Effect Of Gold Sputter Coating Time On The Bond Strength Of Titanium Alloy And Porcelain

[Objective]The aim of this study was to investigate the effect of gold sputter coating on the adhesion between titanium alloy and porcelain with different time.Different thickness of the gold coating would be created by changing the gold sputter coating time,thus,the optimal option of the coating time would be found.[Methods)Eight-eight titanium specimens(d=10mm;h=0.5imm)were prepared.The surfaces of these specimens were polished under running water using waterproof abrasive papers.All of the specimens would be sandblasted and ultrasonically cleaned in acetone,anhydrous ethanol and deionized water,respectively.According to the.different treatments of the titanium alloy,the specimens were divided into 8 groups(n=9).The control group,denoted as SB,would only be treated with sandblasting;the groups treated with different gold sputter coating time(s)were denoted as Au500,Au600,Au700,Au800,Au900,Au1000 and Au1100.According to the manufacture’s recommendation,porcelain sintering procedures would be applied on the specimens,one specimen of each group would be underwent simulated porcelain sintering thermocycles(SPSTs).The last 16 specimens were subjected to cool-thermal cycle for 20 000 times.Shear bond strength test was performed to measure the bond strength of titanium alloy and the porcelain and the results were statistically analysed.Stereoniicroscope was used to characterize the titanium-porcelain interfaces and determine the mode of failure.Field Emission Scanning Electron Microscope(FE-SEM)was used to observe the microstructure of the specimens and Energy Distribution Spectrum(EDS)was also used to analysis the weight percentage(wt%)of the O element on the titanium alloy surfaces before and after SPSTs.After the cool-thermal cycle,the bond strength of the specimens were also measured by shear bond strength test,and the results were statistically analysed.[Results]The shear bond strength of each group was Au500(16.33±1.74 MPa),Au600(16.05±1.61 MPa),Au700(16.61±0.88 MPa),Au800(19.37±0.74MPa),Au900(17.67±1.43 MPa),Au1000(16.64±1.78 MPa),Au1100(16.50± 1.90 MPa),SB(15.04±0.87 MPa).One-way ANOVA analysis results showed that Au800 and Au900 was higher than the other groups which treated with gold sputter coating(P<0.05).Au800 and Au900 was also higher than SB(P<0.05).No significant difference was found between Au500,Au600,Au700,Au1000,Au1100 and SB.Independent sample t test revealed that there was significant difference between Au800 and Au900(P<0.01).After the cool-thermal cycle,the bond strength of SB and Au800 was 8.6±0.65 and 17.01 ± 1.64 MPa,significant difference was found in both groups before and after the cool-thermal cycle.Stereomicroscope showed that the fracture mode of all groups was mixed failure.FE-SEM demonstrated that a lot of pits and sharp edge was found in SB group,but the situation was much better in Au800.Moreover,the gold coating seemed combined closely to the titanium alloy after SPSTs.EDS showed that the gold coating had little effect on the oxidation resistance of titanium alloy during porcelain sintering.[Conclusions]1.Gold sputtering coating could effectively improve the bond strength between titanium and porcelain and the optimal coating time was 800s.2.No relevance was found between the fracture mode and the bond strength.3.The cool-thermal cycle results revealed that gold sputtering coating could improve the durability of titanium and porcelain.