Biomechanical analysis of the strength of the mandible after marginal resection

Abstract

Purpose: This study investigated the biomechanical behavior of the mandible after marginal resection by tensile test in a human cadaveric mandible and finite element (FE) analysis.

Materials and methods: Human cadaveric mandibular models after marginal resection were prepared with residual heights of 5, 10, and 15 mm. The strength in each of these mandibular models was examined by tensile testing. In addition, FE models of the mandible after marginal resection were prepared with residual heights of 5, 7.5, 10, 12.5, and 15 mm. Distribution and magnitude of von Mises stress were analyzed by applying bite forces of 151 N as a point load on the incisal region and 355.2 and 478.1 N on the premolar and molar regions on the nonresected and resected sides, respectively. At the molar region of the resected side, bite forces of 368.5 N and 286.9 N (80% and 60%, respectively, of 478.1 N) were also applied.

Results: On tensile testing, all cadaveric mandibular models were broken at the posterior resection corner. The tensile force was significantly larger in the model with a residual height of 15 mm compared with that of those with a 5- or 10-mm residual height. On FE analysis, von Mises stress was concentrated at the resection corner. The region of maximal von Mises stress concentration in FE models was consistent with that showing destruction on tensile testing. The relationship between the residual height and von Mises stress in the resection area was linear in models of the incisal, premolar, and molar loading on the nonresected side and quadratic in models of the premolar and molar loading on the resected side. The maximal von Mises stress in the resection area was highest during molar loading on the resected side under the present loading condition and exceeded the threshold for the development of pathologic fracture in the model with a residual height of around 10 mm or less. However, the maximal von Mises stress decreased in parallel with the reduction of bite force in the molar region of the resected side.

Conclusions: The residual height and bite force are critical factors for the prevention of pathologic fracture of the mandible after marginal resection. Currently, a residual height of more than 10 mm and reduction of bite force are recommended to reduce the risk of fracture.