A total of seven human mandibles were struck to breaking point under standardised conditions using a pendulum. The cortical deformation for two impact directions was measured with strain gauge strips located at eight defined sites. Fronto-median impacts led to mostly bilateral and always multiple fractures in the posterior area of the bone, especially in the collum and the condyle. The fracture threshold was between 2.5 and 3.1 kN. Lateral impact caused fractures near the impact area as direct fractures of the ipsilateral corpus. Mainly single and double fractures were observed. For lateral impact the fracture threshold was between 0.6 and 0.8 kN.

Biomechanical investigations of the mandible are difficult to perform due to a variety of conditions involved. For the appropriate reconstruction of biomechanical properties, a geometrically correct body model has to be established which fits to complex in vivo conditions. The aim of our study was to evaluate the use of finite-element models (FEM) for the assessment of mandibular deformation under mechanical loading. Explanted human mandibles (n = 5) were investigated by strain gauges to determine the individual strain distribution under mechanical loading. FEM analysis based on a computed tomograph (CT) was performed and the results were matched with the test data. Our study demonstrates only minor interindividual differences in the strain distribution for each load studied. The mechanical response in terms of deformation was found to depend mainly on gross geometrical properties and to a minor extent on the various other variables. At all positions the maximum principal strain was tensile, the minimum principal strain was compressive, and the absolute strain values were correlated with the magnitude of the applied force. CT-based FEM analysis revealed the utility of mathematical models to approximate simulated data our experimental results. Hence, FEM analysis is a non-invasive tool in the prediction of biomechanical behaviour of individual mandibles and therefore may help in trauma reconstruction and treatment planning.

Our fracture and osteosynthesis model allows the quantitative determination of micromovements in the gap tissue and shows the importance of ideal realignment, which has a decisive influence on micromovements in the gap tissue.