Comparative Analysis of Irrigation Techniques for Cleaning Ef fi ciency in Isthmus Structures

Introduction: This study aimed to evaluate the removal of a bio film-mimicking hydrogel from isthmus structures in a simulated complex root canal system consisting of 2 curved root canals by Laser-activated irrigation (LAI, AdvErl Evo, Morita) and mechanical activation techniques. Methods: A 3D-printed root canal model with 2 parallel root canals (60 degrees - curvature, radius 5 mm, dimension 25/.06) with a total length of 20 mm connected via isthmuses (2.5 ! 0.4 ! 0.2 mm) at 5 mm and 8 mm from the apical endpoint and with lateral canals (diameter 0.2 mm) in all directions at 2, 5, and 8 mm from the apex was filled with a colored bio film-mimicking hydrogel. Irrigation protocols under continuous irrigation with distilled water (3 ! 20s per root canal; 3 ml/20s; n = 20) included conventional needle irrigation ( = NI); manual agitation ( = MA, gutta-percha point 25/.06); EndoActivator ( = SAI-EA, 25/.04); EDDY ( = SAI-E, 25/.04); ultrasonically-activated irrigation ( = UAI) and LAI (Er:YAGlaser; P400FL tip at canal entrance; 25pps, 50 mJ, 300 ms). Removal of the hydrogel was determined as a percentage via standardized photos through a microscope. Statistical analysis was performed using Kruskal -Wallis and Conover tests ( P = .05). Results: Laseractivated irrigation (LAI) was associated with the greatest removal of hydrogel from the entire root canal system ( P < .05), followed by SAI-E. No signi ficant differences were reported for the coronal isthmus between LAI, SAI-E, NI, and MA ( P > .05), but inferior results for SAI-EA and UAI ( P < .05). In the apical isthmus, all techniques outperformed UAI ( P < .05), with LAI, SAI-E, and NI showing the best results ( P < .05). Conclusions: Laser-activated irrigation (LAI) was superior to other irrigation techniques in the entire root canal system. SAI-E and NI performed comparable to LAI in the isthmuses.