Abstract: Objective: To evaluate the morphology changes in the upper airway after premolars extraction in patients with ClassⅠhyperdivergent. Methods: 26 patients were selected,whose cervical morphology showed that growth was finished. 4 boys and 9 girls were included in the non-extraction group [average age: (17.62±3.45) years], 3 boys and 10 girls were included in the extraction group [average age:(16.85±3.51)years]. The hard tissues and upper airway were measured by the cephalometrics before and after treatment. The data were analyzed with statistical software. Results: After treatment, U1-NA(mm) and L1-NB(mm) increased significantly in the non-extraction group (P<0.05). The U1-SN(°), U1-NA (mm), U1-NA(°), L1-MP(°), L1-NB(mm), L1-NB(°), and MP-FH(°) decreased significantly in the extraction group (P<0.05). There were no significant differences in both groups for hard tissues, upper airway, tongue, and hyoid between pretreatment and posttreatment (P>0.05). ΔU1-SN(°), ΔU1-NA (mm), ΔU1-NA (°), ΔL1-MP(°), ΔL1-NB (mm), ΔL1-NB(°) changed significantly(P<0.05). There was no significant difference between the non-extraction and extraction groups in the changes of hard tissues, upper airway, tongue, and hyoid (P>0.05). Conclusion: The effects of premolars extractionon in upper airway morphology in patients with ClassⅠhyperdivergent was limited.

Key words: classⅠmalocclusion, hyperdivergent, extraction, upper airway, obstructive sleep apnoea hypopnea syndrome