Editors Note: This letter was originally sent to Congressman Dan Burton and published on the ADA website, but has since been removed from public viewing by the ADA. We publish the letter here in its entirety under the "fair use" principle of US copyright law.

May 11, 2001

The Honorable Dan Burton
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

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

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

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:

* Dahl JE, Sundby J, Hensten-Pettersen A, Jacobsen N. " Dental Workplace
exposure and effect on fertility " Scand J Work Environ Health 1999
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.

* Schuurs AH. " Reproductive toxicity of occupational mercury. A review
of the literature" J. Dent 1999;27(4):249-56. 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

* Saxe SR, Wekstein MW et al. "Alzheimer's disease, dental amalgam and
mercury", JADA 1999 Feb;130(2):191-9
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.

* Ahlqwist M, Bengtsson C et al, "Serum mercury concentration in
relation to survival, symptoms, and diseases: results from the prospective
population study of women in Gotherburg, Sweden. Acta Odontol Scand 1999 June;
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



Robert M. Anderton, D.D.S., J.D., LL.M.


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Document Posted: May 11, 2001
Page Updated: May 11, 2001