Long-term microtensile bond strength of surface modified zirconia.

Objective: To compare long-term microtensile bond strength of zirconia, surface-modified via a novel treatment, to current surface conditioning methods for zirconia, when resin bonded to dental composite.

Methods: Two ProCAD (porcelain) and 10 sintered ZirCAD (ZrO(2)) blocks (18 mm × 14 mm × 12 mm) were obtained from manufacturers. Twelve Herculite XRV composite blocks were fabricated (18 mm × 14 mm × 12 mm). Bonding surface of blocks was polished through 1200-grit SiC and air-abraded (50 μm alumina, 0.28MPa, 20s). Blocks were then separated into six groups: (1) porcelain (control), HF-etched/silane-treated, (2) ZrO(2), tribochemical-coated/silane-treated, (3) ZrO(2), primer-treated, (4) ZrO(2), modified via novel 3.2 nm silica layer/silane-treated, (5) ZrO(2), modified via novel 5.8nm silica layer/silane-treated, and (6) ZrO(2), modified via novel 30.4 nm silica layer/silane-treated. Blocks were bonded to composite using Clearfil Esthetic cement. Blocks were stored in distilled water (37°C, 24h), then cut into microtensile bars (n=8/gp), then bond strengths were measured using a universal testing machine at 0, 1, 3, and 6 months. All groups were statistically analyzed (ANOVA, Tukey's, p<0.05).

Results: At 6 months (aging), all silica seed layer specimens displayed microtensile bond strength similar to CoJet specimens but less than that of silane-modified dental porcelain.

Conclusion: The deposition of a silica layer on zirconia resulted in similar or superior long-term resin bond strength when compared to traditional silanation and bonding techniques for zirconia but lower than that for silane-treated dental porcelain.