[Morphological changes of the mandibula with loss of the teeth--observation of the trabecular bone using micro-CT]

The jaw bones receive complicated forces not only through the muscles, but through the teeth directly. Therefore, it is thought that the morphology of the jaw bones are greatly effected by the oral conditions. In this paper, the morphological changes of the mandibula with loss of the teeth are descrived. Furthermore, the three dimensional changes of the trabecular bones observed by micro-CT are shown. The jaw bones are of complex composition since they contain the alveolar sockets that encase the dental roots. The structures of the trabecular bone of the mandibula are constructed in order to support the teeth. The trabecular bones appear to have plate-like shape rather than rod-like shape in the three dimensional observation using micro-CT. With loss of the teeth, the height of the mandibula is rapidly shortened. And in the internal structures, both width and volume of the trabecular bone within the substantia spongiosa are reduced and the trabecular bones run in the irregular course. In addition, the plate-like shaped trabecular bones tend to transform into rod-like shaped ones. Based on these findings, it is suggested that maintenance of the intact teeth is important to keep the normal morphology of the mandibula.