[Effect of functional appliance on upper airway in adolescent patients with skeletal Class II malocclusion]

To investigate the effect of functional appliance on upper airway in adolescent patients with skeletal Class II malocclusion based on cone-beam CT (CBCT).

Thirty adolescent patients (male:female=1:1) with skeletal Class II malocclusion and their 30 counterparts with skeletal Class I malocclusion were selected. Skeletal Class II malocclusion patients were treated with Activator for 12 months on average, meanwhile skeletal Class I malocclusion patients were treated with fixed appliance without extraction. Cone-beam CT (CBCT) films were taken before and 12 months after treatment. Films of skeletal Class II malocclusion patients were measured (items about skeletal and upper airway, and the outline of upper airway depicted with 3D reconstruction) and compared with the reference standards and the measurements of their counterpart patients with skeletal Class I malocclusion. Independent t test was performed in inter-group comparison and paired t test was performed in inner-group comparison using SAS 8.0 software package.

Before treatment, patients with skeletal Class II malocclusion showed decreased SNB and APDI value, increased ANB, Wits, and OJ compared with standard value and value of skeletal Class I malocclusion patients. In addition, decreased MPW and PAS value, and downsized volume of upper airway and transverse diameter minimum were found in skeletal Class II malocclusion patients. After treatment with Activator, patients with skeletal Class II malocclusion showed increased MPW and PAS value, and enlarged volume of upper airway and transverse diameter minimum. All values of skeletal items of patients with skeletal Class II malocclusion showed trends to get close to the reference standards and the values of skeletal Class I malocclusion patients. There was no significant difference between different genders of the two groups.

Patients with skeletal Class II malocclusion have constructed upper airways. Treatment with Activator can increase the MPW and PAS values and enlarge volume of upper airway and transverse diameter minimum. Functional appliance can ameliorate the narrowness of upper airway for skeletal Class II patients.