Laser-Induced Plasma Activation: An Innovation To Enhance Endodontic Irrigation

This study aims to introduce an innovative endodontic irrigation method termed Laser-Induced Plasma Activation (LIPA), which uses far-field focusing nanosecond pulsed Nd:YAG laser to activate endodontic irrigants via laser-induced optical breakdown (LIOB), and preliminarily assesses its effectiveness and safety. A Q-switched Nd:YAG laser (10 ns pulse duration, 100 mJ/pulse, 8 Hz) was used to test eight irrigants, including 17% EDTA and 0.5%-5.25% NaClO solutions, with high-speed photography capturing plasma and cavitation bubbles. Particle image velocimetry was used to analyze flow fields in distilled water. The removal of the smear layer was analyzed on extracted teeth. Root surface temperature and transient apical peak pressure (TAPP) were measured for safety evaluation. Utilizing the LIPA method, plasma and cavitation bubbles were generated in all eight irrigants. The maximum flow velocity reached 13.66 m/s near cavitation bubbles and 0.50 m/s in the apical region of a simulated polydimethylsiloxane root canal. The smear layer was completely removed. The root surface temperature increased by less than 0.5℃, and the TAPP value was 4.97±0.51 kPa, showing no significant difference from needle irrigation (p>0.05). The LIPA technique employs the LIOB mechanism for liquid plasma conversion and cavitation bubble generation, differing from traditional laser-activated irrigation methods that create vapor bubbles through rapid heating and vaporization. This study offers preliminary evidence of LIPA's safety and efficacy, suggesting it as a promising, cost-effective advancement for endodontic irrigation.