A tooth is a calcified structure present in the jawbones of humans. The function of teeth is to help in chewing and tearing the food. Adult teeth are also known as permanent teeth. They develop by substituting the primary or milk teeth. Adult teeth start erupting around the age of six. As both the milk teeth and adult teeth are available in the mouth at the same time this phase is called dentition. Children have all their adult teeth till the second molars by the time they reach the age group of 12 to 14. Only the wisdom teeth or third molars appear later.
There are 32 adult teeth, 16 teeth in each jaw which consists of
8 Incisors: These have single root. The teeth are slim and pointed which is useful in cutting and slicing the food.
4 Canines: These also have single root. The teeth are pointed and used for gripping and ripping the food.
8 Premolars: These have double roots. The teeth have planes and sharp surfaces, and are used for mashing the food.
12 Molars: These have 3 branches to the roots. They are even and wide and used for chewing and grinding the food. The 12 molars include 4 wisdom teeth which develop much later.
The part of the tooth, which is not covered by the gum is called the crown. The part of the tooth, which remains implanted in the gum is called the root. The body of the tooth is made of a solid pale yellowish bonelike material known as dentine. Within the tooth lies the pulp cavity. It contains nerves, loose connective tissue and blood vessels. These cytoplasmic threads are pierced through the canals and spread over the dentine. The layer present on the surface of the teeth is known as enamel. It is made of apatite crystals. The apatite crystal consists of calcium phosphate, calcium fluoride and calcium chloride. These minerals are responsible for the firmness of the dentine. The tooth is fixed firmly in the jaw bone with the help of cementum, a bone like substance. Between the jaw bone and the cementum layer there is a tissue layer known as periodontal membrane.
Birth stage: The teeth are grown inside the jaws and do not appear until around the age of 6 months.
6 Months: When babies are around 6 months old, the first set of teeth appear. These teeth are called milk or deciduous teeth.
9 Months: The central and upper incisors are developed, 4 front teeth at the top and 4 front teeth in the bottom.
1 year: Lower first deciduous molars are developed at this age, then upper first deciduous molars (14months), then lower deciduous canines (16months) and later the upper canines (18months) erupt.
2 years: The upper and lower deciduous molars go off and around 2 ½ years all the deciduous teeth are seen in the mouth.
6 years: This is the age at which all the milk teeth are replaced with the permanent or adult teeth. The lower central incisor is lost first. This is the beginning of the development of adult teeth.
7 years: The lower central incisors erupt at this age. The upper and lower permanent molars are lost. The upper four deciduous central incisors fall out and are replaced by permanent teeth.
8 years: All the four lower permanent incisors are developed by this age.
9 years: All the four upper permanent incisors are developed by this age. The first deciduous molars get replaced by adult teeth.
10 years: The lower permanent canines are grown at this age and the second deciduous molars fall off.
11 years: The upper permanent canines develop in the place of upper deciduous canines and second permanent molars. This is the age at which almost the entire set of milk teeth usually falls off.
12 years: This is the stage at which the permanent second molars fall off.
13 years: At this age the average human being has 28 teeth. The upper and lower second molars are the final teeth to be developed before wisdom teeth.
17-21 years: The wisdom teeth erupt in this stage.
70+ years: By the time a human reaches the age of 70+ there are signs of darkening and falling of the teeth.
Children must be encouraged to follow proper oral hygiene regularly. Parents must motivate them to visit the dentist once in a year. In this way, they can easily overcome the problems of tooth decay and gum diseases. If not treated properly, periodontal problems may get aggravated and lead to the necessity of tooth extraction.