Modeling of jaw biomechanics in the reconstructed mandibulectomy patient

Statement of problem. Biomechanics of occlusal force and indirect calculati on of temporomandibular joint loading in patients after surgery for head an d neck cancer is poorly understood. Purpose. This study compared occlusal force values of 6 mandibulectomy subj ects with reconstructed mandibles to 6 noncancer subjects with intact mandi bles and reports occlusal force predictions from a developed computer model simulation of both a mandibulectomy subject with a reconstructed mandible and noncancer subject with an intact mandible. Material and methods. Maximum occlusal force was recorded at the first mola r and incisal edge in 6 mandibulectomy subjects who had bony reconstruction of the mandible and 6 noncancer subjects with an intact mandible. Clinical data were then qualitatively compared with occlusal force values generated from an existing computer model simulating an average adult, and a develop ed model simulating an average mandibulectomy subject who had bony reconstr uction of the mandible. The biomechanical parameters modeled also included an estimation of joint force magnitude and direction when biting with maxim al force on the first molar. Results. Clinical data revealed no significant differences in occlusal forc e between the 6 mandibulectomy subjects with bony reconstruction of the man dible and 6 noncancer subjects with an intact mandible; however, average mo lar and incisal occlusal force values were 22% and 32% less in mandibulecto my subjects with bony reconstruction Computer simulations of a reconstructe d mandibulectomy subject predicted that reconstructed subjects would have 4 5% less molar occlusal force, 50% less incisal occlusal force, and a higher joint/tooth force ratio compared with a simulated noncancer patient with a n intact mandible. Conclusions. There were no significant differences in first molar or incisa l occlusal force between reconstructed mandibulectomy subjects and noncance r subjects with intact mandibles. Trends calculated from computer simulatio ns were consistent with clinical findings.