Incorporation of TiO₂ Nanotubes as a Surface Treatment for Y-TZP

Objectives: The objectives of the present study were to evaluate the addition of TiO₂ nanotubes into zirconia surfaces and the bond strength of a resin cement to modified ceramics.
Methods: TiO₂ nanotubes were produced by alkaline synthesis, mixed with Isopropyl alcohol (50wt%) and applied on pre-sintered zirconia disks (IPS e.max ZirCAD). The ceramics were sintered and surfaces were characterized by confocal laser microscopy, scanning electron microscopy (SEM), and EDS analysis. For the bond strength 6 groups (n=16) were evaluated: 1) without TiO₂ and Single Bond Universal; 2) with TiO₂ nanotubes and Single Bond Universal; 3) without TiO₂ nanotubes and Z-prime; 4) with TiO₂ nanotubes and Z-prime; 5) without TiO₂ and Signum Zirconia Bond; 6) with TiO₂ and Signum Zirconia Bond. After sintering, resin cement cylinders (RelyX Ultimate) with a diameter of 1.40 mm and 1 mm in height were prepared and polymerized for 20 seconds. Specimens were stored in water at 37°C for 30 days and submitted to shear test. The data were analyzed by two-way ANOVA and Tukey honest significant difference (α=5%).
Results: The nanotubes were incorporated in the zirconia surface and the EDS analysis has confirmed that nanoagglomerates were composed of TiO₂. The shear bond strength showed there were statistically significant differences among bonding agents (p < 0.001). There was no significant difference with the application of the nanotubes regardless of the analyzed group (p = 0.682). The interaction between the factors bonding agent and addition of nanotubes was significant (p = 0.025).
Conclusions: It was possible to incorporate nanotubes to the zirconia surfaces. However, this incorporation did not improve the bond strength. The association of zirconia with nanostructures could be a potential new method to improve the interaction between resin cement and Y-TZP ceramics at the adhesive interface.