Effectiveness of Various Cleaning Protocols in Enhancing Resin–Zirconia Bond Strength After Saliva Contamination

Background: This study evaluated the influence of various decontamination protocols after salivary contamination on the micro-shear bond strength (µSBS) between monolithic high-translucency zirconia and resin cement. Methods: A total of 81 multilayer (ML) monolithic–translucent zirconia discs of 10 mm diameter and 2 mm thickness (DD cubeX2 ML, Dental Direkt) were fabricated, sintered, and polished using silicon–carbide papers. The bonding surfaces were treated with 50-μm Al2O3 using a Renfert sandblaster at 0.3 MPa for 20 s. Fifty samples were randomly assigned to five groups (n = 10). A control group consisted of clean, uncontaminated samples, while the other four groups were contaminated and cleaned using water, sodium hypochlorite, phosphoric acid + ethanol, or Ivoclean, respectively. Resin cement cylinders (Panavia V5, Kuraray Noritake) were bonded onto the zirconia surfaces. The µSBS was evaluated after simulated ageing using a universal testing machine. Failure modes were analysed by light microscopy. Surface morphology was evaluated using a field emission scanning electron microscope (SEM), and the chemical surface was assessed with X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared (FTIR) Spectroscopy. Surface wettability was assessed through contact angle measurements. One-way ANOVA with Tukey’s HSD was used to compare µSBS between groups. Results: Among the tested groups, the control group exhibited the highest µSBS value (59.5 ± 4.2 MPa), followed by Ivoclean (56.7 ± 4.8 MPa), phosphoric acid + ethanol (46.8 ± 4.7 MPa), and sodium hypochlorite (41.1 ± 5.7 MPa), with the lowest value observed with water (33.5 ± 6.3 MPa). All groups exhibited adhesive failure, with no sign of cohesive or mixed failures. SEM analysis showed no effect on zirconia crystallinity or sandblasting, while Ivoclean left residual zirconium oxide particles. Furthermore, XPS and FTIR analysis revealed favourable chemical changes after Ivoclean treatment, correlating with improved bonding performance. Contact angle measurements confirmed greater surface wettability in the Ivoclean group, resulting in strong bond strength. Conclusions: Ivoclean significantly increased the resin–zirconia bond strength after saliva contamination, showing more reliable results compared to others. Phosphoric acid + ethanol showed the second-highest mean strength, while water showed the least effectiveness.