A crossbite is a common form of dental misalignment where one or more of a child’s upper teeth fit incorrectly inside the lower teeth when the jaw closes. This contrasts with a typical bite, where the upper arch sits slightly outside the lower arch. Correction of this misalignment is often time-sensitive, as the early development of the jaw and teeth provides a unique opportunity for effective intervention. Understanding a crossbite is the first step toward achieving a healthy, functional bite for the child.
Defining and Identifying Crossbites
A crossbite is categorized based on the location of the misalignment. An anterior crossbite occurs in the front of the mouth, where one or more upper front teeth bite behind the lower front teeth, similar to a partial underbite. A posterior crossbite affects the back teeth, where the upper back molars sit inside the lower back molars. This posterior type may be unilateral, affecting only one side of the jaw, or bilateral, affecting both sides simultaneously.
Parents can look for specific visual cues that suggest a crossbite is present. Uneven tooth wear is a common sign, as the misalignment causes specific teeth to bear excessive force during chewing. A recognizable sign, particularly with a unilateral posterior crossbite, is a functional shift in the jaw. This shift means the child must move their lower jaw to one side to fully close their mouth, which causes the lower jaw line to visibly deviate when biting down.
Importance of Early Intervention
Addressing a crossbite promptly during childhood is important because the bones of the face and jaw are still developing and responsive to orthopedic correction. An untreated crossbite can impact the natural growth trajectory of the jawbones, potentially leading to permanent facial asymmetry over time. The persistent shift in the lower jaw to achieve a comfortable bite also places unnatural strain on the temporomandibular joint (TMJ) complex. This strain often resolves after the crossbite is corrected.
The teeth themselves suffer from the incorrect bite relationship. Excessive force on misaligned teeth can cause premature wear on the enamel, increasing the risk of chipping or sensitivity. The misalignment may also affect a child’s ability to articulate certain sounds, potentially leading to minor speech issues. Early correction, often termed Phase I or interceptive orthodontics, capitalizes on the malleability of the young patient’s jaw to modify growth and prevent these long-term complications.
Treatment Options Based on Age
The approach to fixing a crossbite depends on the child’s age and whether they are in the primary (baby teeth) or mixed (a mix of baby and permanent teeth) dentition stage. Treatment during Phase I (typically ages 7-10) focuses on orthopedic correction, meaning correcting the jaw structure rather than just moving teeth. This early intervention capitalizes on the malleability of the young patient’s jaw to modify growth. The most common tool for a posterior crossbite is the Rapid Palatal Expander (RPE).
The RPE is a fixed appliance cemented to the upper back teeth, featuring a small screw mechanism in the center of the palate. Parents are instructed to turn a key daily, which applies gentle pressure to the two halves of the upper jaw. This action causes the mid-palatal suture to separate and widen the maxilla. Each turn typically expands the arch by about a quarter of a millimeter. The active expansion phase usually lasts only a few weeks, and the appliance remains in place for several months afterward to allow new bone to solidify the achieved expansion.
Anterior Crossbite Treatment
For an anterior crossbite, treatment involves moving the misaligned upper incisor forward to sit in front of the lower teeth. This can often be achieved with a simple removable appliance, such as a clear plastic retainer with a spring component. Limited fixed braces on just the front teeth may also be used. Active treatment with these appliances is generally shorter than with an RPE, sometimes lasting only 3 to 6 months.
Adolescent Treatment
If a crossbite is not addressed during the growth phase or requires more comprehensive dental alignment, treatment shifts to adolescence when all permanent teeth have erupted. At this stage, full fixed braces are typically used to correct the dental misalignment. In rare instances of severe skeletal discrepancy that persists into late adolescence, correction may involve a combination of orthodontics and corrective jaw surgery.
Post-Treatment Care and Retention
Following the active phase of crossbite correction, the teeth and jaw must be stabilized to prevent the corrected alignment from shifting back, a phenomenon known as relapse. This stabilization period, or retention, is the final stage of treatment. The orthodontist will prescribe a retainer, a device designed to hold the teeth in their newly established position.
Retainers come in two forms: fixed and removable. A fixed retainer is a thin wire bonded to the tongue-side surface of the front teeth, offering continuous retention. Removable retainers, such as the clear aligner-style or the Hawley appliance, are worn full-time initially, then typically only at night. Consistent wear, especially during the first year of retention, is necessary to maintain the long-term stability of the corrected bite. Children require long-term monitoring to ensure the corrected bite remains stable as their jaw continues to mature.