Optimization of Narrow Cavity Flow Field Via a Passive Self-Exciting Slot Jet for Root Canal Irrigation

Root canal treatment is crucial for preventing oral diseases, and its success hinges on the effective removal of biofilm and debris from the canal wall by the irrigant. However, the intricate and narrow anatomy of root canals limits the efficacy of irrigant jet in the critical apical region, hindering fluid mixing and the removal of wall-adherent material. To address this, a passive self-exciting jet technique using a novel slot jet needle is proposed. This design aims to reorganize the flow and induce secondary jet self-excitation within the narrow cavity, thereby enhancing root canal irrigation effect. The influence of the slot angle and aperture diameter is first investigated, and the results show that the efficacy of jet coupling depends not only on the slot jet direction but also on the relative strength of the jets. The irrigation performance is optimal when the slot angle is 90 deg and the aperture diameter is 0.1 mm. Furthermore, the influence of the tapering angle is investigated using the principle of a tapering nozzle. Compared to the clinically common prototype 30 G needle, the optimized design increases the effective cleaning area by up to 20.82% and the extending depth by up to 50.79%, while reducing the mean apical pressure by up to 23.39%. These improvements demonstrate that the cleaning performance, mass exchange capability, and safety are improved simultaneously.