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.