Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror
Medicine News Science

Dental X-Rays Linked To Common Brain Tumor 248

Posted by timothy
from the tradeoffs-are-everywhere dept.
redletterdave writes "A new study suggests people who had certain kinds of dental X-rays in the past may be at an increased risk for meningioma, the most commonly diagnosed brain tumor in the U.S. Dr. Elizabeth Klaus, the study's lead author and a professor at the Yale School of Medicine, discovered that dental X-rays are the most common source of exposure to ionizing radiation — which has been linked to meningiomas in the past — and that those diagnosed with meningiomas were more than twice as likely as a comparison group to report ever having had bitewing images taken. And regardless of the age when the bitewings were taken, those who had them yearly or more frequently were between 40 percent and 90 percent higher risk at all ages to be diagnosed with a brain tumor."
This discussion has been archived. No new comments can be posted.

Dental X-Rays Linked To Common Brain Tumor

Comments Filter:
  • by medv4380 (1604309) on Tuesday April 10, 2012 @09:33AM (#39630731)
    A valid reason to avoid the dentist
  • not sure (Score:2, Interesting)

    by Anonymous Coward

    I'm a dental student, and I have been taught that - with modern equipment - exposure to radiation from 2 bitewings is about the same as half a day of ski holiday. You really need to take a lot x-rays to expose patients to significant more ionizing radiation than they receive from nature itself.

    • by Anrego (830717) *

      Along these lines, my dentist once told me that the lead apron they have you wear is more for patients peace of mind then necessity.

      • by Flammon (4726)

        Ya, and that's why they leave the room when taking the x-ray.

        • by Anrego (830717) *

          That actually seems reasonable enough to me. I mean, one x-ray every 9 months.. probably not bad. Being in the same room with dozens of x-rays a day .. that might cause problems.

    • by Skidborg (1585365)
      Key word being "modern equipment". It's not like most dental offices are just thrilled to discard their insanely expensive, decades-old X-ray machine and buy a brand new insanely expensive machine that does the same thing.
      • Usually the machine you think of as the "decades-old X-ray machine" isn't discarded and isn't insanely expensive; a new X-ray can be had in the $1.2 - 2.5K range. The magic sauce is the film, the people in the study, as old as 79 were likely X-rayed with the very old and slow C speed film, new film E and F speed is much faster alowing reduced exposure; changing to a faster film is trivial. Next comes the Phosphor storage screen, used like film, but laser scanned and digitalized, way faster than film but co

    • Holy X-Ray batman. I live in a ski area!!!!! I'm a goner. Nice knowing you all.
    • Re:not sure (Score:5, Insightful)

      by Remus Shepherd (32833) <remus@panix.com> on Tuesday April 10, 2012 @10:09AM (#39631247) Homepage

      I'm a dental student, and I have been taught that - with modern equipment - exposure to radiation from 2 bitewings is about the same as half a day of ski holiday.

      These comparisons are always misleading, because they ignore the density of the radiation received. Radiation from half a day of ski holiday is diffused over your entire body. The radiation from bite wing X-rays is concentrated on your teeth and skull. The concentration matters.

      Let's use a better analogy. The energy at the focal point of a magnifying glass might be one-hundredth the amount of energy you get from standing out in the sunshine. But because that energy is concentrated into a small point, it will burn your skin.

      We survive nature not because it isn't powerful, but because its power is spread out. That power gets dangerous when mankind focuses and purifies it.

      • by malakai (136531)

        Point is, it's as likely that the film you bite down on and the plastic it's covered in turns out to be carcinogenic. We're talking a very small amount of radiation here.

      • by blueg3 (192743)

        The concentration matters.

        Not really. It's still well below the acute-effect threshold. Cancer, as far as we can tell, is a long-term, low-probability effect that is linear in the total amount of exposure. Being concentrated in one place over another may well influence what body parts have a higher probability of getting cancer, but in terms of total probability, concentrating the radiation in time (short exposure) or space (concentrated area) has no effect. Linear relationship means that only total dose matters.

        • by jd (1658)

          But it cannot be a linear effect. The ionizing events may be linear, but the body's ability to deal with damage will be non-linear -- approximating to linear only over a small enough number of events. It is also now known that the probability of mutation events in DNA differs substantially along its length - two or three orders of magnitude isn't unusual. Some areas of DNA are unimportant, others more so. Approximating everything to linear relationships doesn't work.

          Also, the vast majority of what we know a

      • Re:not sure (Score:5, Informative)

        by bcrowell (177657) on Tuesday April 10, 2012 @12:01PM (#39633175) Homepage

        >> I'm a dental student, and I have been taught that - with modern equipment - exposure to radiation from 2 bitewings is about the same as half a day of ski holiday.

        >These comparisons are always misleading, because they ignore the density of the radiation received. Radiation from half a day of ski holiday is diffused over your entire body. The radiation from bite wing X-rays is concentrated on your teeth and skull. The concentration matters. Let's use a better analogy. The energy at the focal point of a magnifying glass might be one-hundredth the amount of energy you get from standing out in the sunshine. But because that energy is concentrated into a small point, it will burn your skin.

        Unsurprisingly, the dental student's professor knows more about this than you do. The professor's analogy is the correct one. Yours is the incorrect one.

        When x-rays cause cancer, it's a statistical process. Each x-ray photon has some small probability P of damaging a cell's DNA in such a way as to make it cancerous.

        When you go skiing in the mountains, you're exposing yourself to more cosmic rays than you get at sea level. These are high-energy charged particles, not x-ray photons, but the statistical nature of the process is the same.

        When you burn your skin with a magnifying glass, there is nothing statistical about the process. The outcome is deterministic. You're simply transporting x amount of energy into a certain piece of your flesh, raising its temperature by y degrees.

        In case it matters, I have a PhD in physics, my field is nuclear physics, and I have worked with ionizing radiation a lot.

        The only thing I would add to the correct information that the GP related from his/her professor is that in addition to the possibility of causing cancer, radiation can also make you healthier, via a well-documented effect called radiation hormesis. The usual interpretation (which is hard to test empirically) is that the radiation stimulates your cells' damage-control mechanisms. At the very low doses we're talking about, the evidence from controlled animal studies is that the net effect on your health is positive, because the hormesis effect is orders of magnitude stronger than the negative effects of the radiation.

        • It is my understanding that our DNA has repair mechanisms that will fix some of these radiation-induced errors, but that these repair mechanisms are quite slow, so total dose is not as important as how quickly it is received. The parent here is correct, except that density over time is also important. I suggest brushing up on radiation safety before you work with any more of that ionizing radiation ;)
          • by jd (1658)

            You are correct, although the repair mechanism is not all that good and ONLY exists in nucleic DNA (there is no repair mechanism in mitochondrial DNA).

            Dosage over time is important, which is why the maximum safe dose is given as a dose per unit of time. However, in the better tables, the maximum safe dose per year is NOT 365.25x the maximum safe dose per day. The calculations are not simple ones and are constantly under revision. I imagine that with this new data on dental X-Rays that the safe dosage calcul

        • Re:not sure (Score:5, Interesting)

          by Remus Shepherd (32833) <remus@panix.com> on Tuesday April 10, 2012 @01:51PM (#39635123) Homepage

          In case it matters, I have a PhD in physics, my field is nuclear physics, and I have worked with ionizing radiation a lot.

          Masters' in physics here with a similar background to yours.

          My point is that the statistical likelihood of damage due to radiation depends upon its flux. For the same amount of incident energy, the flux you receive across your entire body is lower than if the same energy were collimated and aimed at your skull. The same number of photons in a smaller area increases the risk in that area. So saying that a dental X-ray has the same energy as a full-body soak in low-level radiation is deceptive. The dental X-ray is over a much smaller area, has a higher incident flux, and therefore has a larger chance to cause damage in that specific region.

          The only thing I would add to the correct information that the GP related from his/her professor is that in addition to the possibility of causing cancer, radiation can also make you healthier, via a well-documented effect called radiation hormesis. The usual interpretation (which is hard to test empirically) is that the radiation stimulates your cells' damage-control mechanisms. At the very low doses we're talking about, the evidence from controlled animal studies is that the net effect on your health is positive, because the hormesis effect is orders of magnitude stronger than the negative effects of the radiation.

          And this makes me suspicious of your credentials, because hormesis is an effect usually only talked about by snake oil salesmen. It's not a reliable effect, and there's a good bit of argument against it existing at all. Even if it does exist it is not something you want to play with, as a very small change of dose can drive your exposure from 'beneficial' to 'really dangerous'. If you're relying on hormesis to keep you safe then you are begging for disaster.

    • The article sort of touches on this:

      Lurie also echoed Claus' caution that radiation levels from dental X-rays when some of the participants were younger was much greater than is used now.

      The result may be different if everyone had used today's equipment the whole time.

  • by Daetrin (576516) on Tuesday April 10, 2012 @09:35AM (#39630761)
    They give you this big heavy blanket (lined with lead? I dunno) to lay across your body when they do the x-ray. They seem to think it's important to block off the areas they're not actually imaging. So why don't they give you something similar to lay across the top half of your face and head? Obviously it wouldn't stop everything, but you'd think it would help at least a little.
    • by houstonbofh (602064) on Tuesday April 10, 2012 @09:41AM (#39630859)
      Because it is bouncing off your teeth and jaw so the cap would keep it in.
      • Lead doesn't reflect radiation, it absorbs it. But that's irrelevant because "bouncing off your teeth and jaw" is equally flawed. X-Rays and other forms of ionizing radiation don't "bounce off" surfaces, it will either pass through, be absorbed, or trigger another particle to be emitted. There are 3 types of radiation that may be emitted, alpha, beta, and gamma. Alpha and beta will only penetrate a few millimeters of solid/liquid matter such as skin, muscle, etc so those won't make it back out of the body.

        • by blueg3 (192743) on Tuesday April 10, 2012 @11:40AM (#39632759)

          X-Rays and other forms of ionizing radiation don't "bounce off" surfaces, it will either pass through, be absorbed, or trigger another particle to be emitted.

          I assure you that all kinds of ionizing radiation can reflect. X-rays can reflect -- they make X-ray mirrors, usually out of highly-polished beryllium. It's more effective at small reflection angles (glancing reflection). You can even make X-ray fiber optics (glass light pipes), which is a decent way of focusing an X-ray beam. These again are only really effective for glancing reflections. Alpha particles and electrons also reflect.

          Triggering another particle to be emitted is actually a subset of "be absorbed", although this isn't obvious. Photons aborbed by atoms regularly kick an electron into an excited state (or ionize it, the highest-energy excited state, in a sense). Electrons falling back into their ground states cause the emission of new photons with well-defined energies. I suppose you could also have a photon kick an electron into motion, producing a beta ray, but I don't think that occurs much in nonconductive bulk materials. (Usually you go the other way: electron beam to X-ray beam through brehmsstralung.)

          There are 3 types of radiation that may be emitted, alpha, beta, and gamma.

          Sort of. From nuclear sources. There are actually many more particles that can be emitted from particle decays, but those are the most common. More to the point, though, radiation sources used for X-rays generally don't emit alpha or beta particles. In fact, the term "X-ray" refers to a particular part of the electromagnetic spectrum. Gamma rays are electromagnetic radiation. (They conventionally referred to electromagnetic radiation within the energy range commonly emitted by radioactive materials. It's really preferable these days to call all such things "photons" regardless of their energy.) So, X-rays and gamma radiation are the same thing. Alpha and beta radiation are in no way relevant here.

          However, putting a shield over the patient's head would only protect other people in the room, not the patient, because any such radiation would coming OUT of the patient's head.

          That's only really true if the X-rays are well-collimated. Since they point the X-ray beam so that it goes horizontally through your head (more or less) and then give you a lead shield for your chest, it stands to reason that either the X-ray beam is not well-collimated or the lead shield isn't there to serve a functional purpose.

          • I assure you that all kinds of ionizing radiation can reflect. X-rays can reflect -- they make X-ray mirrors, usually out of highly-polished beryllium. It's more effective at small reflection angles (glancing reflection). You can even make X-ray fiber optics (glass light pipes), which is a decent way of focusing an X-ray beam. These again are only really effective for glancing reflections.

            Which simply affirms my statement. Yes, some small portion can be deflected, but as you noted, it's "only really effective for glancing reflections".

            Gamma rays are electromagnetic radiation. (They conventionally referred to electromagnetic radiation within the energy range commonly emitted by radioactive materials. It's really preferable these days to call all such things "photons" regardless of their energy.) So, X-rays and gamma radiation are the same thing.

            Actually, gamma [wikipedia.org] has two different uses, the older/historical definition is based upon the wavelength/energy of the radiation. That definition is now only used in astronomy (because the source of the emission can't be determined). The accepted usage in cases where the source can be determined is that gamma ray/radiation is produced in the nucleus, x-rays are pro

      • by blueg3 (192743)

        "Keep it in" only happens if the material reflects X-rays. Most materials don't reflect X-rays; it's a pain to make an X-ray mirror. They use lead, which absorbs X-rays. A lead apron (or hat) always "keeps it in" in the sense that the X-rays are converted into heat inside the lead apron.

    • by Anrego (830717) *

      My dentist once told me that the apron is more for patient peace of mind then any practical purpose these days. Given the nature of how the x-rays are delivered, it would seem a useless measure (hint: they point the thing at your head...).

      • by utkonos (2104836)
        Unless you have genetalia in your head, they are putting the lead shield in the correct place. The areas of the body that are sensitive to the type of radiation emitted by xray equipment are reproductive organs, digestive organs, and blood producing organs in descending order. The lead shield that they give you covers just those parts of your body.
    • by DarthVain (724186)

      I'm pretty if sure most people were told to put on this lead mask they would tell their dentist to f-off and forget about the xray.

  • CMOS imaging? (Score:3, Interesting)

    by AmonRa1979 (797618) on Tuesday April 10, 2012 @09:35AM (#39630771)

    Any word on whether there was a decline in this type of tumor when CMOS x-ray imaging started being used in dentistry? Using CMOS rather than film supposedly requires less exposure time or less x-ray intensity in order to obtain an image comparable to film. I see the article does comment on the decreased intensity of x-ray source now as compared to a decade or so ago, but unless they couldn't readily identify this type of tumor back then, then I would expect to have seen a decline in this type of tumor as well.

    • by Guppy (12314)

      Although the sensitivies for film and sensors have been improving, dental head CTs (which are much higher dose) have become increasingly common. While dental CTs are intended for special situations involving complex procedures, I've head of them being used in routine care as well, and it'd be interesting to know if it off-sets doage reductions elsewhere.

      • by sunwukong (412560)

        What was considered "routine care" for the CT?

        I can't think of anything in bread and butter dentistry that a CT would actually help with to any practical extent.

    • That another area where the study seems nonsensical, it assumes that every exposure is equivalent, the newer films are almost as fast as the original sensors, and some of the subjects, being as old as 79, could easily been exposed be equipment a century old containing rotary telephone exchange technology of counting pulses with mechanical relays.

  • by Sfing_ter (99478) on Tuesday April 10, 2012 @09:41AM (#39630861) Homepage Journal

    Well, at least our friends in the UK won't have to worry about this... :P

  • Flawed Study (Score:5, Informative)

    by blahbooboo (839709) on Tuesday April 10, 2012 @09:46AM (#39630929)

    This is a very flawed study that doesn't account for many things including a) It's based on patients "memories" of when they got x-rays and not actual dates b) Doesn't account for the dramatic reduction in amount of rays needed for the images in the last 20-30 years.

    Proof? Check this far better article http://articles.boston.com/2012-04-10/metro/31313701_1_x-rays-tumor-risk-radiation-exposure [boston.com]

    • Sorry, but my main objection to both the claim and counter-claim is that this is journalism, not science. Can't someone provide links to PLoS One papers? Arxiv? Cancer research group websites? I'd ask my uncle, who was a statistician specializing in cancer research, but he's retired and won't be on the cutting edge any more. This needs to be answered by researchers who have that up-to-the-microsecond knowledge.

      However, I'd also point out that the "dramatic reduction" you speak of is questionable. I've seen

  • by sirwired (27582) on Tuesday April 10, 2012 @10:52AM (#39631949)

    Firstly, where did they find their sample of people who have never had bitewings taken? If you've EVER received a dental exam, the dentist almost certainly took a set of bitewings, and probably a panorex.

    If you've actually never had bitewings takne, you probably aren't receiving dental care at all. And if you aren't receiving dental care, it's a safe bet that you are more likely (though not certain) to not be receiving quality medical either. Meaning you could have a menengioma and die without it ever being diagnosed.

    And please, please, note that even the study stated these results were based on far older radiation levels. Today's x-rays don't need nearly as much.

    Given that dental abscesses can be fatal if untreated, (in addition to poor dental health being linked to stuff far more common and deadly than brain tumors), don't refuse dental x-rays based on this report.

    • by Skidborg (1585365)
      On the other hand, try to find a dentist who has an x-ray machine manufactured more recently than the 1980's.
  • I've been having problems with frequent headaches recently and I was worried that I might have a brain tumor or something. I've been to a neurologist who had me get an MRI to eliminate that possibility (which BTW it did, phew!). I've had enough dental xrays over the years, but rarely a full mouth set. Most of the time the dentist would only take views of any teeth that looked problematic visually, or if I was complaining of pain and nothing was visual in that area. I also had localized views taken befor

  • Here is the study itself. Ignore the media, they're obviously idiots.
    http://onlinelibrary.wiley.com/doi/10.1002/cncr.26625/abstract [wiley.com]

    There are too many variables left untouched. The only reason this is getting attention is because it's from an Ivy.

    Are these digital radiographs (formal term for "x-ray")? Are these older film radiographs? What other sources of radiation are these people exposed to? What were their settings for each capture? Is it confirmed and documented? Are they travelers?

    Obviously exp

Dead? No excuse for laying off work.

Working...