Tongue thrust, also known as an orofacial myofunctional disorder, involves an abnormal pattern of muscle use in the mouth and face. This condition is defined by the tongue pushing forward against or between the teeth during activities like swallowing, speaking, or when the mouth is at rest. While a forward tongue position is normal for infants, it should transition to a mature swallowing pattern where the tongue rests on the roof of the mouth. When this infantile pattern persists, the constant, misplaced pressure from the tongue leads to noticeable visual changes in the mouth, teeth, and face.
Visible Signs During Rest and Swallowing
The incorrect resting posture of the tongue is a noticeable visual characteristic of tongue thrust. Instead of resting high against the palate, the tongue often sits low in the mouth or pushes forward, sometimes visible between the front teeth. This low and forward position frequently contributes to an open-mouth posture, where the lips are habitually parted.
The continuous forward tongue posture makes it difficult for the lips to seal properly, often leading to chronic mouth breathing. This can create the appearance of a constantly wet mouth or chronic lip licking as the individual compensates for dryness. The muscles around the lips may also appear strained or overly active while attempting to close the mouth against the tongue’s forward pressure.
The act of swallowing provides a brief but clear visual confirmation of the disorder. During a normal swallow, the tongue presses up against the roof of the mouth. With a tongue thrust, the tongue visibly pushes forward, often resulting in the tip protruding between the upper and lower front teeth as food or saliva is moved down the throat. Observing a person swallowing water can reveal this distinct, abnormal forward thrusting action.
How Tongue Thrust Appears During Speech
Tongue thrust often results in a characteristic lisp, which is a key visual and auditory sign. This is specifically an interdental or frontal lisp, where the tongue tip is positioned against or between the front teeth when producing certain sounds. Visually, the tongue pushes through the gap between the teeth during the articulation of sounds like /s/ and /z/.
This forward tongue position can also affect other sounds, including /t/, /d/, /n/, /sh/, and /ch/. The visual movement is a forward press, rather than the precise, quick contacts required for clear articulation. This improper placement replaces the sharp, clear acoustic quality of these sounds with a muffled, slushy, or “th-like” distortion.
The visible action of the tongue pressing forward is a result of the tongue not being able to achieve the proper resting or movement patterns. This lack of precise tongue control reduces speech clarity. For an observer, the tongue’s protrusion during conversation is the most immediate visual cue that an oromyofunctional disorder is affecting speech.
Dental and Facial Appearance Changes
The long-term consequence of tongue thrusting is visible in the alignment of the teeth and the structure of the lower face. The most distinct visual manifestation is an anterior open bite, which presents as a noticeable gap between the upper and lower front teeth when the jaw is closed. This gap is created because the tongue’s continuous forward pressure prevents the teeth from meeting correctly during development.
While momentary pressure during swallowing is too brief to move the teeth, the prolonged, light pressure from the tongue’s incorrect resting posture causes dental misalignment. Research indicates that an abnormal resting position for six hours or more per day applies enough force to gradually push the teeth out of alignment. This constant force can also cause the upper front teeth (incisors) to flare outward, giving them a protruding appearance often referred to as “buck teeth.”
The chronic open-mouth posture, often associated with the forward tongue rest, can subtly alter the overall facial appearance. This may result in a slightly elongated lower facial structure, sometimes called “long face syndrome,” due to the jaw dropping down and back to accommodate the forward tongue position. Additionally, the constant pressure of the tongue can sometimes be observed on the gums, potentially causing localized redness or irritation.
The improper muscle function may also affect the tone of the chin muscle (mentalis), which can appear strained or dimpled as the individual tries to force the lips closed. These dental and facial changes are the most structural and permanent visual evidence of a persistent tongue thrust habit. Correcting these issues often requires a combined approach of dental treatment and therapy to retrain the tongue to a proper resting and swallowing pattern.