The Impact of Various Surface Treatments on Adhesion Between Co–Cr Alloy and Acrylic Teeth

Abstract

Objective: This study aimed to assess the shear bond strength (SBS) between cobalt–chromium (Co–Cr) alloy and acrylic resin teeth using various surface conditioning methods and to investigate the failure modes associated with these methods. Materials and Methods: A total of 53 Co–Cr specimens were fabricated and randomly assigned to five groups (n = 10 per group) based on the type of surface treatment: (1) polymethyl methacrylate (PMMA; control group), (2) Clearfil Ceramic Primer Plus + PMMA, (3) M&C Primer + PMMA, (4) Super-Bond Universal, and (5) M&C Primer + Super-Bond Universal. Each specimen was subsequently bonded to an acrylic resin tooth. Three specimens from both the control and primer-treated groups were reserved for scanning electron microscopy (SEM) analysis. All samples were stored in distilled water at 37 ± 1°C for 24 h before SBS evaluation with a universal testing machine. Statistical Analysis: Statistical analysis was performed using one-way analysis of variance (ANOVA) followed by Tukey’s HSD post hoc test. Results: A statistically significant difference in bond strength was observed among the experimental groups (p < 0.05), with the Super-Bond Universal group exhibiting the highest bond strength (8.01 ± 1.05 megapascals [MPa]), compared to the control group (3.07 ± 0.48 MPa). The control group and the PMMA + M&C Primer group exhibited predominantly adhesive failures, while the other groups showed a combination of adhesive and mixed failures. Conclusion: Super-Bond Universal without primer achieved the highest bond strength, and the application of primers prior to PMMA or resin cement placement significantly improved bonding between Co–Cr alloys and acrylic resin teeth, suggesting that appropriate surface conditioning can enhance denture repair outcomes.