锥形束CT中下颌第三磨牙与下颌管的关系及其与阻生类型的相关性分析

The Accuracy of CBCT in Locating the Mandibular Canal and Impacted Mandibular Third Molar

目的:研究在曲面断层片上表现为下颌管与下颌第三磨牙影像重叠的患者,其二者在锥形束CT(CBCT)上的位置关系,为临床风险评估提供参考。方法:研究184颗(146例患者)在曲面断层片上表现为与下颌神经管有影像重叠的下颌第三磨牙,在CBCT上其牙根与下颌神经管的位置关系。分析两者之间位置关系与阻生类型、性别、曲面断层片上下颌神经管骨白线是否可见的相关性。测量下颌第三磨牙与下颌神经管接触的患者其接触的长度及宽度,分析接触长度、宽度与牙根和下颌神经管相对位置的相关性。结果:CBCT图像上下颌第三磨牙与下颌神经管之间是否接触,与其在颌骨内的深度相关,低位阻生接触可能大(P=0.002),与性别相关,女性多(P=0.020);当曲面断层片中下颌神经管骨白线不可见时,接触可能大(P=0.001)。当下颌神经管与牙根舌侧接触时,接触的长度、宽度可能较大。结论:CBCT与曲面断层片相比能更好地体现下颌阻生第三磨牙与下颌神经管的关系,提供更准确的术前风险评估。

Objective： To evaluate the accuracy and reliability of CBCT examination in image analysis of the superimposition of mandibular canal （MC） and impacted mandibular third molar （IMTM） by panoramic radiography. Methods： 184 MC and IMTM superimposed images （146 patients） from panoramic radiography were reexamined by CBCT. Correlations of their relationship and type of tooth impaction, gender, visibility of the white line of bone of the MC by panoramic radiography were analyzed. Patients with IMTM in contact with the MC, the length and width of the connection were measured, correlations of the length and width and the relative location of tooth root and MC were analyzed. Results： In CBCT image, the impacted mandibular third molar contact with the mandibular canal is related to position depth of the tooth root （P=0.002） and gender （P=0.020）, and also related to the MC white line was visible in panoramic radiograph （P= 0.001）. The length and width of the connection could be larger when the MC was in contact with the lingual side of tooth root. Conclusions： CBCT may able to generate images with sub-millimeter isotropic resolution, it is more sensitive and accurate for detecting dentoalveolar structures and provide more accurate reference for clinical risk assessment.