Effect of miniscrew placement height on the distribution of biological forces produced by clear aligner for mandibular molar distalization / 口腔疾病防治

Objective@#To explore the effect of different miniscrew placement heights on the distribution of biological forces produced by clear aligner combined with intramaxillary traction for mandibular molar distalization, to identify the miniscrew location that is conducive to the protection of lower anterior tooth anchorage and to provide a reference that can be used when designing clinical treatments.@*Methods@#Mimics, GeomagicStudio 2017, SolidWorks 2016, and Ansys workbench were used to establish finite element analysis models and perform mechanical analysis under the following six working conditions: working condition 1 was the control group without miniscrews; working conditions 2 to 5 had miniscrew in the buccal bone cortex between the first and second molars of the lower jaw 10 mm, 7 mm, 4 mm, and 1 mm from the top of the alveolar crest, respectively; working condition 6 had the miniscrew in the center of the buccal tongue at the anterior edge of the ascending branch of the lower jaw 5 mm above the occlusal plane.@*Results@#On the sagittal axis, miniscrew anchorage caused distal displacement of all teeth. Compared to the control group, in the miniscrew group, the displacement of the anterior molars exceeded that of the second molars. On the vertical axis, the result in the control group was similar to backward bending; the results in the miniscrew groups resembled the effect of a lever, lowering the lateral incisors and canines and raising the central incisors and first premolars. On the coronal axis, the second premolars and the first molars showed lingual displacement in the control group, and only the premolars and first molars showed lingual displacementin the miniscrew groups. The canines were the teeth that were most strongly affected by the change in miniscrew placement height.@*Conclusion@#The higher the miniscrew position is, the stronger the protective effect on the anterior anchorage. According to the miniscrew placement height, the mandibular arch should be properly narrowed, the central incisors and first premolars should be lowered, and the lateral incisors and canines should be raised when designing clinical treatments.

Three-dimensional finite element study of mandibular first molar distalization with clear aligner / 华西口腔医学杂志

OBJECTIVES@#This study aimed to construct the finite element model of the mandibular first molar with the invisible appliance and explore the dentition movement characteristics of the mandibular first molar when using micro-implant anchorage and different initial positions of the first molar.@*METHODS@#Models of the mandible, tooth, periodontal membrane, and invisible appliance were constructed using cone beam computed tomography (CBCT) data. The two groups were divided into the non-anchorage group and the micro-implant group (between the roots of the first molar and the second molar) based on whether the elastic traction of the micro-implant was assisted or not. The two groups were divided into the following conditions based on the starting position of the first molar: Working condition 1: the distance between the first molar and the second premolar was 0 mm; working condition 2: the distance between the first molar and the second premolar was 1 mm; working condition 3: the distance between the first molar and the second premolar was 2 mm; working condition 4: the distance between the first molar and the second premolar was 3 mm. The data characte-ristics of total displacement and displacement in each direction of dentition were analyzed.@*RESULTS@#In the non-ancho-rage group, all the other teeth showed reverse movement except for the first molar which was moved distally. Meanwhile, in the micro-implant group, except for a small amount of mesial movement of the second molar in wor-king condition 1, the whole dentition in other working conditions presented distal movement and anterior teeth showed lingual movement, among which the distal displacement of the first molar in working condition 4 was the largest. With the change of the initial position of the first molar to the distal, the movement of the first molar to the distal, the premolar to the mesial, and the anterior to the lip increased, while the movement of the second molar to the mesial decreased.@*CONCLUSIONS@#The micro-implant can effectively protect the anterior anchorage, increase the expression rate of molar distancing, and avoid the round-trip movement of the second molar. The initial position of the first molar movement is related to the amount of distancing and the remaining tooth movement.

Achieved intrusion amount of the maxillary incisors and the influencing factors in clear aligner extraction cases / 口腔疾病防治

Objective @#To investigate the achieved intrusion amount of the maxillary incisors and the influencing factors in clear aligner cases treated with extraction of premolars. @*Methods @#This study has been reviewed and approved by the Ethics Committee, and informed consent has been obtained from patients. Thirty adult female patients who underwent extraction of the bilateral maxillary first premolars followed by clear aligner therapy were included. CBCT data before and after treatment were obtained, and three-dimensional reconstruction with registration alignment was performed. A spatial coordinate system was established, and the achieved intrusion amount was measured, followed by calculation of the intrusion efficacy. The factors related to the achieved intrusion amount were investigated through multiple linear regression analysis.@*Results @#The overall efficacy of maxillary incisor intrusion was 54%, with the maxillary central incisors (48%) lower than the lateral incisors (59%), which was statistically significant (P<0.001). Regression analysis showed that the designed intrusion amount and the stepwise intrusion design were positively correlated with the achieved intrusion amount. The designed retroclination amount and use of class Ⅱ intermaxillary elastics were negatively correlated with the achieved intrusion amount. The initial overbite, overjet, crowding, upper central incisor inclination, amount of the first series of aligners, canine attachment type, posterior teeth attachment type and bite ramps had no significant correlation with the achieved intrusion amount.@*Conclusion@# In maxillary first premolar extraction cases treated with clear aligners, the upper central incisors have lower efficacy of intrusion movement than the lateral incisors. The achieved intrusion amount of maxillary incisors was influenced by multiple factors, which should be considered comprehensively for better vertical control in such cases.

Factors influencing mechanical properties of clear aligners and research progress / 口腔医学

@#In recent years, clear aligner technology has been maturing and is rapidly gaining popularity in the orthodontic market for its aesthetic and removable properties. However, despite the background of its large-scale clinical application, mechanical properties of clear aligners need to be studied in depth. This paper reviews the factors influencing mechanical properties of clear aligners and the current status of research to provide evidence-based guidance for clinical application.

Study on clinical efficacy of a 3D model based on crown-root integration in clear aligners / 口腔医学

Objective@#To evaluate the clinical effect of clear aligners in the anterior region in non-extraction cases by establishing a three-dimensional model of crown-root fusion to guide clinical application.@*Methods@#Eleven patients visiting the orthodontic department of Xuzhou Stomatological Hospital from December 2020 to December 2021 were collected, and the orthodontic plan was designed using Maestro 3D Dental Studio scheduling software to obtain the expected three-dimensional model of the patient's orthodontic treatment result. CBCT, intraoral scan, and 3D reconstruction software were used to create a postoperative model of the patient. The crown and root data were aligned in Geomagic Studio 2014, and differences in torque and axial inclination between the actual model after treatment and the predicted model of the anterior teeth before treatment were compared in 3-matic.@*Results@#The actual torque angles of the anterior teeth were all smaller than the predicted angles before treatment, with the highest realization rate of 77.55% for lateral incisors and the lowest of 60.70% for central incisors; the actual axial inclination angles of the anterior teeth were also smaller than the predicted angles before treatment, with the highest realization rate of 81.49% for central incisors and the lowest of 74.95% for cuspids. @*Conclusion@# A digital model of crown-root integration based on a combination of 3D reconstruction and intraoral scanning techniques is advantageous in assessing the efficacy of clear aligners. In non-extraction cases with clear aligner, the efficiency of movement is higher for small areas of the anterior region.

Effect of different tips of posteriors in extraction treatment on three-dimensional forces of teeth with clear aligners / 口腔医学

Objective@#To investigate the three-dimensional forces in real-time at different tips of the posteriors created by clear aligners on maxillary teeth during en-masse retraction of anteriors after 2 first premolars extraction treatment. @*Methods@#Four groups of maxillary models with different tips of posteriors(T1-upright of posteriors, T2-posteriors with distal inclination of 5°, T3-posteriors with mesial inclination of 5°, T4-posteriors with mesial inclination of 10°) undergoing 0.25 mm en-masse retraction treatment using clear aligners were simulated on a multi-axis force/torque transducer measurement system. When each clear aligner was inserted, a computer connected to the transducer collected and recorded the three-dimensional force of every tooth in real-time. Each group included 12 aligners.@*Results@#Incisors received smaller lingual and extrusive forces; canines received greater distal forces; smaller mesial forces were observed on the posteriors, and molars received greater buccal and extrusive forces in T2,compared with T1,which showed statistically significant differences(P<0.05). Incisors received smaller lingual and extrusive forces; canines received greater distal forces; greater mesial forces were observed on the posteriors, and molars received greater buccal and extrusive forces in T3 and T4,compared with T1,which showed statistically significant differences(P<0.05).@*Conclusion@#Posteriors with distal inclination contributed to the torque of the anterior and anchorage of posteriors. In group T2 posterior teeth experienced larger buccal forces and extrusive forces than in group T1. When the posteriors crown inclined mesially, the anterior teeth were more prone to lingual tip and caused overbite. The more mesially inclined the posterior teeth were, the more serious overbite was, and the posterior teeth were more prone to anchorage loss.

Assessing the reliability of ChatGPT: a content analysis of self-generated and self-answered questions on clear aligners, TADs and digital imaging

ABSTRACT Introduction: Artificial Intelligence (AI) is a tool that is already part of our reality, and this is an opportunity to understand how it can be useful in interacting with patients and providing valuable information about orthodontics. Objective: This study evaluated the accuracy of ChatGPT in providing accurate and quality information to answer questions on Clear aligners, Temporary anchorage devices and Digital imaging in orthodontics. Methods: forty-five questions and answers were generated by the ChatGPT 4.0, and analyzed separately by five orthodontists. The evaluators independently rated the quality of information provided on a Likert scale, in which higher scores indicated greater quality of information (1 = very poor; 2 = poor; 3 = acceptable; 4 = good; 5 = very good). The Kruskal-Wallis H test (p< 0.05) and post-hoc pairwise comparisons with the Bonferroni correction were performed. Results: From the 225 evaluations of the five different evaluators, 11 (4.9%) were considered as very poor, 4 (1.8%) as poor, and 15 (6.7%) as acceptable. The majority were considered as good [34 (15,1%)] and very good [161 (71.6%)]. Regarding evaluators' scores, a slight agreement was perceived, with Fleiss's Kappa equal to 0.004. Conclusions: ChatGPT has proven effective in providing quality answers related to clear aligners, temporary anchorage devices, and digital imaging within the context of interest of orthodontics.

RESUMO Introdução: A Inteligência Artificial (IA) é uma ferramenta que já faz parte de nossa realidade, e esta é uma oportunidade de entendermos como ela pode ser útil na interação com os pacientes e no fornecimento de informações valiosas sobre Ortodontia. Objetivo: O objetivo deste estudo foi avaliar a precisão do ChatGPT em responder a perguntas sobre Alinhadores transparentes, Dispositivos de ancoragem temporária, e Imagens digitais em Ortodontia. Métodos: 45 perguntas e respostas foram geradas pelo ChatGPT 4.0 e analisadas separadamente por cinco ortodontistas que, de forma independente, avaliaram a qualidade das informações fornecidas, usando uma escala de Likert, na qual pontuações mais altas indicavam uma maior qualidade das informações (1 = muito ruim; 2 = ruim; 3 = aceitável; 4 = bom; 5 = muito bom). Aplicou-se o teste H de Kruskal-Wallis (p < 0,05) e comparações pareadas post-hoc com correção de Bonferroni. Resultados: Das 225 avaliações dos cinco avaliadores diferentes, 11 (4,9%) foram consideradas como muito ruins, 4 (1,8%) como ruins, e 15 (6,7%) como aceitáveis. A maioria foi considerada boa [34 (15,1%)] ou muito boa [161 (71,6%)]. Com relação às pontuações dos avaliadores, percebeu-se uma leve concordância, com o Kappa de Fleiss igual a 0,004. Conclusões: O ChatGPT mostrou eficácia em fornecer respostas de qualidade para questões relacionadas a Alinhadores transparentes, Dispositivos de ancoragem temporária e Imagens digitais.

Edge level of aligners and periodontal health: a clinical perspective study in young patients

ABSTRACT Introduction: Although the superiority of clear aligners over multi-bracket appliances in keeping gingiva healthy has been suggested, the possible benefits of one aligner design over another have not yet been investigated, especially with regard to the vestibular edge. Objective: The aim of this study was to measure several periodontal indexes in adolescents undergoing orthodontic treatment with aligners, comparing two different types of rim. Methods: The study involved 43 patients aged between 14 and 18 years. The periodontal health was assessed using plaque index (PI), gingival index (GI), and gingival bleeding index (GBI), at the start of the treatment with aligners (T0), with a vestibular rim (VR) reaching up to 3 mm beyond the gingival margin. Three months later (T1), aligners were set to obtain a juxtagingival rim (JR) on the second quadrant and VR on the first quadrant. The periodontal indexes were measured again, both at T1 and then three months later (T2). Results: Intra-quadrant comparisons revealed a statistically significant worsening of the periodontal indexes only for the second quadrant (p<0.05), at T1 (GI), and especially at T2 (PI, GI, GBI), while no statistically significant changes were found for the first quadrant. Conclusions: More severe mechanical irritation, especially during insertion and removal of the aligner, can explain the worsening inflammatory indexes with the JR. In addition, the pressure exerted by the JR on the gingival sulcus seemed to facilitate plaque deposition, whereas the VR had a protective effect, reducing the risk of mechanical trauma.

RESUMO Introdução: Embora se alegue uma superioridade dos alinhadores transparentes sobre os aparelhos multibraquetes em manter a gengiva saudável, ainda não foram investigados os possíveis benefícios de um modelo de alinhador sobre outro, especialmente no que diz respeito à borda vestibular. Objetivo: O objetivo deste estudo foi medir vários índices periodontais em adolescentes submetidos a tratamento ortodôntico com alinhadores, comparando dois tipos diferentes de borda. Métodos: O estudo envolveu 43 pacientes com idade entre 14 e 18 anos. A saúde periodontal foi avaliada por meio do índice de placa (IP), índice gengival (IG) e índice de sangramento gengival (ISG), ao início do tratamento com alinhadores (T0), com borda vestibular (BV) estendendo-se até 3 mm além da margem gengival. Três meses depois (T1), os alinhadores foram ajustados para se obter uma borda justagengival (BJ) no segundo quadrante e BV no primeiro quadrante. Os índices periodontais foram medidos novamente tanto em T1 quanto três meses depois (T2). Resultados: As comparações intraquadrantes revelaram uma piora estatisticamente significativa nos índices periodontais apenas para o segundo quadrante (p<0,05), em T1 (IG) e especialmente em T2 (IP, IG, ISG), enquanto nenhuma mudança estatisticamente significativa foi encontrada para o primeiro quadrante. Conclusões: Irritações mecânicas mais intensas, principalmente durante a inserção e remoção do alinhador, podem explicar a piora dos índices inflamatórios com a BJ. Além disso, a pressão exercida pela BJ no sulco gengival pareceu facilitar a deposição de placa, enquanto a BV teve um efeito protetor, reduzindo o risco de trauma mecânico.

Perceived esthetics and value of clear aligner therapy systems: A survey among dental school instructors and undergraduate students

ABSTRACT Objective: To investigate the attractiveness, acceptability, visibility and willingness-to-pay for clear aligner therapy (CAT) systems in first-year and final-year dental students and instructors. Methods: A questionnaire designed to collect information regarding esthetic preferences and intentions related to seven CAT systems was handed out to 120 undergraduate students and instructors at the Academic Centre for Dentistry Amsterdam (ACTA). Proportional odds models and population average generalized estimating equation models were used to examine potential association between participant characteristics, esthetic perceptions and CAT systems. Results: Overall, the examined CAT systems received favorable esthetic ratings. Expertise status was significantly associated with willingness-to-pay additionally for CAT, compared to fixed orthodontic appliances. There was no association between sex, previous orthodontic treatment history, satisfaction with own dental appearance and potential interest in treatment and aligner visibility and willingness-to-pay. CAT system was significantly associated with the perceived aligner visibility, acceptability and attractiveness by students and instructors. Conclusions: CAT systems were considered to a great extent attractive and acceptable for future treatment by dental school instructors and students. Willingness-to-pay for CAT systems was significantly associated with expertise status, with instructors appearing more reluctant to pay for CAT.

RESUMO Objetivo: Comparar diferentes sistemas de tratamento com alinhadores transparentes (CAT), quanto à atratividade, aceitabilidade, visibilidade e disposição a pagar, por parte de alunos (primeiro e último anos) e instrutores de Odontologia. Métodos: Um questionário elaborado para coletar informações sobre preferências e intenções estéticas, em relação a sete sistemas CAT, foi distribuído para 120 alunos de graduação e instrutores do Academic Centre for Dentistry Amsterdam (ACTA). Modelos de riscos proporcionais e modelos de equação de estimação generalizada para a média da população foram usados para examinar a possível associação entre as características dos participantes, percepções estéticas e os sistemas CAT. Resultados: No geral, os sistemas CAT examinados receberam avaliações estéticas favoráveis. O nível de experiência foi significativamente associado com a disposição em pagar mais por sistemas CAT do que por aparelhos ortodônticos fixos. Não houve associação entre sexo, histórico de tratamento ortodôntico anterior, satisfação com a própria aparência dentária, potencial interesse em tratamento, visibilidade do alinhador e disposição em pagar mais. Os sistemas CAT foram significativamente associados à visibilidade percebida, aceitabilidade e atratividade dos alinhadores por alunos e instrutores. Conclusões: Os sistemas CAT foram considerados, em grande parte, atraentes e aceitáveis para tratamentos futuros pelos instrutores e alunos do curso de Odontologia. A disposição em pagar mais pelos sistemas CAT foi significativamente associada ao nível de especialização, com os instrutores parecendo mais relutantes em pagar mais pelo CAT.

Research progress on the three-dimensional finite element analysis of bite opening / 口腔疾病防治

@#Deep bite is a common clinical malocclusion that has a great impact on patients’ facial aesthetics and oral function. Bite opening is the key step in the treatment of deep bite, playing a decisive role in the development of mandible and the progress of orthodontic treatment. Torque and tip control during the correction of deep bites is a hot topic in orthodontics. The three-dimensional finite element method can accurately simulate clinical processes and conduct dynamic stress analysis, which provides the basis of the biomechanical mechanism. This paper reviewed the finite element analysis of various orthodontic systems for bite opening to provide a reference for clinical application. The emergence of mini-implants provided a new idea for anchorage control in bite opening. Finite element studies found that high-positioned mini-implants are beneficial for bodily tooth intrusion and proposed the ideal position for force application. For the finite element simulation of the reverse curve archwire, it was found that the intrusion and inclination of the anterior teeth increased with the curve depth of the archwire. The application of clear aligners has also been flourishing, but these forces are still difficult to effectively control. Finite element studies on their attachment design and corresponding tooth movement may be helpful to open the bite quickly and effectively. However, the existing studies still have modeling limitations. The structural simplification, linearization and nonstandard parameter definition of the model reduce model accuracy. Additionally, the existing research mostly focused on initial tooth movement, and studies on long-term tooth movement after bone remodeling are lacking. These studies are needed in the future.

Research progress on the relationship between orthodontic treatment and the oral microbiome / 口腔疾病防治

@#With the deepening of research in oral microbiomics, an important relationship between changes in the oral microbiome and orthodontic treatment has been found. Orthodontic treatment will have an impact on the oral and systemic microbiome. The presence of oral appliances can change the quantity and quality of the oral microbiometo and increase the risk of oral and even systemic diseases in patients undergoing orthodontic treatment. Compared with fixed orthodontic treatment, clear aligners will not have a harmful impact on the structure of the oral microbiome, which is more conducive to maintain oral health during the orthodontic treatment process. In addition, different bracket types and materials can lead to different changes in the oral microbiome, and the occurrence and development of orthodontic-related diseases, such as white spot lesions, dental caries, gingivitis and periodontitis, are also related to changes in the oral microbiome. At present, the role of the oral microbiome in the process of orthodontic treatment needs to be further studied. Whether a change in the oral microbiome caused by orthodontic treatment can be restored after orthodontic treatment is still uncertain and needs more research. This paper reviews the research progress on the application of microbiomics in orthodontics, including the impact of fixed appliances and clear aligners on the microbiome and the relationship between orthodontic-related diseases and the oral microbiome.

Effects of Attachment Wear on Tooth Movement: A Finite Element Analysis / 医用生物力学

Objective To explore the effect of attachment wear on tooth movement in clear Aligner treatment, and to provide references for improving the efficiency of orthodontic treatment. Methods The tooth cone bean computed tomography (CBCT) scanning data were obtained, and the tooth model was established and assembled with the worn and complete attachment, respectively. When the appliance applied 2° distal torsion, 0.25 mm distal displacement, 0.1 mm depression displacement and 0.1 mm elongation displacement to the teeth, the changes of tooth displacement, periodontal ligament stress and root equivalent stress in the worn and complete attachment groups were compared. Results When the clear Aligner was used to apply distal torsion and elongation displacement to the teeth, the maximum tooth displacement decreased significantly, and the worn attachment caused the teeth to move obliquely when the distal translation and elongation displacement occurred. When the tooth was subjected to distal torsion, distal translation, depression and elongation, the maximum principal stress of periodontal ligament and the equivalent stress of tooth root decreased when the worn attachment caused the tooth to be subjected to distal torsion, distal translation, depression and elongation. Conclusions Attachment wear will affect the efficiency of tooth rotation and elongation.When the attachments are obviously worn, they should be replaced in time to ensure normal function of the attachments.

Alinhadores Ortodônticos Removíveis Versus Aparelhos Ortodônticos Fixos: uma Revisão da Literatura / Removable Orthodontic Aligners Versus Fixed Orthodontic Appliances: a Literarture Review

Com intuito de pontuar os paralelos entre as técnicas ortodônticas com aparelhagem fixa e alinhadores transparentes, este estudo propôs revisar a literatura científica sobre alinhadores ortodônticos removíveis versus aparelhos ortodônticos fixos. Foram selecionados artigos de 2005 a 2021, utilizando as bases de dados PubMed, Scopus, Web of Science, Cochrane Library, Clinical Trials e Opengrey. Os artigos abordavam temáticas como sensação dolorosa, saúde periodontal, higiene, microbiota, reabsorção radicular, qualidade de vida e efetividade do tratamento. Os alinhadores apresentaram maior aceitabilidade pelos pacientes e vantagens claras em relação à dor, higiene, qualidade de vida, reabsorção radicular e saúde periodontal, sendo inferior aos aparelhos ortodônticos fixos na efetividade do tratamento e na interferência na fala.

In order to point out the parallels between orthodontic techniques with fixed appliances and transparent aligners, this study proposed to review the scientific literature on removable orthodontic aligners versus fixed orthodontic appliances. Articles from 2005 to 2021 were selected, using the PubMed, Scopus, Web of Science, Cochrane Library, Clinical Trials and OpenGrey databases. The articles addressed issues such as pain, periodontal health, hygiene, microbiota, root resorption, quality of life and treatment effectiveness. Aligners showed greater acceptability by patients and clear advantages in relation to pain, hygiene, quality of life, root resorption and periodontal health, being inferior to fixed orthodontic appliances in terms of effectiveness and speech capacity.

Influences of Different Root Control Attachments on Canine Distal Translation with Plastic Aligner / 医用生物力学

Objective To study the effects of different root control attachment on root control and periodontal ligament （PDL） stress during canine distal translation in plastic aligner-based orthodontic treatment. Methods Through three-dimensional (3D) finite element technology, 11 models composed of 4 attachments and 3 kinds of loading were established. Namely, attachment A: no attachments; attachment B: traditional vertical rectangular attachment; attachment C: 1/4 spherical double optimized attachment; attachment D: double optimized door arch attachment; load a: 0.15 mm distal translation of the canine; b: load a+ application of 30 N·mm counterclockwise torque to stress surface of the attachment; load c: load a+ application of 30 N·mm counterclockwise torque to the entire crown. The root control effect of distal translation of the right maxillary canine was simulated with plastic aligner under different loads. Results Displacement modes of all models were distally tipped translation. The double optimized door arch attachment showed the optimal root control effect during canine distal translation. The root control effect for two groups of double optimized attachment was better than that of traditional rectangular attachment. The effect of adding attachments on root control of the canine was better than that of applying only counterclockwise couple. The PDL stress mainly appeared in distal alveolar ridge and root apex without attachment, while the PDL stress mainly appeared in distal alveolar ridge with attachment. Conclusions The most suitable measure to improve the effect of root control during canine distal translation is to use the double optimized door arch attachment in clinic.

The Role of Power Arm by Combined Use of Clear Aligner and Miniscrew in En-Masse Retraction of Maxillary Anterior Teeth / 医用生物力学

Objective To investigate the role of Power Arm in en-masse retraction of maxillary anterior teeth using clear aligner (CA) and micro-implant anchorage (MIA). Methods The three-dimensional (3D) model of maxillary anterior teeth by combined use of CA and MIA was established, and the 6 mm-height Power Arm, was attached to the canine or appliance. The initial displacement and the maximum von Mises stress of periodontal ligament under three loading conditions were analyzed, namely the force was loaded by CA+150 g retraction force at canine, CA+150 g retraction force on Power Arm at appliance, CA+150 g retraction force on Power Arm at canine. Results In sagittal direction, the crown and root displacement difference of maxillary central incisor was 129, 129, 133 μm，respectively. The crown displacement of the maxillary first molar was -23.3, -23.5, -26.8 μm, respectively. The maximum von Mises stress of periodontal ligament in central incisor was 48.4, 72.6, 40.0 kPa, respectively, and that of the first molar was 5.3, 10.5, 5.8 kPa, respectively. Conclusions It can not be testified that retraction of the 6 mm-height Power Arm at canine or appliance with 5 mm-height mini-screw has more advantages than retraction of the canine directly for more favorably controlling the torque of incisors, saving anchorage of posterior teeth and decreasing von Mises stress of the periodontal ligament.

Efficacy of mandibular molar distalization by clear aligner treatment / 中南大学学报(医学版)

OBJECTIVES@#At present, the research on clear aligner of molar distalization mainly focuses on the upper jaw, while the research on mandibular molars is few.This study aims to evaluate the therapeutic effect of mandibular molars distalization with clear aligner via cone beam CT (CBCT) and Dolphin software.@*METHODS@#Twenty cases of mandibular molars with clear aligner were included according to the inclusion and exclusion criteria. CBCT was taken before treatment (T0) and when the first molar was moved in place (T1). Dolphin software was used to measure the effectiveness of molar distalization. Three-dimensional changes in direction and the impact on the incisors and facial soft and hard tissues were evaluated.@*RESULTS@#The effective rates of crown and root distalization of the second and first mandibular molars were 74%, 49%, and 71%, 47%, respectively. The second and first molars were both the distal buccal cusp with the largest distalization [(2.15 ± 0.91) mm and (1.85±1.09) mm], respectively, with significant difference between the T0 and T1 (@*CONCLUSIONS@#Clear aligner can effectively move mandibular molars farther, the crown is more effective than the root, and it is tilted. The second mandibular molar is more effective than the first mandibular molar in its distant displacement and three-dimensional changes. Molar distalization causes minor changes in mandibular incisors and facial soft and hard tissues.

Cephalometric evaluation of changes in vertical dimension and molar position in adult non-extraction treatment with clear aligners and traditional fixed appliances

ABSTRACT Introduction: Orthodontists have been using clear aligners to treat malocclusions, and one potential effect of treatment with orthodontic aligners is the intrusion and/or resists extrusion of the posterior teeth. This "bite-block effect" is primarily anecdotal due to the frequent occurrence of posterior open bites in patients after clear aligner therapy. Objective: The purpose of this study was to compare changes promoted by clear aligners and traditional fixed appliances in cephalometric measurements of the vertical dimension and molar position in adult patients with Class I malocclusion treated with non-extraction. Methods: Pre- and post-treatment lateral cephalometric radiographs of adult patients treated with either clear aligners (n=44) or traditional fixed appliances (n=22) were selected for retrospective analysis. Eight interval measurements and one nominal measurement were evaluated: anterior overbite (OB), mandibular plane angle related to cranial base (SN_MP) and related to Frankfort (FMA), lower molar height (L6H) and upper molar height (U6H), palatal plane to mandibular plane angle (PP_MP), lower facial height (LFH), total facial height (TFH), and posterior open bite (Posterior_OB). A single evaluator traced all cephalographs, and changes in select measures of the vertical dimension were compared within and between groups. Results: OB decreased (1.15 mm) and L6H increased (0.63 mm) in the traditional fixed appliance group. Mandibular plane angles (related to cranial base and to Frankfort) increased (0.43° and 0.53°, respectively) in the clear aligner group, but just FMA showed significant difference between groups (difference of 0.53°). LFH and TFH increased (ranging from 0.52 mm to 0.80 mm) in both groups, with no differences between treatment modality. Presence of visible posterior open bite significantly increased over the course of treatment. OB, FMA and L6H exhibited an interaction between treatment stage (pre- and post-treatment) and modality (clear aligner therapy and traditional fixed appliances), but no interaction among these three variables was found. Conclusions: The evidence does not support the theory that clear aligner therapy produces better vertical dimension control than traditional fixed appliances. Traditional fixed appliance therapy slightly extruded the lower molar, and clear aligner therapy produced a slightly mandibular backward rotation.

RESUMO Introdução: Ortodontistas têm usado os alinhadores transparentes para tratar más oclusões, e um potencial efeito desse tratamento é a intrusão e/ou resistência à extrusão dos dentes posteriores. Esse efeito de "bloco de mordida" é principalmente empírico, devido à ocorrência frequente de mordidas abertas posteriores em pacientes após a terapia com alinhadores transparentes. Objetivo: O objetivo do presente estudo foi comparar as mudanças promovidas pelos alinhadores transparentes e aparelho fixo convencional nas medidas cefalométricas de dimensão vertical e posição do molar em pacientes adultos com má oclusão de Classe I tratados sem exodontias. Métodos: Radiografias cefalométricas laterais pré- e pós-tratamento de pacientes adultos tratados com alinhadores transparentes (n=44) ou com aparelho fixo tradicional (n=22) foram selecionadas para uma análise retrospectiva. Oito medidas de intervalo e uma medida nominal foram avaliadas: trespasse vertical anterior (OB), ângulo do plano mandibular em relação à base do crânio (SN_MP) e em relação ao Plano de Frankfurt (FMA), altura do molar inferior (L6H) e altura do molar superior (U6H), ângulo do plano palatal ao plano mandibular (PP_MP), altura facial inferior (LFH), altura facial total (TFH) e mordida aberta posterior (Posterior_OB). Um único avaliador fez todos os traçados cefalométricos, e as mudanças nas medidas da dimensão vertical foram comparadas intra e intergrupos. Resultados: OB reduziu (1,15 mm) e L6H aumentou (0,63 mm) no grupo de aparelho fixo tradicional. Os ângulos do plano mandibular (em relação à base do crânio e ao plano de Frankfurt) aumentaram (0,43° e 0,53°, respectivamente). No grupo dos alinhadores invisíveis, apenas o FMA apresentou diferença significativa entre os grupos (diferença de 0,53º). LFH e TFH aumentaram (variando de 0,52 mm a 0,80 mm) em ambos os grupos, sem diferenças entre as modalidades de tratamento. A presença de uma mordida aberta posterior visível aumentou significativamente durante o curso do tratamento. OB, FMA e L6H exibiram interação entre o estágio do tratamento (pré- e pós-tratamento) e a modalidade (terapia com alinhadores invisíveis ou aparelho fixo tradicional), porém não foi encontrada interação entre essas três variáveis. Conclusões: A evidência não suporta a teoria de que a terapia com alinhadores invisíveis produz melhor controle da dimensão vertical do que o aparelho fixo. O tratamento com aparelhagem fixa extruiu ligeiramente o molar inferior, e o tratamento com alinhadores invisíveis produziu uma ligeira rotação posterior da mandíbula.

Expansion treatment using Invisalign®: Periodontal health status and maxillary buccal bone changes. A clinical and tomographic evaluation / Tratamiento de expansión con Invisalign®: estado de salud periodontal y cambios óseos maxilares. Evaluación clínica y tomográfica

ABSTRACT The aim of this study was to evaluate changes in periodontal status and maxillary buccal bone by considering clinical and tomographic parameters during the first year of orthodontic expansion with Invisalign® aligners. Upper first (1PM) and upper second (2PM) premolars of 19 patients with orthodontic expansion requirement treated with Invisalign® aligners were evaluated. Plaque index (PI), gingival index (GI), probing pocket depth (PPD), clinical attachment level (CAL) and cone beam tomographic (CBCT) records were collected at 76 sites before starting treatment (T0) and at 12 months (T1). Bone height was measured from cementoenamel junction (CEJ) to the crest cortical bone (CC). Bone thickness was measured at two levels: 4 mm (CEJ+4) and 6 mm (CEJ+6) apical to the CEJ. A descriptive analysis was made of the variations of bone thickness and height in a series of cases. The average expansion was 1.93 mm for 1PM and 167 mm for 2PM. Arithmetic mean of distance CEJ-CC in 1PM was 3.05 mm at T0, and remained at 3.05 mm at T1. Arithmetic mean of distance CEJ-CC in 2PM was 2.06 mm at T0 and 2.31 at T1. Post-expansion, most of the analyzed sites (86%) exhibited a bone thickness of ≥0.5 mm. The greatest variations between T0 and T1 were observed at the level of 1PM CEJ+ 4 and 2PM CEJ+ 6. The minimal changes in the clinical records (GI, PI, PPD and CAL) between T0 and T1 were compatible with the maintenance of gingivalperiodontal health. Invisalign® for expansion movements did not produce substantial changes in the evaluated periodontal clinical parameters or in the bone measurements. Removable appliances reduce plaque retentive factors and favor adequate oral hygiene.

RESUMEN El objetivo de este estudio fue evaluar los cambios en el estado periodontal y hueso facial maxilar a través de parámetros clínicos y tomográficos durante la expansión ortodóncica con alineadores Invisalign® en el primer año de tratamiento. Se evaluaron los primeros (1PM) y segundos (2PM) premolares superiores pertenecientes a 19 pacientes con requerimiento de expansión ortodóncica tratados con alineadores Invisalign®. Se registraron los índices de placa (IP), índice gingival (IG), profundidad al sondaje (PS) y nivel de inserción (NI) y registros tomográficos de haz cónico (CBCT) en 76 sitios antes de comenzar el tratamiento (T0) y a los 12 meses (T1). Se midió la altura ósea desde el límite amelocementario (LAC) hasta la cortical de la cresta (CC) y el espesor en dos niveles; a 4 mm (LAC+4) y a 6 mm (LAC+6) hacia apical del LAC. Se realizó un análisis descriptivo de las variaciones de la altura y espesor óseo en una serie de casos. La expansión promedio para 1PM fue de 1,93 mm y para 2PM fue de 1,67 mm. La media aritmética de LAC-CC en primeros premolares fue de 3,05 mm en T0 y se mantuvo el valor de 3,05 mm en T1. La media aritmética de LAC-CC en segundos premolares fue de 2,06 mm en T0 y 2,31 en T1. Post expansión, la mayoría de los sitios (86%) analizados exhibieron un espesor óseo ≥0,5 mm. Las mayores variaciones entre T0 y T1 se observaron a nivel de 1PM CEJ+4 y 2PM CEJ+6. Los registros clínicos (PI, GI, PPD y CAL) evidenciaron mínimos cambios entre T0 y T1, compatibles con el mantenimiento de la salud gíngivo-periodontal. El uso de Invisalign ® para movimientos de expansión no produjo cambios sustanciales en los parámetros clínicos periodontales evaluados ni en las mediciones óseas. La aparatología removible reduce los factores retentivos de placa bacteriana y facilita una adecuada higiene oral.

Three-dimensional finite element analysis on en-mass retraction of anterior teeth with clear aligner / 中华口腔医学杂志

Objective@#To investigate the mechanical effects during en-mass retraction of maxillary anterior teeth with clear aligner using three-dimensional finite element method.@*Methods@#Cone-beam CT (CBCT) was used to scan a female orthodontic patient (26 years old, from Department of Orthodontics, Stomatological Hospital of Chongqing Medical University) whose maxillary first premolars were extracted and maxillary dentition had been aligned and leveled. A finite element model including maxillary teeth-periodontal ligament (PDL)-alveolar bone-clear aligner was established by using Mimics 17.0, SolidWorks 2016 and Geomagic Studio 2015 software packages. The process of 0.2 mm en-mass retraction of anterior teeth using clear aligner was simulated by using non-linear contact method of Abaqus 6.14. The trend and displacement of maxillary teeth, the stress distribution of PDL and alveolar fossae, and the deformation trend of clear aligner were obtained and analyzed.@*Results@#Under the experimental condition, lingual crown tipping and distal tipping movement of anterior teeth were observed, and all of them had the tendency of overbite increasing.The maximum displacement of the central incisor, lateral incisor and canine were 25.16, 50.34 and 24.98 μm, respectively. Meanwhile, the second premolar, first molar and second molar had the tendency of mesial tipping movement, and the maximum displacement of them were 33.04, 2.90 and 16.63 μm, respectively. The stress distribution both at the PDL and alveolar fossae were consistent with tooth movement pattern. It was noted that the stress in the PDL of the canine and second premolar were comparatively big, and the corresponding apical areas of alveolar fossae appeared stress concentration. Concurrently, it was found that the clear aligner showed stress concentration at the junction of adjacent teeth with a tendency of crown directional dislocation.@*Conclusions@#During en-mass retraction of anterior teeth with clear aligner, attention should be paid to the overbite and torque in anterior teeth, and the anchorage protection of posterior teeth. At the same time, we should be careful of root resorption of the teeth on both sides of the extraction space.

Influences on periodontal health and conditions of patients with periodontitis by clear aligner treatment / 中华口腔医学杂志

No matter what kind of therapies you choose, clear aligner treatment (CAT) or fixed orthodontic treatment (FOT), the therapy must be performed on the basis of periodontal health and follow the rule that the treatment cannot be harmful to the periodontal tissues. Doctors and patients prefer the clear aligner treatment because of its features, such as aesthetic, removable and comfortable. There are many studies which consider the influences of CAT on the periodontal health, and the conclusions are relatively consistent. The CAT is more beneficial for the plaque-control and maintaining the periodontal health. However, there are a few articles which are talking about applying the CAT to the patients with severe periodontitis. This article mainly reviews the effect of CAT towards the patients with periodontitis, and provides some reference when the patients with severe periodontitis need to choose a proper treatment.