与下颌管关系密切的下颌阻生第三磨牙流行病学特征分析

Analysis of epidemiological characteristics of impacted mandibular third molars next to inferior alveolar canal

目的研究与下颌管(inferior alveolar canal,IAC)关系密切的下颌阻生第三磨牙(impacted mandibular third molar,IMTM)的流行病学特征,为临床上评估IMTM拔除风险及制定手术方案提供参考。方法连续收集2015-01-01—2016-12-31在第四军医大学口腔医院口腔外科拔除IMTM患者的临床资料,从中选取经锥形束CT(cone-beam CT,CBCT)检查确定IMTM突入IAC或二者直接接触的患者,分析这些患者患牙的阻生类型及和IAC的空间结构关系。结果共纳入214例患者,304颗患牙。其中突入IAC者226颗(74.34%)、接触IAC者78颗(25.66%)。按照Pell&Gregory分类,2种类型均是中位阻生最多[分别为99颗(43.81%)和40颗(51.28%)];按照Winter′s分类,2种类型均是水平阻生最常见[分别为90颗(39.82%)和34颗(43.59%)];进一步分析患牙和IAC的空间位置关系发现,2种类型均是IAC位于IMTM根方者最多见[分别为118颗(52.21%)和63颗(80.77%)]。结论本研究明确了经CBCT证实的与IAC关系密切的IMTM的阻生类型及其和IAC的空间位置关系等特征,为缺乏CBCT检查时,临床制定IMTM拔除手术方案及如何预防下牙槽神经损伤提供了理论指导。

Objective To study the epidemiological characteristics of impacted mandibular third molar （IMTM） next to inferior alveolar canal （IAC）, and to guide the risk evaluation and the surgical procedure of IMTM extraction. Methods A retrospective analysis was made among the patients who underwent IMTM extraction in the Department of Oral Surgery, School of Stomatology, the Fourth Military Medical University since Jan. 1,2015 to Dec. 31,2016. Only the IMTMs next to IAC, which were confirmed by cone-beam computed tomography （CBCT）, were finally included. And then, the type of impaction and the relative position between IMTM and IAC were analyzed. Results Three hundred and four IM- TMs from 214 patients were included. Among which, 226 （74.34%） IMTMs protruded into IAC, while 78 （25.66%） IM- TMs contacted with IAC. According to the Pell ＆ Gregory classification, median impaction was the most common in both the protruding group [ 99 （43.81% ） and the contacting group 40 （51.28% ）] ;in accordance with the Winter＇s classification, horizontal impaction was the most common in both the two groups [90 （39.82%） vs. 34 （43.59%） ]. Further analysis of the relative position between IMTM and IAC showed that both in the protruding group and the contacting group, most IAC were located next to the root of IMTM [118 （52.21%） vs. 63 （80.77%） ]. Conclusion This study demonstrates the impaction type of IMTM next to IAC and the relative posi- tion between these IMTM and IAC. Furthermore, it provides guidance for the extraction surgery planning and how to prevent inferior alveolar nerve damage in the absence of CBCT.