Are X-Rays at the Dentist Causing the Most Common Type of Brain Tumor?

If you go to the dentist for the recommended twice yearly check-up, chances are every once in a while you're biting down on a tab and having a circular tube take an X-ray of your teeth, searching for dreaded decay. A new study published in the journal Cancer is saying there could be a link between these X-rays and the most common form of brain tumors: meningioma.

Before panic ensues and you cancel all your dentist appointments -- don't do that -- know that meningioma is usually benign, although it is often associated with some symptoms such as headaches.

The Washington Post reports the study found those who had meningioma were twice as likely to also have had a type of dental X-ray called "bitewing X-rays" in their life. A bitewing X-ray is one showing both the upper and lower teeth and how they touch each other allowing the doctor to search for areas of decay between teeth, among other things.

CNN reports the average age of the 1,433 patients in the study was 57, with a range from 20-year-old to 90-year-old participants. The average age links the potential that those with brain tumors could have been exposed to higher levels of radiation than are currently used today. The study also evaluated 1,350 people who did not have meningioma.

Patients who had Panorex X-rays, those that take an image of all the teeth in one around-the-head-shot, at 10 years old or younger were reported as 4.9 percent more likely to have the tumor.

The Washington Post has more on the findings:

The study reports that ionizing radiation is the major environmental risk factor for meningioma and that dental X-rays are the most common artificial source of exposure to ionizing radiation in the United States.

Lead author Elizabeth Claus, professor at the Yale School of Public Health and a neurosurgeon at Brigham and Women’s Hospital in Boston, noted that risk factors for meningioma, the most commonly diagnosed form of brain tumor, remain poorly understood, in part because meningioma was only added to brain tumor registries in the United States in 2004.

To Claus, this study shows that people might be getting X-rays more often than they should. The Food and Drug Administration only recommends adults get X-rays every two to three years, depending on their propensity to develop cavities, and children every one to two years. CNN has more on these thoughts:

There's currently a low threshold for dentists to order dental X-rays, says Dr. Keith Black, director of the Maxine Dunitz Neurosurgical Institute at Cedars-Sinai Medical Center in Los Angeles, who was not involved in the study. Even if X-rays are not necessary for a procedure, dentists often request them as part an annual exam. Black hopes dentists will pay attention to this research linking the X-rays to brain tumors.

There are important uses for dental X-rays in making decisions regarding certain procedures. But if the teeth are otherwise healthy, Black recommends against the radiation.

The dental community is saying the study has some flaws that would need to be fixed and the re-evaluated before the findings could be taken seriously as a correlation. For example, those in the study were going by memory that they'd had the X-rays, not based on their dental record. Here's what the American Dental Association said in a statement about the research:

The ADA has reviewed the study and notes that the results rely on the individuals’ memories of having dental X-rays taken years earlier. Studies have shown that the ability to recall information is often imperfect. Therefore, the results of studies that use this design can be unreliable because they are affected by what scientists call "recall bias."   Also, the study acknowledges that some of the subjects received dental x-rays decades ago when radiation exposure was greater.  Radiation rates were higher in the past due to the use of old x-ray technology and slower speed film.  The ADA encourages further research in the interest of patient safety.

Claus has said she doesn't want these findings to be a cause for panic but that it be a conversation between patients and their dentist.