Abstract: Objective To provide theoretical support for mandibular rigid internal fixation. Methods One of adult male complete dentition was chosen, and then using Frankfort horizonal plane as benchmark , CT scanning was done from condylar process to mental region,73 lamella in all.Using Photoshop 7.0 analysis bone tissue window fault, and coordinate value was load into Solid Works 2002 definite software ,then in a three-dimensional computer model of mandible, fracture mobility and plate strain were calculated for bite forces applied on incisors, fracture side and non-fracture side first molars. Simulated mandibular body and symphysis fractures were rigid internal fixed with two titanium miniplates. Fracture without interfragmentary contact were study. The loads were transmitted only through the plates and none stress was transmitted through the fracture surfaces. This computer-based study with finite element analysis (FEA) was done to estimate the stability of tention band fixation of mandibular fractures. Results With two miniplates, the symphysis and body fracture mobility were lower than 150 μm. To mandibular body fractures which had angle of more than 20 degrees with mesial surface, at both the incisors bite force and fracture molar force situation, the fracture mobility was also lower than 150 μm, but the fracture mobility above 150 μm was calculated at non-fracture molar bite forces. Conclusion From a mechanical point of view, based on the FEA model, two titanium miniplates are suitable for symphysis and body fractures. However two miniplates can not provide sufficient stabilizations for mandibular body fractures which have angle of more than 20 degrees with mesial surface . Suitable indications should be selected when miniplates are fixed mandibular angle fractures.

Key words: fracture fixation, internal, fracture fixation , stress, mechanical