Minimization of dental implant diameter and length according to bone quality determined by finite element analysis and optimized calculation

The purpose of this study was to investigate the influences of bone quality and implant size on the maximum equivalent elastic strain (MES) in peri-implant bone using finite element (FE) analysis, and to minimize implant size via optimized calculation based on MES. Three-dimensional FE models consisting of a mandible and a titanium implant with a superstructure were constructed and applied a vertical load or an oblique load of 60N. We investigated the effects of four variables: the thickness of the cortical bone (C), Young’s modulus of the trabecular bone (T), and the diameter (D) and length (L) of the implant. According to the variables determined using Latin hypercube sampling, 500 FE models were constructed and analyzed under each of the loads following the construction of response surfaces with the MES as a response value. D and L were minimized by optimized calculation with the MES limited to the physiological limit with reference to the mechanostat theory. The MES was significantly influenced by D more than L, and could be restricted to the physiological limit unless both C and T were small. Larger MES than physiological limit was observed around the bottom of implants. From the viewpoint of the mechanostat theory, we calculated minimum size of implants according to the bone quality. However, the results should be verified with more detailed FE models made using CT data, animal studies and clinical prognoses.