Crossbite: when the teeth meet the wrong way around
A malocclusion that forces the jaw joint – and one that should rarely wait until the teeth change over.
Normally the upper back teeth close over the outside of the lower ones, like a lid over a pot. In a crossbite this is reversed in one or more places: the lower teeth bite past the outside of the upper ones.
The most common cause
An upper jaw that is too narrow. It can be hereditary or have developed that way – for instance with constant mouth breathing, when the tongue does not rest against the palate and therefore does not shape it from the inside. Enlarged adenoids are a common background here.
Why one does not wait
If the teeth do not interlock properly, the lower jaw shifts to the side when biting down – a forced bite. This puts one-sided strain on the jaw joint and can, over time, make facial development asymmetrical. Alongside the underbite, the crossbite is therefore the malocclusion for which early treatment is frequently indicated.
The treatment
The upper jaw is widened. In children this is done via the palatal suture, which has not yet ossified: an appliance with a screw stretches it in small steps, and the bone fills in the gap. After puberty the suture has fused – then either surgically assisted expansion or a different approach is needed.
The key facts at a glance
- In a crossbite, lower teeth bite past the outside of the upper ones – at individual teeth or along entire sides.
- The cause is usually an upper jaw that is too narrow, often connected with constant mouth breathing.
- The lower jaw shifts to the side when biting down. This strains the jaw joint and can lead to asymmetrical facial development.
- As long as the palatal suture is open, the upper jaw can be widened without surgery. After puberty it becomes more involved.
Answered briefly
Frequently asked questions
As a rule yes, and promptly. It does not grow out, and the longer the lower jaw deviates when biting, the more it shapes the development of the joint and the face.
A fixed appliance is anchored to the upper molars. A screw in the middle is turned a little each day and stretches the palatal suture. The resulting gap fills with bone. The active phase lasts a few weeks, after which the appliance stays in place for a few more months for stabilisation.
When the screw is turned you feel pressure behind the nose, and sometimes the teeth briefly feel wobbly. Pain in the true sense is rare. A gap between the upper incisors is intended and closes again by itself.
Yes, but differently. The palatal suture has fused; expansion then requires surgical support. If individual teeth are in crossbite, an ordinary orthodontic correction is often enough.