Mouth breathing is an inevitable result of obstruction of the nasal airway. Associated changes in mandibular posture and the function of related muscles have long been postulated to cause undesirable changes in facial growth. Evidence for such a causeeffect relationship is reviewed and illustrated with clinical records.
McNamara, J. A. (1984). Influence of respiratory pattern on craniofacial growth, International Journal of Orofacial Myology, 10 (2), 14-32.