COMPOSITION, REACTIVITY AND SURFACE INTERACTIONS OF 3 DENTAL SILANE PRIMERS

Three commercially available dental silane primers, two single-phase p rehydrolyzed and one two-component system were investigated for their composition, extent of hydrolysis, surface interactions, bond strength and interfacial topography when used on three representative porcelai n alloys (Au-Pd, high-Pd, Ni-Cr). Five tests, H-1 FT-NMR, FTIR, GPC, E SCA and EPMA, were used to determine the composition and the surface i nteraction profiles. Shear tests were performed to assess the bond str ength values. According to the results, all the primers contain gamma- methacryloxypropyltrimethoxysilane (gamma-MPTS) at concentrations of 1 .15-18.86 g/100 mL, two in ethanol and one in isopropanol. Traces of a cetic acid were found in the prehydrolyzed primers. All the primers de monstrated partial hydrolysis of the methoxy groups. Prehydrolyzed pri mers exhibited a higher rate of hydrolysis and better orientation of h ydrolyzed methoxy groups towards the Ni-Cr alloy surface. Due to the e xtent of surface oxidation, the Ni-Cr alloy provided more bonding site s for silanols than the other two types of alloys. The Ni-Cr alloy dem onstrated the highest shear bond strength values on smooth surfaces re gardless of the type of primer used. The results of the present study suggest that active prepolymerized primers may provide significant adv antages over two-component systems in the repair of Ni-Cr porcelain fr actures involving removal of the metal oxide layer.