Experimental and computational evaluation of the composite resins fractures lines

Objectives: The aim of this study was to compare the fracture lines observed after “in vitro” flexural strength test of composite resins with simulation of crack propagation in the finite element method. Methods: The composite resins selected for this work were: Tetric N-Ceram – nano-hybrid (Ivoclar, Schaan, Liechtenstein), Filtek Z350 – nanoparticulated (3M, St Paul, MN, USA) and Heliomolar – microparticulated (Ivoclar, Schaan, Liechtenstein). In the first stage, the flexural strength test was carried out according to the ISO 4049:1988. Furthermore, a numerical simulation using finite element analysis was performed to investigate two hypothetical stages of crack propagation: 50% and 80% of propagation. Were made cuts on the surface to show the division between the cracked and the intact parts. Results: In a speculative analysis of the maximum principal stresses at the crack tip, it was observed that at the crack opening of 50% the model showed a distortion in the stress field with significant concentration at the crack tip. The shape of the dissipation of stress field indicates that the crack propagation is mainly vertical, according to what was observed experimentally. In the simulation of the crack opening in 80% of the model, it was observed a new format of the stress field, more flattened and irregular, favoring a more statistical propagation of the crack tip, difficulting the determination of its final direction of propagation. For this shape of the stress field, it is possible the occurrence of a crack propagation radially in any direction, which justifies the occurrence of chipping or straight fracture presented in the specimens in experimental testing. Conclusion: When analyzing the specimen and virtual model is observed that the fracture lines were coincident. In addition, the finite element analysis was an effective tool for evaluating and simulating of the crack propagation of composite resins.