Archive for January, 2012

Dr. Oz and Thyroid Cancer fears from Dental X-rays

Dr. Dave —
 I just received the following message about x-rays and thyroid cancer.  Also, consider THIS.  Would you have anything more to contribute to the confusion?
   — Z

Ladies, listen up!!

Thyroid cancer
On  Wednesday, Dr. Oz had a show on the fastest growing cancer in women,
thyroid cancer. It was a very interesting program and  he mentioned  that
the increase could possibly be related to the use of dental x-rays and
mammograms. He demonstrated that on the apron  the dentist puts on you for
your dental x-rays there is a little flap that can be lifted up and wrapped
around  your neck. Many dentists don’t bother to use it. Also, there is
something called a “thyroid guard” for use during mammograms.
   By  coincidence, I had my yearly mammogram yesterday. I felt a little
silly, but I asked about the guard and sure enough, the technician had one
in a drawer. I asked why it wasn’t routinely used. Answer: “I don’t know.
You  have to ask for it.” Well, if I hadn’t seen the show,  how would I have
known to ask?
   We  need to pass this on to our daughters, nieces, mothers  and all our
female friends and husbands tell your  wives !! I just did, now you send
it on to your list.
Someone was nice  enough to forward this to me. I hope you pass  this  on
to your friends and family.

Thank you for your question.  Yes we do  have the lead aprons with thyroid collars.  It is most likely not necessary but we have them anyway.  To debunk the myth propagated by Dr. Oz, I’ll explain further:

Firstly, there are 2 types of dental radiograph mediums; film and digital.  It was once true that digital radiographs used less radiation or energy than radiographs by film.  But lately, there have been huge advancements in the quality and speed of the film.  Just like film for cameras; the higher “speed” the film, the less exposure you need to capture an image.  Dental “X-ray” units have exposure adjustments on them.  You adjust the amount of radiation, by adjusting the interval of time that the unit is emitting the energy.  Low quality, low speed, films need more exposure time; hence more energy.  In fact, there is a digital mode on the units.  If you flip the switch, the exposure times are a fraction of the times for film.  However, the film is so fast and of such quality these days, we are using the lower settings in DIGITAL mode.   Also, the image captured with film is higher detail that the digital medium allows.

Now with all this said; the higher speed films are MUCH more expensive for the dentist then the lower speed film.  Here, we only buy the highest quality film available.  Every time there is an upgrade we change and spare no expense for the safety and well being of our patients and staff.  Unfortunately, not all dentist do.  In my tenure, the film has advanced several times.

Dr. Oz’s second concern is radiation scatter.  Does the energy significantly scatter beyond the target?   The answer is NO.  Besides the advancements in film, the dental units have been improving too.  Scatter used to be more of a problem on the earlier units but the newer lead lined collimators do not allow for that any more.  The collimator on a dental unit is that tube that the dental technician aims at the tooth.  These direct the energy specifically at the tooth and not the surrounding tissues.  This is wonderful for the safety of the patient, but can be a headache for the the dental technician because it causes a familiar problem we call “Cone Cutting”.  If the collimator is not aimed directly at the film….if we are off just a little bit,  we get an area of zero exposure.  The outline in the developed film is EVEN THE SAME SHAPE AND SIZE of the collimator head!!!!!  That proves there is almost zero scatter.

So like a lot of things on TV, a little bit of truth and knowledge mixed with self serving promotion can be dangerous.  To be at any significant risk of exposure, the practice would have to use very dated materials and equipment.  Someone almost had to cherry pick  facts to end up with the misleading conclusions that were stated in the television show as described.  In doing so, he has put unnecessary fear into millions of people.


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