The relationship between oxide adherence and porcelain-metal bonding.

The lack of a reliable bond test has hindered the elucidation of the mechanism for porcelain-metal bonding in dental systems, because a test capable of detecting differences among porcelain-metal bonds of various qualities is required before the reasons for these differences may be ascertained. A method was developed in the present study whereby specimens of alloys with differing physical properties may be deformed to a constant strain to yield a fracture surface suitable for measurement of the area fraction of retained porcelain by an x-ray spectrometric technique described previously. The method proved sufficiently discriminating that significant differences could be found in 48 of the possible 66 comparisons among alloys and treatments. Linear regression analysis revealed a strong correlation (r2 = 0.947) between the area fractions of retained porcelain measured in the present study and the oxide adherence strength values measured previously. This strong correlation, when considered in light of the literature evidence for the presence of an oxide layer at the porcelain-metal interface, provides compelling support for the oxide layer theory of porcelain-metal bonding in dental alloy systems.