Each tooth is a living part of body containing nerves and blood vessels. The part that is visible in mouth is crown and the longer portion anchored inside gum and bone is root.

If you see the internal parts of tooth, the outermost hardest white cover is called as enamel. The inner relatively less hard part is dentin. It surrounds the pulp containing blood vessels and nerves of the tooth. Pulp tissue is connected to the circulatory and nervous system via a foramen at the apex of the tooth. Surrounding the roots, which are also made up mainly of dentine, there is a thin bone like layer called cementum. The jawbone is connected with cementum through a shock-absorbing membrane, the periodontal ligament.

There are four different types of teeth in human beings. They vary in shape and size according to their particular function. They are:

1. Incisors: They are the front teeth, four upper and four in lower arch. They are shaped to bite and cut food into small pieces.

2. Canines: They are conical teeth at corner of mouth. Their function is to tear or shred the food.

3. Premolars: These are two in each side of both jaws just behind canines. These teeth have two cusps and they function to hold and crush the food.

4. Molars: They are three in number on each side of each jaw having bigger chewing surfaces for cutting food into smaller particles.

There are two sets of teeth during their lifetime. The first to appear are milk teeth and are helpful to the child not only in terms of chewing but also provide guidance for developing jaw and permanent dentition. The first milk tooth appear at about 6 months of age and then subsequently all 20 teeth erupt upto two and half years. The milk dentition has 2 incisors, one canine and 2 molar on each side of each jaw that makes 5 teeth each side and a total of 20 teeth in the mouth. The milk teeth are lighter in colour as compared to permanent teeth.

After the milk teeth, permanent teeth appear in the oral cavity starting from about six years. The first permanent molar comes at six years just behind the milk teeth on all four sides of jaw. At this time the milk teeth start falling and permanent teeth start replacing them. Subsequently most of the permanent teeth erupt till 12 years of age. The second molars erupt behind 1st molar at about 12-13 years and the third and last molar (wisdom teeth) erupt between 18-25 years. The permanent teeth are larger and darker in colour as compared to milk teeth. There are two incisors, one canine, two pre-molars and three molars making eight teeth in each quadrant and a total of thirty-two.

The Gums

The teeth remain embedded in jawbone which is covered from outside by gums. Health gums are coral pink in colour. They remain firmly attached to the underlying bone. Healthy gum can be identified by thin margins firmly adapting over the respective tooth and it does not bleed easily.

COMMON DENTAL DISEASES

There are four common dental diseases: the tooth decay or dental caries, inflammation of gums or gingivitis, irregular teeth or malocclusion and lastly oral cancer and pre-cancerous conditions. We will now review all the diseases and their prevention.