Objectivity and reliability of panoramic radiographic signs and cone-beam computed tomography in the assessment of a superimposed relationship between the impacted mandibular third molars and mandibular nerve: A comparative study

Aim: To evaluate the relationship between panoramic radiographic signs and cone-beam computed tomography (CBCT) in the assessment of a superimposed relationship of the impacted mandibular third molars and mandibular canal. Materials and Methods: Panoramic and CBCT images were evaluated independently to assess the relationship between the mandibular canal and the impacted mandibular third molar roots by two oral and maxillofacial radiologists. The results were tabulated and the association of panoramic radiographic and CBCT findings was analyzed using Chi-square test and Fisher's exact test. All of the analyses were carried out with PASW Statistics 18.0. Results: Panoramic radiographic findings were statistically significant with CBCT findings (P < 0.01). Cases of darkening roots without interruption and lingual cortical perforation suggested more frequent buccal placement of mandibular canals. Cases of darkening roots with interruption and complete lingual cortex perforation suggested more frequent lingual placement of mandibular canals. Conclusion: The results of the present study suggest that, although panoramic radiography is an effective method for preoperative evaluation prior to mandibular third molar extraction, its predictability is low with regards to the emergence of nerve lesions. Therefore, it is mandatory to know the true three-dimensional imaging relationship between the mandibular canal and impacted mandibular third molars. Thus, CBCT is the best method for risk assessment and planning prior to surgical procedures to prevent inferior alveolar nerve injury.