Clear aligners are transparent, custom-made trays used for straightening teeth. They work by applying gentle, consistent pressure to guide teeth into a new position over a series of aligner sets. A crossbite is a common type of dental misalignment where one or more of the upper teeth fit inside the lower teeth when the mouth is closed.
Understanding Crossbites
A crossbite is a form of malocclusion characterized by a lateral misalignment of the dental arches. Unlike a normal bite, where the upper teeth slightly overlap the outside of the lower teeth, a crossbite reverses this relationship in the affected area. This misalignment can occur in the front of the mouth, known as an anterior crossbite, or in the back teeth, referred to as a posterior crossbite.
For treatment planning, orthodontists distinguish between two primary causes of a crossbite. A dental crossbite involves only the teeth being misaligned, meaning the underlying jaw structure is generally proportional. A more complex condition is a skeletal crossbite, which stems from a discrepancy in the size or position of the jawbones themselves. This skeletal issue might manifest as a narrow upper jaw or a lower jaw that is overgrown relative to the upper one.
Aligners and Correction Feasibility
Clear aligners can effectively treat many cases of crossbite, particularly those classified as mild to moderate dental crossbites. The plastic trays exert pressure to push the misaligned teeth laterally, expanding the dental arch width or shifting individual teeth into their correct position outside the opposing arch.
The success of clear aligners in crossbite correction relies on the precise, staged movements programmed into each aligner set. For cases involving a single tooth or a few teeth that are tipped out of alignment, the aligner’s ability to apply pressure across the entire tooth surface is highly effective. Treatment duration can vary widely depending on the case’s complexity, but minor dental crossbites may be corrected within a comparable timeframe to other common alignment issues.
The feasibility of using aligners hinges entirely on an accurate diagnosis of the crossbite’s origin. Clear aligners are primarily tools for moving teeth, making them well-suited for dental corrections where the jawbones are not significantly misaligned. If the problem is purely dental, the aligners can use the jaw as a stable anchor point to push the teeth across the bite line.
Limitations and Required Adjuncts
Clear aligners alone are typically insufficient for treating severe crossbites or those with a significant skeletal component, as the required tooth movement often exceeds what aligners can predictably achieve when the jaws have a major structural mismatch. In these complex situations, the clear aligner system must be combined with auxiliary devices, known as adjuncts, to achieve the desired outcome.
One common adjunct is the use of orthodontic elastics, or rubber bands, which are attached to small, tooth-colored buttons or precision cuts placed on the aligners. These elastics span between the upper and lower teeth, applying a continuous, directional force that the aligners cannot generate independently. This force is crucial for moving an entire segment of teeth or correcting the bite relationship between the arches.
Attachments, which are small composite resin shapes bonded directly to the teeth, are also frequently necessary. These attachments provide the aligner plastic with a better grip, allowing it to deliver complex biomechanical forces, such as rotating a tooth or pushing it bodily.
Temporary Anchorage Devices (TADs)
For highly advanced movements that require maximum anchorage, Temporary Anchorage Devices (TADs), which are small, temporary screws placed into the jawbone, may be used. TADs provide a fixed point from which to pull teeth, significantly increasing the range and predictability of the aligner treatment.
Alternative Treatment Paths
For patients whose crossbite is too severe or is caused by a major skeletal discrepancy, alternative treatments offer more robust solutions. Traditional fixed appliances, commonly known as braces, are often recommended because they use brackets and wires to apply stronger, continuous forces over longer distances. Braces are capable of complex root movements that may be challenging for clear aligners, even with adjuncts.
In younger patients whose jawbones are still developing, a palatal expander may be used to correct a narrow upper jaw. This fixed device is cemented to the back teeth and works by gently widening the upper arch over several months. Widening the palate can resolve a posterior crossbite by allowing the upper teeth to fit properly over the lower teeth.
For adults with severe skeletal crossbites, where the jawbones are fully matured and misaligned, orthognathic surgery is sometimes necessary. This procedure involves surgically repositioning the upper jaw, the lower jaw, or both, to correct the foundational structural imbalance. Orthodontic treatment, either with braces or aligners, is typically performed both before and after the surgery to align the teeth properly within the newly corrected jaw structure.