Effect of 10-Methacryloxydecyl Dihydrogen Phosphate Concentration on Chemical Coupling of Methacrylate Resin to Yttria-stabilized Zirconia.

PURPOSE: To test the hypothesis that the concentration of 10-methacryloxydecyl dihydrogen phosphate (MDP) in zirconia primers has no effect on the chemical bonding efficacy of methacrylate resins to yttria-stabilized tetragonal zirconia (Y-TZP).
MATERIALS AND METHODS: Shear bond strength testing was performed to evaluate the efficacy of experimental primers containing 5, 10, 15, 20 or 30 wt% MDP (5M, 10M, 15M, 20M, 30M) in improving composite-zirconia bond strength. Bonding without use of MDP-containing primer served as the negative control (Ctr0). Bonding with a commercially available MDP-containing primer served as the positive control (CtrM). Thermogravimetric analysis (TGA), inductively coupled plasma-mass spectrometry (ICP-MS), x-ray photoelectron spectroscopy (XPS), Fourier transform-infrared spectroscopy (FT-IR), and computational simulation of infrared spectra were used to confirm the formation of Zr-O-P bond between MDP and Y-TZP.
RESULTS: Results derived from TGA, ICP-MS, XPS, and FT-IR suggested that MDP chemically bonded with Y-TZP. Simulation of IR data supported the FT-IR results. There was a higher concentration of phosphorus on the 10M-conditioned Y-TZP surface when compared with the other groups, suggesting bettter formation of Zr-O-P bond in the 10M group. Shear bond strengths were significantly lower for group 5M (p < 0.05), compared to groups 10M to 30M, which were not significantly different from one another (p > 0.05).
CONCLUSIONS: MDP improves resin bonding of zirconia through the formation of Zr-O-P bonds with zirconia. 10 wt% MDP appears to be the most optimal concentration for synthesizing zirconia primers for resin bonding.