Finite-element-analysis of different screw-diameters in the sagittal split osteotomy of the mandible.

A three dimensional finite element model of the mandible was developed to simulate and study the biomechanical loads of osteosynthesis screws in bilateral sagittal osteotomy. Using the finite-element method clinical conditions were simulated. Different bicortical screw configurations and diameters were evaluated. When bite forces were applied, the most stable configuration was found to be a triangular one. This confirms the results found in the literature. A mini screw of 2.0 mm diameter can provide sufficient stability at the osteotomy site after ramus split osteotomy. Even screws with a diameter of 1.5 mm would withstand forces up to 89.5 N, which would not normally be reached by patients after ramus split osteotomy in the early period of healing. Forces exerted by patients after bilateral ramus split osteotomy do not exceed these values. The finite-element analysis appears to be an adequate method to evaluate this clinical question of interest. It might well replace mechanical models and the results are comparable with those reported in the International literature.