Diagnostic accuracy of position of impacted mandibular third molar on CBCT with panoramic radiography

ABSTRACT Objective: This study was conducted to evaluate the relationship between impacted mandibular third molar (IMTM) root and inferior alveolar nerve (IAN) as visualized on Orthopantomograph (OPG). Besides determining the need of Cone Beam Computed Tomography (CBCT) imaging, it also assesses the risk of IAN damage during surgical removal of this tooth. Method: A total of 100 patients underwent OPG and CBCT imaging as preoperative radiographic evaluation before extraction were included in the study. On panoramic radiographs, radiographic predictor signs of corticalization for the proximity and involvement between the IMTM and IAN and CBCT for presence or absence of corticalization and position of IAN with respect to IMTM were recorded and correlated. Chi-square test was used for statistical analysis. Results: Highly significant association was found between radiographic signs of Rood and Shehab such as “Darkening of root” and “Deflection of canal” and significant association was found between “Interruption of white line” and “Narrowing of canal” on OPG and presence of corticalization between IMTM root and IAN canal on CBCT. Highly significant association was found between these signs on OPG with position of IAN on CBCT such as “Darkening of Root” with “Lingual” position and “Interruption of white line” with “Interradicular” position, whereas significant association was found between “Narrowing of canal” with “Lingual” position of IAN on CBCT. Conclusions: Radiological evaluation with OPG alone may lead to inadequate assessments prior to surgical removal of IMTM because of its proximity with IAN and risk of neurosensory complication.