Abstract: The anatomical structure of maxillary second molars is complex, and the number of root canals varies greatly. Three root canals are common. In recent years, C shape root canal of maxillary first molars have been reported gradually. However, buccal fusion C shape root canals of maxillary second molars are rare. Here, we report a case of buccal C shape root canal accompanied by 1-3-1 type root canal in the right maxillary second molars. It provides a new diagnosis and idea for the treatment of abnormal root canal of maxillary second molars.

Key words: maxillary second molar, C shape root canal, root canal therapy, middle buccal root canal