Comparative Analysis of Diagnostic Accuracy of OPG and CBCT in the Evaluation of Impacted Mandibular third Molar Proximity to the Mandibular Canal.

Abstract

Introduction: Mandibular third molars are the most frequently impacted teeth. The proximity of impacted third molars to the inferior alveolar canal requires particular consideration during extraction. Hence, we aimed to compare the diagnostic accuracy of CBCT and OPG using radiographic signs of Rood and Shebab's and find out the risk of mandibular nerve injury.

Methods: A prospective study was conducted in 50 subjects. All patients underwent digital OPG evaluation based on Winter's classification of impacted teeth and Rood and Shehab's classification of seven radiographic signs. Cases with any positive finding were examined using CBCT to assess the positioning of the mandibular canal and alveolar ridge.

Results: Horizontal and mesioangular impactions were at higher risk of inferior alveolar nerve damage (p< 0.01 and p < 0.05) along with lingual position of canal (p<0.001), Darkening of roots, interruption of the mandibular canal (p<0.001), and diversion of the mandibular canal (p< 0.04) were associated with a higher risk of damage during extractions.

Discussion: The current study confirmed that horizontal and mesioangular impactions showed a significant association with the absence of cortication between the mandibular canal and third molar roots, indicating a high risk of nerve injury, similar to other studies. Also, CBCT has been proven to be the best imaging modality owing to its high diagnostic accuracy.

Conclusion: In the current study, CBCT was considered the gold standard, and diagnostic accuracy was higher than OPG. There was fair agreement about the mesioangular and horizontal impaction and their proximity to the mandibular nerve.