Studies link dental X-rays to brain tumours, thyroid cancer, and low birth weight

Growth in dental use of CT machines raises radiation exposures dramatically

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      Carole-Anne Stanway had lived with blinding headaches for 17 years before she decided enough was enough.

      The grandmother of five in Kelowna finally asked her doctor for an MRI to see what was wrong. He refused to give her a referral, saying the headaches were just from tension. He had put her on Tylenol 3 and antidepressants, but those hadn’t helped.

      Stanway got an MRI done privately anyway, at a cost of $2,700. The result: she had three meningiomas, a type of brain tumour.

      The good news was the tumours weren’t cancerous. The bad news was the specialist didn’t want to remove them unless they became cancerous because of the risk of brain damage.

      Stanway put up with the headaches for five more years until, in 2002, they and other health problems forced her to stop working as an assistant in a medical office. She’s been on disability leave ever since.

      She has been prescribed a buffet of pain drugs, which, along with noninsured medical procedures and travel to see specialists, have drained her savings. The drugs reduced the pain for a while, but her body quickly got used to them. Then they didn’t help anymore.

      She stopped taking the pain meds five years ago after they started to cause her kidney problems. Some of the drugs also gave her severe nausea. But she’s still on the antidepressants. “Chronic pain is difficult to deal with otherwise,” she said in a phone interview from her apartment.

      A few months ago, her eyes started moving uncontrollably while she was reading, likely a side effect of meningioma, which can cause optic problems.

      Stanway said doctors don’t know what caused her meningiomas, but she thinks dental X-rays are a possible culprit. “I had a lot of dental work done when I was younger. As children, we received a lot of radiation.”

      In a study in the journal Cancer last year, 1,433 people with men­ingioma were found to be two times more likely to have had a “bitewing” dental X-ray as those without the illness. Those who reported having a panorex scanning dental X-ray (which gives a two-dimensional panoramic view of the mouth) before age 10 were 4.9 times more likely to have meningioma.

      Meningioma is the most common form of primary brain tumour (tumours that start in the brain). Women get it more than twice as often as men.

      Other studies have linked dental X-rays to thyroid cancer, breast cancer (in women who hadn’t worn a shielded apron), saliva-gland tumours, and glioma (a cancerous type of brain and spinal tumour).

      Pregnant women who got a dental X-ray were three times more likely to deliver a low-birth-weight baby (weighing less than 2.5 kilograms), according to a 2004 study in the Journal of the American Medical Association.

      Dental X-rays are the most common way Americans are exposed to human-made radiation, the 2012 Cancer study said.

      Yet despite growing awareness about the risks of X-rays, radiation in many dental offices is actually rising. That’s thanks to the explosive growth of 3-D cone-beam CT (computed tomography) machines, which give off up to 60 times the radiation of a conventional dental X-ray.

      CT manufacturers heavily market their machines to dentists, promising unsurpassed detail about a patient’s mouth. The marketing includes payments to prominent dentists to give talks to colleagues, ads in dental magazines and displays at dental conferences, according to a 2010 New York Times investigation.

      “Kids love to see that 3-D image,” one orthodontist said in a webcast sponsored by a CT maker.

      The marketing often minimizes the radiation exposure from the machines, while experts on dental radiation criticize the growing “indiscriminate use” of CT scans for routine screening, particularly by orthodontists, the story said.

      “The parents of these children have no idea about the amount of radiation used in these CT scans, and even more frightening, neither do the dentists,” Nicholas Dello Russo, an instructor in periodontology at Harvard University’s school of dental medicine, told the Times.

      Here in B.C., the first CT machine was introduced in a dental office in 2006 or 2007. Today, five to 10 percent of dental offices use one, according to Daniel Hanson of Langley-based Innovative Biomedical Engineering.

      Hanson’s company is hired by the B.C. Dental Association to inspect dentists’ X-ray machines to ensure they comply with radiation safety regulations. That doesn’t include looking at patients’ radiation-exposure records, which Hanson said no one in the province is tracking.

      Hanson helped spearhead provincial CT-machine guidelines that came out last November. Previously, no federal or B.C. standards had existed for the machines.

      “There was inconsistency in the way people were interpreting the risk from CT machines. This whole technology just exploded on the industry,” Hanson told the Georgia Straight in a phone interview while on vacation.

      The increasing use of dental CT scans is part of a trend of patients being exposed to increasing amounts of other medical X-ray radiation. In the U.S., radiation exposure from diagnostic medical X-rays has shot up more than sevenfold for the average person since the early 1980s, in large part because of the use of medical CT machines, according to a 2009 study by the U.S.-based National Council on Radiation Protection & Measurements.

      An estimated 29,000 cancers (half of them fatal) will result from the 72 million medical CT scans done in 2007 alone, the U.S. National Cancer Institute said in a different 2009 study.

      Yet only nine percent of emergency-room doctors believe CT scans increase cancer risk, and only three percent of patients think so, according to a 2004 study in the journal Radiology.

      Growing awareness of risks from dental X-rays prompted the U.S. Food and Drug Administration (FDA) in 2009 to call on dentists to reduce radiation by switching to faster-speed types of X-ray film that require less radiation.

      The fastest F-speed film typically requires 60 percent less radiation than slower D-speed film, which was used by 70 percent of U.S. dentists.

      The FDA went so far as to advise patients to pressure dentists about the issue: “Ask your dentist or dental technician if they use the faster (E or F) speed film and tell them the reasons for your inquiry.”

      The American Dental Association also recommends that dentists use F-speed film or digital imaging (which it says reduces radiation exposure by another 40 to 60 percent).

      Canadian bodies have yet to follow suit. Health Canada’s latest guidelines for dental X-ray machines date back to 2000 and don’t explicitly call on dentists to switch to F-speed film or digital imaging.

      Carole-Anne Stanway wonders if childhood dental X-rays harmed her.

      Health Canada says only: “The fastest film or film-screen combination consistent with the requirements of the examination should be used.” The guidelines do, however, say that any amount of radiation increases cancer risks. “It is generally accepted that there is no safe level of radiation dose and that no matter how low a dose is used, there is a mathematical probability of an effect.”

      The guidelines don’t mention CT scans.

      The Canadian Dental Association also doesn’t explicitly ask dentists to switch to faster-speed or digital equipment and doesn’t discuss CT machines.

      Its guidelines, which date to 2005, say: “Operators should select films of a speed and quality that will permit the production of radiographs of an acceptable diagnostic quality with minimum exposure of the patient to radiation.”

      At the provincial government’s B.C. Centre for Disease Control (BCCDC), answers were hard to come by. Francine Anselmo, head of the centre’s medical X-ray program, at first asked for questions to be sent by email. After being informed that the Straight doesn’t conduct email interviews, Anselmo said she didn’t know what percentage of B.C. dentists use D-speed film.

      When asked why her centre or Health Canada haven’t advised dentists to switch to faster film, as the U.S. FDA did in 2009, Anselmo said: “I have no idea.” Asked if she was familiar with studies linking dental X-rays to cancer, she said, “No, no, not at all.” And she replied, “Probably you’re talking to the wrong person,” when queried on whether or not her office has any concerns about radiation from dental X-rays.

      Anselmo referred further questions to her supervisor at the BCCDC, Abderrachid Zitouni, the provincial radiation specialist.

      The Straight left a phone message for Zitouni, but it was Anselmo who returned the call, asking again for questions to be emailed. Finally, another BCCDC employee, Karen Glassford, called to refer us to the centre’s media-relations person, Alex Dabrowski.

      Dabrowski, in turn, referred the Straight to WorkSafeBC, the province’s workplace-safety agency, and the B.C. Dental Association.

      At WorkSafeBC, spokeswoman Megan Johnston said her agency doesn’t deal with patient radiation safety: “Our mandate is only worker safety, so we wouldn’t be able to address questions about patient safety and exposure.”

      Bruce Ward, spokesman and a past president of the B.C. Dental Association, said his group has no position on whether dentists should switch to higher-speed film or digital X-rays. He was skeptical when asked if Health Canada or dental associations should call on dentists to make the switch.

      “I can’t say yes or no. If there was a health concern that came out, I would consider doing that. But if they [dentists] have something that works, then I don’t think there is a need to change when new technology comes along,” he said.

      Ward acknowledged, however, that patients have lots of concerns about X-ray radiation. “It’s definitely huge. In my office, it’s a conversation that happens [with a patient] at least once a day,” he said on the phone from his home in Vancouver.

      Ward said he himself switched from D-speed film to digital in his dental practice in North Vancouver seven years ago. “You want to be able to reassure people they are getting as little radiation as possible. Nobody likes to get X-rays.”

      Ward said a common patient complaint is that some dentists do routine screening X-rays regardless of whether a patient has symptoms of a problem. He said routine X-rays are inappropriate and “certainly not a policy that’s supported by anyone, anywhere. If patients feel they are having X-rays done routinely, they should have a conversation with their dentist.”

      Gina Ball, president of the B.C. Society of Orthodontists, said in an email that she was on vacation and also referred the Straight to the B.C. Dental Association.

      At the Brain Tumour Foundation of Canada, spokeswoman Megan Winkler said research is virtually nonexistent on meningioma and its causes. It’s not even clear how many people get it, much less how to prevent it.

      “It’s beyond frustrating. We need more research. If rates are going up, we need to know that so we are catching it sooner,” Winkler said on the phone from her office in London, Ontario.

      Most provinces, including B.C., don’t compile standardized data on meningioma, she said.

      At Thyroid Cancer Canada, president Rita Banach is concerned about exploding thyroid-cancer rates in Canada, which she thinks may be linked with increasing radiation exposure. Thyroid cancer is the fastest-growing type of cancer in Canada, with rates rising seven percent each year between 2002 and 2007, according to Statistics Canada.

      “That may indicate we’re getting more radiation exposure in the environment from medical sources, Wi-Fi, cellphones,” Banach said on the phone from her home in Toronto.

      “We should not be having CT scans unless it is absolutely indicated.”

      Banach is a thyroid-cancer survivor herself. She had her thyroid gland and 11 lymph nodes removed in 1999. To kill any remaining cancer cells, she was given radioactive iodine, which damaged her salivary glands and left her with dry-mouth syndrome and a chronically dry throat. She now takes thyroid hormone every day.

      “The basic question of what causes thyroid cancer doesn’t seem to be a priority, except to patients. The research is often driven by creating a drug, not on prevention. There’s no money to be made from prevention,” she said.

      Back in Kelowna, Stanway spends her time in her apartment taking in the view of beautiful Dilworth Mountain and practising her new hobby: quilting for her son and daughter and five grandchildren. Her latest project was a quilted bedspread.

      She still needs a CT scan or MRI every two years to see if the meningiomas have become cancerous. She tries not to worry about it—or about the fact that she is exposing herself to still more radiation.

      When the headaches get really bad, she tries stretching. Through it all, she somehow manages to stay cheerful. “I am a gregarious, happy individual,” she says on her Google profile. “I have the love of music throughout me…I love to try new things.”

      Her advice to others: “I would keep your dental X-rays to a minimum.”



      Refusing 2B baffled by BS

      Aug 15, 2013 at 11:18pm

      I had MANY unneccesary x-rays as a child, for cavities and braces. Feet for shoe-fitting in the 50's. Some chiropractors do it routinely, family doctors order chest x-rays for lung infections, and many dentists still x-ray it once a year - even without symptoms!

      I now have thyroid nodules that I have to get ultrasounds for every year.

      Recently I asked a mammogram tech. for a thyroid cover, and she resisted, saying it might blur the mammogram. She then had trouble finding the tiny triangular patch and had to go looking for scotch tape to keep in on my neck. Thsi was at Langley hospital, which tells you how often they ever used it! -and It didn't blur the image.

      I was also told it was a DIGITAL x-ray, making it sound safer, but it only means that the X-ray is stored as a digital file for ease of sharing and filing. You are still exposed to the same dangerous X-rays. Mammograms are also unnecessary radiation if without symptoms.

      Why are we now being told NOT to do self exams (to know our own bodies) and report changes. Must be a large research experiment!

      I've always wondered about people near x-ray machines, in other offices, outside the windows, etc. The x-ray tech covers up and keeps way, but everyone else is exposed repeatedly.

      (Please do a story on all these issues).

      Cutting down on this would safe us a fortune.
      So would limiting the number of times a pharmacist can add a dispensing fee for seniors who have Rx's delivered weekly. My mom gets charged $10. per Rx per week! x4, and medicare pays most of that, so we don't hear a lot of complaints, but it's highway robbery! These pharmacies refuse to do bi-weekly or 1 month dispensing. How do they get away with that? Stopping this would save billions!

      r adams

      Aug 16, 2013 at 5:19pm

      I work as a dental service technician in Ontario. We are very well trained by our employer and by the companies whose equipment we service. After reading this article I came away with the impression that the writer didn't know much about what they were writing about. I work with dental x ray equipment every day in offices all over Ontario. Firstly the dentists are very concerned about both the patients safety and their staff. When you make a decision to work in this field you need to be educated about radiation safety and how to take xrays properly. I am constantly asked by dentists and their staff about this issue. All forms of radiation are dangerous. radiation kills cells. Very simple stuff. Avoiding exposure at all costs is important. Most dentists one one hand like to take xrays as often as necessary to use them for diagnosing problems. However I hear many of them ask and explain that if the patient wishes they can abstain from taking xrays if they wish. Most dentists want intra orals done every two years and a Panorex every five. MOre than that is overkill. the manufacters of this equipment all have different views of how much exposure is too much exposure. Most of them tell us you would need exposures in the thousands to cause damage. None the less, any time you receive radiation there is some risk , so like anything else in life moderation is the key.
      Here in Ontario the HARP act which regulates radiation safety allows the max exposure of 360 milliretrogens per a single intra oral xray. Now when using film the required radiation would typically be in the area of 250-320 Mr , the amount of radiation when using a digital sensor in place of film would be usually around 30-80 milliretrogens. The time of exposure would be approx. 0.320 sec for film and 0.08 sec for digital. The amount of exposure is dramatically reduced. However for panorex xrays it is still high. Cephs are not too high. Hovever the new 3d xrays are somewhat high in taking 300 or so "slices" as it scans the head. The radiation is concentrated on the mouth area but I do agree with the article in that these types of exposures are only to be prescribed when necessary. You wouldn't have one of these for a checkup. All in all, working in this field I feel safe. But be careful at all costs. If you want to live a long healthy life

      Martin Dunphy

      Aug 16, 2013 at 7:13pm

      r adams:

      So, what, exactly, was it about the article that you took exception to, if you don't mind me asking?

      dental hygienist from BC

      Aug 18, 2013 at 1:39am

      Thank you r adams for your above comment. I very much agree that there is some information that is lacking from the above article. My dental office uses conventional x rays. We take bitewings annually for our patients, because they are a diagnostic tool in dentistry. With the x rays we can: detect cavities, monitor bone levels that support the teeth, see if restorations are failing, look for abscesses that can develop at the apex of the root, see if a root canal has been done properly, etc etc. Like many other procedures, every patient has the power to decline it if they wish.

      I am not familiar with CT scan use in dentistry, but I do not believe any dental professional out there will prescribe it without a rationale.

      As mentioned in the article, more research is needed to determine the cause and risk factors associated with meningioma. Before hastily coming to the conclusion, we should first take a look at the full story.

      As for amalgam fillings mentioned by Mark F, there is strong debate on whether or not they are safe. Our office still use them on molars and premolars, because they are strong and last much longer than composite fillings. Some people choose to have their amalgams changed to composites, but most of the mercury is released when the amalgams are removed. As for root canals or any other dental or non-dental procedures, there are risks (even for cleanings, there are risks like pain, bleeding, infections, etc) but the most important thing is to learn as much as you can about it, weighing the two sides and making an educated and informed decision. The human body is complicated and I do not believe you can pinpoint just one single thing as the cause for a problem.

      Ellie Kesselman

      Aug 18, 2013 at 7:49am

      Martin Dunphy:
      I don't believe that r adams WAS disagreeing with anything in the article. He mostly was elaborating on some of the details about frequency and usage of excessive amounts of x-ray exposure.

      CT-scans for dentists offices are rather scary and unnecessary sounding! Minimal use of bite-wing X-rays makes sense, although extreme care is required and done for young children. Also, using absolutely minimal exposures on bite-wing X-rays is part of good standards of care. Panorama X-rays are done as little as necessary, although I would rather do without them entirely, personally.

      Thyroid and brain tissue is vulnerable and vital! I feel very sympathetic to the woman in this article, as I have been having trouble with thyroid growths recently, for no apparent reason, and it is awful. They hurt. I am scared. I don't claim that X-ray exposure was the cause. I don't know what was.

      With most X-ray usage for diagnostics, and occasionally for chemotherapy, there is a careful consideration of whether the risks are less than the possible benefits. Dental CT scans for child entertainment purposes is shocking. Dentists and X-ray technicians are very well-informed about the effects of ionizing radiation. That is why I find this both puzzling and distressing.

      I am @EllieAsksWhy on The Twitter, if you wish to chat further.


      Aug 19, 2013 at 2:33pm

      personally I think dentistry has become quite scary - 15 yrs ago you had a dentist clean check you teeth, simple and everyone turned out just fine. today you have gadgets galore, scanning machines circling you head, several other xrays, and numerous other equipment even a screen that shows how much your dental plan is being bilked! big business dentistry - more concerning for all the children who maybe getting needlessly exposed to high levels of xrays in a year!


      Aug 19, 2013 at 3:32pm

      There is no reason anymore for film based xrays. When was the last time you took a roll of film to the drug store for processing? I would guess for most people, not in a long time. Digital xray sensors require less than 60% of the exposure time of film, allow overall better diagnostics (think Photshop) and improve staff time and complexity. If you see an old film processor in a dental office I would certainly think twice about using their services - it's like something from the stone ages and shows the doctor is out of date or doesn't care enough about patient care to spend the money on upgrading to digital. While the intial costs for offices switching from film to digital is high, the overall operating costs are less as there is no film or processing chemicals required and save considerably on staff time.

      The truth is radiation exposure for both bite-wing and panoramic xrays is signifigantly reduced with digital technology. I'm to understand there has not been a change in the overall amount of xrays doctors are taking of their patients for diagnostics and most follow the standard of practise that's been in place for decades. This means the overall xray exposure for both new and older patients has been reduced overall in the decade since digital systems have been introduced. While I won't speculate on the source of Mrs. Stanway's ailments, standard dental xrays are a nessesary evil in the greater good of your oral health.

      But as for CT scans... although these too have seen signifigant reduction in the amount of xray exposure required to run diagnostics, their reduction in price and cool factor have certainly increased their use. But they are not typically supported by insurance plans and the $400-800 scan fee is a bit much to swallow for the average patient unless no other diagnostic imaging is suitable. However,in the case of implants it's a necessity - no sense permanently damaging nerves that was more commonly the case when only panoramic xrays were used for this purpose. I'm not sure if an orthodonist scanning a kid for braces is the best idea but there is no denying the imaging ability of CT scans, with responsible use and advice, are very powerful diagnostic tool.

      I'm note sure we should be so much alarmed at the dental xray exposure itself, as much as the need to mainting patient education and awareness towards their treatment plans


      Aug 19, 2013 at 5:00pm

      @Refusing 2B baffled by BS

      While CT scanners need specific sheilding including double drywall and at times, lead sheeting, normal intraoral digital xrays (ie/bitewings) scatter and lose their energy expodentially by distance. Within 10 feet they would not penetrate drywall. At 20 feet the xrays would be unlikey to penetrate a few sheets of paper. Bytander exposure is typically not a concern in a modern dental office.

      Peter Casson

      Aug 24, 2013 at 8:57pm

      I went to a new Vancouver Dentist a couple of years ago for my first appointment and he told the Technician to give me some x-rays. I inquired how many there would be and she told me 15 in total to get my entire mouth. I told the Dentist that this was unacceptable and was way too much exposure. I told him 5 x-rays would be the maximum I would accept and said I would take my chances in the future if something went wrong with my teeth.
      Later he told me: "x-rays were safe"
      I had a few more appointments with him to complete my evaluation of his professional performance but I finally decided to part ways.