In vitro biomechanical evaluation of fixation methods of sagittal split ramus osteotomy in mandibular setback.

The purpose of this study was to compare different internal fixation techniques with resorbable or titanium fixation system used in sagittal split ramus osteotomy (SSRO) for mandibular setback. Synthetic polyurethane hemimandible replicas were used. The distal segment was repositioned in a 5-mm setback position. The hemimandibles were divided into the following eight groups: resorbable miniplate (A), titanium miniplate (B), resorbable hybrid; resorbable miniplate and bicortical screw (C), titanium hybrid; titanium miniplate and bicortical screw (D), resorbable mixed hybrid; resorbable bicortical screw and titanium miniplate (E), titanium mixed hybrid; titanium bicortical screw and resorbable miniplate (F), three resorbable bicortical screws (G) and three titanium bicortical screws (H). The compression loads were applied on the incisal edge. The compression loads (N) at 5- and 10-mm displacement were analyzed (P < 0.05). Miniplate groups (A and B) were significantly weaker than the other groups (C approximately H). Group (H) had greatest biomechanical stability. There was no significant difference between group (D) and group (H) at 10-mm displacement. Group (G) showed a lower load than group (H) and group (D). There was no significant difference between the hybrid and mixed hybrid groups. It was concluded that additional placement of a bicortical screw, either titanium or resorbable with a miniplate may provide significantly better stabilization.