Thyroid Cancer Risk Rises With Number of Dental X-Rays

The research team, made up of scientists from Kuwait and from the cities of Brighton and Cambridge in England, studied 313 thyroid cancer patients in Kuwait and compared them with a similar number of healthy “controls.” Dental treatment in that country is free. Compared to other nations, such as Britain, Kuwait’s thyroid cancer rate is high.
   
The study is the largest such investigation on this issue to date. The scientists, led by Anjum Memon, a senior lecturer and consultant in public health medicine at Brighton and Sussex Medical School, in England, said their results “should be treated with caution, because the data were necessarily based on self-reporting by the participants. Comprehensive historical dental X-ray records were not available from the clinics.” They encourage additional research that would focus on actual dental X-rays that can have radiation doses estimated.
   
Memon, whose team was part of a partnership between Brighton and Sussex universities, and Britain’s National Health Service, said he wasn’t surprised by the results because earlier studies had noted a higher risk of thyroid cancer among dentists, dental assistants, and X-ray workers. Moreover, he said, researchers have found a connection between dental X-rays and a heightened risk of brain and salivary gland tumors.
   
As with the brain and salivary glands, the thyroid gland, located in the neck, is close to the exposure path of dental X-rays. The gland, especially in children, is sensitive to radiation.
   
Memon suggested that, if his study’s results are confirmed by further research, it would warrant a revision of dental X-ray strategy. Up to this point, dentists have used the procedure freely—to evaluate new patients and to investigate even the smallest dental question. Dentists might have to move to a much more conservative strategy such as that used for chest X-rays.

“Our study,” Memon wrote, “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 part of routine check-up or when registering with a dentist.
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The notion that low-dose radiation exposure through dental radiography is absolutely safe needs to be investigated further, as although the individual risk, particularly with modern equipment is likely to be very low, the proportion of the population exposed is high.”