Chip of tooth tells radiation dose

WASHINGTON — A tiny chip of tooth enamel can tell the tale of radiation exposure, scientists report February 16 at a meeting of the American Physical Society. The technique may allow researchers to better understand the links between radiation exposure and illnesses such as cancer. Knowing normal levels of radiation exposure is important in the event of acute exposures, such as the detonation of a radioactive bomb or nuclear power plant accidents.

“Dental enamel is quite a remarkable material,” said study coauthor Barry Pass of Howard University in Washington, D.C. “It’s a marvelous chronicle of the environment. There’s a world of information in the tooth.”

Radioactivity creates long-lived unpaired electrons when it hits tooth enamel. The higher the radioactive dose, the more unpaired electrons are created in the tooth. Researchers can detect and quantify this signal with a method called electronic paramagnetic resonance, which relies on electromagnetic waves hitting the tooth and interacting with the unpaired electrons. In this way, teeth function as a reliable dosimeter, Pass said.

Earlier attempts to use this technique required sample sizes of 100 milligrams or more, which often meant an entire tooth had to be extracted. By using a higher frequency of electromagnetic waves to probe the enamel, Pass and colleagues could accurately determine radiation doses from samples as small as 2 milligrams, he reported. These tiny “enamel biopsies” must be removed from the tooth, but are so small that they don’t interfere with the tooth’s function.