Types of Teeth in Humans, Diagram and Functions

One of the most fascinating Biology Topics is the study of genetics and how traits are passed down through generations.

What are the four types of teeth?

Before food can be used by the body, it must be broken down into small pieces. The first part of this breakdown of food is done by the teeth. We chew the food with the teeth and break it down mechanically into small pieces. This is discussed below.

There are four types of teeth in our mouth. These are:

1. Incisors,
2. Canines,
3. Premolars, and
4. Molars.

The four types of teeth are shown in Figure. The upper part of a tooth (which we can see in the mouth) is called crown, the middle part of a tooth (which is inside the gums) is called neck whereas the lower part of a tooth (which is embedded in the jaw bone) is called root. Every tooth is held in a separate socket in the jaw. The positions of four types of teeth in the mouth are shown in Figure. Different types of teeth differ in appearance and perform different functions.

This is discussed below

(i) Incisors are the chisel-shaped teeth at the front of the mouth (see Figure). The incisors are
for biting and cutting the food. There are four incisors in the centre of each jaw.

(ii) Canines are the large, pointed teeth just behind the incisors (see Figure). The canines are for types of teeth (Incisors, canines, premolars and piercing and tearing the food. There are two canines in each jaw, one behind the left incisor and the other behind right incisor.

(iii) Premolars are the large teeth just behind the canines on each side (see Figure). Premolars have large, flat surfaces. The premolars are for chewing and grinding the food. There are four premolars in a jaw, two on each side.

(iv) Molars are very large teeth which are present just behind the premolars, towards the back of our mouth (see Figure). The molars have a larger surface area than premolars. The function of molars is the same as that of premolars. That is, molars are for chewing and grinding the food. There are six molars in each jaw, three on each side. Please note that molars are present only in the permanent set of teeth. They are not present in the temporary set of teeth called milk teeth.

Most of the adult men and women have a total of 32 teeth. Of these, 16 are in the upper jaw and 16 are in the upper jaw. The 16 teeth of each jaw consist of 4 incisors, 2 canines, 4 premolars and 6 molars. The teeth of upper jaw match with the teeth of lower jaw.

Milk Teeth and Permanent Teeth

In human beings, the teeth grow twice. First time the teeth grow when one is a small baby (or infant). This set of teeth is called milk teeth. Thus, the first set of teeth which grow during infancy (babyhood) are called milk teeth. Milk teeth are a temporary set of teeth. The milk teeth loosen and begin to fall off at the age between 6 and 8 years. When milk teeth fall off in a child, then another set of teeth grow in their place. So, second time the teeth grow when one is a child. The second set of teeth is called permanent teeth. The permanent teeth grow in place of milk teeth. The permanent set of teeth remains till the old age. But when old people lose their permanent teeth, then new teeth do not grow in their place.

Tooth Decay

The white, hard outer covering of tooth is called enamel (see Figure). The part of tooth below the enamel is called dentine. Dentine is similar to bone. Inside the dentine is pulp cavity which contains nerves and blood vessels. If the teeth are not cleaned regularly, then tooth decay can take place. Tooth decay is a process in which the tooth becomes rotten due to the formation of cavities (holes) inside it leading to toothache. Tooth decay occurs as follows.

If we do not clean our teeth and mouth after eating food, then many harmful bacteria begin to grow and live on the teeth. These bacteria act on the sugar present in the left-over food particles sticking to the teeth to form acid. The acid thus formed eats up the enamel and dentine of the tooth gradually and ultimately makes a cavity (or hole) in the tooth [see Figure (a)]. When this cavity (or hole) reaches the pulp cavity of the tooth (which contains nerves), our tooth becomes painful and we get toothache [see Figure (b)], If the cavities caused by

tooth decay are not treated in time (by fillings, etc.) by a dentist, then it causes severe toothache. In extreme cases, tooth decay can lead to the loss of whole tooth (because it may require extraction). Excessive use of sugar containing foods such as sweets, chocolates, toffees, ice cream and cold drinks, etc., are the major cause of tooth decay. Tooth decay can be prevented in the following ways :

1. We should rinse the mouth thoroughly with clean water after every meal.
2. We should clean our teeth with a brush and toothpaste at least twice a day.
3. A dental floss should be used to take out food particles trapped between the teeth. (Dental floss is a soft thread used to clean between the teeth).
4. We should eat less of sugary foods such as sweets, chocolates, toffees, and ice cream, etc. Too many cold drinks should also be avoided (this is because sugar + bacteria – acid which eats up tooth).