Steady-state transfer and depletion kinetics of mercury from amalgam fillings

In 29 volunteers with a low amalgam load, the number of amalgam-covered too th surfaces and the occlusal area of the fillings were determined. Before a nd at select times after removal of all amalgams, concentrations of total m ercury were measured by cold-vapor atomic absorption in plasma and erythroc ytes as well as in urine together with the excretion rate. Absorbed daily d oses were estimated from intraoral Hg emission by two separate methods. The transfer of Hg from the fillings via the oral cavity and blood to urinary excretion was evaluated according to the most representative combination of parameters. This consisted of occlusal area (1), absorbed dose (2), Hg con centration in plasma (3) and urinary excretion (4). Pairwise correlation co efficients were 0.49 for parameters 1 vs. 2, and 0.75 each for parameters 2 vs. 3 and 3 vs. 4. Within 9 days after removal of the fillings: a transien t increase in Hg levels was observed in plasma only; in the group without a rubber dam, concentrations increased significantly above pre-removal value s at days 1 and 3, whereas they decreased significantly below pre-removal v alues at day 30 in the rubber-dam group and at day 100 in both groups. Excr etion rates decreased significantly at day 100 in the protected group. Peak plasma-Hg was 0.6 ng/ml on average at day 1 and decreased with half times of 3 and 43 days in subjects protected by a rubber dam. The results indicat ed that concentrations of total mercury in plasma responded rapidly to chan ges in the amalgam status and reflected the actual absorption most reliably . Notably, plasma-Hg levels were sensitive enough to detect a transient att enuation of the additional exposure after using a rubber dam during the rem oval of only a few fillings. However, being small in magnitude and lasting 100 days at best, the rubber-dam effect had minor toxicological relevance. (C) 2000 Elsevier Science B.V. All rights reserved.