It has been proved in previous studies that the surface treatment of cobalt-chromium alloy with gold dust was effective not only to increase the bonding strength between metal and porcelain, but also to cover metal color and prevent the border coloring.
In this study, two kinds of gold alloys for porcelain fusing indifferent compositions (Select 50 and Select 77 H, Ohura Precious Metal Co.) were selected to examine the effect of metal surface treatment with gold dust on the bonding strength. The size of gold dust (Super-Binder OG, Ohura Precious Metal Co.) used in this study was 1.0 μm in a uniform diameter.
The results showed that both alloys exhibited stronger bonding strength after treated with gold dust, particularly in the case of Select 50. Most of the gold dust remained on the fractured surface of Select 50 specimens after the shear test, observed by scanning electron microscope. It was also found that gold dust existed on both metal and porcelain surfaces in the case of Select 77 H.
The above results suggested that the treatment of a metal surface with gold dust could reinforce the bonding strength between gold alloy and porcelain. Furthermore, the bonding strength would increase greatly if the gold dust was bonded firmly to the metal surface.