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Root canal morphology and assessment of incidence, type, and position of isthmus in permanent mandibular central incisor in North Indian population: An in vitro study

Background and Objectives: Mandibular incisor's anatomy presents a challenge when making endodontic access because of its small size and high prevalence of two canals and isthmus within them. The main objective of this study is to evaluate the root canal anatomy and its aberrant morphology in mandibular central incisors. Knowing the variations in canal anatomy such as two canals, presence of isthmus, type, its prevalence, and position in the mandibular central incisors, which help improve the procedure of successful root canal treatment. Materials and Methods: One hundred and twenty extracted human mandibular central incisor teeth were collected. Two different studies have been performed. Sixty teeth were studied through tooth clearing and dye penetration technique. Teeth were decalcified with 5% nitric acid, dehydrated with increasing concentrations of alcohol and rendered clear by immersion in methyl salicylate. Hematoxylin dye was inserted in access cavity and canals. The samples were observed under dental operating microscope. These samples were evaluated for root canal morphology to assess its root canal configuration. Sixty teeth were studied through sectioning of apical 3 mm (1, 2, and 3 mm from the apex) simulating a surgical resection method was followed. The sectioned samples were observed under stereomicroscope for evaluating isthmus and its type. Results and Conclusion: Sectioning study showed that canal shapes varied from round to oval, long oval, and ribbon shaped, while the prevalence of isthmus was more at 3 mm section. Tooth clearing study showed that 46.6% teeth had single canal, 49.8% teeth had two canals, and only 5% teeth had two separate apical foramina.