The teeth has three parts:
Crown: Outer part covered with enamel (hardest substance).
Neck: Joint between crown and root covered with gum.
Root: Part within the socket of the jaw bone.
Enamel is ectodermal in origin from amaeloblast cells, where as the dentine is mesodermal in origin from odontoblast cells.
A peridontal membrane is present between the root and the socket. Dentine constitutes main part of the tooth with a pulp cavity which contains connective tissue, blood vessels and nerves.
A layer of odontoblast or tooth forming cells lines pulp cavity.
Types of Teeth
1. Homodont – All teeth of same type e.g., Fishes, Amphibians, Reptiles.
2. Heterodont – Different types of teeth e.g.. incisor, canine, premolar, and molar as in mammals.
3. Pleurodont – Teeth attached by their sides to the rim of jaw or in groves as in certain lizards.
4. Thecodont – Teeth attached within socket of jaw bone e.g., in mammals and crocodiles.
5. Acrodont – Teeth flat surface of jaw bone e.g., Amphibia (frog), lizards.
6. Monophyodont – Teeth formed only once in life time e.g. Kangaroo.
7. Diphyodont – Two sets of teeth formed in life time, as milk teeth and permanent teeth.
8. Polyphyodont – Teeth formed and fall many times e.g., fishes, frogs, lizards.
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