Radiographic Assessment of Features of Impacted Mandibular Third Molars With Post-Operative Injury to the Inferior Alveolar Nerves: A Record-Based Cross-Sectional Study

Background Surgical removal of impacted mandibular third molars (IMTMs) is among the most common minor oral and maxillofacial surgical procedures. However, it carries the risk of complications, including injury to the inferior alveolar nerve (IAN). Panoramic radiography can predict this risk based on certain radiographic features, including root darkening, interruption of the radiopaque line of the inferior alveolar canal, canal diversion, dark and bifid apex, root deflection, narrowing of the IAN canal, and root narrowing. Objective To assess the prevalence and distribution of seven radiographic signs predictive of IAN injury during mandibular third molar surgery namely, root darkening, interruption of the white line, IAN canal diversion, root deflection, narrowing of the IAN canal, dark and bifid apex, and root narrowing and evaluate their correlation with clinical outcomes in adult patients. Methods This retrospective, cross-sectional study reviewed 258 panoramic radiographs of adult patients aged 18–60 years (120 males and 138 females) with 341 impacted mandibular third molars located in proximity to the IAN canal. Predictor variables were the seven radiographic signs listed above. The primary outcome variable was postoperative IAN injury. Data were analyzed using SPSS version 23.0. Statistical tests included ANOVA, chi-square, and correlation coefficients, with significance set at p<0.05. Data were presented using descriptive statistics, tables, charts, and graphs. Results The most frequent radiographic sign was interruption of the radiopaque superior margin of the IAN canal (n = 182, 70.5%), followed by narrowing of the IAN canal (n = 143, 55.4%) and root darkening (n = 105, 40.7%). Of the 341 IMTMs, 76 (21.4%) were surgically removed, and 13 (17.1%) of these cases resulted in IAN injury. Among them, eight had interrupted radiopaque lines, three had canal narrowing, and one each showed root deflection and root darkening. Conclusion The most predictive radiographic signs of IAN injury during surgical removal of IMTMs were interruption of the radiopaque canal margin, canal narrowing, and root darkening. Surgeons should carefully assess these signs preoperatively to reduce the risk of nerve injury.