Tuesday, April 24, 2012

The Human Teeth

        Human beings have tow sets of teeth during their life time: primary teeth and permanent teeth. Primary teeth are also called deciduous or milk or baby teeth and begin to break through the gums after the age of six months. All the 20 primary teeth are in place by the child is three years old. The permanent teeth begin forcing out and replacing the primary teeth when the child is about six years old. All the 32 permanent teeth are in place usually when the person is in his/her early 20s.

          The 32 permanent teeth are arranged in pairs on each side of the upper and lower jaws. There are four types of teeth: incisors, canines, bicuspids or premolars and molars. The incisors are the eight front teeth, four in each jaw. The canines are four pointed teeth, one on each side of the incisors, two in each jaw. Next to the canines are two bicuspids, four in each jaw. Next to the bicuspids are six molars, three in each jaw.

          All the teeth have two parts: the crown and the root. The crown is the part of the tooth that is above the gum line. The root is below the gum. The part of the tooth at the gum line, where the crown and the root meet, is called the neck. The root is held light in the jawbone by a layer of bone tissue called cement.

          All true teeth are made up of three layers-------the outer hardest layer is called enamel, inside the enamel layer is dentine and the inner most layer is pulp. Dentine is like bone and its inside is called the pulp cavity that contains tiny blood vessels and nerves. The dentine is nourished by the pulp. 
Inside the tooth
Baby teeth
Permanent Teeth