Mercury and dentistry
Dental amalgam is a silver-coloured mercury-containing product that many people are familiar with. Also known as 'silver fillings', amalgams are commonly used by dentists to fill cavities in teeth. Amalgam is a combination of approximately equal amounts of elemental mercury and alloy powder, which contains other metals such as silver, tin, copper, and zinc. Mercury is used to bind the other compounds of dental amalgam together to form a hard, stable restorative material. Dental amalgam has been in widespread use for over 150 years, and is one of the oldest materials used in oral health care.
Mercury amalgams are used in dentistry because they are inexpensive compared to other alternatives such as gold, porcelain and composite (white) restorations. Amalgams are also very durable. In addition, dentists continue to use mercury-containing dental amalgam because they are relatively fast and easy to place, and can often be repaired.
For more general information about dental amalgam, please visit the Mercury-containing products page.
For those interested in the health and safety of dental amalgam, please consult the following web sites:
Dental amalgam contains mercury, a toxic and persistent metal with adverse effects on the environment and human health, including neurodevelopmental delays in children. Mercury converts in lakes and waterways to the highly toxic form of methyl mercury, which accumulates in fish, and in turn in wildlife and humans.
The Canadian Dental Association recognizes that while dental amalgam is a safe material for filling cavities, dental amalgam waste should be captured and recovered in order to prevent the release of mercury to the environment.
Environment Canada and the Canadian Dental Association are working together under the Canada-wide Standard on Mercury for Dental Amalgam Waste to reduce releases of mercury from dentistry in Canada by 95% by 2005, from a baseline of 2000.
An article published in the Journal of the Canadian Dental Association entitled: Canada-wide Standards: A Pollution Prevention Program for Dental Amalgam Waste, describes the relationship between mercury, particularly dental amalgam waste, and the environment. It also describes the important role of pollution prevention to ensure that the dental community becomes part of the solution to this serious environmental health problem.
Mercury from dental amalgam waste has the potential to enter the environment through several different pathways. Mercury from amalgam waste can end up in surface waters, the atmosphere, or even agricultural soils through disposal to sewers, landfills, and waste incinerators. Because mercury is an element and does not break down it can ultimately cycle through many different parts of the environment and be carried on wind currents around the world.
Amalgam is relatively stable; however, when amalgam waste is disposed of the rate of release of mercury from the amalgam waste can vary with the size of amalgam particles and with environmental conditions such as the chemistry and temperature of media like sewage, soil, sludge and water bodies where sewage is discharged. While the amount of mercury released from a given dental practice may appear insignificant, the amount generated from the over 17,000 dentists in Canada is considerable.
A study conducted in 2002 found that about 60% of amalgam waste is not captured by conventional vacuum systems (Watson ET. Al. 2002). This amalgam waste can travel through municipal sewer systems to wastewater treatment plants, and may be discharged directly to waterways or end up in sewage sludge. When sludge is applied to land, the mercury it contained may be released to soil, or may volatilize from the soil and be emitted to the atmosphere. When sewage sludge is incinerated, the mercury it contained may be released to the atmosphere.
Mercury can also enter the environment when amalgam waste is either accidentally or intentionally disposed of with municipal solid waste or biomedical waste. The incineration of municipal solid waste or biomedical waste provides a direct pathway for mercury to the atmosphere. In landfills, mercury that volatilizes becomes part of landfill gas and is emitted to the atmosphere.
Once emitted to the atmosphere, mercury can be deposited on land and water bodies and eventually be taken up by fish, wildlife and humans. Because of mercury's ability to travel long distances on wind currents, mercury from point source releases may remain localized in the environment, or may be transported, over time, regionally and even globally, and be deposited far from the source.
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