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Dental X-ray, cancer link assessed.

Dental X-ray, cancer link assessed

A new study shows for the first time an increased incidence of salivary gland cancer in people exposed to very high levels of dental X-rays, such as those commonly used through the 1950s. While finding no such relationship for exposure to the smaller doses used today, the researchers observed a dose-dependent trend, which they say affirms the importance of minimizing exposure to dental X-rays. Many dentists repeatedly expose their patients to unwarranted risk by not taking advantage of new, low-dose technology, they assert.

The study focused on tumors of the parotid gland, a major salivary gland located in the cheek and directly in the path of many dental X-rays. Susan Preston-Martin of the University of Southern California School of Medicine in Los Angeles and her colleagues interviewed 408 patients with parotid tumors and an equal number of matched controls. They compared the two groups' exposure to dental X-rays and other types of cranial radiography. After correcting for other risk factors, they found an X-ray-related increase in malignant parotid tumors, they report in the Aug. 17 JOURNAL OF THE NATIONAL CANCER INSTITUTE.

"The paper really is a testimonial to the safety to modern diagnostic X-ray procedures," says Charles Schoenfeld of the American Dental Association in Chicago, noting that X-ray doses today are about one-five-hundredth the minimum average dose the study associates with an increased risk of cancer.

However, says study coauthor Stuart C. White of the University of California at Los Angeles School of Dentistry, the dose-related findings leave open the posibility that even low doses could carry some risk over longer periods of time. He estimates that fewer than half of the dentists in the United States have switched to "E speed" X-ray film. Available since 1981, the high-speed film requires half the X-ray dose of the most commonly used film. Similarly, most dentists do not use rectangularly columnated X-ray beams, which can cut X-ray doses by another 50 percent, White says.
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Author:Weiss, Rick
Publication:Science News
Date:Aug 27, 1988
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