Attempting to Determine the Relationship of Mandibular Third Molars to the Mandibular Canal on Digital Panoramic Radiography; Using CBCT as Gold Standard

(1) Background: It is important to know, radiologically, the relationship of Mandibular third molars (M3) to the mandibular canal to minimize postoperative complications by causing damage to the inferior alveolar vessels and nerve during extraction. This study aimed to evaluate the usability of various image analyses or high-risk radiographic findings in determining the relationship of M3s to the mandibular canal on Digital Panoramic Radiography (DPR). (2) Methods: DPRs of 60 patients with bilateral mandibular M3s in the dental arch, determined one of them to be related to the mandibular canal unilaterally by Cone Beam Computed Tomography (CBCT), were included. The high-risk radiological signs of M3s and Fractal Analysis (FA) and Histogram Analysis (HA) measurements of the trabecular bone around the M3s’ roots were compared. The Independent t-test, Kolmogorov–Smirnov, Mann–Whitney U, and Chi-Square tests were used for statistical analyses. (3) Results: DPR signs, such as radiolucency and bifurcation at the root apex, discontinuity of the mandibular canal cortex, and superimposition of the tooth root and mandibular canal, were observed statistically significantly more frequently for mandibular canal-related M3s (p < 0.05). As an objective image analysis, Lacunarity showed a statistically significant difference between related and unrelated M3s for measurements made inside and outside the mandibular canal (p < 0.05). (4) Conclusions: This study demonstrated that the discontinuity of the mandibular canal cortex and Lacunarity measured on DPR could help determine the relationship of the mandibular M3s to the mandibular canal.