People with eight fillings or more are ‘at risk of serious illness'

Researchers have warned about health risks associated with fillings (Rex)

People with more than eight fillings have an increased chance of brain, heart and kidney disease, a study claims.

Metals within the tooth fillings could raise blood mercury levels two and a half times, researchers at the University of Georgia have found.

The fillings are generally made of a mixture of metals, including mercury, silver and tin.

On average, Britons have seven fillings each.

It is the first time scientists have found a link between tooth fillings and mercury exposure - which can lead to severe illnesses.

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In Britain more than one million children under the age of five already has at least two fillings.

Researcher Dr Lei Yin, of Georgia University, said: ‘Tooth decay is one of the most prevalent chronic diseases.

‘I think a majority of people have experienced dental fillings but the kind of materials the dentist uses is not something that is really discussed.’

Dr Yin and colleagues analysed data from almost 15,000 people to identify a link between dental fillings and potential mercury poisoning for the first time.

Fillings are put together using mercury, silver, tin and copper to form a liquid called dental amalgam which then hardens.

Mercury makes up about 50 percent of the compound and is used to bind the metals and provide a strong, hard, durable product.

The average Briton has seven fillings (Rex)

But it contributes significantly to prolonged mercury levels in the body, according to the findings published in Ecotoxicology and Environmental Safety.

‘This study is trying to provide the most accurate levels of exposure which will form the scientific basis to make future risk assessment,’ said researcher Professor Yu.

Dental amalgam has been the most popular dental filling material for over 150 years because it’s affordable and long-lasting.

Prof Yu added: ‘As toxicologists we know mercury is poison but it all depends on the dose. So if you have one dental filling maybe it’s OK.

‘But if you have more than eight dental filings the potential risk for adverse effect is higher.’

Individuals with more than eight fillings had about 150 percent more mercury in their blood than those with none found the study.