Biomechanical research on junction system of bone with biomaterials.

Regarding the junction of bioceramics with original bone, which have quite different material constants of Young's modulus and Poisson's ratio from each other, synostosis (ankylosis) cannot be obtained under severe loading conditions. Therefore, it is necessary to introduce a new junction system for the interface between the biomaterial mechanical organ and original bone. The jointing system of dental root to jawbone reflects on the function against mastication. The interface between different mechanical organs with different materials necessitates a specific juncture system under severe loading because of the disparity of material constants. The authors already reported the result of studies on the shape effect of artificial roots in functioning jawbone by means of finite element analysis. Studies on the functional effect of artificial roots in undulated shape were carried out biomechanically by means of finite element analysis using models to investigate an effective juncture system between bone and biomaterials. The results of finite element analysis were compared with the findings obtained from histological specimens. To observe the juncture state of bioceramics with tubular bone cortex, tubular apatite artificial bone was implanted in the femur of a dog. From these studies, the following results and conclusions were obtained: (a) The fibrous juncture system around bioceramics has an important role, after which the principal stress trajectories are converted; and (b) optimal undulated morphology compatible to the artificial bone's juncture system by means of fibrous ligament is essential for remodeling of the bone around the artificial skeletal bone.