Using mass spectrometry technology, scientists analyzed radiocarbon levels in 33 teeth from 22 dead individuals who lived in northern Sweden. These people, whose ages were known, all had similar diets.
The researchers then compared the radiocarbon levels in the teeth with the levels of atmospheric radiocarbon recorded in various years to determine when the teeth formed in each person.
"When you think of the strategy, it's not surprising that it works," Frisén said.
The researchers were able to pinpoint within 18 months the age of the teeth. Other methods, including the analysis of wear on teeth, are accurate only to within five to ten years.
"It turned out to be much better than we expected," Buchholz said. "It's a very powerful technique."
However, it does not work for individuals born before 1943. That's because atmospheric radiocarbon levels did not vary before nuclear testing began in 1955, and the final formation of enamel is for wisdom teeth at 12 years of age.
The researchers emphasize that enamel dating cannot identify a specific personthat requires DNA analysisbut the method can be used to narrow down the number of people on a list of missing people in a disaster, for example.
"Knowing the age of an individual allows [us to] narrow in on fewer potential identities," Frisén said. "This is a strategy that has been used for ages, but with less precision than what can now be done."
Swedish forensic scientists found the technique to be particularly useful in narrowing their search for victims of the Southeast Asia tsunami. When bodies are left in water, as was the case with tsunami victims, they quickly deteriorate and become very difficult to identify.
"DNA analysis is favored, but [it] calls for access to DNA," Frisén said. "The current technique can aid when DNA identification cannot be done."
Buchholz says his laboratory has made the technology available to authorities dealing with the aftermath of Hurricane Katrina.
"It's available if they want it," he said. "They will determine if they need it."
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