Researchers have regrown teeth in rats by manipulating existing stem cells: "a new technique [can] orchestrate the body's stem cells to migrate to three-dimensional scaffold that is infused with growth factor. This can yield an anatomically correct tooth in as soon as nine weeks once implanted in the mouth. ... These findings represent the first report of regeneration of anatomically shaped tooth-like structures in vivo, and by cell homing without cell delivery. ... By homing stem cells to a scaffold made of natural materials and integrated in surrounding tissue, there is no need to use harvested stem cell lines, or create a an environment outside of the body (e.g., a Petri dish) where the tooth is grown and then implanted once it has matured. The tooth instead can be grown 'orthotopically,' or in the socket where the tooth will integrate with surrounding tissue in ways that are impossible with hard metals or other materials. ... A key consideration in tooth regeneration is finding a cost-effective approach that can translate into therapies for patients who cannot afford or who aren't good candidates for dental implants. Cell-homing-based tooth regeneration may provide a tangible pathway toward clinical translation."