revised final - Agency for Toxic Substances and Disease Registry ...

MERCURY 293
More on Health Effects and Dental Amalgam.
2. HEALTH EFFECTS
A number of government sponsored scientific reviews of the literature on the health effects associated with
the use of dental amalgam have concluded that the data do not demonstrate a health hazard for the large
majority of individuals exposed to mercury vapor at levels commonly encountered from dental amalgam
(DHHS 1993; Health Canada 1997). Governments that have restricted the use of amalgam or recommend
limited use (e.g., Germany, Sweden, Denmark, and Canada) cite the need to minimize human exposure to all
forms of mercury as much as possible and to reduce the release of mercury to the environment (DHHS 1993;
Health Canada 1997). The restrictive actions, however are prospective, and none of the government reports
recommend removing existing fillings in people who have no indication of adverse effects attributable to
mercury exposure. Removal of existing amalgams, if improperly performed or not indicated, may result in
unnecessarily high exposure to mercury. Levels of mercury release for various dental procedures have been
reported by Eley (1997). Chelation therapy (used to remove metals from the body tissues) also may have
adverse health effects (and varying levels of effectiveness), and should be considered only in consultation
with a qualified physician.
In 1990 in the United States, over 200 million restorative procedures were provided of which dental
amalgam accounted for roughly 96 million (DHHS 1993). In the 1970s, the use of amalgam was 38%
higher. The use of mercury amalgam has been steadily declining and is expected to continue to decline due
to improvements in dental hygiene and preventive care. Approximately 70% of the restorations placed
annually are replacements. Advocates of the safety of amalgam emphasize the long history of use (over
150 years) and the large exposed population without apparent adverse effects as strong support for their
position (ADA 1997). They also underscore the poor quality of the studies in the literature reporting adverse
effects attributable to amalgam. Researchers concerned about the safety of mercury amalgams counter that
sample sizes in the studies that support the safety of amalgams are also too small to detect low frequency
effects in the general population, and that the absence of high quality studies simply reflects the relatively
small amount of research effort that has gone into resolving this very important issue (Richardson 1995;
Weiner et al. 1990).
The general public is also clearly concerned about the placement of mercury, a substance with demonstrated
toxic effects, into their mouths. A survey conducted by the American Dental Association in 1991
demonstrated that nearly half of the 1,000 American adults surveyed believed that health problems could
develop as a result of dental amalgam (ADA 1991). Increases in life expectancy and increases in the