OBJECTIVETo evaluate the effect of nano-silica coating prepared by different concentration silica sol on shear bond strength between alumina ceramic and resin cement.

METHODSSilica coating was prepared with colloidal silica sol on alumina ceramic surface that was treated with air particle abrasion. Infrared spectrum (IR), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) were used to analyze the silica coating. A total of 32 alumina ceramic discs were randomly divided into 4 groups with 8 discs per group, which received different surface treatments as silane couple agent (control group), 20% silica sol + silane (group A), 30% silica sol + silane (group B), 40% silica sol + silane (group C). Each ceramic disc was bonded to composite with resin cement, and then shear bond strength of these samples was tested.

RESULTSIt was observed from the IR pictures that symmetrically flexible vibration absorption kurtosis, anti-symmetrically flexible vibration absorption kurtosis, and bending vibration absorption kurtosis of Si-O-Si enhanced after heat treatment. SEM pictures showed that nanoparticles in coating gel were well distributed and some of them conglomerated after heat treatment. There was a little conglomeration in 20% coating, more in 30%, and the most in 40%. Contents of surface silicon increased after modification with silica coating prepared by sol-gel method. Bond strength of three groups with silica coating was significantly higher than that of the group with only silane couple agent [(1.881 +/- 0.156) MPa] (P < 0.05). Group B gained the highest strength [(4.852 +/- 0.178) MPa] compared with group A [(3.196 +/- 0.171) MPa] and group C [(3.576 +/- 0.671) MPa] (P < 0.05).

CONCLUSIONSSurface silicon contents all increased after surface modification with different concentration silica sol. Silica coating followed with silane couple agent could significantly enforce bond strength of alumina ceramic, with 30% silica sol group gaining the highest bond strength.