Crossbite: Understanding and Treating This Common Issue

Crossbite and facial asymmetry
Have you ever heard of a crossbite? It's a common dental issue that can affect both children and adults.

Crossbite can occur in any area of the mouth (front or back) and may impact only the teeth' alignment or involve the growth of the jaws as well.

What makes it particularly challenging is that it doesn't resolve on its own. It can even worsen over time, affecting the overall facial development. That's why early treatment is crucial.

What is a Crossbite?

In a normal bite, your upper jaw should slightly overlap the lower jaw, with the chewing surfaces of your bottom teeth fully hidden behind the upper teeth when you bite down.
normal bite
However, in a crossbite, the opposite occurs – it's the lower teeth that overlap the upper ones.
Dental crossbite: The lower molars overlapping the upper ones
Now, you might think it's not a big deal, but this misalignment goes against how your jaws are supposed to work together. Over time, it can cause problems not only with your teeth but also with the joints and muscles involved in chewing.

There are different types of crossbites, depending on the specific teeth involved and the origin of the issue. Let's break it down:

  • Anterior Crossbite: This type of crossbite affects the front teeth. It means that your lower front teeth are positioned in front of the upper front teeth when you bite down.
  • Posterior Crossbite: When the crossbite is limited to the back teeth, specifically the molars and premolars, it's called a posterior crossbite. In this case, your lower teeth may be positioned on the outer side of your upper teeth when you bite.

Crossbites can also be categorized based on the involvement of one side or both sides of the mouth:

  • Unilateral Crossbite: If the crossbite affects only one side of your mouth, either the right or left, it's called a unilateral crossbite.
  • Bilateral Crossbite: When the crossbite affects both sides of your mouth, it's known as a bilateral crossbite.
  • Unilateral vs. Bilateral crossbite

The origin of a crossbite can vary as well. It may be due to:

  • Dental Misalignment (Dental Crossbite): In this case, the crossbite is solely related to the position of your teeth. Your jaws have developed normally, but the teeth don't align properly.
  • Skeletal Issues (Skeletal Crossbite): A skeletal crossbite involves the growth of your jaws. Either they haven't developed properly or have grown asymmetrically.
  • Combination of Dental and Skeletal Factors: Sometimes, a crossbite occurs due to a combination of both tooth misalignment and jaw growth issues.

Dental Crossbite: Alignment Issues

In a dental crossbite, your jaws have developed normally, but the problem lies in the misalignment of your teeth (1).

They may be tilted in the wrong direction, causing the upper and lower teeth to meet incorrectly. Typically, dental crossbite occurs on one side of your mouth when you bite down.
dental crossbite
Also, as the lower jaw seeks contact points through the teeth to stabilize itself, it may deviate to one side. This can lead to facial asymmetry.

Facial asymmetry: Lower jaw deviated to one side

The good news is that dental crossbite is usually a minor issue and can be easily treated when diagnosed early. However, if left untreated, what starts as a simple dental misalignment can progress and impact normal growth, potentially transforming into a skeletal problem (2).

Signs of dental crossbite:

  • Unilateral Crossbite: Dental crossbite often manifests on one side of your mouth when biting down.
  • Deviation of the Lower Jaw: When closing your mouth, you may notice that your lower jaw deviates to the affected side of the crossbite.
  • Teeth Angled Inward: The upper teeth may be tilted inward toward the inside of your mouth.

Skeletal Crossbite: Jaw Development Issues

Unlike dental crossbite, skeletal crossbite involves more than just misaligned teeth. It's a condition where the jaws have become too narrow or asymmetrical (1).

Skeletal crossbite is typically a more severe condition that often affects the alignment of teeth on both sides (bilateral crossbite).
skeletal crossbite
The most common cause of skeletal crossbite is a narrow upper jaw that hasn't grown sufficiently in width. As a result, the palate (the roof of the mouth), becomes narrow and takes on a triangular shape.
Narrow palate
In rarer cases, skeletal crossbite can be caused by a malformation of the lower jaw (the mandible). The mandible may have developed excessively on one side or grown asymmetrically, leading to a unilateral crossbite on that side.

Severe forms of skeletal crossbite often require more advanced treatment, which may include surgical intervention to correct the jaw position and alignment.

Signs of skeletal crossbite:

  • Narrow Upper Jaw: The upper jaw may appear too narrow, impacting the alignment of your teeth.

  • Triangular-Shaped Palate: The roof of your mouth may have a narrow, "V" shape due to skeletal issues.

  • Bilateral Crossbite: Skeletal crossbite commonly affects both sides of the mouth when biting down.

  • Facial Features: In some cases, skeletal crossbite can impact facial features due to jaw abnormalities.

  • Bad Habits: Skeletal crossbite is often associated with habits like thumb sucking or mouth breathing.
  • What causes a crossbite?

    Crossbite results from the interaction of multiple factors, including genetics, abnormal oral functions, and certain habits. Let's explore these factors in more detail:

    1. Genetics:


    Genetic factors play a role in facial development and the growth and positioning of the jaws. Certain syndromes and anomalies can affect jaw growth, making skeletal crossbites more likely (3). It's not uncommon for individuals with crossbites to have parents who also experienced similar issues. Some common genetic situations associated with crossbite include:

    • Maxillary Hypoplasia: Insufficient growth of the upper jaw.
    • Mandibular Hyperplasia: Excessive growth of the lower jaw.
    • Laterognathia: Asymmetry of the jaw, where one side is larger or positioned differently than the other.

    2. Functional Issues and Bad Habits:

    A child sucking his thumb

    Abnormal oral functions and certain habits can significantly contribute to the development of crossbite. If left unaddressed, they can impact facial growth and cause skeletal malocclusion. Oral function abnormalities and habits associated with crossbite include:

    • Mouth Breathing: Breathing predominantly through the mouth instead of the nose forces the tongue into a low position. Besides the dental alignment issue, this can alter facial growth patterns and head posture and cause other health problems.

    • Tongue Thrusting: Habitually pushing the tongue against or between the teeth during swallowing can disrupt the proper alignment of the teeth. In addition to the crossbite, this can lead to a gap between the upper and lower front teeth when the mouth is closed. This malocclusion is called an open bite.

    • Thumb Sucking: This is a normal and vital function for newborns. However, prolonged thumb sucking after five years of age can affect the growth and alignment of jaws and teeth.

    Why are oral functions so important in jaw development and dental alignment?

    While genetics play a role in facial development and jaw growth, it is primarily abnormal oral function and bad habits that contribute significantly to malocclusion (3). This is particularly the case for posterior crossbite, which is more common in children (7%-23%) (4).

    Initially, these functional problems impact tooth alignment. However, if left unaddressed, they can disrupt facial growth and result in deformities of the jawbone (7). Let's delve into why this happens.

    During growth, facial bones are connected by sutures, which provide growth potential until puberty. Normal functions (such as chewing, nasal breathing, and swallowing) exert tension on these sutures, stimulating growth and facilitating proper jaw development and tooth alignment.
    palatal suture
    However, persistent abnormal oral functions, such as mouth breathing, can deprive the sutures of adequate stimulation, resulting in facial deformities.

    Furthermore, balanced muscle activity is vital for maintaining proper tooth alignment. When muscles, including the cheeks and tongue muscles, exert uneven pressure on the teeth, it can cause them to shift.

    For example, if the cheek muscles work harder than the tongue muscles, the teeth may gradually tilt inward.

    Therefore, the rehabilitation and restoration of normal oral function are essential aspects of treatment.

    By addressing these functional issues early on, we can prevent the development of long-term skeletal problems that often require complex, long treatment.

    Why early treatment is crucial?

    Treating a crossbite as soon as possible is crucial for several reasons. Here's why:

    • Limited self-correction: Crossbites are unlikely to correct themselves over time. In fact, without intervention, crossbites can worsen and negatively impact jaw growth.

    • Early treatment is especially critical for skeletal crossbite. During growth, the width of the jaws is the first aspect to complete its development. By addressing the crossbite early, we can leverage the growth potential and facilitate easier and faster treatment.
      Delayed treatment may require surgical intervention to correct bone deformities, as growth potential diminishes with age.

    • Preventing additional problems: Untreated crossbites can contribute to various muscular, joint, and dental issues. These include:
      • Temporomandibular joint pain
      • Jaw asymmetry
      • Less efficient chewing
      • Muscle dysfunction
      • Tooth wear

    Treating Crossbite: Options for Children and Adults:

    Crossbite, like any dental malalignment issue, should be treated as early as possible, especially in childhood. The remaining growth potential allows for faster and more efficient treatment. There are several approaches available to fix a crossbite, including:

    In Children:

    Treating crossbite in children offers advantages due to their ongoing growth potential. The following treatment options are commonly employed:

    1. Palatal Expansion:

    This technique involves using orthodontic devices (such as a rapid palate expander) to expand the upper jaw, creating space for proper teeth alignment. This will also help to position the lower jaw correctly, thus preventing muscular and joint problems later on.

    2. Rehabilitation of Oral Functions and Elimination of Bad Habits:

    An essential step in treatment is rehabilitation and replacing harmful habits with healthier ones. This will help stop the condition from progressing, create favorable conditions for facial growth, and prevent recurrence after treatment. Two primary approaches are used:

    • Myofunctional Therapy: Children actively participate in exercises that target breathing, swallowing, phonation, and other functions to develop new, beneficial habits for proper growth.

    • Rehabilitation with Orthodontic Devices: Orthodontic devices, such as tongue cribs, tongue spurs, or orthodontic trainers, are utilized to rehabilitate oral function without conscious participation from the child.

    In Adults:

    Treatment for crossbite in adults may vary depending on the severity and whether it is primarily dental or skeletal in nature.

    1. Fixing Dental Crossbite in Adults:

    Dental crossbite treatment is relatively simple as it involves only teeth misalignment. It can be addressed using orthodontic appliances such as braces, clear aligners, or palate expanders. Within a few to several months, these can modify tooth positions and establish a healthier bite.

    2. Fixing Skeletal Crossbite in Adults:

    Treating skeletal crossbite in adults is more complex as growth has already been completed. Treatment options depend on the severity of the condition:

    • Minor Cases: Minor skeletal crossbites can sometimes be corrected with orthodontic appliances to restore a normal bite. The idea is to address the misalignment of the jaws by adjusting the teeth's positions.

    • Severe Cases: If the crossbite is associated with severe jaw deformity, corrective surgery may be necessary. However, some studies have shown that palatal expansion can still be an effective option for adults.
      By reactivating the palatal suture, it may be possible to achieve jaw correction without the need for surgery. However, this approach is not suitable for everyone and carries potential risks and complications.
      Therefore, a thorough examination and consultation with an orthodontist is necessary to determine the appropriate treatment course.