Safety is a difficult thing to define. Safe from what? From cancer? From a brain abscess brought on by a bacterial infection that began as cavities? From pain? From anxiety? From stress? I’ll argue that the question we need to be asking is whether the risk of a procedure (x-rays) outweighs the diagnostic benefit (identifying cavities early and getting a full picture of the state of a child’s oral health).
X-rays are prescribed according to the ALARA principle, which states that radiographic exposure should be kept to “as low as reasonably achievable.” This means that x-rays are ordered by the dentist based on an individualized assessment and according to that child’s particular cavity risk. Additional precautions are also taken for children to reduce their exposure to ionizing radiation, such as the use of lead aprons and/or shields and via dose reduction at the machine.
For most children, the initial radiographic assessment includes front-teeth and back-teeth x-rays, and then their yearly recall assessment includes back-teeth x-rays only unless a specific problem is noted that requires further investigation.
Why are x-rays important?
X-rays allow the dentist to examine areas that are otherwise not visible clinically, namely between the teeth, where cavities can often hide. Many a patient in my practice has been considered cavity-free up until age four or five when we are able to capture their first x-rays. What we sometimes find lurking between the teeth is the start of cavities between all the back molars (often as many as 8 cavities, one for each molar).
Without x-rays, these small cavities may not be recognized at a time when less invasive management techniques (like home hygiene improvement, dietary changes, and fluoride varnish or silver diamine fluoride treatments) can be utilized. Once the cavities are large enough to break through the surface enamel and be clinically visible, more aggressive treatment measures are often necessary (like fillings or crowns). X-rays allow us to identify trouble areas early and adjust home practices and dentist management techniques to prevent the further spread of the infection.
How much radiation do children receive from dental x-rays?
Two bitewing x-rays (the typical x-rays taken yearly at dental checkups) yield about 0.005 mSv (or 5 microsieverts) of radiation. This is the same level of radiation you’re exposed to from sunlight on any given day. The average person’s daily exposure to background radiation comes out to 4-8 microsieverts per day. This means that dental x-rays aren’t contributing greatly to our overall ionizing radiation load.
I’ll close with one last interesting factoid. The amount of radiation from two bitewing x-rays (5 microsieverts) is equivalent to the amount of radiation received by eating 50 bananas (the dose of ionizing radiation from a banana is 0.1 microsieverts – silly potassium – see the hilarious SciBabe article below for more info). I don’t know about your kids, but mine go through fifty bananas in a month. This isn’t to say we shouldn’t be eating bananas, but to show that ionizing radiation is everywhere, even in our snacks. We should be judicious about ordering x-rays, but we shouldn’t avoid them simply because of the ionizing radiation because the dose is small and they provide crucial information that contributes to a thorough dental examination, which is the whole reason you’re bringing your child to the dentist, right?
Links
The 2021 AAPD guidelines for prescribing radiographs: https://www.aapd.org/globalassets/media/policies_guidelines/bp_radiographs.pdf
CDC and ALARA: https://www.cdc.gov/nceh/radiation/alara.html
An excellent open-source graphic on ionizing radiation sources from xkcd: https://xkcd.com/radiation/
The SciBabe on radioactive bananas: https://scibabe.com/daily-mos-the-mildly-radioactive-banana/
Another great blog post from a fellow dentist, Dr. Francis McCarthy, on x-ray radiation: https://www.francismccarthydmd.com/patient-information/blog/2017/1/20/radiation-risks-the-truth-about-dental-x-rays/
