Effect of acidic primers on bonding between stainless steel and auto-polymerizing methacrylic resins

Objectives: The purpose of this study was to evaluate the effect of acidic primers on bonding between methacrylic resins and SUS 316 stainless steel. Methods: The primers were single liquid metal conditioners containing either a phosphate monomer (Cesead opaque primer, CO; Metal primer, MP) or a carboxylic monomer (Super-Bond liquid, SB; Acryl bond, AB; MR bond, MR). Disk metal specimens were air-abraded with alumina followed by priming. The disks were bonded with a methacrylic resin using a brush-dip technique (Super-Bond C & B, CB or Repairsin, RE). Specimens were thermocycled in water and bond strengths were determined. Results: Shear bond strengths after the thermocycling were 11.9 MPa for CO---CB, 7.6 MPa for CO---RE, 4.9 MPa for SB---RE, 3.9 MPa for MP---RE, 3.3 MPa for AB---RE, 2.5 MPa for MR---RE, 1.9 MPa for None-CB, and 0 MPa for None-RE. The two systems primed with CO primer showed greater bond strengths than the other groups (P < 0.05). Of the two systems conditioned with CO primer, CB resin demonstrated higher value bond strength as compared with RE resin (P < 0.05). Conclusion: Among the systems examined, CO primer used together with CB resin exhibited greater bond strength to SUS 316 stainless steel than other systems after the ageing test. Reduction in bond strength by thermocycling, however, was remarkable for all groups.