Frequent dental X-rays, particularly in childhood, may be linked to an increased risk of the most common brain tumor in adulthood, say researchers who suggest minimizing the use of X-rays, especially among people without symptoms of tooth or gum problems.
Dr. Elizabeth B. Claus, an epidemiologist at the Yale School of Medicine in New Haven, Conn., and at Brigham and Women's Hospital in Boston, led the new study suggesting an association between mouth X-rays and tumors called meningiomas. The tumors, which take their name because they arise in the meninges, the membrane surrounding the brain and spinal cord, account for about a third of brain tumors detected in the United States. Although they're most often benign and slow-growing, they can cause disability by exerting pressure on the brain.
Having once-yearly or more frequent bitewing X-rays, which expose a small piece of film placed between the teeth to a beam of radiation, raised the risk for meningiomas 1.4 to 1.9 times, Claus and her colleagues found. A panoramic X-ray that sweeps around the head to grab a view of all the teeth -- often to assess the need for braces -- nearly quintupled the risk of developing a meningioma if performed before a child's 10th birthday, the team reported.
After reviewing the new research, the American Dental Association issued a statement reiterating its longstanding position that dentists should order dental X-rays "only when necessary for diagnosis and treatment. Since 1989, the ADA has published recommendations to help dentists ensure that radiation exposure is as low as reasonably achievable," the ADA said in a statement, released to coincide with online publication today of the new study in Cancer, the journal of the American Cancer Society.
The ADA currently recommends X-rays every 1-2 years for healthy children and every 2-3 years for healthy adults.
Claus and her research colleagues reviewed histories of dental X-rays among 1,433 patients diagnosed with meningiomas between the ages of 20 and 79 in 2006-2011 and compared them with dental X-ray histories of healthy subjects matched for age, gender and geography. All were asked to recall dental X-rays they'd ever received.
Reaction to the study was mixed among doctors and dentists contacted by ABC News.
Dentists long have relied upon X-rays to look beyond the surface of teeth and gums for signs of cavities, infections or to visualize bones and ligaments affecting the bite. However, X-ray doses in decades past were several times higher than doses used in today's digital devices, the researchers, the ADA and outside experts agreed.
"The current study is well-done and confirms that even in the 'modern era' radiation exposure from repeated dental X-rays conveys an increased risk of these tumors," said Dr. David Schiff, co-director of the University of Virginia Neuro-Oncology Center, told ABC News.
The risk of meningioma is only 3 cases for every 100,000 people, "low enough that you can miss it without a good scientific study," said Dr. Keith L. Black, chairman of neurosurgery at Cedars-Sinai Medical Center in Los Angeles, who said there's need for a bigger, well-designed study.
X-rays employ ionizing radiation, the potentially DNA-damaging radiation that poses the greatest environmental risk for developing a meningioma. Dentists like to reassure patients that X-rays expose them to very low doses, well below naturally occurring radiation they get from the atmosphere and radioactive elements in soil.