Tin passivation by copper in dental amalgams

Odontologists have been using dental amalgams for more than a century. In the conventional amalgams, the important formation of a phase Sn7-8Hg called gamma(2) was considered to be responsible for the inferior resistance to corrosion of this first generation of materials. The progressive increase of the copper content in formulae corresponds to the recent improvement of the resistance to corrosion of the dental amalgams. The decrease of the content in gamma(2)-phase in the structure was only suggested to explain this phenomenon. We proposed a second reason, a chemical one. It was found by corrosion tests in a medium with a mineral composition similar to natural. saliva (SAGF medium: Gal-Fovet artificial saliva). (C) 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.