RESUMO
INTRODUCTION: Successful endodontic treatment is dependent on a perfect knowledge of normal root canal anatomy and variations from the norm. This study was aimed to investigate the root canal anatomy of mandibular first premolars by both radiography and cross-sectional methods in an Iranian population. METHODS: Two hundred seventeen extracted human mandibular first premolars were used. Radiographs were taken in both mesiodistal and buccolingual directions for each premolar. Then, all the teeth were decoronated at the cementoenamel junction and resected perpendicular to their long axes into three equal sections and stained with fuscin. Digital photographs of the cross-sectional root surfaces were taken and surveyed at 40x magnification. The root canal configuration types were determined separately by radiographs and cross-sectional images for each premolar. RESULTS: Out of 217 teeth examined, 192 (88.47%) had a single root canal. The remaining 25 teeth (11.53%) showed two canals in at least one cross-section of their roots with five root canal configurations. In the mesiodistal (MD) radiographs, only 5.99% of premolars showed two canals with three root canal configurations. CONCLUSIONS: One-hundred ninety two out of 217 premolars showed one canal in both cross-section and MD radiography. Only 7 premolars were diagnosed as having more than one canal with the same canal configuration in both cross-sections and MD radiography methods.