Objective: Angle is a common site for mandibular fractures. Fractures of the mandible are classified as favorable and unfavorable depending on the fracture plane and muscles acting on these fragments. Mini-plate fixation on the oblique line according to biomechanics defined by Champy for both favorable and unfavorable fractures has become the standard treatment protocol. The purpose of this study was to compare the mechanical stress of mini plates and screws of horizontally favorable and unfavorable mandibular angle fractures and to determine whether one plate fixation maintains sufficient stability for even unfavorable angular fractures.

Materials and methods: A 3-dimensional finite element model of a mandible was constructed. Horizontally favorable and unfavorable fractures of mandibular angle area were simulated and fixed with 2.0-mm titanium conventional miniplate/screw system. The condyle and the genial area were fixed in all directions and a vertical 250 N bite force was applied from the molar area.

Results: In the favorable fracture the highest von Mises stress values was measured in the upper cortical layer of the fracture line and screws of the proximal segment. Screws in the distal segment showed less distribution of stress. In the unfavorable fracture the stress field spread over the screws and upper cortical layer of the distal segment was remarkable. The highest von Mises stress values was measured in the posterior screw of the distal segment.

Conclusion: It can be concluded that stress at the posterior screw of the distal segment of unfavorable fracture may cause screw loosening then failure of the fixation.

Conflict of interest: None declared.