RESUMO
INTRODUCTION: Multiple force vector applications may be indicated when an arch segment or en masse intrusion is needed. This finite element method study aimed to evaluate the total deform the stress yielded in the bone and the miniplate when forces with different directions and magnitudes were applied. METHODS: First, the prototyped skull model was fabricated on the basis of computed tomography (CT) scans. On this model, the miniplate was fixed, and orthodontic appliances were attached. Then, a 3-dimensional finite element model was constructed by reproducing the characteristics of the physical model. Seven situations were investigated, which diverged in the point of force application, the direction and the number of force vectors, and the force magnitudes. RESULTS: When the force was applied at 1 point, similar behavior could be observed concerning the deformation and the stress in the miniplate, the maxilla, and the screw holes. Most deformation and stress appeared in the transmucosal arm below the step bend and at the force application point. The angled vectors (-45° and 30°) presented smaller values concerning the vertical vectors. Similar or better performances could be observed when the forces were simultaneously applied at the 2 points. CONCLUSIONS: The newly designed miniplate showed similar or improved performances when multiple vectors were applied at the 2 points simultaneously compared with the force applied at 1 point. This newly designed miniplate may present improved performance in a clinical situation when multiple forces are demanded.
RESUMO
OBJETIVO: avaliar a resistência ao cisalhamento da colagem de braquetes e o Índice de Remanescente de Adesivo (IRA) dos compósitos Concise e Transbond XT com ou sem agente de união. MÉTODOS: a amostra consistiu de 60 incisivos bovinos divididos em 4 grupos (n=15). Em todos os corpos de prova foram realizados profilaxia com pedra-pomes e condicionamento do esmalte com ácido fosfórico a 37 por cento. Nos Grupos 1 e 2, foram colados braquetes com o compósito Concise, respectivamente, com e sem aplicação da resina fluida. Nos Grupos 3 e 4, utilizou-se o Transbond XT, respectivamente, com e sem aplicação do XT Primer. Nesses dois últimos grupos, as colagens foram fotopolimerizadas por 40 segundos. O ensaio de resistência ao cisalhamento da amostra foi realizado em máquina Instron à velocidade de 0,5mm/min e, em seguida, foi avaliado o IRA. RESULTADOS: com relação à resistência ao cisalhamento, o Grupo 4 foi estatisticamente superior aos Grupos 1 e 2 (p<0,05) e sem diferença estatística significativa em relação ao Grupo 3 (p>0,05). Não foram encontradas diferenças estatísticas significativas entre os Grupos 1, 2 e 3 (p>0,05). Como resultados do IRA, o Grupo 3 foi estatisticamente superior ao Grupo 2 (p<0,05), porém sem diferenças estatísticas significativas em relação ao Grupos 1 e 4 (p>0,05). Não foram encontradas diferenças estatísticas significativas entre os grupos 1, 2 e 4 (p>0,05). CONCLUSÃO: os compósitos Concise e Transbond XT obtiveram valores de resistência adesiva adequados com ou sem a utilização de seus respectivos agentes de união.
OBJECTIVES: The aim of this study was to evaluate the shear bond strength of brackets and the adhesive remnant index (ARI) of Concise and Transbond XT composites with and without the use of a bonding agent. METHODS: The sample consisted of 60 bovine incisors divided into four groups (n=15). All teeth were subjected to prophylaxis with pumice and enamel etching with phosphoric acid at 37%. In Groups 1 and 2 brackets were bonded with Concise composite with and without application of enamel bond resin, respectively. In Groups 3 and 4, Transbond XT was used with and without XT Primer application, respectively. In these latter groups bonding was light cured for 40 seconds. Specimen shear strength testing was performed on an Instron machine at 0.5 mm/min, and ARI was subsequently evaluated. RESULTS: Shear bond strength in Group 4 was statistically higher than in Groups 1 and 2 (p<0.05) but not when compared to Group 3 (p>0.05). There were no statistically significant differences between Groups 1, 2 and 3 (p>0.05). ARI in Group 3 was statistically higher than in Group 2 (p<0.05), but not statistically different from Groups 1 and 4 (p>0.05). There were no statistically significant differences between Groups 1, 2 and 4 (p>0.05). CONCLUSION: The composites Concise and Transbond XT showed adequate bond strength with or without the use of their respective bonding agents.
