Safety of dental amalgam fillings still a matter of dispute

By Nicola Menke Nov 14, 2011, 3:06 GMT

Berlin - Mercury is the most toxic non-radioactive substance known to man - just two grams are lethal. Though essentially a hazardous material, it can be found in many people's mouths because about 50 per cent of dental amalgam fillings consist of elemental mercury.

The heavy metal is extremely toxic only in a dissolved state, however, and not when it is hardened and alloyed with other metals in a tooth filling.

Various studies, including the recent German Amalgam Trial by Munich Technical University's Centre for Naturopathic Research, have shown that people with dental amalgam fillings have, on average, four times more mercury in their blood than people without them.

Opinions on the health consequences of these higher mercury levels are divided, with some experts seeing a clear risk of poisoning and others regarding the risk as slight.

'As with any foreign substance remaining in the human body for a long time, unwanted side effects can, of course, occur,' said Reiner Zaijtschek, a national executive board member of the Free Association of German Dentists. But, the impact of dental amalgam fillings was small, he added.

'No study has proven a definite link between them and chronic health problems,' said Zaijtschek. Handling amalgam responsibly, however, was very important because mercury was particularly dangerous as a vapour - released when dental fillings were placed or drilled out.

There is agreement that the danger of mercury poisoning is greatest when the amalgam is being put into or taken out of the mouth. The potential risks of long-term contact with mercury in tooth fillings are far lower.

'As soon as the filling has hardened, there is no longer any free mercury,' said Dietmar Oesterreich, vice president of the German Dental Association, and that attrition did not release any mercury from the metal alloy.

Critics of amalgam have a different view.

'The fillings constantly release small doses of mercury. Some of it is deposited in the body, for example in connective tissue and organs,' said Claudia Hesse of the Berlin-based Society of Holistic Dentistry.

She said mercury was released not only by attrition, but that acids could free mercury ions from fillings, which then get into the digestive tract via saliva and are spread around the body through the bloodstream.

'Mercury vapour is what's most dangerous. It's released mainly during the consumption of hot foods and drinks,' Hesse explained. She said the vapour is inhaled through the nose and mouth, enters the bloodstream and could penetrate all bodily tissues and even the blood-brain barrier, which protects the brain from toxins.

According to Peter Jennrich, a member of the academic advisory council of the German Medical Society for Clinical Metal Toxicology, mercury often causes neurological symptoms such as restlessness and fatigue as well as headaches and gastrointestinal complaints.

'What is more, poisoning by the heavy metal can be a co-factor in almost all chronic illnesses,' he said.

A standard medical examination frequently cannot determine whether mercury poisoning has occurred, and if so, to what degree. 'Neither a normal blood analysis nor a urine sample shows everything,' Jennrich said.

Because the toxin builds up in tissues and organs, only a special provocation test can detect it. This is done by administering a chelating agent, an organic compound able to bind metal ions, which are subsequently secreted by the body. The degree of poisoning is then measurable in the urine.

The prescribed therapy depends on how much mercury is found to be in the body and could entail removal of the dental amalgam fillings or a heavy metal detoxification. The latter is used in cases of acute mercury poisoning and is most effective when chelating agents are used.