A crossbite is a type of misalignment where one or more upper teeth sit inside the lower teeth instead of slightly outside them. Normally, your upper teeth overlap your lower teeth just a bit when you bite down. When that relationship is reversed, even for a single tooth, it’s called a crossbite. It’s one of the more common orthodontic issues, affecting roughly 10% of children for the back teeth and about 6.5% for the front teeth.
Anterior vs. Posterior Crossbite
There are two main types, defined by where in your mouth the misalignment occurs.
A posterior crossbite affects the back teeth: your premolars and molars. Instead of your upper back teeth sitting slightly outside your lower ones when you bite together, they tuck inward. The teeth may look tilted toward your tongue. This is the more common form and can occur on one side (unilateral) or both sides (bilateral).
An anterior crossbite affects the front teeth. One or more upper front teeth sit behind the lower front teeth rather than in front of them. This can sometimes be confused with an underbite, but a true underbite involves the entire lower jaw protruding forward, while an anterior crossbite may involve just one or two teeth.
Within anterior crossbites, the cause matters for treatment. A dental crossbite means the teeth themselves are angled incorrectly, even though the jaw is fine. A skeletal crossbite means the upper or lower jaw is the wrong size or position, creating a concave facial profile with a prominent chin. There’s also a functional crossbite, where the jaw shifts forward during biting because of a premature contact between teeth, essentially “training” the bite into the wrong position.
What Causes a Crossbite
Genetics plays the biggest role. If your jaw bones grow at mismatched rates, or if your upper jaw is naturally narrower than it should be, a crossbite can develop regardless of habits or environment. But several childhood behaviors significantly raise the risk.
Thumb sucking, pacifier use, and prolonged bottle feeding all change the shape of the developing palate. The sucking motion pushes the tongue down and away from the roof of the mouth, while the cheek muscles press inward on the upper arch. Over time, this narrows the upper jaw. One study found that children with non-nutritive sucking habits had more than double the risk of posterior crossbite starting in their baby teeth. The duration matters: habits lasting 36 months or longer were specifically linked to posterior crossbite development, while pacifier use sustained for 24 to 47 months was associated with bite problems even if it stopped before permanent teeth came in.
Mouth breathing is another significant contributor. Children who breathe primarily through their mouths tend to develop a narrow upper jaw, a high arched palate, and a long facial shape. The connection is well established: mouth breathers show a higher prevalence of posterior crossbite, open bite, and other alignment issues compared to the general population. Not every child with these habits will develop a crossbite, though. The genetic growth pattern of the jaw determines susceptibility, so two children with the same habits can end up with very different bites.
How a Crossbite Affects Your Bite and Jaw
The most obvious sign is teeth that don’t line up properly. You might notice one tooth tucked behind another, or your back teeth may feel like they’re not meeting evenly when you chew. But the effects go well beyond appearance.
A crossbite forces your jaw to work asymmetrically. When you chew on the affected side, your jaw follows an abnormal pattern. In healthy people, only about 3% of chewing cycles move in a reversed direction. In people with a unilateral posterior crossbite chewing on the affected side, that number jumps to 60-71%. Your jaw essentially closes at the wrong angle, with less side-to-side movement and a narrower chewing path. This means less efficient grinding of food and more strain on one side of your jaw.
Over time, this asymmetric function compounds. The muscles on one side work harder, and the jaw joint (the TMJ) on the crossbite side can become compressed or repositioned. In growing children, the condyle, the rounded end of the jawbone that fits into the skull, can actually remodel into a more asymmetric position. This is why orthodontists consider crossbite a progressive condition: left alone, it tends to get worse rather than stabilize.
Long-Term Risks of Leaving It Untreated
A crossbite that isn’t corrected can lead to a cascade of problems. The teeth involved wear unevenly, and the enamel on those teeth breaks down faster than normal. Gums around the affected teeth may recede, and the teeth themselves can loosen over time. Cavities become more likely in areas where teeth meet abnormally, since food gets trapped in ways that are harder to clean.
The skeletal consequences are more serious, especially in children. A functional posterior crossbite causes the lower jaw to shift to one side to achieve a comfortable bite. The neuromuscular system adapts to this shifted position, and as the child grows, the bones follow the muscles. This can produce visible facial asymmetry, with the chin deviating toward the crossbite side. Once the skeleton has grown into that asymmetric pattern, correcting it becomes much more complex.
TMJ disorders are a well-documented consequence. The uneven forces on the jaw joints can cause clicking, pain, limited opening, and chronic headaches. The longer the crossbite persists, the more the joint structures remodel to accommodate the dysfunction.
Treatment Options by Age
Children and Adolescents
Early treatment is the standard approach because the bones are still growing and more responsive to correction. The palate has a natural suture running down its center that doesn’t fully fuse until the mid-teen years, making it possible to widen the upper jaw by physically separating the two halves of the palate.
Palatal expanders are the most common device for posterior crossbite in kids. They’re fixed to the upper back teeth and gradually widened, applying pressure that opens the midpalatal suture. The palate grows about as wide as it’s going to get between infancy and age 13, so treating before that window closes gets the best skeletal results with the least tooth tipping. A device called a quad-helix tends to work faster than removable expansion plates, finishing treatment about three months sooner on average, and at lower overall cost.
Clear aligners have emerged as an effective option for children in mixed dentition (a mix of baby and permanent teeth), particularly for anterior crossbites. In case studies, anterior crossbites in 8-year-olds were corrected within five months using aligners. They offer advantages over traditional appliances: easier hygiene, less discomfort, and more controlled expansion with less unwanted tooth tipping. For mild to moderate crossbites, aligners are now considered a viable first-line option in younger patients.
Teens and Adults
Traditional braces remain effective for crossbite correction at any age, though the approach shifts as the skeleton matures. In teens whose palatal suture hasn’t fully fused, expansion is still possible with orthodontic devices alone. In adults, the suture has typically closed, limiting how much the jaw can be widened without surgical assistance.
For adults with moderate to severe skeletal crossbites, surgically assisted rapid maxillary expansion (SARME) is a well-established procedure. A surgeon makes small cuts in the bone to release the fused suture, and an expander then gradually widens the jaw over the following weeks. For moderate cases, a one-stage approach can combine jaw expansion with other corrective jaw surgery. Severe skeletal crossbites in adults, particularly those involving a Class III jaw relationship, almost always require some form of surgical intervention alongside orthodontic treatment.
What Correction Feels Like
If you or your child gets a palatal expander, you’ll turn a small key or screw daily (or every few days, depending on the protocol) to widen it incrementally. Pressure across the roof of the mouth and behind the nose is normal for the first few minutes after each activation. Rapid expansion protocols finish faster than slow expansion, but both are successful at correcting the crossbite.
Braces or aligners for crossbite correction work like they do for any other orthodontic issue: periodic adjustments, mild soreness after each one, and a gradual shift in tooth position over months. The total timeline varies widely depending on severity, but posterior crossbite correction with a quad-helix averages several months shorter than with a removable plate.
After active treatment, retention is important. Chewing patterns that developed during the crossbite don’t always self-correct immediately, even after the teeth are in the right position. Some studies have found that abnormal chewing patterns improve significantly after crossbite correction but may not fully normalize right away, which is one reason orthodontists recommend a period of functional monitoring after the bite is fixed.