Alkaline nanoparticle coatings improve resin bonding of 10-methacryloyloxydecyldihydrogenphosphate-conditioned zirconia

Abstract

Creating an alkaline environment prior to 10-methacryloyloxydecyldihydrogenphosphate (MDP) conditioning improves the resin bonding of zirconia. The present study evaluated the effects of four alkaline coatings with different water solubilities and pH values on resin bonding of MDP-conditioned zirconia. Two alkaline nanoparticle coatings were studied in particular. Thermodynamics calculations were performed to evaluate the strengths of MDP-tetragonal phase zirconia chemical bonds at different pH values. Zirconia surfaces with and without alkaline coatings were characterized by scanning electron microscope (SEM)/energy dispersive spectrometer and Fourier transform infrared spectroscopy; alkaline coatings included NaOH, Ca(OH)₂, nano-MgO, and nano-Zr(OH)₄. A shear bond strength (SBS) test was performed to evaluate the effects of the four alkaline coatings on bonding; the alkaline coatings were applied to the surfaces prior to conditioning the zirconia with MDP-containing primers. Gibbs free energies of the MDP-tetragonal zirconia crystal model coordination reaction in different pH environments were −583.892 (NaOH), −569.048 [Ca(OH)₂], −547.393 (MgO), and −530.279 kJ/mol [Zr(OH)₄]. Thermodynamic calculations indicated that the alkaline coatings improved bonding in the following order: NaOH > Ca(OH)₂ > MgO > Zr(OH)₄. Statistical analysis of SBS tests showed a different result. SBSs were significantly different in groups that had different alkaline coatings, but it was not influenced by different primers. All four alkaline coatings increased SBS compared to control groups. Of the four coatings, nano-Zr(OH)₄ and -MgO showed higher SBS. Therefore, preparing nano-Zr(OH)₄ or -MgO coatings prior to conditioning with MDP-containing primers may potentially improve resin bonding of zirconia in the clinic.

Keywords:

• adhesion
• T-YZP
• zirconia primer
• bond strength
• surface conditioning
• MDP

Acknowledgments

This study was supported by grants 81400539, 2016YFA 0201704 from National Natural Science Foundation of China, CSA-B2015-04 from Chinese Stomatological Association, 2014-37, 15KJB320003 from Jiangsu Higher Education Institutions, and grants BK20140913 and BK20150998 from Natural Science Foundation of Jiangsu Province.

Disclosure

The authors report no conflicts of interest in this work.