About 3,500 new cases of thyroid cancer and 1,850 cases of meningiomas are diagnosed each year in the UK, and 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 (i.e. detection of a cancer that would not ultimately cause symptoms), but the researchers believe other causes need investigation.
The thyroid gland is situated in the neck and the meninges cover the brain and spinal cord - these organs will be exposed to radiation from dental X-rays. Both organs are highly radiosensitive, particularly in childhood and adolescence. Dental radiography, a source of low-dose diagnostic radiation, is often overlooked as a potential hazard to these organs.
More research is need to further test the hypothesis
The researchers conducted a systematic review and meta-analysis, which summarised the findings from all the previously published studies on dental X-rays exposure and the risk of thyroid cancer, meningioma and other cancers of the head and neck region. They said the results of their research should be treated with caution because these 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 based on dental X-rays records and patient follow-up to test the hypothesis further.