Practice Scenario 1: Mercury in Dental Fillings (Amalgam)
Practice Questions 1 Below
Mercury Fillings: Mercury fillings are the most commonly used by dentists in the U.S.
Amalgam fillings are usually 50% or more mercury.
The amount of mercury in each filling is about the same as in a mercury thermometer or at least ½ gram.
Amalgam fillings are referred to as “silver” and supported as "safe" by the American Dental Association.
Issue of Concern: Mercury is a neuro-toxin capable of harming the developing brain of a fetus or child. Mercury is released from amalgam dental fillings and absorbed into the human body. For more than a decade, concerns have been raised about the mercury in dental fillings. Health concerns raised include: compromise of the immune system, kidney damage, multiple sclerosis, and deficits in children's learning and motor skills.
Actions To Date: Austria, Britain, Canada, Denmark, Germany & Sweden have either banned or discouraged the use of mercury fillings, especially for pregnant women and children. Japan no longer teaches the use of amalgam in dental schools. Some U.S. states have disclosure regulations about amalgam including Maine and California. California requires the notice to be posted: “Dental Amalgam, used in many dental fillings, causes exposure to mercury, a chemical known to the state of California to cause birth defects or other reproductive harm.”
U.S. National Debate: In 1998, the U.S. Public Health Service identified fish and mercury fillings as the 2 largest sources of mercury in most U.S. residents. In 2003, the U.S. EPA said 1 in 12 women of childbearing age have so much mercury in their bodies they are at risk of having a brain injured child. In 2004, EPA doubled the 2003 estimate, recognizing that the fetus absorbs mercury at a higher rate, per body weight, than the mother.
Latest U.S. Findings: A study funded by the National Institutes of Health (NIH)
confirmed that mercury from fillings is absorbed in the body, but in non-harmful trace amounts. It found no proof that mercury in dental fillings causes kidney, brain or immune system damage. The report, issued in 2004, was a review of 300 studies from the past 8 years.
"Influence" Controversy: This latest NIH funded study was conducted by The Life Sciences Research Office on behalf of the National Institute of Dental and Craniofacial Research (the Dental Institute of NIH).
NIH has now launched an investigation of its Dental Institute to determine if the research contract for the study was improperly given to a known supporter of the American Dental Association's stance that mercury fillings are safe.
Alternatives to Mercury Fillings: Plastic resins (which are suspected to also leach from fillings and may cause harm), Composite inlay, glass ionomer cement, ceramic inlay, and gold inlay. Alternatives also include practices and measures designed to prevent development of cavities.
Mercury Products Phased-out or Voluntarily Removed from U.S. market: Mercurochrome and other mercury-based disinfectants; mercury preservatives in childhood vaccines, mercury thermometers, mercury out of contact lens solutions.
The Case for Precaution Practice:
1) In the above scenario, identify gaps in scientific knowledge (i.e., issues of scientific uncertainty).
2) Distinguish whether the knowledge gaps would be classified as risk, uncertainty or ignorance.
3) Outline what other information you would need to know about mercury fillings and potential to harm human health.
4) Do you think that there will ever be conclusive "cause and effect" proof that mercury fillings cause harm?
5) Do you know upon what basis other mercury products, such as the popular first-aid antiseptic, mercurochrome, were discontinued?
