In recent years several studies, independent of each other, have found that thyroid cancer risk increases as the number of dental x-rays taken grows. On average, research shows that the incidence rates of thyroid cancer have doubled, from 1.4 per 100,000 in 1975 to 2.9 per 100,000 in 2006.
Several factors are probably involved in the thyroid cancer increase, and sensitive diagnostic techniques should not be considered to account for all of it. However, all the studies provide good evidence to warrant further research in settings where historical dental x-ray records are available and where radiation doses can be estimated.
Over the course of the years, countries with free dental treatment, such as Kuwait, have had higher incidences of thyroid cancer compared to countries where dental treatments are not free, like England.
Moreover, there have been several studies reporting an increased risk of thyroid cancer in dentists, dental assistants, and x-ray workers, suggesting that multiple low-dose exposures in adults may also be significant. Dental x-rays have also been linked to an increased risk of brain and salivary gland tumor.
The thyroid gland is located in the neck, and is exposed to radiation from many dental x-rays. This gland is sensitive to ionizing radiation, especially in children. Dental radiography, a source of low-dose diagnostic radiation, is frequently ignored as a potential risk to the thyroid gland.
The public health and clinical implications of these findings are particularly relevant in the light of increases in the incidence of thyroid cancer in many countries over the past 30 years. While more research is needed, the use of x-rays in general and for routine check-ups in particular, might need to be reconsidered in the near future.
Dr. Larian is a Beverly Hills thyroid expert, and available for consultation. For more information, call our office at 310.461.0300.