The Effect of Multiple-Time Applications of Metal Primers Containing 10-MDP on the Repair Strength of Base Metal Alloys to Resin Composite

This experimental study was performed to assess whether applying a metal primer containing 10-MDP multiple times affected the repair shear bonding ability of base metal alloys to resin composites. Ten base metal alloys were randomly assigned to each group in the manner described, following multiple applications of a metal primer (Clearfil Ceramic Primer Plus), namely one to five applications, and no primer application as a negative control. On the specimens’ prepared surfaces, the resin composite was pushed into the mold and then light-activated for 40 s. The bonded samples were kept for 24 h at 37 °C in distilled water in an incubator. The shear bond strength was determined using a universal testing device. A stereomicroscope was used to determine the debonded surface. The one-way ANOVA and Tukey’s test were implemented to statistically analyze. The lowest shear bond strength was found in group 6 (6.14 ± 1.12 MPa), demonstrating a significant difference (p = 0.000) when compared to groups 1 to 5. The shear bond strength of group 3 was highest at 21.49 ± 1.33 MPa; there was no significant difference between group 3 and groups 4 and 5 (20.21 ± 2.08 MPa and 20.98 ± 2.69 MPa, respectively) (p = 0.773, p = 1.000, respectively). All fractured specimens in groups 1, 2, and 6 were identified as adhesive failure. Groups 3 and 4 exhibited the highest percentage of mixed failures. To achieve the repair shear bonding ability of base metal alloys to resin composites, the sandblasted base metal alloys should be coated with three applications of a metal primer before applying the adhesive agent.