May 11, 2001

The Honorable Dan Burton
Chairman
Committee on Government Reform
U.S. House of Representatives
Washington, D.C. 20515

RE: Autism - Why the Increased Rates? A One Year Update

Dear Mr. Chairman:

The American Dental Association (ADA) requests that the Committee on Government Reform accept this letter as a statement for the record for the committee's hearing on April 25, entitled "Autism -- Why the Increased Rates? A One Year Update."

During the hearing, Dr. Boyd E. Haley stated in his testimony that elementary mercury from dental amalgams could work synergistically with other ethyl-mercury sources and have a cumulative toxic affect on the body. Dr. Haley postulated that this could be a potential cause of autism and Alzheimer's disease.

There is no scientifically valid evidence linking either autism or Alzheimer's disease with dental amalgam. And there is no scientifically valid evidence demonstrating in vivo transformation of inorganic or mercury vapor into organo mercury species in individuals occupationally exposed to amalgam mercury vapor. (Chang, S.B. et al., Factors Affecting Blood Mercury Concentrations in Practicing Dentists; Journal of Dental Research 1992, 71(1) 66-74).

Based on currently available scientific evidence, the ADA believes that dental amalgam is a safe, affordable and durable material for all but a handful of individuals who are allergic to one of its components. It contains a mixture of metals such as silver, copper and tin, in addition to mercury, which chemically binds these components into a hard, stable and safe substance. Dental amalgam has been used for more than 150 years and, during that time, has established an extensively reviewed record of safety and effectiveness.

Issued in late 1997, the FDI World Dental Federation and the World Health Organization consensus statement on dental amalgam stated, "No controlled studies have been published demonstrating systemic adverse effects from amalgam restorations." The document also states that, aside from rare instances of local side effects of allergic reactions, "the small amount of mercury released from amalgam restorations, especially during placement and removal, has not been shown to cause any … adverse health effects."

The ADA's Council on Scientific Affairs' 1998 report on its review of the recent scientific literature on amalgam states: "The Council concludes that, based on available scientific information, amalgam continues to be a safe and effective restorative material." The Council's report also states, "There currently appears to be no justification for discontinuing the use of dental amalgam."

In an article published in the February 1999 issue of the Journal of the American Dental Association, researchers report finding "no significant association of Alzheimer's disease with the number, surface area or history of having dental amalgam restorations" and "no statistically significant differences in brain mercury levels between subjects with Alzheimer's disease and control subjects."

The U.S. Public Health Service issued a report in 1993 stating there is no health reason not to use amalgam, except in the extremely rare case of the patient who is allergic to a component of amalgam. This supports the findings of the Food and Drug Administration, the National Institutes of Health Technology Assessment Conference and the National Institute of Dental and Craniofacial Research, that dental amalgam is a safe and effective restorative material.

There have been several peer reviewed scientific studies concerning the safety of dental amalgam. These studies disprove any link between dental amalgam and various medical conditions. We have listed some of them below:

The study groups consisted of 558 female dental surgeons (1/3 of whom placed more than 50 fillings a week) and 450 high school teachers (control) that had given birth in Norway to at least 1 living child. The study comprised data from a total of 1408 pregnancies. The effects of practicing dentistry and of the given workplace exposure on fertility were analyzed with the discrete proportional hazard regression method.

Conclusions: Occupational exposures had no clear adverse effects on fertility among the female dental surgeons studied.

This paper provides insight into the potential reproductive effects on handling dental silver amalgam. Both animals and case reports and epidemiological studies were reviewed. Conclusions: The studies conclude that negative reproductive effects from exposure to mercury in the dental office are unproven. Consequently, given the low amounts of mercury stemming from dental amalgam fillings, the population at large are at even less risk than dental staff.

This study consisted of 68 human subjects with diagnosed Alzheimer's disease and 33 control subjects without Alzheimer's to determine mercury levels in multiple brain regions at autopsy and to ascertain the subjects' dental amalgam status and history. Conclusions: Mercury in dental amalgam restorations does not appear to be a neurotoxic factor in the pathogenesis of this disease. The authors found that brain mercury levels are not associated with dental amalgam, either from existing amalgam restorations or according to subjects' dental amalgam restoration history. Furthermore, dental amalgam restorations, regardless of number, occlusal surface area or time, do not relate to brain mercury level.

This prospective population study of women in Gothenburg, Sweden was started in 1968-69 and comprised of 1462 women aged 38-60 years at baseline. Follow-up studies were conducted in 1974-75, 1980-81 and 1992-93. Conclusions: No statistically significant correlation was observed between dental amalgam and the incidence of diabetes, myocardial infarction, stroke, or cancer. No association was established between disease and mercury on a population basis in middle-aged and older women.

The National Institute of Dental and Craniofacial Research is currently supporting two very large clinical trials on the health effects of dental amalgam. Studies underway for several years each in Portugal and the Northeastern United States involve not only direct neurophysiological measures but also behavioral and cognitive functional assessments. In addition, the trials are monitoring the impact of amalgam on immune function, antibiotic resistance and renal function. Preliminary findings from these studies are consistent with any number of small and large epidemiological studies published over the years concerning the health effects of dental amalgam.

The ADA supports ongoing research in the development of new materials that it hopes will someday prove to be as safe and effective as dental amalgam. However, the ADA continues to believe that amalgam is a valuable, viable and safe choice for dental patients and concurs with the findings of the U.S. Public Health Service that amalgam has "continuing value in maintaining oral health."

Sincerely,

Signed

Robert M. Anderton, D.D.S., J.D., LL.M.
President
RMA:MT:chf

Document Posted: May 11, 2001
Page Updated: November 09, 2004

For Dr. Haley's response to this letter, see Dr. Haley Reponds