Tabriz University of Medical Sciences Journal of Dental Research, Dental Clinics, Dental Prospects 2008-210X 8 3 2014 09 17 A Three-rooted Mandibular Second Premolar: A Case Report 184 186 10.5681/joddd.2014.034 EN Zahra Fathi Saeed Rahimi Reza Tavakoli Mahsa Amini Journal Article 10.5681/joddd.2014.034 2014 10 04 Presence of extra roots and canals should be considered before initiation of root canal treatment for the success of endodontic treatment. A mandibular second premolar with three separate roots is very rare and its prevalence has been reported to be around 0.1%. This case report explains non-surgical endodontic treatment of a mandibular second premolar with three separate roots and three separate mesiobuccal, midbuccal, and lingual canal orifices. Close attention to anatomic variations, thorough radiographic examinations, thorough evaluation of the pulp chamber floor, and use of magnifying and optical devices have been recommended for the success of endodontic treatment of mandibular second premolars with complicated root canal system anatomy.