There are a few different factors that affect how much radiation is given off during a dental x-ray. However, with advancements in technology, especially digital systems, x-rays require very low dose radiation. Radiation dosage can be measured in units called millirems (mrem). A typical dental x-raytaken digitally exposes a patient to less than 0.5 mrem.
To put things in perspective, an average resident of the U.S. receives over 360 mrem every year from background sources. This comes from all over the place: outer space, radioactive materials in the earth, small amounts of radioactive material in foods and products that we use, even over people. Variances in lifestyle likewise cause variances in each individual's total exposure. For example: an individual who flies often is exposed to more background radiation than someone who does not.
While steps should be taken to limit x-ray radiation exposure, dental x-rays are very low dose and are crucial for proper diagnosis. Without them, much of the oral cavity cannot be viewed.
Bitewing x-ray showing cavities between the teeth that cannot be seen upon visual inspection of the mouth. Without x-rays, these would not have been detected until they were massive cavities...most likely requiring more intense treatment such as a root canal or extraction.