Comparison of five different fixation techniques of sagittal split ramus osteotomy using three-dimensional finite elements analysis

The aim of this study was to compare the mechanical stress over hemimandible substrate and hardware after sagittal split ramus osteotomy (SSRO) fixed with five different techniques using three-dimensional (3D) finite element analysis. A 3D finite element model of a hemimandible was created and a 5 mm advancement SSRO was simulated on a computer model. The model was fixed with five different techniques: 3 linear 60 degrees screw arrangement; 3 linear 90 degrees screw arrangement; 3 inverted L screw arrangement; 1 conventional miniplate; and I locking miniplate with four monocortical screws. Load was applied until 3 mm displacement was reached and the results were compared with previous mechanical and photoelastic tests, thus analysing the mechanical stresses developed, in the proximity of miniplates and screws and within the fixation system itself. The maximum principal stress values demonstrate a lower mechanical stress rate in bone and in the fixation system with the inverted L arrangement, followed by the linear 90 degrees and linear 60 degrees arrangements. The locking miniplate/screw system presented lower maximum principal stress and better stress distribution compared with the conventional system. Under the conditions tested, the reversed L arrangement provided the most favourable stress dissipation behaviour.