Answer to Question #13960 Submitted to "Ask the Experts"

My family and I just moved to a new city and visited a new dentist. He did more imaging than we are accustomed to. In addition to a full set of x rays, a cone-beam computed tomography (CBCT) was performed. We were told the dentist does these x rays for all new patients and continues with annual x rays. Our previous dentist did not have a CBCT machine and, at least for us only did x rays every two to three years. The change concerns me. I prefer to minimize my family's radiation exposure. From what I have read so far on the Health Physics Society site, even with the addition of the CBCT scan and more frequent x rays our radiation exposure is still relatively insignificant. This is news that I can certainly welcome. Am I correct? Is continuing with this dentist okay? What might you do if you and your family were in these circumstances?

The issue you bring up about the number, type, and frequency of dental radiographs (x rays) is an interesting one that has been discussed and debated for a long time. Back in the 1980s I even did a study on this subject as part of my master’s degree program in health physics, running a clinical evaluation of guidelines for taking dental x rays that had been recently published by the American Dental Association (ADA) and the Food and Drug Administration (FDA). About 20 years later I was on a panel called by the ADA and FDA to review the guidelines and revise as appropriate.

The basic idea behind the guidelines (called Selection Criteria) is that radiographic examinations should be tailored to the individual patient’s health condition and needs, not done as a "one size fits all." The only dental x ray exam that the ADA gives a frequency for is the bitewing (BW). This intraoral x ray is made with the patient biting on a paper tab sticking out from the film packet (or digital sensor) and shows both the upper and lower back teeth on one side. A full BW exam is one or two images per side, depending on the number and arrangement of teeth. It is the most useful x ray exam to check for dental decay (caries, cavities) and also shows the level of the bone around the teeth. The recommended frequency for BW exams varies with patient age (kids generally need them more frequently than adults) and risk for dental decay or other conditions, ranging from one to three years. If your previous dentist was taking them every two to three years, he or she was judging you to have good oral health with relatively low risk for disease. That is how often I personally get BW radiographs. My husband has started getting new cavities due to his dry mouth, so he needs BW more frequently.

Regarding CBCT, it is a wonderful imaging technique that provides information in three dimensions (3D), rather than the two dimensions from standard dental x rays. I'm an oral and maxillofacial radiologist who works with CBCT every day, providing imaging reports for dentists who use this technology and would like a specialist to review the scans to make sure that nothing is missed. There are many situations where the 3D information is very helpful, such as in evaluating the amount of bone available for a dental implant, checking on the location of the nerve canal before wisdom tooth extraction, identifying strange anatomy before root canal therapy, locating impacted teeth before orthodontic treatment, and evaluating the jaw joints in patients who are having pain or clicking sounds in their temporomandibular joints (TMJs). It has sometimes been used as a general screening examination, as it sounds like your new dentist is doing, but it is actually less useful in that situation than in situations where there is a specific indication. BW radiographs are still needed with CBCT to evaluate the teeth for decay.

The good news is that the doses from all types of dental x ray examinations are relatively low and your risk for developing any type of adverse effect is also very low. There are also risks from avoiding x rays, primarily from lack of early detection of dental disease, much of which cannot be found clinically until it is advanced.

I do not think you need to leave this dentist if you are satisfied with the care you and your family are receiving. However, when it’s time for another check-up and the dentist wants to take more x rays, it is perfectly appropriate to ask why—why now and what did he see clinically that makes him suspicious that x rays are needed at this time. If he has a reason, other than it has been a year since your last ones, go ahead and get them. If he wants to take them more often that you are comfortable with, ask about your risk factors for dental disease (they can change over time, such as with my husband’s dry mouth that contributes to more frequent decay). You and your dentist should be partners in your oral health care.

Sharon L. Brooks, DDS, MS