Biological Effects of Radiation in Dentistry

Dental X-rays (radiographs) help dentists see inside a tooth and beneath the gums to diagnose common problems like cavities, periodontal disease and infections. Without this technology, many diseases would go treated. But X-rays are not without risk as people absorb increasing amounts of radiation from their environment. Researchers at the Sussex Medical School suggest limiting dental X-rays when possible.

X-Ray History

• Dentistry has made great advances in lowering radiation exposure during X-rays. In the 1930s and 1940s, the irradiating X-ray cone that emitted radiation covered most of the head and neck, and the exposure lasted several seconds. Today, the diameter of the cone is less than 3 inches, pointed at a small spot and exposure lasts only tenths of seconds. Faster film speed has also reduced the amount of radiation the patient receives.

Radiation Risks

• X-rays are one form of energy that's absorbed by living organisms. Large amounts of radiation can cause cells to mutate, and have been shown to cause cancer and changes in chromosomes. If the head and neck are exposed, X-rays can increase the risk of cancer of the lens of the eye, thyroid, salivary glands, bone marrow and skin. The lead in the lead apron used in the dentist’s office is used to prevent radiation from reaching the patient's sensitive organs.

Radiation Exposure

• In the normal course of a day, you are exposed to radiation from various sources, such as airline travel, high altitudes, radon gases and home appliances. The roentgen is used to express the measurement of radiation exposure and the amount of energy absorbed by tissue is called a rad, or radiation absorbed dose. Exposure to radiation is cumulative, meaning the resulting biological effect depends on the overall amount of radiation absorbed over a lifetime.

Radiation Effects

• The thyroid is a gland that is highly vulnerable to radiation-caused cancer, and most susceptible to dental X-rays. It has been found that X-ray technicians, dental assistants and even dentists have experienced elevated risks of tumors and thyroid cancer due to repeated exposure to X-rays radiation. According to the American Academy of Family Physicians, the accepted cumulative dose of radiation during pregnancy is 5 rad, the equivalent of 50,000 dental X-ray examinations. Still, many dentists elect to postpone such exposure during a woman's pregnancy, unless it is an emergency.

Recent Studies

• In an April 2010 study in the journal Acta Oncologica, researchers discovered an elevated risk of developing thyroid cancer in patients that have had repeated dental X-rays. According to the study, patients who had had up to four dental X-rays were more than twice as likely to have developed the disease. By receiving between five and nine X-rays, the risk increased more than four-fold, and those who had had 10 or more X-rays had a 5.4 times higher risk than someone who had never been X-rayed.