Answer to Question #4411 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues — Dental

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


Recently I went to a doctor of dental surgery (DDS) picked randomly from the phone book for a second opinion. He decided that he wanted to take his own x rays. The cylinder on his x-ray machine at one point appeared to be pointing directly at my left eye but I did not say anything. Several days after this multiple x-ray session I developed a "burning" sore throat and a white blotch which appeared to be on the pupil of my left eye. I went to an opthamologist and he said that it was an "opacity" on the lens of my left eye of unknown causes. He thought possibly it was caused by the sun—even though it only appeared in the last two weeks. He was not sure concerning the question of whether or not x rays could be the cause. That is why I decided to pose this question to the experts in the Health Physics Society for no other reason than my own peace of mind. Briefly, if one looked directly into the cylinder of a dental x-ray machine, what could be the possible results?


It is extremely unlikely (make that all but impossible) that either your burning sore throat or lens opacity are related to your recent exposure to dental x ray.

First, your sore throat. It is known that radiation, in large doses, can cause mucositis involving the entire mouth and pharynx. Patients being treated with radiation therapy for cancer of the head and neck region frequently experience this, but only after several high-dose treatments.

The most common cause of lens opacity is a cataract. Once again, radiation in very large doses is known to produce this lesion. However, there is a lengthy latent period, generally months to years, between exposure and appearance of the cataract.

Both of these effects are classed as deterministic, which means that severity of the effect is a function of radiation dose. There are threshold doses. For oropharyngeal mucositis, the threshold dose is of the order of 10 gray (1,000 rad in old units). For a cataract, the threshold is about 1 gray (100 rad). These doses are equivalent to literally hundreds or thousands of ordinary dental diagnostic exposures, and are far greater than any dental x-ray machine can deliver.  Any attempt to produce this much radiation with a dental machine would burn out several x-ray tubes (and perhaps other components) at a cost to the dentist of thousands of dollars in direct cost plus several days or weeks of downtime.

Conclusion:  You should seek other causes for your pharyngitis and lens opacity.

Julian Gibbs, DDS, PhD

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 12 April 2005. 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.