Distribuição de tensões em coroas totais com sistema metal-free por meio do método de elementos finitos

Abstract

This study compared the stress distribution between three-dimensional lower first molar crowns of indirect resin Lava Ultimate (3M ESPE) (LU) and ceramic IPS e.max CAD (Ivoclar Vivadent) (Emax) against the application of functional load. Three variables were studied by the method of finite elements: the type and thickness of restorative material (1 or 2 mm) as well as the direction of the applied load (axial or oblique). On a modeling software (Rhinoceros; 5.0, Robert Mcneel & associates, USA), CAD models of total crown preparation were generated with different thicknesses of occlusal wear and their indirect restorations. Then in Femap® (10.2, Siemens PLM Software, USA) software, the construction of the finite element mesh was made. After checking the quality of this, the elastic modulus and Poisson's ratio of the tested materials were inserted in the program. After, in Nei Nastran software (10.0.3.7, NEi Software, USA), it was carried out the study of stress distribution from the simulation of models with a load of 200 N on the central fossa region and near the tip of the distobuccal cusp ridge, corresponding to a lower first molar crown. Data analysis was based on a qualitative description of the generated images and also on the values of maximum principal stress of each CAD model. According to the results, the LU crowns behaved as transmission structures of stresses and the complex tooth/restoration as a single block in which stress was distributed more evenly. In Emax crowns, however, the tensile stresses concentrated particularly along the thickness of the material. The more favorable stress distribution was obtained with the 2 mm thickness crowns in an axial occlusal load application, especially for the LU material.