Mercury release from dental amalgam fillings.

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.