Eficácia de substâncias modificadoras da superfície no reestabelecimento da capacidade adesiva de zircônia parcialmente estabilizada com ítrio (4Y-PSZ) após jateamento

Abstract

Yttrium-stabilized tetragonal polycrystalline zirconia (Y-TZP) is widely used due to its mechanical strength and chemical stability, while translucent yttrium-partially stabilized zirconia (4Y-PSZ) is preferred for its high translucency. However, both materials face adhesion challenges, as their surfaces hinder interaction with resin-based materials. Sandblasting with aluminum oxide (Al2O3) particles, followed by the application of primers containing functional monomers like 10-methacryloyloxycyl dihydrogen phosphate (10-MDP), is commonly used to enhance wettability, surface energy, and chemical bonding with zirconium oxides (ZrO2). However, the pressure exerted by sandblasting can induce crystallographic phase transformations, and the adhesion can be affected by the time between sandblasting and cementation due to surface contamination. Thus, this study investigated the effect of surface-modifying potential substances (SMPS), such as hydrofluoric acid (HF) and sodium hypochlorite (SH), applied at different intervals after sandblasting, on the bond strength, wettability, and phase transformation of 4Y-PSZ obtained by CAD/CAM. 4Y-PSZ blocks (10 x 10 x 3 mm) were sandblasted with Al2O3 and treated with ceramic primer (CP, control), HF+CP, or SH+CP after intervals of 10 min. (CP.10, HF.10, and SH.10), 24h (CP.24, HF.24, and SH.24), and 72h (CP.72, HF.72, and SH.72). Additionally, other 4Y-PSZ blocks served as intragroup controls (CP.0, HF.0, and SH.0). Composite resin cylinders (ø5 x 6 mm) were cemented and stored at 37°C for 48h. Bond strength was measured by shear test (SBS, n=9), wettability by contact angle (in degrees, n=8), and phase transformation by Raman spectroscopy (n=1). Sandblasting increased SBS (T0 vs. T10) in the CP and SH groups (p<0.05) but not in the HF group (p>0.05). After 72h, SBS decreased in the CP (CP.10 > CP.72) and SH groups (SH.10 = SH.24 > SH.72), but remained stable in the HF group (HF.10 = HF.24 = HF.72). Sandblasting also improved wettability up to 24h (T0 vs. T10 vs. T24), after which it stabilized in the CP and HF groups (T24 vs. T72). Raman spectroscopy revealed monoclinic crystals after sandblasting, with an increase in CP after 72h (CP.10 = CP.24 < CP.72), a decrease in HF (HF.10 = HF.24 > HF.72), and stability in SH (SH.10 = SH.25 = SH.72). HF acid was effective in improving wettability and stabilizing SBS in 4Y-PSZ, showing good performance as an SMPS regardless of sandblasting. This suggests that HF can be used either up to 72 hours after sandblasting, maintaining adhesive strength, or directly without sandblasting, without compromising phase transformation.