The purpose of this study was to examine the effect of heating on the physical properties of four types of premixed calcium silicate-based root canal sealers. Endoseal MTA, Well-Root ST, EndoSequence BC Sealer, EndoSequence BC Sealer HiFlow, and AH Plus (epoxy resin root canal sealer) were heated at 100°C for 1 min, and changes in setting time, flow, and film thickness were evaluated in accordance with ISO 6876:2012 standards. In addition, pH measurement and scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses of the set materials were performed. All root canal sealers heated at 100°C showed significant decreases in setting time and flow, particularly Endoseal MTA. In addition, the film thickness of Endoseal MTA increased significantly after heating at 100°C. The pH and SEM/EDS results were not affected by heating. Heating calcium silicate-based root canal sealers accelerated setting time, decreased flow, and increased film thickness. However, the degree of these changes varied among the products. The present findings indicate that heat-induced changes in the physical properties of calcium silicate-based root canal sealers could adversely affect the quality of warm vertical condensation technique.

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.

Laser-activated root canal irrigation (LAI) with an Er:YAG laser is considered more effective than other irrigation methods, whereas the effectiveness of LAI in cleaning lateral canals far from the laser tip remains unclear. This study aimed to compare the efficacy of removing calcium hydroxide [Ca(OH)2] paste from lateral canals using LAI or ultrasonic-activated irrigation (UAI), and to examine the effect of tip insertion depth and laser irradiation parameters on cleaning efficacy. Radiopaque Ca(OH)2 paste (Calcipex II) was injected into lateral canals 6 mm from the root apex in 192 J-shaped simulated root canal models. LAI (Erwin AdvErl; 30 or 70 mJ; 10 or 20 pulses per second; laser tip R200T or R600T) and UAI (ENAC SE10; output setting: 3) were performed 3 times for 20 s. The laser tip was placed at 8–0 mm coronal to the lateral canal location. The volume of Ca(OH)2 paste before and after the experiment was measured using micro-CT (SMX-100CT). The Ca(OH)2 removal rate by LAI was significantly higher than UAI at all tip insertion depths. Ca(OH)2 removal rate in LAI was significantly lower at the 8 mm position compared with other positions (P < 0.05). When the tip insertion depth was fixed at this position, Ca(OH)2 removal rate increased significantly when pulse energy and tip diameter were increased (P < 0.05). LAI removed Ca(OH)2 paste from lateral canals away from the tip more effectively than UAI. Increasing the pulse energy and tip diameter improved the removal efficiency.

Objective: To evaluate the effectiveness of erbium:yttrium aluminum garnet (Er:YAG) laser-activated irrigation (LAI) for cleaning the apical root canal area beyond a ledge. Background data: This was the first study that evaluated the efficacy of LAI in debris and smear layer removal from such hard-to-reach canal areas in human teeth. Methods: Eighty-eight human maxillary molars with either a mesiobuccal or distobuccal canal with 25°–35° curvature and mature apices were used. Following instrumentation to a size 25/0.02 taper, a ledge was created at 2.2 ± 0.7 mm short of the apex and checked using microcomputed tomography. Samples were divided into four groups: syringe irrigation (SI), ultrasonic-activated irrigation (UAI), agitation with the XP-endo Finisher (XP), and LAI. Each group was subdivided based on the irrigation regimen: 9 mL of 6% sodium hypochlorite (NaOCl), and 6 mL of 6% NaOCl +3 mL of 14.3% ethylenediaminetetraacetic acid (EDTA) (n = 11). The apical 1-mm region was examined using scanning electron microscopy to evaluate the remaining debris and smear layer. Data were analyzed using the Kruskal–Wallis test and Mann–Whitney U test (a = 0.05). Results: Regardless of the irrigants used, LAI showed significantly lower smear layer scores than SI and XP (p < 0.05), with insignificant difference as compared with UAI. LAI showed significantly better debris removal than SI (p < 0.05) when NaOCl alone was used. Conclusions: In the apical area of ledged canals, the cleaning efficacy of Er:YAG LAI with/without EDTA was higher than SI and XP, but was comparable with UAI. Clinical Trial Registration number D2014-33.