If your child's dentist has mentioned the word "crossbite," you might be wondering what it means and whether it is something to worry about. In my years of practice, I have found that crossbites are one of the most underrecognized bite problems in children. Parents often do not notice anything wrong because the teeth might look reasonably straight from the front. But a crossbite can quietly cause significant issues with jaw growth, tooth wear, and facial symmetry if it is not addressed.
What Is a Crossbite
A crossbite is a misalignment where one or more of the upper teeth sit inside the lower teeth rather than outside, which is the normal relationship. Think of the upper teeth as a lid on a box. Normally, the lid (upper teeth) fits just outside the box (lower teeth). In a crossbite, part of that lid tucks inside the box instead.
There are two main types. An anterior crossbite involves the front teeth, where one or more upper front teeth sit behind the lower front teeth. A posterior crossbite involves the back teeth, where the upper back teeth (premolars or molars) sit inside the lower back teeth on one or both sides.
Posterior crossbites are especially common in children and are the type I most frequently treat with early intervention. They can affect one side of the mouth (unilateral) or both sides (bilateral), and they often go unnoticed until a dental professional spots them during a routine exam.
Why Crossbites Develop
Crossbites develop for several reasons. The most common cause is a narrow upper jaw. The upper jaw, or maxilla, is supposed to be slightly wider than the lower jaw so that the upper teeth overlap the lower teeth on the outside. When the upper jaw does not grow wide enough, some or all of the upper teeth end up sitting inside the lower teeth.
Genetics play a major role. If a parent had a narrow palate or a crossbite, their child is more likely to develop one too. Habits like prolonged thumb sucking or pacifier use can also contribute by narrowing the palate over time. Mouth breathing, often caused by allergies, enlarged tonsils, or adenoids, changes the resting posture of the tongue and can restrict the normal widening of the upper jaw during growth.
Occasionally, a crossbite is caused by individual teeth that simply erupted in the wrong direction rather than a true skeletal mismatch. These dental crossbites are generally simpler to treat than skeletal ones.
What Happens If a Crossbite Is Not Corrected
This is where crossbites become a bigger deal than many people realize. If a crossbite is not corrected, the consequences can compound over time.
One of the most concerning outcomes is asymmetric jaw growth. When a child has a posterior crossbite, especially a unilateral one, they often shift their lower jaw to one side when closing their mouth. This functional shift, repeated thousands of times a day during chewing and swallowing, can eventually lead to permanent asymmetry in the jaw and face. I have seen teenagers whose faces had noticeable asymmetry because a crossbite was never addressed during childhood. By that point, what started as a simple skeletal mismatch had become a more complex problem requiring significantly more treatment.
Tooth wear is another consequence. When teeth are meeting in abnormal positions, the enamel wears unevenly. This uneven wear can lead to sensitivity, increased risk of cavities, and even fractures of the tooth structure over time.
Crossbites can also contribute to jaw joint problems. The shifted jaw position puts uneven stress on the temporomandibular joints (TMJs), which can cause pain, clicking, or limited range of motion. While TMJ issues are more common in adults, the foundation for those problems is often laid during childhood.
Gum recession around the affected teeth is another risk. When a tooth is sitting in a crossbite position, the forces it receives during chewing are directed in an abnormal way, which can push the tooth through the thin bone on the outer or inner side of the jaw. This can lead to gum tissue loss that is difficult to reverse.
Why Early Treatment Makes a Difference
Crossbites are one of the conditions where the orthodontic community is in strong agreement that early treatment is beneficial. The American Association of Orthodontists recommends that children have their first evaluation by age seven, and crossbites are a primary reason for that recommendation.
In a growing child, we can take advantage of the fact that the upper jaw (maxilla) is actually two separate bones joined by a suture in the middle. Until this suture fuses, which typically happens in the mid-teenage years, we can use a palatal expander to widen the upper jaw. The expander applies gentle, controlled pressure to gradually separate the two halves of the palate, creating more room for the teeth and correcting the crossbite.
I have placed hundreds of expanders over the years, and the process is remarkably straightforward. The appliance is cemented to the upper back teeth, and the parent turns a small screw in the middle of the device once or twice a day as instructed. Most children tolerate it very well. There is some initial pressure, and speaking may feel a little different for the first few days, but kids adapt quickly. Parents sometimes notice a small gap developing between the upper front teeth during expansion. This is actually a sign that the expander is working as intended, and the gap closes on its own or with subsequent orthodontic treatment.
The reason early correction is so much simpler than waiting is that the suture has not yet fused. Once a patient reaches their mid-to-late teens or adulthood, the palatal suture becomes increasingly resistant to expansion. Adult crossbite correction may require surgical assistance to separate the suture, which is a much more involved procedure called surgically assisted rapid palatal expansion (SARPE). While effective, it is obviously preferable to avoid surgery when a simpler option was available earlier.
What Treatment Involves
For most children with a posterior crossbite, treatment involves wearing a palatal expander for about three to six months. After the desired expansion is achieved, the expander is typically left in place for a few additional months to allow new bone to fill in the expanded suture and stabilize the correction.
For anterior crossbites involving just one or two teeth, treatment might be simpler. Sometimes a limited phase of braces on the front teeth, or even a removable appliance, can tip the affected teeth into the correct position within a few months.
After crossbite correction in childhood, many patients will still benefit from comprehensive orthodontic treatment later, usually with full braces or aligners in their early teens, to address the overall alignment and bite. But the early intervention has already solved the most time-sensitive problem and prevented the downstream complications that would have made later treatment more difficult.
If your child has been diagnosed with a crossbite, or if their dentist has recommended an orthodontic evaluation, I would encourage you to schedule that appointment. Crossbites do not self-correct, and the earlier they are addressed, the simpler and more predictable the treatment tends to be. It is one of those situations where a small investment of time early on can save a great deal of trouble later.
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