The effect of cooling rate on the apparent bond strength of porcelain-metal couples.

The effects of cooling conditions on the apparent bond strength of a dental porcelain fused to a case substructure were studied. Under the conditions of this investigation slow cooling of the porcelain-metal composite in an oven or rapid cooling in an ice chest from the maturation temperature of the porcelain resulted in the highest values of apparent bond strength. However, additional factors must be considered in the selection of a particular cooling method. From the present data it appears that the most practical procedure for cooling a ceramometal restoration is under a protective cover since it provides the least risk to the integrity of the porcelain-alloy bond and the surface of the porcelain.