Mid-mesial canal in mandibular first molars: A report of two cases

Introduction: The most common morphology of mandibular molars is two roots and three root canals; nonetheless, unusual anatomic variations may exist. Case reports: This study reports two cases of mandibular first molars with a mid-mesial root canal that underwent treatment and follow-up in the Endodontics Department of Isfahan School of Dentistry. During the initial treatment, the mid-mesial root canal had not been detected in both cases due to the failure to prepare a convenient access cavity.  Conclusion:Preparation of convenient access cavity, knowledge of canal anatomy and presence of uncommon variations should be more appropriately taken into account during the general training and systematic re-training programs of general dental practitioners.   Key words:Anatomy, endodontics, molars, root canal.