To investigate the three- dimensional morphological characteristics of the upper airway in children and adolescents with skeletal class Ⅲ malformation and to explore the relationship between craniofacial structure and upper airway morphology.

Ninety cases of malocclusion aged 3-18 years were collected. In addition, 45 cases of type Ⅰ and type Ⅲ were classified into three age groups with 15 cases in each group: 3-6 years old, 7-12 years old and 13-18 years old. CBCT was taken, and the scanning data of CBCT were reconstructed by the third-party software Invivo 5. The volume, minimum cross-sectional area, height and the ratio of sagittal diameter to transverse diameter at the minimum cross-sectional area of each segment of the upper airway were measured. The difference of the upper airway between skeletal class Ⅰ and skeletal class Ⅲ in each age group was analyzed and compared by group t test.

No significant differences in the upper airway indexes were noted between skeletal class Ⅰ and skeletal class Ⅲ(P > 0.05) in the 3-6 years old group. In the 7-12 years old group, the total volume of skeletal class Ⅲ upper airway (16.25 ± 3.69 cm³), nasopharyngeal segment (2.39 ± 0.90 cm³), and palatopharyngeal segment (5.24 ± 1.14 cm³) were reduced compared with the total volume of the skeletal class Ⅰ upper airway (20.98 ± 6.25 cm³) , nasopharyngeal segment (4.21 ± 1.09 cm³), and palatopharyngeal segment (8.18 ± 2.02 cm³), respectively, the differences were statistically significant (t_Vtotal＝2.526, t_Vnose＝4.999, t_Vpalate＝4.908, P < 0.05). In the 13-18 years old group, only nasopharyngeal segment volume (3.83 ± 0.90 cm³) was reduced in skeletal type Ⅰ (4.69 ± 1.34 cm³); the difference was statistically significant (t＝2.053, P < 0.05).

Age is an important factor affecting the morphology and structure of upper airway in skeletal Ⅲ malocclusion.