Root canal morphology of mandibular first molars in a North Indian subpopulation: An in vitro clearing study

Abstract

Introduction: Limited information is available about the canal morphology of mandibular first molars in North Indian population. The purpose of this study was to evaluate the root canal morphology of North Indian mandibular first molars by clearing and staining technique. Materials and Methods: A total of 863 mandibular first molars collected from various places in North India were subjected to canal staining and decalcification procedures. Access cavities were prepared, and pulp tissue dissolved with sodium hypochlorite. Indian ink was injected into the root canals aided by negative pressure applied at the root tips. The stained teeth were decalcified with 7% hydrochloric acid. Instead of ascending concentrations of alcohol, a nonalcohol-based drying agent (anhydrous calcium chloride) was used to remove traces of acid and water from the specimens. The dried specimens were immersed in methyl salicylate to render them transparent. The following features were observed under operating microscope at ×6 magnification: (i) Number of root canals per tooth, (ii) number of root canals per root, (iii) root canal configuration in each root (Vertucci's classification), and (iv) lateral canals, intercanal communications, and their location. Results: Majority had two roots (85%) with three (61%) and four (30%) canals. Three roots were present in 15% of the specimens. Type IV (49%) and type I (48%) were the most common configurations in mesial and distal roots, respectively. Conclusion: First molars with two roots and three canals are a common feature in North Indian patients. Both roots showed wide variations in canal anatomy with type IV and type I configurations predominating in mesial and distal roots, respectively.