A new research study by a medical team at Brighton and Sussex Medical School (BSMS) have showed that repeated exposures to dental X-rays
are associated with an increased risk of thyroid cancer
Globally, about 347,000 new cases of thyroid cancer
and 189,000 cases of meningiomas
are diagnosed each year 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 as well.
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.
The medical 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
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.
Professor Anjum Memon told Thailand Medical
News, “Little is known about the impact and magnitude of risk associated with dental X-rays
, which have been the fastest growing source of human exposure to low-dose ionizing radiation during the past three decades with many patients being 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 in cancer risk would be of considerable public health importance.”
Unfortunately, many clinics and hospitals in Asia including Thailand do not practice thyroid shielding protocols during dental X-rays.
Professor Memon further added “The clinical and public health implications of these findings are relevant in light of the increasing incidence of thyroid cancer
in many countries. Our study highlights the concern that like chest (or other upper body) X-rays, dental X-rays
should be prescribed when the patient has a specific clinical need and not 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. The findings also stress the need for maintaining comprehensive long-term dental X-rays r
ecords, which could follow the patient when they register with a new dentist thus avoiding the need for unnecessary X-rays.”
Professor Memon concluded: “The notion that low-dose radiation exposure through dental
radiography is completely without risk needs to be investigated further. Although the individual risk, with modern technology and equipment is likely to be very 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 of Professor Anjum Memon with Dr Imogen Rogers, Dr Priya Paudyal and Dr Josefin Sundin called for further studies based on dental X-rays
records and patient follow-up.
In the meanwhile, patients are advised to avoid and reject unnecessary dental x-rays
that are called by healthcare professional or hospitals and also to ensure that during such x-rays, thyroid shielding protocols are abided by.
Reference: Dental X-Rays and the Risk of Thyroid Cancer and Meningioma: A Systematic Review and Meta-analysis of Current Epidemiological Evidence ,Anjum Memon, Imogen Rogers, Priyamvada Paudyal, Josefin Sundin, 2019 https://doi.org/10.1089/thy.2019.0105