The use of zirconia for fabricating indirect restorations has become increasingly common due to its superior mechanical properties. However, this material presents poor bonding to resin-based luting agents. In an attempt to overcome these issues, the present study aims to evaluate a new method of functionalization of the surface of Y-TZP and Y-PSZ zirconia with 3-aminopropyltrimetoxisilane (APTMS) after new surface treatments with a method of TiO2 nanofilm formation in sintered ceramic surfaces and two methods of application of TiO2 nanotubes in presintered surfaces. One hundred forty slices of zirconia will be prepared and divided according to the type of ceramic, surface treatment, and functionalization. For the method of TiO2 nanofilm formation, a sol-gel solution containing TiO2 will be applied over sintered zirconia surfaces with a spin-coating technique. Additionally, surfaces will be thermally treated for maturation and growth of the nanostructure. For the other two surface treatments, TiO2 nanotubes will be produced through alkaline synthesis, mixed with isopropyl alcohol and applied over the presintered zirconia slices. After the application, the slices will be sintered in a zirconia oven. All modified ceramics will be characterized by contact angle and surface energy analyses, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Bond strength will be evaluated by microshear with a universal testing machine after 10,000 thermocycling cycles. Resin composite cylinders will be cemented on zirconia slices after surface treatments and functionalization. Resin composite cylinders will be cemented with a dual-cured resin cement and the light activation will be performed with the light source positioned below the ceramic. Data will be submitted to normality and homogeneity tests, followed by ANOVA and Tukey tests in case of normal distribution or by Kruskal-Wallis and Dunn tests in case of non-normal distribution. The results will be evaluated at a level of significance of 5% (±=0.05).
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