The effects of occlusion on single miniplate osteosyntheses of the mandible

Abstract

Aim: Miniplate osteosyntheses of a fractured mandible is a complex structural engineering problem that has been modeled experimentally, analytically and numerically. In general, the more realistic the model, the more difficult it is to appreciate its nuances. Thus, a purpose of this paper is to present a basic analytical model that illustrates the most fundamental principles of static equilibrium as it applies to the mechanics of single miniplate osteosynthesis designs. The second purpose is to use the model to demonstrate the effects of changes in occlusion on the loads experienced by the structures. Materials and methods: The 3 equations of static equilibrium were derived from the free-body-diagram of the distal segment of a vertically fractured reduced mandible. The equations were solved parametrically with variations in plate screw locations, anterior-posterior locations of occlusal contact, and occlusal contact force direction, including the simulation of sticky foods. Results: The results indicate a profound effect of occlusal contact force location and direction on the magnitudes and/or directions of the forces acting on the screw and the miniplate, and on the location and magnitude of the interfragmental bone-bone compression force. Conclusions: In some respects, this model is as barebones as is possible. Atypically however, it includes occlusal contact force direction. The results strongly suggest that all analyses of plating systems should account not only for occlusal contact force location and magnitude, but also its direction.