Objective To evaluate the root canal retreatment efficacy either with or without the aid of a clinical operating microscope and ultrasonic instruments. Methods Thirty mandibular premolars with single root canal were prepared with ProTaper Universal rotary instruments and filled with lateral compaction technique in vitro. The filling material in root canal were retreated by ProTaper Universal rotary retreatment systems. Images of the residual filling material in root cannal were taken and the percentage was caculated. Then, a clinical operating microscope and ultrasonic instruments were used to help cleaning the root canal further, the images of the residual filling material were taken and the percentage was caculated again. The cleaning efficacies of root canal before and after microscope and ultrasonic treatment were compared. Results Before and after microscope and ultrasonic treatment, the percentage of the residual filling material was 26% , 9% in buccal-lingual dimension; 21% , 7% in mesia-distal dimension. There was a significant difference about the root canal cleaning efficacies before and afer the microscope and ultrasonic treatment ( P＜0. 05 ). Conclusion Using dental operating microscope and ultrasonic tips is help for improving the retreatment efficacy.%目的 评价显微超声技术应用子根管再治疗中牙胶糊剂去除效果.方法 30颗下颌前磨牙,经ProTaper镍钛器械预备及牙胶糊剂侧方加压充填,保存2周.先用ProTaper镍钛再治疗器械去除根管内充填物,结束后拍摄数字化牙片(radiovisiography,RVG).再在根管显微镜下用根管超声锉继续去除根管内的残留物,治疗结束后再次拍摄RVG.分别计算颊舌侧及近远中侧根管壁充填物残留量的百分比,比较显微治疗前后管壁的清洁度.结果 ProTaper镍钛再治疗器械去除后管壁的残留物百分比颊舌侧为26％,配合显微超声治疗后为9％；近远中侧为21％,配合显微超声治疗后为7％；显微治疗前后颊舌侧及近远中侧管壁清洁度均有统计学意义上的改变(P＜0.05).结论 根管再治疗的牙胶去除过程中,显微超声技术有助于提高效率.
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