Efficacy of different irrigation needles used in endodontics: an in silico and an in vitro investigation.

Objective: Irrigation is a clinical procedure in which needles of various designs, attached to syringes, are delivered by positive pressure to cleanse the root canals of infection-promoting agents. Despite being available in multiple designs and different materials, the irrigant does not necessarily reach every portion of the canal. This study compared four different needle designs in terms of depth of penetration of the needle (DOP), wear of the needle and fluid dynamics of the irrigant (FD). Methods: Stereolithography was used to manufacture four 3D-printed single-rooted mandibular premolars with double curvature. The four needle designs used were Group I (NiTi open-ended, notched needle tip), Group II (Stainless steel, single-sided vented needle tip), Group III (Stainless steel, double-ended needle tip), and Group IV (Soft propylene, multi-vented needle tip) (n = 10 in each group). After assigning each tooth to a group, a stereomicroscope was used to measure the DOP. Pre- and post-irrigation scanning electron microscopy images of three randomly chosen needles from each group helped qualitatively determine the wear. Later, particle image velocimetry (PIV) experiments for each of the four needle designs were subsequently compared with those obtained from computational fluid dynamics (CFD). Results: The open-ended syringe had the significantly lowest mean DOP as determined by one-way ANOVA and Tukey's post hoc test. Wear was significantly lowest in the non-metallic syringes. The PIV and CFD analyses were in close agreement with each other. The non-metallic needle exhibited the highest pressure and axial velocity near the apex. Conclusion: The validated CFD models showed a greater canal coverage and irrigant flow from the non-metallic syringe in the double curvature root canal simulations; though with the highest risk of apical extrusion.