Nasal breathing is the intended physiological standard for human respiration, filtering, warming, and humidifying air before it reaches the lungs. When a person, particularly a child during developmental years, breathes chronically through the mouth, this altered function profoundly influences the growth trajectory of the facial bones and dental arches.
The soft tissues and muscles adapt to keep the airway open, applying imbalanced forces to the developing skull structure. This article explores the mechanisms and anatomical consequences of chronic mouth breathing on the jaw and facial complex.
How Mouth Breathing Affects Oral Posture and Development
The most significant change caused by chronic mouth breathing involves the resting position of the tongue. Optimal oral posture requires the tongue to rest gently but firmly against the roof of the mouth (the palate or maxilla). This continuous pressure acts as a natural internal orthopedic expander, stimulating the upper jaw to grow horizontally and forward.
When the mouth drops open to facilitate breathing, the tongue must drop to the floor of the mouth to clear the pharyngeal airway. This shift removes the essential outward pressure on the maxilla, disrupting the balance of forces that shape the upper jaw. The powerful buccinator muscles in the cheeks then press inward on the upper teeth and bone without counter-resistance from the tongue.
This muscular imbalance leads to the progressive narrowing of the upper dental arch and palate. To maintain an open airway, the lower jaw (mandible) often rotates backward and downward. This postural adaptation physically lowers the jaw, creating space at the back of the throat, fundamentally altering craniofacial growth.
Defining the Structural Changes to the Jaw and Face
The biomechanical forces resulting from a low tongue posture lead to several structural changes. The upper jaw typically develops a narrow, V-shaped dental arch and a high, vaulted palate. This narrowness reduces space for permanent teeth, resulting in crowding and posterior crossbites.
The backward and downward rotation of the mandible contributes to an increased lower anterior facial height, often giving the appearance of a long, vertical face. This growth pattern is sometimes described as an “adenoid face” pattern. The retruded position of the lower jaw results in a convex facial profile and a receding chin appearance, known as Class II malocclusion.
These skeletal changes are compounded by dental issues, including an increased overjet (upper front teeth protrude over the lower teeth). The constant lip-apart posture leads to incompetent lip seal and chronic dryness. The altered jaw position contributes to forward head posture as the individual strains neck muscles to open the airway.
Primary Causes of Nasal Obstruction and Mouth Breathing
The switch from nasal to oral breathing is a compensatory reaction to a physical blockage in the nasal passages. In children, enlarged adenoids and tonsils are common culprits, physically obstructing the nasopharynx and forcing the mouth open for air intake. When these lymphatic tissues swell due to infection or chronic inflammation, they restrict airflow.
Structural abnormalities within the nose itself also compel oral breathing. These include a deviated nasal septum, non-cancerous growths called nasal polyps, or chronic inflammatory conditions like allergic rhinitis or chronic sinusitis, which cause the nasal turbinates to swell and block air passage.
In some cases, the initial physical obstruction is resolved, but the mouth breathing habit persists as a learned muscle memory. This habitual pattern remains problematic because the soft tissues continue to function detrimentally to proper jaw development, even when the nasal airway is clear. A complete assessment is necessary to distinguish between a physical obstruction and a persistent habit.
Intervention Strategies for Correction
Addressing chronic mouth breathing requires a multidisciplinary approach that first targets the underlying cause of the nasal obstruction. An ENT specialist may recommend medical management (steroid nasal sprays or antihistamines) or surgical intervention (tonsillectomy, adenoidectomy, or septoplasty) if the obstruction is structural.
Once the nasal airway is patent, myofunctional therapy is implemented to retrain the oral and facial muscles. This therapy uses targeted exercises to normalize tongue posture, encouraging it to rest against the palate and establishing a closed-lip seal. Myofunctional therapy is important for correcting ingrained habits and ensuring soft tissues support the skeletal structure.
Orthodontic intervention frequently involves orthopedic devices like palatal expanders, especially in growing children. These appliances gradually widen the upper jaw, reversing the constriction caused by the lack of tongue pressure. Palatal expansion creates space for crowded teeth and widens the floor of the nasal cavity, facilitating easier nasal breathing. The combination of airway clearance, orthopedic expansion, and muscle retraining offers the best chance to guide the jaw and face toward a balanced growth pattern.