中文摘要：

目的探讨根管弯曲度和器械分离位置对根管内分离器械取出的影响。方法选取60颗离体人下颌前磨牙,建立根管内不锈钢K型锉分离模型。根据器械分离于根管口下的深度（2、8 mm）和分离角度（20°、30°、40°）分为6组,每组10颗。采用超声法取出分离的K型锉,记录K型锉的取出数和操作时间,使用图像分析软件将术前术后拍摄的数码X线片重叠,测量分离器械取出前后K型锉冠端处根管直径的变化值。结果 6组不锈钢K型锉全部取出,未发生侧穿。分离位置一定时,随着弯曲度的增大,取出分离K型锉时冠端处横向牙本质切削量增大,差异有统计学意义（P〈0.05）,取出时间无明显变化（P〉0.05）;而弯曲度一定时,随着分离深度的增加,取出时间明显增加（P〈0.05）,分离K型锉冠端处横向牙本质切削量无明显变化（P〉0.05）。结论根管弯曲度越大,分离器械冠端处横向牙本质切削量越大;分离位置是影响分离器械取出的重要因素,但并不影响分离器械冠端处横向根管壁的牙本质切削量。安全有效的直线通路和足够的牙本质厚度是成功取出根管内分离器械的必要条件。

英文摘要：

Objective To evaluate effect of root canal curvature and location of the fragment on the removal of broken file from root canal.Methods Sixty extracted mandibular premolars were divided equally into six groups according to location of fragment（2 mm or 8 mm below root canal orifice） and root canal curvature（20°,30° or 40°）. Broken files were removed using ultrasonic tips combined with dental operating microscope.Number of successfully removed case and operating time were recorded.Pre-and post-operative digital radiographs were input into image analyzing software to calculate diameter variance of root canal at the level of tip of broken file.Results All the 6 groups of broken files were successfully removed with out perforation.Among same fragment location groups,diameter variance was increased in greater curvature groups and the difference was significant（P0.05）,while operation time was not significantly different（P0.05）.Among same root canal curvature groups,the deeper the fragment,the longer operation time,difference being significant（P0.05）,while difference of diameter variance was not significant（P0.05）.Conclusion The more curvature of root canal,the more dentine removal amount at the level of broken file tip.Location of fragment has no effect on dentine removal amount.Safe straight-line access and adequate thickness of dentine are essential to removal of broken file from root canal.