Three-dimensional finite element assessment of grid-type plate in two different designs of sagittal split osteotomy of the mandibular ramus

Objective To evaluate stress distribution in the grid plate–screw system and cortical bone in two sagittal split ramus osteotomy (SSRO) designs, with linear advancements of 5.0 mm and 7.0 mm, using finite element analysis. Study design A three-dimensional mandibular model was reconstructed from CT scan and processed into finite element meshes. Grid plates with four monocortical screws were virtually positioned in the tension zone. Two osteotomy designs were tested: conventional Epker technique (Group I) and short split technique (Group II). Each design underwent advancements of 5.0 mm (a) and 7.0 mm (b). Masticatory muscle forces and occlusal loads were applied, and stress distribution in plates, screws, and cortical bone were analyzed using the Von Mises criterion. Results Greater mandibular advancement produced higher stresses in bone and fixation components. Group IIa demonstrated the lowest stress values, whereas Group IIb showed the highest peaks, particularly on plates and screws. Group I exhibited intermediate values with less disparity between 5.0-mm and 7.0-mm movements. Stress concentration increased proportionally with advancement. Conclusion The short osteotomy design provided favorable stress distribution for 5.0-mm advancements but reached critical stress levels at 7.0 mm, suggesting limited reliability for larger movements. Grid plates appear safe for smaller advancements in SSRO.