Abstract: PURPOSE: This study was performed to investigate the changes of upper airway before and after functional correction in ClassⅡmalocclusion children with high mandibular plane angle at growth and development peak. METHODS: Cone-beam CT (CBCT) data of the upper airway were inputted into Minics 17.0 software for measurement of changes in the upper airway before and after functional treatment by high headgear-activator. The changes of upper airway before and after treatment were analyzed with SPSS22.0 software package. RESULTS: The change of the total volume of the upper airway, the volume of the velopharynx, glossopharynx, laryngopharynx; the sectional area of the tip of soft palate, roof of the epiglottis, the minimum sectional area of the oropharynx were significant (P<0.05). The upper airway morphology tended to be circular in the soft palate tip plane(P<0.05), but there was no significant difference in the plane of epiglottis(P>0.05). CONCLUSIONS: High headgear-activator corrected mandibular hypoplasia in children with increased airway volume, increased ventilation, improved respiratory function to prevent occurrence of obstructive sleep apnea hypopnea syndrome after adult.

Key words: High headgear-activator, Cone-beam CT, Upper airway, Three-dimensional reconstruction, Mandibular retrusion, High mandibular plane angle