In the past, growing body parts like this has possible with embryonic cells, which come with a host of political issues, which is why finding another way to get it to work is important. Scientists extracted epithelial cells from the gums of human adults and cultured them in a lab, then mixed them with mescenchymal tooth cells of embryonic mice. After a week, they transplanted this mixture into the protective tissue around the kidneys of living mice. There, some of the cells developed into a hybrid of human and mice teeth, complete with dentine and enamel.
This puts the science a ways off from usage in your dentist's office, but it’s an exciting beginning. The next step is figuring out how to do this without the mice. Still, being able to grow teeth at all is certainly a major step forward.
