Can Aligners Correct a Posterior Crossbite? Treatment Options Explained

Most people with a posterior crossbite have no idea they have one. It is not painful, it is not visible when you smile, and the mouth adapts. It is usually identified during a routine examination, or when someone finally asks why one side of their teeth is noticeably more worn than the other.

Whether it needs treating is a legitimate question, and the honest answer is that it depends. Some crossbites sit stable for decades and cause nothing. Others produce a jaw deflection, uneven wear, and localised gum recession that gradually worsens.

This article explains what a posterior crossbite is, what it does over time, and where clear aligners can and cannot help.

Will aligners fix back teeth that bite the wrong way round?

For many adult cases, yes. Where the crossbite is dental — the back teeth are tipped inward at the top or outward at the bottom, but the underlying jaw widths are reasonably compatible — aligners can correct it by tipping the upper teeth outwards and the lower teeth inwards. This works well for mild to moderate discrepancies. Where the crossbite is skeletal, meaning the upper jaw itself is narrower than the lower, tooth movement alone cannot correct it in an adult; the palatal suture has fused and true expansion requires surgically assisted techniques or a fixed expansion appliance. Distinguishing between the two is the whole point of a proper assessment, and it cannot be judged from photographs.

In a normal bite, the upper back teeth sit slightly outside the lower ones, so the upper cusps overhang the lower like a lid on a box. In a posterior crossbite, that relationship is reversed for one or more teeth — the upper tooth bites inside its lower counterpart.

It can be unilateral, affecting one side, or bilateral. Unilateral crossbites are more common and are frequently associated with a functional shift, where the jaw deviates to one side on closing to find a comfortable interdigitation.

The distinction between a true unilateral crossbite and a bilateral narrow arch presenting with a shift matters clinically. If your jaw deflects on closing, what looks like a one-sided problem may in fact be a narrow upper arch affecting both sides.

Developmental arch narrowing. The upper jaw may simply have developed narrower than the lower. Contributing factors discussed in the literature include prolonged mouth breathing, low tongue posture, and habits such as extended thumb sucking, though the evidence for each varies.

Untreated childhood crossbite. A crossbite present in the mixed dentition that was never addressed generally persists into adulthood.

Tooth drifting after loss. Losing a back tooth allows neighbours to tip into the space, sometimes creating a crossbite relationship where none existed. See missing tooth.

Orthodontic relapse. Arches that were expanded and inadequately retained tend to narrow again.

Restorations that alter tooth contour can occasionally create or worsen a crossbite relationship.

Uneven wear. Teeth in crossbite often show accelerated wear because they are contacting in a way the cusps were not designed for.

Functional shift. The jaw deflects to close, meaning the joints and muscles work asymmetrically. Whether this causes symptoms varies considerably between individuals — many people never develop any.

Gum recession. Teeth in crossbite are sometimes positioned outside the ideal bony envelope, which is associated with thinner tissue and a greater tendency to receding gums.

Fracture risk. Asymmetric loading can contribute to cusp fracture over time, particularly in heavily restored teeth.

Cleaning difficulty. Displaced teeth can create areas that are harder to clean, which is relevant for both decay and gum disease.

None of these is inevitable. The point is that they are more likely, and that they accumulate slowly, which is why crossbites picked up in adults have often already produced some of these effects.

Aligners correct dental crossbites principally by tipping. Applying a force to the crown of a tooth tips it about a point somewhere along the root, moving the biting surface outwards or inwards. For back teeth in crossbite, tipping upper teeth buccally and lower teeth lingually is usually enough to establish a normal relationship in mild to moderate cases.

Attachments bonded to specific teeth improve the aligner's grip and allow better control, including a degree of root movement where tipping alone would place the crown outside the bone.

There are real limits. Excessive tipping moves the root out of its bony housing, risking recession and dehiscence. The amount of correction achievable therefore depends on how much bone is available around the teeth, which is assessed clinically and sometimes with three-dimensional imaging.

Where genuine skeletal expansion is needed, aligners cannot deliver it. In adults the midpalatal suture has fused, and options include a fixed expander, a bone-anchored expander, or surgically assisted rapid palatal expansion. These are considerably more involved and are appropriate only for cases that genuinely need them.

Our ProAligner page describes how aligner treatment is planned and delivered.

Arrange an assessment if you notice:

• Upper back teeth biting inside the lower teeth on one or both sides

• Your jaw sliding to one side as you close

• Noticeably more wear on one side of your mouth

• Gum recession around specific back teeth

• Repeated chipping or fracture of the same teeth

• Discomfort, clicking, or tenderness in one jaw joint

• Difficulty cleaning particular back teeth thoroughly

• A child with a crossbite, which is often best assessed early

In children, crossbite correction is generally more straightforward because the palatal suture has not fused, and early assessment is worthwhile. In adults, the priority is establishing whether the problem is dental or skeletal before deciding on an approach.

The NHS provides general information about orthodontic treatment at nhs.uk/conditions/orthodontics/.

Aligner trays sit over the teeth for most of the day, so anything left on the enamel remains in contact for hours. Brush before reinserting trays, clean between the teeth daily, and drink only water while trays are in. Attend hygiene appointments at the interval recommended, and address any decay before treatment begins.

Retention after crossbite correction matters particularly, because expanded arches have a well-documented tendency to relapse. Long-term retainer wear, sometimes including a fixed retainer, is the standard recommendation. Where wear facets have already formed, restorative work may be planned after alignment is complete.

• A posterior crossbite means upper back teeth bite inside the lower ones

• Dental crossbites often respond well to aligners; skeletal ones do not

• Unilateral crossbites are frequently associated with a functional jaw shift

• Correction works mainly by tipping, which is limited by available bone

• Adult skeletal expansion requires fixed or surgically assisted appliances

• Uneven wear, recession, and fracture risk accumulate slowly over years

• Relapse after expansion is common, so retention is essential

A posterior crossbite is worth identifying even if it is not currently causing you problems, because its effects accumulate quietly. Uneven wear, recession, and asymmetric loading are far easier to prevent than to reverse.

Whether aligners are the right tool depends entirely on whether the crossbite is dental or skeletal. For mild to moderate dental crossbites in adults with adequate bone, aligners can work well. For genuine skeletal narrowness, they cannot, and being told so honestly is more valuable than being told what you hoped to hear.

To have your bite assessed, you are welcome to arrange an appointment at Wimpole Dental, 22 Wimpole St, London W1G 8GQ, or call 020 7183 0692.

Dental symptoms and treatment options should always be assessed individually during a clinical examination.

This article is for general educational information only and is not professional dental advice, diagnosis, or a treatment recommendation. Information here is general and cannot replace an in-person assessment by a qualified, GDC-registered dental professional. Symptoms, suitability, fees, timelines, and outcomes vary according to individual clinical circumstances. If you have pain, swelling, or other concerning symptoms, seek prompt professional dental care. Always request a written treatment plan and cost estimate before proceeding with treatment.

Written Date: 21 August 2026

Next Review Date: 21 August 2027