上颌第一磨牙遗漏近颊第二根管的显微根管再治疗

目的：探讨运用根管显微镜对经治的上颌第一磨牙遗漏近颊第二根管（MB2）的诊治方法。方法：选择需行根管再治疗的上颌第一磨牙64个。依据x线片特征，牙冠与髓底的形态特点判断是否存在MB2。采用斜方形开髓入口，小号K锉探查，必要时使用根管手术显微镜定位MB2根管。镍钛机用根管锉冠向下法预备根管，1％NaOCL冲洗根管系统，冷牙胶侧方加压与热牙胶垂直加压充填根管。记录近颊根根管分型、根管预备过程中并发症的情况，评价疗效。结果：再治疗中共发现MB2根管55个（85．81％），疏通45个（80％）。近颊根双根管以2—1型、2—2型较常见（76．56％）。治疗过程中未发生器械折断、管壁侧穿等并发症，治疗成功率为95．55％。结论：上颌第一磨牙MB2发生率高，通常狭窄、弯曲、隐蔽，是临床治疗的难点；临床医生有意识地寻找和在显微镜下的可视化操作能提高MB2根管的发现率和治疗的成功率。

Endodontic retreatment of untreated second mesiobuccal canals in treated maxillary first molars

Objective：To evaluate the clinical treatment of second mesiobuccal canals （MB2 canal） of maxilarry first molars missed in initial endodontic treatment using dental operating microscope （DOM）. Method： 64 maxillary first molars which need endodontic retreatment were selected. The existence of MB2 canal was determined by radiographs and anatomic features of crown and pulpal floor. With a thapezium path to pulp chamber, the MB2 canals were explored by a small size K file and located using a DOM when needed. The canals were instrumented by Ni-Ti rotary instruments, irrigated by 1% NaOCI and were obturated by lateral condensation and vertical compaction technique. The type of mesiobuccal root canals, the in-operative complications and the obturation effect were record. Result： The frequency of MB2 canal in maxillary first molar was 85.81% in endodontic retreatment while negotiate rate was 80%.2-1type and 2-2 type were the main type of mesiobuccal root canals （76.56%）. There were no obvious complications during operation. 95.55% MB2 canals were obturat- ed successfully. Conchusion：The incidence of MB2 canals in maxillary first molars was high. Most of MB2 canals were fine, curved and concealed. The managment of searching for MB2 canals and the increased visibility afforded with the use of DOM can make the treatment more successful.