Evaluation of stress distribution in different fixation techniques following bilateral sagittal split osteotomy: three-dimensional finite element analysis

BACKGROUND: The choice of fixation technique following bilateral sagittal split osteotomy (BSSO) plays a critical role in postoperative stability and biomechanical performance. Despite extensive research, the influence of varying mandibular advancement magnitudes and physiologic muscle forces on stress distribution remains insufficiently explored. PURPOSE: This study aimed to compare stress distribution patterns and mechanical behavior of two commonly used fixation systems-miniplates (MPs) and bicortical screws (BCSs)-under different mandibular advancement conditions using three-dimensional finite element analysis (FEA). STUDY DESIGN, SETTING, SAMPLE: This was a computational in vitro study using three-dimensional FEA based on a patient-specific mandibular model reconstructed from computed tomography data of a 30-year-old male. Simulations were performed to evaluate BSSO under two advancement conditions (3 mm and 9 mm) using different fixation techniques (MPs and BCSs). RESULTS: At 3 mm advancement, MP fixation demonstrated lower stress concentrations in the bone adjacent to screws (242 MPa vs. 270 MPa) but higher stress in teeth and greater displacement compared to BCSs. Conversely, at 9 mm advancement, BCS fixation resulted in higher stress values in teeth, bone, and screws. At the same time, MPs exhibited more favorable stress distribution but increased localized stress around screw-bone interfaces. In all models, stress concentration was predominantly observed in the proximal segment near the vertical osteotomy line. Increasing the advancement magnitude significantly elevated stress levels across all components. CONCLUSIONS: The fixation method and the magnitude of advancement significantly influence stress distribution following BSSO. Findings suggest that MPs may provide a favorable stress distribution with smaller advancements, whereas BCSs may offer biomechanical advantages with larger advancements. However, further experimental and clinical validation is required before definitive clinical recommendations can be made.