Adenoid hypertrophy can affect orthodontics. Adenoid hypertrophy can cause varying degrees of increased nasal ventilation resistance, resulting in varying degrees of nasal congestion. Patients with more severe adenoidal hypertrophy may experience prolonged open-mouth breathing and severe snoring, open-mouth breathing and breath-holding during sleep, which is also common in developing toddlers and children. Long-term open-mouth breathing can lead to abnormal development of the jaw and face, causing high arches in the hard palate and disorderly alignment of the teeth, resulting in the so-called adenoid face. Orthodontic treatment is best to improve the nasal congestion and open-mouth breathing caused by adenoid hypertrophy at an early stage. Most patients may require further adenoidectomy to completely remove the nasopharyngeal obstruction and restore nasal ventilation for the next step of orthodontic treatment.