Are dental x-rays dangerous?
Dental x-rays are one of the lowest radiation dose studies performed. A routine exam which includes 4 bitwings is about 0.005 mSv, which is less than one day of natural background radiation. It is also about the same amount of radiation exposure from a short airplane flight (~1-2 hrs). The American Dental Association recommends that patients who are not having problems have dental x-rays performed every two years. Proper shielding is also common, which makes the potential risk even lower.
The above was taken from X-Ray Risk.com which promotes responsible imaging through education. Click on the link below for a list of FAQs on radiation safety.