Fluid flow analysis of laser-activated irrigation in the simulated root canal

Aim: The aim of the study was to evaluate the efficacy of laser-activated irrigation, the streaming pattern, and its relevance to laser-induced bubbles in a transparent simulated root canal. In addition, the effects of tip position on irrigant flow were examined. Materials and Methods: Particle image velocimetry with a high-speed camera was used, which enabled tracking of buoyant tracer movement. Recorded images were analyzed using two-dimensional fluid analysis software. The tip of an erbium: yttrium aluminum garnet (Er:YAG) laser was placed either in the coronal chamber or in the root canal. Results: On laser irradiation within the coronal chamber, rapid streaming appeared in the entire root canal immediately after the advent of the vapor bubble. Peak flow velocity was observed when the vapor bubble grew to peak size. In contrast, when the tip was placed in the root canal, rapid streaming was related to the appearance of secondary cavitation bubbles and confined to the apical region. Conclusion: The streaming pattern in laser-activated irrigation was affected by the tip position in the root canal. In addition, there was a close relation between the formation of laser-induced bubbles and rapid streaming.