Accuracy of Panoramic Radiograph for Determining the Relationship Between Mandibular Third Molar and Mandibular Canal: A Comparative Evaluation Using Cone-Beam Computed Tomography

Objectives: The purposes of this study were to evaluate an accuracy of panoramic radiographfor determining relationship between lower third molar and mandibular canal comparing with conebeamcomputed tomography (CBCT) and to study the relationship between signs on panoramicimage and nerve involvement.Materials and Methods: The study was a retrospective study of patients who were treatedby extraction or surgical removal of mandibular third molar from January 2013 to December 2018. CBCT was performed to all eligible patients who showed preoperative panoramic radiograph ofmandibular third molar roots approximated or superimposed to mandibular canal. Signs of nerveinvolvement on panoramic radiograph including darkening of root, deflection of root, narrowing ofroot, dark and bifid apex of root, interruption of white line of canal, diversion of canal, and narrowingof canal were compared to CBCT finding.Results: There were 154 mandibular third molars from 106 patients in this study. Accuracy,sensitivity, specificity, positive and negative predictive values of panoramic radiograph were 73.4%,83.1%, 60%, 74%, and 72.2%, respectively. A logistic regression analysis showed that darkening ofroot and interruption of white line of canal indicated significant correlation with nerve involvement(p < 0.01).Conclusions: Although panoramic radiograph provides less accurate details than CBCT, itcan give reliable preliminary information to evaluate relationship between mandibular third molarand mandibular canal. Moreover, darkening of root and interruption of white line could be used topredict nerve involvement.Keywords: Panoramic radiography, Cone-beam computed tomography, Third molar, MandibularNerve SWU Dent J. 2022;15(1):21-33.