الفهرس 
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Abstract
This in vitro study was designed to evaluate effect of surface treatment modalities on the surface characteristics and shear bond strength of a repair composite to two ceramic materials. Materials and Methods: a total of seventy samples were divided, n=35 samples from each material ZLS (group S) and PICN (group E). According to the manufacturer’s recommendation (group S) was subjected to crystallization, polishing and then glazing. While, (group E) subjected to polishing. Each group will then be subdivided into five subgroups according to the surface treatment techniques into: (Subgroup 1): hydrofluoric acid, (Subgroup 2) Er:YAG laser treatment, (Subgroup 3) Er,Cr:YSGG laser treatment, (Subgroup 4) Er:YAG laser treatment+ airborne particle abrasion (Subgroup 5) Er,Cr:YSGG laser treatment+ airborne particle abrasion.
Surface roughness after each surface treatment was then measured. Scanning electron analysis to evaluate surface topography then wettability was measured. Bonding of the samples was done according to the manufacturer instruction. The shear bond strength was measured using a universal testing machine and failure mode assessed.
Statistical analysis was performed, two-way ANOVA followed by Tukey’s post hoc test were used to compare the effects of different surface treatment techniques on tested material types.
Results: Regarding the surface roughness of Vita Suprinity samples of different surface treatments, Er,Cr:YSGG laser+ airborne particle abrasion showed the highest value. Followed by HF acid etching and Er:YAG laser
+ airborne particle abrasion, which has no significant difference between them. While the lowest value was found in Er:YAG laser treatment. For Vita Enamic surface roughness Er:YAG + airborne particle abrasion showed the highest value. Followed by Er,Cr:YSGG laser+ airborne particle abrasion and HF acid etching, which has no significant difference between them. While the lowest value was found in Er,Cr:YSGG laser treatment. High surface roughness of different surface treatments indicates decrease contact angle which improves wettability. As for shear bond test of Vita Supernity, the highest value was found in HF acid etching, followed by Er,Cr:YSGG laser treatment + airborne particle abrasion which has no significance difference between them, and then Er,Cr:YSGG laser treatment. While the lowest value was found in Er:YAG laser treatment+ airborne particle abrasion. For Vita Enamic shear bond test, Er:YAG + airborne particle abrasion surface treatment showed the highest value, followed by HF acid etching which has no significance difference between them, and then Er:YAG laser. While the lowest value was found in Er,Cr:YSGG laser + airborne particle abrasion. For mode of failure analysis of Vita Supernitiy, samples treated with Er:YAG having higher percentage of adhesive failure and a lower percentage of samples with mixed failure mode in comparison to samples treated with HF and Er,Cr:YSGG + AA. While for mode of failure analysis of Vita Enamic samples treated with HF and Er:YAG + AA having higher percentage of samples with mixed failure mode and a lower percentage of samples with adhesive failure mode in comparison to samples treated with Er,Cr:YSGG and Er,Cr:YSGG + AA.