[Structure of jaw bone].

The jaw bone is put in a special environmental condition because it receives not only external force through a masticatory muscle, but occlusal force directly from the teeth. Therefore, the morphology and internal structure of the jaw bone is strongly reflected by the erupted condition of the teeth. In the edentulous jaw bone, the number and thickness of the trabecular bones is reduced as well as decrease of its size. This tendency is quite resemble to the morphological change of osteoporosis. Based on the facts mentioned above, it is suggested that the loss of the teeth induces the fragility of the jaw bone. Therefore, maintenance of a healthy tooth is very important to keep the normal morphology of the jaw bone.