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

Abstract

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(γ1)/HgSn7−9(γ2) matrix surrounding unreacted Ag3Sn(γ) particles. In addition a hitherto uncharacterized reaction layer of fine grains between Ag3Sn(γ) and Ag2Hg3(γ1) is a mixture of Ag3Sn(γ), Ag–Hg–Sn (β1), Ag2Hg3 (γ1), and occasionally Cu6Sn5 (η′). An Ag–Hg–Sn (β1) 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.