Aim: The aim of this study was to assess the reliability of high risk injury signs to inferior alveolar nerve on panoramic radiograph, both individually and in combination, in predicting the absence of corticalisation between the mandibular canal and the third molar and cortical plate perforation on cone beam computed tomographic (CBCT) images.
Methods: The sample consisted of 20 subjects (20 left and 20 right mandibular third molars) who underwent pre-operative radiographic evaluation before extraction of impacted mandibular third molars. On panoramic radiographs, the most common high risk injury signs of inferior alveolar nerve (darkening of roots, interruption of white line, deviation of mandibular canal, narrowing of mandibular canal and superimposition of mandibular canal on roots) and bucco-lingual position of mandibular canal, supero-inferior position of mandibular canal, presence or absence of corticalisation between the mandibular third molar and the mandibular canal and cortical plate perforation on cone beam computed tomographic (CBCT) images were evaluated.
Results: Darkening of roots, superimposition of roots on mandibular canal were significantly associated with presence of corticalisation of mandibular canal (P value < 0.05) and interruption of white line was significantly associated with absence of corticalisation of mandibular canal (P value < 0.05). Darkening of roots was significantly associated with cortical plate perforation (P value <0.05). No statistically significant association was observed for the other panoramic radiographic findings, either individually or in association (P value > 0.05).
Conclusion: Darkening of roots and interruption of white line observed on panoramic radiographs were effective in determining the risk relationship between the tooth roots and mandibular canal, cortical plate requiring further three dimensional evaluation.