A Japanese group, led by cell biologist Takashi Tsuji of Tokyo University of Science in Noda, Chiba Prefecture, focused on tooth germs, the embryonic tissues that develop into teeth. After obtaining such germs from mouse embryos, they separated out two types of cells–epithelial cells and mesenchymal cells–and then recombined them into a new bioengineered tooth germ. The team then grew the bioengineered germs in a special culture for 5 to 7 days and transplanted them into the upper jaws of adult mice in the place of an extracted molar. New teeth poked through the gums after about 36 days and reached the proper size and alignment with opposing teeth for proper chewing after 49 days.

All indications are that the teeth function just like the real thing. They have the roots, inner pulp, and outer enamel of normal teeth and are just as hard, the team reports. Moreover, unlike dental implants, the regenerated teeth develop the periodontal ligaments that tie normal teeth to the supporting bone and the nerve fibers that give sensitivity to chewing pressure and other stresses. “We clearly demonstrated that the bioengineered organ germ could develop into a fully functioning organ,” Tsuji says