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Mary Shomon

Thyroid Cancer Risk May Increase Due to Multiple Dental X-Rays

By June 29, 2010

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According to research conducted by UK and Kuwaiti investigators, and recently reported on in the journal Acta Oncologica, the risk of thyroid cancer increases with multiple exposure to dental x-rays.

The thyroid gland is sensitive to radiation, and radiation exposure is a known cause of thyroid cancer. But dental x-rays have long been overlooked as a source of radiation, given the low dose of the radiation used.

Repeated exposure, however, now appears to be correlated to an increased risk of thyroid cancer, and according to the researchers, their findings correlate to previous research that has found an increased risk of thyroid cancer in dentists, dental assistants, and x-ray workers.

The researchers found that study subjects who had up to four dental X-rays had more than double the risk of developing thyroid cancer than those who had never had a dental x-ray. Those who had between five and nine X-rays had a risk more than four times normal. And the greatest risk was for those with ten or more X-rays, whose risk was more than five times that of someone who had not received dental x-rays.

Lead investigator Dr. Anjum Memon has said that the implications of the findings are especially important, given the increased rate of thyroid cancer in the past 30 years. In the US, for example, thyroid cancer is the fastest growing form of cancer, and in the United Kingdom, the thyroid cancer rate has doubled from 1.4 per 100,000 in 1975, to 2.9 per 100,000 in 2006.

The researchers are cautioning, however, that the topic requires further research and study, especially to get a better estimate of the radiation doses and number of exposures that are more associated with an increased risk.

What Can You Do?

Given this new information, what should you do to help protect yourself against thyroid cancer?

According to the study author Dr. Memon: "Our study highlights the concern that, like chest or other upper body X-rays, dental X-rays should be prescribed when the patient has a specific clinical need, and not as part of routine check-up or when registering with a dentist. 'So, one of the first things you can do is to make sure that you get dental x-rays only when your dentist has a specific need for them, and not just as a routine part of treatment, i.e., routine annual x-rays, or a routine dental x-ray with every checkup.

Second, and this is a recommendation that I've been making for years here at the site and in my books: Ask the dentist to protect you with a lead thyroid collar when doing any x-rays. This is a recommendation that you'll also hear from About.com's guide to Dentistry, Shawn Watson, who says: "Before you have x-rays taken at your dental office, make sure the protective lead vest, that is placed over your body prior to taking an x-ray, has a thyroid collar." (My own dentist didn't even have a thyroid collar for the longest time. He used to look at me a bit strangely when I would ask that he protect my thyroid for dental x-rays. I would end up pulling the lead apron up so that it would go right up to my chin. Now he has an actual thyroid shield on his lead apron, thankfully!)

Third, if you have young children, minimize their exposure to any unnecessary dental x-rays, and insist that their dentists and orthodontists also use a thyroid collar. Children are especially susceptible to thyroid-damaging radiation, so you'll want to ensure they are not subjected to routine or unneeded dental x-rays. And for children, any essential x-rays should only be conducted with use of the appropriate lead thyroid collar.

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Photo: clipart.com

Source: Memon, Anjum et. al. "Dental x-rays and the risk of thyroid cancer: A case-control study," Acta Oncologica, May 2010, Vol. 49, No. 4, Pages 447-453. Abstract/Summary.

July 2, 2010 at 6:37 am
(1) christine Conte says:

Well, you missed the easiest answer to this problem…go to a dentist that uses digital x-rays. No radiation at all.

March 31, 2011 at 2:44 pm
(2) Mary says:
September 21, 2011 at 7:18 pm
(3) MAYAHDMD says:

not true. there is still radiation exposure albeit slightly less than conventional dental radiography.

July 2, 2010 at 7:39 am
(4) Melanie Miller says:

I am hypothyroid, and had tons of oral Xrays as a child due to a cleft palate, and have recently become more uneasy about the once-a-year X-ray “requirement’ imposed by my dentist. This year I refused it and they told me that I could go as far as once every two years, but that their liability insurance required it at least that often. What is one to say to this? I would presume it’s the same for all dentists.

October 30, 2010 at 3:12 am
(5) Sue Nnc says:

As for the dentist’s refusal to go more than two years without dental x-rays per a liability insurance requirement, I would request a liability insurance RELEASE related specifically to the x-rays for me to sign, and if they refused that I’d find another dentist.

July 2, 2010 at 7:52 am
(6) Alison says:

I expressed concern about this when I went to the dentist recently. He said the dose of radiation was miniscule (apparently you get more by sitting in the sun for an hour or so) and that these research papers are far from conclusive.

I am wondering what to think.

July 2, 2010 at 7:55 am
(7) Tony says:

I believe digital refers to the x-ray collection method (film vs. electronic capture).Therefore x-rays are still being used but the image is captured and viewed electronicly.

July 2, 2010 at 8:20 am
(8) Cindy says:

What about x-rays of the head for any diagnois? I have had several head x-rays to check my neck and shoulders plus an MRI of the head all in one year along with dental x-rays. Should I be concerned?

July 2, 2010 at 8:33 am
(9) Betty says:

Dentists are a bs. like everyone else. Money, money, money. Now my dentist has come up with a new 5-year photo scan, which she claims gives a more complete picture than the annual xrays. Since for five decades, dentistry has served me well w/o that telling 5-year photo (that comes with a high fee), I decline that 5-year photo. Since losing my dental ins. 5 yrs ago, I stick to xrays every 2 years. Sorry it puts less $ in her pocket, but I take great care of my teeth and have had no cavaties despite my cut-back in routine xrays. Wish I’d cut back on x-rays years earlier and plan to stick with my decision even though I’m about to get dental ins. w/a new job.

July 2, 2010 at 8:36 am
(10) Ducklady says:

Good luck with refusing X-rays in my area. The dentists will throw you out of their practice. I’ve simply been avoiding the dentist the past several years because of this. I have dental insurance, too, that goes unused because I refuse to have x-rays for check ups. The liability insurance business is, I suspect, a lie. I’d be happy to sign any waiver they want.

I’ve considered getting a letter from my doctor, need to ask her next time I see her. I’ve suffered to much with misdiagnosed, untreated hypothyroidism in the past 3 decades to take any risks whatsoever.

I’ve had the same problem with the chiropractor. All was well until she bought an x-ray machine. She now has to pay for it. So suddenly x-rays were “required.” She suddenly became unable to treat anyone without an X-ray, after several years in business!

This is all about paying for the machine and it’s at the expense of my body. Phooey to these people.

July 2, 2010 at 8:43 am
(11) Shari Solomon says:

what about digital x-rays? do they have any radiation?

July 2, 2010 at 10:33 am
(12) Margaret Heckler says:

This article validates something I recently did in connection with dentist. I put off having x-rays taken by stalling every time they wanted to take x-rays until the day came when they flat out refused to clean my teeth unless I had the x-rays done. The last ones were from my previous dentist and were probably 2 years old. I argued with the dental assistant, then I argued some more with the dentist, but to no avail. I contemplated leaving and pulling all of us out but my son was having a cavity filled in the room next to mine and my husband has many dental issues. Long story short, I complied (they had a throat collar at least) but then I wrote a long letter of complaint to the lead dentist explaining I had half my thyroid removed because of a tumor and I really wanted to keep the 1/2 I had left! And as I have always had dental care, no new cavities since age 14 and no dental treatment other than cleanings for the last 40 years, felt that I was not at high risk for dental problems but that I was at high risk for thyroid cancer! I even quoted material from the American Dental Association and the Federal Department of Health -”The Selection of Patients For Dental Radiographic Examination revised 2004 by the ADA and the US Department of Health and Human Services, which state on page 1 “Radiographs should be taken only when there is an expectation by dentists that the diagnostic yield will affect patient care.” Furthermore, the above guidelines place a professional responsibility onto dentists to “minimize the total diagnostic radiation burden (to patients)…” The guidelines state on page 14 “Adult dentate patients, who receive regularly scheduled professional care and are free of signs and symptoms of oral disease, are at a low risk for dental caries….the Panel recommends that a radiographic examination consisting of posterior bitewings be performed at intervals of 24 to 36 months.” So even their own organization states that 36 month intervals are fine for patients in good oral health. Along with the letter I sent a Waiver of Liability, signed and notarized and wrote that if that was not acceptable to them I would find another dentist for me and my family (they have made close to $5,000 from us this year alone!). The dentist response in effect was that my worries were without merit (low dose of radiation, thyroid collars, blah, blah, blaht BUT they would accept my waiver until such time as symptoms of dental decease indicate I need x-rays. So, I win for me at least for now.

I guess if you show up with a legal document and threaten to take your business elsewhere you might get them to agree. Back up position for me was to quit that practice and just bounce from practice to practice for as long as I could get away with it.

Good luck everyone!

July 2, 2010 at 10:39 am
(13) Michelle says:

FYI, digital xrays still use ionizing radiation. The dose is slightly lower and the image quality is slightly better, but radiation exposure is still present.

July 2, 2010 at 11:01 am
(14) FL operasinger says:

What about routine chest x-rays? They are awfully close to the thyroid, too!

July 2, 2010 at 1:20 pm
(15) Lucy says:

Digital xrays do still give off radiation but at a much lower dose than traditional xrays

July 2, 2010 at 3:36 pm
(16) Karen Rutan says:

X-rays are still x-rays. They are just captured digitally. One should always ask for a tyroid collar for any type of exposure.

July 2, 2010 at 10:21 pm
(17) Tina says:

I totally understand the desire not to want too many xrays, but I’m sure that many of you that complain that the dentist makes sooo much money off of you would be very quick to sue or send a notice to the dental board if you had a problem and lost a tooth due to :o ur” neglect. I am a dental assistant and yes I have a Hishimotos(sp?). Is it due to all the exposure, maybe, but the thought of tooth loss due to being scared of minimal radiation scares me more.
@ Betty, your dentist did not randomly come up with the idea of having a full series of xrays every 5 years. It is the standard of care. I can’t tell you how many times we have discovered a chronic abcess in that series of xray. The ones taken on an annual basis checks for decay between the teeth and do not check the end of the roots. Not only have we discovered chronic abcesses, we have discovered cysts ( which have been cyst, not cancer) and other abnormalities. It’s not to just grab money out of your hands!!!! I know it’s hard to believe, but dental supplies are VERY expensive and it cost a lot of money to run a dental practice! Just some of our impression materials run several hundred dollars for two tubes. And those expensive xrays cost over $100 for a box of 80 films(depending on brand and type of film). Don’t forget about staff. I hate to admit it but I’m expensive too!! Taxes, heathcare(thank goodness), workmans comp,and let’s not forget my regular hourly wage. Training and experience isn’t cheap!! If your dentist is willing to train someone off the street and not hire someone with training you have more to worry about than you radation level!! In the state of Oregon your local hairdresser has to have more training than I do. Scary isn’t it!!!

July 2, 2010 at 11:00 pm
(18) Carrie says:

Thank you Tina. Every once in a while there is something on tv or in the news to make everyone panic. Decreasing overall exposure is, of course, very important. Using a thyroid collar is pretty standard and you should be very worried if they don’t have it (the exception being a panoramic xray). You get more eposure flying in an airplane than you get from a full mouth set of xrays (18). Truth is….your Dentist cannot see under you tissue, between you teeth or into your bone. If they miss a diagnoses because of not taking xrays…they are at risk of losing their license and their livlihood. Technology is getting better and their is less exposure than ever before….but there is still a little exposure even with digital My whole family is hypothyroid…..my Dad didn’t go to the Dentist until he was in boot camp…..my Mom only went when her teeth were so bad that they all had to be pulled. I don’t think my whole family became hypo from going to the Dentist. They need LOTS more study and more FACTS before people go making these claims! By the way….I’m a Dental Assistant….and my amalgam fillings haven’t given me Alzheimers either!

October 1, 2010 at 10:55 am
(19) Tom says:

Hilarious–your amalgam fillings have not given you Alzheimer’s. I guess that means they’re completely benign? Actually no, it doesn’t. Amalgam fillings wear down over time. Where does all that mercury go? Not a tough question.

It’s an old and very lame defense of something to mention an extreme case and point out that the extreme case hasn’t happened. You could play Russian Roulette and not blow your head off, but that doesn’t mean it’s a recommended activity.

July 5, 2010 at 6:37 am
(20) Ciara says:

I have to say I agree with Carrie’s straighforward good sense on this. I am puzzled tho by the advice to “ask for a neck collar”. ProvisioN of a neck collar is MANDATOARY for dental x-rays in any EU country I can think of and has been manadatory here for at least 30 years and probably longer and if I actually ask for a neck collar I would out the door faster tha n you could say negligence because anyt dentist who had to asked should not be practising.

July 5, 2010 at 9:34 am
(21) deb says:

I am a thyroid cancer survivor and have always suspected that my exposure to multiple dental xrays in childhood was the cause. FINALLY, the proof is here.

July 5, 2010 at 10:13 am
(22) beth mckinney, rdh, ms says:

thyroid collars have been standard of care in dentistry for many years and should be routinely used on everyone everytime. a single dental x-ray gives a radiation dose of 0.0001 rads. a chest x-ray about 0.003. a mammogram about 0.1-0.2. digital x-rays require smaller doses but it is still the same type of ionizing radiation. a fatal dose is about 600 rads. hiroshima was at least twice that. radiation doses are cumulative over a lifetime. routine x-rays of any type, including mammograms, are being called into question by many. the choice is the individuals and everyone has the right to refuse treatment.

July 5, 2010 at 1:09 pm
(23) Marina, RDH, BS says:

Patient has a right to refuse treatment but also needs to understand that you can’t tie up the professional’s hands when it comes to repeatedly refusing x-rays. At some point, a set of films are indicated to check for decay inbetweeen teeth, to check on bone levels around teeth, and any pathology. A stand-off isn’t going to be of benefit to patient or dentist. I would stay away from offices that aren’t using thyroid collars (what else might they not be current on?). I would also question practices where x-rays are routinely and automatically taken without seeing the dentist first (even if visit is brief check). I would want some discussion based on individual needs and if is there a previous set which can be used. As a hygienist treating a patient with even moderate periodontal disease, a set of x-rays is invaluable. I think it’s important as a patient to be part of the decision making process but you also don’t want to be dictating your own care. Just like it’s important to find a doctor who will listen to your ideas about your thyroid issues and medication, it is important to find a dentist where the relationship is respectful of your concerns as well as any liability and legal issues the professional might have with having you in his/her care.

July 8, 2010 at 10:44 pm
(24) Sarah says:

Thank you so much for this information. My daughter has required multiple dental x-rays due to a congenital problem that is being corrected and there is already a history of thyroid disease in my family. It scares me for her to have had to go through this (and I would make the dentists, oral surgeon, and ortho get x-rays from each other if they were within a few weeks) and this dramatic increased risk for her.

July 9, 2010 at 3:44 pm
(25) Tammy says:

Digital xray is new technology. I had thyroid cancer, and I had lots of dental xrays as a child. No digital available. So does this mean I get to do a lawsuit against my dentist for not offering me the thyroid sheild?

September 28, 2010 at 7:24 am
(26) Kasey says:

Actually, I am a dental assistant, I dont know who gave you the idea that digital xrays have no radiation??!, its just about the same maybe a little less. You cannot take xrays that dont involve radiation, it doesnt exist!

November 23, 2010 at 9:40 pm
(27) Jimbo says:

Just passing through and felt compelled to comment. Absolutely should only take x-rays when indicated. Legally, patient cannot permit dentist to deviate from the standard of care i.e. you cannot give permission to be mistreated. A lawyer would be all over that if a serious condition was missed because of no radiographs. I’m a practicing DDS and have some patients who refuse radiographs when I believe they’re needed. I’m not dogmatic about it but I could have a liability problem by being sensitive to my patients’ legitimate feelings. About the greedy dentists comments: patients who don’t follow my advice often require more extensive treatment later on. The appropriate use of diagnostic radiographs often saves the patient alot of grief and money. Oh yeah- digital reduces but does not completely eliminate ionizing radiation. (My office has been digital for about 11 years.) Find a DDS you trust and follow his/her advice.

March 15, 2011 at 7:51 pm
(28) LaLady says:

I had routine dental x-rays off an on since the ’70′s, but nothing worrisome. In 2000, however, I went to a new dentist for a routine checkup. The assistants decided to give me a full set of x-rays because it had been a few years since I’d had any, and they had no records for me. They kept x-raying and x-raying me, saying they couldn’t quite get the right view, etc. I’m sure they must have taken 10 to 15 views at least. I was sitting there very worried about all of the radiation, but I am a very non-confrontational person, so I did not speak up, and I figured they knew what they were doing. They put a vest on me, but I don’t think it was pulled up very high. There was no collar. At that time, I didn’t know where the thyroid was or that radiation was dangerous for it. The dentist was a trusted friend I had met within the three previous years.

Long story shorter, in late 2007 I discovered a large nodule on my thyroid. You could see it through my skin. It turned out to be thyroid cancer, which was treated with surgery and radioactive iodine. My thyroid was completely removed, and I must take a thyroid hormone replacement pill every day for the rest of my life. Thanks to God, I am still apparently cancer free these three years later. However, I will always believe that it was that dental session which caused my cancer.

March 17, 2011 at 4:45 pm
(29) Vernon says:

Digital xrays use radiation too.

March 25, 2011 at 5:14 pm
(30) Jaz says:

Isn’t it funny that you are afraid of dental xrays because of radiation, and yet to cure your thyroid cancer you took radioactive iodine ?!???!!!

December 21, 2011 at 4:34 pm
(31) Anissa says:

My 15 year-old daughter was recently diagnosed with thyroid cancer. She had no symptoms but had a large lymph node on her neck. We saw a pediatric oncologist a year ago who told us she didn’t have cancer after her pediatrician did every blood test known and a CT. The pediatric oncologist also did more testing and sent us on our way with a bill of health. Since the lymph node still didn’t go away after a year, our allergist told us to see her ENT doctor who we convinced to do a biopsy and found metistatic papillary thyroid carcinoma. This all started after she got braces and the several x-rays that went along with it! I really wish there were more laws to protect our children and make it a requirement to cover their thyroids when getting dental xrays!

February 3, 2012 at 12:07 pm
(32) Shaleen says:

Re: Jaz’s comment to LaLady

I am not “afraid” of cheesecake, I just don’t overdo it for obvious weight gain and health reasons. Same with radiation. Use it lightly and when really necessary. Routine cleaning of teeth is not a time when x-rays are always necessary.

I don’t think people refusing dental x-rays are fearful. Most are just being cautious. We now live much longer and exposure will accumulate for many more years than in the past.

April 29, 2012 at 7:00 pm
(33) motto says:

Melanie and the others re dentists insisting on x-rays:

1. YOU are the patient. YOU must give your consent to EVERY procedure that is done. Tell the Dentist you DO NOT consent to routine x-rays.

2. If the Dentist insists you have too for alleged “liability” reasons you have an option: 1) ask to sign a release and waiver; 2) find another dentist.

My dentist has stopped asking me.

June 5, 2012 at 11:58 am
(34) Willa says:

My dentist uses digital exrays, says the radiation is very minor but still there. My dentist also insists on the lead apron plus the thyroid cover. Years ago there was no thyroid cover and I had a lot of x-rays! I have Hashi.

June 6, 2012 at 1:37 am
(35) Jim says:

I too had extensive xrays (at a time when they didn’t widely claim that xrays are cumulatively bad news) for the preparatory orthodontist’s convenience–55 years ago…I believe that the same xradiation caused my Brain-draining pathway to close up (Aqueductal stenosis)–therefore I got hydrocephalus which developed slowly over the years (water-on-the-brain). The experts tell me that they don’t know why/how I got the hydrocephalus–they say therefore it is congenital. I say balderdash!

unless there is a lawyer who stands to make 40% in a malpractice suit, my statute of limitations was up long ago. Because experts disagree as to the cause, I “couldn’t win a suit anyhow.”…but, malpractice aside,
routine xrays are cumulative–I’ve had a lot of radiation for CT scans to examine my head. Woe is me, but it would be nice to find a heads up dentist who doesnt need more damned xrays of my head.

August 18, 2012 at 10:31 am
(36) ami says:

“ProvisioN of a neck collar is MANDATOARY for dental x-rays in any EU country” – Woah… really?! I was not given one… in fact, my dentist shoved the xray card in my mouth and had left the room before I was totally aware that he was taking an xray! I thought at first he was just taking an impression of my teeth…

August 22, 2012 at 12:05 pm
(37) Sandy says:

Just curious, Are all those who are concerned about radiation exposure living without cell phones too?

“According to Kjell Hansson Mild, who led the study, heavy users of mobile phones have a 240 percent increased risk of developing a malignant tumor on the side of the head where they press the phone to their ear. ”

I’ll take my chances on avoiding and extraction or root canal on a tooth, that had the problem been detected early, could have been completly avoided.

December 15, 2012 at 4:44 pm
(38) bop11 says:

Unfortunately most dental insurance require Xrays as proof that the billed procedure was performed.

December 17, 2012 at 7:20 am
(39) Simon Evans says:

In the UK dental x-rays must be clinically justified as giving net benefit to the patient. It is also strongly discouraged to use lead protection as lead aprons can get in the way of panoramic x-rays. Modern dental x-ray sets are well collimated and shielded so that unless the thyroid is in the direct main x-ray beam, the dose to it will be minimal. Lead protection, including thyroid collars will have no effect on the dose to the thyroid as the dose it receives is from internal scatter. The only view that will directly irradiate the tyroid gland is known as the vertex occlusal view that the dentists I work for say is never used in the UK – even in this view, most of the thyroid dose would come through internal irradiation. It also says on here to ask for a thyroid collar when having neck x-rays – you cannot use lead protection in the area being x-rayed as it will get in the way! Apart from gonad shields being used in x-rays where they will not get in the way, lead protection is of little use generally for the patient in radiography.

Apparently the studies of thyroid cancer rates relied on patient’s recollections of numbers of radiographs, which is going to be unreliable. My advice would be to ask what the clinical justification of the exposure is rather than refusing outright – there should be a net clinical benefit to you the patient!

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