A comparative study of panoramic radiography and cone-beam computed tomography about the relationship of mandibular third molar an inferior alveolar canal

Purpose: To evaluate the accuracy of Panoramic radiography（PAN） by using CBCT to compare the anatomical relationship between the mandibular third molar and the inferior alveolar nerve canal (IAN). Methods: The research sample included the imaging information of 953 MTMs and adjacent mandibular canals were studied. Statistical software SPSS25.0 was used, and chi-square test was used to analyze the correlation between demographic factors, type of obstruction, special imaging findings of PAN and IAN canal defect in CBCT. The factors related to IAN canal defect were evaluated by Logistic regression. Results: Among the 953 study subjects, 757 cases of inferior alveolar nerve canal cortical bone were intact and 196 cases of IAN canal are defect. The differences between mandibular duct wall defects in the classification of MTM, the darkening of roots, the interruption of the white line, the deviation diversion of canal, and the narrowing of canal were statistically significant. In logistic regression analysis, P&G classification (mesial-distal), the darkening of roots, and the interruption of the white line were risk factors for mandibular duct wall defects. Conclusions: The interruption of the white line, darkening of the root, and the P&G classification (mesial-distal) suggest an increased rate of IAN canal defects. The special imaging manifestations related to the absence of cortical bone in the mandibular canal wall in univariate analysis, this study still recommends that further detailed investigation of CBCT is recommended.