Bone histomorphometric study of alveolar bone resorption and formation and root resorption on experimetal tooth movement of rats.

点击翻译按钮获取中文摘要

1. The purpose of the first study was to investigate the effect of local application of 1, 25 (OH)_2D_3 on osteoclast number induced by experimental tooth movement. A piece of orthodontic elastic band was inserted between the first and the second upper molars of Wistar male rats weighing 200 g. 20 mol of 1, 25 (OH)_2D_3 (10^<-12> -10^<-7> M)was injected locally in the submucosal palatal area of the root bifarcation of the right first molar. The left side was injected with phosphate-buffered sahne (PBS). The number of osteoclasts was counted in a 700x1050mum^2 area of the inter-radicular septum. The local injection ofl, 25 (OH)_2D_3 caused a dose-dependent increase in osteoclast number. The effect of 1, 25 (OH)_2D_3 appeared at 10^<-12>M and reached a response plateau at 10^<-10>M when greater than a 3-fold rise in osteocla number was attained compared with the PBS-treated controls. While the insertion of a pace of elastic band for three days induced a significant increase in the appear … More ance of osteoclasts in the alveolar bone, daily injections of 20 mul of 10^<-10>M 1, 25 (OH)_2D_3 for 3 days markedly stimulated the appearance of osteoclasts induced by inserting an elastic band. 1, 25 (OH)_2D_3 was synergistic with mechanical stimuli resulting in enhancement of the appearance of osteoclasts induced by mechanical stimuli alone. These findings suggested that the local application of 1, 25 (OH)_2D_3 acts directly to increase in osteoclast number and synergistically to stimulate osteoclastic bone resorption induced by mechanical stimuh.2. The purpose of the second study was to compare the amount and rate of tooth movement in young and mature rats administered 1, 25 (OH)_2D_3 simultaneous with application of mechanical force. In thirty 7-week-old and thirty 28-week-old male Wistar rats, the right maxillary first molar was moved buccally with a fixed appliance. The appliances delivered forces ranging from 5 to 20 g. Twenty ml of 1, 25 (OH)_2D_3 (10^<-10> and 10^<-8> mol/L)was injected locally in the submucosal palatal area of the root bifurcation of the right first molar. Ile left side was injected with phosphate-buffered saline (PBS). In young growing rats receiving 10-10 mol/L 1, 25 (OH)_2D_3 every three days, tooth movement significantly increased to 126% of that in PBS-injected control rats on day 20. In 1, 25 (OH)_2D_3-injected mature rats, tooth movement was stimulated markedly and increased with 10^<-10> mol/L to 245% and with 10^<-8> mol/L to 154% of the amount of tooth movement seen in the PBS-injected controls by the end of the experiment. PBS-injected rats had a plateau stage where tooth movement did not occur at all, while there was no such lag-time in the 1, 25 (OH)_2D_3-injected group which showed continuous tooth movement. The local injection of 1, 25 (OH)_2D_3 did not change serum calcium, phosphate and alkaline phosphatase activity and there were no apparent clinical or microscopic side-effects. Less