A retromolar canal is a branch of a mandibular canal and is rarely detected in the usual radiographic examination. We experienced a case in which damage to the nerve was avoided by having identified the retromolar canal on the image at the time of tooth extraction of the left lower third molar. The patient was a male in his twenties. Although he had consulted a nearby dental clinic for dental care of the molar of the left lower jaw, he was referred to our hospital. In a panoramic X-ray at the first examination, the retromolar canal diverged from the mandibular canal and was located above the lower third molar. Computed tomography imaging findings showed that the retromolar canal was in the cancellous bone buccal to the lower left third molar and the diameter was 3.5mm. For extraction of the left lower third molar, the lingual split technique was selected to avoid damage to the retromolar canal.
