Effects of Hydrofluoric Acid Concentrations, Commercial Brands, and Adhesive Application on the Bond Strength of a Resin Luting Agent to Lithium Disilicate Glass Ceramic.

Abstract

To evaluate the surface topography/roughness and bond strength of a resin luting agent to a lithium disilicate glass ceramic after etching with different concentrations of hydrofluoric acid (HF) and commercial brands. For bond strength evaluation, 260 lithium disilicate glass ceramic (EMX) discs were randomly distributed into 13 groups based on concentrations of HF and commercial brands (n=20): 5% and 10%, Lysanda (LY5 and LY10); 5% and 10%, Maquira (MA5 and MA10); 5% and 10%, FGM (FG5 and FG10); 4.8%, Ivoclar Vivadent (IV5); 5% and 10%, PHS do Brasil (PH5 and PH10); 5% and 10%, BM4 (BM5 and BM10); 9%, Ultradent Inc (UL10); and Dentsply (DE10). A further random distribution (n=10) was made based on the application (+) or absence (-) of an adhesive layer. Resin luting agent cylinders (1 mm in diameter) were added on EMX surfaces, light-cured, and stored for 24 hours in deionized water at 37°C. On a universal testing machine (DL 500, EMIC), specimens were submitted to a microshear bond strength test at a crosshead speed of 1 mm/min until failure. A representative etched EMX disc from each group underwent surface topography analysis using field-emission scanning electron microscopy (n=1), and five (n=5) etched EMX discs from each group were tested for surface roughness. Data were statistically analyzed using analysis of variance and Tukey test (α=0.05). A less conditioned and smoother surface was observed for 5% HF compared to 10%. Additionally, commercial brands of HF were shown to affect bond strength. When the adhesive layer was not used (-), a 10% concentration promoted higher bond strengths to EMX. However, when adhesive was applied (+), the concentrations of HF and commercial brands had no effect on bond strength results. A 10% concentration of HF results in higher bond strength than a 5% concentration. If an adhesive layer is applied, neither this distinction nor the influence of commercial brands is observed.