Should amalgam fillings be removed?

Abstract

Marilyn Larkin's news item (Aug 3, p 393)1Larkin M Don't remove amalgam fillings, urges American Dental Association.Lancet. 2002; 360: 393Summary Full Text Full Text PDF PubMed Scopus (5) Google Scholar on the American Dental Association's campaign to discourage people from having amalgam fillings removed deserves some comment. In her report, she cites Frederick Eichmiller's concerns about the number of patients with multiple sclerosis, Alzheimer's disease, and autism requesting removal of these fillings. Dental amalgam is a mercury-based filling that contains elemental mercury at about 50% by weight. Amalgam is classified as an intermetallic compound, because it is mixed with silver, tin, copper, and zinc. To the chemist, this intermetallic compound is unstable by definition—and not a “stable alloy”, as reported by Eichmiller—and mercury vapour leaks from dental amalgam over time. Mercury adsorbed daily from dental amalgam ranges from 2 to 17 μg (not “minute” amounts as Eichmiller claims), and people that use chewing gum or are affected by bruxism may have higher intake of mercury from dental amalgams. Moreover, individuals with dental amalgams are exposed to continuous long-term amounts of mercury (in vapour form and in organic form from biotransformation by oral bacteria). Mercury vapour and organic mercury are the two most important forms of mercury in terms of toxic effects, their major target organ being the central nervous system. Furthermore, T Clarkson2Clarkson TW The three modern faces of mercury.Environ Health Perspect. 2002; 110 (1): 11-23Crossref PubMed Scopus (811) Google Scholar describes individuals with immunological susceptibility to mercury compounds who present with clinical adverse effects.2Clarkson TW The three modern faces of mercury.Environ Health Perspect. 2002; 110 (1): 11-23Crossref PubMed Scopus (811) Google Scholar F L Lorscheider and co-workers3Lorscheider FL Vimy MJ Summers AO Mercury exposure from “silver” tooth fillings: emerging evidence questions a traditional dental paradigm.FASEB J. 1995; 9: 504-505PubMed Google Scholar found a correlation between the total number of amalgam surfaces and total mercury content in whole blood, plasma, urine, faeces, breastmilk, and placenta. Postmortem examinations by M Nylander and colleagues4Nylander M Friberg L Lind B Mercury concentrations in the human brain and kidneys in relation to exposure from dental amalgam fillings.Swed Dent J. 1987; 11: 179-187PubMed Google Scholar show significant correlations between mercury tissue concentrations and the number of amalgam fillings. Similarly, our necropsy findings show a correlation between number of amalgam fillings and mercury content of tissue in brain, pituitary, thyroid, and kidney (unpublished data). Leistevuo and colleagues5Leistevuo J Leistevuo T Helenius H et al.Dental amalgam fillings and the amount of organic mercury in human saliva.Caries Res. 2001; 35: 163-165Crossref PubMed Scopus (56) Google Scholar also report higher concentrations of organic mercury in saliva samples from patients with dental amalgams compared with controls. We believe that Eichmiller's comments are not supported by the findings of experimental studies. The health effects of amalgam fillings warrants further investigation and should be commented on with caution, from whichever view you approach the issue.