Prevalence and extent of long oval canals in the apical third

The aim of this study was to investigate the canal diameters in the apical roots of human teeth to determine prevalence and extent of long oval canals. This investigation was carried out on 180 extracted human teeth, 20 for each tooth group. Each root was horizontally sectioned at 1, 2, 3, 4, and 5 mm from the apex. Canal diameters were measured with a measuring microscope. In 293 (25%) of the 1181 cross sections investigated, a long oval canal (the long canal diameter was at least 2 times the short canal diameter) was identified. In some tooth groups, the percentage of long oval canals exceeded 50%. In most cases, the long diameter decreased apically; that is, the canal tended toward a rounder cross section. A wide range of diameters existed in all canals. Long oval canal is common in the apical 5 mm in human teeth. Many long and narrow oval canals would be impossible to instrument completely without perforating or significantly weakening the roots. Care should be taken in cleaning, shaping, and obturating these oval canals.