Study finds no link between dental amalgam fillings containing mercury and disease

A new study into whether dental amalgam fillings containing mercury are hazardous to health has found little evidence of an association between amalgam and disease.

The research, carried out on people in the New Zealand Defence Force (NZDF) between 1977 and 1997, is published today in the International Journal of Epidemiology (IJE), edited in the Department of Social Medicine at Bristol University.

The use of mercury in dentistry has been controversial since at least the middle of the nineteenth century as inorganic mercury can cause a wide variety of health problems, particularly in the nervous system and the kidneys. Modern dental amalgam currently contains about 50% mercury and, although alternative dental materials are increasingly available, amalgam’s advantages, including low cost and durability, have maintained its popularity as a filling material.

The controversy has intensified over the last 20 years or so because highly sensitive analytical techniques have shown mercury to be continuously released from dental amalgam fillings and absorbed into the body.

Michael Bates of the School of Public Health, University of California, Berkeley and colleagues in New Zealand and Australia, used data on 20,000 people (84% males) from the NZDF’s own dental service which provides all military personnel with regular and consistent treatment and maintains comprehensive records.

They found no association between dental amalgam and chronic fatigue syndrome or kidney disease. A very small association was found between amalgam and multiple sclerosis. As the cohort was relatively young, there were insufficient cases of Alzheimer’s or Parkinson’s to investigate the possibility of a link between amalgam and these diseases.

Dr Bates said: “The debate about possible health effects induced by dental amalgam is marked by an absence of adequate epidemiological studies. Previous studies have mostly been small with limited exposure data. By contrast, our study had a large sample size, detailed exposure data and a consistent level of dental treatment across the cohort.

“This study is the most comprehensive so far to investigate the amalgam safety issue and generally provides reassurance. Some important questions remain, however, and it is essential that the cohort be followed up in the future to establish whether there were any associations with rarer diseases and diseases more common in the elderly.”

Paper: M N Bates, J Fawcett, N Garrett, T Cutress and T Kjellstrom: ‘Health effects of dental amalgam exposure: a retrospective cohort study’ IJE 2004, Vol 33 No 4 pp 894-901