Micro-computed Tomographic Analysis of the Root Canal Morphology of the Distal Root of Mandibular First Molar

Introduction: The aim of this study was to evaluate the morphologic aspects of the root canal anatomy of the distal root of a mandibular first molar using micro computed tomographic analysis. Methods: One-hundred distal roots of mandibular first molars were scanned using a micro computed tomographic device at an isotropic resolution of 19.6 mu m. The percentage frequency distribution of the morphologic configuration of the root canal was performed according to the Vertucci classification system. Two-dimensional parameters (area, perimeter, roundness, aspect ratio,and major and minor diameters) and the cross-sectional shape of the root canal were analyzed in the apical third at every 1-mm interval from the main apical foramen in roots presenting Vertucci types I and II configurations (n = 79). Data were statistically compared using the Kruskal-Wallis and Dunn tests with a significance level set at 5%. Results: Seventy-six percent of the distal roots had a single root canal. Two, three, and four canals were found in 13%, 8%, and 3% of the sample, respectively. In 13 specimens, the configuration of the root canal did not fit into Vertucci's classification. Overall, 2-dimensional parameter values significantly increased at the 3-mm level (P < .05). The prevalence of oval canals was higher at the 1-mm level and decreased at the 5-mm level in which long oval and flattened canals were more prevalent. Conclusions: The distal roots of the mandibular first molars showed a high prevalence of single root canals. The prevalence of long oval and flattened canals increased in the coronal direction. In 13% of the samples, canal configurations that were not included in Vertucci's configuration system were found.