Effect of dental implant cross-sectional design on cortical bone structure using finite element analysis.

PURPOSE: This finite element analysis investigation evaluated the effect of different implant cross-sectional designs on bone stress levels under different loading patterns. MATERIALS AND METHODS: Finite element analysis program was used to construct four different three-dimensional models describing 4x10-mm implants in blocks of cortical and trabecular bone. A 5-mm-long abutment was modeled above each implant. The implant in model 1 was unthreaded, while in model 2 the implant was circularly threaded. The third implant in model 3 had the cross-sectional shape as a 16-sided star-shaped design. The implant in model 4 was constructed unthreaded, with a diameter of 4.5 mm. Vertical and horizontal loads of 100 N each were applied on the top middle node of each implant assembly. All nodes at the bottom surface of the bone models were restrained. RESULTS: By comparing models 1, 2, and 3, the lowest bone stress values under vertical and horizontal forces were observed around the unthreaded implant in model 1 (8.92 and 94.52 MPa, respectively). The highest stress value under vertical loading was shown around the threaded implant in model 2 (10.07 MPa), whereas the highest stress value under horizontal loading was observed around the star-shaped implant in model 3 (108.40 MPa). Model 4, with a wider unthreaded design, had stress values under vertical and horizontal loading of 7.32 and 71.35 MPa, respectively. CONCLUSIONS: It was concluded that the unthreaded implant design produced the least bone stress. An increase in implant diameter could produce marked reduction in stress value in the bone around the neck of the implant.