Effect of needle insertion depth and root canal curvature on irrigant extrusion ex vivo

Introduction The aim of this study was to evaluate the effect of needle type and insertion depth, apical preparation size, and root canal curvature on irrigant extrusion by using a recently introduced method. Methods Sixteen human teeth with a straight root canal (group A) and 16 with a moderately curved root canal (group B) were sequentially prepared to sizes 25 or 35, .06 taper and mounted on a plastic vial filled with distilled water to simulate a periapical lesion. The vial was either closed or open to the environment. A point-conductivity probe was used to determine the volume of extruded irrigant into the vial. NaOCl was delivered by an open-ended or a closed-ended needle at 1, 3, or 5 mm short of working length. Results were analyzed by two 4-way mixed-design analyses of variance. The level of significance was set to P < .05. Results The open-ended needle extruded significantly more irrigant than the closed-ended. Irrigant extrusion decreased as needles moved away from working length or when the apical size was increased. Needle wedging increased extrusion, especially when an open-ended needle was used. Root canal curvature did not have a statistically significant effect on irrigant extrusion. Conclusions Needle type, needle insertion depth, and apical preparation size had a significant effect on irrigant extrusion