Ability of two radiographic methods to identify the closeness between the mandibular third molar root and the inferior alveolar canal: a pilot study

The aim was to compare the ability of two radiographic methods: the panoramic radiograph (PR) in combination with a 20-degree negative angle periapical radiograph (-20 degrees Pa) vs two periapical radiographs Pa + (-20 degrees Pa), in evaluating the closeness of the lower third molar root and the inferior alveolar canal. 2 radiographic methods of 32 impacted third molars were used. Two untrained dental students evaluated the closeness of the association between the root tip of the lower third molar and the inferior alveolar canal, both when in contact and separated, using dental cone beam CT as the gold standard. The position of the inferior alveolar canal relative to the third molar root was also recorded. The sensitivities and specificities of these findings were evaluated. Kappa values were used to assess the intra- and interobserver reliability. Of the 32 teeth, 23 (68.6%) showed contact between the root tip of the third molar and the inferior alveolar canal on dental cone beam CT, and 9 (31.4%) showed separation. The respective mean sensitivities of PR + (-20 degrees Pa) and Pa + (-20 degrees Pa) in detecting contact were 97.9% and 84.8% and the respective mean specificities in detecting separation were 16.7% and 44.4%. Intraobserver agreement in both techniques ranged from 0.69 to 0.94. The respective interobserver reliability was 0.88 in PR + (-20 degrees Pa) and 0.75 in Pa + (-20 degrees Pa). Both the PR + (-20 degrees Pa) and the periapical vertical tube-shift technique Pa + (-20 degrees Pa) have high potential for detecting the closeness between the third molar root and the inferior alveolar canal.