Successful Root Canal Treatment of an Atypical Mandibular Canine with a Boomerang-shaped Root and Canal System with a Large Periapical lesion—A Case Report with 9-year Follow-up

Aim This report describes an atypical mandibular canine with a single boomerang-shaped root and root canal system with a large periapical lesion managed by root canal treatment. Methods The chief complaint of a 16-year-old male was acute pain and an abnormal sensation in the right mandibular canine (tooth #27). The clinical examination revealed that tooth #27 had an unusual coronal morphology. The buccal aspect of the tooth resembled that of a normal canine but was significantly broader than expected. On the lingual aspect of the crown; however, there was an unusual cusp-like structure with ridges that was slightly less prominent than the buccal incisal tip. The intraoral periapical radiographs revealed a complex root with an obvious cow horn-shaped canal mesially and distally, but with the suggestion of a root structure joining the mesial and distal extensions. A large periapical lesion was present. Computed tomography revealed the presence of a single root and canal system shaped like a boomerang. Root canal treatment was performed and the patient was followed-up for 9 years. Results Following root canal treatment, the patient had no symptoms, no mobility, no periodontal pockets, or root resorption. At 9 years, the cone beam computed tomography images confirmed that satisfactory healing of the periapical tissues had occurred. Conclusion The mandibular right canine had a unique boomerang-shaped root and canal system. Effective shaping and cleaning of the complex canal shape plus thermoplastic root filling aided the successful healing of the periapical lesion.