Endodontic impact of cavitation and bubble formation induced by 2780-nm Er,Cr:YSGG laser using radial firing tips on simulated root canals

Abstract Limited information exists regarding the induction of explosive vapor and cavitation bubbles in an endodontic rinsing solution. Despite several reports stating the positive effects of the Er,Cr:YSGG laser and radial firing tips (RFT) for root canal system cleansing and smear layer removal, no information is available regarding the basic behavior of cavitation in root canals. Thus, the aim of this visualization study was to understand the cavitation process generated by the Er,Cr:YSGG laser, understand its previously reported clinical endodontic implications, and explore future ones. Methods This study investigates the fluid movements and the mechanism of action caused by an Er,Cr:YSGG laser and RFT in a transparent root model using the most commonly reported settings (1.25 W, 60 µs, 50 Hz). Results Results were obtained by a high-speed imaging technique that allowed to observe each individual emitted pulse and their effect in both free water environment and transparent root canal model, resulting in an image of the laser-bubble activity every 10 µs. From this experimental set-up, it was possible to visualize for the first time and attest the speed and diameters of the primary cavitation bubbles, their evolution, and behavior over time. It was also possible to identify the differences between the cavitation process using either the RFT2 or RFT3. From this physical phenomena observation, relevant clinical facts could now be explained: (1) the time required for the cavitation process to become pronounced and its impact on smear layer removal in apical thirds and (2) how negative apical pressure and peri-apical drainage could be obtained by means of secondary cavitation and fluid movements in root canals.