Orthodontics and Speech Therapy: When Bite and Speech Are Connected

How malocclusion affects speech production

Speech sounds are produced by shaping airflow using the tongue, teeth, lips, and palate in precise ways. Any structural alteration to these components can interfere with sound production. An anterior open bite — where the upper and lower front teeth do not meet — creates a gap through which air escapes when producing sibilant sounds (s, z, sh, ch), typically causing a frontal lisp. A large overjet (protruding upper teeth) forces the tongue to compensate for the increased space, altering 's' and 'th' sounds. A posterior crossbite can affect lateral tongue posture and the production of sounds that require the tongue to contact the hard palate. Severe Class III malocclusion may affect labio-dental sounds such as 'f' and 'v'.

Open bite and lisping

Anterior open bite is the malocclusion most strongly linked to speech difficulties. The persistent gap between upper and lower front teeth encourages a tongue thrust swallowing pattern — where the tongue protrudes forward between the teeth during swallowing — and a frontal lisp during speech. The tongue thrust may be a cause of the open bite (where prolonged thumb sucking or a resting low tongue posture pushed the teeth apart) or a consequence of the gap (where the tongue automatically fills the available space). Disentangling cause and effect matters for treatment planning: if tongue thrust is driving the open bite, orthodontic treatment alone without myofunctional therapy addressing the habit is likely to result in relapse.

Tongue thrust and myofunctional therapy

Tongue thrust is an atypical swallowing pattern where the tongue pushes forward against or between the teeth rather than resting on the palate. It affects approximately 30 to 40% of children and typically resolves spontaneously, but persists in a proportion of adults. When tongue thrust is associated with speech difficulties or orthodontic relapse risk, orofacial myofunctional therapy (OMT) — exercises to retrain tongue and lip posture and swallowing pattern — can be effective. In the UK, myofunctional therapy is provided by some speech and language therapists (SLTs) and by a small number of specially trained dental professionals. Referral is usually via the orthodontist or GDP. Evidence for OMT specifically in adults is more limited than for children.

Orthodontic treatment and speech improvement

Correcting the underlying structural cause of a speech problem through orthodontics can lead to spontaneous speech improvement — particularly when the malocclusion is severe and the speech difficulty is clearly structural rather than habitual. Patients with anterior open bite who have it closed with orthodontic treatment often find that the lisp resolves on its own within weeks to months as the tongue adapts to the new anatomy. Children tend to adapt faster than adults. However, long-standing compensatory speech patterns — habits built up over many years — may persist even after the bite has been corrected. These patients benefit from formal speech and language therapy to establish new patterns.

Collaboration between orthodontists and speech and language therapists in the UK

In complex cases, particularly children with significant open bite, tongue thrust, or velopharyngeal insufficiency (relevant in cleft palate patients), close collaboration between the orthodontist and an NHS or private SLT is best practice. Hospital orthodontic departments treating complex cases, cleft teams, and multidisciplinary facial growth clinics in major NHS trusts routinely include SLT input. For patients in primary care orthodontic settings, the orthodontist can recommend SLT assessment and it is worth asking GP or health visitor to make a referral if speech difficulties are present. NHS SLT is available for children, with varying thresholds and waiting times by region.

Realistic expectations for speech after orthodontic treatment

Orthodontic treatment is not speech therapy. For mild speech adaptations caused by structural factors, correction of the bite frequently leads to noticeable improvement. For deep-seated habitual patterns, speech therapy is needed. Patients should not expect immediate speech changes after brace fitting — indeed, fixed braces cause temporary speech changes during the initial weeks of treatment as the tongue adapts to the new hardware. These typically resolve spontaneously. Adults who have had uncorrected open bite for decades may find that even after orthodontic correction, the lisp requires targeted therapy to resolve, as the motor pattern is deeply ingrained.

Useful related pages

This guide is for general information only. It is not a diagnosis, treatment plan, or substitute for advice from a registered dentist or orthodontist.