A polyphyodont is any animal whose teeth are continually replaced. In contrast, diphyodonts are characterized by having only two successive sets of teeth.
Nile crocodile (Crocodylus niloticus)
A tooth is a hard, calcified structure found in the jaws of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tearing food, for defensive purposes, to intimidate other animals often including their own, or to carry prey or their young. The roots of teeth are covered by gums. Teeth are not made of bone, but rather of multiple tissues of varying density and hardness that originate from the outermost embryonic germ layer, the ectoderm.
Section through the ivory tusk of a mammoth
Buccal view of top incisor from Rattus rattus. Top incisor outlined in yellow. Molars circled in blue.
Buccal view of the lower incisor from the right dentary of a Rattus rattus
Lingual view of the lower incisor from the right dentary of a Rattus rattus