ABSTRACT
OBJECTIVE: The objective was to evaluate the effects of the configuration of endodontic cavities with parallel or divergent walls, versus traditional endodontic cavities, on stress distribution, fracture resistance, and fracture mode of maxillary premolars by using both fracture-strength and finite element tests. METHOD AND MATERIALS: Thirty-two maxillary first premolars were divided into four groups (n = 8), according to the type of endodontic cavities: without endodontic cavities (control); conservative; conservative with diverging walls; and traditional. After performing root canal treatment and restoration, fracture resistance was evaluated by oblique compressive load. The stress distribution was evaluated by nonlinear finite element analysis by means of micro-computed tomography, operated at 50 kV and 800 mA. The fracture resistance data were analyzed by statistical software. RESULTS: Higher stress concentration was observed on the coronal portion of the palatal cusp and the palatal root dentin. Stress concentration on the palatal root dentin was similar for all groups. The stress level on the palatal cusp and at the proximal crests was slightly increased in the traditional endodontic cavities group compared with conservative endodontic cavities. Stress distribution in restored teeth was similar to that of intact teeth. No significant differences were observed in the fracture resistance among different endodontic cavities' design (P = .32). All groups had values similar to those of the control group (P > .05). CONCLUSIONS: Regardless of the cavity design, conservative endodontic cavities that preserve marginal ridge integrity did not affect the resistance to fracture, failure mode, or stress distribution in maxillary premolars restored with composite resin. Endodontically treated teeth displayed biomechanical behavior similar to sound teeth.
Subject(s)
Tooth Fractures , Tooth, Nonvital , Bicuspid , Composite Resins , Dental Cavity Preparation , Dental Restoration, Permanent , Dental Stress Analysis , Humans , X-Ray MicrotomographyABSTRACT
Estudou-se por meio de microscopia eletrônica de varredura, a capacidade de limpeza da técnica de instrumentação rotatória com limas de níquel-titânio Profile.04, associada a diferentes soluções químicas auxiliares do preparo biomecânico, em canais com achatamento mésio-distal. Vinte dentes incisivos inferiores humanos unirradiculares foram selecionados e divididos aleatoriamente em cinco grupos, instrumentados com o sistema Profile.04, um milímetro aquém do ápice anatômico e com instrumento memória de número 40, variando apenas a solução química auxiliar do preparo biomecânico, a saber: água destilada (grupo controle), hipoclorito de sódio a 1 por cento, hipoclorito de sódio a 1 por cento alternado com EDTAC a 17 por cento e hipoclorito de sódio a 1 por cento associado ao creme EndoPTC. Após o preparo biomecânico, os espécimes foram seccionados longitudinalmente e preparados para microscopia eletrônica de varredura. As fotomicrografias obtidas dos terços apicais foram submetidas a avaliação por dois docentes de Endodontia, que atribuíram escores às imagens. Os resultados evidenciaram diferença estatística ao nível de 1 por cento entre as soluções químicas auxiliares estudadas. A solução de hipoclorito de sódio a 1 por cento associada ao creme EndoPTC e a água destilada foram estatisticamente semelhantes, apresentando a maior quantidade de smear layer. A solução de hipoclorito de sódio a 1 por cento alternado com EDTAC a 17 por cento apresentou paredes dentinárias livres de smear layer, com exposição de grande quantidade de canalículos
