Finite element study on modification of bracket base and its effects on bond strength

OBJECTIVE: This article aims to analyze the difference in stresses generated in the bracket-cement-tooth system by means of a peel load in single and double-mesh bracket bases using a three-dimensional finite element computer model. MATERIAL AND METHODS: A three-dimensional finite element model of the bracket-cement-tooth system was constructed and consisted of 40,536 bonds and 49,201 finite elements using a commercial mesh generating programmer (ANSYS 7.0). Both single and double-mesh bracket bases were modified by varying the diameter from 100-400 µm progressively, and the spacing between the mesh wires was kept at 300 µm for each diameter of wire. A peel load was applied on the model to study the stresses generated in different layers. RESULTS: In case of double-mesh bracket base, there was reduction in stress generation at the enamel in comparison to single-mesh bracket base. There was no difference in stress generated at the bracket layer between single and double-mesh bracket bases. At the impregnated wire mesh (IWM), layer stresses increased as the wire diameter of the mesh increased. CONCLUSION: Results show that bracket design modification can improve bonding abilities and simultaneously reduce enamel damage while debonding. These facts may be used in bringing about the new innovative bracket designs for clinical use. .

OBJETIVO: o objetivo do presente artigo é analisar a diferença entre as tensões geradas na interface braquete-cemento-dente por meio do teste peel load em bases de braquete de malha simples e dupla e do método de elementos finitos tridimensional. MÉTODOS: foi construído um modelo de elementos finitos do sistema composto pela interface braquete-cemento-dente. Esse modelo consistiu de 40.536 nós e 49.201 elementos finitos. A análise foi feita com a ajuda do programa ANSYS 7.0. Tanto a base de braquete de malha única quanto a de malha dupla sofreram modificações no diâmetro, que variou de 100 a 400µm, progressivamente. O espaço entre os fios das malhas foi mantido a 300µm para o diâmetro de cada fio. O teste peel load foi aplicado ao modelo para investigar as tensões geradas nas diferentes camadas. RESULTADOS: quando comparadas às bases de braquetes de malha simples, as bases de braquetes de malha dupla geraram menos tensão no esmalte dentário. Não foram detectadas diferenças entre as tensões geradas na superfície dos braquetes com bases de malha simples e dupla. Na malha de fios impregnados (MFI), houve um aumento na tensão com o aumento do diâmetro dos fios que compõem a malha. CONCLUSÃO: os resultados revelam que as modificações no desenho do braquete podem aumentar a colagem e, ao mesmo tempo, minimizar os danos causados no esmalte durante o processo de descolagem. Esses fatos podem ser utilizados no desenvolvimento de desenhos de braquetes inovadores, destinados à utilização clínica. .

A 3-D Analysis To Study The Center of Resistance Modification With Alveolar Bone Resorption - A Finite Element Method.

The aims of this investigation were to define the modified location of CRES and CROT in a maxillary central incisor with different alveolar bone heights. A three dimensional finite element model of the upper central incisor with its supporting structures was created using ANSYS software on a PIII computer. Five three dimensional models of an upper central incisor with 1 to 6.5 mm of alveolar bone loss were formulated and used by the author. Center of resistance and center of rotation were located for the various stages of alveolar bone loss. The results revealed that the moment/force ratio (at the bracket level) required to produce bodily movement increases in association with alveolar bone loss. Bone loss causes center of resistance movement towards the apex, but its relative distance to the alveolar crest decreases at the same time. Greater amounts of displacements of incisal edge and apex were observed with increased alveolar bone loss for a constant applied force. Center of rotation of the tipping movement also shifted towards the cervical line. Among the many differences between orthodontic treatment of an adolescent and an adult patient is the presence of alveolar bone loss in the adult cases. Alveolar bone loss causes change in center of resistance as a result of alteration in bone support. This necessitates modifications in the applied force system to produce the same movement as in a tooth with a healthy supporting structure.