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You are here: BBC Science > Human Body & Mind > The Body > Skeleton
Fact files

Skeleton - Teeth

Food processing: Teeth cut through and chew up food, preparing it for digestion

Enamel: Is the hardest substance in the human body

Tooth decay: Bacteria in your mouth produce acid which rots your teeth

Teeth break down food

Your teeth prepare food for digestion by breaking it down and chewing it up. They do this by cutting, tearing, crushing and grinding:

  • Your eight flat front teeth are good for biting, scraping and cutting. They are called incisors
  • Your four cone shaped canines are good at piercing and tearing food
  • The teeth that crush and grind your food are your eight blunt premolars and your twelve broader, larger molars

Hard teeth have a soft centre

Your teeth are covered in enamel, which is the hardest substance in your body. It covers the exposed part of your teeth above your gum. The roots of your teeth are fixed into a socket in your jawbone.

Although your teeth are hard on the outside, they actually have a soft centre. Inside your teeth is a cavity filled with pulp. Pulp is made up of connective tissue, blood vessels, and nerve fibres. It supplies nutrients to your teeth. The pulp cavity extends into the root of your teeth, forming the root canal.

Two sets of teeth

The first set of teeth known as deciduous or milk teeth erupts through the gums between eight months and three years of age. Milk teeth become loose and start to fall out as permanent teeth push through the gums at about six years of age. A full set of 32 permanent teeth is complete when wisdom teeth appear in the late teens or early twenties.

The reason you have two sets of teeth probably comes down to size. A full set of permanent teeth would be too big to fit into a young child's mouth. So milk teeth act as a bridge until the jaw is large enough to accommodate a full set of permanent teeth.

Wisdom teeth

The last teeth that emerge are your wisdom teeth. It's not clear what their function is, but some experts believe they're a remnant from a time when our ancestors had a more rugged diet and, as a result, longer, larger jaws. Now our jaws are smaller, there often isn't enough room for them, which is why wisdom teeth can cause problems.

Tooth decay

There are bacteria in your mouth that multiply when you eat sweet food. As these bacteria feed on food stuck on your teeth, they produce acid. This acid can dissolve enamel and eat through a tooth, right down to the nerve in its pulp cavity. A hole in a tooth like this provides a route for bacteria in your mouth to cause nasty infections in the root of a tooth. This can result in excruciating toothache.

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