The Tooth Fairy's New Tricks

Kids who lose a baby tooth will often put it under their pillow for the Tooth Fairy. But Julia Shi's dad Songtai is a dentist and a medical researcher at the National Institutes of Health. When Julia, then 6, shed a tooth recently, they noticed that a little piece of red pulp was still attached. That gave him an idea, and the next time she lost a tooth, he placed it in a liquid used to culture cells. Back at the lab, he extracted the pulp and found that it contained a number of stem cells, those special progenitor cells that can be used to replenish various types of tissue. (He also gave Julia back her tooth.)

The finding won't eliminate the controversy around stem-cell research. Unlike the stem cells found in embryos, which can become anything from skin to nerves to muscle, the stem cells in baby teeth seem to transform themselves only into bone, nerve and fat cells, limiting their usefulness. They do, however, grow more quickly than stem cells found in full-grown adults. It's too early to suggest that children should start banking their baby teeth — and Shi for now has all the teeth he needs. Still, the Tooth Fairy must be very proud.