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.