stage of treatment it will be used and the type surgical approach surgery rst or conventional approach. For example one of the approaches is to limit the nvisalign appliance to the presurgical phase. Typically this phase is the longest in orthognathic surgery lasting approximately from  to  months. Therefore if patients receive T on the

presurgical phase xed appliances will be only used for a short period of time during the postsurgical phase. This approach is often preferred since the labial xed appliances used in the postsurgical phase typically have better nishing control of the occlusion. The labial orthodontic appliances are placed just before surgery thereby facilitating the conventional approach during surgery that ties the interocclusal surgical splint to the orthodontic bonded appliances required for xation of the proximal and distal bone segments after the osteotomies. The second approach uses the nvisalign system for both pre- and postsurgical phases with no xed labial appliances which has the challenge of limited areas available to securely tie the surgical splint for maxillary and mandibular xation. lthough clinicians are using nvisalign in conjunction with orthognathic surgery no studies have been conducted evaluating the outcomes with this approach. n fact most of the published literature has been in the form of case reports. The rst report of this approach was published in  using nvisalign in combination to orthognathic surgery. The treatment of two patients was described in which nvisalign was used for the presurgical phase of aligning and leveling the arches. egmental xed appliances were also used as adjuncts to the clear aligners to derotate some teeth since at that point in time the nvisalign appliance had not developed the optimied attachments that facilitated these corrections. Fixed appliances were placed just before the surgical procedure and maintained through the postsurgical detailing phase. The total treatment time for one patient was  months  months for the presurgical phase with nvisalign and  months for the other  months for the presurgical phase with nvisalign. The reason for one of the patients having undergone almost  years of treatment was attributed to insurance approval and scheduling the surgery date. dditionally the patients were changing aligners every  weeks. Finally the author suggested that in patients with single jaw surgery xed appliances would not be necessary being managed fully with the nvisalign appliance. n  omack and ay reported on another patient treated with nvisalign and orthognathic surgery who had class  malocclusion and sleep apnea. n this report bimaxillary advancement with a two-piece-maxilla for transverse correction was executed. oth the pre- and postsurgical phases were completed with the nvisalign appliance. The duration of the presurgical phase was  months for this patient. The xation during surgery of the maxilla and the mandible after the osteotomies was achieved by means of archbars tied to the splint. ince the maxilla was split for transverse expansion a soft tissue splint was placed during 235

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surgery and left for  weeks for stabiliation of the two maxillary halves. fter the surgical procedure polyvinyl siloxane  impressions were taken for renement of the occlusion which took another  months of treatment. The total treatment time was  months which included a period in which the patient was not seen due to unavailability related to a work schedule. uring this nishing phase buttons were bonded to the posterior teeth to settle the occlusion with elastics. ancui et al. in  reported on the treatment of a patient who had multiple missing teeth and class  malocclusion who underwent orthognathic surgery with nvisalign. oth pre- and postsurgical phases were performed with the nvisalign appliance. The presurgical phase lasted  months. For the xation of the maxilla and mandible into their new positions buttons were bonded to the labial surfaces of the majority of the posterior teeth. The authors maintained the patient on the splint for  weeks after surgery and then delivered a dynamic functional positioner for  months. ome ceramic brackets were bonded to help with the seating of the occlusion. The total treatment time was  months. agani et al. in  reported on another patient with a class  malocclusion treated with nvisalign in the preand postsurgical phases.  total of  months was the duration of the presurgical alignment phase. The day before surgery xed appliances were bonded which were removed  month after surgery. The total duration of treatment was  months.

Splint-Aided Maxillary and Mandiblar ixatin itt abial ixed Appliane hen labial xed orthodontic appliances are not present the stabiliation of the surgical splint after the osteotomies can be troublesome. The maxilla and mandible need to be securely tied to the surgical splint to ensure proper referencing the jaws to each other to achieve the planned outcome after surgery. The surgical splint transfers the information of the virtual three-dimensional  plan to guide the free osteotomied segment to a stable reference skeletal region. The splint must be tied to the dentition or denture bases to reference maxilla and mandible to each other. The connection of the splint to the teeth is usually facilitated when orthodontic appliances are bonded to the labial surfaces of the teeth. ith nvisalign there are no labial appliances to enable this connection Fig. .. ifferent approaches have been described in the literature to overcome this problem. rchbars used for maxillary and mandibular fracture xation are one of the earliest adopted approaches. The problem with this approach is it is time consuming thereby extending the duration of time the patient is under anesthesia which increases the risks of the surgical procedure. nother approach is to bond multiple buttons on the labial surfaces of teeth specically to be used for the surgical procedure. This was reported by ong et al. when using lingual orthodontic appliances in orthognathic surgery.

Fig. 17.1 Surgical splint with holes to be used in a patient undergoing orthognathic surgery using Invisalign as the only appliance for orthodontic treatment. Note that no labial orthodontic appliances are present.

17 • Surgery First with Aligner Therapy

owever since no archwires are present connecting the bonded buttons bonding failure could occur during the operation while the jaws are being tractioned to seat them into the splint. Furthermore the breakage of one of these attached buttons may end up entrapped in the mucoperiosteal aps causing a signicant complication to the surgical procedure. ith the advent of miniscrews in orthodontics the connection of the dentition to the surgical splint has been facilitated. This was reported by aik et al. who added two miniscrews in each of the quadrants mesial to the rst molars and premolars. These miniscrews are used to secure the splint tightly to the teeth and can be used after surgery to support the use of intermaxillary elastics to keep the teeth in the postsurgical planned occlusion.  more complex setup that connects the miniscrews through a bar framework is commercially available. The martlock hybrid F from tryker alamaoo   and the atrix F from epuy ynthes raniomaxillofacial est hester   are similar bone-supported archbars to be used during surgery. This framework is secured to the labial alveolar bone of the dentition through four to six miniscrews per arch. The main advantage of these two products over an approach that uses only the miniscrews is that more locations are available to connect the surgical splint to the maxilla and mandible through ligatures. This may facilitate more tight adaptation of the osteotomied segments into the surgical splint. Typically the mesh including the miniscrews is removed after the osteotomied maxilla and mandible are secured with hardware which has the drawback that intermaxillary elastic wear in the postsurgical stage will require to be delivered from the teeth which could have an unfavorable extrusive effect on the specic teeth from which the elastics are being worn.

Tranitinin Int and Ot  Srery it Clear Aliner s mentioned the major difference in the execution of surgery in patients with T is the absence of labial xed orthodontic appliances typically necessary for securing the surgical splint. These patients are typically wearing a series of sequential aligners as part of the presurgical phase and will transition to the aligners in the postsurgical phase to complete orthodontic treatment. f the patient is wearing aligners in the presurgical phase the surgical plan will consist of maxillomandibular movements that will achieve a result close to the nal idealied occlusion. rior to surgery a scan or impression is taken to plan the tooth movements after surgery to detail the occlusion which will be used for fabrication of the aligners. n alternative is to take this scan or  impression after surgery. owever the acquisition of a scan or impression after surgery is somewhat difcult due the limited mouth opening observed during the rst  months after surgery. Therefore taking the scan prior to surgery may be advocated to be able to start wearing the aligners soon after surgery approximately  weeks after. lthough this approach may expedite treatment there still may be a slight unpredictability in the planned occlusion and the actual postsurgical occlusion if different may

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require different movements than originally planned. owever since the teeth would be usually well aligned after the presurgical phase any inaccuracies between the planned and the obtained occlusion can be managed with intermaxillary elastics. n the other hand the predictability of the planned nal occlusal outcome for the fabrication of the postsurgical aligners could be more difcult in patients where the maxilla will require segmentation in two or more pieces. n these situations it is still possible that the presurgical dental models could be segmented to the planned outcome and a scan of this model could be used for the fabrication of the surgical splint and the postsurgical aligners. owever it is better recommended to take the scan or impressions after the surgery to ensure a more precise t of the aligners especially if the segmentation is more that two pieces. nother important consideration when segmenting the maxilla is that the patient typically will have to maintain the splint after surgery for  to  weeks prior to resuming orthodontic movements.  splint covering the incisal and occlusal surfaces of the teeth is bulky and cumbersome for a patient in recovery after surgery.  splint not covering the occlusal surfaces is typically recommended for the postsurgical phase prior to resuming the new aligners Fig. .. n example of management of a patient with nvisalign appliances into and out of the surgical procedure is illustrated in Figs. . . and .. This patient received a eForte  osteotomy with a three-piece segmentation for transverse expansion and vertical impaction of the posterior segments see Fig. .. The occlusion  weeks after surgery at the splint removal visit shows a slight discrepancy between the surgical plan and the achieved outcome see Fig. .. The patient was scanned  weeks later when she was able to achieve enough range of motion. The aligners were delivered in conjunction with vertical elastics from the miniscrews used during surgery. The occlusion was nicely established to the projected outcome approximately  months after surgery see Fig. ..  surgical intermaxillary splint has been designed by  ystems ockville   which consists of -printed thin hard acrylic templates of the maxillary and mandibular arches attached together registering the nal occlusion after the osteotomies. There is no need for wires or miniscrews to tie the osteotomied dentition to the splint. The teeth t into the splint by snapping physically into place. y using this splint a transition to the postsurgical aligners may be more easily achieved. This clear aligner orthodontic splint was recently reported by aminiti and ou who also described a reduced cost version produced by splinting ssix-type trays through clear denture repair acrylic. ne major disadvantage of this new type of intermaxillary splint is that the miniscrews are typically not placed therefore intermaxillary elastics to maintain the occlusal result after surgery require either hooks on the clear aligners or cutouts for bonding buttons or brackets to the labial surfaces of some teeth.

Srery irt and CAT  very novel approach to the application of the nvisalign system in orthognathic surgery is its integration to the

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Fig. 17.2 Surgical nal splint without occlusal coverage to be left for  to  wees postsurgically due to a three piecemailla osteotomy.

Fig. 17.3 Threedimensional virtual surgical plan. A Presurgery.

17 • Surgery First with Aligner Therapy

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Fig. 17.3, cont’d B Planned osteotomies consisting of threepiecemailla with impaction of the posterior segments and mandibular advancement with genioplasty.

Fig. 17.4 Postsurgical occlusion deviating slightly from the planned occlusion. A ight buccal B eft buccal  frontal occlusal views.

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Fig. 17.5 cclusion seated with intermaillary elastics and clear aligners to the planned outcome after  months. A ight buccal B eft buccal  frontal occlusal views.

surgery rst approach F. erhaps this is one of the most attractive options for patients with dentofacial deformity where the facial and smile esthetics drive their chief complaint. urgery rst addresses the dentofacial deformity from the beginning of treatment without any presurgical orthodontics. y performing orthognathic surgery in this manner it has been shown that patient satisfaction is higher than with the conventional approach. This is understandable since obviating the presurgical phase the typical decompensations that accentuate the dentofacial deformity are eliminated. Furthermore the chief complaint of the patient is immediately addressed without being postponed for a year or more as is the case with the conventional approach. nother condition where the combination of F and T is largely indicated is in the treatment of patients with obstructive sleep apnea who will undergo maxillomandibular advancement surgery. First the surgery addresses immediately the medical functional condition without a delayed presurgical orthodontic phase secondly these patients can achieve a good occlusion after surgery with the use of clear appliances which are more acceptable to this population particularly composed of adult patients. n the FT nvisalign approach two common treatment modalities have been applied. The rst consists of placing labial orthodontic appliances including a wire prior to surgery – weeks before. These xed appliances are used for  to  months after surgery during which time major intraarch movements are accomplished and intermaxillary vertical elastics are used to seat the occlusion. This approach also has the advantage for the surgeon of being able to tie the surgical splint to the orthodontic appliances during maxillary and mandibular osseous xation.

The appliances are then removed after this short phase of orthodontic xed therapy and nvisalign trays are given to the patient until treatment completion. The second treatment modality uses nvisalign as the only appliance for orthodontic movement after surgery without the use of any xed labial appliances. This approach unfortunately poses the same challenge on maxillary and mandibular xation for patients who do not have labial orthodontic appliances during surgery. onetheless different alternatives have been designed to facilitate and increase the predictability of the xation with nvisalign appliances as described earlier.  patient who underwent F in conjunction with nvisalign is presented to illustrate this specic approach. This case report also illustrates how the  virtual plan for the surgical treatment can be integrated to the orthodontic  dental plan represented in the linheck lign Technologies an ose  .

Cae Stdy  -year-old female patient presented to the oral maxillofacial surgeon with the goal of improving her facial esthetics Fig. .. he had received orthodontic treatment during her adolescence consisting of camouage treatment for a class  skeletal relationship addressed through the extraction of maxillary rst premolars. The patient had close to adequate arch alignment and a class  occlusion with a -mm overjet Fig. . however there was a signicant facial convexity related to a large mandibular deciency. The denture base was anteriorly positioned to the apical base in the mandible and the lower incisors were signicantly labially inclined. The patient also had steep

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A

B

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C

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Fig. 17.6 Pretreatment etraoral photos. A Frontal lips relaed B smile  prole  bliue  bliue smiling views. (A-C from Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. –

Fig. 17.7 Pretreatment intraoral photos. A ight buccal  B Frontal Continued

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Fig. 17.7, cont’d  eft buccal occlusion.  aillary and  andi bular occlusal views. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod.  –

lower mandibular and occlusal planes. The maxillary position of the incisors was overall adequate in the vertical and anteroposterior dimensions and included a good inclination in reference to the cranial base Fig. .. ll third molars had been extracted and the roots had adequate root parallelism Fig. .. To maximie the mandibular projection two options were available. The rst one required the extraction of two mandibular premolars to retract the mandibular incisors

Fig. 17.8 Pretreatment digitied lateral cephalogram. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod -

Fig. 17.9 Pretreatment panoramic radiograph. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod -

17 • Surgery First with Aligner Therapy

achieving a large overjet to obtain a signicant mandibular advancement with surgery. The second option was a nonextraction approach with a counterclockwise rotation of the maxillomandibular complex in conjunction with a genioplasty. The patient opted for the second option as she did not want any more tooth extractions and did not want a prolonged presurgical orthodontic phase of space closure. dditionally with a nonextraction approach surgery rst was indicated as it addressed her chief complaint of optimiing her facial esthetics.  virtual  plan was made for the surgical movements Fig. .. hen her stone models were occluded in the planned occlusion after surgery no transverse problems were observed therefore no maxillary segmentation was planned Fig. .. Figures . and  shows the specic movements that were planned for this patient. The counterclockwise rotation of the maxillomandibular complex in conjunction with the genioplasty gave her approximately  mm of projection at menton. rior to surgery  impressions were taken for fabrication of the aligners that would address the mild crowding and would also serve to detail the occlusion in the postsurgical phase. The patient was advanced into an edge-to-edge incisor overcorrection relationship. Four miniscrews on each

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quadrant were placed interradicularily to be used during surgery for intermaxillary xation. Two weeks after surgery facial esthetics were greatly improved with the surgical procedure Fig. .. t the occlusal level a slight lateral open bite was noticed on the right side which was expected based on the planned postsurgical occlusion Fig. .. The patient was wearing intermaxillary elastics in a class  direction from the more anterior miniscrews in the maxilla to the most posterior miniscrews in the mandible. Two months after surgery the facial swelling had reduced signicantly Fig. . and the patient had almost  of mandibular range of motion. ll the attachments from the nvisalign appliance were bonded and small tubes bonded to the mandibular rst molars. The patient started the rst phase of aligners changing them on a weekly basis. ntermaxillary elastics from the right maxillary miniscrew implants were used to erupt the mandibular teeth on this opposing quadrant into occlusion Fig. .. Five months after surgery the lateral open bite on the right buccal segment was still evident Fig. ..  cantilever arm was extended from the lower right rst molar to engage an elastic extending from the maxillary right posterior miniscrew Fig. .. The objective of this cantilever arm was to provide an uprighting moment to the right lower molar which was mesially tipped. ntermaxillary elastics were also

Fig. 17.10 A Threedimensional  virtual surgical plan presurgery. Continued

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i 171 nt’d B andmar changes with the planned surgery in .  ounterclocwise rotation of the maillomandibular comple. (A from Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -

worn from two mandibular buttons on the premolars to a hook in the maxillary aligner. istal to the mandibular right canine the aligner was cut to allow for extrusion on the mandibular buccal segment. Twelve months after surgery the swelling had completely resolved Fig. .. The occlusion was almost ideal at this point with some minor renement required Fig. .. fter another aligner renement phase the orthodontic treatment was nished to a good occlusal and facial result Figs. . and .. The lateral cephalogram depicts the sagittal soft and hard tissue changes Fig. . while the panoramic radiograph shows adequate root parallelism Fig. .. The superimposition reveals the

remarkable soft and hard tissue mandibular advancement Fig. .. s part of her enhancing the patient’s facial esthetics a rhinoplasty was performed approximately  months after orthognathic surgery.  very nice esthetic and occlusal outcome was achieved in this patient with the FT approach. nterestingly this patient was attending college in a location that was at a far distance from our institution. ost of her visits were carried during the summer when she was off school. uring the academic year she was provided with the aligners and her progress was monitored through photos she provided to our ofce every  months. The patient had approximately  orthodontic visits.

17 • Surgery First with Aligner Therapy

Fig. 17.11 Planned postsurgical occlusion with overcorrection. A ight buccal B Frontal  eft Buccal views of the planned occlusion

Fig. 17.12 traoral photos  wees postsurgery. A Frontal B Prole and  Smiling views.

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Fig. 17.13 Intraoral photos  wees postsurgery. A ight buccal B Frontal and  eft buccal views of patient in occlusion.

Fig. 17.14 eduction of facial swelling  months postsurgery. A Frontal B Prole and  Smiling views. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -

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Fig. 17.15 Intraoral photos  months postsurgery. A ight buccal B Frontal and  eft buccal views. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -

Fig. 17.16 ateral open bite on the right is still present  months after surgery. A ight buccal B Frontal and  eft buccal views of patient in occlusion.

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Fig. 17.17 antilever arm etended from bonded lower right molar tube to upright this tooth using an elastic from the maillary miniscrews aligner cut distal to the lower right canine to allow eruption of the buccal segment.

Fig. 17.18 traoral photos  months postsurgery.

Fig. 17.19 Intraoral photos  months postsurgery. A ight buccal B Frontal and  eft buccal views of patient in occlusion.

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Fig. 17.20 Posttreatment etraoral photos. A Frontal B Smiling and  Prole views. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -

Fig. 17.21 Posttreatment intraoral photos. A ight buccal B Frontal and  eft buccal views of patient in occlusion. Continued

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Fig. 17.21, cont’d  aillary and  andibular occlusal views. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -

Fig. 17.23 Posttreatment panoramic radiograph. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -

Fig. 17.22 Posttreatment lateral cephalogram. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -

Fig. 17.24 Superimposition of the seletal and soft tissue changes. (From Chang J, Steinaher D, Nanda R, et a “Srger-rt” aroah ith Iniaign thera to orret a a II maoion and eere mandiar retrognathim J Clin Orthod. -

17 • Surgery First with Aligner Therapy

Cnlin FT is a very appealing approach for adult patients undergoing orthognathic surgery.   plan for the skeletal movements in conjunction with a  plan for the dental movements can be interconnected to achieve excellent occlusal and esthetic results. Furthermore the presurgical orthodontic phase can be obviated with the immediate resolution of the dentofacial deformity. This approach may become mainstream in the future as renements in the techniques and improvements in the nvisalign appliance are developed to increase predictability.

References . owling  speland  rogstad  et al. uration of orthodontic treatment involving orthognathic surgery. Int J Adult Orthodon Orthognath Surg. -. . uther F orris  art . rthodontic preparation for orthognathic surgery how long does it take and why  retrospective study. Br J Oral Maxillofac Surg. -.

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. oyd . urgical-orthodontic treatment of two skeletal class  patients with nvisalign and xed appliances. J Clin Orthod. -. . omack  ay . urgical-orthodontic treatment using the nvisalign system. J Clin Orthod. -. . arcui  alassini  rocopio  et al. urgical-nvisalign treatment of a patient with class  malocclusion and multiple missing teeth. J Clin Orthod. -. . agani  ignorino F oli  et al. The use of nvisalign system in the management of the orthodontic treatment before and after class  surgical approach. Case Rep Dent. . . Taub  alermo . rthognathic surgery for the nvisalign patient. Semin Orthod. -. . ong  ee  unwoo  et al. ingual orthodontics combined with orthognathic surgery in a skeletal class  patient. J Clin Orthod. -. . aik  oo  im  et al. se of miniscrews for intermaxillary xation of lingual-orthodontic surgical patients. J Clin Orthod. - qui . . aminiti  ou T. lear aligner orthognathic splints. J Oral Maxillofac Surg. . . elo  asparini  aragiola  et al. urgery-rst orthognathic approach vs traditional orthognathic approach oral health-related quality of life assessed with  questionnaires. Am J Orthod Dentofacial Orthop. -.

18

Pain During Orthodontic Treatment: Biologic Mechanisms and Clinical Management TIANTONG LOU, JOHNNY TRAN, ALI TASSI, and IACOPO CIOFFI

The Importance of Orthodontic Pain Pain, as dened by the International Association for the Study of Pain, is “an unpleasant and emotional experience associated with actual or potential tissue damage or described in terms of such damage.” he maority of patients will experience arying intensities and freuencies of pain during their course of orthodontic treatment. Pain is a highly complex experience and is freuently an area of concern among patients undergoing orthodontic treatment. - he experience of pain is modulated by seeral factors, such as the magnitude of noxious stimuli, emotions, cognition, past experience and memories of pain, and other concomitant sensory experiences. rthodontic pain i.e., dental pain associated with orthodontic tooth moement can negatiely impact patient compliance and oral hygiene,- lead to increased freuency of missed appointments, and compromise the oerall treatment result.  ear of pain is a maor reason for patients to forego orthodontic treatment.   In one particular surey, patients rated pain as the highest area of dislie in regard to orthodontic treatment and raned pain fourth among maor fears and apprehensions. ot surprisingly, patients who experience reduced leels of orthodontic pain tend to hae an improed leel of cooperation in treatment.   herefore, practitioners should aim to reduce the pain experience to improe patient compliance, decrease treatment times, and increase oerall patient satisfaction. er the last few decades, there has been an increased demand from prospectie orthodontic patients for more esthetic alternaties to traditional metal bracets and wires.  rthodontic appliances that are less isible may lead to improed patient acceptance and improed uality of life.- ore recent adancements in the specialty hae led to the use of computer-aided design and computer-aided manufacturing AA technology to fabricate orthodontic appliances. his has allowed clear aligner therapy A to become aailable to the mass maret and emerge as a desirable treatment option for orthodontic patients. Since its initial introduction in , A has rapidly increased in popularity, and many orthodontists are utiliing clear aligners instead of conentional multibracet appliances to treat patients with a wide ariety of malocclusions. 252

his chapter aims to proide an oeriew regarding orthodontic pain, its relation to clear aligner therapy, as well as the pharmacologic and nonpharmacologic clinical management of pain experienced during orthodontic treatment.

Biologic Mechanisms of Orthodontic Pain and Clinical Correlates he underlying mechanism of pain during orthodontic tooth moement is a result of the complex interplay between ast numbers of neurons and chemical mediators in both the central and peripheral nerous systems. It is well nown that orthodontic pain is primarily due to an inammatory reaction in the periodontium, which accompanies orthodontic tooth moement. he application of orthodontic force results in a localied region induces ischemia, inammation, and edema in the periodontal ligament space and actiates a cascade of proinammatory mediators. ne of these mediators is the enyme cyclooxygenase- -, a critical component in the synthesis of prostaglandin, which is targeted by nonsteroidal antiinammatory drugs SAIs. ociceptie stimuli exerted by orthodontic appliances are primarily detected by sensory bers such as  bers unmyelinated and thinly myelinated Ad bers in the pulp and periodontal ligament. ther substances that either actiate or sensitie nociceptors during inammation include tumor necrosis factor-a -a, interleuin  I-, I-b, bradyinin, enephalin, serotonin, dopamine, glutamate g-amino butyric acid, and histamine.- Studies hae demonstrated that eleated leels of these compounds are associated with hyperalgesia., In addition, the actiated proinammatory mediators can stimulate the release of neuropeptides from the afferent nere endings into the surrounding tissues. Substance P and calcitonin gene-related peptide P are two potent neuropeptides that cause neurogenic inammation.- hese sensory neuropeptides enhance inflammation through interactions with epithelial cells to induce asodilation and increase blood essel permeability., hey also lead to mast cell degranulation and further release of proinammation mediators such as histamine and serotonin. hese inammatory mediators trigger the release of more

18 • Pain During Orthodontic Treatment: Biologic Mechanisms and Clinical Management

Pain

neuropeptides, contributing to a continuation and intensication of the inammatory process. Substance P also increases the leels of arious cytoines, such as - a, I-b, and I-.  P stimulates the release of I-, I-, and -a  hese cytoines sere as signaling messengers between immune cells and are important in bone resorption, deposition, and remodeling. I-b is released by broblasts of the gingia surrounding the teeth during orthodontic tooth moement and is inoled in bone remodeling.  I- is a regulator of the immune response during inammation and the formation and actiity of osteoclasts.- -a is synthesied and released by monocytes and macrophages and may be related to bone remodeling. he afferent bers hae their cell bodies residing in the trigeminal ganglion of ecel cae and transmit electrical signals to the central nerous system. hey ascend the trigeminal spinal tract and enter the trigeminal sensory nuclear complex. rom the trigeminal brainstem complex, the nociceptie signal is transmitted to the thalamus and eentually to the cerebral primary somatosensory cortex, where the location of the signal is discriminated. op-down neural pathways modulate the nociceptie stimuli coming from the periphery. Although seeral brain areas are inoled in pain processing, still little is nown about how pain is encoded in the brain. oweer, it is clear that the pain and salience brain networs oerlap. he initial pattern of pain experienced by patients undergoing traditional multibracet orthodontic appliance therapy has been long studied and well documented.  - Pain appears approximately  to  hours after orthodontic forces are applied to the teeth, with pea leels freuently occurring within the rst  hours after archwire placement, followed by a steady decrease toward baseline leels within  days ig. .. - hese ndings hae been conrmed in seeral racial and ethnic groups - and through the use of ecologic momentary assessment. here also appears to be a diurnal ariation in pain experienced by patients, with higher leels occurring in the eenings and nights. erall, patients are generally able to tolerate and adapt to new appliances within  wee after placement. oweer, female patients in middle adolescence hae been reported to experience more pain than age-matched males and younger patients when exposed to orthodontic procedures. In addition, orthodontic pain is signicantly affected by menstrual phase, with the pain leels being higher

24h 48h 72h

7 days

Fig. 18.1 Trajectory of dental pain after orthodontic procedures.

253

in the luteal phase. hile there is conicting reports on the effect of age on orthodontic pain perception, there is substantial eidence that the type of malocclusion and the amount of crowding hae little effect on pain experienced during orthodontic treatment.  hese ndings suggest that pain is liely most affected by other factors, including hormonal and psychological ariables. ne such example is anxiety, which among other things can be dependent on the relationship with the orthodontic care proider.

Orthodontic Tooth Pain in Clear Aligner Therapy rthodontic pain associated with A has been inestigated in a limited number of studies. A appears to follow a similar pattern of pain progression in terms of peaing at  hours and trending toward baseline leels after  days.,-, oweer, to date, A has mainly been associated with more intermittent forces as compared to conentional treatment with multibracet appliances, although seeral companies are focusing on deeloping materials that may proide more gentle and continuous forces. nly a limited number of studies exist that examine orthodontic pain in patients undergoing A with Inisalign’s latest generation multilayered polyurethane-based polymer, Smartrac. hese studies show a maximum patient-reported pain score of  mm on a -mm isual analogue scale AS, which may be considered mild and of limited clinical signicance.  In preious literature, xceed- thermoplastic material was used in the older generation, and coincidently these studies showed signicantly higher reported pain scores in the rst wee of treatment up to  mm on AS.   imited eidence suggests Smartrac may be more comfortable than older generation materials, but further studies are needed to alidate this. Interestingly, with continued actie tooth moements of the subseuent aligner stages, there is less pain reported by patients compared to the rst stage aligners een if the rst stage aligners are programmed to be passie without actie tooth moements. his perhaps could be a result of the accuracy, t, and deformation of the rst trays, the introduction of iatrogenic posterior occlusal interferences,  or the apprehension and stress inoled with starting orthodontic treatment with a new appliance.  Indeed, pain perception with A, especially during the rst stage, is signicantly related to an indiidual’s psychological stress and anxiety. In general, when compared to traditional multibracet appliances, A results in less reported pain and improed patient experience. iller et al. conducted the rst study ealuating the differences in pain and impact on uality of life experienced by patients undergoing A ersus multibracet appliance therapy. his was a prospectie longitudinal cohort study with  A patients and  multibracet appliance patients. he participants were ased to use a daily diary for  days, measuring functional, psychosocial, and pain-related impacts. he diary consisted of uestions adapted from the eriatric ral ealth Assessment Index, a -point iert scale for demographic data, and a isual analog scale for pain. he results showed that the

254

Principles and Biomechanics of Aligner Treatment

progression of pain in aligner treatment followed a similar pattern to multibracet appliances, in which pain peaed after  hours and gradually returned to normal. Additionally, although the initial leels of pain were higher for the multibracet appliance group, along with higher leels of analgesic consumption, both groups recoered to baseline within  days. In a subseuent study by Shalish et al.,  patients being treated by either buccal multibracet appliances, lingual multibracet appliances, or A were recruited to complete a health-related uality of life uestionna ire  - and a -point scale for dysfunction during the rst wee and on day . heir results showed the aerage initial pain leels were consistently higher in the lingual multibracet appliance and clear aligner groups, with analgesic consumption paralleling the dynamics of the pain leels although the difference did not reach statistical signicance. In all groups, the pain leels subsided within  wee. hese results contradict the ndings by iller et al., which the authors attributed to a greater mechanical force being applied in the aligner group compared to the buccal multibracet appliance group. o further elucidate and compare pain leels between these orthodontic treatment modalities, uiyama et al. conducted a prospectie clinical trial with  patients receiing either A, multibracet appliance therapy, or a hybrid treatment combining both modalities. sing AS, the participants were ased to record their pain leels at time points of  seconds,  hours,  hours, and  to  days post appliance insertion. his was repeated at wees  and  after appliance deliery. heir results illustrated a similar pattern of pain progression during the rst wee of appliance deliery for all groups studied. oweer, the oerall pain leels were signicantly more intense and longer lasting for the multibracet appliance group than either the aligner or the hybrid group. In a recent study by hite et al., patients were randomly allocated to either clear aligner or multibracet appliance treatment groups to inestigate differences in their pain leels. he participants were ased to complete a daily diary with pain measured on AS. he diary was completed at initial appliance deliery, daily for the rst wee, as well as the rst  days after their next two follow-up appointments. he pattern of pain progression during the rst wee following initial appliance actiation was in general agreement with preious studies.,,,,, he clear aligner group experienced consistently lower discomfort than the multibracet appliance group during most of the rst wee, with statistically signicant differences obsered after  to  days. oreoer, analgesic consumption was more freuent in the multibracet appliance group, and their rate of consumption closely mirrored the pattern of pain progression during the rst wee. Similarly, oer a relatiely longer term of  months, the leel of pain was less in the aligner group than the multibracet appliance group. he patients in the multibracet appliance group may hae experienced an increased initial inammatory response, which led to increased sensitiation of the nociceptors and higher pain sensation in subseuent follow-up appointments. he results of hite et al., uiyama et al., and iller et al. comparing pain and discomfort between A and

multibracet appliances are in general agreement with one another, as well as with past studies that demonstrated multibracet appliances may cause more pain than remoable appliances.,,, As mentioned earlier, these results were in contrast to the ndings from Shalish et al., who reported the pain was greater in patients treated with aligners than multibracet appliances. ne possible explanation for this discrepancy could be the ariations in the initial archwires used between the studies. or example, the classic nicel titanium ii or nitinol wires used in the Shalish et al. study hae been shown to display higher pea discomfort than the superelastic copper ii wires used in hite et al., urthermore, the hite et al. study was the only one to utilie Smartrac, a new aligner material brought to maret by Align echnology in ,, whereas the preious studies used the older xceed- aligner material. imited eidence suggests Smartrac may be more comfortable than preious materials, although further studies are needed to erify this. astly, Shalish et al. speculated that the differences in pain leels obsered may possibly hae been due to a higher leel of mechanical force being applied early in treatment for the aligner group. In summary, although orthodontic pain exists with A, the current eidence seems to suggest it is of a lesser degree than multibracet appliances, especially during the rst wee. oweer, additional studies proiding more substantial data are needed. As would be expected, actiation in the aligner tray has been reported as the most freuent cause of pain and discomfort. oweer, other issues leading to pain in association with clear aligners might include nonsmooth edges, tray, and attachment deformation.

Modulators of Pain: Psychological actors linical and pain assessment literature continues to be focussed on identifying and managing specic cognitie and psychological factors that are related to the indiidual’s experience of pain. In orthodontics, pain is a common seuela and expected with treatment. oweer, it is apparent clinically that the perception of pain aries considerably across indiiduals when the same stimulus, such as an initial light archwire, is actiated. he expected pain from an orthodontic adustment is generally belieed to be relatiely minor and self-limiting howeer, some patients will report a much different experience. It is generally accepted that particular affectie and cognitie behaioral factors contribute to these differences in indiidual pain perception. Specically releant to medical and dental settings, pain perception is inuenced by factors such as somatosensory amplication, anxiety, depression, and catastrophiing.- It has been shown that patients with prolonged pain during orthodontic treatment exhibit higher leels of anxiety than indiiduals with pain of short duration. urthermore, experimentally induced orthodontic pain ia elastomeric separators is greater in indiiduals who exhibit higher leels of trait anxiety and somatosensory amplication—a tendency to perceie normal somatic and isceral sensations as being relatiely intense, noxious, and

18 • Pain During Orthodontic Treatment: Biologic Mechanisms and Clinical Management

disturbing—as compared to indiiduals with low leels of both. f importance, anxiety and other mood disorders hae been found to be related to increased freuencies of waing-state oral parafunctional behaiors, such as waetime tooth clenching,- which are also associated with temporomandibular disorders.,, herefore, it might be uestioned whether anxiety, orthodontic pain, and aw motor behaior are intertwined. ecently, we performed a large web surey and recruited  indiiduals subdiided into groups with high, intermediate, and low leels of trait anxiety., lastomeric separators were applied to the molars and pain and freuency of tooth clenching episodes were recorded for  days. A signicant correlation orthodontic pain and freuency of tooth clenching was obsered. In participants with high anxiety, the decrease in orthodontic pain was paralleled by a decrease in the freuency of waetime tooth clenching episodes. hese results suggest that indiiduals with high trait anxiety may respond with an aoidance behaior decrease of aw motor actiity to orthodontic stimuli as a method to reducing their pain experience. he relationship between aw motor actiity and orthodontic pain is supported by a recent study that demonstrated a reduced masticatory performance in orthodontic patients during the period in which they reported the maximum leels of pain and creicular I-b. oweer, there is some eidence of increased aw muscle actiity with A,, leading to aw muscle tenderness of limited clinical signicance. ec et al. estimated the contribution of psychological factors to orthodontic pain. f interest, for eery pain catastrophiing scale PS magnication score of  unit higher, the relatie ris of being a high-pain responder was .. agnication refers to an indiidual’s tendency to exaggerate the threat alue of nociceptie inputs. In this study, the authors showed that cold sensitiity signicantly predicts the pain experienced, with those reporting greater scores for cold sensitiity haing greater orthodontic pain. his result supports the hypothesis that somatosensory amplication plays a maor role in orthodontic pain experience. aluation of the aboementioned psychological constructs in a clinical setting utiliing alidated uestionnaires is adisable to identify indiiduals who may be more sensitie to pain and discomfort during orthodontic therapy. Anxiety and symptom perception management might be recommended for those susceptible indiiduals.

Clinical Considerations for the Management of Orthodontic Pain In the last decade, seeral reiews and clinical studies hae been published on the management of orthodontic pain. It is well nown that pharmacologic approaches with oerthe-counter analgesics are effectie in managing orthodontic pain. In particular, acetaminophen paracetamol is usually prescribed in place of SAIs to aoid possible effects on the rate of tooth moement., Indeed, SAIs hae been reported to interfere with the synthesis of prostaglandin  P, which is nown to be an important chemical mediator during the bone remodeling

255

process., A recent ochrane reiew, including  randomied controlled trials s and , participants aged  to  years, did not nd any eidence of a difference in efcacy between SAIs and paracetamol at , , or  hours postinterention. hey concluded that analgesics are more effectie at reducing orthodontic pain than placebo or no treatment. Sandhu and ecie examined the diurnal ariation of pain in  orthodontic patients. onsistent with the aboementioned studies, pain was reported to pea after  hours. Interestingly, during the pea period, orthodontic pain was lower during the afternoon as compared to the night and morning. herefore, the authors suggested that patients should be adised to tae analgesics accordingly and need not be prescribed routine analgesics to be taen eery  to  hours. In addition, they suggested that preemptie administration of analgesics may be more effectie than posttreatment administration, as the traditional administration at regular interals does not consider temporal ariations in orthodontic pain. oweer, the preiously mentioned reiew indicated there is ery low eidence suggesting preemptie ibuprofen gies better pain relief at  hours than ibuprofen taen posttreatment. inally, it must be noted that the combination of acetaminophen plus ibuprofen proides greater analgesic efcacy than acetaminophen or ibuprofen alone. Special considerations should be made for patients with a history of regularly taing pain medications. Indeed, a recent literature reiew which included animal studies suggested that long-term consumption of pain relieers can signicantly affect the rate of orthodontic tooth moement. Surprisingly, they found that animals in treatment with ibuprofen did not show a signicant decrease in orthodontic tooth moement, as some preious human studies had shown. n the other hand, long-term administration of indomethacin, etorolac, and high doses of etoricoxib decreased the amount of tooth moement. oweer, caution should be taen when interpreting these results due to the uestionable uality of eidence that is aailable. Seeral nonpharmacologic approaches hae been considered to manage orthodontic pain. In another recent ochrane reiew, leming et al. included  s with  participants and analyed the effects of low-leel laser therapy , ibratory aduncts, experimental chewing aduncts e.g., bite wafers and chewing gum, and psychosocial and physical interentions on orthodontic pain. hey concluded that laser irradiation may help reduce orthodontic pain in the short term. n the other hand, eidence to support other methods is of low uality. It is the opinion of the authors that nonpharmacologic interentions should be used wheneer possible to reduce orthodontic pain able ., proided they do not expose patients to harm or additional costs during treatment they should be used especially when a medical condition preents the use of recommended analgesics. f foremost importance, clinicians should establish a relationship of trust with patients and improe their communication sills to reduce nocebo and faor placebo effects. erall, a proper pain management approach would reuire a careful baseline assessment of pain predictors, psychological factors, and patient expectations. oreoer, placebo and nocebo effects should be considered when communicating with

256

Principles and Biomechanics of Aligner Treatment

Tale 181 Strategies to educe Pain During Orthodontic Treatment Pharmacologic

onpharmacologic

Doctorpatient communication

Acetaminophen or iuprofen P

n

Cheing adjuncts

n

oleel laser therapy

n

iratory stimulation

mproe pre and posttreatment communication

igh leel of eidence to support pain reduction ith this treatment o leel of eidence to support orthodon tic pain reduction ith this treatment igh leel of eidence to support pain re duction ith this approach

PRN, Pro re nata (As necessary).

patients. lasini et al. highlighted that negatie patientpractitioner interaction should be aoided and that communication with patients should be well-balanced by not proiding excessie negatie information with regard to side effects and limiting information regarding benets.

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. Sturgeon A, autra A. Psychological resilience, pain catastrophiing, and positie emotions perspecties on comprehensie modeling of indiidual pain adaptation. Curr Pain Headache ep. . . Sullian , ishop S, Pii . he pain catastrophiing scale deelopment and alidation. Psychol Assess. -. . ec , arella , handler P, et al. actors associated with pain induced by orthodontic separators. J Oral ehail. -. . aea-elasco , ely-argeot , ilarrasa A, et al. oint hypermobility syndrome problems that reuire psychological interention. heumatol nt. -. . Sullian , horn , aythornthwaite A, et al. heoretical perspecties on the relation between catastrophiing and pain. Clin J Pain. -. . acobsen P, utler . elation of cognitie coping and catastrophiing to acute pain and analgesic use following breast cancer surgery. J ehav Med. -. . ur , udy . Assessment of cognitie-factors in chronic pain—a worthwhile enterprise. J Consult Clin Psychol.  -. . eyneman , remouw , ano , et al. Indiidual-differences and the effectieness of different coping strategies for pain. Cognit Ther es. -. . aton . linical and health serices relationships between maor depression, depressie symptoms, and general medical illness. iol Psychiatry. -. . ec A. A systematic inestigation of depression. Compr Psychiatry. -. . ang , ian , hen , et al. ognitie behaioral therapy for orthodontic pain control a randomied trial. J Dent es. -. . ergius , roberg A, aeberg , et al. Prediction of prolonged pain experiences during orthodontic treatment. Am J Orthod Dento facial Orthop. , e-e. . arsy A, oodson , ane S, et al. he amplication of somatic symptoms. Psychosom Med. -. . ariewic , hrbach , call . ral behaiors checlist reliability of performance in targeted waing-state behaiors. J Orofac Pain. -. . ndo , anemura , anabe , et al. lenching occurring during the day is inuenced by psychological factors. J Prosthodont es. -. . inocur , iel , isha , et al. Self-reported bruxism—associations with perceied stress, motiation for control, dental anxiety and gagging. J Oral ehail. -. . ichelotti A, iof I, esta P, et al. ral parafunctions as ris factors for diagnostic  subgroups. J Oral ehail. -. . Slade , hrbach , reenspan , et al. Painful temporomandibular disorder decade of discoery from PPA studies. J Dent es. -.

. how , iof I. ffects of trait anxiety, somatosensory amplication, and facial pain on self-reported oral behaiors. Clin Oral nvestig.  -. . Spielberg , orsuch , e . Manual of the StateTrait Aniety nventory. Palo Alto onsulting Psychologists Press . . how . Effects of Aniety and Daytime Clenching on Orthodontic Pain Perception. niersity of oronto . . ameiro , Schult , rein P, et al. Association among pain, masticatory performance, and proinammatory cytoines in creicular uid during orthodontic treatment. Am J Orthod Dentofacial Orthop. -. . astroorio , argellini A, ucchese A, et al. ffects of clear aligners on sleep bruxism randomied controlled trial. J iol egul Homeost Agents. -. . ou , ran , astroorio , assi A, iof I. aluation of masticatory muscle response to clear aligner therapy using ambulatory electromyographic recording. Am J Orthod Dentofacial Orthop. e-e. . Arias , arue-roco . Aspirin, acetaminophen, and ibuprofen their effects on orthodontic tooth moement. Am J Orthod Dentofacial Orthop. -. . oche , isneros , Acs . he effect of acetaminophen on tooth moement in rabbits. Angle Orthod. -. . eier , anda S, urrier , et al. he effects of exogenous prostaglandins on orthodontic tooth moement in rats. Am J Orthod Dentofacial Orthop. -. . yroola , Spyropoulos . ffects of drugs and systemic factors on orthodontic treatment. uintessence nt. -. . on A, arrison , orthington , et al. Pharmacological interentions for pain relief during orthodontic treatment. Cochrane Dataase Syst ev. . . Sandhu S, ecie . iurnal ariation in orthodontic pain clinical implications and pharmacological management. Semin Orthod. -. . ng , Seymour A, ir P, et al. ombining paracetamol acetaminophen with nonsteroidal antiinammatory drugs a ualitatie systematic reiew of analgesic efcacy for acute postoperatie pain. Anesth Analg. -. . arygiannais A, alamanos , Athanasiou A. oes longterm use of pain relieers hae an impact on the rate of orthodontic tooth moement A systematic reiew of animal studies. Eur J Orthod. -. . leming PS, Strydom , atsaros , et al. on-pharmacological interentions for alleiating pain during orthodontic treatment. Cochrane Dataase Syst ev. . . lasini , osas S, olloca . Placebo hypoalgesic effects in pain potential applications in dental and orofacial pain management. Semin Orthod. -.

19

Retention and Stability Following Aligner Therapy JOSEF KUČERA and IVO MAREK

Retention and Stability in Orthodontic Treatment INTRODUCTION Orthodontic treatment is an area of medicine and dentistry that has to address not just health and function but also aesthetics. It is usually the aesthetic considerations that make patients seek out orthodontic treatment in the rst place. Achieving an excellent aesthetic and functional result can be lengthy and expensive, therefore it is in the interests of both the patient and the clinician that the result of orthodontic treatment remains stable in the long term. Unfortunately the importance of the retention phase is often underestimated, hen in reality it is as important to the patients as the active orthodontic treatment itself. he period after the completion of active treatment can be divided into a retention period and a postretention period. he purpose of the retention phase folloing active orthodontic treatment is to prevent relapse dened as the natural tendency of the teeth to migrate into their original position in the dental arch and to eliminate the inuence of other factors that might destabilie the result. It is very dif cult to say ho long the retention phase should last. he literature offers many recommendations, although they vary considerably and are often vague. ome authors sug gest that, folloing orthodontic treatment, teeth should be held in the position achieved by treatment for as long as it is necessary to sustain the result, or that the retention phase should be as long as needed and as short as possible. Others suggest that retainers should be used until the patient’s groth is complete or the third molars erupt, or for a period of  years or even  years, or simply as long as the patient ishes to keep the teeth aligned. It is generally recommended that nongroing patients ear retainers for at least  year and is biologically dened as the completion of the reorganiation of bone and peri odontal ligaments around the teeth. ollagen bers are reorganied ithin the rst  to  months. his period is critical, and the earing of retention appliances is essential because relapse is very likely at this stage after this critical period the risk decreases substantially. oever, the reor ganiation of elastic supracrestal bers may take more than  year, hich makes the retention of severely rotated teeth particularly difcult some authors recommend adjunctive surgical procedures such as berotomy to decrease the amount of relapse., In groing patients retainers should be orn until the groth is complete. At the time patients stop earing the retention appliances, the postretention period begins, and it is only then that e get a true picture

of the stability of the original result that had been achieved by the orthodontic treatment. uring the postretention period numerous factors and the complexity of their inter actions may ultimately destabilie treatment results.

FACTORS INFLUENCING LONG-TERM STABILITY ith regard to stability there are some general guidelines and recommendations for orthodontic treatment, and so long as these are respected hen making and carrying out the treatment plan they tend to produce stable results ith relatively little risk of relapse. In such cases, longterm changes in dental arches of treated patients are then simi lar to those occurring in untreated subjects. efore starting treatment, orthodontists need to keep in mind that the position of the teeth and the shape of the dental arches are the balanced result of many factors, espe cially the inuence of the forces exerted by the surrounding soft tissues i.e., pressure from the cheeks, lips, and tongue that create a “neutral one” or “one of stability.” Orthodon tic movement of the teeth outside of this neutral one pushes them into an unbalanced one, ith conseuent relapse., he shape of the dental arch, particularly the mandibular arch, should therefore be respected in the plan ning and implementation of treatment because changes in arch shape tend to relapse into the original shape in the long term., he upper dental arch may be expanded more than the loer arch in indicated cases rapid maxillary expansion hoever, even in these cases, the longterm sta bility appears to be uite problematic. Any changes in the loer intercanine distance are also very prone to relapse,, partly because decrease in the loer intercanine distance is due to the natural changes that occur in the dental arch as a result of aging., he uality of articulation and inter cuspation can also be very important for the longterm sta bility.,, he correct intercuspation of the teeth in lateral segments ith high cusps itself provides the best retention, both in sagittal and transverse dimensions. It is also impor tant to achieve the correction in the vertical direction, and especially for sufcient correction of the deep bite, as its deepening reduces the space for the loer incisors. Incisor shape can also be a source of posttreatment instability. In triangularshaped incisors, recontouring of the approximal surfaces i.e., interproximal enamel reduction, stripping provides more stable contact beteen the incisors. Accord ing to some studies, this stabiliing effect of loer incisor stripping is comparable to the efciency of bonded retain ers., imilarly, the adjustment of large proximal enamel ridges on the palatal surfaces of the upper incisors is also important for the stability of the incisor region. 259

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ontinuing groth is a separate issue and needs to be addressed ith particular attention in more pronounced skeletal malocclusions, especially in the sagittal and vertical dimensions, hich continue to gro over a longer period than in the transverse dimension. Unfavorable groth of the jas has a negative impact on the occlusal relationship and on the position of incisors due to the dentoalveolar compensation process. his is one of the reasons hy it is recommended to plan comprehensive treatment of severe skeletal malocclusions after the patient’s groth is com plete. oever, even after groth completion, the dental arches are also subject to changes related to the patient’s aging, and these processes are in fact lifelong and may result in the development of irregularities in the incisor seg ment    that often bring patients back for retreatment.

Retention Protocols and the Choice of Retention Appliance RETENTION PROTOCOLS o date, there is no universal retention protocol, and there is insufcient highuality scientic literature to reliably

A

establish such a protocol in terms of the length of the reten tion phase, the earing regime, and the choice of type of retention device.  his is because e cannot generalie a single procedure for patients ho differ in diagnosis, sever ity of the malocclusion, age, type of groth, treatment type, and uality of treatment result. hus the choice of retention device should alays be individualied, ith consideration of all the potential factors of instability men tioned earlier. his approach is called “differential reten tion,” meaning that for every patient, orthodontists must focus and aim the retention on those points that pose the greatest threat and risk of relapse in the individual patient ig. .. According to surveys on retention protocols, the most common retention devices are the aley retainers and clear thermoplastic retainers. or the mandible, a xed retainer is often indicated, either on its on or in combina tion ith a removable appliance.  An increasing trend has been observed in the use of thermoplastic retainers, hich patients prefer because of their good aesthetics and inconspicuousness. A similar trend can also be observed ith xed retainers in both jas. In terms of the freuency of use of the various retention devices, an indenite use of xed retainers is recommended by many clinicians.  

B

C Fig. 19.1 Examples of relapse after orthodontic treatment, where either the patient failed to wear the retention appliances after rapid maxillary expansion (A-C) or the retention regime selected was insufcient for a noncompliant patient the rotational relapse of lateral incisors

19 • etention and taility ollowing Aligner Therapy

D

G

E

H

F

I

261

Fig. 19.1, c’ (-) and palatal moement of upper left canine (-) shown could hae een preented y onding a xed retainer and including prolematic teeth

If the decision is made to use a retention appliance long term, a xed retainer seems to be the best option mainly because it prevents relapse of the aesthetically important anterior teeth very efciently and ithout any need for patient cooperation., onded retainers have also been described in the literature as safe, predictable, and posing no health risks to the patient.,, ome studies, hoever, have indicated that there is a tendency toard increased buildup of plaue and calculus around bonded retainers ig. ., having negative conseuences on the periodon tium hoever, this can be minimied ith regular care, exercised by the patient and a dental hygienist.

he biggest disadvantage of bonded retainers that impacts their longterm or lifelong use is failure rate. According to the literature, the failure rate varies idely, from . to ., oever, e believe that the occur rence of common failures, such as abrasion of the layer of adhesive resin caused by food attrition or occlusal contacts, is only a matter of time ig. .. Other considerable risks associated ith prolonged use of bonded retainers are the socalled unexpected complications, here unexpected tooth movement occurs, even hen the integrity of the bonded retainer has not been compromised in any ay. he incidence of these complications is uite small, occurring

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A

B Fig. 19.2 Calculus accumulation and gingial inammation around the lower onded retainer (A and B)

A

B

C

D Fig. 19. Examples of failures of onded retainers (A) The detachment of a composite resin layer is usually a conseuence of onding errors (B) The loss of the adhesie layer due to mastication or premature contact on the onded retainer (C) Premature contact on the retainer wire, wire fatigue, or selection of a wire with insufcient mechanical properties (small diameter dead-soft wire) resulting in fracture of the wire () Extending the upper retainer to the canines increases the ris of fracture, with conseuent wire actiation and unwanted tooth moement (Kucˇera J, Littlewood SJ, Marek I. Fixed retention: pitfalls and complications. riti ental Journal   ( .

in approximately  to  of cases,, but their clinical conseuences can be very severe. In addition, it is estimated that up to  of such cases reuire retreatment. here are to distinct types ig. ., characteried by a torue difference beteen to adjacent incisors  effect or op posite inclination of contralateral canines ist effect.,

hese complications are surprising because they may ap pear after a relatively long period of problemfree retention, often occurring after several years.,, he unanted tooth movement can be so pronounced that the root is moved outside of the alveolar bone ig. ., hich is in many cases accompanied by the occurrence of gingival

19 • etention and taility ollowing Aligner Therapy

A

B

C

D Fig. 19. Two distinct types of unexpected complication of lower onded retainers opposite torue on two adacent incisors ( effect A, B) and opposite inclination of contralateral canines (Twist effect C, ) Both  effect and Twist effect may e accompanied y seere gingial recession (A, C) (,  ro Kucera J, Strelo J, Marek I, et al. reat ent o colication aociated wit lower ed retainer. J Clin Orthod. .

A

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C

Fig. 19.5 nexpected complication of lower onded retainer (Twist effect) lower left canine moing out of the ony enelope (A-C) ignicant ony dehiscence can e identied on dental cone-eam computed tomography (B, C) (Marek I, Kucˇera, J. Twist-effect, X-effect and other unexpected complications of xed retainers – original article. LKS , (.

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Principles and Biomechanics of Aligner Treatment

recession. In such severe cases, orthodontic retreatment is necessary, and often a surgical periodontal intervention may also be needed ig. ..  ongterm or lifelong retention is not ithout risk. It should be indicated ith caution, and it is essential that xed retainers are regularly checked by an orthodontist or during regular dental or hygiene checkups. It is also very important that dentists and dental hygienists ho see the patients most freuently are informed about the retention devices used and

their associated risks, no matter ho small. his is especially important for the dental health care providers to help their patients manage because many of the patients consider the orthodontic treatment completed hen the xed appliance is removed, and their regular attendance for checkups at the orthodontic ofce in the retention phase can be a problem ig. .. It is needless to say that early detection of these complications can minimie the damage to adjacent tissues and facilitate the subseuent care.

A

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C

D

E

F Fig. 19.6 Treatment of a complication associated with a lower onded retainer (A-C) ower left central and lateral incisors seerely proclined y a fractured onded retainer and lingual gingial recessions occurring on oth incisors (-) etreatment with a full lower xed appliance corrected the torue of the incisors and was followed y a periodontal reconstructie surgery

19 • etention and taility ollowing Aligner Therapy

G

H

I Fig. 19.6, c’ (-) inal reconstruction with full porcelain crowns and onding of a new lower xed retainer

100% 90%

Attendance of patients at recall

80% 70% 60% 50% 40% 30% 20% 10% 0% 1

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Years in retention Fig. 19. hen long-term retention is indicated, regular recalls are necessary to chec retainers howeer, attendance of patients decreases in the retention period, as seen on this graph (Fro Kucera J, Marek I. Uneected colication aociated wit andiular ed retainer a retroectie tud. Am J Orthod Dentofacial Orthop .

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APPLIANCES FOR RETENTION AND INDICATIONS OF ARIOUS RETENTION DEICES ased on the biologic principles and knoledge of factors that inuence the position of teeth in the retention phase, several combinations of retention appliances have been recommended. ost often a removable aley retainer ith van der inden labial bo and Adams clasps on the rst molars is used for both the upper and loer jas ig. .. aley retainers are orn largely during the nighttime only. he second option is clear thermoplastic retainers, suitable for both night and daytime ear ig. .. aley retainers are indicated especially for patients ho have need for an increased stabiliation of the canine positions. Other typical indications are patients after transverse expansion or after treatment of a deep bite hen the appliance is also serving as a bite plate. In class II cases here intermaxillary elastics or a bitejumping device as used, an activator ith van der inden labial bo and Adams clasps on maxillary molars ig. . or to clear thermoplastic appliances ith class II precision ings should be considered. In the majority of patients, each of these removable retainers is used in combination ith an upper or loer bonded retainer. onded retainers are most often made of thin multistrand exible steel archires of various strengths and ith various cross sections most of ten the cross section varies beteen . and .in. he ire is shaped and passively attached by a o compos ite resin to all anterior teeth in the loer ja canines and incisors on the lingual surface, preferably in the apical third of

teeth. Alternatively, thick monolament stainless steel, cobalt chromium or titaniummolybdenum ires bonded only to the canines can be used cross section ranges beteen . and . in. In the upper arch, xed retainers most often are limited only to the incisor segment, hile in some patients ith increased need for canine stabiliation e.g., palatally or buc cally impacted canines the canines are also included in the bonded retainer ig. .. he use of xed retainers is par ticularly necessary in patients ith compromised periodontal health, here they also serve as periodontal splints, as ell as in patients ith spacing or midline diastemas, after compli cated space closure folloing extractions, severe tooth rota tions, open bite, or ith impacted canines, or even as a space maintainer before dental implants are placed ig. ..

SPECIFICS OF RETENTION FOLLOING CLEAR ALIGNER TERAPY eneral principles that apply in treatment planning and that fundamentally inuence the occurrence of relapse and the stability of treatment are eually relevant in the treat ment by xed or clear aligner appliance treatment. o ever, the retention phase folloing orthodontic treatment using clear aligners is different to some extent from that folloing use of xed appliances. hen planning retention after clear aligner therapy A, the greatest disadvantage is the complicated achieve ment of nal articulation and intercuspation in the poste rior segments, as opposed to xed appliance treatment, here an ideal occlusal contact can be achieved in the nal

A

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Fig. 19. awley retainer with frontal ite plane in occlusal (A), front (B), and lateral (C) iews

19 • etention and taility ollowing Aligner Therapy

A

26

B Fig. 19.9 acuum-formed thermoplastic retainer in the upper aw in frontal iew (A) and smile (B)

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Fig. 19.10 etention actiator after class  treatment in lateral right (A), frontal (B), and lateral left (C) iews

stage of treatment by use of settling elastics. In A, a posterior open bite often occurs. his may be a conseuence of various factors, including premature anterior contact of incisors ig. . due to insufcient intrusion of loer incisors or incorrect torue of upper or even loer incisors. In addition, the intrusive inuence of masticatory forces on aligners in the posterior segments plays an important role. his situation can be solved by additional aligners never theless, even then a slight open bite often persists. In these

cases, posterior teeth need to be alloed to achieve their best possible contact natural settling ith their antagonists. In this regard, the use of clear aligners for retention may not be appropriate, as it might hinder this natural process entirely, thereby making the settling less effective than hen aley appliances are used ig. .. On the other hand, the abovementioned intrusion effect of clear aligners on the posterior segments is advanta geous hen treating openbite cases. ompared to the

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Principles and Biomechanics of Aligner Treatment

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F Fig. 19.11 ifferent types of commonly used xed retainers pper retainers can include incisors only (A), or een oth canines, either continuous (B) or segmented (C) the segmented ersion is more suitale ecause premature contact on the retainer can e aoided, therey decreasing oth the incidence of fracture and the adhesie layer () ower xed retainer usually includes canines and incisors estiular retainers can e used after difcult extraction space closure (E) or as a space maintainer prior to implant placement ()

xed appliance treatment, clinically signicant intrusion of molars and premolars can be achieved even ithout using temporary anchorage devices. hese intrusion movements also seem to be very stable, though valid data to verify this premise are lacking currently ig. . In openbite cases here incisor extrusion is a part of the treatment, it is important that both upper and loer xed retainers extending from canine to canine are used as part of the retention protocol. Additionally, it is essential that

all teeth in the upper and loer arches are included in thermoplastic retainers to prevent unanted eruption of the last molars and conseuent reopening of the bite ig. .. he apparent advantage of A is the nal position of the loer incisors can be predicted very precisely during treatment planning, alloing the clinician to predict and reduce unanted proclination of incisors and thus expected relapse as ell ig. .. herefore functions

19 • etention and taility ollowing Aligner Therapy

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H Fig. 19.12 Examples of typical indication in which use of xed retainers is recommended (A, B) ifcult extraction space closure (C, ) arge midline diastema closure in a periodontally compromised patient (E, ) pace closure in a patient with generalied spacing (, ) eere crowding and tooth rotations

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Principles and Biomechanics of Aligner Treatment

A

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F Fig. 19.1 (A, B) ateral open ite often occurs after aligner treatment (C, ) The clinical picture at the end of treatment may thus differ when compared to the nal situation depicted in the treatment planning software (E, ) oweer, the clinical situation after  years in recall shows that the teeth will eentually settle into the desired position

like grip and superimposition in treatment planning softare should be included in the standard protocol hen planning nonextraction therapy in cases of croding or in class II cases here use of elastics is planned. espite providing exact control of the loer incisor position, xed retainers may still be recommended as the most reliable retention method for stabiliing the position of the loer incisors in the long term. After class II treatment, the use of a retention activator in construction bite or thermoplastic retainers ith precision ings should be considered to maintain the interarch occlusal change. In crossbite cases here transverse expansion as performed, it is more suit able to use a removable retention plate because it is more rigid and maintains the nal transverse dimension better and can be easily adjusted by selective grinding here settling is needed to nalie the articulation.

RETENTION PROTOCOL AND SCEDULE OF CECUPS IN TE RETENTION PERIOD In standard cases the folloing retention protocol is used in our institution In the rare cases hen patients do not have a bonded maxillary xed retainer, fulltime ear of the reten tion appliance for the rst  months is recommended this most often involves a thermoplastic retainer during the day and a aley appliance overnight, achieving  hours of retainer ear, ith the exception of time that the patient spends eating, drinking, teeth brushing, and possibly partici pating in sport activities after the month period, the patients are then asked to ear retention appliances over night for the rest of the rst year of retention, folloed by every other night in the second year, tice a eek in the third year, and once a eek afterards hen a xed retainer is

19 • etention and taility ollowing Aligner Therapy

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D Fig. 19.1 atural settling of teeth after orthodontic treatment in recall after  months, as isualied on T scans of a patient wearing a awley retainer at nighttime (A, B) and a thermoplastic retainer (C, )

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Principles and Biomechanics of Aligner Treatment

A

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F Fig. 19.15 Treatment of an open ite with aligners that was facilitated y intrusie force in the lateral segments

used, the protocol remains the same, except that the remov able appliance is orn only at nighttime from the beginning. xceptions to the general protocol include groing patients ith sagittal or vertical malocclusions, ho should continue to ear retention appliances until their groth is nished, and patients ho have undergone orthognathic surgery or those ith compromised treatment results, here an increased tendency to relapse may be expected, ho are also recommended a prolonged retention period. atients are instructed to attend regular checkups throughout the retention period. he recommended sched ule is once every  or  months during the rst year, tice a year in the second year, and at least once a year thereaf ter. urrently there is a tendency to maintain the bonded

retainers indenitely and independently of the original malocclusion but only after a prior agreement ith the patient. atients are instructed that the retention may be discontinued at some point but that their dentition is sub ject to continuous change throughout their lives, and this change may manifest itself in the occurrence of various irregularities in the aesthetically exposed anterior segment. hus patients must either accept the risk of these changes or they must continue ith a bonded or removable retainer if they ant to maintain their teeth alignment. oever, ith due respect to the expected and unexpected complica tions associated ith the prolonged use of a bonded retainer, they need to be checked regularly, at least once a year.

19 • etention and taility ollowing Aligner Therapy

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F Fig. 19.16 elapse of anterior open ite due to short retention thermoplastic retainers and conseuent extrusion of second molars ituation after treatment (A-C) and  years in recall (-)

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Fig. 19.1 Treatment planning software can e used to plan the position of lower incisors exactly, aoiding unwanted proclination of the lower incisors and thus preenting the ris of relapse

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2

Principles and Biomechanics of Aligner Treatment

References . oyers . andboo of Orthodontics for the Student and eneral ractitioner. rd ed. hicago earbook edical ublishers . . amínek . Ortodoncie. st ed. raha alén . . achrisson U, üyükyilma . onding in orthodontics. In raber , anarsdall , ig , eds. Orthodontics Current rinciples and echniues. th ed. hiladelphia, A osby lsevier  chap . . achrisson U. ongterm experience ith direct bonded retainers update and clinical advice. J Clin Orthod. . . ooth A, delman , roft . entyyear folloup of patients ith permanently bonded mandibular caninetocanine retainers. Am J Orthod Dentofacial Orthop. . . roft , ields , arver . Contemporary Orthodontics. th ed. t. ouis, O osby lsevier . . eitan . linical and histologic observations on tooth movement during and after orthodontic treatment. Am J Orthod.  . . van eeuen , altha , uijpersagtman A, et al. he effect of retention on orthodontic relapse after the use of small continuous or discontinuous forces. An experimental study in beagle dogs. Eur J Oral Sci. . . oese . Increased stability of orthodontically rotated teeth follo ing gingivectomy in acaca nemestrina. Am J Orthod.  . . dards . A longterm prospective evaluation of the circumferential supracrestal berotomy in alleviating orthodontic relapse. Am J Orthod Dentofacial Orthop. . . einstein , aack , orris , et al. On an euilibrium theory of tooth position. Angle Orthod. . . de la ru A, ampson , ittle , et al. ongterm changes in arch form after orthodontic treatment and retention. Am J Orthod Dentofacial Orthop. . . Alexander . he Aleander Discipline ongerm tability. anover ark uintessence . . agravére O, ajor , loresir . ongterm dental arch changes after rapid maxillary expansion treatment a systematic revie. Angle Orthod. . . ittle , iedel A, Årtun . An evaluation of changes in mandibular anterior alignment from  years postretention. Am J Orthod. . . ahlieke , ischbach , chare . ostretention croding and incisor irregularity a longterm folloup evaluation of stability and relaps. r J Orthod. . . inclair , ittle . aturation of untreated normal occlusions. Am  Orthod. . . ishara , reder , amon , et al. hanges in the dental arches and dentition beteen  and  years of age. Angle Orthod. . . de reitas , anson , de reitas , et al. Inuence of the uality of the nished occlusion on postretention occlusal relapse. Am J Orthod Dentofacial Orthop. .e.e. . achrisson U. Important aspects of longterm stability. J Clin Orthod. . . Aasen O, speland . An approach to maintain orthodontic alignment of loer incisors ithout the use of retainers. Eur J Orthod. . . dman ynelius , etrén , ondemark , et al. iveyear postretention outcomes of three retention methods—a randomied controlled trial. Eur J Orthod. . . achrisson U. Important aspects of longterm stability. J Clin Orthod. . . nlo , uroda , eis A. Intrinsic craniofacial compensations. Am J Othod. .

. slambolchi , oodside , ossou . A descriptive study of mandibular incisor alignment in untreated subjects. Am J Orthod Dentofacial Orthod. . . ehrents . roth in the aging craniofacial skeleton. onograph , raniofacial roth series. Ann arbour enter for uman roth and evelopment University of ichigan . In anda , anda . onsiderations of craniofacial groth in longterm retention and stability is active retention needed Am J Orthod Dentofacial Orthop. . . ittleood . videncebased retention here are e no Semin Orthod. . . ittleood , illett , oubleday , et al. etention procedures for stabilising tooth position after treatment ith orthodontic braces. Cochrane Database Syst Rev. . . ratt , luemper , artseld r , et al. valuation of retention protocols among members of the American Association of Orthodontists in the United tates. Am J Orthod Dentofacial Orthop. . . enkema A, ips , ronkhorst , et al. A survey on orthodontic retention procedures in the etherlands. Eur J Orthod.  . . oland , ichens , illiams A, et al. he effectiveness of aley and vacuumformed retainers a singlecenter randomied controlled trial. Am J Orthod Dentofacial Orthop. . . ai , rossen , enkema A, et al. Orthodontic retention procedures in iterland. Swiss Dent J. . . admos A, udalej , enkema A. pidemiologic study of orthodontic retention procedures. Am J Orthod Dentofacial Orthop. . . Årtun , padafora A, hapiro A. A year folloup study of various types of orthodontic caninetocanine retainers. Eur J Orthod. . . enkema A, enkema A, ronkhorst , et al. ongterm effectiveness of caninetocanine bonded exible spiral ire lingual retainers. Am J Orthod Dentofacial Orthop. . . Årtun . aries and periodontal reactions associated ith longterm use of different types of bonded lingual retainers. Am J Orthod. . . andis , lahopoulos , adianos , et al. ongterm periodontal status of patients ith mandibular lingual xed retention. Eur J Orthod. . . ogers , Andres . ependable techniue for bonding a  x  retainer. Am J Orthod Dentofacial Orthop. . . törmann I, hmer U. A prospective randomied study of different retainer types. J Orofac Orthop. . . ucˇera , arek I. Unexpected complications associated ith mandibular xed retainers a retrospective study. Am J Orthod Dentofacial Orthop. . . atsaros , ivas , enkema A. Unexpected complications of bonded mandibular lingual retainers. Am J Orthod Dentofacial Orthop. . . arek I, ucˇera . isteffect, effect and other unexpected complications of xed retainers. LS. . . aera , udalej , atsaros . evere complication of a bonded mandibular lingual retainer. Am J Orthod Dentofacial Orthop. . . ucˇera , treblov , arek I, et al. reatment of complications associated ith loer xed retainers. J Clin Orthod.  . . rátná , arek I, ycová . ettling after orthodontic therapy according to type of retention. Ortodoncie. . . annessy , arvey , AlAadhi A. A randomied clinical trial comparing mandibular incisor proclination produced by xed labial appliances and clear aligners. Angle Orthod. .

20

Overcoming the Limitations of Aligner Orthodontics: A Hybrid Approach LUCA LOMBARDO and GIUSEPPE SICILIANI

Introduction Aligners were rst introduced by Kesling1 in 1945 to correct crowding. Later, Ponitz2 reorted te use o a reoable lastic retainer ssi, entsly, or, PA, A. oweer, it was not until te 199s, wen eridan et al. cobined tese retainers wit interroial reduction P, tat tey began to gain oularity. en, in 1999, ia isti and Kelsey irt, togeter wit a couter secialist, ounded Align ecnology in Palo Alto, A, A.4 ince tey launced teir nisalign brand into te aret, te deand or ortodontic aligners as been growing aong atients esecially adults, tans to teir estetic roerties and clinical ecacy.5 At rst, aligners were areted as an alternatie to traditional ed aliances in sile alocclusion cases inoling sligt crowding or inor sace closure. er tie, oweer, te range o alocclusion cases tat can be treated by eans o inisible aligners as broadened. linical researc as deeloed aligner-based solutions or een cole cases inoling aor rotation o te reolars, uer incisor torue, distalization, andor etraction sace closure. esite te claied eciency o aligner treatent, oweer, its clinical otential still reains controersial aong clinicians. ts adocates are coninced by te clinical eidence arising ro successully treated cases, wile setics oint to te signicant liitations o te tecniue, esecially in te treatent o cole alocclusions.-11 rtodontics coanies clai tat aligners can resole, witout te use o additional tecniues, rotations o 4 degrees at te uer and lower central incisors, 45 degrees in canines and reolars,  degrees in lateral incisors, and 2 degrees in olars. trusions and intrusions o 2.5  ae been acieed in anterior teet, and root oeents o 4  and 2  ae been reorted in osterior teet.12 eerteless, ew studies ae been ublised to suort tese clais, wic are not always suorted by te eerience o oter clinical ractitioners. n act, soe ortodontists indicate tat te nuber o atients wo reuire soe unlanned correction or een recourse to ed ortodontics is closer to  to .5 1 Kraitz reorted tat nisalign aligners ad a ean accuracy o 41 in ters o acieing lanned outcoes, wit te ost redictable oeent being lingual contraction 4.1 and te least redictable etrusion 29..14

n te attet to clariy te situation, Lagraère and lores-ir15 ublised te rst systeatic reiew on te subect in 25. ince ten, seeral autors ae roided udated eidence on aligner ecacy.12,1-1 e ost recent systeatic reiews into te accuracy o ortodontic oeents acieable wit aligners ae concluded tat tey are able to roduce distal oeent o te uer olars and resole anterior crowding issues troug incisor rotrusion and by increasing te intercanine, interreolar, and interolar distances. n te oter and, reoable aligners are ar less eectie at acieing transerse eansion ia bodily oeent o te osterior teet. urterore, tey are unable to eror canine and reolar rotations satisactorily, and see to all sort in ters o etrusion oeents and control o oerbite and occlusal contacts. earing in ind tis eidence, our clinical eerience, and te eer-growing oularity o aligner treatent, we ae deeloed a new ybrid aroac using a cobination o dierent deices to oercoe soe o te ost coon liitations o reoable aliances.

Transverse Expansion of the Posterior Teeth esearc as sown tat aligners are unable to eror redictable bodily reolar and olar eansion. igital setus tend to oerestiate bodily eansion oeents, and ore tiing tan lanned occurs.19-21 oweer, in clinical cases ig. 2.1 in wic te osterior sectors are greatly negatiely inclined, it is ossible to lan uncontrolled tiing o te uer and lower canines, reolars, and olars. urterore, te sace needed to resole crowding can be created by using aligners alone ig. 2.2 to eert ressure on te lingual suraces o te teet tis iroes te arcor by signicantly increasing te intercanine, interreolar, and interolar distances ig. 2.. n act, Lobardo et al.22 ae deonstrated tat tis estibulolingual tiing can be acieed wit a redictability o 2.9. at being said, in young atients wit transerse decits due to yolasia o te uer aw ig. 2.4, it is not realistic to eect aligners to aciee seletal alteration. nly an ortoedic aroac, rst on te deciduous teet ig. 2.5 and ten ia seletal ancorage2 ig. 2., is able to noralize te aillary diensions and tereore 275

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Fig. 20.1 Initial intraoral photographs of adult patient with class I malocclusion dentoalveolar contraction in both arches.

Fig. 20.2 Intraoral photographs during aligner therapy with composite buttons.

20 • Overcoming the Limitations of Aligner Orthodontics: A ybrid Approach

277

Fig. 20.3 inal intraoral photographs after step aligner treatment.

erit correct erution and iroe te transerse and sagittal occlusal relationsis. oweer, in suc atients, aligners ig. 2. can be used as an ecacious tool or coleting dental alignent and creating accetable intercusidation witout decoensating te class  alocclusion ig. 2.. t is not only in cildren tat suc robles arise, oweer in adult atients,24 te redictability o transerse eansion ia bodily oeent o te reolars and olars is oor, and ay be daaging in atients wit tin eriodontal tissues or gingial recession ig. 2.9. ence in adults it is best to resole issues o seletal aillary contraction ia surgery or seletal ancorage eanders bone-bone raid

alatal eander ig. 2.1. nly ater te transerse decit as been resoled sould crowding be addressed, and in suc cases te occlusion can be iroed by eans o aligners ig. 2.11, wic can guide te etrusion o te teet in a controlled asion. is aroac lessens te ris o reature contacts, unwanted estibular oeent, and worsening gingial recession ig. 2.12.

Canine and Premolar Rotation t as been deonstrated tat te andibular canine is te ost dicult toot to control wit aligners and tat te

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Fig. 20.4 Initial intraoral photographs of a young patient with sel etal and dental class III and narrow upper aw.

Fig. 20.5 apid palatal epansion with arms for elaire mas on de ciduous second molars.

Fig. 20.6 ybrid epander with dental and seletal anchorage in up per aw and arms for elaire mas.

20 • Overcoming the Limitations of Aligner Orthodontics: A ybrid Approach

Fig. 20.7 Intraoral photograph during aligner therapy.

279

aount o rotation actually acieable wit te aillary and andibular canines is rougly a tird o tat redicted.25 or reolars, te rotation accuracy o aligners as been reorted witin te range 2.2 to 41..2 e diculty in derotating cylindrical teet by eans o aligners is liely due to te act tat tey are unable to gri tese teet suciently to generate a orce coule. is ay be ascribable to oor aligner tting andor ecessie stiness o te aliance itsel. uerous otential solutions to tis roble ae been roosed in recent years. or eale, in a case o crowding wit a seerely rotated lower canine and uer incisor ig. 2.1, coosite buttons were alied on te lingual side o te aligner ig. 2.14 to increase te gri, and derotation was lanned in only 2 stes. e good elasticity2 and t ig. 2.15 o 22 aligners weden  artina, ue arrare, taly, in addition to careul striing,

Fig. 20.8 inal intraoral photographs after step aligner treatment.

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Fig. 20.9 Initial intraoral photographs of adult patient with seletal contraction of upper aw class III tendency and gingival recession in both arches.

Fig. 20.10 apid palatal epansion with seletal anchorage APA method.

Fig. 20.11 Intraoral photograph during aligner therapy.

20 • Overcoming the Limitations of Aligner Orthodontics: A ybrid Approach

Fig. 20.12 inal intraoral photographs after aligner therapy.

Fig. 20.13 Initial occlusal intraoral photographs of an adult patient with severe rotation of the upper incisors A and right lower canine B.

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Principles and Biomechanics of Aligner Treatment

Fig. 20.14 Occlusal intraoral photographs during treatment with composite buttons on the lingual surfaces of teeth . . . and ..

Fig. 20.15 Intraoral photograph during aligner therapy.

roided satisactory alignent, witout recourse to ultile reneents, witin a liited tierae ig. 2.1. e ae recently deeloed a new ybrid aroac to increase te redictability o rotations, wic is one o te aor liitations o aligner treatent.1-1 n cases o rotations o 2 degrees or aboe ig. 2.1, it is ossible to include icrotubes wit a circular cross section in te setu to be ositioned across te lingual surace o te rotated teet ig. 2.1. e setu can be erored in suc a way tat te aligners coer tese sections witout actually toucing te ig. 2.19. is enables te clear aligner to guide te oeent o te teet, eliinate unwanted oeents, and increase atient coort. y tese eans we acieed correct rotation in only 1 stes witout any reneents or

Fig. 20.16 inal intraoral photographs after step aligner treatment.

20 • Overcoming the Limitations of Aligner Orthodontics: A ybrid Approach

Fig. 20.17 Initial photographs of a young patient with rotation greater than  degrees of left upper canine and left second premolar.

Fig. 20.18 Application of microtubes on rotated mesial and distal teeth.

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Principles and Biomechanics of Aligner Treatment

A

B

C

D

Fig. 20.19 Occlusal photographs. A pper arch with thermal iTi . sectional. B pper arch with aligner covering thermal iTi . sectional.  Lower arch with thermal iTi . sectional.  Occlusal photograph of lower arch with aligner covering thermal iTi . sectional.

coosite buttons. n oter words, tis ybrid aroac enabled us to iroe bot redictability and treatent tie ig. 2.2.

Extrusion, Intrusion, and Overbite Control According to Kraitz,14 etrusion and intrusion are aong te least redictable oeents acieable wit clear aligners only 29. etrusion and 41. intrusion o te oeents lanned in te setu are acieed at te end o aligner treatent. oe autors ae deonstrated tat it is ossible to aciee anterior bite closure using clear aligners,14 but in te aority o cases tis will inole uncontrolled lingual tiing o te uer and lower incisors, acieed ia sace creation troug P and transerse aillary eansion. e diculty in acieing ure etrusion is liely due to te oor gri o te aligners on cylindrical teet, wic ay be iroed by te alication o coosite buttons. oweer, we ae also ad soe success in oercoing tis bioecanical liitation, resoling oen bite using auiliaries eiter beore or during aligner

teray. e ae ound, or eale, wen oen bite in growing atients is due to bad abits tub-sucing and as already caused seletal alterations aillary contraction ig. 2.21, it is better to ot or an ortoedic aroac bite-bloc eander wit grille ig. 2.22 to noralize te uer aw and allow correct erution o te uer incisors ig. 2.2. en, once tese iroeents ae been acieed, aligners are te ideal solution or rening te occlusion ig. 2.24, guiding te eruting teet into teir roer ositions witin a liited tierae and wit inial unwanted eects ig. 2.25. At te oosite end o te sectru, dee bite ig. 2.2 cannot generally be resoled by eans o aligners alone, as intrusion o te uer and lower incisors is unredictable, once again resuably due to oor gri on te ancoring teet. ence, in all cases in wic it is indicated class , not ecessie estibular oeent o te lower incisors, it ay be ery useul to eloy class  elastics ig. 2.2. e eects o tese deices tat are coonly seen as undesirable lower olar etrusion and estibular oeent o te lower incisors enable rotation o te occlusal lane, areciably aiding oening o te bite, and allow correction o te sagittal relationsis ig. 2.2.

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285

Fig. 20.20 inal intraoral photographs after sevenstep aligner treatment.

Fig. 20.21 Initial intraoral photographs of young patient with ante rior open bite and maillary contraction.

286

Principles and Biomechanics of Aligner Treatment

Fig. 20.22 Bitebloc epander with anterior grille.

Fig. 20.23 rontal intraoral photograph after the rst stage of treat ment with palatal epander and grille.

Fig. 20.25 inal intraoral photographs after step aligner treatment.

Fig. 20.24 Intraoral photograph during aligner therapy.

olar istaliation t as been deonstrated tat aligners are able to distalize te uer olars wit a ery ig degree o ecacy rougly  wen te etent o te lanned oeent is around 2.5 .2 oweer, our clinical eerience as

sown tat bodily olar distalization is not, in act, acieable by eans o aligners, as tey roide only ery liited root control. ln 215, ang29 deonstrated, in a study o 2 atients wo underwent cone-bea couted toogray  beore and ater aligner treatent, tat irresectie o te tye o ortodontic oeent lanned, wat was acieed were large crown oeents but ery sall root oeents. is ade it clear tat te aligners were acting to tilt te teet rater tan oe te bodily. it tis in ind, in olar distalization cases ig. 2.29, it is reerable to lan derotation around te alatal root, wit distal inclination o te crown rater tan bodily oeent. Knowing tat derotation o te uer olar is not sucient to correct class , and ay cause ancorage loss, it is better to eloy class  elastics ig. 2.. e eect o tese elastics is to esially incline te teet in te lower arc, reenting te uer canines and incisors ro oing esially ig. 2.1.

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287

Fig. 20.28 inal intraoral photographs after step aligner treatment. Fig. 20.26 Initial intraoral photographs of a young patient with deep bite and class II.

Fig. 20.27 Lateral intraoral photograph during aligner therapy com bined with class II elastics.

Fig. 20.29 ight initial intraoral photograph of a patient with class II subdivision and contraction of the upper aw.

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Principles and Biomechanics of Aligner Treatment

Fig. 20.30 Lateral intraoral photograph during aligner therapy com bined with class II elastics. Fig. 20.33 apid palatal epansion and pendulum with seletal an chorage APA method.

Fig. 20.31 ight lateral intraoral photograph lateral after aligner treatment.

A

B Fig. 20.32 Left initial intraoral photograph of a patient with class II subdivision and contraction of the upper aw.

at being said, tere are cases in wic te class  is so seere tat olar distalization alone is not sucient to resole sagittal issues. n tis atient ig. 2.2, or eale, it would be unrealistic to eect to aciee - distalization ia bodily oeent wit aligners. ence we decided to eand te uer aw using a raid alatal eander ancored to our iniscrews, ositioned using te

Fig. 20.34 Lateral intraoral photographs during aligner therapy A and combined with class II elastics B.

APA etod,1- in cobination wit a onolateral endulu ig. 2.. is aroac enabled us to resole rst te transersal issues and ten te sagittal, uicly, unobtrusiely, and witout te need or atient coliance. nce class  ad been acieed, a series o 14 aligners was lanned to close te saces in te uer arc and coordinate te arces ig. 2.4. n tis case, te alication o aligners in cobination wit class  elastics on te rigt

20 • Overcoming the Limitations of Aligner Orthodontics: A ybrid Approach

Fig. 20.35 Left lateral intraoral photograph after aligner therapy.

side to roote distalization o te uer reolars and canines enabled us to treat te alocclusion wit satisactory results oer a sort eriod o tie ig. 2.5.

Conclusions e scientic and clinical eidence now sows tat aligners are able to resole alocclusion in a growing nuber o cases. n te oter and, teir liitations in ters o acieing transerse eansion ia bodily oeent as been aly docuented. t also aears tat tey are unable to redictably derotate canines and reolars. at is ore, liitations ae been described or etrusion and intrusion oeents and control o oerbite and occlusal contacts. n te basis o tese ndings, and te nowledge tat te solution to tese robles cannot be an endless series o aligners, we roose a ybrid aroac cobining aligner teray wit dierent ortodontic deices to roide satisactory and redictable clinical outcoes.

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Index age numbers folloe by “f” inicate gures an “t” inicate tables

A Afferent bers, 253 Aging, of polymers, 30 Align appliance, 125–126, 125f, 126f Aligner auxiliaries, 43–47 attacments an pressure areas, 43–45, 44f interproximal reuction, 45–46 intraoral elastics, 45 temporary ancorage eices, 47 iscoloration, 36 extrusion, 1–1, 1f, 1f plastics, 17 Aligner material properties clinical loaing patterns, 40–41, 40f longterm loaing, 37–40, 3f, 40f mecanical properties, 35 optical canges, 36, 36f optical material canges, 35 sortterm mecanical loaing multiple cycle, 37, 3f occlusal forces, 37 single, 36–37, 37f ater absorption, 35, 36f Aligner ortoontics ancorage, 47 application, 13 attacments, 13 basic attacment congurations anterior extrusion, 1–1, 1f, 1f rstorer control, 1–21, 20f, 21f posterior intrusion, 1, 1f seconorer control, 21–23, 21f, 22f, 23f, 24f tirorer control, 24–26, 24f, 25f, 26f, 27f, 2f ertical control, 17 biologic consierations, 4–4 biomaterials, 13 functions eliering preetermine force ectors, 17, 17f, 1f proiing aligner retention, 16, 16f slipping aoi, 16, 17f geometry, 13, 15f ybri approac canine an premolar rotation, 277–24, 21f, 22f, 23f, 24f, 25f extrusion, intrusion, an oerbite control, 24, 25f, 26f, 27f molar istaliation, 26–2, 27f, 2f, 2f transerse expansion, 275–277, 276f, 277f, 27f, 27f, 20f, 21f improements, 13 location, 14–15, 15f, 16f in prerestoratie patients, 16–1 seuentialiation, 47 sie, 15 translucent composites, 13 Aligner planning softare, 11–14 Aligner “slipping,” 16, 17f Alignertoot mismatc, 13, 14f American ental Association ouncil on cientic Affairs A, 6 Ancorage management, 47

290

Anterior open bite biomecanics, for correction, 5 iagnosis, 5 treatment alternaties, , 104 attacments, 6–7, 6f, 7f linec softare esign, 5–6 obecties, , 100t, 104, 105t plan, , 104, 105f results, 100–102, 101f, 102f, 102t, 105, 106f, 107f, 10f, 10t seuence, –100, 100f, 105, 106f Arc eelopment, class  malocclusions treatment plan, 51

B eneslier, clinical proceure an rational of, 10–11, 11f icuspis, it plastic aligners, 1 iomaterials, for attacment fabrication, 13 iomecanical conentional attacment, class  malocclusions treatment plan, 51, 52f olton analysis, 53 racetbase biomecanics, 21 uccal tipping, 25, 25f

C alcitonin generelate peptie , 252–253 anine impaction aerse seuelae of, 14 clinical case, 157–15, 15f, 15f, 162f, 163f, 164f, 165f, 166f early iagnosis an treatment, 14–153, 152f, 153f late iagnosis, 153–154, 154t patologic conition, 14 prealence, 14 treatment, 14–153, 152f, 153f planning, 154–157, 154f, 155f, 156f arriere otion 3 Appliance A, 137, 13 A See lear aligner terapy A  See onebeam compute tomograpy  epalometric analysis, 3, 7, f erical ertebral maturation , 121 emical aging, of polymers, 30, 32–33 lass  elastics, 10 lass  malocclusions, 123–126, 125f, 126f clinical protocol, 67–6 elastic effect, 67 extractions, 67 ybri approac in case report, 13–13, 13f, 140f, 141f, 142f, 143–146, 143f, 144f, 145f, 146f, 147f it istaliing eice, 137–13 manibular aancement, 67 maxillary istaliation, 6–7, 6f, 70f, 72f, 73f, 74f, 75f, 76f, 77f, 7f, 0f maxillary molar istaliation, 66–67 maxillary molar rotation, 67 ortognatic surgery, 67 terapeutic options, 66

lass  malocclusions, 51 entoaleolar iscrepancy, 52, 52f, 53f, 54f iagnosis, 51 morpologic iscrepancy, 5–60, 61f, 62f, 63f preprostetic nee, 60–62, 64f toot sie iscrepancy, 53–56, 55f transerse iscrepancy, 56–5, 56f, 57f, 5f, 5f treatment, 51–52 lear aligner terapy A, 137, 252 case stuy, 240–244, 241f, 242f, 243–244f, 245f, 246f, 247f, 24f, 24f, 250f complex moements, 42 funamentals recap, 4 it nisalign, 235 patient compliance, 4 surgery rst, 237–240 teoretical an practical consierations, 43–4 analysis of moements occurring, 43–4 nal position analysis, 43, 43f transitioning, 237, 23–23f, 23f, 23f, 240f it irtual setup softare, 210 lear aligner treatment A class  malocclusions, 66 of croing, 52 linec softare, 6–6, 3 esign, 5–6 tools, 52f treatment plan, 1f omplementary force ectors, 17, 17f omputerassiste esigncomputerassiste manufacturing AA, 1 onebeam compute tomograpy , 1, 2f, 153 aantages, 5 AAA, 5 AAA concept, 5 benets, 6–7, 6f, 7f, f, f, 10f cepalometrics, 5 it conentional panoramic examinations, 6 loose raiograpic proceures, 5–6 ortoontic iagnosis an treatment planning, 5 ortognatic surgery, 7 upper airay, 7 onentional attacments, of aligner auxiliaries, 44, 44f onentional bracet tecniues ortoontic toot moement it, 13, 14f torue moication of, 24, 24f reep, 17, 33, 37 ure of pee, 10–110, 110f

D eep bite case report, 111–114, 111f, 112f, 113f, 114f, 115f, 116f, 117f, 11f, 11f, 120f correlation beteen, 10 cure of pee leel, 10–110, 110f enition, 10 treatment strategies, 10 upper incisors leel, 110–111

Index

ental arces, 3 entoaleolar iscrepancy, 52, 52f, 53f, 54f entofacial ortopeics, 1 ifferential scanning calorimetry , 32 igital maging an ommunications in eicine , 7 igital imaging tecniues, 11, 11f igital impressions, 3 igital moels, 1–5, 3f igital smile esign , 16 istaliation, 67 ouble conentional attacment, 54f uplex, 56

abial impactions, 157 aser scanning, 7– eone appliance, 125, 125f oss of tracing, 17

M

lastic aligner eformation, 13, 14f lastic effect, of class  malocclusions, 67 lastic ear, 67 namel, 3–5 stetic analysis, 16 tanol, 31–32 olution, 1 xtraction iagnosis, 3, 4f, 5f, 6f of posterior teet, 5 treatment plan, 3 progress, 3–7, 7f, f, f, 0f results, 7–1, 1f, 2f, 3f

alocclusion, 1 anibular aancement, 126–132, 127f, 12f, 130f, 132f, 133f, 134f pase, 126 anibular xation, 236–237 axillary istaliation, 6–7, 6f, 70f, 72f, 73f, 74f, 75f, 76f, 77f, 7f, 0f axillary expansion , 121–122, 122f axillary molar istaliation, 66–67 axillary molar rotation, 67 axillary transerse eciency, 6 esioistal moements, 210 iniimplants, 10 olar istaliation aligner ortoontics, in ybri approac, 26–2, 27f, 2f, 2f upper in aligner treatment, 10 clinical case, 11–200, 12f, 13t, 14f, 15f, 16f, 17f, 1f, 200f clinical consierations, 200 olars, it plastic aligners, 1 ucogingial unction , 157

F

N

abrication process, 32 acial treeimensional scan, 2f eer aligners, 67 inite element analysis A, 15, 20–21 inite element meto , 44–45 ree gingial graft , 205–207 urcation efects, 207–20

ational ommission on aiation rotection an easurements, 5 ear infrare  tecnology, 3–5, 4–5f

E

G ingial creicular ui  biomarers, 125 lass transition temperature, 32 lassy material, 31–32

H an an rist maturation , 121 orsesoesape geometry, 25–26 ygroscopic expansion, 35

I ncisor control, class  malocclusions treatment plan, 51 nsufcient force leels, 25–26, 26f, 27f, 2f nterceptie ortoontics, 121 case reports, 122–123, 123f, 124f, 124t maxillary expansion, 121–122, 122f ntermaxillary elastics, 16 nterproximal contacts, 11 nterproximal enamel reuction , 45–46 nterproximal reuction, class  malocclusions treatment plan, 51–52 ntraoral scans s, 1–5, 3f nisalign aligners, 13–13 nisalign system, 3

L abial xe ortoontic appliances, 236–237, 236f

O penbite treatment alternaties, , 104 attacments, 6–7, 6f, 7f linec softare esign, 5–6 for correction, biomecanics, 5 obecties, , 100t, 104, 105t plan, , 104, 105f results, 100–102, 101f, 102f, 102t, 105, 106f, 107f, 10f, 10t seuence, –100, 100f, 105, 106f ptimie attacments, of aligner auxiliaries, 44, 44f ptimie oot ontrol Attacments, 22 rtoontic applications, in polymers, 30 rtoontic pain biologic mecanisms of, 252–253 in clear aligner terapy, 253–254 clinical consierations, 255–256, 256t clinical correlates, 252–253 importance of, 252 psycological factors, 254–255 rtoontics, 1 aances in, 16 aligner, 1 iagnosis, 1, 2f igital eolution in, 1 2 imaging moalities, 5–6 rtoontic toot moement , 42 staging, 47–4 rtoontic treatment See etention rtoontists, 42 rtognatic surgery, 7, 67, 235 rtopantomograpy , 116f, 120f, 14, 152f rtoulse, 1–3 ererupte molars, 17

291

P ain, 252 alatal impactions, 157 alatally isplace maxillary canine  teet, 14 anoramic xray, 147f atologic toot migration , 202 enulum  appliance, 13 erioontal isease clinical case, 214–220, 215f, 216f, 217f, 21f, 21f, 221f, 222f, 223f, 224f, 225f, 226f, 227f, 22f, 22f, 230f, 231f iagnosis, 205–210 malocclusions relate to, 202, 203f optimal control, 210–214 ocart, 214 mesioistal moements, 210, 212f ertical moements, 213–214, 213f estibulolingual moements, 213 ortoontic moements, 210–214, 212f ortoontic treatment in, 202, 204f retention, 214 treatment planning multiisciplinary team, 205 ortoontic assessment, 20, 20t, 20f, 211f, 212f patient expectations, 205, 205f perioontal assessment, 205–20, 205t, 206f, 206t erioontal ligament  strain, 22, 22f erioontitis graes, 205t, 220t stages, 206t, 21t  See olyetylene tereptalate glycol  ysical aging, of polymers, 30, 32–33 lastic foil, 210 lastic materials, 42 olyetylene tereptalate glycol , 31, 35 material, cemical structure of, 31f olymers cemical aging, 30, 32–33 enition, 30 materials, 30 mecanical stability, 30 molecular structure, 30–32, 31f in ortoontic applications, 30 pysical aging, 30, 32–33 termal properties, 30–32 olyuretane , 31 material, cemical structure of, 31f re–manibular aancement pase, 126  See olyuretane 

R api maxillary expansion , 121, 122 etention appliances, 266, 266f, 267f, 26f, 26f in ortoontic treatment, 25–260 protocol, 260–261f, 260–264, 262f, 263f, 264–265f, 265f, 270–272 specics, 266–270, 270f, 271f, 272f, 273f eolution, 1 otation control, class  malocclusions treatment plan, 51 unner, 125, 125f

S euentialiation, 47 eere entofacial eformity, 235

292

Index

lo maxillary expansion , 122 oft tissue ata extraction, 7– pace management in anterior region, 16–16 case stuy, 16–170, 16f, 170f, 171f, 172f, 173f in posterior region, 170–174, 175f, 176f, 177f, 17f pecic olume, 31 plintaie maxillary, 236–237 tability, 25–260 tereopotogrammetry, 7– tress relaxation, 17, 37–3, 40f ubepitelial connectie tissue graft , 205–207 upercoole region, 31–32 urgery rst, it aligner terapy, 235–251

T angential forces, 16, 17f eet segmentation,  emporary ancorage eices As, 47, 5, 157 emporomanibular isorers s case stuy, 10–14, 10f, 11f, 12f, 13f, 14f, 15f, 16f, 17f, 1f iagnosis, 17–10 management, 17 treatment plan, 17–10

emporomanibular oint , 7 ensile measurements, 37–3 ermoplastic aligner materials, 40 ermoplastic polymers, 31 ermoplastic polyuretane , 35 oontics See Aligner ortoontics 3 ata integration, 11, 11f 3 facial reconstruction tecniues, 7–, 10f 3 imaging conebeam compute tomograpy, 5–6 benets, 6–7, 6f, 7f, f, f, 10f 3 ata integration, 11, 11f 3 facial reconstruction tecniues, 7–, 10f irtual setup, –11, 11f s See emporomanibular isorers s oot alignment after aligner seuence, 13, 14f an leeling, 11 oot isplacement patterns, of posterior teet, 22, 22f oot sie iscrepancy, 53–56, 55f oottootgingia segmentation,  orue moication, of anterior teet, 24 racing superimposition, 116f ransition pase, 126 ranserse eciency correction of, 24 maxillary, 6

ranserse iscrepancy, 56–5, 56f, 57f, 5f, 5f umor necrosis factora a, 252–253

U pper molar istaliation See also olar istaliation in aligner treatment, 10 clinical case, 11–200, 12f, 13t, 14f, 15f, 16f, 17f, 1f, 200f clinical consierations, 200 prigting moment, of posterior teet, 22f

V ertical moements, 213–214 estibulolingual moements, 213 iscoelasticity, 31–32 iscoelastic material, mecanical beaior of, 37

W ater absorption, of aligner material properties, 35, 36f it of eratinie gingia , 20

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