Abstract: Objective　To compare the effects of extraction versus nonextraction orthodontic treatments on oropharyngeal airway volume in patients with skeletal classⅠmalocclusion. Methods　40 patients with skeletal classⅠmalocclusion were selected, including 20 with four premolars extracted (Extraction Group, ExtG) and 20 controls (Non-extraction Group, NExtG). They were screened for pretreatment (T0) and posttreatment (T1) cone beam computed tomography (CBCT) scans. Constructed lateral cephalograms (three skeletal and four dental variables) and oropharyngeal (OP) volumes were measured at T0 and T1. Paired sample t-tests were used to compare the mean changes from T0 to T1 in both ExtG and NExtG. Independent sample t-tests were used to evaluate the different effects of extraction versus non-extraction treatment on oropharyngeal airway volume. Results　Changes in CoA and CoGn from T0 to T1 were found to be significant in both groups (P＜0.01）. In the ExtG alone, significant differences in U1-FH、IMPA、U1-Na Perp and L1-Na Perp were also found at the end of the treatment (P＜0.01). Despite the observed changes, differences in OP volumes and minimal constricted axial areas from T0 to T1 were not significant between two groups（P＞0.05）. In the ExtG, the location of the minAx changed in 8 patients at T1, and the minAx of 6 patients changed in NExtG at T1. Conclusion　Extraction of four premolars with retraction of incisors does not affect OP airway volume in the orthodontic treatment of skeletal classⅠmalocclusion.

Key words: Cone- beam compute tomography, cephalometric, Oropharyngeal airway, Extraction treatment, Non-extraction correction