Perhaps, you’re wondering why humans only have two sets of teeth. Unlike the human hair which regenerates multiple times in a lifetime, human tooth regeneration only happens once. Primary set of teeth is replaced when our deciduous teeth, commonly called as milk or baby teeth, is lost. Tooth regeneration is common to primitive animals but humans have limitations because of fewer stem cells around. This is the case that scientists are aiming to achieve so as to easily assist tooth regrowth by using stem cells.