Area moments of inertia as a measure of the mandible stiffness of the implant patient.

It was hypothesized that the bending stiffness of the mandible is an important biomechanical parameter in implant dentistry. It was shown how this bending stiffness can be estimated by means of the principal area moments of inertia of the cortical and cancellous cross-sections as obtained by computed tomography, some image processing and subsequent calculation. It was found that the contribution of the cancellous bone to the bending stiffness is normally insignificant and that the principal area moments of inertia of the cortical cross-section show large variations, depending on the degree of resorption. It was furthermore found that the variations in the principal area moments of inertia of the cortical cross-section in one and the same potential implant patient were minor. Finally, in a three-dimensional finite element study, it was found that the peak bone stresses adjacent to implants, resulting from a standardized load at the distal end of an implant-supported bridge, were inversely related to the magnitude of the principal area moment of inertia about the horizontal axis of the cortical cross-section. It was concluded that the principal area moments of inertia of the cortical cross-section and the angulation of the principal axes of inertia might be useful as a quantitative characterization of the mandible stiffness in clinical research and perhaps also in clinical practice.