Researchers at King's College London were able to grow teeth from human epithelial cells taken from gums. They grew these teeth in the mouths of mice, which is a long way from growing them in humans, so don't expect to regrow your teeth if you're already on the way to losing them.
In the latest study they took human epithelial cells from the gums of human patients, grew more of them in the lab and mixed them with mesenchyme cells from mice.
The mesenchyme cells were cultured to be "inducing" - they instruct the epithelial cells to start growing into a tooth.
Transplanting the cell combination into mice, researchers were able to grow hybrid human/mouse teeth that had viable roots, they reported in the Journal of Dental Research.