Tin passivation by copper in dental amalgams

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