Purpose: The objective of this study was to obtain a better understanding of the working mechanism of the Er,Cr:YSGG laser in endodontics using specialized imaging techniques. Materials and Methods: Using a high-speed imaging setup, cavitation bubbles induced by Er,Cr:YSGG laser were visualized with high temporal and special resolution in a water environment and in glass models of root canals using silica tips of 200, 320, and 400 μm diameter. A thermal imaging technique was combined with thermocouples to measure the temperature increase in the canal wall. Results: In water, the cavitation bubbles were reproducible. The relationship between pulse energy and dimensions of the bubble is linear. However, the dynamics of cavitation bubbles in the root canal model is complex. The cavitation effects exist for a much longer period of time and there is a turbulent mixture with air or gas bubbles. Colored dyes show very fast fluid motion in and out of the canal during laser exposure. The temperature increase measured was only 5 to 10 degrees. Conclusion: Our imaging suggests that the working mechanism of an Er,Cr:YSGG laser in root canal treatment can be attributed to cavitation effects inducing high speed fluid motions into and out of the canal. This might effectively remove the smear layer and sterilize the canal wall. The thermal component is moderate.
Keywords: laser, cavitation, endodontics, Er,Cr:YSGG, fluid dynamics