The Tooth

Pearly Whites

We use our teeth to bite and chew food—the first stage in digestion. Babies start to get their first teeth, called milk or deciduous teeth, at about 6 months. By around age 2, children have 20 teeth: four central incisors, four lateral incisors, four canines and eight premolars. These teeth begin to fall out at around age 6, and adult, or permanent teeth, replace them.

Adults usually have 32 teeth: eight incisors, four canines, eight bicuspids, eight molars and four wisdom teeth. Wisdom teeth sometimes don’t appear until age 25, and in some cases, they never erupt through the gums.

Parts of a tooth

1. Crown: the part of the tooth that’s visible
2. Root: the part of the tooth that extends into the jawbone. It makes up about two-thirds of the tooth.
3. Enamel: the strong, white covering of the tooth
4. Dentin: a yellow bonelike material under the enamel and cementum. It contains nerve fibers.
5. Pulp: the soft center of the tooth. It contains blood vessels and nerves. It nourishes the tooth and sends signals to the brain.
6. Cementum: a layer of hard, tough tissue that covers the root. It helps attach the tooth to the jawbone
7. Periodontal ligament: the soft layer between the cementum and the jawbone.