Mercury is a poison that's more toxic than arsenic. So why is it still an ingredient in dental fillings? The campaign against amalgam fillings - made with a mixture of mercury and other metals, and used for more than 150 years - got a boost in October when an international treaty to control the use of the toxic metal, the United Nations Minamata Convention on Mercury, was signed into action.
Although the treaty didn't set a deadline for the banning of dental amalgam, it did lay down steps to phase it out, including promoting mercury-free alternatives, changing dental school curricula and retraining dentists.
If you have three or more amalgam mercury fillings, you will show some symptoms
Amalgam, or silver, fillings have been hotly debated since the 1970s. It was enough to persuade Sweden to ban them in 1997 after determining that 250,000 Swedes had immune disorders and other ailments as a direct result of the mercury in their fillings.
Some countries have followed suit. Elsewhere, including in Hong Kong, dentists continue to use them.
While scientists agree that dental amalgam fillings slowly release mercury vapour into the mouth, the amount of mercury released and the question of whether this exposure presents a significant health risk remain controversial.
"If you have three or more amalgam mercury fillings, it is almost certain you will show some symptoms, like digestive and immune symptoms, colds or allergies, or nervous system decline that is accelerated so that your concentration is affected," says Graeme Stuart-Bradshaw, homeopath and naturopath with the Integrated Medicine Institute. "Quite likely, you will also have damage to the liver."
Mercury has also been shown to build up in the brains and other organs of fetuses if the mother has amalgam fillings, and can be passed to infants through breast milk. "It is important that women remove their amalgams a good six months before they conceive," says Stuart-Bradshaw.