Abstract: Objective: To explore the changes of shear bonding strength (SBS) and surface morphology of the bonding surface between leucite glass ceramic and resin after Er:YAG laser treatment and expound the influence of Er:YAG laser treatment with different powers as preconditioning method on the bonding strength of the bonding surface of ceramic restoration, and to provide the reference for the clinical application. Methods: The IPS Empress CAD glass ceramic blocks were prepared into 84 ceramic samples with 7 mm×6 mm×3 mm, and randomly divided into control group, acid etching group, 2 W laser group, 4 W laser group, 6 W laser group, 8 W laser group and 10 W laser group according to different surface treatment methods(12 samples in each group). Except for control group,surface treatment was carried out on the samples of other groups; the samples in acid etching group were treated with 9.5% hydrofluoric acid, and the samples in 2 W laser group, 4 W laser group, 6 W laser group, 8 W laser group and 10 W laser group were treated with Er:YAG laser with power of 2, 4, 6, 8 and 10 W, respectively. After the surface treatment of the samples was completed, 10 samples from each group were selected and tested by an electronic universal testing machine to detect the SBS values of the treated surface after bonded with the resin, and then the adhesion failure mode was observed by an optical stereoscopic microscope. Scanning electron microscope (SEM) was used to observe the surface morphology of the other two samples in each group. Results: Compared with control group, the SBS values of samples in other groups were all increased (P<0.01). The SBS values of samples in 2 W laser group, 4 W laser group, 6 W laser group, 8 W laser group and 10 W laser group were successively increased, and there were significant differences between various groups (P<0.01). Compared with acid etching group, the SBS values of samples in 2 W laser group, 4 W laser group, 6 W laser group and 8 W laser group were all decreased (P<0.01), and the SBS value of sample in 10 W laser group had no statistically significant difference (P>0.05).The failure mode observation showed that the failure modes of each group were mainly adhesive failures, occasionally mixed failures, and no cohesive failures. The SEM results showed that the surface of samples in control group was smooth and unchanged; many irregular grooves with different depthes were found in the surface of samples in acid etching group, presenting an obvious honeycomb structure; in 2 W laser group, the pits formed by the peeling of porcelain layer in a small range were observed; in 4 W laser group, the area and depth of pits of samples were increased; in 6 W laser group, continuous bulk peeling was observed; in 8 W laser group and 10 W laser group, the number of pits in surface of the samples was increased, presenting an obvious scale-like appearance. Conclusion: With the increase of the irradiation power of Er:YAG laser, leucite glass ceramic and resin show a gradually increasing bonding strength and a gradually rough surface morphology change. When the laser power reaches 10 W, the effect is similar to that of hydrofluoric acid treatment.

Key words: Er:YAG laser, leucite, glass ceramic, bonding strength