Effect of Er:YAG laser pretreatment on glass-ceramic surface in vitro

This study investigated the feasibility of using an Er:YAG laser to pretreat glass-ceramic surface and evaluate the effect of the treatment on the bonding strength and marginal adaptation between glass-ceramic and dentin. Glass-ceramic samples (CEREC Blocs) and third molars were cut into 6 mm × 6 mm × 2 mm plates. Thirty ceramic plates were randomly divided into 5 groups: group A (control), group B (pretreated with 9.6% hydrofluoric acid [HF]), group C (pretreated with the Er:YAG laser at 300 mJ and 15 Hz), group D (pretreated with the Er:YAG laser at 400 mJ and 15 Hz), and group E (pretreated with the Er:YAG laser at 500 mJ and 15 Hz). The surface morphologies of the samples in each group were studied under a scanning electron microscope, and the sample displaying optimal etching parameters was selected for subsequent experiments. Based on the surface treatments, 30 ceramic and dentin plates were randomly allocated into 3 groups: the control, laser, and acid-etching groups. After bonding a ceramic plate to a dentin plate, the microleakage and bonding strength were measured, and the pretreatment effects of the Er:YAG laser and 9.6% HF were compared. Group E exhibited an etching effect that was more pronounced and uniform than that in groups C and D. Microleakage and bonding strength analyses revealed that the laser and acid-etching groups differed significantly from the control group in dye penetration depth and shear strength (P < 0.05), although the laser and acid-etching groups did not differ from each other. Both 9.6% hydrofluoric acid and Er:YAG laser pretreatments can coarsen glass-ceramic surfaces, improve the marginal adaptation and bonding strength between the glass-ceramic and dentin, and decrease microleakage of the materials. The two treatments showed no apparent differences in pretreatment outcomes.