Three-dimensional Numeric Simulation of Root Canal Irrigant Flow with Different Irrigation Needles

Abstract 

Introduction

The purpose of this study was to investigate, by using computational fluid dynamics (CFD), the effect of needle tip design on irrigant flow pattern.

Methods

Parameters of an in vitro irrigation model were used to create CFD models. Experimental data obtained by recording the dynamic fluid distribution during irrigation with 27-gauge notched (Appli-Vac) and side-vented open-ended (Vista-Probe) needles, placed at 3 and 5 mm from the apex of a simulated straight root canal prepared in a plastic block, were used to validate the results of CFD analysis. Two “virtual” needle tip designs were also included in CFD analysis, one with a beveled tip (based on Appli-Vac) and one with side-vent based on Vista-Probe needle but with a closed-end tip. Apical pressure, flow velocity at wall, and flow velocity distribution within root canal were determined by CFD.

Results

Flow patterns generated by CFD were in close agreement with the in vitro model. When placed 3 mm from the apex, the irrigant reached, or almost reached, the apex with all 4 needle designs. When placed 5 mm from the apex, the irrigant did not reach the apex with the side-vented needles. Irrigant velocities on canal walls were very low (0–0.7 m/s) compared with that within the needle lumen (∼7 m/s) and varied as a function of needle tip design. Apical pressure was highest with the beveled needle and lowest with the side-vented closed-end needle.

Conclusions

Irrigation needle tip design influences flow pattern, flow velocity, and apical wall pressure, all important parameters for the effectiveness and safety of irrigation. Computational fluid dynamics can be a valuable tool in assessing the implications of needle tip design on these parameters.

Key Words: Computational fluid dynamics, endodontic, irrigation, needle, tip design