Orofacial myofunctional disorders, also known as infantile swallowing or tongue dysfunction, is caused by an imbalance in the muscular strength of the tongue, lips, cheek and jaw muscles. The muscles of these structures are only slightly developed.

Visible signs are usually an open mouth in combination with a lack of nasal breathing, a shortened upper lip, misaligned teeth and jaw and increased salivation. The tongue lies between the teeth when at rest and presses against the teeth when swallowing. Dyslalia, which mainly affects the sibilant sounds, especially /s/, is also common.