Answer to Question #13717 Submitted to "Ask the Experts"

My five-year-old son just went to his first dental appointment. Before seeing my son, the dentist ordered a panoramic x ray. The panoramic machine did not fit him, so the dental technician brought a stool to boost him up to reach the bite area. The technician used the light on his face and pressed the machine button for 20 seconds but no image was shown on the computer screen. The technician repeated the previous step and an image was shown. The image clearly showed half of my son's forehead, two eye sockets, teeth, and jawbone. It seems the x ray scanned my son's whole face.

From this I have a couple of questions: (1) Was my son exposed to two x-ray measurements? (2) Since young children's cells grow and divide rapidly and some tissue and organ absorbed more radiation than the others should I be concerned about any health issues such as cataracts in the future due to eye cells damage or Alzheimer's disease due to the brain cells damage?

You mention several issues and I will address them, but I am pleased to let you know that the amount of radiation that your son received does not put him in a high-risk category for the future.

It seems that your first question may be whether your five-year-old son should have had a panoramic x ray. The guideline that is generally followed in addition to the actual age of the child is the eruption pattern of the permanent first molars and permanent incisors. These teeth are erupting in some five-year-old children while in other children these teeth may not erupt until age six or closer to age seven. So, yes, it is very often fine for a five-year-old to have a panoramic x ray.

Another question is about what features should be exposed in a panoramic view. What you describe seems to be the normal features that a panoramic radiograph captures: The lower portion of the eye sockets, the maxillary sinuses, the upper and lower jaws, and usually the temporomandibular joint (TMJ) (or the joints that open and close the mouth), as well as the cervical spine.

The next issue appears to be the important question though—did your son receive a radiation dose on both exposures? Or to put the question another way, what happened during the first exposure? It is possible that the panoramic machine did make a radiographic exposure that was not received by the controlling computer. It is also possible that there was a "dry run" and the machine actually did not make an exposure. At this point it is difficult to say for sure. I will give some example risk estimates and assume that two exposures were made.

You ask specifically about cataracts and Alzheimer's disease effects, which may be potential effects seen after radiation exposures. Let's look at how much radiation is necessary in order to see these types of radiation effects. The International Commission on Radiological Protection (ICRP) guidelines on x-ray effects and cataracts provide for a safe dose of 500 milliGray (mGy) of absorbed radiation dose before there is a risk for cataracts. The absorbed dose for the eye is approximately 0.09 mGy per dental panoramic x ray, or approximately 0.18 milliGray for two panoramic x rays. This represents 0.036% of what might be considered the allowed level of radiation as recommended by the ICRP guidelines, which means that the risk of your son developing cataracts as the result of these two panoramic exposures is exceedingly small or zero.

As far as the risk of developing Alzheimer’s disease, there is no proven link between radiation exposures and Alzheimer’s disease at this point although studies are ongoing.

In summary, whether your son had one or even two panoramic exposures does not place him in a high-risk category for developing cataracts in the future. As far as Alzheimer’s disease is concerned, there is currently no proven link between radiation exposures and an increased risk of developing the disease. I hope this answer has been helpful.

Jeffery B. Price, DDS, MS