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Dentition. Types of teeth. Function of teeth

author icon By Dr. George Ghidrai

Teeth are the hardest structures of the human body. The type, number, and arrangement of a set of teeth represent the dentition.

Humans have two sets of teeth:

  • Primary teeth

    Primary teeth are also known as deciduous teeth, milk teeth, baby teeth or temporary teeth. Primary teeth start to form during the embryo phase and erupt during infancy (from 6 months to 3 years).

    Normally, there are 20 primary teeth, 10 on each dental arch: 4 incisors (2 central incisors and 2 lateral incisors), 2 canines and 4 molars.

    primary dentition primary dentition primary dentition

    Generally, by the age of 12 to 14 years, all primary teeth are replaced by permanent teeth but in the absence of permanent replacements, they can remain functional for many years.

  • Permanent teeth

    Permanent teeth (or adult teeth) are the second set of teeth and normally consist of 32 teeth. The first permanent teeth appear around the age of 6 and are usually the first molars which erupt right behind the last "milk" molars of the primary dentition.

    The permanent premolars will replace the milk molars of the primary dentition and all permanent molars will erupt behind the deciduous teeth.

    permanent dentition

    Up to the age of thirteen years, twenty-eight of the thirty-two permanent teeth will appear. The four last permanent teeth, the third molars or the wisdom teeth, usually appear between the ages of 17 and 25 years.

Function of teeth


Chewing is the main function of teeth. Teeth are part of the digestive system; chewing is the first stage of the process of digestion.

Food needs to be broken down and chewed before entering the digestive system so that the body can easily absorb nutrients from them. In the absence of teeth, digestion is hampered leading to significant disturbances in food absorption.

Depending on their position and type, teeth have a role in shearing, tearing or grinding food.


Teeth, especially those located in visible areas, have an important aesthetic role. The position, shape, and shade of teeth have a pronounced impact in shaping each individual personality.


Teeth can help us pronounce accurately as they have an important role in the pronunciation of consonants. When teeth are missing (especially upper front teeth), the normal speech can be severally affected.

Types of teeth

Typically, humans have 32 permanent teeth: 16 on the upper arch and 16 on the lower arch. Sometimes, due to genetic disorders, birth defects or eruption problems, more or fewer teeth are present.

Teeth are divided into four main groups, each with a well-defined position and function.

Last review and update: February 2019

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