Heat-Induced Changes in the Physical Properties of a New Premixed Calcium Silicate-Containing Root Canal Sealer: An In Vitro Study.

This study aimed to examine how heating affects the physical properties of a newly developed premixed calcium silicate-containing sealer (AH Plus Bioceramic Sealer; AHB), in comparison with EndoSequence BC Sealer (ES), AH Plus Jet (AH), and Pulp Canal Sealer. The setting time, flow, and film thickness were tested with or without heating at 100 °C for 30 or 60 s, in accordance with ISO6876:2012 standards. Ultrastructural and elemental analyses were performed with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Data were analyzed using one-way analysis of variance (ANOVA) with a Tukey post hoc test (α = 0.05). All sealers exhibited significantly shorter setting time and flow after heating at 100 °C for 30 and 60 s (p < 0.05). After heating, AHB showed a significantly higher film thickness compared to that of the other materials (p < 0.05). None of the tested properties of heat-applied AHB and ES met ISO standards, except the setting time in ES. The SEM/EDS results for AHB and ES were not affected by heating. The detected changes in physical properties can negatively impact the performance of premixed calcium silicate-containing sealers, particularly AHB, when warm vertical compaction is employed.

Comparison of vapor bubble kinetics and cleaning efficacy of different root canal irrigation techniques in the apical area beyond the fractured instrument.

Background/purpose: Intracanal fractured instruments hamper adequate root canal disinfection. The aim of this study was to evaluate vapor bubble kinetics and cleaning efficacy of different irrigation techniques in the apical area beyond the fractured instrument. Materials and methods: Sixty curved root canal models, in which a 3-mm fragment of a #20 K-file or a WaveOne Gold Primary (WOG) instrument was intentionally separated at 3 mm from the apical foramen, were irrigated with laser-activated irrigation with photon-induced photoacoustic streaming (LAI-PIPS; 20 mJ/15 Hz), laser-activated irrigation using an Er:YAG laser unit (LAI; 30 mJ/20 Hz), or ultrasonic-activated irrigation (UAI) for 5 s. Vapor bubble velocity and counts were analyzed using high-speed video imaging. To evaluate canal wall cleanliness, 40 canals of extracted human teeth with an intentionally separated 3-mm WOG fragment in the canal at 3 mm from the apical foramen were irrigated with LAI-PIPS, LAI, UAI or conventional syringe irrigation, using 17% EDTA (30 s, two cycles), saline (30 s), and 3% NaOCl (30 s, three cycles) as irrigants. Debris and smear layer on the apical canal wall beyond the fractured instrument were scored using scanning electron microscopy. Results: LAI-PIPS and LAI demonstrated higher vapor bubble counts than UAI. The WOG fragment permitted higher bubble velocity and count than the K-file fragment. LAI-PIPS and LAI showed better debris and smear removal than the other techniques. Conclusion: LAI and LAI-PIPS demonstrated higher vaporized bubble kinetics and better cleaning efficacy in the apical area, even in the presence of a fractured instrument.

Effect of tip insertion depth and irradiation parameters on the efficacy of cleaning calcium hydroxide from simulated lateral canals using Er:YAG laser- or ultrasonic-activated irrigation.

BACKGROUND/PURPOSE: 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. MATERIALS AND METHODS: 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). RESULTS: 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). CONCLUSION: 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.

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.