Tongue thrust is the abnormal habit of placing the tongue between the teeth before and during the act of swallowing. During each swallow, the tongue exerts momentary pressures of a few pounds on the surrounding structures of the mouth. Tongue thrust can move teeth into abnormal positions and can lead to facial growth problems. "Tongue thrust swallowing" is defined as the placement of the tongue tip forward between the anterior teeth during swallowing and is often associated with an anterior open bite.
An anterior open bite, or a tendency for, is when the anterior teeth do not vertically overlap, or overlap just slightly. In an ideal occlusion, the anterior teeth vertically overlap about 25%. When there is an anterior open bite it is more difficult to seal off the front of the mouth during swallowing to prevent food or liquids from escaping. Bringing the lips together and placing the tongue between the separated anterior teeth is a method of forming an anterior seal to close off the front of the mouth.
Most individuals breathe through their nose, with their lips closed and posterior teeth almost in contact. At rest, the tongue sits towards the roof of the mouth and moves back during swallowing. Swallowing occurs on average twice a minute while awake and once a minute while sleeping.
Large tonsils and/or adenoids and chronic nasal inflammation can contribute to a tongue thrust and poor tongue posture. The inability to breathe through the nose can cause an individual to become a mouth breather. Breathing through the mouth often leads to poor tongue posture. In order to maintain a maximum airway, the tongue assumes a low and forward position as the lower jaw opens in mouth breathing. The anterior tongue posture can once again move teeth into abnormal positions and lead to facial growth problems.
Overall the tongue is a very strong muscle and can have an effect on orthodontic treatment. Depending on each individual's orthodontic situation, myofunctional therapy may be recommended in an attempt to alleviate the adverse effects of tongue thrust and tongue posture.