polyphyodonts

Polyphyodonts are animals that continuously replace their teeth multiple times over their lifetime. This contrasts with diphyodonts, which have two successive sets (typically a deciduous or "baby" set and a permanent set), and monophyodonts, which develop only a single set of teeth. In polyphyodont species, new teeth form and erupt to take the place of worn or lost teeth, allowing long-term maintenance of dental function.

The best-known polyphyodonts are sharks, which replace teeth throughout life in a conveyor-like process as new teeth grow in rows behind the active row. Many reptiles are also polyphyodonts; crocodilians, for example, routinely shed and replace teeth even as adults. Other reptiles such as some snakes, lizards, and amphibians show various patterns of tooth replacement, though rates and regularity can differ widely among species and groups.

In mammals, dentition is typically diphyodont. Humans, for example, form a set of deciduous teeth that are replaced by a permanent set during development. Some mammals possess teeth that continue to grow or wear in a way that mimics renewal, but this is not true continuous replacement like that seen in many reptiles and fish.

Replacement teeth develop from dental tissues in the jaw—often from a dental lamina or tooth buds located behind the current teeth—and move into function as older teeth are shed or worn away. The frequency and timing of replacement vary by lineage and ecological needs, with faster replacement favored in habitats or diets that cause rapid tooth wear.

Overall, polyphyodonty is a widespread strategy in vertebrates, reflecting adaptations to maintain effective feeding across long lifespans and diverse diets.