dental instruments and oral health

What is a Crossbite?

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:

Anterior Crossbite

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.

Posterior Crossbite

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. 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 prevalence of posterior crossbites in children ranges between 8 and 16 percent.”


What Causes a Crossbite?

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).

Genetics

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

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.

Delayed Eruption of Permanent Teeth

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.

Childhood Habits

Sucking habits can alter jaw growth in children. These habits include, but are not limited to, thumb sucking, finger sucking, poor chewing habits, and using a bottle or pacifier excessively.

Risk Factors & Complications of Untreated Crossbites

Common risk factors associated with untreated crossbites include:

  • Tooth chips or cracks caused by abnormal occlusion between the upper and lower teeth.
  • Increased risk for cavities and gum disease, such as gingivitis and periodontal disease.
  • Receding gums, which is a serious oral condition that exposes tooth roots to infection and decay due to improper tooth position, malocclusion, and periodontal disease.
  • Temporomandibular joint dysfunction (TMD), which is a disorder that causes dysfunction and pain in the jaw and surrounding muscles that control jaw movement.

Treatment Options for Crossbites

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

Clear aligners have become a common orthodontic treatment for crossbites. 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.

Braces

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.

On the other hand, if more than one tooth is in a crossbite, a dental expansion appliance or headgear may be used in conjunction with braces:

Rapid Palatal Expander (RPE)

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.

In essence, the goal is to widen the upper jaw, expand the dental arch, and move the misaligned teeth into their correct positions.

Reverse-Pull Headgear (Facemask)

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.

Jaw Surgery

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. The procedure costs anywhere between $20,000 and $50,000.