邻牙向拔牙区移动最佳时机选择的实验研究

目的　研究拔牙创愈合的生理过程和牙齿向拔牙区移动的生物学反应,探讨邻牙向拔牙区移动的最佳时机。方法　30只同源雄性SD大鼠分为5组,拔除上颌第一磨牙,在拔牙后不同的时间制作口内矫治器,牵第二磨牙向拔牙区移动。所有的大鼠分别在矫治器加力前两天和处死前两天给予四环素和钙黄绿素腹腔注射;制备硬组织切片,采用骨硬组织形态测量和计算机图像处理技术,对向处于不同愈合阶段的拔牙区移动牙齿时的骨改建参数进行定量分析。结果　①骨改建同时包括吸收和形成两个过程;②近中牙槽骨面(压力侧)骨吸收较远中 (张力侧)活跃,而远中牙槽骨面(张力侧)骨形成则较近中(压力侧)活跃;③骨形成参数、骨吸收参数均在拔牙后1 周存在一个峰值。结论　①拔牙后宜早期移动牙齿,以便充分利用拔牙创的骨改建优势;②其理想的移动时机为拔牙后1周左右。

Experimental Study on Selecting Optimal Time of Orthodontic Tooth Movement into Extraction Sites

OBJECTIVE: The purpose of this study was to investigate the physiological process of healing after tooth extraction and the biological reaction of tooth movement into extraction sites with the aim of selecting optimal time of tooth movement into extraction sites clinically. METHODS: Extraction of upper first molars were performed on 30 male Sprague-Dawley rats which were divided equally into 5 groups. Orthodontic appliance was placed at different time after tooth extraction in order to move the maxillary second molars mesially into the extraction spaces. The animals were injected continuously with tetracycline and calcein for two days before appliance activation and animal sacrifice. Undecalcified mesio-distal specimans 65-100 microns of thickness were prepared. The quantification of bone remodeling parameters on tooth movement into extraction sites at different time was performed by histomorphometric measurements and computer image analysis. RESULTS: 1. The bone turnover had two bone modeling processes: resorption under pressure and formation in tension. 2. The bone resorption was more active on the mesial surface (pressure side) than that on the distal surface (tension side). While bone formation was more active on the distal surface (tension side) than that on the mesial surface (pressure side). 3. Both the resorptive parameters and the formative parameters across time were manifested by a peak at day 7 after tooth extraction. CONCLUSION: 1. Orthodontic retraction into extraction sites should be initiated at an early stage after tooth extraction, so that the advantage of bone remodeling in extraction sites was used. 2. The optimal time of tooth movement into extraction sites clinically was about a week after tooth extraction.