History and current state of metal adhesion systems used in prosthesis fabrication and placement

The adhesion techniques used in prosthetic dentistry have substantially improved with respect to retention of veneering resin to the metal framework of resin-veneered restorations and the bonding of resin-bonded fixed partial dentures (RBFPDs) to abutment teeth. In the early 1970s, prostheses relied on macromechanical retention for veneering surfaces and the retention holes of retainers. Later, retention was achieved by using small spherical particles. In addition, the use of small pits created by electrochemical corrosion was tested in resin-veneered restorations and RBFPDs. Thus, micromechanical retention gradually supplanted macromechanical retention. First-generation adhesive monomers were introduced at the end of the 1970s and were succeeded in the early 1980s by the marketing of adhesive resin cements, which were effective for use with non-noble alloys when surface oxidation procedures were used. In 1994, a second-generation adhesive primer for noble alloys was introduced, which prompted development of other adhesive primers. These primers were applied mainly to silver-palladium-copper-gold and type IV gold alloys and improved the reliability of RBFPDs. Recent studies have confirmed the effectiveness of such primers when used with high-gold-content metal ceramic alloys. Due to these developments, RBFPDs now have excellent esthetic characteristics.