Fluid Movement in the Apical Area Beyond the Ledge During Er:YAG Laser-Activated Irrigation: A Particle Image Velocimetry Analysis.

This study aimed to examine the irrigant flow generated by laser-activated irrigation (LAI), in comparison with ultrasonic-activated irrigation (UAI) and syringe irrigation (SI), in the area beyond the ledge using particle image velocimetry (PIV). There was no reported study about cleaning efficacy of LAI beyond the ledge. Forty-nine J-shaped root canal models (40° curvature) were instrumented to no. 35/0.06, and a ledge, 2.5 mm deep, was created with no. 60/0.08 instrument at 5 mm from the apical foramen in each canal. The samples were irrigated with LAI [30 mJ/5 pulse per second (pps), 30 mJ/10 pps, 30 mJ/20 pps, 50 mJ/10 pps, 70 mJ/10 pps], UAI, and SI with a tip/needle insertion depth of 5 mm from the apical foramen ( = 7). PIV was performed with glass beads and a high-speed camera. Velocities were compared in the coronal and apical areas to the ledge, respectively. In the apical area, all LAI groups and UAI produced a higher velocity than that of SI, and LAI at 30 mJ/20 pps and 70 mJ/10 pps showed significantly higher velocity than that of UAI ( < 0.05). In the coronal area, LAI at 30 mJ/20 pps generated a significantly higher velocity than that of UAI and SI ( < 0.05). Velocity was significantly slower in the apical area than in the coronal area in UAI and SI ( < 0.05), but was similar between both areas in LAI except at 30 mJ/20 pps. Among tested laser settings, higher velocity was significantly achieved by LAI at 30 mJ/20 pps and 70 mJ/10 pps compared with UAI in the canal area beyond the ledge. SI generated lower fluid movement than LAI and UAI in both canal regions.