Laser induced explosive vapor and cavitation resulting in effective irrigation of the root canal. Part 1: a visualization study

Background and Objectives: Limited information exists regarding the induction of explosive vapor and cavitation bubbles in an endodontic rinsing solution. It is also not clear whether a fiber has to be moved in the irrigation solution or can be kept stationary. No information is available on safe power settings for the use of cavitation in the root canal. This study investigates the fluid movements and the mechanism of action caused by an Er,Cr:YSGG laser in a transparent root model. Material and Methods: Glass models with an artificial root canal (15 mm long, with a 0.06 taper and apical diameter of 400 µm) were used for visualization and registration with a high-speed imaging technique (resolution in the microsecond range) of the creation of explosive vapor bubbles with an Er,Cr:YSGG laser at pulse energies of 75, 125, and 250 mJ at 20 Hz using a 200 µm fiber (Z2 Endolase). Fluid movement was investigated by means of dyes and visualization of the explosive vapor bubbles, and as a function of pulse energy and distance of the fiber tip to the apex. Results: The recordings in the glass model show the creation of expanding and imploding vapor bubbles with secondary cavitation effects. Dye is flushed out of the canal and replaced by surrounding fluid. It seems not necessary to move the fiber close to the apex. Conclusion: Imaging suggests that the working mechanism of an Er,Cr:YSGG laser in root canal treatment in an irrigation solution can be attributed to cavitation effects inducing high-speed fluid motion into and out the canal

Laser induced explosive vapor and cavitation resulting in effective irrigation of the root canal. Part 2: evaluation of the efficacy

Background and Objectives: Limited information exists regarding the efficacy of laser activated irrigation (LAI) on removal of root canal debris. This study compares the efficacy of LAI for removal of debris in root canals as compared to conventional irrigation (CI) and passive ultrasonic irrigation (PUI). Materials and methods: A splitted tooth model was constructed with straight roots prepared to a 0.06 taper and an apical diameter of ISO 40. A vertical groove was cut in the canal wall at 2-6 mm to the end of the canal in one halve of the root canal wall and filled with dentinal debris. In group 1 root canals were irrigated with 2.5% NaOCl by hand (20 seconds) with the needle 1 mm short from the apical stop, in group 2 NaOCl was ultrasonically activated (20 seconds) with an Irrisafe tip 1 mm short from the apical stop, and in group 3 NaOCl was activated with an Er,Cr:YSGG laser (Z2 Endolase tip −200 µm fiber, four times for 5 seconds, 75 mJ, 20 Hz, stationary at 5 mm from the apical stop). The remaining quantity of dentin debris in the groove was evaluated using a scoring system. Results: LAI resulted in significantly less debris than PUI (P<0.005) and CI (P<0.0005). PUI also showed significantly less debris than CI (P<0.005). Conclusion: Under the conditions of this study LAI is statistically significantly more effective in removing artificially placed dentin debris in a root canal as PUI and CI. Lasers Surg. Med. 41:520-523, 2009. © 2009 Wiley-Liss, Inc

The efficacy of ultrasonic and PIPS (photon-induced acoustic streaming) irrigation to remove artificially placed dentine debris plugs out of an artificial and natural root model

The aim was to validate an artificial resin ‘root canal wall groove model’ (RCWGM) mimicking the situation of natural roots with a groove of identical dimensions on debris removal out of these grooves, and to evaluate Erbium ‘laser-activated irrigation’ (LAI) with two conical tips at PIPS (photon-induced photoacoustic streaming) settings, with different activation times and different root canal positions on debris removal out of the grooves. A split RCWGM was used (resin blocks and roots of maxillary canines) with a canal size 40/0.06. The grooves in the apical third were filled with stained dentinal debris. Seventeen irrigation protocols (n = 20) were used: syringe-needle irrigation (3× 20 s), manual dynamic activation (1× 60 s), ultrasonically activated irrigation (UAI) with 25/25 Irrisafe (3× 20 s) and LAI (2940 nm Er:YAG) with X-Pulse or PIPS tips at PIPS settings (20 mJ, 50 μs, 20 Hz) and with the fibre (IN) or (OUT) the canal: IN during 1× 20 s, and OUT during 1× 20 s, 2× 20 s, 3× 20 s, 30 s, 2× 30 s and 1× 60 s. The quantity of remaining dentine debris in the groove was evaluated on a numerical scale. Statistical analysis was performed by means of proportional odds logistic regression, equivalence testing and Wald tests. The level of significance was set at 0.05. Resin models and the RCWGM with natural teeth can be called equivalent (log odds ratio 0.185). There were mostly no statistically significant differences for debris removal between UAI and LAI (p &gt; 0.05) and between LAI with PIPS and X-Pulse (p &gt; 0.05). Although not statistically different, the numbers of completely cleaned grooves were higher with LAI than with UAI for a 1-min activation, confirming findings from other studies. There is no difference in cleaning efficacy between X-Pulse and PIPS tips at PIPS settings. © 2019, Springer-Verlag London Ltd., part of Springer Nature