Take care of your teeth! Part 1
Brief Description: Teeth are invaluable to everyone. Here are some basic and interesting facts you should know about your teeth!
Teeth are invaluable to everyone. They enable you to cut and grind the morsel of food, which is moistened by saliva. Biting the food makes it small enough to pass down the gullet into the stomach. Digestion is made easier if these pieces of food are crushed into even smaller particles by the action of chewing. You will have heard grown ups tell children to "chew the food properly", as this makes easier for the stomach to digest the food.

In a lifetime, we are given only two sets of teeth. At birth, a human baby has no teeth, but normally after six months the first teeth appear in the centre of the lower jaw. By the time the infant is two years old, he is the proud owner of a set of 20 teeth called "milk teeth". There are ten in each jaw.

At the age of six or seven years, these teeth begin to fall out and are replaced with a permanent set of teeth. In addition, three more teeth, the molars, erupt on each side in the back part of the jaw.

The permanent set consists of 32 teeth among them and the four "wisdom teeth" which are located at the back of each jaw. These wisdom teeth usually erupt during the late teens.

Teeth are given different names according to their position in the jaw. The 32 teeth include four incisors (these help to cut food); two cuspids or canines (tear food); four bicuspids (tear and crush food); and six molars (grind food) in each jaw.

Incisors, or the front teeth help cut pieces off the food, as when biting into an apple or taking a bite out of a sandwich. Canines are located on each side of the incisors. They are a little pointed they function as extra incisors. Bicuspids are also known as premolars.

The premolars and molars are similar in function. Their knobbly surfaces meet when the jaws are closed, and crush the food into small pieces.

As well as breaking the food into a suitable size for swallowing, the crushing action of the molars and premolars reduces food to quite small particles. Small particles of food are easier than large pieces because they offer a greater surface area to the digestive enzymes.

The structure of the tooth is as follows: the outer layer of the tooth has a "skin" of enamel. Enamel covers the exposed part, or crown of the tooth and makes a hard biting surface. It is mainly calcium phosphate, the hardest mineral substance in the body. Since the enamel contains no nerves, it is insensitive to pain.

Under the enamel comes the dentine, which is related to the bone. Dentine is softer than enamel. It is a living tissue with threads of cytoplasm running through it. Tooth sensitivity begins here.

The hardness of both enamel and dentine depends on there being enough calcium in the diet and sufficient vitamin D to help the absorption of calcium in the intestine.

Beneath the dentine lies the pulp, a relatively soft material containing nerves, blood vessels and cells that radiate into the dentine.

These blood vessels bring food and oxygen, so that the tooth can grow at first and then remain alive when growth has stopped. The sensory nerve endings in the pulp are sensitive to heat and cold but give only the sensation of pain. If you plunge your teeth into an ice-cream, they do not feel cold but they do hurt.

The reason why teeth do not fall out easily is because they are anchored by "cementum". This cement is a bone like tissue which covers the root of the tooth. In the cement are embedded thousands of tough fibres which pass into the bone of the jaw and hold the tooth in place.