A three-dimensional study of canal curvatures in the mesial roots of mandibular molars.

The degree and configuration of canal curvature was studied in the mesial roots of 100 randomly selected mandibular first and second molars. The teeth were radiographed in buccolingual (clinical) and mesiodistal (proximal) directions with #8 K files in place. One hundred percent of the specimens demonstrated curvature in both views. No correlation in degree of curvature was found to exist between the clinical and proximal views. Secondary curvature, in a direction opposite to that of the principle curve, was seen more frequently in the proximal view. In the proximal view, canals exhibited greater mean curvature than in the clinical view 38% of the time. Weine type II morphology (two canals, one foramen) demonstrated the greatest range in canal curvature when viewed from the proximal. Coronal flaring with Canal Master rotary instruments to a level just coronal to the curve significantly reduced the severity of curvatures in both views for most cases.