[1][2][3] Most mammals are diphyodonts—as to chew their food they need a strong, durable and complete set of teeth.
Diphyodonts also differ from monophyodonts, which are animals who have only one set of teeth that does not change over a long period of growth.
In some cases hypodontia or hyperdontia occurs, the latter in cleidocranial dysostosis and Gardner's syndrome.
The house shrew, Suncus murinus, the Chinese miniature pig,[5][6] mice, and ferrets[7] are currently being used to study the diphyodont replacement of the deciduous dentition by replacements and additional permanent teeth.
Manatees, elephants and kangaroos differ from most other mammals because they are polyphyodonts.