Answer to Question #11299 Submitted to "Ask the Experts"

My 12-year-old daughter has been receiving orthodontic care for the past two years and eight months. During that time she received one cephalometric x ray and seven panoramic x rays to watch an impacted canine. The panoramic x rays have been spaced about six months apart. I am very concerned about the radiation exposure to her. I have expressed this to the orthodontist, and he assures me that the radiation exposure is low. Can you please tell me if the radiation exposure is too much?

Panoramic and cephalometric radiographs require the least amount of radiation of any x-ray examinations used in dentistry. A common way of expressing the amount of radiation used for these examinations is by comparing them to the number of days of normal background radiation that gives the same degree of exposure. Background radiation is around us all the time and includes things like cosmic radiation from outer space; small amounts of naturally occurring radioactive materials in soils, building materials, food, etc.; and radon, a naturally occurring radioactive gas. The amount of background radiation that people are exposed to varies, primarily with altitude. Those living at higher altitudes receive more cosmic radiation than those living at sea level. Studies have not found any differences in cancer rates or other adverse effects in people living in areas with higher background radiation compared with those in other areas.

That said, the amount of radiation for a cephalometric radiograph (the profile view of the head used to evaluate how the jaws relate to each other and to the rest of the skull) is equivalent to less than one day of average background radiation. Panoramic radiographs (used to evaluate the condition and position of teeth) have an exposure equivalent to one to three days of background radiation, depending on the specific machine. In comparison, a single commercial airplane flight from New York to California exposes passengers to the equivalent of three to five days of background radiation due to the extra cosmic radiation at high altitudes. So the amount of radiation that your daughter has been exposed to during her orthodontic treatment is about the same as she would get in a couple of cross-country plane trips. That's very little.

The real answer about whether the radiation exposure your daughter has received is too much is related to the need for the information provided by the x rays. When a child has an impacted tooth (one that is blocked from erupting normally), such as the impacted canine in your daughter's case, the orthodontist has to make a decision about how to handle the situation. Sometimes the orthodontic treatment will move the surrounding teeth enough so that the impacted tooth will be able to erupt into its normal position without help. In other cases the orthodontist will have to put an attachment on the impacted tooth so it can be pulled gently into place. It sounds like in your daughter's case the orthodontist is monitoring the position and movement of the impacted tooth, which can only be done with x rays. You might want to discuss with him his plans for either continued monitoring of the impacted tooth or helping it erupt by adding some traction on it.

Sharon L. Brooks, DDS, MS

Reference
White SC, Pharoah MJ. Oral radiology principles and interpretation. 7^th ed. St. Louis, MO: Elsevier/Mosby; 2014.