Controversy Over Amalgam Filling

In dentistry, amalgam is an alloy (combination of metals) of mercury with various metals used for dental fillings. It commonly consists of mercury, silver, tin, copper and other trace metals.

In the 1800s, amalgam became the dental restorative material of choice due to its low cost, ease of application, strength and longitivity.

The dental amalgam controversy refers to the conflicting views over the use of amalgam as a filling material because it contains the element mercury. Scientists agree that dental amalgam fillings leach mercury into the mouth, but studies vary widely in the amount and whether such amount presents significant health risks. The effects of that amount of exposure are also disputed,. The use of mercury in dental fillings is approved in most countries. Norway, Denmark, and Sweden have banned the use of mercury in dental amalgams over environmental concerns, and in Sweden's case also from concerns over its effect on human health.

Health effects
A 2003 monograph on mercury toxicity from the World Health Organization concluded that:

• Studies on humans and animals have demonstrated that dental amalgam contributes significantly to mercury body burden in humans with amalgam fillings.
• Dental amalgam is the most common form of exposure to elemental mercury in the general population,
  
  constituting a potentially significant source of exposure to elemental mercury, with estimates of daily intake from amalgam restorations ranging from 1 to 12.5 µg/day, the majority of dental amalgam holders being exposed to less than 5 µg mercury/day.
• Intestinal absorption varies greatly among the various forms of mercury, with elemental mercury (as found in amalgam) being the least absorbed form (<0.01%)
• Absorption also varies according to individual factors such as gum chewing and bruxism (tooth grinding).
• The number of restorations - amalgam or otherwise - is declining, largely due to improved dental hygiene, in all industrialised countries examined declining by 38% since the 1970s in the USA and over 65% in the ten years from 1986 in the UK
• Although several studies have demonstrated that some mercury from amalgam fillings is absorbed, no relationship was observed between the mercury release from amalgam fillings and the mercury concentration in basal brain.
• However, in the same report it was concluded that "...even at very low mercury levels, subtle changes in visual system function can be measured."
• In multiple sclerosis patients with amalgam fillings, red blood cells, haemoglobin, hematocrit, thyroxine (T4), T-lymphocytes and T-8 (CD8) suppressors cells levels are significantly lower, while blood urea nitrogen and hair mercury levels are significantly higher.
• The report also notes that regarding elemental mercury exposure, the main form of exposure from dental amalgam," most studies rely on assessment of exposure at the time of study, which may not be fully informative, as mercury has a long half-life in the body and thus accumulates in continuous exposure ", making the evaluation of effects on health uncertain.

Health effects for dentists :

In 1991, Geir Bjørklund published a toxicological risk analysis of occupational diseases in dentistry that are related to chronic exposure to inorganic mercury, especially metallic mercury vapour. He found studies indicated that dental work involving mercury may be an occupational hazard with respect to reproductive processes, glioblastoma (brain cancer), renal function changes, allergies and immunotoxicological effects.

Are there alternatives to amalgam?

There is now a dental amalgam that contains indium as well as mercury. The indium helps retain the mercury

so that less is released into the environment. There are also high-copper amalgams. They contain less mercury and more copper. Dentists use other materials for filling teeth. These include Glass Ionomer Cement, Miracle mix, composite resin, porcelain and gold. Amalgam is stronger than composite resin. This is a tooth-colored material.