Anatomic evaluation of the retromolar canal by histologic and radiologic analyses

- The retromolar canal was detected at a relatively high prevalence rate (43.1%).
- The retromolar canal included within both blood vessels and nerves.
- The retromolar artery was larger than the nerve.
- Clinicians must be careful to vascular problems as well as nerve injury.

ObjectivesThe aim of this study was to identify the detailed anatomic morphology of the retromolar canal using histologic sections and cone-beam computed tomography (CBCT) images.Materials and methodsTwenty-two sides of the mandible obtained from cadavers and CBCT images of 72 patients (144 sides) were analyzed. All mandibles were prepared using conventional methods of tissue processing, stained with hematoxylin-eosin, and measured to elucidate the composition and dimensions of the retromolar canal with the aid of a light microscope. In addition, the prevalence, course, opening position, and distance of the retromolar canal from the second molar were measured on CBCT images.ResultsThe retromolar neurovascular bundle in the retromolar canal originated from the inferior alveolar neurovascular bundle, and the mean areas of the neurovascular bundle and each artery and nerve contained within it were 0.59, 0.07, and 0.05 mm2, respectively. The mean horizontal and vertical diameters of the neurovascular bundle were 0.82 and 0.90 mm, respectively. The retromolar canal was detected more often on CBCT images (43.1%, 31 out of 72 patients). It mainly arose vertically (71.0%) from the mandibular canal and opened in the middle portion (57.9%) of the retromolar triangle at a mean distance of 13.13 mm from the second molar.ConclusionsThe retromolar canal is a normal anatomic structure that is relatively common and contains both a relatively large artery and a nerve. Clinicians need to pay closer attention to vascular problems as well as nerve damage when they are performing surgical procedures in the retromolar area.