The radiation you would receive from a traditional film dental x-ray is very low. Today, with non-film digital x-rays available, the radiation is reduced by an additional 90%.
Comparatively, a traditional chest CT-scan exposes a patient to 2,800 times the radiation as a digital dental x-ray, and a mammogram gives off around 60 times as much radiation. Surprisingly, you can get the same amount of radiation as one of our dental x-rays from eating about 50 bananas.
References:
BBC NEWS Magazine 13 October 2011 “Go Figure: What Bananas Tell Us About Radiation” By Michael Blastland.
Every Day Health: “The Truth About Everyday Radiation.” By Sharon Tanenbaum, Medically reviewed by Ed Zimney, MD. 3/18/2011.