Evaluation of the fracture formation pattern of trauma to the symphysis of the mandible after marginal mandibular resection by finite element analysis

Marginal resection of the mandible (MMR) is a proven mandibulectomy technique for the treatment of a range of malignant and benign lesions. After MMR, mandibular fracture remains an unsolved problem. Many studies have been conducted to evaluate the mechanism of fracture formation. The aim of this study was to quantify the resistance of the marginal mandibulectomy size to mandibular fracture in the face of trauma, to improve the use of this technique and to establish a threshold for prophylactic internal fixation or grafting. Using the finite element analysis method, 13 different mandibular models were created in three-dimensional computerized models. MMRs were performed so that the mesiodistal diameters of these models were constant but increased vertically by 5 mm. These resections were performed with the mesiodistal border between the mesials of both 1st premolars in the symphysis and between the distal part of the right 1st premolar and the distal part of the right 2nd molar in the corpus. Marginal resections were performed: 7 in the symphysis and 6 in the corpus. A force of 1000 N was applied perpendicular to the symphysis of the mandible. In the study, von Mises, maximum principal and minimum principal stress values were evaluated. As a result of the study, the stresses in the last 4 models in the symphysis and the last 4 models in the corpus were found to have the potential for fracture. Residual height and trauma force are critical factors for pathologic fracture prevention. The minimum amount of bone that can withstand trauma was 18 mm or less for resection in the symphysis and 17 mm or less for resection in the corpus. If the remaining bone height after MMR is not higher than these values, internal fixation or bone grafting should be considered prophylactically to prevent fracture.