Evaluation of two thione primers and composite luting agents used for bonding a silver-palladium-copper-gold alloy.

The purpose of the current study was to evaluate the bond strength and durability of two metal adhesive systems bonded to a silver-palladium-copper-gold (Ag-Pd) alloy. Disk specimens were cast from an Ag-Pd alloy (Castwell M.C. 12), air-abraded with 50 micro m grain-sized alumina, and they were bonded with two primer-cement bonding systems (Alloy Primer and Panavia Fluoro Cement; Metaltite and Bistite II). For each cement, unprimed specimens were also prepared as experimental controls. Shear bond strengths were determined both before and after thermocycling (4-60 degrees C, 1 min each, 100 000 cycles). The average post-thermocycling bond strengths in MPa (n=8) were: 39.0 for the Metaltite-Bistite II system, 32.2 for the Alloy Primer-Panavia Fluoro Cement system, 23.1 for the Bistite II material and 21.0 for the Panavia Fluoro Cement material. The use of proprietary primers, both of which contain thione functional monomer, enhanced the post-thermocycling bond strengths of both cements (P < 0.05). After thermocycling, however, the difference in bond strength between the two cements was not significant regardless of the use of the primers (P > 0.05). It is concluded that the combined use of the thione primer and the luting agent is necessary for bonding the Ag-Pd alloy examined.