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目的    探讨多次黏结对金属托槽槽沟及其滑动摩擦力的影响。方法    本研究于2004年9月至2006年3月在福建医科大学附属口腔医院及福州大学测试中心进行。选择因正畸治疗拔除的上颌双尖牙40颗，MBTTM迷你直丝弓托槽10个，采用高温灼烧后电解抛光的方法处理脱落的金属托槽，对托槽进行多次黏结。扫描电镜下观察槽沟底金属表面结构的变化，并检测托槽宽度和槽沟宽度。应用三角函数的原理推算出托槽弓丝接触角 θc的公式，分别计算出多次黏结前后托槽指数、入槽指数及θc的变化。结果    随着黏结次数的增加，槽沟底金属表面结构愈显粗糙；托槽宽度逐渐减小，与首次黏结相比，第二次黏结的变化无统计学意义（P > 0.05），第三、第四次黏结的变化具有统计学意义（P < 0.01）。随着黏结次数的增加，槽沟宽度、θc均依次增大，托槽入槽指数、托槽指数显著减小，与首次黏结相比，各组差异均有统计学意义（P < 0.01）。结论    入槽指数的减小虽然有利于缓解滑动阻力，但多次黏结会引起金属托槽槽沟表面粗糙、托槽弓丝接触角θc增大，均有可能导致槽沟滑动摩擦力增加，因此，在正畸临床矫治过程中对托槽的多次黏结应慎重。而托槽指数的变化对托槽与弓丝间滑动摩擦力的影响还有待于进一步的研究。

The influence of multiple bonding on the bracket slot and its sliding friction

Objective To discuss the changes of the slot size and its related indexes and their influence on the slot＇ sliding friction during multiple bonding.Methods Forty recently extracted human upper premolars were chosen.Ten brackets were bonded to these teeth;the brackets were then reconditioned three times by thermal process and electropolishing.Use SEM before and after multiple bondings to observe the change of the bracket base and the slot size,then the bracket index,the bracket engage index and the critical contact angle were tested.Results The base of the slot became more coarse;the slot size became wider,the bracket width became shorter,the bracket index and the bracket engage index decreased greatly,and the critical contact angle increased significantly（P 0.01）.Conclusion During multiple bonding,the wearing of the slot base and the augmentation of the critical contact angle,which is due to the electropolishing,has disadvantages during the sliding between the bracket and archwire.