Abstract:

The patients with skeletal class Ⅱ malocclusion are often accompanied by structural and functional abnormalities of the upper airway， and obstructive sleep apnea hypopnea syndrome （OSAHS） may occur in severe cases. The morphologic and fluid dynamic changes of the upper airway in one patient with skeletal class Ⅱ malocclusion accompanied by OSAHS after maxillomandibular advancement （MMA） surgery were observed.The patient was a 27-year-old male with skeletal class Ⅱ malocclusion and moderate OSAHS. Combined orthodontic and orthognathic treatment was conducted， involving the anterior movement of the maxilla and mandible. After surgery， the patient’s facial and intraoral features showed a satisfactory occlusion relationship with normal overbite， overjet and canine-molar relationships. There was also a significant improvement in the upper airway flow field. Two years after surgery， the cross-sectional area of the nasopharyngeal airway increased by 10.76% with a 55.36% reduction in pressure. The oropharyngeal airway showed a 108.25% increase in cross-sectional area with a 98.14% pressure reduction. The hypopharyngeal airway exhibited a 97.51% increase in cross-sectional area with a 351.03% pressure reduction. The laryngopharyngeal airway demonstrated a 27.54% increase in cross-sectional area with a 95.62% pressure reduction. The apnea-hypopnea index （AHI） decreased by 55.45%， achieving the treatment goal. Morphological measurements combined with fluid dynamic analysis can comprehensively evaluate the condition of the upper airway. The approximate value of the critical closing pressure（Pcrit） obtained from computational fluid dynamics （CFD） analysis may serve as a simple quantitative indicator for assessing the upper airway condition.

Key words: Maxillomandibular advancement surgery, Upper airway, Obstructive sleep apnea- hypopnea syndrome, Computational fluid dynamics, Case report