Evaluation of silica-coating techniques for zirconia bonding.

Purpose: To evaluate silica-coating/silane treatment techniques for zirconia bonding.

Methods: 19 groups of zirconia disks were subjected to different surface treatments: polished or sandblasted by CoJet or alumina, and treatment with silane or zirconia primers (containing phosphate- or phosphonate-monomer). After surface treatments, the zirconia disks were cemented with resin cements and stored in deionized water for 2 hours at 370 degrees C prior to shear bond strength testing. Zirconia surface (polished and unpolished), CoJet sand, Cojet-treated zirconia surface (before and after water rinsing) and representative debonded surfaces were examined by scanning electron microscopy (SEM). The zirconia surface after silica-coating was examined by Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy.

Results: A non-phosphate-containing resin cement (Choice 2) had almost no bond strength on polished zirconia, while MDP-containing cements (Panavia F2.0) had mild bond strength. After zirconia was sandblasted with CoJet or alumina, bond strengths were slightly increased. Silane treatment did not increase bond strength, while phosphate/carboxylate-based primer (i.e. Exp Z-Prime) doubled the bond strengths. Silica nanoparticles identified by FTIR-ATR spectra, were observed by SEM on the zirconia surface after CoJet treatment. However, these nanoparticles were removed by forceful water stream.