Radiographs (x-rays) have always played a large part of diagnosis and planning within dentistry, and with the advent of cone-beam CT (CBCT) scanners, that role is becoming bigger still.
Briefly, a CBCT is similar to a medical grade CT machine in that it allows 3-dimensional evaluation of bone (as well as other tissues); however, the CBCT can only produce relatively small images, and therefore exposes the patient to significantly less radiation than the medical grade CT. In dentistry, the CBCT is what allows very precise planning of dental implants and implant prosthetics. As dental implants continue to become more common, the number of CBCT scans performed goes up, and so does the radiation risk.
In recent years, the topic of radiation exposure in medical and dental clinics has received more attention. An article in the New England Journal of Medicine in 2007 suggests that 1.5-2% of all cancers in the US may be attributable to radiation from CT scan; however, the author is referring to medical grade CT (Brenner et al). If we look at the average American, 50% of their radiation exposure will come from the environment, 48% comes from medical/dental procedures, and an additional 2% comes from other sources (NCRP Report 2009). Radiation risk becomes more relevant to dentistry when we consider that many of the anatomic structures that are most sensitive to radiation are found in the head and neck.
Every type of dental radiograph exposes a patient to radiation. The most common type of images used in day-to-day dental practice includes the periapical/bitewing, the panoramic (SEE IMAGE), the full-mouth series (which is a collection of 18 periapical/ bitewing images), and the CBCT. Not only does radiation dose vary with the type of image, but it also varies with the brand of x-ray machine used, the technique, and a number of other technical factors. For example, the digital sensors used in modern radiographs are exceptionally sensitive, and allow lower radiation dose than conventional film.
So, how do you minimize radiation dose during dental procedures? The first, and perhaps the best, method is for the dentist to carefully consider the risks and benefits of each image to be taken. At Trailhead Dental, we frequently decide to obtain panoramic and bitewing radiographs as part of our initial examination, but that is a deliberate decision, and certainly not automatic. We attempt to obtain previous radiographs from your other doctors, and try to only take radiographs if there is a specific need, which reduces your radiation dose. If we do need to take radiographs, it is important to use proper protection during the procedure, including the use of a lead apron.
It is also important to address patient concerns about radiograph, and not dismiss it radiation risk as the same as “a day at the beach”. Here is a practical example to help understand radiation dose. One common brand of CBCT machine used in offices around Denver, CO has an effective dose of 70 mSv, which is approximately equivalent to 4 panoramic images or 12 days of exposure to everyday background radiation. A single panoramic image is approximately equivalent to 3 days of background radiation, and full mouth series with digital sensors is approximately equivalent 4 days of background radiation. These are relatively small amounts, but keep in mind that radiation dose is cumulative, and add to your risk of more serious health concerns.
If you have questions about how radiographs are being used in your dental care, and would like to schedule a consultation with Dr. Bryan Limmer, please contact our office at 720-242-6803.