Last week the American Cancer Society published Yale University research findings that dental patients who received frequent dental X-rays a generation ago, are at greater risk for developing meningioma, a non-cancerous brain tumor.
The Yale study involved more than 1,400 dental patients from around the U.S. who were diagnosed with the non-cancerous tumor. The study also tracked a similar group of dental patients who did not have a meningioma.
What the Yale researchers discovered is that patients with meningioma were twice as likely to have had dental X-ray exams where they bit down on a tab of X-ray film at least once a year when they were children.
An even greater link was discovered between meningioma and the single X-ray outside of the mouth. Dental patients who had the panorex dental exam when they were younger than 10-years-old had almost five times greater the risk for meningioma.
Since the research publication dentists have found themselves on the defensive regarding dental X-rays.
The American Dental Association released a statement on the study asserting the following, “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.'”
In the ADA statement, Dr. Alan G. Lurie, a radiation biologist and head of radiology at the University of Connecticut School of Dental Medicine, voiced concerns about the study’s design and outcomes. “I think it’s a very flawed study,” said Dr. Lurie, who is also president of the American Academy of Oral and Maxillofacial Radiology.
He characterized at least one outcome of the study—reflected in a table that related meningioma risk to types of dental X-ray examination—as “biologically impossible.”
Said Dr. Lurie, “They have a table, Table 2, in which they ask the question, `Ever had a bitewing,’ and the odds ratio risk from a bitewing ranges from 1.2 to 2.0, depending on the age group. Then they asked ‘Ever had full mouth’ series, and the odds ratio risk from a full mouth series ranged from 1.0 to 1.2.
“That’s biologically not possible because the full mouth series has two to four bitewings plus another 10 to 16 periapicals. A full mouth series, just to round things off, is 20 intraoral X-rays of which two to four are bitewings. They are showing that one bitewing has 50 to 100 percent greater risk than a full mouth series that has multiple bitewings plus a bunch of other films. That’s biologically not possible.”
Explaining this gross internal discrepancy is difficult, as the epidemiologic and statistical methods are widely accepted, Dr. Lurie said. He attributes the perceived discrepancy in the data to possible recall bias in the patients involved in the study.
“Epidemiologists are very aware of this bias,” Dr. Lurie said. “What happens is you’re asking people to remember what kind of dental X-rays they had 10, 20, 30 or 40 years ago. It’s anecdotal, and the argument is that it’s just as anecdotal for the group without meningiomas as it is for the group with meningiomas. That is not necessarily true.”
In this week’s survey, The Wealthy Dentist asked dentists if the news reports will change how their dental practice uses X-rays. We are curious what dentists think about the study and if any patients are calling dental practices questioning X-rays.
To take part in the survey, click here, or leave us a comment and tell us your thoughts on dental X-rays and this study.
For more on this study see: ADA Releases Statement on Dental X-rays Study