Objectives: In this in vitro study, the effect of various drying (surface reaction) times of a commercial silane, other than that recommended by the manufacturer (at least 5 min), on the bond strength between the resin composite and silica coated base and noble alloys was evaluated.
Methods: A total of 112 disc specimens (9 mm diameter and 0.5 mm thickness) were cast out of two types of alloy designed for ceramic firing, one of which was a noble (Degunorm) (gold-silver-platinum) and the other a base alloy (Wiron 99) (nickel-chromium-molybdenum). The specimens were assigned to two main groups according to each alloy type. These two main groups were further divided into seven subgroups, having eight specimens each. The specimens of both alloy types were air-abraded with 30 microm silica (SiO2) coated alumina (Al2O3) (CoJet-Sand, ESPE, Seefeld, Germany). The conditioned surfaces were coated with 3-methacryloxypropyltrimethoxysilane (MPS) and were allowed to react and dry for 1, 2, 3, 4, 5, 6, and 7 min, respectively, before the opaquer was applied. Immediately after the waiting periods for the silane to dry, first opaquer and then resin composite were applied. After storage in water for 30 days at 37 degrees C and thermocycling (5000 cycles, 5-55 degrees C), shear tests were performed using the universal testing machine at a crosshead speed of 0.5 mm/min.
Results: Analysis of data showed no significant difference in bond strength for any silane drying and reaction period for both base and noble alloys between 1 and 7 min (ANOVA, P = 0.05) (Degunorm: 5.8 - 7.4 MPa and Wiron 99: 7.2 - 10.2 MPa, respectively). Bond strengths of resin composite to base alloys were significantly higher than those to noble alloys at 2, 3 and 5 min (P = 0.0045, P = 0.05, P = 0.002, respectively).
Significance: In order to optimize the flow of laboratory work, the silane solution drying time might be reduced to 1 min for both base and noble alloys.