Optimal design for wall thickness of dental implants using finite element method

It is critical to achieve an ideal relationship among major components of an implant system in the limited width of alveolar bone. The aim of the present work was to develop implant fixture models to predict maximum stress concentration sites and distribution contours after loading. Three-dimensional finite element models of a standard Brånemark fixture with different wall thicknesses were developed and the geometric details, such as threads of inner and outer screws were realistically modeled. A maximum lateral force of 150 N was applied to simulate horizontal occlusal forces to predict stress distribution contours within the implant system using an optimal design technique (APDL, ANSYS Parametric Design Language). The effects of different wall thicknesses and boundary levels of the fixtures were then evaluated to help design a better implant system. When the fixtures were directly constrained to simulate different boundary levels, the maximum equivalent stress (max EQV) was always located at the implant-bone interface. Max EQV increased when the wall thickness or boundary level was reduced to a certain extent. The fixture with a wall thickness of 0.97 mm demonstrated the smallest stress increase ratio when the boundary level was lowered. The relationship between wall thickness of the fixture and the boundary level played an important role in maintaining a well-distributed stress level within the fixture.