Tongue thrust (also called reverse swallow or immature swallow) is a pseudo-pathological name of what is either considered a normal adaptive lip seal mechanism, whereby normal nasal breathing or normal swallowing can occur, or seen as an oral myofunctional disorder - a tongue muscle pattern that is perceived as clinically abnormal and in which the tongue protrudes anteriorly to seal otherwise incompetent lips.
Tongue thrusting is only seen during speech, swallowing or eating, and in order to close otherwise incompetent lips on background of an almost ubiquitous small lower jaw and anterior open bite. The behaviour is apparent only during a normal awake state, and whilst the tongue (and rest of the body) is in normal resting tone. By descriptive inference, tongue thrusting is impossible during deep sleep, or non-tone phases; or in particular during non-conscious states.
Nearly all infants exhibit a swallowing pattern involving forward tongue tip push as part of infant suckling behaviour. By six months of age most lose the forward extent of this push once paediatric incisal teeth erupt, and normal lip seal is automatically acquired as solid foods begin.
There are thus two community and clinical professional views of the observation of tongue thrusting behaviour that persists past the neonatal period.
1. Either it is a normal adaptive means of closing an open (or incompetent) lip state, caused by a unique combination of anatomical reasons, or
2. Tongue thrusting is the cause or potentiator of an open or incompetent lip state, and which resists efforts at behavioural change or clinical attempt at remedy.
In generality, tongue thrusting is poorly understood. In particular it lacks consensus on many points of description, causality, effect or management and between the various clinical groups that each offer different forms of treatments or philosophies of professional interest.
The classical view of tongue thrusting
Since 1958, the term "tongue thrust" has been described and discussed in speech and orthodontic (dental) publications and by a range of writers - and speaking from specific non-medical professional perspectives and clinical biases - as a pathological event that exists as an entity for itself and without fundamental or primary functional or necessary cause.
Both the general dental and speech pathologist classical views are that tongue thrusting causes both the dentofacial abnormality of anterior open bite, and the incompetent lip seal and swallowing and speech effects associated with tongue thrust.
In both professions, tongue thrust is represented as a behavioural disturbance which can be taught to be resisted. Such interventional therapy is represented to strongly assist orthodontic or speech pathologist efforts at resolution of both the speech and orthodontic effects of anterior open bite and the associated lip incompetence of both.
As with normal reflexes, most school-age children have tongue thrust if looked for. For example, according to recent literature, as many as 67–95 percent of children 5–8 years old exhibit tongue thrust, which may professionally be represented as associated with or contributing to an orthodontic or speech problem - depending on the clinical bias of proposal. Up to the age of four, as with the complex conversion of all simpler reflex events, there is a possibility that any observed child will normally outgrow tongue thrust as they transition to a fuller dentofacial development. However, if a tongue thrust pattern is retained beyond infancy, it can be seen through a lens of abnormality, and this vulnerable to clinical bias and attempts to clinically interact.