Copyright © 2007 Dorling Kindersley
Anchored firmly in the jawbones are the teeth. Our teeth are used to tear, chop, and grind food to make it soft enough to swallow and easier to digest.
The white, outer shell of a tooth is made of enamel, the hardest substance in the body. Under the enamel is a softer substance called dentine, and inside this is the soft, living heart of the tooth, called the pulp cavity.
If teeth are not properly cleaned, a mixture of bacteria and food, called plaque, builds up on them. As the bacteria feed on the sugary food debris, they produce an acid that dissolves the calcium minerals in enamel and dentine, forming a cavity. If the sensitive dentine layer is exposed, hot and cold foods can cause pain.