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Conditions · Children, teens & adults
Crossbite: Front and Side Crossbites in Children and Adults
A crossbite is when some upper teeth bite inside the lower teeth instead of slightly outside them, at the front or the sides. Side crossbites often come from a narrow upper jaw and can make the jaw shift sideways. At Yonsei Baro near Isu Station, Dr. Sally Chaekyung Lee often recommends correcting them early.
Crossbite at a glance
| Question | In brief |
|---|---|
| What it is | Upper teeth sitting inside the lower teeth when biting: anterior (front) or posterior (side), on one or both sides |
| Common causes | A narrow upper jaw, a front tooth erupting behind the others, thumb sucking or mouth breathing, crowding, jaw growth differences |
| Usually noticed | Can appear in baby teeth; often spotted between ages 5 and 9 |
| How it’s assessed | Check for a sideways or forward jaw shift, digital scan, X-rays or 3D CT of jaw width and roots, growth analysis |
| Treatment options | Upper-jaw expansion, braces or clear aligners, appliances to correct a single tooth, combined surgical treatment for large adult jaw differences |
| Typical approach: children | Early correction is often advised, especially if the jaw shifts; expansion is easier while the upper jaw is still growing |
| Typical approach: adults | Braces or aligners for tooth-level crossbites; jaw-width problems may need anchorage-assisted or surgical expansion |
What are the types of crossbite?
Anterior crossbite
One or more upper front teeth sit behind the lower front teeth. When only one or two teeth are involved it is usually a tooth-position problem, and leaving it can wear the edges of the teeth or push a lower front tooth forward so its gum thins. When all the front teeth are involved, it may be an underbite .
Posterior crossbite
Upper back teeth sit inside the lower back teeth, usually because the upper jaw is narrow. When it affects one side only, the lower jaw often slides sideways as the teeth close so that they fit together.
Does my child need treatment now?
Crossbites are one of the clearer reasons for early orthodontic treatment. A posterior crossbite with a sideways jaw shift is commonly corrected in childhood, because a jaw that repeatedly shifts during growth may contribute to uneven development. See jaw asymmetry .
A narrow upper jaw is also easier to widen before the midline suture in the roof of the mouth matures. If thumb sucking or mouth breathing is involved, addressing it helps keep the correction stable. Our page on early orthodontic treatment explains the wider timing decision.
How is a crossbite corrected?
- Upper-jaw expansion: a fixed or removable expander gradually widens a narrow upper jaw in children
- Clear aligners for children: systems such as Invisalign First and Angel Aligner KiD can include some arch development in suitable mixed-dentition cases
- Braces or aligners: correct crossbites caused by tipped teeth in teens and adults
- Single-tooth correction: a small appliance or short phase of braces moves a front tooth over the bite
Can an adult crossbite be fixed?
Yes, often. Crossbites caused by tooth position respond well to braces or aligners. Once the upper jaw has matured, though, widening it is harder: options include expansion supported by temporary anchorage screws or, for large differences, surgically assisted expansion with an oral and maxillofacial surgeon. Dr. Lee will explain which applies after measuring the jaw width on CT.
How Dr. Lee assesses a crossbite
Dr. Lee first guides the jaw gently into its natural closing position to see whether it shifts. A digital scan shows how the teeth meet, and a RAY Quantum 5D CT scan shows the true width of the upper and lower jaws and how the back teeth are tipped, which separates a narrow jaw from tipped teeth. For children, growth analysis indicates how much expansion is still realistic. Published cases are on our before-and-after page ; results vary.
Crossbite FAQs
Will a crossbite correct itself as my child grows?
Occasionally a crossbite in baby teeth resolves when adult teeth arrive, but many don’t, especially those caused by a narrow upper jaw or a jaw that shifts sideways. Because these are easier to correct while the upper jaw is still growing, it is worth having a crossbite checked rather than waiting to see.
Does a palate expander hurt?
Most children feel pressure or tightness in the teeth and the roof of the mouth for a few days after each adjustment, and speech and eating feel different at first. A small gap may appear between the upper front teeth as the jaw widens; this is expected and usually closes. Discomfort tends to settle quickly.
Can a crossbite cause one side of the face to look different?
It can contribute. When a one-sided crossbite makes the lower jaw slide sideways every time a child bites, the chin can sit off-centre. If this continues during growth, it may affect how the jaw develops. Correcting the crossbite early removes the shift and usually re-centres the jaw.
Why does a front crossbite of one tooth matter?
A single upper front tooth caught behind the lower teeth can push the lower tooth forward, thinning the gum on the front of it, and the two teeth may wear against each other. These single-tooth crossbites are usually quick to correct when caught early, often with a small appliance or a short phase of braces.
Can clear aligners fix a crossbite?
Aligners can correct many crossbites caused by tipped teeth in teens and adults, and children’s aligner systems can develop the arch in some mixed-dentition cases. When the upper jaw is significantly narrow, a fixed expander is often more effective. See braces vs clear aligners for the general trade-offs.
Medically reviewed by Dr. Sally Chaekyung Lee, DDS, PhD
Board-certified orthodontist (Korea Ministry of Health and Welfare) · Adjunct Professor of Orthodontics, Yonsei University · Last updated October 2026
This page is general information, not a diagnosis. Treatment results and duration vary from person to person. Orthodontic treatment can cause temporary discomfort and, in some cases, root shortening, gum recession or tooth decay if oral hygiene is poor; teeth can relapse if retainers are not worn as instructed.
Spotted a crossbite?
Book an examination and Dr. Lee will check whether the jaw shifts and explain, in English, whether to treat now or monitor. Isu Station Exit 2 · Open until 9 PM Mon & Thu · Saturdays 9 AM–2 PM.