Innovations in bonding to zirconia-based materials. Part II: Focusing on chemical interactions

ObjectivesThe zirconia–resin bond strength was enhanced using novel engineered zirconia primers in combination with selective infiltration etching as a surface pre-treatment. The aim of this study was to evaluate the effect of artificial aging on the chemical stability of the established bond and to understand the activation mechanism of the used primers.MethodsSelective infiltration etched zirconia discs (Procera; NobelBiocare) were coated with one of four novel engineered zirconia primers containing reactive monomers and were bonded to resin-composite discs (Panavia F2.0). Fourier transform infrared spectroscopy (FT-IR) was carried out to examine the chemical activation of zirconia primers from mixing time and up to 60 min. The bilayered specimens were cut into microbars (1 mm² in cross-section area) and zirconia–resin microtensile bond strength (MTBS) was evaluated immediately and after 90 days of water storage at 37 °C. Scanning electron microscopy (SEM) was used to analyze the fracture surface.ResultsThere was a significant drop in MTBS values after 90 days of water storage for all tested zirconia primers from ca. 28–41 MPa to ca. 15–18 MPa after completion of artificial aging. SEM revealed increase in percentage of interfacial failure after water storage. FTIR spectra suggested adequate activation of the experimental zirconia primers within 1 h of mixing time.SignificanceThe novel engineered zirconia primers produced initially high bond strength values which were significantly reduced after water storage. Long-term bond stability requires developing more stable primers.