A study of a low copper dental amalgam by analytical transmission electron microscopy

Analytical transmission electron microscopy was used to study specimens of a low-Cu dental amalgam (Velvalloy), prepared using the ''wedge technique.'' Analysis confirmed that the microstructure consists of a Ag2Hg3(gamma(1))/HgSn7-9(gamma(2)) matrix surrounding unreacted Ag3Sn(gamma) particles. In addition a hitherto uncharacterized reaction layer of fine grains between Ag3Sn(gamma) and Ag2Hg3(gamma(1)) is a mixture of Ag3Sn(gamma), Ag-Hg-Sn(beta(1)), Ag2Hg3(gamma(1)), and occasionally Cu6Sn5 (eta') An Ag-Hg-Sn(beta(1)) phase was clearly identified for the first time. Since Velvalloy is a simple commercial dental amalgam, it is a reasonable starting point for characterizing more complex dental amalgam microstructures.