Some people do not want diagnostic x-rays because they have heard that the radiation is dangerous. In fact, they pose very little danger. There are currently two methods of measuring exposure to radiation.
The first and oldest unit of measure is called a rem. A rem is a large unit, so exposure to medical radiation is generally measured in millirems (mrem). (It takes a thousand millirems to make a rem.) Dental x-rays on the slowest speed film deliver about 4 mrem. (Most offices now use faster films which reduce radiation by a factor of 2-4, the average dose across the board being about 2 mrem per intraoral film.) Thus, using the slowest speed film, a full mouth series of dental x rays (18 intraoral films) delivers about 72 mrem. A panorex film delivers about 8 mrem. By comparison, according to the National council on radiation protection and measurements, the average person in the US is exposed to about 360 mrem per year just from background sources. By this measure, it would take approximately 5 full series of dental radiographs on the slowest speed film to equal the background radiation that the average citizen is exposed to on a yearly basis. Note that we take a new full series every three to five years on average. Most offices use faster film reducing the dose of radiation per film by about half. Offices using digital radiography reduce the radiation by even more.