The mixed dentition: when primary teeth give way to permanent ones
Six years of rebuilding – and the phase that decides whether there is enough space.
The change of teeth begins at around six years of age and lasts until about twelve. During this time, primary teeth and permanent teeth stand side by side – the mixed dentition. Much of what looks crooked in this phase sorts itself out. Some things do not.
The first permanent tooth is often overlooked
At around six years of age, the first permanent molar erupts behind the primary molars – without a primary tooth falling out beforehand. Many parents therefore take it for a primary tooth and do not take its care seriously enough. It is the tooth most frequently affected by caries of all.
Gaps are good
A primary dentition with gaps between the incisors is a good sign: the permanent teeth are larger and need the space. A gapless, even primary dentition looks prettier and frequently announces crowding.
When a primary tooth goes too early
Primary teeth keep the space free for their successors. If one is lost too early – through caries or an accident – the neighbouring teeth drift into the gap. The permanent tooth then finds no more space and erupts out of line or remains stuck in the bone. That is why a space maintainer is fitted in such cases: a small appliance that keeps the gap open.
What parents can watch for
Whether the teeth change roughly symmetrically – if one side lags clearly behind, that should be looked at. Whether a permanent tooth erupts behind the primary tooth instead of displacing it. And whether a primary tooth stays in place unusually long although the other side changed long ago.
The essentials at a glance
- The change of teeth lasts from about six to twelve years of age. Much of what looks crooked along the way sorts itself out.
- The first permanent molar arrives at six without a primary tooth falling out – and is therefore often overlooked.
- Gaps in the primary dentition are a good sign. A gapless primary dentition frequently announces crowding.
- A primary tooth lost too early costs space. A space maintainer keeps the gap open.
Answered briefly
Frequently asked questions
That depends on which tooth it is and how long it will be until the successor arrives. With a primary molar that is lost years before the change of teeth, a space maintainer usually makes sense. Have it looked at instead of waiting.
With the lower incisors this is common and often sorts itself out when the milk tooth falls out. If the milk tooth stays firmly in place, it should be extracted. Have it looked at promptly.
At around eight to nine years, when the permanent incisors are in place. That is why the first orthodontic examination is set at this age.
About six years, from age six to twelve. The wisdom teeth come – if they come – considerably later, usually between 17 and 25.