Scientists are warning that having 10 dental X-rays during a lifetime could increase the risk of thyroid cancer more than fivefold.

The Daily Mail reports that lead researcher Dr Anjum Memon from Brighton and Sussex Medical School and colleagues asked 313 thyroid cancer patients and a comparable number of healthy volunteers how many dental X-rays they had been given during their lifetime.

The team factored in any hospital or other X-rays the study group might have undergone and found that the risk of developing thyroid cancer increased five-and-a-half times with 10 X-rays or more – and having just four dental X-rays doubled the risk of developing thyroid cancer, compared with those who had never had a dental X-ray.

Dentists usually cover patients with lightweight lead collar and bibs when administering dental X-rays. However, most dentists carry out an X-ray procedure routinely when examining new patients for the first time and the researchers are warning that this practice should stop, with X-rays only being offered for clinical reasons.

The incidence of thyroid cancer has more than doubled over the last 30 years and the team says that the implication of dental X-rays in this has been ‘overlooked’.

The thyroid is a gland as the base of the neck, which releases and controls hormones.

Dr Memon carried out the research in collaboration with teams from Cambridge and Kuwait universities.  He said:

'It is important that our study is repeated with information from dental records, including frequency of X-rays, age and dose at exposure.

'If the results are confirmed, then the use of X-rays as a necessary part of evaluation for new patients and routine periodic dental radiography at six to 12 months interval – particularly for children and adolescents – will need to be reconsidered, as will a greater use of lead collar protection.’

However, dentists in the UK have pointed out that the research was carried out in Kuwait, where thyroid cancer is more common than in the UK. It is also not known what equipment was used for the X-rays, they added.

Chief executive of the British Dental Health Foundation, Dr Nigel Carter, said:

'The number of X-rays being taken in dental practice in the UK has greatly reduced in recent years and the dosages from modern equipment are extremely low.’

The research is published in the journal Acta Oncologica.

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