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

Objective: 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). Background data: There was no reported study about cleaning efficacy of LAI beyond the ledge. Materials and methods: 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 (n = 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. Results: 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 (p < 0.05). In the coronal area, LAI at 30 mJ/20 pps generated a significantly higher velocity than that of UAI and SI (p < 0.05). Velocity was significantly slower in the apical area than in the coronal area in UAI and SI (p < 0.05), but was similar between both areas in LAI except at 30 mJ/20 pps. Conclusions: 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.

Effect of Pulse Energy, Pulse Frequency, and Tip Diameter on Intracanal Vaporized Bubble Kinetics and Apical Pressure During Laser-Activated Irrigation Using Er:YAG Laser.

Objective: Er:YAG laser-activated irrigation (LAI) is an effective method of root canal cleaning, but irrigant extrusion from the apical foramen has been a concern. We aimed to analyze the effects of pulse energy, pulse frequency, and laser tip diameter on intracanal vapor bubble kinetics and periapical pressure generation during LAI with Er:YAG laser. Background: Irrigant vapor bubble kinetics are one of indices of root canal cleaning efficacy. However, few studies have compared laser pulse conditions to vapor bubble kinetics, in relation to periapical pressure. Methods: A plastic root canal model (apical diameter 0.50 mm, 6% taper, 20 mm long) was filled with distilled water, and LAI with Er:YAG laser (Erwin AdvErl Unit; 30, 50, or 70 mJ; 10, or 20 pulses per second; laser tip R200T or R600T) was performed with the end of the tip fixed at 15 mm from the root apex. The number, maximum diameter, and velocity of vapor bubbles were analyzed by high-speed video imaging. Pressure generated outside the apical foramen was measured with a pressure sensor. Results: Vapor bubble count and maximum diameter increased significantly with pulse energy, pulse frequency, and tip diameter. Vapor bubble velocity increased significantly with pulse frequency, but not with pulse energy or tip diameter. Periapical pressure increased significantly with pulse energy, pulse frequency, and tip diameter. Conclusions: The pulse frequency was the single factor that significantly affected all the examined parameters (the number, diameter, and velocity) of vapor bubble kinetics together with the periapical pressure.

Effect of Laser Energy and Tip Insertion Depth on the Pressure Generated Outside the Apical Foramen During Er:YAG Laser-Activated Root Canal Irrigation.

OBJECTIVE: The risk of extrusion of irritative irrigants into the extraradicular tissue should be minimized during root canal irrigation. This study aimed to examine the pressure generated outside the apex during Er:YAG laser-activated irrigation (LAI) in comparison with passive ultrasonic irrigation (PUI) and conventional syringe irrigation (SI). BACKGROUND DATA: LAI is reported to be efficient for root canal debridement, whereas the apical pressure generated during LAI has not been investigated in detail. METHODS: Plastic root canal models (apical diameter = 0.40 mm, taper = 6%, and length = 20 mm) were irrigated with water using either LAI with an Er:YAG laser (Erwin AdvEr; 30, 50, or 70 mJ, 10 pps), PUI, or SI. The tip insertion depth was set at 2, 5, or 10 mm from the apex. The pressure generated outside the apical foramen was measured with a pressure sensor connected to the apex of the model. RESULTS: When the tip was positioned at 2 mm and the power setting was changed, the mean maximum pressure values were LAI (30 mJ) = PUI < LAI (70 mJ) < SI (p < 0.05). When LAI was performed at 70 mJ and the tip was positioned at 5 or 10 mm, the pressure values were PUI < LAI = SI (p < 0.05). CONCLUSIONS: LAI generated similar or lower pressure outside the apical foramen compared with SI, irrespective of the laser energy and tip insertion depth examined. However, LAI generated higher pressure compared with PUI.