Sina Shirkavand
Maryam Zare Jahromi
Mohammad Reza Saei
Reza Ruzbeh
Razieh Moghaddam

Background: Successful endodontic treatment is dependent on the knowledge of root canal anatomy. Objectives: This study aims to investigate the root canal anatomy of mandibular first molars in an Iranian population. Materials and Methods: One hundred human mandibular first molars were collected and stored in ۵.۲۵% NaOCl. Radiographic images of the teeth were taken in mesial, distal, and buccal aspects using digital radiography. The root numbers were recorded, and the teeth were covered with lacquer. Access cavities were prepared, pulp tissue was dissolved, the apex was covered with liquid glue, and the root canals were injected with methylene blue. Decalcification of the teeth meant they were kept in ۱۰% nitric acid, and final dehydration meant they were kept in ۱۰۰% Isopropyl alcohol for ۷۲ hours and rendered clear by immersion in methyl salicylate. The number of root canals per tooth, the number of canals per root, and canal configuration in each tooth were recorded. Results: Ninety-nine of the ۱۰۰ teeth had two roots and the other had three roots. The teeth were classified based on the number of canals; there were ۲% with two canals, ۵۹% with three canals, and ۳۹% with four canals. Based on the Vertucci classification, the most prevalent canal configurations in the mesial root were types II and IV, and type I in the distal root. Conclusions: The most common root morphology is the two rooted morphology with three canals. Both the mesial and distal roots show wide variations in canal anatomy with type IV and type I canal configuration predominating in the mesial and distal roots, respectively. Iranian mandibular first molar teeth exhibit features close to the average Caucasian, Jordanian, and Kuwaiti’s root and canal morphology.