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

Category: Medical and Dental Patient Issues — Dental

The following question was answered by an expert in the appropriate field:

Q

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?

A

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

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 7 January 2015. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.