An open bite occurs when the upper teeth cannot overlap the lower teeth. From the front view, no matter how hard you bite down and close your teeth together, you will be able to see your tongue peeking through your teeth. Whenever a patient with an open bite is asked to swallow, there is a tongue thrust tendency as the tongue forms a seal to help food and water go down.
Children that do not stop thumb sucking or persistent pacifier use are at greater risk of developing open bites. Chronic mouth breathing in young children due to blocked airway and sinuses causes head posture changes, where they tip their heads back and extend their necks to breathe better. With time, the changes in head posture and tongue position can lead to an open bite.