Introduction: Dental fusion is a developmental anomaly in which two teeth buds join each other at different levels. Objective: To report a case of a lower canine and a lower lateral incisor with separate crowns and root fusion, with root canals connected and apical periodontitis. Methods: One year earlier, the patient had received root canal treatment in the canine; however, there was no remission of symptoms. Endodontic treatment was performed with reinstrumentation, passive ultrasonic irrigation with sodium hypochlorite, smear layer removal and intracanal medication with calcium hydroxide. A week later, the symptoms had disappeared and the canals were filled with gutta-percha and Sealapex by means of the Tagger hybrid technique. Results: After two years and two months, the patient exhibited periapical tissues healing. Conclusion: The detection and proper management of developmental tooth anomaly cases is mandatory for treatment success.