Published on April 20, 2012 by admin
Recently, the media has given a lot of attention to a study from Yale linking dental x-rays to brain tumors. Studies such as these tend to resurface every few years, and each time the science behind the study is found to be flawed. The full journal article of the study can be found at the following web address http://onlinelibrary.wiley.com/doi/10.1002/cncr.26625/full.
To put it in lay man’s terms, patients with brain tumors were asked if they had dental x-rays during different stages of their lives. Based upon these surveys, the authors of the article conclude there is a link between exposure to some dental X-rays in the past and Meningioma. Based upon this methodology, I could ask the same questions regarding eating tomatoes and come up with the same conclusion, that tomatoes cause brain tumors.
Surveys are a very weak method of science because they are often inaccurate. Even the study’s authors point out the association between dental x-rays and brain tumors is softened by the fact that most of the exposure to x-rays in the study took place in the 1960s – when doses were much, much higher than they are today. They also point out that we are relying upon patients recalling what happened more than 40 years earlier.
This is, however, a good opportunity to have a discussion regarding dental x-rays and what they mean to our health. Using REM (Roentgen Emission Man) – the traditional units to measure the amount of radiation to which we are exposed – the amount of radiation you receive from background cosmic radiation is about 350 millirem, whereas the amount you receive from a single dental x-ray is less than 3 millirem (the same as a cross country plane flight). This isn’t very much. By comparison, a mammogram provides about 500 millirem per breast, the same amount of radiation you receive from an x-ray of the lumbar spine. This still isn’t very much, thus mammograms are ordered regularly for patients.
We at the Nephi Dental Clinic have the highest concern for your overall health. We will not put your health at risk. Dental X-Rays are a vital tool in diagnosing dental disease. Without x-rays, we cannot properly perform the task in which you trust us, to care for your oral health. Doing dentistry without x-rays is like driving a car on a very dark night with no headlights. It can be done, but we wouldn’t recommend it. Our digital X-Ray units emit the lowest possible radiation. We will always be committed to staying up-to-date on the best treatments for our patients and staying current on the medical literature to better serve our patients.
The following is an article released by the ADA (American Dental Association) regarding this topic.
ADA releases statement on dental X-rays study
By Jean Williams, ADA News staff
A study published online April 10 associating dental radiographs with brain tumors has stirred media attention and questions from experts on the study’s methodology.
The study published in Cancer, an American Cancer Society peer-reviewed journal, found that people with meningiomas (typically, benign brain tumors) are more likely to report that they’ve had certain dental X-ray examinations in their lifetimes.
In a press statement following publication of the study online by Cancer, the ADA referred to their recommendations for prescribing radiographs, which help dentists determine how to keep radiation exposure as low as reasonably achievable.
“The ADA has reviewed the study and notes that the results rely on the individuals’ memories of having dental X-rays taken years earlier,” says the April 10 statement. “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.’ ”
The ADA released its statement in tandem with the lifting of the press embargo on the study. U.S. News and World Report and MSNBC interviewed Dr. Matthew Messina, a practicing dentist in Ohio and ADA media spokesperson. Several other media outlets cited the ADA’s recommendations on dental X-rays.
In “Dental X-Rays and Risk of Meningioma,” the authors, led by researcher and neurosurgeon Elizabeth B. Claus, M.D., of Yale University School of Medicine and Brigham and Women’s Hospital, conclude that “exposure to some dental X-rays performed in the past, when radiation exposure was greater than in the current era, appears to be associated with an increased risk of intracranial meningioma.”
Using anecdotal evidence, the population-based, case-control study compared dental and therapeutic radiation histories in 1,433 patients who had intracranial meningiomas diagnosed between ages 20 and 79 with a control group of 1,350 patients. Data collection involved interviews and questionnaires and relied on the patients’ recall of details related to dental care received over their lifetimes. According to the study report, “Participants were asked to report the number of times they had received bitewing, full-mouth, or panoramic films” during four stages in life: before age 10, between ages 10 and 19, between ages 20 and 49 and up to age 50.
Dr. Alan G. Lurie, a radiation biologist and head of radiology at the University of Connecticut School of Dental Medicine, has many 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.”
Individuals who had meningiomas and had surgery for them in this study population may be more likely to remember having had X-rays than individuals who did not have meningiomas, Dr. Lurie said.
Dr. Lurie emphasized that his comments on the dental X-rays study are his own. “They’re not necessarily the views of the Academy,” he said, noting that the AAOMR was preparing an official response to be released this week.
A broad range of local, national and international media reported news of the dental X-rays study, including ABC World News with Diane Sawyer, CBS This Morning, Good Morning America, USA Today, The Sun (United Kingdom), The Daily Mail (United Kingdom) and others.