PORCELAIN BONDING OF TITANIUM ALLOYS

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Titanium appears to be highly suitable for dental prosthetic applications because of its excellent corrosional resistance, good biocompatibility and light weight. However, there are problems in porcelain bonding of pure titanium. The object of this study was to develop the porcelain bonding titanium alloy system using beta titanium alloys and low expansion ceramics.First, the bonding strength and reactions between pure titanium and porcelain were investigated. Two kinds of commercial porcelains on pure titanium were fired in low pressure air, low vacuum + argon gas or high vacuum + argon gas. In any firing conditions, porcelain bonding strength of pure titanium was much lower than those of Ni-Cr alloys. Be cause the titanium surface oxide layer spalled easily and the expansion of titanium might be lower than that of porcelain.Then, beta-titanium dental casting alloys, Ti-2OCr-0.2Si and Ti-25Pd-5Cr, were selected as porcelain bonding metals because of those lower expansion and thinner oxide layer. The bonding strength between the beta titanium alloys and porcelain by pull-out test were much higher than that of pure titanium. Especially the bonding strength of Ti- 25Pd-5Cr alloy showed the highest value. But if the porcelain was fired on these beta titanium plate, it was fractured and split by small bending stress. Then the porcelain expansion was reduced by mixing castable ceramics. This low expansion porcelain bonded firmly with the beta-titanium alloys.