The tongue thrust reflex, also known as the extrusion reflex, is a normal, involuntary movement present in infants from birth. This reflex is part of a set of primitive reflexes fundamental for a newborn’s survival and early development. The reflex causes the tongue to protrude when the lips or front of the mouth are touched. This automatic response facilitates safe and effective feeding when an infant’s diet consists only of liquids.
Defining the Infant Tongue Thrust Reflex
The infant tongue thrust reflex is a protective mechanism dictating how a baby interacts with objects placed near their mouth. When an object, such as a bottle nipple or a spoon, contacts the tongue or lips, the tongue instinctively pushes forward and out. This mechanism ensures the baby can create the necessary seal for sucking during feeding.
The reflex is purposed to prevent the aspiration of non-liquid food before the infant is developmentally ready to manage it. A newborn’s oral musculature is not mature enough to move food from the front of the mouth to the back for swallowing. The forward thrusting action ensures that any item that is not liquid is immediately expelled, which is why feeding solid foods to a very young baby is challenging.
The Developmental Timeline: When the Reflex Should Disappear
The tongue thrust reflex is a temporary stage of development and should naturally begin to fade as the infant matures. This transition typically starts around four to six months of age, which is the common timeframe for introducing solid foods. As the reflex diminishes, the baby gains the ability to voluntarily control tongue movements, learning to manipulate food inside the mouth.
The gradual replacement of the reflex by a mature swallowing pattern is a multi-year process. While the protective reflex fades in infancy, the complete transition to the adult swallowing pattern usually takes until a child is around six or seven years old. In a mature swallow, the tip of the tongue rests against the hard palate, not pushing against the front teeth. When the immature pattern persists past this developmental window, it is no longer considered a reflex but an orofacial myofunctional disorder (OMD).
Impact of Persistent Tongue Thrust on Oral Structure and Speech
When the tongue continues to thrust forward against or between the teeth during swallowing and at rest, the constant pressure causes significant physical changes. The tongue is a powerful muscle that exerts a sustained force, estimated to be up to four pounds with each swallow. Over time, this force can push the teeth out of alignment.
A common dental consequence is the development of an anterior open bite, where the upper and lower front teeth do not meet when the mouth is closed. This persistent forward pressure can also cause the upper front teeth to flare out, a condition known as maxillary protrusion or increased overjet. The continuous muscle action can also interfere with the proper development of the jaw and facial structure.
The abnormal tongue placement also impacts a child’s ability to articulate certain sounds correctly, leading to specific speech difficulties. The most frequent issue is an interdental or frontal lisp, where the tongue protrudes between the teeth during speech. This makes it difficult to produce sibilant sounds, such as “s” and “z,” which require the tongue to be positioned behind the front teeth.
Diagnosis and Correction of Tongue Thrust Swallowing
Diagnosis of persistent tongue thrust is often a collaborative process involving multiple healthcare professionals. A pediatric dentist or orthodontist may notice dental misalignment, while a speech-language pathologist or myofunctional therapist identifies improper swallowing and resting patterns. The initial assessment focuses on observing the tongue’s position during rest, speech, and swallowing.
The primary and most effective non-surgical treatment for this disorder is Myofunctional Therapy. This therapy consists of a structured program of exercises designed to retrain the muscles of the tongue, lips, and face. The goal is to establish a proper oral resting posture where the tongue rests on the palate and to teach the mature, correct swallowing technique.
The exercises are tailored to the individual and aim to create a new, strong muscle memory. In some cases, orthodontists may use specialized appliances, such as a tongue crib or fence, to physically block the forward thrusting of the tongue. These devices are used in conjunction with Myofunctional Therapy to help break the habit and support proper dental alignment.