Abstract

Purpose: To determine the most appropriate stress distribution in fixation with resorbable screws and plates after bilateral sagittal split ramus osteotomy using the finite-element method. Materials and Methods: This experimental study was performed on simulated human mandibles using computer software. The osteotomy line was applied to the simulated model and experimental loads of 75, 135, and 600 N were exerted on the model in accordance with the vector of occlusal force. The distribution pattern of stress was assessed and compared in 8 fixation methods: 1 resorbable screw, 2 resorbable screws in a vertical pattern, 2 resorbable screws in a horizontal pattern, 3 resorbable screws in an L pattern, 3 resorbable screws in a backward-L pattern, 1 miniplate with 2 screws, 1 miniplate with 4 screws, and 2 parallel miniplates with 4 screws each. Results: Among the simulated fixations, 2 parallel miniplates showed the greatest primary stability and the single screw and the 2-hole miniplate showed the least tolerance to posterior forces. Conclusions: This study showed the 2-miniplate/4-hole plate pattern was the strongest and the single-screw and 2-hole plate patterns were the weakest of fixations in this bilateral sagittal split ramus osteotomy model. The finite-element method showed that polymer-based resorbable screws and plates (polyglycolic acid and D, L-polylactide acid) provide satisfactory primary stability in this model. (C) 2012 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 70: 1434-1438, 2012