The purpose of this study is to determine the most stable fixation method for mandibular symphysis fractures by comparing the mechanical characteristics of models fixed at different positions with different numbers of plates. Fractures were generated in 3-dimensional finite element models, and were fixed with a single miniplate, parallel double miniplates, or perpendicular double miniplates. A 300 N perpendicular load was then applied on the left molar region, and a finite element analysis was performed. We compared vertical gaps between the fractured surfaces, maximum stress within the screw/plating system, and maximum stress around screw holes in the bone. Compared to the single miniplate, both the parallel and perpendicular double miniplates demonstrated significantly less stress in the screw/plating system and screw holes in the bone. In addition, the perpendicular double miniplates had significantly smaller vertical gaps between fracture surfaces when compared to the single miniplate. Comparing parallel and perpendicular double miniplate fixations, less stress was found around the screw holes of the perpendicular miniplate models than those of the parallel miniplate models. There were no differences in vertical gaps or maximum stress within the screw/plating systems between the 2 double miniplate fixations. These results suggest that perpendicular double miniplate fixation is more suitable for fixing mandibular symphysis fractures.
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