Endodontic management of fusion with a complex root canal anatomy in mandibular posterior teeth

Abstract Objective To report a developmental-related tooth that the mandibular first molar fused to the second molar with seven canals and treated with a conservative option. Methods CBCT images were used for analyzing the complex morphoanatomy in coronal and root canal systems. The tooth was isolated with a rubber dam and seven canal orifices were identified. Root canal treatment under a microscope was carried out. Results The tooth was diagnosed as an anomalous fused mandibular molar with chronic apical periodontitis and the root canal treatment was successful. Conclusions We reported a rare case of fusion involving permanent mandibular molars and CBCT is a critical aid in efficiently diagnosing and understanding such an anatomically abnormal tooth. Clinical Relevance This study suggests CBCT analysis is important for understanding the abnormal structure and guiding for treating such a malformed tooth before operation. This study also provides a rare and interesting case for endodontics.