In vitro tarnish of dental amalgams.

1. Tuccillo-Nielsen tarnish test in an effective screening device for dental amalgams. 2. The gamma phase appears to be more tarnish prone in conventional dental amalgams than gamma 1 phase. Although gamma 2 appeared to be tarnish prone, it was difficult to discriminate this phase because of the porosity in the amalgams. 3. The copper-rich phases are the most tarnish prone in high-copper amalgams. Gross examinations of amalgam from additive systems show spotty tarnish, whereas more uniform tarnish appearance is observed in amalgams from single-composition alloys. 4. The amalgams can be graded for in vitro tarnish performance in selected groups like the additive systems and the single-composition alloys.