Effects of primers containing sulfur and phosphate monomers on bonding type IV gold alloy

Objective The purpose of the present study was to evaluate the effect of five primers (two sulfur, one phosphate, and two sulfur–phosphate dual-function primers) on the bond strength between a self-curing luting agent and gold–copper–silver (Au–Cu–Ag) alloy. Methods The primers used were two sulfur primers (V-Primer and Metaltite), one phosphate primer (Epricord), and two primers which contained a sulfur monomer and a phosphate monomer (Alloy Primer and Metaltite/Epricord). The surface of Au–Cu–Ag specimens were blasted with alumina, and then bonded with acrylic rods using a tri-n-butylborane-initiated self-curing luting agent. Shear bond strengths were determined after 5000 thermocycles. An additional alumina-blasted Au–Cu–Ag alloy specimen was subjected to X-ray photoelectron spectroscopy (XPS) analysis. Results The maximum shear bond strengths were obtained with Metaltite/Epricord (29.6 ± 2.3 MPa) and Alloy Primer (23.0 ± 1.6 MPa), followed by Metaltite (10.3 ± 4.2 MPa), V-Primer (8.9 ± 0.6 MPa), Epricord (6.4 ± 1.5 MPa), and No primer control (2.0 ± 0.5 MPa). The XPS analysis detected six chemical elements (Au, Cu, Ag, Al, O, and C) on the Au–Cu–Ag alloy. In addition to pure Au element, the metal oxide-states of Ag2O, AgO, Cu2O, and CuO were suggested. Conclusion The combined use of a sulfur monomer and a phosphate monomer significantly improved the bond strength of resin to Au–Cu–Ag alloy which should be especially significant to clinicians.