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
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
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
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
- Dahl JE, Sundby J, Hensten-Pettersen A,
Jacobsen N. " Dental Workplace exposure and effect on fertility " Scand
J Work Environ Health 1999 Jun;25(3):285-90.
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
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.
- 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; 57(3):168-74
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."
Robert M. Anderton, D.D.S., J.D., LL.M.
Document Posted: May 11, 2001
Page Updated: August 19, 2002
For Dr. Haley's response to this letter, see Dr.