Zirconia surface modification by a novel zirconia bonding system and its adhesion mechanism.

OBJECTIVE: Bonding to zirconia has been of great interest over the last 10-15 years. The aim of this study was to develop a zirconia bonding system and clarify its adhesion mechanism. METHODS: A zirconia primer was prepared using tetra-n-propoxy zirconium (TPZr) and water. A silane primer was also prepared using gamma-methacryloyloxypropyltrimethoxysilane (gamma-MPS) and hydrochloric acid. After the zirconia primer was applied to the oxidized zirconia surface, the silane primer was applied to the ZrO(2)-functionalized layer and the resin cement was applied to the silane-modified layer. Ceramic Primer II was used as a typical MDP-based ceramic primer. Shear bond strengths were measured using a universal testing machine. To clarify the enhancing mechanism of the zirconia bonding system, X-ray photoelectron spectroscopy (XPS) analyses were performed. RESULTS: The zirconia bond strength was affected by the surface wettability of zirconia, and the compositions of TPZr and water utilized in the zirconia primer. When the zirconia primer, consisting of 10muL TPZr and 13muL water, was applied to the zirconia surface that had been oxidized by H(2)O(2) above 10%, the maximum bond strength of 8.2MPa was obtained. The mechanism of the zirconia bonding system was established as follows: the hydrolyzed zirconium species formed a more reactive ZrO(2)-functionalized layer on the oxidized zirconia surface, and the hydrolyzed gamma-MPS species adsorbed on that layer introduces a chemical bonding to the resin. SIGNIFICANCE: The novel zirconia bonding system enhanced the bonding performance of the resin, and showed a greater bond strength than an MDP-based ceramic primer.