下颌阻生第三磨牙拔除损伤下牙槽神经风险的全景片影像分析

Panoramic radiographic study on the risk of inferior alveolar nerve injury after impacted mandibular third molar extraction

目的在全景片(panoramic radiography,PR)中分析下颌阻生第三磨牙拔牙损伤下牙槽神经风险的相关因素。方法对464例患者(522侧牙)在PR上分析下颌阻生第三磨牙和下颌管的影像关系,在数字卡尺上测量下颌阻生牙与下颌管上缘最短垂直距离,分析其与阻生牙类型及拔牙风险的关系。对所得数据进行确切概率法检验及秩和检验分析。结果 522侧牙中,下颌第三磨牙到下颌管最短距离大小与阻生牙类型、拔牙损伤神经风险有差异,近中阻生牙距离最小,并具有统计学意义。拔牙致下颌神经管暴露、下牙槽神经损伤与阻生牙与下颌管交叉、重叠距离有关,但阻生牙的类型与拔牙致下颌神经管暴露、下牙槽神经损伤无关。近中阻生类型距离最小,其次是水平阻生类型,而垂直阻生、远中阻生类型距离最大。下颌阻生第三磨牙与下颌管呈现交叉、重叠全景片影像关系时,拔牙对下牙槽神经损伤的风险加大。结论拔牙手术者应全面分析影像资料、临床资料,获取有价值的信息,同时不断地积累拔牙经验,才能避免或降低拔牙术中损伤下齿槽神经的风险。

Objective To observe the risk factors of inferior alveolar nerve damage after impacted mandibular third molar surgical extraction on panoramic radiography （PR）. Methods The shortest vertical distancebetween impacted mandibular third molars and inferior alveolar canal on PR were measured for 522 teeth from 464 patients,and the images were classified. Relationship analysis of impacted molar type and the risks of inju- ring alveolar nerve were also performed. Fisher exact probability test and a rank test were performed for collected data. Results Among 522 teeth, different distance between mandibular third molars and mandibularcanal differed in type of molar impaction and risks of injuring nerve after molar extraction. The shortest distance was found in mesioangular impacted tooth and there was statistical difference. Tooth extraction resulting in mandibular nerve canal exposure and inferior alveolar nerve damage was correlated with the cross and overlapped distance between impacted tooth and mandibular canal. But the type of impacted tooth and its extraction was not correlated with the results of mandibular nerve canal exposure and inferior alveolar nerve damage. Mesioangular impacted tooth had the shortest distance, and next was horizontal impacted tooth, and vertical impacted tooth and distoangular impacted teeth had the longest distance. When mandibular third impacted molarpresented cross, overlapped PR image correlation with mandibular canal, it would strengthen the risk of inferior alveolar nerve injury after molar extraction. Conclusion Tooth extraction operator should completely analyze the image materials and clinical records for obtaining valuable information, and should summarize toothextraction experiences continuously at the same time to avoid or to decrease the risk o{ inferior alveolar nervedamage during tooth extraction,