Enhancing resin-zirconia bonding: Influence of decontamination strategies on saliva-contaminated high-translucent zirconia.

Purpose: To evaluate the effect of different decontamination protocols on the bonding strength of MDP-containing resin cement to saliva-contaminated zirconia ceramic.

Methods: 144 zirconia samples (12 mmx12 mmx1.2 mm) were prepared from 4Y-TZP and 6Y-TZP blocks, sandblasted with 50 μm Al₂O₃, and contaminated with artificial saliva. Samples were divided into six groups (n=24) based on decontamination method: sintered (CON), Rocatec-treated (ROC), Al₂O₃ abraded (AL), water-cleaned (HO), Ivoclean-treated (IVO), and 37% H₃PO₄-cleaned (PH). Pre-prepared resin cylinders (2.0 mm diameter, 3.0 mm height) were bonded to zirconia using MDP-containing resin cement (Panavia SA) and light-cured. All bonded samples underwent thermocycling (5°C-55°C, 10,000 cycles for 1 week, 50,000 cycles for 6 months, and 100,000 cycles for 12 months) to simulate intraoral aging. Shear bond strength was assessed at 1 week, 6 months, and 12 months using a universal testing machine. Surface roughness parameters (Rq, Ra) were measured with a digital profilometer, and adhesive failures were analyzed via scanning electron microscopy (SEM). Data were evaluated using one-way ANOVA and Tukey's post hoc test (α= 0.05). Weibull analysis was performed to assess the reliability and probability of bond strength failure. Additionally, Kaplan-Meier survival analysis was conducted to evaluate the long-term durability of resin-zirconia bonds over time.

Results: For 4Y-TZP, Ivoclean (1768±32 MPa) and Al₂O₃ abrasion (1541±36 MPa) achieved the highest shear bond strengths at 1 week. In contrast, 6Y-TZP exhibited lower bond strengths, with sintered and Rocatec-treated groups performing moderately. Surface roughness analysis showed that sintered and Ivoclean-treated 4Y-TZP had lower roughness (Rq ~14.8, Ra ~0.5), while 6Y-TZP had higher values, particularly after H₃PO₄ treatment (Rq 61.6, Ra 119.7).

Clinical Significance: Selecting appropriate decontamination methods such as Ivoclean application or airborne-particle abrasion with Al₂O₃-based on the zirconia type is essential to achieve durable resin bonding and ensure the long-term success of high-translucency zirconia restorations.