An experimental study on histopathological changes of alveolar bone around hydroxyapatite during orthodontic tooth movement.

目前尚不清楚在使用不可生物降解的羟基磷灰石(HAP)进行骨移植的情况下，M.TM.是否可以接受。因此，我们观察了正畸牙移动过程中HAP间的骨组织学变化。将羟基磷灰石(HAP)植入Beagie犬第二前磨牙附近的人工骨缺损处，不植入任何材料作为对照。种植3个月后，第二前磨牙在正畸力的作用下移动。然后进行组织病理学观察。实验结果如下：种植部位的牙齿移动量小于对照组。在压力区：在种植区和对照部位均可观察到破骨细胞的骨吸收，此外，牙根吸收发生在HAP附近。进一步突变的巨细胞紧密附着在HAP周围的骨和结缔组织。在保留期内，HAP周围的牙根与骨之间有强直。在张力区：观察到来自HAP的额外的骨。骨缺损处充填了骨组织，而对照组为结缔组织。这一结果表明，HAP之间的骨是由破骨细胞溶解的。临床上应避免在压力区植入羟基磷灰石，以免发生牙根吸收和关节僵硬。但对于张力区，植入羟基磷灰石似乎是有效的，因为它能产生更多的修复骨。

It the been unclear whether M.T.M. is acceptable in the cases treated with bone graft using hydroxyapatite(HAP), which is not bio-degradable. So we examined histological changes of bone among HAP during orthodontic tooth movement. HAP was implanted into artificial bone defects adjacent to second premolars in beagie dogs, and as control no materials was implanted into them. Three months after implantation, the second premolars were moved with orthodontic force. Then they were observed histopathologically. The results obtained were as follows.Amount of movements of the teeth in implanted sites were smaller than control. At pressure zone : Resorptions of bone by osteoclasts were observed both in implanted and control sites, in addition, root resorptions occured adjacently to HAP. Further mutinucleated giant cells closely attached to HAP surrounded by bone and connective tissue. In retention period there was ankylosis between roots and bone around HAP. At tension zone : additional bone from HAP was observed. Bone defects were filled with bone in implanted sites, on the other hand, with connective tissue in control.These results suggested that bone among HAP was resolved by osteoclasts. Clinically, HAP implantation for pressure zone should be avoided because of the occurence of root resorption and ankylosis. But for tension zone it seems to be effective because HAP implantation produces more repaired bone.