Effect of Middle Layer by Electro-spark Deposition Technology on Bonding Strength of Porcelain and Cast Pure Titanium

Objective:To investigate the effect of middle layer by electro-spark deposition(ESD) technology on bonding strength of titanium and porcelain.Methods:Forty pure titanium specimens with the size of 25mm×3mm×0.5mm were randomly divided into four groups(n=10) according to four different surface treatments:untreated control,Si electrode group,Zr electrode group and CoCr electrode group.We sandblasted four groups and measured the roughness.After the middle area of the samples were veneered with Ti-22 system,a three-point-flexure-test was used to evaluate the bonding strength of titanium to porcelain.The interface of titanium and porcelain was investigated by scanning electron microscope(SEM) with energy disperse spectroscopy(EDS).The phase composition of Si electrode group specimens was characterized by X-ray diffraction(XRD).Results:There were no significant difference in the roughness among four groups after sandblasting.The mean bonding strength of Si electrode group was the highest(33.38±3.67MPa),it was significantly higher than those of other three groups(P0.05),and there were no significant difference in the bonding strength among those of other three groups.No definite oxide layer was observed at the interfaces in four groups.A 15-20μm thick transition layer was observed between middle layer and titanium in Si electrode group.TiN,Ti5Si3 and TiSi2 were characterized by X-ray diffraction in Si electrode group specimens.Conclusion:Middle layer prepared by ESD technology using Si electrode significantly improves bonding strength of porcelain and cast pure titanium.