There are 20 milk teeth, which are much smaller than the 32 adult permanent teeth. This ‘primary teeth’ set of teeth is made up of four incisors, two canines and four molars in each jaw.
The milk teeth start forming in the womb and first come through somewhere between five and eight months, although this can vary and boys are often a little later than girls. The last of these primary teeth normally come through when a child is between two and three years old.
Milk teeth start falling out at around six years and up to 12 years old on average. In each jaw, the four primary incisors are replaced by the four permanent incisors, the two primary canines are replaced by the two permanent canines and the four primary molars are replaced by four permanent pre-molars.
At around six years old, the first four permanent molars appear at the back of the mouth. They do not have milk teeth ’equivalents’.
By the age of 13, a child doesn’t normally have any primary teeth left, and has 28 of the 32 permanent adult teeth in their mouths. The final permanent teeth to appear are usually the third molars or wisdom teeth (see above), which can come through any time from late teens to early or even mid-twenties, if at all.
The importance of milk teeth
As primary teeth fall out, it is a common misconception that they do not matter. The primary teeth have a number of important roles:
- Primary teeth are essential in the first step of digesting food: chewing, biting and grinding.
- Primary teeth act as guides for the permanent teeth; by keeping proper spaces in the mouth, they help ensure permanent teeth enter the mouth in the correct places. If primary teeth are lost early through decay there is more chance of permanent teeth, becoming crooked or even blocked by other teeth.
- Primary teeth influence the development and growth of the face and jaw muscles.
- Tooth decay and disease present in primary teeth can easily pass on to permanent teeth as they erupt. Primary molars remain in the mouth until around 10 to 12 years of age with lots of opportunity to pass decay on to their new permanent neighbours.
- If it spreads to the root, an infection in a decayed primary tooth can damage the developing permanent tooth lying directly underneath.
Why you need to watch out when the adult teeth start to come through (the mixed dentition period)
The beginning of a period of mixed teeth sizes starts around six years of age, with both primary and permanent teeth in the mouth:
- The new permanent teeth are not fully mature. The first few years in the mouth are critical as these teeth are weaker and more vulnerable to tooth decay.
- The ‘six year molars’ are particularly prone to cavities – they are the first permanent tooth to arrive in the mouth and erupt at the back behind the primary teeth, so they are easy to forget about.
- The unevenness of the mixed milk and permanent teeth make them more difficult to clean and protect.
Click here to go back to the list of all articles in the For Parents section