Quality assessment of the cortical bone of the human mandible.

This study is the first to investigate simultaneously both the regional and the directional variations in mechanical properties and computed tomography (CT) numbers of the fresh mandible bone and to explore the correlation between the two sets of data with a view to provide a noninvasive method for determining the bone quality for designers of dental implants. Using a three-point bending test the regional variation of Young's modulus of bone in the human mandible was determined from five fresh specimens from donors representative of patients in need of dental implants in that some of the mandibles were fully dentulate, some partly so, and some fully edentulate. While a pattern of the modulus distribution was evident in the mandibles we tested, these mandibles did have, as a result of their respective states, their own peculiarities. We determined also the directional variations of the modulus for the mandible, which are due to the anisotropic nature of bone. The modulus values obtained in our study were much lower than those listed in the only other published study, which was conducted on dry mandibles. These differences in the modulus data from the two studies were attributed partly to the differences in condition of the bone and differences in the dimensions of specimens tested in the two studies. Because the values of the modulus obtained in this study are lower than those previously published, they would be safer as a basis for implant designs. A weak correlation was found between the modulus values and the CT number of the mandible. This would not be sufficient for accurate predictions of the bone properties from CT scans. The development of a noninvasive method for determining the bone quality in various patients thus remains a challenge for researchers.