Comparison of Analog Panoramic Radiography and Cone Beam Computed Tomography for Assessing Relationship between Impacted Mandibular Third Molar and Inferior Alveolar Nerve Canal

The aim of this study is to compare OPG and CBCT for assessing relationship between impacted mandibular third molar and inferior alveolar nerve. 60 patients in the age range of 18–30 years with panoramic radiographs and impacted mandibular third molar (IMTM) were included in this study. A trained radiologist evaluated the panoramic radiographs and CBCTs, the relationship between IAN and IMTM was assessed using the Shehab & Rood classification and the nerve proximity to the third molar, both when in contact and separated, was determined using CBCT. The sensitivities and specificities of these findings were evaluated. Kappa values were used to assess the intra-observer reliability. Of 60 impacted third molars, 33 teeth showed contact between the tooth and the nerve. Except about narrowing of the canal, the difference between the two methods (panoramic and CBCT) in determining the relationship between the tooth and the nerve was not significant. The highest sensitivity of panoramic radiography was related to darkening of the root (48.6%), and the lowest sensitivity related to narrowing of the canal (5.7%) and diversion of the canal (5.7%) The highest specificity related to the deflection of the root (100%) and interruption of the white line (96%), and the lowest specificity related to deflection of the root (64%) and narrowing the canal (64%). More than 50% of cases indicate direct contact between the molar and the nerve. In diversion of the canal, interruption of the radiopaque border of canal, and darkening of the roots, the possibility of this contact is considerably high. The relationship between diversion of the canal and interruption of the radiopaque border of canal has a high predictive value for indicating the absence of this contact.