applied to the mini-implants for four months, the mini-implant was recorded as successfulanchorage. After immediate loading for four months, the analyses were completed by SPSS 9.0 software. Results  Of the 306 inserted mini-implants, 162 were absolutely separated from PDL, 136 appeared to touch or overlay on PDL,but not contact to the adjacent roots, and 8 were excluded from this study because of injury to the adjacent root. The success rates of group Ⅰ and Ⅱ were 87.0% and 65.4% respectively. There were significant differences in the success rates between the two groups（P<0.001）. The differences between the two groups in distribution of the upper right and left area had statistical significance（P<0.05）. Conclusion  PDL injury is one of the main reasons leading to early loosening of the mini-implant.

[Key words]  mini-implant； periodontal ligament； initial stability； immediately loading

近年来微型镍钛种植体作为支抗在正畸医治中普遍使用[1-4]。作为一种新型的相对支抗安装，它具有手术操作简单、创伤小、本钱低、医治完毕后容易去除、等候骨整合和骨愈合时间短[5]、不依赖患者配合等优点。虽然如此，微型种植体支抗较高的失败率仍限制其在临床上的进一步开展与普及[6]。Park等[7]曾报道种植体支抗的失败率高达9.4%～20.0%。而种植体的松动零落是其失败的主要临床表现。招致微型种植体松动零落的要素很多，曾有学者经过动物实验对微型种植体植入时损伤牙根而招致微型种植体松动零落进行研讨[8-9]，但关于微型种植体仅碰触牙周膜而不损伤牙根能否与微型种植体的初期松动具有相关性却少有报道。本研讨使用三维CT手腕，主要对临床上即刻加载条件下微型种植体碰触牙周膜与微型种植体初期波动性的关系进行研讨。

1  资料和办法

1.1  研讨对象的选择

选取山东大学

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