Effect of MMA–PMMA resin polymerization initiators on the bond strengths of adhesive primers for noble metal

Objectives: This study was conducted to investigate the effect of MMA–PMMA resin polymerization initiators on the bond strengths of two adhesive metal primers by evaluating the shear bond strengths of resins to silver–palladium–copper–gold (Ag–Pd–Cu–Au) alloy. Methods: Three types of MMA–PMMA resins for which the polymerization initiators were TBB, BPO-amine and CQ-amine, and two adhesive primers, Metal PrimerII and V-Primer, were used. A brass ring placed over the nonprimed or primed casting alloy disk surface was filled with each resin. The half specimens were stored in water at 37°C for 24 h. In addition, another half specimens were then immersed alternately in water baths at 4°C and 60°C for 1 min each for 20 000 thermal cycles before shear mode testing at a crosshead speed of 0.5 mm/min. Results: There were no significant differences (p>0.05) in bond strength between the three types of resins with or without thermal cycling when Metal PrimerII was used. However, when Ag–Pd–Cu–Au alloy was primed with V-Primer, the bond strength of CQ-amine resin was significantly weaker than that of TBB resin. Metal PrimerII was more effective for enhancing the bond strength and the bond strength was not affected by thermal cycling, in contrast to V-Primer. Significance: The effectiveness of Metal PrimerII to enhance the bond strength is not influenced by polymerization mode of MMA–PMMA resin, in contrast to V-Primer when the resin is bonded to Ag–Pd–Cu–Au alloy.