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目的    探讨上颌第一磨牙近中颊根第二根管（MB2）的寻找与扩通方法。方法    将2006—2008年于沈阳市口腔医院口内门诊就诊患者的因牙髓炎需要做根管治疗的上颌第一磨牙84颗，随机分成试验组（42颗）、对照组（42颗）。试验组根管显微镜下寻找MB2并扩通，而对照组常规裸眼下进行操作，比较分析两组MB2的发现率及通畅率。结果    试验组上颌第一磨牙MB2发现率、通畅率分别为80.95% 、82.35% ，对照组上颌第一磨牙MB2发现率、通畅率分别为42.86% 、77.78%，两组上颌第一磨牙MB2发现率比较，差异有统计学意义（P < 0.05），通畅率比较差异无统计学意义（P > 0.05） 。结论    在对上颌第一磨牙进行根管治疗时，用根管显微镜寻找MB2的比例远大于临床用裸眼下操作。

Clinical observation on location and diation of the second mesiobuccal canals in the first maxillary molars

Objective To study the ways of the location and dilation of the second mesiobuccal canals in the first maxillary molars. Methods A total of 84 first maxillary molars from patients aged 18 to 40 who needed to receive root canal therapy due to pulpitis were randomly diveded into two groups：the experiment group （42 teeth） and the control group （42 teeth）. MB2 was located and dilated under a microscope in the root canals of the experiment group, while MB2 was located and dilated with naked eyes in the control group. Compare and analyze the rate of location and dilation between the two groups. Results The rate of location and dilation of MB2 of the first maxillary molars was 80.95% and 82.35%, respectively, in the experiment group, which was 42.86% and 77.78% in the control group. The location rate had statistical difference（P 〈 0.05） ,while the dilation rate didn＇t（P 〉 0. 05）. Conclusion In the root canal therapy for the first maxillary molars, the location rate of MB2 under microscopes is much better than with naked eyes.