Effect of air-drying temperature on the effectiveness of silane primers and coupling blends in the repair of a microhybrid resin composite

Abstract

Purpose: To evaluate the effect of different silane agents and air-drying temperatures on the repair strength of a microfilled hybrid composite. Materials and Methods: Composite cylinders (8 x 4 mm) of Gradia Direct Anterior (GC, N = 36), stored in a saline solution at 37 degrees C for 1 month, were sandblasted (50-mu m aluminium oxide), cleaned (35% phosphoric acid) and randomly divided into six groups (n = 6). Two prehydrolyzed silane primers (Monobond-S, lvoclar-Vivadent, Porcelain Primer, Bisco), a non prehydrolyzed silane primer (Porcelain Liner M, Sun Medical) and three silane/adhesive coupling agents (Porcelain Bond Activator-PBA/Clearfil New Bond, PBA/Clearfil SE Bond, PBA/Clearfil Tri-S Bond, Kuraray) were investigated. Siiane-coated surfaces were air dried at two different temperatures (23 degrees C and 38 degrees C) and repairs (8 x 8 mm) were fabricated (Gradia Direct Anterior). Unrepaired composite cylinders (8 x 8 mm, n = 6) were used as control to evaluate the cohesive strength of the material. Microtensile bond strength measurements (mu TBS) were performed. Results: The silane agent applied (p lt 0.001), the airdrying temperature (p lt 0.001) and their interaction (p lt 0.001) were significant factors (two-way ANOVA, Tukey test; p lt 0.05). Silane primers achieved inferior mu TBS when air dried at 23 degrees C as compared to silane/adhesive blends. Warm air-drying was significantly beneficial to composite repairs mediated by silane primers. Comparable results were achieved by silane/adhesive couplings at 23 degrees C and 38 degrees C. At 38 degrees C all the intermediate agents resulted in repair mu TBS that were comparable to the 24-h cohesive strength of the composite (one-way ANOVA, Dunnett t-tests; p lt 0.05). Conclusion: The chemical interactions between silane primers and compozite substrate may be optimized through warm airdrying. Silane/adhesive couplings were not influenced by the air drying temperature.