Three-dimensional finite element analysis of mechanical stress in symphyseal fractured human mandible reduced with miniplates during mastication.

PURPOSE In this study we tried to analyze the stress distribution in a symphyseal fractured human mandible reduced by 2 different methods--reduction with 1 miniplate or with 2 miniplates--by using finite element (FE) analysis, and then compared the results with an intact mandible. MATERIALS AND METHODS Three-dimensional FE models of an intact mandible and symphyseal fractured mandibles reduced by 2 fixation methods were developed to analyze mandibular stress distribution and bite forces under 2 basic loading conditions, namely, clenching in the intercuspal position and left unilateral molar clenching. Groups of parallel vectors were used to simulate 9 pairs of masticatory muscles involved in the 2 static biting tasks. RESULTS Stress distributions in reduced mandible with 1 or 2 miniplates were more or less different from that of the intact mandible. The maximum stress occurred at the biting point. Meanwhile, the subcondylar region was a stress-bearing area. During left unilateral molar clenching, bite forces obviously reduced after fracture. Bite force and the stress distribution pattern in the mandible reduced with 2 miniplates were closer to that in the intact mandible. CONCLUSIONS It is suggested that the effect of the miniplates in stabilizing the continuity-broken mandible influence the restorations of the stress distribution pattern and bite force. Two miniplates have a biomechanical advantage over 1 miniplate on these restorations.