A crossbite is a common dental misalignment where one or more of the upper teeth fit inside the lower teeth when a child closes their jaw. This reversed biting relationship affects proper oral function and jaw growth. Addressing this issue early is important for ensuring the correct development of the teeth and supporting facial structures.
Identifying and Classifying Crossbites
Parents and dentists can spot a crossbite by observing how the upper and lower teeth meet during biting. In a normal bite, the upper teeth should slightly overlap and sit outside the lower teeth; a crossbite is characterized by the opposite occurring in one or more areas of the mouth.
Crossbites are generally categorized based on where the misalignment occurs in the dental arch. An anterior crossbite involves the front teeth, where one or more upper incisors bite behind the lower incisors, often resembling an underbite. A posterior crossbite affects the back teeth, causing the upper molars or premolars to tuck inside the lower back teeth when the jaws close.
The origin of the problem further classifies the crossbite as either dental or skeletal. A dental crossbite means the teeth are positioned incorrectly, while the jaws are appropriately sized and aligned. A skeletal crossbite results from a mismatch in the size or position of the upper jaw (maxilla) and the lower jaw (mandible), such as a maxilla that is too narrow for the mandible.
Why Early Treatment is Critical
An untreated crossbite can guide the child’s jaw growth incorrectly, leading to long-term functional and aesthetic issues. The misalignment often causes the lower jaw to shift to one side when biting, which may result in asymmetrical facial development over time. This functional shift places stress on the temporomandibular joint (TMJ), potentially leading to chronic jaw pain and joint disorders.
The abnormal contact between the teeth also results in uneven pressure distribution during chewing. This can lead to excessive and premature wear, chipping, or fracturing of specific teeth. Furthermore, the misaligned bite can contribute to gum recession and bone loss around the affected teeth due to improper forces.
Orthodontists recommend an initial evaluation around age seven, which is the optimal period for interceptive orthodontics or Phase I treatment. At this age, the child has a mix of baby and permanent teeth, and the jawbones are still actively growing and malleable. Addressing skeletal issues, such as a narrow upper jaw, is significantly easier and less invasive while the child is still growing than waiting until the jawbones have fused.
Early intervention capitalizes on this growth to correct structural problems, reducing the need for complicated procedures later in life. Fixing the crossbite early also stabilizes the bite, allowing the permanent teeth to erupt into a more favorable environment. The goal is to establish a correct foundation for the entire dental and facial structure.
Treatment Options for Children
The primary approach for correcting a posterior crossbite in a growing child involves widening the upper jaw. Common devices used are palatal expanders, such as a Rapid Palatal Expander (RPE) or a Quad-Helix appliance. An RPE is a fixed device cemented to the back teeth, featuring a screw mechanism turned daily by the parent for a few weeks.
This controlled pressure gently separates the two halves of the upper jaw at the midpalatal suture, which is not yet fused in children. The Quad-Helix is a fixed appliance that uses spring tension for a similar widening effect. Both devices effectively eliminate the skeletal discrepancy, allowing the upper back teeth to sit outside the lower teeth.
For anterior crossbites, treatment depends on whether the issue is dental or skeletal. A simple dental crossbite involving one or two teeth may be corrected with a removable appliance featuring a small spring to push the tooth forward. Another option is a 2×4 appliance, which is a type of partial fixed braces applied to the four upper front teeth and the two upper back molars.
If the anterior crossbite is skeletal, indicating a deficient upper jaw, the orthodontist may use appliances to encourage forward growth of the maxilla. This might involve a specialized fixed or removable appliance, sometimes combined with elastics or a face mask worn outside the mouth to move the upper jaw forward. The active treatment phase for crossbite correction can range from a few weeks to several months, depending on the severity.
Retention and Follow-up Care
Once the active correction of the crossbite is complete, retention begins to ensure the stability of the result. The expanded jaw or repositioned teeth need time for the surrounding bone and tissues to solidify in their new location. For posterior crossbites corrected with an RPE, the expander is often left in place, inactivated, for an additional three to six months to serve as a fixed retainer.
Following the fixed retention period, a removable retainer may be prescribed, typically worn primarily at night. The total retention period after maxillary expansion often averages six to nine months, though this varies based on the child’s needs. The goal of retention is to minimize the risk of relapse, preventing the teeth or jaw from drifting back toward their original misalignment.
Monitoring must continue even after the initial retention phase, especially as the rest of the permanent teeth erupt. Children are followed periodically by the orthodontist to ensure the corrected bite is stable and the jaw relationship remains balanced throughout the transition to the permanent dentition. This ongoing surveillance helps determine if a second, comprehensive phase of orthodontics will be necessary later, usually with full braces, to align all the permanent teeth.