Mercury from dental amalgam fillings: Studies on oral chelating agents

Hibberd A, Howard M, Hunnisett A. J.Nutr & Env. Med., September 1998 Since the early nineteenth century, dentistry has relied mainly on amalgam (approximately 50% metallic mercury (Hg)) for filling teeth. Scientific research has shown that hg is constantly released from amalgams, mainly as Hg vapour, which is inhaled, absorbed, metabolized to ionic Hg (Hg2 + ) and distributed throughout the body, mainly bound to proteins. Dental amalgam is the major source of the body Hg burden. Toxicological research on amalgam Hg has indicated deleterious effects on the immune, renal, reproductive and central nervous systems, and oral and intestinal bacteria. Results do not indicate that amalgam fillings are safe. Oral DL-2,3-dimercapto-succinic acid, magnesium salt (DMSA); 2,3-dimercapto-1-propane-sulphonic acid, sodium salt (DMPS); N-acetyl-L-cysteine (NAC) and potassium citrate B.P. (K Cit) were studied for Hg chelating ability in patients who had, or until recently had, amalgam fillings. Based on the increase in urinary Hg concentrations after single doses, compared with controls, the order of efficacy was: DMPS plus K Cit., NAC plus K Cit. and DMSA (each producing an increase of 163%), then in descending order, DMSA plus K Cit., DMPS, NAC and K Cit. Very significant (p<0.01) correlations were demonstrated between post-chelation urinary and post-chelation sweat Hg concentrations with all agents. Both these parameters may be good indicators of total body Hg burden. The advantages of employing combined chelating agents were examined and some clinically useful and convenient methods of assessing and reducing Hg burdens suggested.