锥形束CT在下颌阻生第三磨牙拔除术中的应用研究

Application of cone beam computed tomography in extraction of impacted mandibular third molar

目的:利用锥形束CT(cone beam computed tomography,CBCT)观测下颌阻生第三磨牙(impacted mandibular third molar,IMTM)与下颌神经管(mandibular nerve canal,MNC)的位置关系,为预防下牙槽神经损伤提供参考评价。方法:收集2017年6月~2018年10月就诊于我科曲面体层片提示牙根与下颌神经管重叠患者170例共232颗下颌阻生第三磨牙,征得患者同意后行CBCT检查,分析下颌阻生第三磨牙与下颌神经管的解剖关系。结果:曲面体层片显示重叠的232颗牙齿,CBCT三维观测仅117颗(50.4%)紧密接触,115颗(49.6%)则无接触关系。下颌神经管位于牙根颊侧(60.8%),明显高于根尖(29.3%)及舌侧(9.9%)位置,三者之间差异均有统计学意义(P<0.05)。下颌神经管位于牙根颊侧时,下颌神经管和牙根无接触与接触差异无统计学意义(P>0.05),舌侧时无接触与接触差异有统计学意义(P<0.05),根尖位置时无接触与接触差异有统计学意义(P<0.05)。结论:CBCT能准确显示下颌阻生第三磨牙与下颌神经管的位置关系,为临床医师术前评估下牙槽神经损伤提供依据。

Objective:The position relationship between impacted mandibular third molar and mandibular nerve canal was observed by cone beam computed tomography(CBCT),which provided a reference for the prevention of inferior alveolar nerve injury.Methods:A total of 232 impacted mandibular third molars were collected from 170 patients with overlapping between root and mandibular nerve canal by orthopantomography from June 2017 to October 2018.CBCT was performed with the consent of patients to analyze the anatomical relationship between impacted mandibular third molars and mandibular nerve canal.Results:Orthopantomography showed 232 overlapping teeth,only 117 cases(50.4%)had close contact relationship on CBCT,and 115 cases(49.6%)had no contact relationship.The probability of mandibular nerve canal locating on buccal side of root was 60.8%,which was significantly higher than that of apical(29.3%)and lingual side(9.9%).There was significant difference among the three locations(P<0.05).In buccal-lingual position,when the mandibular canal was located on the buccal side of the root,there was no significant difference between non-contact or contact relationship(P>0.05).There was significant difference between the non-contact and contact relationship of the lingual position(P<0.05),and also of the apical position(P<0.05)respectively.Conclusion:CBCT can accurately display the position relationship between the impacted third molar and the mandibular nerve canal,and provide a basis for clinicians to evaluate the injury of inferior alveolar nerve before operation.