Dentist  Aleksandr  Melekhin,  DDS,  Ph.D.

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Dentition is the development of the primary (also called baby teeth, milk or deciduous teeth) and permanent (adult) teeth in the dental arch and their arrangement in the mouth. Typically, humans have 20 primary teeth and 32 permanent teeth.

dentition, primary tooth, permanent tooth, deciduous, baby, lacteal, milk tooth, tooth eruption,wisdom tooth, incisor, canine, premolar, molar,


Tooth eruption

Although tooth eruption occurs at different times for different people, a general eruption moment exists and pulls together in our Guide.

Tooth eruption has three stages:

  1. The first, known as primary stage, occurs when only primary teeth are visible.
  2. Once the first permanent tooth erupts into the mouth, the teeth are in the mixed (or transitional) dentition.
  3. After the last primary tooth falls out of the mouth, the teeth are in the permanent stage.

Primary Dentition

There are many different terms to describe Primary Dentition including: deciduous, baby, lacteal, and milk.

This stage starts on the arrival of the low (mandibular) central incisors, usually at eight (6-10) months, and lasts until the first permanent molars appear in the mouth, usually at six (6-7) years.

The 20 primary teeth typically erupt in the following order: (1) central incisor, (2) lateral incisor, (3) first molar, (4) canine, and (5) second molar (Dentition Guide).

As a general rule, four teeth erupt for every six months of life, low (mandibular) teeth erupt before upper (maxillary) teeth. Teeth erupt sooner in females than males.

The teeth erupt sooner in girls than boys.

Loss of the primary or deciduous dentition usually occurs between 5 to 7 years of age, although some children experience tooth loss earlier.

Children who lose their teeth at a young age (older than 2 and younger than 5) are at a greater risk for periodontal and gum disease.

The tooth buds of permanent teeth develop below the primary teeth, close to the palate or tongue.

Mixed Stage

Mixed dentition starts when the first permanent molar appears in the mouth, usually at six (6-7) years, and lasts until the last primary tooth is lost, usually at eleven or twelve years.

Upper (maxillary) permanent teeth erupt in a different order from low (mandibular) permanent teeth.

Upper teeth erupt in the following order: (1) first molar (2) central incisor, (3) lateral incisor, (4) first premolar, (5) second premolar, (6) canine, (7) second molar, and (8) third molar (Dentition Guide).

Low teeth erupt in the following order: (1) first molar (2) central incisor, (3) lateral incisor, (4) canine, (5) first premolar, (6) second premolar, (7) second molar, and (8) third molar (Dentition Guide).
Since there are no premolars in the primary dentition, the primary molars are replaced by permanent premolars.
If any primary teeth are lost before permanent teeth are ready to replace them, some posterior teeth may drift forward and cause space to be lost in the mouth.
This may cause crowding and/or misplacement once the permanent teeth erupt, which is usually referred to as malocclusion.
Qualified Community Specialists (Orthodontist)  may be required  in such circumstances for children to achieve a straight set of teeth ("Braces").

Permanent Teeth

The permanent dentition (32 permanent teeth) begins when the last primary or baby tooth is lost, usually at 11 to 12 years, and lasts for the rest of a person's life or until all of the teeth are lost (edentulism).
During this stage, third molars (also called "Wisdom Tooth") are frequently extracted because of decay, pain or impactions.
The main reasons for tooth loss are Tooth Decay or Gum Disease.


  • For every 6 months of life, approximately 4 teeth will erupt
  • Lower teeth usually erupt before upper teeth
  • The teeth in both jaws usually erupt in pairs one on the right and one on the left
  • Primary teeth are smaller and whiter than the permanent teeth that will follow
  • Girls generally go before boys in tooth eruption
  • By the time a child is 2 to 3 years of age, all primary teeth should have erupted
  • Shortly after age 4, the jaw of the child begins to grow, creating spaces between the primary teeth
  • That provides the necessary space for the larger permanent teeth to erupt
  • Between the ages of 6 and 12, a mixture of both primary teeth and permanent teeth exist in the mouth

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Aleksandr V. Melekhin, DDS


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