What should you do the next time the dentist tells you he or she is going to take full dental X-rays? A new study shows that just as porcupines make love very, very carefully you should also take care to limit the amount of radiation exposure during your lifetime, particularly the amount your children receive.

Dr. Elizabeth Claus of Yale University reports in the American Cancer Society Journal Cancer, that there’s a link between dental x-rays and the risk of developing a brain tumour called a meningioma.

These tumours grow from the meninges, the layers of tissue that cover the brain. Fortunately, most meningiomas are benign. Others are slow growing, but they can become life-threatening when they become as large as a baseball, compressing brain tissue. Meningiomas account for 34% of all primary brain tumours, can occur at any age, and are twice as common among women as in men.

Formerly it was believed that the main cause of meningiomas was ionizing radiation due to atomic bombs or radiation received during cancer treatment. Now, Dr. Claus says the main risk is dental x-rays.

Dr. Claus and her colleagues studied 1,433 Americans who had meningiomas with 1,350 others who did not have this tumour, but who were of the same age profile, sex ratio and geographical area. The researchers then analyzed the dental and medical history of both groups.

For instance, they were questioned whether their dentist had ordered standard X-rays, known as bite-wings, every year, never, or now and then. Finally they were asked if they had ever had braces which involve full mouth X-rays.

Dr. Claus concluded that those who reported having full mouth X-rays before 10 years of age were 4.9 times more likely to develop a meningioma. Those who had full mouth X-rays later than 10 years of age were three times more prone to this tumour. This should flash a red light for parents.

So how can you avoid needless dental radiation? According to Dr Claus all children who get braces today also get full mouth X-rays. None of my children had braces, but most of my grandchildren have had them. The question is how many of them really needed braces and has this practice become a fashionable trend? Is the risk worthwhile if only for cosmetic reasons?

Never accept this rationale if a dental technician says, “Don’t worry. You get more radiation exposure from a day in the sun or flying to the Caribbean.” I agree that today dental X-rays expose patients to less radiation than in the past. But little bits of radiation mount up, particularly when one totals the exposure received from other X-ray tests. Radiation isn’t like an infection that’s cured by antibiotics. Rather, radiation is cumulative and, like elephants, our bodies never forget the amount received during a lifetime.

I’ve always worried about needless radiation and many years ago one of my columns made headline news. I discovered that some patients were receiving huge amounts of radiation from dental and other X-rays. For instance, some X-ray equipment had not been serviced for 15 years! This sparked a major investigation by the government.

Dental X-rays are, of course, required for legitimate reasons. But like anything they can be overdone. So always ask if the X-ray is really needed. No one really knows how much radiation we can receive before it causes trouble.

Ideally we should all have radiation cards that show how much radiation we’ve accumulated. Particularly since one of the major tests today is the CT scan that delivers large amounts of radiation. But hell will freeze over before such cards are in general usage.

So what should parents do? I’d agree that markedly crooked teeth deserve to have braces as the radiation dose does not compare with a CT scan. But for lesser imperfections it may be prudent for parents to ask, “Should I subject my child to potential risk of radiation and a meningioma, and how important is it for my child to have the perfect smile?”

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