Resin Bonding to Type IV Gold Alloy Conditioned with a Novel Mercapto Silane System: Effect of Incorporation of a Phosphate Monomer

Self-assembled monolayers of thiols have been used to link a range of materials to planar gold surfaces or gold nanoparticles in nanoscience and nanotechnology. Novel mercapto silane systems are a promising alternative to dental noble metal alloys for enhanced resin bonding durability Goldbased alloys for full-cast restorations contain various base metal elements, which may bond to acidic functional monomers chemically, in addition to noble metal elements. This study examined how the additional incorporation of a phosphate monomer (di-2-hydroxyethyl methacryl hydrogenphosphate, DHP) into novel mercapto silane primer systems affected the resin bond strength to a type IV gold alloy pretreated with the primers. One of three commercial primers (Alloy Primer and M. L. Primer) and three experimental primer systems ((1) blend of γ-mercaptopropyltrimethoxysilane (SPS) and γ-methacryloxypropyltrimethoxysilane (MPS) (both 1.0 wt%), (2) 1.0 wt% DHP-containing primer, and (3) blend of SPS, MPS, and DHP (each 1.0 wt%)) was applied to the alloy surfaces after sandblasting. Resin cylinders (diameter: 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 thermocycled 10,000 times before the shear bond strength test (n = 10). The mercapto silane systems (SPS + MPS) were found to show superior resin bonding durability to the commercial primers and the only DHP-containing primer, regardless of additional incorporation of the phosphate monomer.