Types of Dentition

1. Diphyodont. Most mammals--humans included--typically develope and erupt into their jaws two generations of teeth. The term literally means "two generations of teeth."
2. Monophyodont. Some mammals--such as the manatee, seals, and walruses have only a single generation of teeth.
3. Polyphyodont. Most reptiles and fishes develope a lifetime of generations of successional teeth--as if on a conveyer belt. Such teeth have a brief functional life and are anatomically simple in design.
4. Homodont. In many vertebrates, all of the teeth in the jaw are alike. They differ from each other only in size. The alligator is an example of homodontism.
5. Heterodont. Most mammals, humans included, develope distinctive classes of teeth that are regionally specialized.
6. Anodontia is the developmental absence of teeth. Among mammals, the whalebone whale and the anteater are toothless; their ancestors had teeth. In humans, anodontia is a pathological condition. Partial anodontia is one or a few teeth missing.