[摘要]目的研究不同的超声功率对体外根尖倒预备的影响。方法58颗体外牙常规根管预备、冲洗以及热牙胶充填后，沿垂直牙体长轴方向切除根尖3 mm，将其随机分为3个试验组和1个对照组。试验组分别采用高、中、低3种功率进行超声倒预备，深度3 mm，对照组不做倒预备。扫描电子显微镜下观察根尖断面微裂、边缘完整性和牙胶清除率，记录操作时间。结果高功率组的微裂数量和范围明显多于中、低功率组，边缘完整性则低于中、低功率组，低功率组的牙胶清除率明显低于中、高功率组。功率越大，其操作时间越短。结论在中等功率下进行超声倒预备，微裂少，破坏性小，牙胶清除相对彻底，用时也较短。

    [关键词]超声功率；倒预备；扫描电子显微镜；根尖手术

    [中图分类号]R 781.05[文献标志码]A[doi]10.3969/j.issn.1673-5749.2012.01.002

    Effects of ultrasonic power on root-end preparationLiu Xiaobin, Li Guihong.(Dept. of Conservative Den-tistry and Endodontics, Tianjin Stomatological Hospital, Tianjin 300041, China)

    [Abstract]ObjectiveTo evaluate the effects of ultrasonic power on root-end preparation. Methods58 teeth were root canal prepared and filled, 3 mm of the root-end was cut off along the vertical direction of the long axis of the tooth. The samples were divided randomly into 3 experimental groups and 1 control group. In the experi-mental groups, root-ends were prepared with high, middle, and low 3 different ultrasonic power. The control group was not prepared. Microcracks, marginal integrity, and gutta-percha clearance rate were observed under scanning electron microscope, and recorded the operation time. ResultsNumber of microcracks and destroy of marginal integrity were much more under high power. Low power took the minimal gutta-percha clearance rate. The greater power took the shorter operation time. ConclusionUnder moderate ultrasonic power, the number of microcracks and destroy of marginal integrity were much small, clearance rate of gutta-percha were higher, and also took short operation time. ......