Cavity Preparation with Er,Cr:YSGG Laser and Composite Resin Restoration

Abstract

We have examined the mechanism of laser cutting for enamel and dentin, the effect of the ratio of water to air in the water spray on the efficiency of laser cutting, SEM analysis of laser-cut tooth surface and its alteration after applying various adhesive systems, the effect of various adhesive systems on the bond strength of composite resin to laser-cut enamel or dentin, the adaptation of composite resin to laser-prepared cavities, and the effect of laser preparation and adhesive system on pulp reaction using an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser. From these studies, the following results were obtained. High-speed camera observation clarified that micro-phreatic explosion occurred on the tooth surface during laser irradiation. The ratio of water to air in the spray influenced the efficiency of the laser cutting for dentin. A thin heat denaturation layer was observed on the surface of the dentin prepared with the laser, but this layer disappeared after application of both 40% phosphoric acid and 10% sodium hypochlorite. Pre-conditioning using phosphoric acid or both phosphoric acid and sodium hypochlorite was effective in improving the bond strength of two-step self-etch adhesive system to both enamel and dentin prepared with the laser. Pretreatment of the cavity prepared with the laser using phosphoric acid or sodium hypochlorite did not affect the dental pulp healing of rat tooth.