Abstract: Objective: To analyze alterations of upper-airway morphology after nonextraction treatment of skeletal class Ⅱ malocclusion adolescent patients. Methods: Fifteen adolescent cases of skeletal class Ⅱ malocclusion receiving nonextraction treatment were selected, who were taken cephalometric radiograph and cone beam computed tomograph before and after orthodontic treatment. Then, Dolphin 11.5 was used to take 3D measurements. The alternations of upper-airway and cephalometric values were analyzed. Results: After the nonextraction treatments, the changes of other measure projects of cranio-maxillofacial were not significant different, except labial inclination of lower incisors (P<0.05). The width of upper-airway sagittal osseous nasopharynx increased (P<0.05), and the change values of total cross area of upper-airway, smallest cross area of oropharynx, and cross area of nasopharynx, palatopharynx and glossopharyngeal were not significant. The volumes of upper-airway, palatal pharyngeal and the glossopharyngeal significantly increased (P<0.05). Before and after treatment, the overlaps of Cone beam CT indicated that after the nonextraction treatments, the patients' chin had grown forward, while the whole upper-airway had grown backward. Conclusion: For the nonextraction treated adolescent skeletal class Ⅱ patients, craniofacial patterns keep the pre-treatment growth modality, significant forward growths of chins arise, and the patients' faces improve significantly. The therapy would enlarge the upper-airway, improve respiratory function to a certain extent, and the upper-airway grows entirely backward.

Key words: Cone beam computed tomography , Upper-airway, The skeletal class Ⅱ, Nonextraction therapy