|Other names||Open-mouth breathing, mouth breathing habit|
Human infants are sometimes considered obligate nasal breathers, but generally speaking healthy humans may breathe through their nose, their mouth, or both. During rest, breathing through the nose is common for most individuals. Breathing through both nose and mouth during exercise is also normal, a behavioral adaptation to increase air intake and hence supply more oxygen to the muscles. Mouth breathing may be called abnormal when an individual breathes through the mouth even during rest. Some sources use the term "mouth breathing habit" but this incorrectly implies that the individual is fully capable of normal nasal breathing, and is breathing through their mouth out of preference. However, in about 85% of cases, mouth breathing represents an involuntary, subconscious adaptation to reduced openness of the nasal airway, and mouth breathing is a requirement simply in order to get enough air. Chronic mouth breathing in children may affect dental and facial growth. It may also cause gingivitis (inflamed gums) and halitosis (bad breath), especially upon waking if mouth breathing occurs during sleep.
Mouth breathing has been classified according to etiology into three groups: obstructive, habitual and anatomic.:281
The nasal airway may be compromised partially (where there is increased resistance to the flow of air due to narrowing of the lumen at some point in the upper respiratory tract) or completely obstructed. Such individuals may find it difficult or impossible to breathe through their nose alone. In about 85% of cases, mouth breathing is an adaptation to nasal obstruction. Specific causes of nasal obstruction which have been linked to mouth breathing include antrochoanal polyps.:350
Gingivitis,:85 gingival enlargement,:85 and increased levels of dental plaque:108 are common in persons who chronically breathe through their mouths. The usual effect on the gums is sharply confined to the anterior maxillary region, especially the incisors (the upper teeth at the front). The appearance is erythematous (red), edematous (swollen) and shiny. This region receives the greatest exposure to airflow during mouth breathing, and it is thought that the inflammation and irritation is related to surface dehydration, but in animal experimentation, repeated air drying of the gums did not create such an appearance.:85
It has been suggested that chronic mouth breathing in children can lead to the development of a long, narrow face, sometimes termed long face syndrome, when the mouth breathing is related to adenoid hypertrophy. Malocclusion of the teeth (e.g., crowded teeth) is also suggested to result from chronic mouth breathing in children. Conversely, it has been suggested that a long thin face type, with corresponding thin nasopharyngeal airway, predisposes to nasal obstruction and mouthbreathing, i.e., a long thin face may cause mouth breathing rather than the other way around. Facial form is also strongly influenced by genetic factors.
The following other conditions are also associated with mouth breathing: cheilitis glandularis,:490 Down syndrome,:365 anterior open bite,:225 tongue thrusting habit,:225 cerebral palsy,:422 sleep apnea, and snoring.
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