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Do you need to be concerned about dental x-rays?

March 14, 2023

On the one hand, yes. You should always know what's going on and understand the risks and benefits of the choices you make, especially when it comes to your kids. On the other hand, it may be a topic your dentist has not described to you in depth because, for dental x-rays especially, the benefits can be substantial and the risks are considered nominal.

We all know radiation is bad… except, of course, when it's not, e.g. treating cancers, hyperthyroidism, etc. We use it in medical and dental most commonly for diagnostics so we can x-ray vision our way into figuring out what (if anything) is going on, the sooner the better, so we can manage small problems instead of letting them get out of hand. Cavities are the most commonly observed disease, but by no means the only thing for which we're screening. 

But even if it's not all bad, what harm can it cause? We're talking about ionizing radiation. The average person, from all sources (1/3 of which is from radon gas in the ground) experiences 6.2 millisieverts (mSv) of radiation per year. This is chronic daily low-level exposure, which your body has time to account for and repair damage from. At 5 microsieverts (μSv) for 4 dental x-rays, you'd need to get over 5000 individual dental x-rays to equal the annual dosage you already get. Basically, just walking around during the course of the average day is like getting 13.5 dental x-rays. The goal in medicine and in dentistry is to abide by the principle of ALARA - as low as reasonably achievable, i.e. get the information you need to diagnose and treat while being as conservative as possible. As per the pediatric radiology and imaging campaign is titled, we want to "Image Gently". In pediatrics, I usually take 2-4 x-rays a year. While this all translates to numbers that are non-zero, which means a health risk which is non-zero, it is, as I stated, entirely nominal at these dosages and frequencies and the body is capable of repair and healing. If your dentist tells you they want you to come in tomorrow to take 5000 x-rays, then we should all have a discussion.

Here are a few more interesting comparisons. We've been talking about electromagnetic radiation, i.e. light energy (from radio waves to visible light, x-rays, and finally gamma rays). In nuclear radiation, unstable elements or isotopes decay by breaking down (emission of alpha and beta particles) and by emitting pent up energy in the form of gamma rays (the highest on the electromagnetic spectrum). What's interesting is that there are many stable and unstable isotopes we encounter. Brazil nuts contain radium from the earth in which they grow (Ra-226 & Ra-228), the consumption of each nut therefore results in an exposure to about 0.22 μSv, AKA 5 Brazil nuts to 1 dental XR. Bananas also contain Potassium (normally K-39). Bananas, however, also contain a small amount of the radioactive isotope K-40. Eating 1 banana therefore results in an exposure of 0.1 μSv of radiation to the body, AKA 12.5 bananas to 1 dental XR. Cosmic Radiation (from stars including our sun) is experienced during a standard airplane flight from east coast to west coast would result in 35 μSv of radiation (same as 28 dental xrays).

These chronic low-level doses are NOT cumulative. Our bodies heal from electromagnetic energy damage all the time (e.g. UV light AKA sunburns). The Banana Equivalent Dose (BED) is an actual unit of measure one can use instead of Sieverts (Sv, what we've been using here), Greys, Rads, etc. The BED is used most often to inform the public about relative radiation risks when discussing what are truly infinitesimal doses. A dental x-ray is basically 12 BEDs (12 bananas). A series of 4 bitewing dental x-rays is 50 BEDs (50 bananas). Medical imaging, which people seem to be less weary of, includes a chest X-ray of 100 μSv (80 dental x-rays or 1000 bananas) and an abdominal CT scan of 10,000 μSv (8,000 dental x-rays or 100,000 bananas).

While commonly used for smaller, more routine purposes such as checking for cavities, x-rays are imperative in accurately diagnosing a problem, assessing for root fractures and abscesses, diagnosing bone pathology, checking for cancerous growths, determining salivary gland and joint issues, etc, and can therefore be life-changing. As is best practice, I will always “image gently,” only as needed for expected diagnostic gain, with dosages as low as reasonably achievable (ALARA). While one does not pursue radiation above that which is absolutely necessary, that which is added by dentistry for the benefit of your kiddo’s health is considered safe and well worth it. 

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