Crossbite: When the Bite Sits the Wrong Way Round
For adults asking about a crossbite: how anterior and posterior types differ, what a functional shift is, and what guidance and evidence say about timing and correction by age. In a functional posterior crossbite, teeth interfere on closing and the lower jaw shifts to one side, a Cochrane review's background says.
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Medical disclaimer: This page is for general information only. It does not replace an examination or treatment by a dentist.
Dr Ibraheem Ijaz, principal dentist, reviewed this page. He is a General Dental Practitioner: BDS, BSc (Hons), MSc (Leeds), PG Dip Implant Dentistry, PG Cert Restorative and Aesthetic Dentistry.
What is a crossbite?
A crossbite is a bite where some upper teeth close behind or inside the lower teeth, instead of in front of or outside them.
The British Orthodontic Society (BOS) adult guide says a crossbite can create an asymmetrical smile and make eating more challenging. It adds that teeth can meet awkwardly, causing damage or wear to their tips.
What is the difference between an anterior and a posterior crossbite?
An anterior crossbite involves front teeth and a posterior crossbite involves back teeth.
| Anterior | Posterior | |
|---|---|---|
| Teeth | One or more upper front teeth behind the lower ones | Upper back teeth biting inside the lower back teeth |
| Direction of any jaw shift | Forward | To one side |
A posterior crossbite can affect one side or both, and occurs when the upper teeth or jaw are narrower than the lower teeth, Cochrane's 2021 background says.
Cochrane's 2024 review lists anterior crossbite, like an underbite, among terms for prominent lower front teeth.
What is a functional shift?
A functional shift means the lower jaw moves as the teeth close, because teeth interfere with a comfortable bite.
Cochrane's 2021 background describes a functional posterior crossbite: the lower jaw shifts to one side into a position where more teeth touch. In anterior crossbite with a functional shift, a 2015 Swedish thesis describes front teeth meeting edge to edge, then the lower jaw and front teeth being guided forward.
Cochrane's background says the sideways displacement may increase the likelihood of tooth grinding, which may lead to worn tooth surfaces, abnormal growth and development of the teeth and jaws, and jaw joint problems. Strain on the jaw may lead to skeletal facial asymmetry, it adds. For the condition, see tooth wear.
A 2016 review of 45 medium-low quality studies says most available studies report asymmetric jaw growth with a one-sided crossbite but calls the link with skeletal asymmetry unresolved.
When has guidance recommended assessing a child's crossbite?
An archived British Orthodontic Society page for dentists, copyright 2014, lists crossbites with a jaw shift for referral while baby and adult teeth are mixed.
BOS says most patients can be referred once adult teeth are first established, but lists these crossbites for earlier assessment. A 2015 reference guide hosted on the NHS England site also lists crossbites for referral at the mixed stage.
Cochrane's 2021 background says most posterior crossbites (50% to 90%) persist as adult teeth erupt, and that the optimum timing of treatment is still debated. A 2024 narrative review of functional posterior crossbite notes self-correction from baby to mixed teeth, but says the literature suggests starting early to increase success, weighing risk and benefit.
To ask about orthodontic treatment, book online or call 0114 288 2121.
What does evidence say about correcting a crossbite in children and adolescents?
Cochrane's 2021 background says posterior crossbite treatment usually involves expanding the upper arch, removing tooth interferences and eliminating the jaw's sideways displacement.
Its 2021 review, searched to April 2021, covers 31 randomised trials and about 1,410 children and adolescents without skeletal Class III, cleft or craniofacial syndromes, 15 trials at high risk of bias. In children aged 7 to 11, two of the arch expansion appliances tested each corrected one-sided posterior crossbite better than no treatment, on high-certainty evidence from three trials. Beyond these and some comparisons between appliances, it calls the remaining evidence insufficient for robust conclusions.
The available trials to April 2021 were not sufficient to address stability, jaw joint symptoms or quality of life, it says. A 2024 review of 22 studies of varying design and quality, covering 1,076 growing children treated with expansion, pooled posterior crossbite relapse at 19.5% at two years or more, with a moderate level of evidence.
For non-skeletal anterior crossbite in mixed teeth, a 2020 review of seven articles found two appliance types corrected overjet equally, with very low certainty. Both can bring pain and discomfort and affect everyday activities, chewing and speech, it adds.
What does evidence say about adults with a crossbite?
Cochrane's 2021 review of randomised trials, searched to April 2021, found no evidence on orthodontic treatment of posterior crossbites in adults.
It says this is probably because most adult studies compared orthodontic with orthodontic-surgical treatment. BOS says in severe cases braces and jaw surgery may be required. See how teeth move for the biology.
In a 2008 study of 25 adults aged 17 to 26 with an uncorrected one-sided posterior crossbite, 36% had no bite midline shift and the rest shifted towards the crossbite side, and a jaw guidance angle was lower there. No measure differed significantly from normal bites. On these measures, the authors concluded such adults have adaptations that compensate and maintain normal function.
Is a posterior crossbite linked to jaw joint problems?
Cochrane's 2021 background says some teenagers and adults with a crossbite may have a higher risk of temporomandibular joint (jaw joint) problems. It calls more recent studies less conclusive on a link with posterior crossbite.
A 2013 review of 43 medium-low quality studies, searched to April 2012, could not establish an association with muscle pain or disc displacement. A 2012 review of 14 publications from 1970 to 2009 says a functional posterior crossbite seems associated with headache, jaw joint and muscle pain, and clicking, while an overall link was reported as often as not.
A 2025 review of 13 cross-sectional studies of bite problems in under-18s says posterior crossbite may be associated with jaw pain signs and symptoms. Five linked them, all at very low certainty. At least one found no difference.
The NHS says temporomandibular disorder (TMD) is not usually serious and generally gets better on its own. Ask for an urgent GP appointment or get help from 111 now if you are unable to eat or drink, have clicking, popping or grinding noises when you move your jaw, have difficulty opening your mouth fully or your jaw is locking, have pain around your jaw, ear or at the side of your head, have frequent, severe headaches, have pain or tenderness at the side of your head or on the scalp, or have vision problems, such as double vision or loss of vision in one or both eyes.
These can be signs of a serious problem that needs urgent treatment. You can call 111 or get help from 111 online.
Who is orthodontic treatment at Deepcar Dental Care for?
Orthodontic treatment at Deepcar Dental Care is for adults only.
See orthodontics at Deepcar Dental Care for the treatments offered.
Frequently asked questions
Does a crossbite need fixing?
Need varies. The Index of Orthodontic Treatment Need, used for adult teeth, grades a crossbite by the gap between the jaw's retruded contact position and its full bite: 1 mm to 2 mm is grade 3 ("borderline need") and over 2 mm is grade 4 ("need treatment").
Can a child's posterior crossbite correct itself?
It can, but how often is unclear. A 2023 review of seven cohort studies reported self-correction in 12.2% to 77.1% from baby to mixed teeth, about 16% from mixed to adult teeth and 20% to 82.8% from baby to adult teeth, at very low to moderate certainty. Cochrane's 2021 background says most persist as adult teeth erupt.
Is a one-sided posterior crossbite linked to an uneven lower jaw in adults?
Studies differ. A 2020 scan study of 38 adults found greater, possibly mild, lower jaw asymmetry than in 19 controls. A 1995 study of 30 adults found no skeletal asymmetry of the lower jaw, though the jaw sat rotated relative to the skull.
Can a crossbite affect eating?
It can in adults, BOS says. If eating is difficult, show a dentist. For posterior crossbite, Cochrane's 2021 background says young children are unlikely to have pain or chewing problems. A 2016 review of medium-low quality studies says people with a one-sided crossbite show smaller bite force than others, on fewer data.
How common is a posterior crossbite?
Figures vary by study. Cochrane's 2021 background gives around 4% of children and adolescents in Europe and 17% in America for posterior crossbite. A 2018 review of 53 population studies averaged 9.39% with adult teeth and 11.72% with mixed teeth, counting more than two affected teeth.
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