Mercury release from dental amalgam fillings

Abstract

Several aspects of Hg release from dental amalgam tooth fillings were examined both in vivo and in vitro. Using light microscopy, Hg globules (diameter =1-2μm) were observed on amalgam surfaces. Hg vapour was measured in exhaled air before and after 5 min of gum chewing in three groups of subjects with varying numbers of dental amalgams. Group 1 had symptoms similar to those of chronic low-dose Hg exposure, N=22; Group 2 had no apparent symptoms and were considered healthy, N=20; Group 3 were controls having no amalgam fillings; N=10. Groups 1 and 2 both demonstrated a significant 3-fold increase in Hg vapour levels after chewing, while levels in controls remained undetectable. A mouth rinse with hot water (55°C) in Group 2 resulted in a further increase in Hg vapour levels. Saliva samples (1 ml) from 17 subjects in Group 2, collected before and after chewing, showed a significant 8-fold increase in Hg concentration after chewing. In a fourth group Hg absorption by the oral mucosa was studied, Group 4, N=10. A 50% degree of absorption was found after 3 min. It is concluded that dental amalgam should be considered an unsuitable alloy resulting in long-term Hg exposure and that it is therefore toxicologically unsuitable as a dental filling material.