Tooth

Teeth are hard, bonelike structures in the jaws used for biting and chewing. They are composed of calcium, phosphorus and other mineral salts, and they have three layers. The hard, shiny layer that we brush is called the enamel. It serves as a protective coating and covers the crown of the tooth, which exists above the gum line.

The dentine is a second protective layer that covers the tooth’s nerves. At the center of each tooth is the pulp, which houses the blood vessels, nerves and connective tissue.

Teeth have two basic parts: a root to anchor the tooth to the jaw and a crown above the gum line. The root is covered with a hard material called cementum. Humans have four different types of teeth, each of which serves a different function:
• Incisors- used for cutting through food to break it up into bites.
• Cuspids- also referred to as canines; these teeth tear into food.
• Bicuspids- used for tearing and crushing food.
• Molars- teeth with larger, flatter surfaces used to grind and crush food.

These four types of teeth used together enable people to eat both meats and vegetables.

By the time children are 3 or 4 years old, they have 20 teeth. These teeth are called deciduous teeth and between about age 6 and 12, children will lose these teeth. As they lose them, the deciduous teeth are replaced by 32 permanent teeth. Some people are born without some of these 32 teeth and others may actually have additional teeth. These extra teeth are called supernumerary teeth.