The way a person breathes can profoundly influence the development of their face and the alignment of their teeth. Chronic oral breathing is strongly linked to the development of malocclusion, the term for misaligned teeth or a “bad bite.” Mouth breathing is defined as breathing primarily through the mouth instead of the nose, often becoming a long-term habit that extends beyond temporary nasal congestion. This habit can set off a chain reaction that physically alters the growth of the jawbones, leading to less space for the teeth to erupt properly.
The Link Between Breathing Patterns and Oral Structure
Humans are anatomically designed to be nasal breathers at rest, as the nose filters, warms, and humidifies the air before it reaches the lungs. A proper oral rest posture, which accompanies nasal breathing, involves the lips being sealed and the tongue resting high against the entire palate, or roof of the mouth. This high tongue position is essential because the constant, gentle pressure from the tongue against the palate encourages the upper jaw to widen laterally as a child grows.
When a person must breathe through their mouth, the tongue drops from the palate to the floor of the mouth to create a clear airway. This shift in tongue posture removes the natural internal pressure necessary to guide the healthy, horizontal development of the maxilla. Without the tongue’s support, the upper jaw is left vulnerable to external forces, which begins the process of structural change.
How Mouth Breathing Affects Craniofacial Growth
The removal of the tongue’s internal force is the primary mechanical explanation for how mouth breathing alters facial development. The maxilla, or upper jaw, is no longer supported from within and becomes susceptible to the constant, unopposed pressure exerted by the cheek muscles. This imbalance causes the upper arch to collapse inward, resulting in a narrower dental arch and a high, vaulted palate.
As the upper arch narrows, there is insufficient space for the permanent teeth, which directly leads to dental crowding and rotation. Chronic mouth breathing often causes the jaw to rotate downward and backward to maintain an open airway, contributing to an elongated lower facial height. This rotation can change the overall facial profile, leading to a flatter mid-face and a less-defined jawline. These changes are most pronounced during the rapid growth periods of childhood when the skeletal structures are highly responsive to functional stimuli.
Specific Dental and Facial Consequences
The altered growth pattern initiated by chronic oral breathing leads to several recognizable dental and facial conditions, collectively known as malocclusions. One common result is a posterior crossbite, which occurs when the narrow upper jaw causes the upper back teeth to bite inside the lower back teeth. Another frequent finding is an anterior open bite, where the front upper and lower teeth do not overlap or meet when the mouth is closed.
Severe dental crowding is a near-universal consequence, as the constricted maxillary arch cannot accommodate all the teeth in a straight line. The downward and backward rotation of the lower jaw can also create a Class II malocclusion, sometimes called an “overjet,” where the upper front teeth protrude significantly past the lower teeth. These structural changes can also manifest as “adenoid facies,” a collection of features including a long, narrow face, dark circles under the eyes, and a perpetually open-mouthed expression.
Identifying and Correcting the Habit
Recognizing chronic mouth breathing involves looking for consistent signs, such as waking up with a dry mouth, chronic bad breath, or a habitually open-mouthed posture. Other indicators include a history of snoring, frequent upper respiratory infections, or dark circles beneath the eyes. For children, chronic mouth breathing is often initiated by a physical blockage in the airway, such as enlarged tonsils, adenoids, or a deviated septum.
The first step toward correction involves consulting an Ear, Nose, and Throat (ENT) specialist to identify and resolve any underlying physical obstruction. Once the airway is clear, the focus shifts to behavioral correction, primarily through a specialized treatment called Myofunctional Therapy. This therapy uses targeted exercises to retrain the muscles of the tongue, lips, and cheeks to establish proper function and oral rest posture. Myofunctional therapy aims to restore nasal breathing by teaching the tongue to rest high on the palate and promoting a lip seal.