Effects Of Nano-silica Coating On Shear Bond Strength Of High-strength Ceramic

In recent years,because of their physical and aesthetical properties, all-ceramic restorations enjoy a high popularity,especially the high-strength ceramics such as glass infiltrated alumina ceramic and zirconium oxide ceramic.Nevertheless,failure rates ascribing to high-strength ceramic fracture are still high up to 2.3%-8%,most of which initiated from the cementation or internal surfaces.So the long-term strong,stable bond to these ceramics is dispensable for successful restoration.Many literatures on such surface-treatment methods are available as used with high-strength ceramics for the purpose of good bonding.Because glass infiltrated alumina ceramic and zirconium oxide ceramic contain only a small amount of silica within its glass matrix.Silane application did not significantly enhance the resin-to-ceramic bond strength,and etching the ceramics with hydrofluoric acid did not create a microretentive surface compared with conventional ceramics.It has shown that silica coating combined with silane is a effective method of surface conditioning for the ceramics.However,the present silicoater techniques were rather complicated,expensive,vulnerable to difficulties,and all these shortcomings inhibited the promotion of these techniques.Solution-gelatin (sol-gel)synthesis of nano-composites containing ultrafine particles of silicon in oxide matrices has been rapidly developed,as an easier and less complicated method in making coating,it has been investigated in various situations.The purpose of this study was to prepare nanostructured silica coating on the surface of glass-infiltrated alumina ceramic and zirconium oxide ceramic with sol-gel process,and to evaluate the effect of nano-silica coatings prepared by different concentration silica sol on shear bond strength of the ceramics. Furthermore,the durability of the bond strength over 30 days storage time is yet to be investigated.PartⅠEffects of nano-silica coatings on shear bond strength of glass infiltrated alumina ceramicObjectives:The study evaluated the effect of nano-silica coating prepared by different concentration silica sol via a sol-gel process on shear bond strength of resin cement to a glass-infiltrated alumina ceramic.Methods:Nano-silica coating was prepared with colloidal silica sol on glass-infiltrated aluminum oxide ceramic surfaces which had been treated with air particle abrasion.Scanning electrical microscopy(SEM),Fourier Transmission Infrared spectrum(FTIR)and energy depressive spectrum(EDS) were used to analyze the silica coating.Sixty-four blocks(10×10×2mm)of In-Ceram alumina ceramic were fabricated according to the manufacturer's instructions,and the specimens which had been treated with air particle abrasion were assigned to one of the following four groups(n=16),(A) silanization,(B)silica coating prepared by 20%silica sol+ silanization(C) silica coating prepared by 30%silica sol+ silanization(D)silica coating prepared by 40%silica sol+ silanization.Composite cylinders were luted with resin cement to the specimens.The ceramic-composite blocks were then stored in distilled water at 37℃either for 24 hours or for 30 days prior to shear bond tests in a universal testing machine(MTS synergi,MTS,USA).The bond strength of each block was statistically analyzed by ANOVA and LSD test.Results:Silica coatings can be made via sol-gel process successfully.SEM pictures showed that nano-particles in coating gel were well-distributed and some of them conglomerated after heat treatment.There were only a little Conglomeration in 20%coating,more in 30%and the most in 40%.And as showed in EDS,contents of surface silicon increased after modification with silica coatings by sol-gel method.It can be seen from the IR picture that anti-symmetrically flexible vibration absorption kurtosis,symmetrically flexible vibration absorption kurtosis and bending vibration absorption kurtosis of Si-O-Si enhanced after heat treatment.Bond strengths of groups with silica coatings were significantly higher(P＜0.05),while groupC(4.9±0.3MPa) gained the highest strength compared with groupB(3.2±0.21MPa)and groupD (3.6±0.7MPa)(P＜0.05).No statistically significant difference existed between groupB and groupD.After 30 days storage time,he bond strengths of four groups all insignigicantly decreased.The mean bond strength in group C was significantly higher than that of other groups(p＞0.05).Conclusions:Nano-silica coating can be made with sol-gel process successfully,which increased content of silicon element of dental aluminum oxide ceramic.Heat treatment may reinforce Si-O-Si net structure but some parts of nano-particles in coating gel conglomerated.Conditioning the In-Ceram alumina ceramic surfaces with silica coatings provided higher bond strength of the resin cement.And the 30%silica sol gained the highest bond strength after either 24 hours or 30 days storage time.PartⅡEffects of nano-silica coating on shear bond strength of Zirconium Oxide CeramicObjective:Aim of this study was to evaluate the effect of nano-silica coating prepared by different concentration silica sol with a sol-gel process on shear bond strength between zirconium oxide ceramic and resin luting cement.Methods:Four zirconium oxide ceramic groups were fabricated to receive different surface treatments as(A)silanization,(B)silica coating prepared by 20%silica sol+ silanization(C)silica coating prepared by 30%silica sol+ silanization(D)silica coating prepared by 40%silica sol+ silanization. Composite cylinders were luted with resin cement to the specimens.Each group was then divided into two subgroups(each with 8 specimens)and then were stored in 37℃distilled water either for 24 hours or for 30 days.Then the samples were tested in a universal testing machine for shear bond strength test. Scanning electrical microscopy(SEM)and energy depressive spectrum(EDS) were used to analyze the silica coatings.Results:Contents of surface silicon increased after modification with silica coating prepared by sol-gel method.Bond strengths of groups with silica coatings were significantly higher(P＜0.05),and groupC gained the highest strength compared with groupB and groupD(P＜0.05),no statistical significant difference existed between groupB and groupC(P=0.064).After 30 days water storage time,bond values in four groups all decreased insignificantly to 2.33±0.10MPa,2.98±0.05 MPa,4.98±0.25 MPa,3.16±0.05 MPa respectively, the mean bond strength in group C was significantly higher than that of other groups(p＞0.05),statistical significant difference existed between groupB and groupC(P=0.018).Conclusion:Sol-gel process is an effective way to prepare silica coating on zirconium oxide ceramic.Conditioning the ceramic surfaces with silica coatings provided higher bond strength of the resin cement.And the 30%silica sol gained the highest bond strength.