Effect of multiple firing on the bond strength of selected matched porcelain-fused-to-metal combinations.

In this study two different opaque porcelain-metal combinations were evaluated for planar shear bond strength. Samples were tested after one, three, five, seven, and nine different firing cycles to evaluate the effect of repeated firing on shear bond strength. For the combination of Will Ceram/W1 and Vita/Olympia materials, no statistical difference was observed either between materials or after repeated firing. For apparently well-matched porcelain-metal combinations, no significant reduction in bond strength occurs during normal firing of the opaque porcelain to the metal.