Underbite: when the lower teeth sit in front of the upper ones
The rarer but more urgent malocclusion – and the reason why one does not wait here.
In an underbite, the lower front teeth bite in front of the upper ones. The technical terms are prognathism or mesial occlusion. This malocclusion is considerably rarer than the overbite – and it is the only one where, as a rule, one does not wait.
Why time is pressing here
An underbite intensifies with growth instead of evening out: the lower jaw grows for longer than the upper jaw, and the longer the incorrect interlocking persists, the more it holds the upper jaw back. That is why treatment here often starts in the primary dentition or early mixed dentition.
The treatment
During growth, the upper jaw is guided forward, usually with a face mask combined with palatal expansion. This demands cooperation: the mask is worn at night. Once growth is complete, in pronounced cases the only option left is combined treatment involving orthodontics and jaw surgery.
How to recognize it
The chin appears prominent, the upper lip rather flat. When biting down, the lower front teeth can be seen in front of the upper ones. Some children push the lower jaw forward when biting down because the teeth do not fit together otherwise – that is a forced bite and should be examined.
The key facts at a glance
- In an underbite, the lower front teeth sit in front of the upper ones. It is rare, but the most urgent malocclusion.
- It intensifies with growth instead of evening out – which is why treatment often starts in the primary or early mixed dentition.
- During growth, the upper jaw is guided forward, usually with a face mask and palatal expansion.
- Once growth is complete, in pronounced cases the only remaining option is combined treatment including surgery.
Answered briefly
Frequently asked questions
As soon as it is detected. Unlike with most malocclusions, here you do not wait for the change of teeth. Treatment in the primary or early mixed dentition can avoid a later operation or at least reduce its extent.
Often yes – jaw size is strongly hereditary. But there are also acquired forms, for instance through a forced bite: if the teeth do not fit together, the child pushes the lower jaw forward, and that shapes development.
During growth, in many cases yes. After growth, the teeth can be positioned so that they interlock correctly, while the jaw position itself remains. How far that goes depends on the severity.
The lower jaw is forced out of its natural position when biting because the teeth would otherwise not fit together. This strains the jaw joint and can steer jaw development in the wrong direction. A forced bite should be examined promptly.