Prediction of nerve damage by comparing periapical radiographic signs of impacted mandibular third molars in close proximity to inferior alveolar nerve with their true tomographic relationship – An observational study

The purpose of the study was to correlate the accuracy of Roods and Shehab signs in an intraoral periapical radiograph (IOPAR) with Cone-beam computed tomography (CBCT) findings to indicate Cone-beam computed tomography only in high-risk conditions.70 impacted mandibular third molar teeth in 58 patients above 18 years with intraoral periapical radiographs presenting with one or more root and canal signs of Rood and Shehab criteria were included in the study. Winter's classification was recorded, and the patients were exposed to a Cone-beam computed tomographic scan. True canal – tooth relationship was assessed in the sectional images. Pearson Chi-square test was used to correlate periapical radiograph and tomographic findings, and an unpaired t-test was applied for descriptive analysis.Rood and Shehab canal criteria in the periapical radiographs were significantly correlated to direct contact of an impacted lower third molar with the canal (p< 0.05) and loss of cortication of Mandibular canal (p< 0.05) on the cone-beam computed tomography. Cone-beam computed tomography is recommended to assess the periapical radiographs with canal risk markers pre-operatively to help avoid iatrogenic complications.