Digital versus conventional panoramic radiography in predicting inferior alveolar nerve injury after mandibular third molar removal

The aim of the study was to compare the accuracy of conventional and digital panoramic radiography (OPG) in relation to 4 specific high-risk signs (interruption of the superior cortical line, diversion, narrowing of the canal, and dark band of the root), which would indicate a close anatomic relationship between third molar roots and the inferior alveolar canal.Four hundred mandibular third molar surgical removals after conventional and 272 after digital radiographs were evaluated in the study. The association between postoperative inferior alveolar nerve (IAN) paresthesia and the presence of any preoperative high-risk signs in the OPG was investigated. Bivariate and multivariate logistic regression analyses were completed to compare the accuracy of conventional and digital radiographic techniques detecting high-risk signs predicting possible IAN paresthesia.Digital OPG results showed significantly higher sensitivity in diversion (P = 0.014) and narrowing (P < 0.002) of the canal, whereas the specificity of these signs was significantly lower (P < 0.001 and P = 0.035). The likelihood ratio analysis and multivariate logistic regression analysis did not prove the significant difference between digital and conventional imaging according to the examined high-risk signs. Positive predictive values of the signs were found in conventional radiography between 3.6% and 10.9%, whereas in the digital images, it ranged from 2.9% to 7.9%.The results of this study failed to prove significant difference between the accuracy of digital and conventional OPG for predicting IAN paresthesia, whereas low positive predictive values indicate both imaging techniques as inadequate screening methods for predicting IAN paresthesia after mandibular third molar removal.