How does arch form and interproximal contact size affect the 3D displacements and rotations of teeth: a finite element analysis

ABSTRACT Objective: The objective of this study was to determine how arch form and interproximal contact size displace mandibular teeth subjected to an anterior component of force (ACF). Methods: Nine finite element models (FEM) of the mandibular arch were developed using Ansys® v. 16.0 software. They were designed to evaluate the effects of three arch forms (triangular, oval, and square) and three contact sizes (point-to-point, 1 mm diameter, and 2 mm diameter). All nine models were subjected to an ACF of 53.8 N (5486 gm). Three-dimensional tooth rotations and displacements of the mandibular teeth were evaluated, from the right first molar to the left first molar. Results: Arch form had a greater effect on tooth movements than contact size. Triangular arches and point-to-point contacts produced the greatest displacements and rotations of teeth. Oval arches with 2 mm wide interproximal contact points showed the greatest stability. The right first premolar showed the greatest displacements in all of the models. Conclusions: Arch form and contact size affect interproximal tooth stability. Teeth are least stable in narrow arches with point-to-point interproximal contacts, and most stable in wider arches with larger contacts.

RESUMO Objetivo: O objetivo deste estudo foi determinar como o formato da arcada e o tamanho do contato interproximal deslocam os dentes inferiores submetidos a um componente anterior de força (CAF). Métodos: Nove modelos de elementos finitos (MEF) da arcada inferior foram desenvolvidos utilizando o software Ansys® v. 16.0. Eles foram projetados para avaliar os efeitos de três formatos de arcada (triangular, oval e quadrado) e três tamanhos de contato interproximal (ponto a ponto, 1 mm de diâmetro e 2 mm de diâmetro). Todos os nove modelos foram submetidos a um CAF de 53,8 N (5486 gm). Foram avaliados tridimensionalmente as rotações dentárias e os deslocamentos dos dentes inferiores, do primeiro molar direito ao primeiro molar esquerdo. Resultados: A forma da arcada teve um efeito maior no movimento dos dentes do que o tamanho do contato interproximal. Arcadas triangulares e contatos ponto a ponto produziram os maiores deslocamentos e rotações dos dentes. Arcadas ovais com pontos de contato interproximal de 2 mm de largura apresentaram maior estabilidade. O primeiro pré-molar direito apresentou os maiores deslocamentos em todos os modelos. Conclusões: O formato da arcada e o tamanho do contato interproximal afetam a estabilidade dos dentes. Os dentes foram menos estáveis nas arcadas estreitas com contatos interproximais ponto a ponto, e mais estáveis nas arcadas mais largas com contatos maiores.

Correlation of caries susceptibility with different means of tooth surface and patients' oral hygiene habits after interproximal enamel reduction in clinical practice / 中华医学美学美容杂志

Objective To explore the correlation of caries susceptibility of patients with the immediate tooth polish,application of fluoride,and the patients' oral hygiene habits after interproximal enamel reduction (IER) in clinical practice.Methods The present study retrospectively collected 45 cases of IER (18 males and 27 females) in 196 tooth sites.Each sample was examined clinically and radiologically to obtain the incidence of caries,and the outcome was correlated with amount of IER,tooth polish,application of fluoride,and the brushing method and frequency for statistical analysis.Results The present study showed that there was no statistical significance among the amount of IER,the site of IER,the patients' brushing method,and the gender with the susceptibility of caries.However,there was statistical significance among the application of fluoride,tooth polish and brushing frequency with the susceptibility of caries.Conclusions The current research suggests that it is desirable to polish tooth and apply fluoride for patients with IER in clinical practices.In the meanwhile,the clinician should pay attention to patients' oral hygiene habits,especially brushing frequency,due to the positive correlation between the brushing frequency and incidence of caries.

Redução de esmalte interproximal como alternativa no tratamento ortodôntico de casos limítrofes: [revisão] / Interproximal enamel stripping as orthodontic treatment alternative in borderline cases: [review]

INTRODUÇÃO: o plano de tratamento ortodôntico deve considerar fatores como apinhamento dentário, protrusão dentoalveolar, discrepâncias maxilares e necessidade de alteração do perfil facial. Também se deve ter em mente as características de normalidade conforme a raça do paciente. Assim, buscando uma abordagem individual do paciente, em casos limítrofes, a terapia ortodôntica pode ser realizada com ou sem extrações. OBJETIVO: realizar uma revisão da literatura sobre a terapia de redução de esmalte interproximal como uma alternativa de tratamento ortodôntico sem extrações para pacientes considerados limítrofes e exemplificar a técnica a partir do relato de um caso clínico. MÉTODOS: para a execução da redução, usou-se brocas Carbide em alta rotação para a remoção do esmalte, discos Sof-Lex para o acabamento e polimento das superfícies desgastadas e aplicação tópica de fluoretos, visando aumentar a proteção do esmalte. CONCLUSÃO: concluiu-se que a técnica é indicada na resolução de discrepâncias no comprimento do arco dentário de até 8,5mm, a fim de evitar as extrações dentárias em pacientes com bom perfil facial. Preferencialmente, os dentes submetidos à técnica devem ser largos, com forma triangular e paredes de esmalte espessas.

INTRODUCTION: The orthodontic treatment plan must consider factors like dental crowding, dental alveolar protrusion, maxillary discrepancies and the facial profile change necessity. It must be considered that the normal characteristics changes in conformity with the ethnic origin of the patient. Then, searching for the individualization of treatment for each patient, in borderlines cases the orthodontic therapy can be done with or without extractions. AIM: To review the literature about the interproximal enamel reduction therapy as an orthodontic treatment alternative to extractions in this borderline patients and to exemplify the technic with a case report. METHODS: To execute the enamel reduction it was used the high-speed Carbide bur and Sof-Lex discs to polish the striped surfaces, followed by topic application of fluoride to increase enamel protection. CONCLUSION: Technic is indicated to solve discrepancies in the dental arch smaller than 8,5mm, to avoid extractions in patients with good facial profile. It's mandatory that the teeth to be striped must be large, triangular and with thick proximal enamel layers.