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Comment by pessimism | Hacker News Reader

Any people here who go to the dentist?

   Specifically, the American Dental Association's 
   guidelines for heathy persons suggest that
   
   * children receive 1 x-ray every 1-2 years,
   * teens every 1.5-3 years,
   * and adults every 2-3 years.

~ http://www.medicalnewstoday.com/releases/243952.php

I was personally very surprised and alarmed by this.

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The amount of radiation you receive in one dental x-ray is approximately 1/8th the amount you receive in a single cross-country plane flight.

I mean, you still don't want to overdo it. All things being equal, you want to limit your exposure to ionizing radiation across the board. But dental x-rays generally aren't a public health menace, and they're seldom overprescribed to a dangerous degree. I'd much rather get a dental x-ray that prevents costly and dangerous dental disease in the proximate future, given the fairly low dosage involved.

Typical dental x-ray's expose you to drastically less radiation than a CT. Wikipedia:

> The dosage of X-ray radiation received by a dental patient is typically small (around 0.150 mSv for a full mouth series, according to the American Dental Association website), equivalent to a few days' worth of background environmental radiation exposure, or similar to the dose received during a cross-country airplane flight (concentrated into one short burst aimed at a small area)

Before getting alarmed consider doing the math to assign numerical value to level of danger. Wikipedia article on Sievert has the formulas for it, as well as benchmark values to judge the outcome.

If you don't want to do the math, consider this handy chart: http://xkcd.com/radiation/

The standard defense of the safety of x-ray machines seems to be that you get more radiation from long haul flights. Well, there's a strong argument that flying isn't safe either. Pilots and stewards apparently have elevated cancer rates.

Why does a kid who hasn't lost his baby-teeth need dental x-rays?

I suppose I am apparently doing very well at avoiding such x-rays. I have had two such x-rays in the last 20 years.

Why are you alarmed? How significant is a 5x greater risk of meningioma?

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