Influence of finish line in the distribution of stress trough an all ceramic implant-supported crown.: A 3D Finite Element Analysis.

Purpose: The aim of this study was to evaluate, by finite element analysis (FEA), the influence of finish line on stress distribution and resistance to the loads of a ZrO(2) crown and porcelain in implant-supported.
Material and Methods: The object of this analysis consisted of a fxture, an abutment, a passing screw, a layer of cement, a framework crown, a feldspatic porcelain veneering. The abutment's marginal design was used in 3 different types of preparation: feather edge, slight chamfer and 50°, each of them was of 1 mm depth over the entire circumference. The ZrO(2)Y-TZP coping was 0.6 mm thick. Two material matching for the abutment and the framework was used for the simulations: ZrO(2) framework and ZrO(2) abutment, ZrO(2) framework and T abutment. A 600 N axial force distributed over the entire surface of the crown was applied. The numerical simulations with finite elements were used to verify the different distribution of equivalent von Mises stress for three different geometries of abutment and framework.
Results: Slight chamfer on the matching ZrO(2) - ZrO(2) is the geometry with minimum equivalent stress of von Mises. Even for T abutment and ZrO(2) framework slight chamfer is the best configuration to minimize the localized stress. Geometry that has the highest average stress is one with abutment at 50°, we see a downward trend for all three configurations using only zirconium for both components.
Conclusions: Finite element analysis. performed for the manifacturing of implant-supported crown, gives exact geometric guide lines about the choice of chamfer preparation, while the analysis of other marginal geometries suggests a possible improved behavior of the mating between ZrO(2) abutment and ZrO(2) coping. for three different geometries of the abutment and the coping.