Effect of water spray during laser ablation on dental hard tissue

摘要

In this study, we investigated the role of water spray. To ablate human enamel tissue, a long-pulsed Er,Cr:YSGG laser was used at various radiant exposures. During dental ablation, distilled water was sprayed to the sample surface. Desiccated samples were also tested with direct irradiation for comparison. In order to identify dominant ablation mechanisms, transient acoustic waves were measured using a piezoelectric microphone. Enamel ablation efficiency was evaluated with Optical Coherence Tomography (OCT). Material removal was up to four times larger at the best flow rate with respect to ablation without spray. In spite of 60 % higher damage threshold by water absorption, spray ablation enhanced both the laser-induced acoustic transients up to six times and the ablation efficiency up to twice over the entire range of radiant exposures tested, compared to dry ablation. The improved pressure and ablation performance of the spray-assisted process with cooling effect were thought to be induced by recoil stress, rapid water vaporization, interstitial water explosion, and/or liquid-jet formation. Spray ablation along with water cooling and abrasive mechanical effects can be a safe and efficient modality for dental treatment.