Methods: 180 pairs of Nickel-Chromium alloy dumbbells were prepared and specimens were subjected to airborne-particle abrasion (50µm Al2O3 particles). The dumbbells were divided into 3 groups (n=30), which received one of the following treatment: sandblasted only (control group), sandblasted and Perform®-ID or sandblasted and sodium hypochlorite. All specimens were stored in distilled water at 37°C for 24 hours and half of the specimens were subsequently thermocycled (500 cycles, 5-55°C) before debonding using a universal testing machine. Tensile bond strength was recorded and data was analysed using two-way ANOVA and post-ANOVA Scheffe test. Each dumbbell was also examined for failure mode and the data was analysed using chi square test. For all statistical analysis, the significance level was set at p<0.05.
Results: Two-way ANOVA analysis indicated that overall there was a statistically significant difference between the 24 hours and thermocycling test (p=0.012), but no differences between sandblasted only (control), sandblasted and Perform-ID or sandblasted and sodium hypochlorite groups (p=0.272). Post-ANOVA contrasts indicated that only the sandblasted and sodium hypochlorite group showed a significant difference between the 24 hours (0 thermal cycles) and thermocycling test (p=0.012). Chi-square analysis showed no significant difference in the mode of failure between the three disinfectant groups at 24 hours (p=0.413) and after 500 thermal cycles (p=0.154).
Conclusions: Disinfectants did not significantly decrease tensile bond strength between Nickel-Chromium dumbbells bonded with resin based adhesive cement. Thermocycling significantly reduced tensile bond strength of dumbbells which were sandblasted and immersed in sodium hypochlorite. Failure mode analysis did not show any significant difference between dumbbells in all three test groups at 24 hours and after 500 thermal cycles.
Keywords: Adhesion, Alloys, Cements and Disinfection/sterilization
See more of: Dental Materials 1: Adhesion - Bond Strength Testing and Mechanisms