Facts about Teeth

Teeth are made not of a bone, but of four tissues of different density and hardness: enamel (the hardest substance of human body), dentin, cementum, and dental pulp.

Humans (and mammals in general) are diphyodont, i.e. they develop two sets of teeth during the lifetime: 20 milk teeth and 32 permanent ones. The presence of a higher-than-normal number of teeth is called hyperdontia.

Some animals have more than one set of teeth in their lifetime. For instance, sharks grow a new set of teeth every two weeks. And walrus tusks are canine teeth that never stop growing throughout life.

Caries is one of the most common diseases throughout the world. It is caused by acid-producing bacteria that live off the remains of foods, especially sugars and starches. To prevent tooth decay saliva helps neutralize the acids that increase the pH of the tooth surface.