Effects of Sandblasting and Hydrofluoric Acid Etching on Surface Topography, Flexural Strength, Modulus and Bond Strength of Composite Cement to Ceramics.

Purpose: To evaluate the influence of different surface treatments of two CAD/CAM glass ceramics on surface topography, shear bond strength of composite cement, flexural strength, and elastic modulus.

Materials and methods: Two ceramics were evaluated: lithium-disilicate (LDS) and zirconia-reinforced lithium silicate (ZLS) glass ceramics. Glass ceramics were sintered and the surfaces were sandblasted (SBL) or etched with 9% hydrofluoric acid for 10 s (HF10), 20 s (HF20) or 30 s (HF30). The treated surfaces were analyzed using scanning electron microscopy (n = 3) to evaluate the etching pattern. For bond strength testing, ceramic samples were silanized after treatments and an adhesive was applied to the surface. Afterwards, a silicone mold was used to build composite-cement cylinders, which were tested after 24 h or one year of water storage (n = 10). Flexural strength and modulus were assessed using a 3-point bending test (n = 15). The data were subjected to statistical analysis at a pre-set α = 0.05.

Results: SBL and HF resulted in different surface topographies. Increased HF etching time influenced the surface dissolution level and exposition of crystals for LDS, while no effect of etching time was observed for ZLS. After one year, the bond strength to LDS significantly decreased, regardless of treatments. For ZLS, HF10 and HF20 showed stable bond strengths over time. SBL yielded the lowest bond strength for both ceramics and statistically significantly reduced the flexural strength of ZLS. The flexural strength and elastic modulus of ceramics were not affected by different etching times.

Conclusion: Bonding stability depended on the glass ceramic and the pretreatment method employed. HF etching did not change the mechanical properties of the ceramics and is indicated as a ceramic treatment for bonding.