RESUMO
INTRODUCTION: Canals can be of different shapes in cross section including round canals, oval canals, long oval canals or ribbon shaped canals. Recesses of nonround canals may not be included in the round preparation created by rotary instruments and thus they remain unprepared. The aim of this study included determination of shape and taper of the apical root canal based on diameter at different levels. Measurement of the diameter of the root canal at one, two and three mm cross sections from the apex of the tooth were done such that apical instrumentation in root canal treatment could be modified based on the results obtained. METHODS: This was a cross sectional study which used convenient sampling technique to determine the sample size. Seventy extracted teeth were sectioned horizontally at one, two and three millimeter from the apex using the diamond disc which was observed under trinocular research microscope for the determination of diameter of root canal under 10x magnification. Digital images of the sections were taken by a camera attached to the research microscope and analysis done using DigiPro 4.0 software. RESULTS: The most common canal configuration was oval. The taper of the canals was 25% in mesial root and 20% in distal in bucco-lingual orientation and 14% in mesial root and 15% in distal in mesio-distal orientation. CONCLUSIONS: The most prevalent canal configuration in this study was non round, however, most of the rotary instruments tend to prepare root canals into round shape making their use questionable. The taper of the root canals was found to be higher in our study than what most of the shaping instruments have to offer. So it would be advisable to consider this fact while selecting instruments and preparing these non-round canals as far as the Nepalese subpopulation is considered.