正畸治疗导致牙根外吸收的临床分析

目的：调查正畸治疗导致牙根外吸收的发病情况，分析其临床特征及相关因素。方法：随机选择经直丝弓矫治技术完成的病例230例，以Levander根吸收分级法对患者全颌曲面断层片进行分析，评估矫治前后中切牙至第一磨牙的根吸收情况。结果：正畸治疗后根吸收发生率明显升高，根吸收均值（root resorption after treatment，RRAT）及根吸收增加量均值（increment of root resorption，IRR）表现为上切牙最高，拔牙组高于未拔牙组，异常根形态组高于正常根形态组。结论：正畸治疗可提高根吸收发生几率，并加重根吸收程度，此可能与拔牙与否、牙位、根形态及治疗前牙根吸收程度有关。

A clinical investigation of orthodontically induced external apical root resorption

Objective:To investigate the frequence of external apical root resorption(EARR)in relation to orthodontic treatment. Method:230 cases treated with straight wire appliance were randomly selected. Pretreatment and posttreatment panoramic radiographs of those patients were examined to assess changes in root length and apical contour according to criteria modified from Levander et al. Result:The prevalence of EARR rose significantly after treatment. There were statistically significant differences in the preval...