Total mesialization of the mandibular dentition using a mini-implant-supported device : A finite element analysis.

PURPOSE: Total mandibular arch mesialization using mini-implants is challenging due to anatomic limitations. The aim of this study was to introduce a mini-implant-supported device for total mesialization of the mandibular dentition and to analyze the biomechanical properties of the device. METHODS: Finite element models were constructed to explore the effect of friction and force direction on the force transmission efficiency of the device. In addition, the three-dimensional displacement of each tooth was evaluated with two force application points (2 or 8 mm hooks) under three force conditions (symmetric: 150 g of force on both sides, or asymmetric: 100 and 200 g of force on each side). RESULTS: The force transmission efficiency was 66.7% under a friction coefficient of 0.15 and parallel pushing and pulling forces. The force transmission efficiency was 65.90 and 66.63% when the pushing force was 15° away from the pulling force on the sagittal and horizontal planes, respectively. The mandibular dentition moved mesially with a greater tendency for incisor labial crown tipping, mesial molar rotation and buccal second molar crown tipping when using the 8 mm hook compared to that when using the 2 mm hook. Rigid archwires resulted in more consistent tooth mesialization than stainless steel archwires. Asymmetric forces resulted in asymmetric dental arch mesialization. CONCLUSION: The forces transmitted by the presented mini-implant-supported device varied depending on the friction level and force direction. The device should be able to achieve symmetric or asymmetric total mesialization of the mandibular dentition.

Asymmetric Extraction Decision in Orthodontics.

During the treatment planning process, extraction decisions are crucial. As a therapy option, the extraction of teeth should be considered in instances where there is a lack of facial harmony and stability in the occlusion. Treatment aims, the kind of malocclusion, aesthetic considerations, and growth patterns are all factors that influence asymmetric extraction. For the most part, premolar extractions are required when there is a significant midline difference or an asymmetrical connection between the teeth. Premolars, which are the first teeth to erupt and occupy the posterior position in chewing, are more vulnerable to injury than other permanent teeth. The optimal time to remove a second molar is at the moment when the connection between the molars has normalized or when a major front cross-bite can be remedied.

Correção de desvio de linha média dentária com o auxílio de ancoragem esquelética e extrações unilaterais ­ relato de caso / Correction of dental midline deviation with the aid of skeletal anchorage and unilateral extraction ­ case report

Resumo Atualmente temos pacientes mais preocupados com a estética facial, e essa tem sido o principal motivo para a procura do tratamento ortodôntico, sendo a linha média facial um fator importante na análise morfológica do sorriso do ponto de vista estético. O desvio da linha média dentária atinge o complexo dentoalveolar, e ocorre quando existe um desequilíbrio entre os dentes e a base apical, do hemiarco direito e esquerdo ou entre os dentes superiores e os inferiores. A utilização de microparafusos como unidades de ancoragem, além de anular os efeitos colaterais indesejáveis, simplifica a mecânica ortodôntica, fornece uma maior previsibilidade ao resultado do tratamento, proporciona maior conforto e estética ao paciente, reduz o tempo de tratamento e possibilita a correção de casos com perdas dentárias, já que fornece uma ancoragem direta. O objetivo principal deste trabalho foi demonstrar através de um relato de caso clínico a correção da assimetria de desvio da linha média e uma melhor harmonia facial com a utilização de exodontias assimétricas de pré-molares e o uso de microparafusos ortodônticos de titânio como ancoragem (AU)

Abstract Currently, patients are more concerned with facial aesthetics, and this has been the main reason for seeking orthodontic treatment, with the facial midline being an important factor in the morphological analysis of the smile from an aesthetic point of view. Deviation from the dental midline affects the dentoalveolar complex, and occurs when there is an imbalance between the teeth and the apical base, of the right and left hemiarch or between the upper and lower teeth. The use of microscrews as anchorage units, in addition to canceling undesirable side effects, simplifies orthodontic mechanics, provides greater predictability of treatment results, provides greater comfort and aesthetics to the patient, reduces treatment time and allows for correction of cases with tooth loss, as it provides direct anchorage. The main objective of this work was to demonstrate, through a clinical case report, the correction of midline deviation asymmetry and better facial harmony with the use of asymmetric extraction of premolars and the use of titanium orthodontic microscrews as anchorage(AU)

Does positional plagiocephaly affect the need for orthodontic treatment, and the mandibular and occlusal symmetry? / La plagiocéphalie positionnelle a-t-elle des répercussions sur le besoin de traitement orthodontique et sur la symétrie mandibulaire et occlusale ?

Introduction: Positional plagiocephaly (PP) is characterized by an asymmetrical flatness of the posterior part of the skull which may involve the frontal part of the skull and the face. The aim is to assess whether children and adolescents with PP have more occlusal and skeletal asymmetries and whether the need for orthodontic treatment is greater than in the healthy population. Material and Method: A comparative cross-sectional epidemiological study was carried out. One hundred children and adolescents were included: 50 in the PP group and 50 in the control group. The need for orthodontic treatment was assessed by the Index of Orthodontic Treatment Need (IOTN). The mandibular and dental asymmetries were measured on lateral cephalometry by two indexes: index of mandibular asymmetry (IMA) and index of dental asymmetry (IDA) respectively. Chi and Student independence tests were performed with a threshold of 5%. Results: The tests are significant for IMA (p = 0.02) and IOTN (p = 0.000012). IDA is insignificant. Discussion: Orthosurgical treatment of mandibular laterognathies by mandibular recentering sometimes creates mandibular asymmetry, while the shift is basal. We must be able to act early on the vault of the skull to hope to obtain a consecutive effect on the base and therefore on the position of the glenoid cavities. Management by manual therapy and early cranial orthosis could be estimated. Conclusion: The need for orthodontic treatment is significantly greater in PP. Unlike mandibular asymmetry, dental asymmetry is not significantly greater than in the control group, testifying to the adaptive capacities of the organism.

Introduction: Les plagiocéphalies positionnelles (PP) sont caractérisées par un aplatissement asymétrique de la partie postérieure du crâne pouvant impliquer la partie frontale du crâne et la face. L'objectif de cet article était d'évaluer si les enfants et les adolescents atteints de PP ont davantage de dissymétries occlusales et squelettiques, et si le besoin de traitement orthodontique est plus important que dans la population saine. Matériel et méthode: Une étude épidémiologique transversale comparative a été menée. Cent enfants et adolescents ont été inclus : 50 dans le groupe PP et 50 dans le groupe témoin. Le besoin de traitement orthodontique a été évalué par l'Index of Orthodontic Treatment Need (IOTN). La dissymétrie squelettique et dentaire a été évaluée radiologiquement par deux indices : l'Index of Mandibular Asymmetry (IMA) et l'Index of Dental Asymmetry (IDA). Des tests d'indépendance du Chi et Student ont été effectués avec un seuil de 5 %. Résultats: L'IMA (p = 0,02) et l'IOTN (p = 0,000012) sont significatifs. L'IDA est non significatif. Discussion: Le traitement ortho-chirurgical des latéromandibulies par recentrage mandibulaire crée parfois une dissymétrie mandibulaire, alors que le décalage est basal. Il faudrait pouvoir agir précocement sur la voûte du crâne pour espérer obtenir un effet consécutif sur la base et donc sur la position des cavités glénoïdes. Une prise en charge par thérapies manuelles et orthèse crânienne précoce pourrait être évaluée. Conclusion: Le besoin de traitement orthodontique est significativement plus important en cas de PP. Contrairement à la dissymétrie mandibulaire, la dissymétrie dentaire n'est pas significativement plus importante que dans le groupe témoin, témoignant des capacités adaptatives de l'organisme.

The Effect of Symmetric and Asymmetric Loading of Frontal Segment with Two Curved Cantilevers: An In Vitro Study.

Cantilevers generate statically determined force systems. The frontal segment loading with symmetric and asymmetric cantilevers in a three-piece intrusion base arch can be used to correct midline asymmetry. Three types of 0.017″ × 0.025″ beta-titanium cantilevers: tip-back (TB), deep curve (DC), utility arch (UA) were tested on typodonts simulating intrusion of the maxillary anterior segment. Typodonts with symmetric and asymmetric cantilevers were scanned with intraoral scanner (3Shape, TRIOS, Copenhagen, Denmark) before (T0) and after (T1) the experiment, scans were superimposed using Mimics software (Materialise, Leuven, Belgium). Data were analysed with qualitative analysis. All cantilevers generated vertical and horizontal forces. For symmetric design, the DC and TB displayed intrusive force with retrusive component, UA intrusion and protrusion. The asymmetric cantilevers produced transverse displacement of anterior segment. DC created lateral, UA medial force, the anterior segment displacement was consistent with the used configuration. The movement of an anterior segment with TB is smaller compared to DC and UA. Symmetric cantilevers configurations can achieve simultaneous intrusion and retrusion or protrusion of the anterior segment. The asymmetric design with transversal force can clinically aid the correction of midline discrepancies. The effect of the cantilever configuration on delivered force direction was confirmed.

Fotografía 2D en el diagnóstico de asimetrías faciales / 2D photography in facial asymmetry diagnosis

El objetivo de esta investigación es identificar la relación entre la asimetría facial y la pérdida de contacto en línea mediana entre dientes maxilares y mandibulares. Se realizó un estudio descriptivo en 18 sujetos portadores de asimetría facial que consultaron en la División de Cirugía Oral y Maxilofacial de la Universidad de La Frontera por tratamiento quirúrgico de la asimetría. En todos ellos se evaluó la presencia y grado de la asimetría facial y la presencia y desvío desde la línea mediana facial del punto mediano mandibular y maxilar mediante la prueba estadística t de student considerando un valor de p <0,05; todas las evaluaciones fueron realizadas mediante fotografías 2D de rostro y dientes obtenidas en condiciones estandarizadas. Se identificó que todos los sujetos portadores de asimetría facial presentaron asimetría dentaria; los desvíos dentarios fueron de casi 7 mm y existió relación estadísticamente significativa entre desvío facial y desvío dentario. Se concluye que los sujetos con asimetría dentaria pueden presentar asimetría facial de forma que la evaluación esqueletal del rostro es necesaria para realizar un diagnóstico correcto.

The aim of this research was to find the relation between facial asymmetry and loss of continuity in median line of maxillary and mandibular teeth. A descriptive study was carried out in 18 subjects with facial asymmetry with surgical indication and observed at the Division of Oral and Maxillofacial Surgery of the Universidad de La Frontera. In all of them the grade of facial asymmetry and the relation in median line of the maxillary and mandibular teeth was evaluated using the t student test considering p value < 0.05; all the evaluations were executed using 2D photography of the face and tooth obtained with standardized conditions. In all the subjects we observed dental asymmetry with almost 7 mm from the median line; statistical relations between dental asymmetry and facial asymmetry. It is concluded that in subjects asking for dental asymmetry treatment a facial evaluation is necessary in view of the relation with skeletal facial deformity.

Orthodontic retreatment of a Class III patient with significant midline asymmetry and bilateral posterior crossbite

Posterior crossbite might cause serious long-term functional problems if not early treated. Nevertheless, in older patients, treatment might include palatal expansion in order to correct such malocclusion. In view of the above, this article aims at reporting late correction of bilateral posterior crossbite associated with Angle Class III malocclusion, right subdivision, with consequent midline shift (good skeletal pattern). The case was presented to the Brazilian Board of Orthodontics and Dentofacial Orthopedics (BBO), with DI equal to or greater than 10, as a requirement for the title of certified by the BBO.

A mordida cruzada posterior pode causar sérios problemas funcionais em longo prazo, se não tratada precocemente. Porém, em alguns pacientes com idade mais avançada, ainda é possível realizar a disjunção palatina para corrigir essa condição. Assim sendo, o objetivo do presente caso é relatar a correção tardia de uma mordida cruzada posterior bilateral, associada a uma má oclusão de Classe III de Angle, subdivisão direita, com consequente desvios de linhas médias dentárias (bom padrão esquelético). Esse caso foi apresentado à Diretoria do Board Brasileiro de Ortodontia e Ortopedia Facial (BBO), se enquadrando na categoria IGC igual ou superior a 10, como requisito para revalidação do título de Diplomado.

The relationship between facialasymmetry and maxillary dental arch shape / 대한치과교정학회지

This study was designed to examine the dental asymmetry in person with facial asymmetry and to examine the relationship between the degree of mandibular deviation and asymmetry of maxillary dental arch. The samples were divided to asymmetry group and normal group. The asymmetry group consisted of 21 subjects(6 males and 15 females) and their mean age was 23.5 years. The normal group consisted of 20 subjects(10 males and 10 females) and their mean age was 18.6 Years. Anteroposterior, transverse position of all maxillary teeth except 3rd molars, vertical position of maxillary Ist molars, and angulation of central incisors were measured. The anterivposterior and transverse positions of teeth were measured on the maxillary dental casts, the vertical position of maxillary 1st molars and angulation of maxillary incisors were measured on posteroanterior cephalometiic radiographs. The data were analyzed to examine whether significant asymmetries existed in each of the asymmetry and normal groups. The results of this study were as follows : 1. In the asymmetry group, the correlation between the degree of mandibular deviation and that of 3-dimensional dental asymmetry was not so high. 2. In the asymmetry group, the teeth in deviated side were more laterally positioned than that of undeviated side. There were differences in the anteroposterior position of maxillary 1st and 2nd molars and the angulation of maxillary central incisors. 3. In the asymmetry group, the transverse asymmetry was larger in the posterior teeth rather than in the anterior teeth and larger than the anteroposterior asymmetry.