Analysis of Stress Distribution on Fixation of Bilateral Sagittal Split Ramus Osteotomy With Resorbable Plates and Screws Using the Finite-Element Method

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.