The main objective of endodontic therapy is the thorough mechanical and chemical cleansing of the entire root canal system
and its complete obturation with an inert filling material. Failure to find and fill a canal contributes toward the failure of endodontic therapy .The root canal anatomy of mandibular first molars is complex. Studies of the morphologic structure of root canal systems have demonstrated the complexity, numbers, and distributions of canals in mandibular first molars. Approximately 2.75% of mandibular first molars have been found in five canals. Although the presence of middle mesial canals in mandibular molars is rare, but finding them is essential for a successful root canal treatment. In this study, we present
three mandibular first molars with three canals in the mesial root.