Three-dimensional numeric simulation of root canal irrigant flow with different irrigation needles

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 ( approximately 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.