Primer for bonding resin to metal

Objectives. The purpose was to examine the effect on the bond strength and durability of a resin bond to metal of modification of a primer consisting of thiophosphoric methacrylate with phosphoric methacrylates and/or benzoyl peroxide. Methods. Acrylic rods were bonded with a luting resin consisting of poly(methyl methacrylate) powder and a mixture of methyl methacrylate and tributylborane initiator to silver-palladium alloy (Ag---Pd), gold-silver alloy (Au---Ag), cobalt-chromium alloy (Co---Cr), and titanium (Ti) surfaces treated with various primers. The bonded samples were thermocycled for 2,000 cycles and the mean bond strengths were compared using one-way ANOVA and Duncanʹs new multiple range test at p < 0.05. Results. Using primers of thiophosphoric methacrylate or phorphoric methacrylates alone, the bond strengths of Ag---Pd decreased significantly (p < 0.05) after thermocycling. The durability was significantly improved (p < 0.05) when thiophosphoric methocrylate was used in combination with the phosphate monomers. The additional use of benzoyl peroxide and heat treatment resulted in a significant increase (p < 0.05) in the durability of two groups; the mean bond strengths over 20 MPa and the lowest values remained unchanged even after 2,000 thermocycles. Significance. The highest level of bond strength and durability of dental noble metals was achieved using a mixture of thiophosphoric and phosphoric methacrylates and benzoyl peroxide. These bond strength results are comparable to values obtained for base metals.