Elucidation of the bonding mechanism of acidic and sulfur-based monomers to heat-treated copper-containing gold alloys

PURPOSE: To elucidate how the combination of acidic and sulfur-based monomers enhances bonding to oxidized noble metal alloy surfaces. METHODS: Two types of gold alloys were used: one with a low copper content (DG) and the other with a high copper content (IV). Three primers were used: a sulfur-based monomer primer (VP), a phosphate-based acidic monomer primer (PZ), and a combination of both (MC). Two conditions were used: heated and non-heated. The shear bond strengths before and after thermocycling were determined and compared for each condition. Surface chemical analysis was performed using X-ray photoelectron spectroscopy (XPS). RESULTS: After thermocycling, the bond strength of MC was significantly higher than that of the VP under all conditions. In the comparison of alloys under heating conditions, IV showed a significantly higher bond strength than that of DG for the PZ and MC groups. XPS revealed peaks attributed to copper oxide (CuO) formation on the heated IV surface. CONCLUSIONS: Multipurpose primers are effective for bonding oxidized noble metal alloys and acrylic resins. The formation of CuO improves the performance of 10-methacryloyloxydecyl dihydrogen phosphate, and its combination with sulfur-based monomers is particularly effective for noble metal alloy surfaces with high copper content.