Durability of resin bond strength to dental noble metal–ceramic alloys conditioned with novel mercapto silane-based primer systems

The purpose of this study was to investigate the efficacy of novel mercapto silane-based experimental primers on the resin bonding and its durability to dental noble metal–ceramic alloys in comparison with that of commercial primers. Disc-shaped gold–platinum–palladium, gold–palladium–silver, and palladium–silver alloy specimens were used as the adherents after air-abrasion. One of three commercial primers (M.L. Primer, Single Bond Universal, and All-Bond Universal) and two experimental primer systems (2-step application with γ-mercaptopropyltrimethoxysilane and then γ-methacryloxypropyltrimethoxysilane and a blend of the two silanes) was applied to each alloy. Resin cylinders with a diameter of 2.38 mm were bonded to the surfaces and light-cured. All bonded specimens were stored in water at 37 °C for 24 h and then half of them additionally water immersed for 7 days (37 °C) and then thermocycled 10,000 times before the shear bond strength test (n = 10). The surface energy parameters for unprimed and primed alloy surfaces were calculated based on the contact angle measurements. The bond strength data were non-parametrically analyzed at α = 0.05. Regardless of the alloy type, both mercapto silane systems equally and consistently showed superior bonding durability to the commercial primers. Pearson correlation analyses revealed moderate to strong, significant correlations between the surface energy parameters and the bond strength values. The two novel mercapto silane systems are a promising alternative for enhanced durability of resin bonding to dental noble metal–ceramic alloys.