Structural changes of the jaw bones with growth, aging and loss of the teeth - Three-dimensional reconstruction using micro-CT -

颌骨不仅通过肌肉，而且直接通过牙齿接受复杂的力。因此，人们认为颌骨的形态受口腔状况的影响很大。研究骨内部结构的传统方法是将标本埋入树脂后进行连续切片。然而，这种方法包含了一些问题，如试样的破坏和结构的单向观察。在本研究中，我们观察了下颌牙齿脱落后的形态学变化。此外，还显示了显微ct观察到的骨小梁三维变化。颌骨是由复杂的成分组成的，因为它们由包含牙根的牙槽窝组成。下颌骨的骨小梁结构是用来支撑牙齿的。显微ct三维观察发现，骨小梁呈板状而非杆状。随着牙齿的脱落，下颌骨的高度迅速缩短。而在内部结构中，海绵质的骨小梁的宽度和体积都缩小了，骨小梁的方向也发生了不规则的运动。此外，有板状小梁骨向棒状小梁骨转变的趋势。基于这些发现，我们认为维持完整的牙齿对保持下颌骨的正常形态至关重要。

The jaw bones are received the 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. A traditional method to study the internal structure of the bone is to make serial sections after embedding the specimen in the resin. This method, however, contains a couple of problems such as the destruction of the specimen and one way observaion of the structure. In this study, the morphological changes of the mandibula with loss of the teeth are observed. Furthermore, the three dimensional changes of the trabecular bones observed by micro-CT are shown.The jaw bones are made of a complex composition since they consist of the alveolar sockets to contain the dental roots. The trabecular bone structures of the mandibula are constructed in order to support the teeth. It is observed that the trabecular bones appeared to 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 direction of trabecular bone is making the irregular course. In addition, it has a tendency that plate-like shaped trabecular bones change into rod-like shaped ones.Based on these findings, it is suggested that maintenance of the intact teethis important to keep the normal morphology of the mandibula.