Bifid mandibular canals: CBCT assessment and macroscopic observation.

PURPOSE: The bifid mandibular canal is an anatomical variation, which causes anesthetic failure and surgical accidents occasionally. The purpose of this study is to observe the prevalence and anatomical location of bifid mandibular canals, providing clinical value in reducing the occurrence of surgical accidents and postoperative complications. METHODS: A total of 321 outpatients were selected in this study. Their CBCT images were observed, and the prevalence of bifid mandibular canals as well as the composition ratios of each branch type was evaluated according to the classification of Naitoh. The bifid mandibular canals and their branches' diameter, length, horizontal distance to the buccal/lingual wall of the mandible, and vertical distance to the mandibular alveolar ridge were measured. Furthermore, 194 dry adult mandibles from the Department of Oral Anatomy and Physiology of Tianjin Medical University were observed to evaluate the prevalence and the average diameter of retromolar foramina. RESULTS: Of all the 321 patients, 84 (26.17%) cases of bifid mandibular canals and 105 (16.36%) sides of unilateral bifurcation were observed. Based on Naitoh's classification, the retromolar canals were the most common types (46.67%), followed by the forward canals (40.00%), the dental canals (10.48%) and the buccolingual canals (2.86%). In 194 dry adult mandibles, 23 cases (11.86%) and 29 sides (7.47%) of retromolar foramina were found and the average diameter of retromolar foramina was 0.94 +/- 0.30 mm. CONCLUSION: More than a quarter of the population has the bifid mandibular canal, which is a potential factor of the onset of surgery accidents. CBCT is an effective method to identify the branches of mandibular canals. Preoperative CBCT examination can help reduce various postoperative complications.