Avaliação da tensão provocada no ligamento periodontal durante o movimento de verticalização de molares inferiores pelo método dos elementos finitos 3D / Evaluation of tension caused by periodontal ligament during mandibular second molars uprighting by 3D finite elements method

A necessidade de tratamento ortodôntico está cada vez maior em pacientes adultos que procuram por reabilitação protética, pois muitos necessitam a verticalização de molares inferiores. Objetivou-se avaliar a máxima tensão provocada no ligamento periodontal por diferentes tamanhos de raízes durante o movimento de verticalização de segundos molares inferiores pelo método dos elementos finitos em 3 dimensões. Foram utilizados três modelos virtuais. Foi confeccionado um modelo de dente com dimensão total de 19,64 mm, sendo 11,41 mm de raiz (raiz média). Desta raiz, foi acrescido 2 mm em um modelo (raiz longa) e retirado 2 mm de outro (raiz curta). Dentre os critérios de interpretação, foi utilizado o proposto por von Mises (máxima energia de distorção). Avaliando a tensão na região da furca, observou-se maior tensão no dente com raiz média (0,026 MPa), assim como aconteceu na região cervical mesial (0,036 MPa). Na região cervical distal a raiz curta teve comportamento inverso ao seu comprimento, sendo o maior valor de tensão 0,023 MPa. Na região apical mesial, o dente com raiz curta obteve o maior valor (0,012 MPa), assim como aconteceu na região apical distal (0,016 MPa). Concluiu-se que na região cervical mesial, obteve-se a maior tensão e no ápice mesial a menor tensão dos 3 tamanhos radiculares comparados com as outras áreas do ligamento periodontal. A maior variação de tensão máxima ocorreu na região apical, principalmente na região mesial. O dente com tamanho radicular curto foi o que sofreu maior tensão em ambas as regiões de ápice. (AU)

The need for orthodontic treatment is increasing in adults looking for prosthetic rehabilitation because many need molar uprighting. The aim of this study was evaluate the maximum tension caused in the periodontal ligament by different sizes of roots during mandibular second molars uprighting by the finite element method in three dimensions. Three virtual models were used. A tooth model was made with the total size of 19.64 mm, being 11.41 mm root (medium root). This root was plus 2 mm in a model (long root) and removed 2 mm of other (short root). Among the criteria of interpretation, it was used the proposed by von Mises (maximum distortion energy). Evaluating the tension in furcation region, the highest tension value was in the tooth with medium root (0.026 MPa) as well as occurred in the mesial cervical region (0.036 MPa). At the distal cervical region, the short root had an opposite behavior to its length, being the highest tension value (0.023 MPa). In mesial apical region, the tooth with short root had the highest value (0.012 MPa) as well as occurred in the distal apical region (0.016 MPa). It was concluded that the mesial cervical region obtained the highest tension and in the mesial apical region the lowest tension of the 3 sizes of root comparing to the other areas of the periodontal ligament. Most maximum tension variation occurred in the apical region, especially at the mesial region. The tooth with short root size has suffered the greatest tension in both apical regions (AU)

Distribution of stress on TMJ disc induced by use of chincup therapy: assessment by the finite element method.

OBJECTIVE: To assess the distribution of stress produced on TMJ disc by chincup therapy, by means of the finite element method. METHODS: a simplified three-dimensional TMJ disc model was developed by using Rhinoceros 3D software, and exported to ANSYS software. A 4.9N load was applied on the inferior surface of the model at inclinations of 30, 40, and 50 degrees to the mandibular plane (GoMe). ANSYS was used to analyze stress distribution on the TMJ disc for the different angulations, by means of finite element method. RESULTS: The results showed that the tensile and compressive stresses concentrations were higher on the inferior surface of the model. More presence of tensile stress was found in the middle-anterior region of the model and its location was not altered in the three directions of load application. There was more presence of compressive stress in the middle and mid-posterior regions, but when a 50o inclined load was applied, concentration in the middle region was prevalent. Tensile and compressive stresses intensities progressively diminished as the load was more vertically applied. CONCLUSIONS: stress induced by the chincup therapy is mainly located on the inferior surface of the model. Loads at greater angles to the mandibular plane produced distribution of stresses with lower intensity and a concentration of compressive stresses in the middle region. The simplified three-dimensional model proved useful for assessing the distribution of stresses on the TMJ disc induced by the chincup therapy.

Distribution of stress on TMJ disc induced by use of chincup therapy: assessment by the finite element method

ABSTRACT Objective: To assess the distribution of stress produced on TMJ disc by chincup therapy, by means of the finite element method. Methods: a simplified three-dimensional TMJ disc model was developed by using Rhinoceros 3D software, and exported to ANSYS software. A 4.9N load was applied on the inferior surface of the model at inclinations of 30, 40, and 50 degrees to the mandibular plane (GoMe). ANSYS was used to analyze stress distribution on the TMJ disc for the different angulations, by means of finite element method. Results: The results showed that the tensile and compressive stresses concentrations were higher on the inferior surface of the model. More presence of tensile stress was found in the middle-anterior region of the model and its location was not altered in the three directions of load application. There was more presence of compressive stress in the middle and mid-posterior regions, but when a 50o inclined load was applied, concentration in the middle region was prevalent. Tensile and compressive stresses intensities progressively diminished as the load was more vertically applied. Conclusions: stress induced by the chincup therapy is mainly located on the inferior surface of the model. Loads at greater angles to the mandibular plane produced distribution of stresses with lower intensity and a concentration of compressive stresses in the middle region. The simplified three-dimensional model proved useful for assessing the distribution of stresses on the TMJ disc induced by the chincup therapy.

RESUMO Objetivo: avaliar, por meio do método dos elementos finitos, a distribuição das tensões no disco articular produzidas pela mentoneira ortopédica. Métodos: um modelo tridimensional simplificado do disco articular foi desenvolvido com o software Rhinoceros 3D e exportado para o software ANSYS. Uma carga de 4,9 N (500 gf) foi aplicada na superfície inferior do modelo, com inclinação de 30, 40 e 50o em relação ao plano mandibular Gônio-Mentoniano (GoMe). O ANSYS analisou, por meio do método dos elementos finitos, a distribuição das tensões presentes no modelo do disco articular para as diferentes angulações. Resultados: os resultados mostraram que a concentração das tensões de tração e compressão foi maior na superfície inferior do modelo. A tensão de tração foi mais presente na região média-anterior do modelo, e sua localização não se alterou nas três direções da aplicação da carga. A tensão de compressão foi mais presente nas regiões média e média-posterior do modelo, mas quando a carga a 50o foi aplicada, ela se concentrou na região média. As intensidades das tensões de tração e compressão diminuíram progressivamente à medida que a carga foi aplicada mais verticalmente. Conclusão: as tensões induzidas pela mentoneira ortopédica se localizaram principalmente na superfície inferior do modelo. As cargas com maior angulação em relação ao plano mandibular produziram uma distribuição de tensões com menor intensidade e uma concentração da tensão de compressão na região média do modelo. Um modelo tridimensional simplificado se mostrou útil na avaliação da distribuição das tensões no disco articular induzidas pela mentoneira ortopédica.