A crossbite is a type of dental misalignment, or malocclusion, where one or more upper teeth fit inside the lower teeth when the jaws are closed. In a normal bite, the upper teeth slightly overlap the lower teeth all the way around the arch. The condition is classified by its location. An anterior crossbite affects the front teeth, where upper incisors sit behind the lower front teeth, sometimes called an underbite. A posterior crossbite involves the back teeth, where the upper molars and premolars bite inside the lower teeth. Crossbites can be unilateral, affecting one side, or bilateral, affecting both sides.
Consequences of Untreated Crossbites
Ignoring a crossbite can lead to functional and structural issues. The improper alignment causes uneven forces when chewing, leading to excessive wear on certain teeth. This uneven pressure can result in chipped enamel, flattened cusps, and increased tooth sensitivity.
A crossbite can also cause trauma to the soft tissues of the mouth. The misaligned bite can push lower teeth into the opposing gum line, potentially causing gum recession and a higher risk of periodontal disease. In growing patients, a persistent crossbite may force the lower jaw to shift to one side when biting, leading to asymmetrical jaw growth and facial features.
The chronic strain from a misaligned bite pattern can affect the jaw joints. Tension on the temporomandibular joint (TMJ) can result in jaw pain, clicking or popping sounds, and the development of temporomandibular disorders.
Correction Methods for Growing Patients
The most effective treatment for crossbites in children and adolescents, typically ages six to ten, is interceptive orthodontics. This Phase I treatment capitalizes on the patient’s remaining growth potential to correct the underlying skeletal discrepancy, often a narrow upper jaw. A Rapid Palatal Expander (RPE) is a commonly used fixed appliance cemented to the back upper teeth.
The RPE applies gentle, continuous pressure to the mid-palatal suture, the growth plate separating the two halves of the upper jaw. Parents or patients turn a central screw on the appliance daily, causing expansion with each turn. This rapid expansion takes a few weeks, and the appliance is then kept in place for several months to allow new bone to fill in the widened space.
For cases requiring mild to moderate expansion, a Quad Helix appliance may be used. This fixed device uses four coiled springs to apply outward pressure to the upper molars and dental arch. Unlike the RPE, the Quad Helix is pre-loaded by the orthodontist and does not require daily manual activation, providing a slower, gentle expansion over about six months.
Comprehensive Orthodontic Correction for Adults
In older adolescents and adults whose skeletal growth is complete, correction focuses on dental compensation—moving the teeth within the existing jaw structure. Traditional metal or ceramic braces use brackets and wires to apply controlled forces, gradually repositioning the misaligned teeth. Braces are a highly effective method, particularly for severe dental crossbites.
Clear aligner therapy, such as Invisalign, provides a discreet alternative for mild to moderate crossbites. These custom-made plastic trays are worn most of the day and exchanged every few weeks to incrementally shift the teeth. To manage crossbites, aligners often require auxiliary components like attachments and elastic bands.
Specialized orthodontic mechanics are incorporated into both braces and aligner treatment. Crossbite elastics are small rubber bands stretched between anchors on the upper and lower teeth to apply the opposing forces needed to move the tooth past the bite obstruction. In some cases, a single anterior crossbite can be corrected with a removable appliance that incorporates a spring to push the tooth forward.
Surgical Solutions for Severe Skeletal Issues
When a crossbite is caused by a severe skeletal discrepancy that cannot be corrected by tooth movement alone, surgical intervention is necessary for adults with fully fused jawbones. Surgically Assisted Rapid Palatal Expansion (SARPE) addresses transverse skeletal issues, such as a severely narrow upper jaw. The procedure involves a maxillofacial surgeon making small cuts in the bone of the maxilla to loosen the fused mid-palatal suture.
A palatal expander is used immediately following the surgery to widen the arch. The bony cuts allow the expansion to be purely skeletal rather than just tipping the teeth. SARPE is typically done under general anesthesia and is followed by several months of orthodontic expansion and stabilization.
For complex cases involving significant discrepancies in the front-to-back or vertical dimensions of the jaw, orthognathic surgery, or corrective jaw surgery, is required. This involves repositioning the entire upper jaw (Le Fort I osteotomy) or the lower jaw (mandibular osteotomy) to achieve comprehensive skeletal and dental alignment. Orthognathic surgery is a combined effort between the orthodontist and the surgeon, often requiring pre-surgical orthodontics to prepare the arches for their new positions.