Three-dimensional finite element analysis used to compare methods of fixation after sagittal split ramus osteotomy: setback surgery-posterior loading.

We used three-dimensional finite element analysis to compare the biomechanical stability of bilateral sagittal split ramus osteotomies fixed by lag screws with linear and triangular configuration, and double or single six-hole miniplates with monocortical screws after set-back operation. The three-dimensional finite element model contained 122,717 elements and 25,048 nodes. Posterior occlusal loads were simulated on the distal segments. MSC Marc software was used to calculate the stress fields on both the segments and the fixing appliances. We conclude that either triangular lag screw configuration or double miniplates led to better stability and lower mechanical stresses near the osteotomy than the linear lag screws or single oblique miniplates.