[The modification of the metal ceramic bond by blended gold coating]

The esthetic appearance of porcelain-fused-to-metal restorations is often compromised in areas in which the ceramic veneer has to be kept very thin. In order to overcome this esthetic problem, bonding gold products are offered by dental manufactures which act as an alloy seal, thereby improving the natural color appearance of the ceramic veneer. In addition, the bond strength between ceramic materials and alloys is said to be maintained or in some cases even increased. The present study investigated the effect of various types of bonding gold layers on strength of the bond between ceramic materials and numerous dental alloys as a function of the type of alloy used, using thermocycling over a period of two months with a total of 85,000 temperature changes. The analysis of the results obtained shows that, contrary to manufacturers' claims, only two of the eight bonding gold products can be recommended, and only for three of the twelve alloys tested, as far as the alleged added adhesion is concerned. Only very few combinations of alloys and bonding gold products did not adversely affect adhesion at all or only insignificantly.