Surface treatments with TiO2 nanostructures for bonding to zirconia materials as an alternative to conventional airborne-particle abrasion of the surface

Zirconia has become a popular choice for indirect restorations; however, adhesion to this material remains a challenge. The present study aimed to evaluate surface characteristics and bond strength to tetragonal Y-TZP and cubic Y-PSZ zirconia submitted to experimental surface treatments. Specimens of Y-TZP (T) and Y-PSZ (P) were prepared and divided into groups: Tf-A) thin TiO₂ film functionalized with 3-(aminopropyl)trimethoxysilane (APTMS); Tf) thin TiO₂ film; MNt-A) manual application of TiO₂ nanotubes with APTMS; MNt) manual application of TiO₂ nanotubes; VNt-A) vacuum application of TiO₂ nanotubes with APTMS; VNt) vacuum application of TiO₂ nanotubes; C) control with Al₂O₃ sandblasting. Characterization with x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) was done. Bond strength was evaluated by microshear bond strength (µSBS). Data were analyzed by two-way ANOVA and Tukey’s HSD tests (α = 0.05). XPS showed signals for elements O 1 s, Ti 2p, and Zr 3d 5/2. In addition, high-resolution demonstrated Ti-O-Si and Zr-O-Si bonding for treatments with TiO₂ and APTMS for T-Tf-A/P-Tf-A. SEM presented a homogeneous film for T-Tf/T-Tf-A/P-Tf/P-Tf-A and cluster formations for all nanotube groups. Control groups for both Y-TZP and Y-PSZ showed clear surfaces. No differences of µSBS were seen between experimental surface treatments and the controls, except for T-MNt-A/T-VNt-A/P-MNt-A/P-VNt-A, which showed the lowest mean µSBS and highest incidence of pre-test failures. Surface treatments with TiO₂ nanostructures were effective in modifying the surface of both zirconia materials evaluated, providing strong covalent bonds, changes to the surface topology, and shear bond strength comparable to conventional sandblasting protocols.