拔牙区骨改建对邻牙移动速度的影响

Influence of Bone Remodeling in Extraction Sites on Tooth Movement

目的 本研究通过对拔牙创的骨改建进程及矫治力对牙齿移动的影响进行研究 ,为临床医生选择理想的矫治力和牙齿移动时机 ,缩短矫治时间提供依据。方法 取SD大鼠 36只 ,随机分为 3组 ,全麻下拔除一侧上颌第一磨牙 ,3月后拔除另一侧上颌第一磨牙。在拔牙后不同的时间制作口内矫治器 ,分别以 0 30、0 6 0、1 36N的力牵上颌第二磨牙向拔牙区移动 ,分别在施力前及施力后的第 1、3、5、7、10、14天拍摄X线片 ,利用图像处理技术 ,测量牙齿移动距离 ,以置入的拔髓针校正放大率。结果 ①牙齿向新鲜拔牙区移动的速度明显大于向已愈合拔牙区移动的速度。②无论向新鲜拔牙区移动还是向已经愈合的拔牙区移动 ,0 30N力组牙齿移动的距离在各时间点与 0 6 0N、1 36N力组牙齿移动的距离之间存在显著的统计学差异 ;而 0 6 0N与 1 36N力组牙齿移动的距离之间基本上从第 5天开始差别不大。③加力后牙齿移动周期一般包括三个阶段 :瞬时运动 ;迟滞期 ;后期移动阶段。大约在第 14天时 ,由于矫治力衰减 ,牙齿停止移动。结论 ①牙齿向新鲜拔牙区移动速度快 ,而向已经愈合的拔牙区移动速度慢。②在矫治过程中 ,中等力较为合适 ;即使使用较大的力 ,也不一定引起较大的牙齿移动。

Objective To investigate the influence of bone remodeling in extraction sites and orthodontic forces on tooth movement with the aim of providing a basis for selecting optimal orthodontic forces, time of tooth movement and reducing the time for tooth moving into extraction sites.Methods Extraction of upper first molars were performed on 36 male Sprague-Dawley rats which were divided equally into 3 groups. A method for quantification of orthodontic tooth movement in the rats was presented. Orthodontic appliance was placed at different time after tooth extraction. Different forces were used to move the maxillary second molars mesially into the extraction spaces. X-ray was taken before appliance activation and after 1, 3, 5, 7, 10, 14 days since appliance activation. Tooth movement was measured cephalometrically by Imagine Analysis Technique, adjusting for magnification by using the known digitized length of the broach.Results ①The tooth on the recent extraction side moved faster than that on the healed side.②Tooth movement at all time points on the 0.30 N curve differed from those on the higher force curves (P<0.01), either moving into recent extraction sites or healing sites. Comparison between 0.60 N and 1.36 N indicated that mesial molar movement did not differ from each other after day 5. ③ The classical tooth movement curve had three parts that represent distinctly different processes: early movement;delay;later movement.Conclusion ① The tooth on the recent extraction side moved faster than that on the healed side.② Moderate force maybe was the optimal orthodontic force. It could be overloaded, but resulted in no further enhancement of tooth movement.