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A crossbite is a form of malocclusion (misalignment) that occurs when the upper and lower teeth do not align correctly. This type of malocclusion means some bottom teeth are located outside the upper teeth when the two jaws are closed.
In other words, some upper teeth are positioned inside the lower teeth. The misalignment can either appear at the front of the mouth (anterior) or the sides of the mouth (posterior).
A crossbite is often confused with an underbite, but it is an entirely different malocclusion and requires different treatment.
In a crossbite, the tooth or teeth are slightly forward, but not the entire jaw. An underbite is when the lower teeth and jaw are in front of the front teeth and jaw. Genetic factors usually cause an underbite. It is also more severe than a crossbite.
There are two different types of crossbites, including:
An anterior crossbite is a lingual occlusion of the upper anterior teeth (incisors and canines) with the lower anterior teeth. In this type of malocclusion, some or all of the upper anterior teeth are behind the lower anterior teeth. In some cases, the lower front teeth completely hide the upper front teeth.
A posterior crossbite is the opposite of an anterior crossbite. In this type of malocclusion, the top back teeth sit inside the bottom back teeth.
Between 8 and 16 percent of children have a posterior crossbite.
Posterior misalignment is due to the irregular narrowing of the palate and teeth in the upper jaw. Posterior crossbites can either develop on one side or both sides of the mouth.
The cause of a crossbite can be contributed to genetic factors, abnormal tooth eruption, breathing through the mouth long-term (especially during sleep), and childhood habits (e.g. thumb sucking).
The primary cause of a crossbite is due to genetics. Some people are born with a larger lower jaw and smaller upper jaw. Since narrow palates and teeth can run in the family, it may result in a crossbite once teeth begin to grow in. If this is the case, an orthodontist may recommend a growth modification device. The device widens a baby’s upper jaw early on to prepare for orthodontic treatment once his or her permanent teeth start to grow in.
Mouth breathing can alter facial growth. Breathing through the mouth typically happens during sleep. If a child already has a small upper jaw and mouth breathes, they have an even higher chance of developing a crossbite.
Over-retained teeth refer to baby teeth that have loosened but then tighten back into the gums, preventing the eruption of permanent teeth. If this occurs in the upper jaw, the tooth should be extracted to prevent a crossbite with the tooth or teeth in the lower jaw. If the permanent tooth erupts and causes a crossbite, orthodontic treatment is necessary to move the tooth into its correct position.
Common risk factors associated with untreated crossbites include:
Yes. If left untreated, a crossbite can cause jaw issues. More specifically, temporomandibular joint dysfunction (TMJ), a disorder that causes dysfunction and pain in the jaw and surrounding muscles that control jaw movement, can form over time.
If a crossbite is not corrected in early childhood, it is more likely that other dental conditions and jaw issues will develop in adulthood. Treatment is still possible for adults, but choices are limited since the jaw and teeth have fully developed.
Clear aligners have become a common orthodontic treatment for crossbites. Invisalign is the most effective, safe, and well-known brand of clear aligners. In short, aligners cover the entire biting surfaces of the upper and lower teeth, which allows a tooth in a crossbite to move freely without being affected by the opposing teeth.
Crossbites are relatively common, and braces are capable of treating most cases. For example, if only a single tooth is in a crossbite, braces can effectively move the tooth into its correct position without help from additional orthodontic appliances.
If more than one tooth is in a crossbite, a dental expansion appliance or headgear may be used in conjunction with braces.
For more severe crossbites, an orthodontist may recommend a dental expansion procedure in combination with braces or clear aligners. For example, Rapid Palatal Expanders (RPE) expand narrow dental arches and correct posterior crossbites. The appliance fits over some back teeth in the upper jaw and a screw connects the device in the middle. To activate RPEs, you turn the screw a small amount every day.
Reverse pull headgear consists of pads that attach to the forehead and chin with a facemask frame in between. Patients connect rubber bands from the anchorage device on the braces to the frame. Reverse pull headgear shifts the upper jaw forward to align the teeth in the upper and lower jaws over time.
In the most severe cases, jaw (orthognathic) surgery is used to treat underbites, overbites, crossbites, and advanced sleep apnea. During the procedure, an oral surgeon strategically moves the upper and lower jaws forward.
Jaw surgery costs anywhere between $20,000 and $50,000.
Veneers are capable of fixing mild crossbites in adults only. If you have a stable bite and are looking to change the shape and color of your teeth, veneers might be an option. However, veneers are more expensive and invasive than orthodontic treatment. Speak with your dentist or orthodontist to determine the best option.
Almeida, Renato Rodrigues De, et al. “Posterior Crossbite - Treatment and Stability.” Journal of Applied Oral Science, vol. 20, no. 2, 2012, pp. 286–294., doi:10.1590/s1678-77572012000200026. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3894776/
Piancino, Maria Grazia, and Stephanos Kyrkanides. Understanding Masticatory Function in Unilateral Crossbites. Wiley Blackwell, 2016.
Proffit, William R., et al. Contemporary Orthodontics. Elsevier/Mosby, 2019.
Recognizing and Correcting Developing Malocclusions: a Problem-Oriented Approaches to Orthodontics. Wiley, 2015.
Sterling, Evelina Weidman. Your Childs Teeth: a Complete Guide for Parents. Johns Hopkins University Press, 2013.