Reconstruction plates to bridge mandibular defects: a clinical and experimental investigation in bimomechanical aspects

A retrospective study of 68 patients was carried out to assess the cmomplications arising frmom the use of reconstruction plates in the maintainance of space and contour following mandibular segmental resection. Skin or mucosal perforation, plate fracture and loss of screw retention were the main cmomplications. The most susceptible sites to screw loosening in the plates were situated nearest to and farthest frmom the resection margin on the proximal residual segments. Smome of the possible causative bimomechanical mechanisms of plate failure were studied using photoelastic models simulating the types of mandibular defect and plate fixation. Isochrmomatic fringe analysis was used to analyse stress lines in the bone surrounding screws. It was found that, during functional loading, mmoment and shear forces produced high concentrations of squeeze and press stress in this bone, causing bone resorption with consequent loss of screw retention.