Shear bond strength and SEM evaluation of composite bonded to Er:YAG laser-prepared dentin and enamel

Objectives. The purpose of this study was to evaluate dentin and enamel bond strength to resin composite following high-speed rotary or Er:YAG laser preparation using a total etch adhesive system. The microstructure of resin–tooth interfaces was also investigated. Methods. Human dentin and enamel specimens were prepared with a high-speed handpiece (KaVo) or Er:YAG laser (DELight) at manufacturerʹs recommended settings and etched with either 37% H3PO4, laser etched, or not etched. Composite rods (Z-250, 3M/ESPE) were bonded to specimens with an adhesive (Adper Scotchbond Multi-Purpose, 3M/ESPE). After thermocycling, specimens were tested in shear to failure. Results. Two-factor ANOVA detected significant differences in the main effects of preparation and etch type, and interaction (p<0.001). Post hoc analyses showed that in both dentin and enamel, only the acid-etched specimens had significantly higher mean bond strengths, with rotary-prepared specimens having significantly higher mean bond strengths versus laser prepared specimens. Within each preparation type, in both dentin and enamel, acid etch was better than laser etch, and laser etch was better than no etch. Scanning electron microscopy of laser-ablated specimens demonstrated significant surface scaling and subsurface fissuring beyond normal resin penetration depth. Significance. Adhesion to laser-ablated or laser-etched dentin and enamel was inferior to that of conventional rotary preparation and acid etching.