Two and three-dimensional finite element method to investigate failure mode from shear and micro-shear tests on dental restorations

ABSTRACT

This study analyzed by means of conventional shear and microshear bond strength tests types of fractures and it verified stress distribution in the interface by finite element method. The models were composed of dentin, adhesive and composite resin. As simplification of the methodology the materials were considered elastic-linear and isotropic. Two and three-dimensional models were created for both tests and the forces applied in the tests were 50 N for shear and 15 N for microshear. The failure criterion approached was Mohr-Coulomb that describes the response of fragile materials, so the analyses were given in relation to σ1, σ3 e τ_máx.. The maximum shear stresses were compared with the nominal stresses of the models and it was observed that the shear model has a greater variation compared to microshear. Another important point raised is that tensions distribution in the two-dimensional model is similar to the three-dimensional model, thus, the model can be simplified to a two-dimensional analysis in this aspect. Although shear stresses are applied, the material failed by traction, a factor observed when analyzing the shear test. By graphically analyzing the modified Mohr-Coulomb failure criterion, it was possible to observe a cohesive dentin failure for shear test and adhesive failure for microshear test, and also the τ_nom values were closer to τ_máx microshear test. Thus, the study allows the conclusion that the methodology developed of adhesive resistance for the microshear test is validated by computational simulation.

Keywords
shear; micro-shear; dentin; bond strength; finite element analysis