Tooth Eruption

Primary teeth are also known as temporary, milk, or baby teeth. It is the first set of teeth your baby grows while growing up. Secondary teeth on the other hand are known as permanent or adult teeth and they grow after the fall out of the primary ones. The primary teeth start erupting around 6 months while the permanent ones start erupting around 6 years.

Before we go any further, let’s make clear some particular terms we’d be using in this article.

First, eruption time: This is the time that you’ll first see a tooth come out. On the other hand, fallout time is the time around which your baby’s primary tooth is expected to remove.

As you continue in this article, you will find out how teeth erupt, the eruption and fallout time for primary teeth, the eruption time for the permanent teeth, some important facts about the primary teeth, and why you should care for them.

How Teeth Erupt

The primary or milk teeth are the first to erupt in babies and they are already formed under the gums before birth. Babies are usually born with a full set of 20 teeth beneath their gums. After the eruption of the crown of the teeth, the roots take about 3 to 5 years for their formation to be completed.

tooth eruption

After your child is 4 years, the jaws and bones of the face begin to grow, thereby creating spaces between the primary teeth. This growth is completely natural and it is needed so that the permanent teeth which are quite larger than the primary ones, will have enough space to grow in.

Eruption and fall out time of primary teeth

Here’s a table that shows the time at which primary teeth start coming in and the time at which they fall out. However, you should remember that this is only a guide as variations exist from child to child. Your child can start earlier than stated or a bit later.

Upper Teeth

ToothEruption timeFall out time
Central incisor8 to 12 months6 to 7 years
Lateral incisor9 to 13 months7 to 8 years
Canine16 to 22 months10 to 12 years
First molar13 to 19 months9 to 11 years
Second molar25 to 33 months10 to 12 years

Lower Teeth

ToothEruption timeFall out time
Central incisor6 to 10 months6 to 7 years
Lateral incisor10 to 16 months7 to 8 years
Canine17 to 23 months9 to 12 years
First molar14 to 18 months9 to 11 years
Second molar23 to 31 months10 to 12 years

From the table above, we can see that the two lower central incisors are the first to erupt.

This eruption begins at about 6 months. This is followed by the upper incisors teeth. Once this is done, the other teeth begin to appear in pairs – one on each side of either of the jaw until all the 20 primary teeth are filled up. These 20 teeth are distributed as 10 in the upper jaw and 10 in the lower jaw.

By the time your baby is done with growing these primary teeth, he or she will be around 2½ to 3 years old. These primary teeth will stay in the mouth until around 6 years.

Important facts you need to know about the primary teeth

Asides from knowing the expected eruption and fallout times for your child’s primary teeth, there are other facts you need to also bear in mind. read our article on eruption cyst

  • First, a general rule of thumb when it comes to the eruption of primary tooth is that in every 6 months of life, about 4 teeth will erupt.
  • Eruption of the lower tooth usually precedes the corresponding upper tooth.
  • Also bear in mind that tooth eruption in girls tend to start earlier compared with that in boys.
  • Teeth erupt in pairs in a jaw – the right and the left.
  • Generally, the primary teeth are quite smaller and whiter in color than the permanent teeth.

Why do you need to care for the primary teeth if it will eventually fall out?

Despite the fact that primary dentition have not come to stay, they didn’t come to play either. During their short period of stay, they play very important and vital roles. Some of these roles include:

  • They help in speech development
  • They help the face maintain its normal appearance
  • They help to attain good nutrition, as delayed or missing teeth make chewing difficult
  • They help to keep or reserve space for the permanent teeth

The primary teeth are the first tenants of the gum and they prepare the space for the permanent teeth to grow in.

That being said, let’s talk about permanent teeth. You can read about teething pills for babies

Eruption time of permanent teeth

The details of the eruption time of the permanent teeth are shown in the table below:

Upper Teeth

ToothEruption time
Central incisor7 to 8 years
Lateral incisor8 to 9 years
Canine11 to 12 years
First premolar10 to 11 years
Second premolar10 to 12 years
First molar6 to 7 years
Second molar12 to 13 years
Third molar (also called wisdom teeth)17 to 21 years

Lower Teeth

ToothEruption time
Central incisor6 to 7 years
Lateral incisor7 to 8 years
Canine9 to 10 years
First premolar10 to 12 years
Second premolar11 to 12 years
First molar6 to 7 years
Second molar11 to 13 years
Third molar (also called wisdom tooth)17 to 21 years

Variations still exist in the eruption time of the permanent teeth in that in some children, the first permanent molars are the first to erupt while in some children, the incisors are the first to emerge. But in most children, about 28 permanent teeth would have erupted by the age of 13.

The remaining four teeth, which are usually the third molars erupt between ages 17 to 21. This totals the 32 permanent teeth seen in adults.


Tooth eruption is a very important landmark in the growth of your child. In this phase, you need to pay attention to both the hygiene and the health of your child’s teeth. If need be, you should see a pediatric dentist. You can also read about how to brush your babies teeth and how long does teething last article

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Inger Kjær, “Mechanism of Human Tooth Eruption: Review Article Including a New Theory for Future Studies on the Eruption Process”, Scientifica, vol. 2014, Article ID 341905, 13 pages, 2014.