Dental X-rays may potentially increase risk of thyroid cancer and meningioma

dental x-raysRepeated exposures to dental X-rays is associated with an increased risk of thyroid cancer and meningioma.

A team at the Brighton and Sussex Medical School (BSMS) led by Professor Anjum Memon, chair in epidemiology and public health medicine, showed repeated exposures to dental X-rays is linked with an increased risk of thyroid cancer and meningioma.

Meningioma is a tumour of the layers of tissue called meninges that surround/protect the brain and spinal cord.

Approximately the UK diagnoses 3,500 new cases of thyroid cancer and 1,850 cases of meningiomas each year.

The incidence of both cancers has increased in many countries during the past three decades.

For thyroid cancer, much of this increase is probably due to increased surveillance, screening and over-diagnosis.

However, the researchers believe other causes need investigation.

Organs exposed to radiation from dental X-rays include the thyroid gland, situated in the neck, and the meninges, which covers the brain and spinal cord.

Both organs are highly radiosensitive, particularly in childhood and adolescence.

Dental X-ray exposure

The review and analysis summarised the findings from all the previously published studies on dental X-rays exposure.

It considered the risk of thyroid cancer, meningioma and other cancers of the head and neck region.

The team advised the results of their research are treated with caution.

This is because studies did not include individual organ doses and ages at exposure, and are subject to recall bias and other limitations.

The researchers said that their synthesis provides good evidence to warrant more research.

Professor Memon said: ‘Many patients are exposed to dental X-rays on multiple occasions over many years.

‘Given this high life-time prevalence and frequency of exposure, even a small associated increase would be of considerable public health importance.’

These findings are relevant in light of the increasing incidence of thyroid cancer and meningioma in many countries.

‘Our study highlights the concern that dental X-rays are prescribed when the patient has a specific clinical need.

‘It should not be as a standard part of evaluation for new patients, for routine check-up, or for periodic screening for dental caries/decay in children/adolescents.

‘Current UK, European and USA guidelines stress the need for thyroid shielding during dental radiography.’

Long-term dental records

Professor Memon also stressed that the findings highlight the need for maintaining comprehensive long-term dental X-rays records.

These could follow the patient when they register with a new dentist – thus avoiding the need for unnecessary X-rays.

‘The notion that low-dose radiation exposure through dental radiography is completely without risk needs further investigation.

‘Although the individual risk, with modern technology and equipment, is low, the proportion of the population exposed is high.

‘Considering that about one-third of the general population in developed countries is routinely exposed to one or more dental X-rays per year, these findings manifest the need to reduce diagnostic radiation exposure as much as possible.’

The research team consisted of Professor Anjum Memon with Dr Imogen Rogers, Dr Priya Paudyal and Dr Josefin Sundin.

The study is published in the journal Thyroid (published by the American Thyroid Association).

The authors have called for further studies based on dental X-rays records and patient follow-up.