Answer to Question #11136 Submitted to "Ask the Experts"

I just switched to a new dentist for my kids and like the office very much, but I think they/we are getting exposed to other people's radiation from x rays due to the office layout.

There are several dental chairs in one room side by side. Each chair has its own x-ray machine. There is nothing (no walls, etc.) separating the x-ray machines from each other. There are no enclosed rooms. It's more like an open-air office with dental chairs and x-ray machines. They also use digital x rays. So when my kids are sitting in the chair other kids RIGHT NEXT TO THEM are getting x rays all the time! Also, the dentist asked me to come in from the waiting room so I could talk to her. We stood in the hallway just a few feet from the x-ray machines going off over and over. This didn't bother the dentist, she was oblivious to it, but I was terrified because I was so close to the x rays taking place. Is this safe? Are my kids safe?

First of all, a little background—every state has a state radiologic control program, or a state agency with a similar name that is responsible for enforcing state regulations concerning radiation emitting devices; and, dental offices are definitely included in this category since dentists own and operate about half of all x-ray machines in use today. The facility layout and its safety would be a part of the inspection. (Editor's Note: in Pennsylvania, the Bureau of Radiation Protection inspects dental facilities every two years.)

This might answer the legality of the question; but, just how safe is an 'open bay' office? Here are a few things to think about. One is that over the last 80 to 90 years, x-ray receptors have become faster and faster, such that today's digital receptors need only 1 percent of the radiation that the early dental receptors from the 1920s needed; so, we definitely use only very low doses of radiation in dentistry. Another reason is the physics of what happens to the x rays once they leave the x-ray machine and reach the patient. Over one-fourth of the x-ray photons are absorbed by the patient and almost two-thirds of the x-ray photons are scattered. This leaves about 10 percent of the x-ray photons to pass through the patient to reach the x-ray receptor. The potential danger to the person making the x-ray exposure or to an innocent bystander is from these scattered x rays since these can be scattered at any angle. The energy from these x rays are partially absorbed by the patient so, when they exit the patient, they are not nearly as energetic as when they entered. As a matter of fact, at a distance of 1 meter from the patient, the average scattered x-ray photon has lost about 99.9 percent of its original intensity. For a safety factor, this 1 meter distance is doubled to 2 meters by most safety experts as the minimum safe distance to stand away from an activated dental x-ray tube head without an intervening barrier.

The most important radiation safety guidelines to consider would be to use thyroid collars and lead aprons for children receiving dental x rays, and to keep unprotected children and adults a minimum of 2 meters away from the x-ray tube head during exposures. Assuming that the overall plan has been approved by the state, the facility should be considered to have a safe design.

Jeffery B. Price, DDS, MS
Clinical Associate Professor and Director of Oral and Maxillofacial Radiology