[Changes of airway before and after Twin-block treatment in patients with mandibular retrusion].

PURPOSE: To observe the changes of upper airway and the effect of different tongue position on upper airway volume before and after Twin-block treatment in patients with Class II division 1 malocclusion and mandibular retrusion. METHODS: Thirty-three patients (ages:11.3+/-0.89) with Class II division 1 malocclusion and mandibular retrusion were included in the study and divided into 2 groups, the control group (12 patients) and experimental group (21 patients). In the experimental group, according to the tongue position shown on cone-beam CT (CBCT), the patients were sub-divided into lower tongue position group and higher tongue position group. Patients in the experimental group were treated with Twin-block appliance, and CBCT was taken before treatment and 8 months after treatment. Patients in the control group underwent CBCT at the first month and eighth month. The changes of oropharyngeal airway volume and the minimal cross-sectional area were measured by using Dolphin software. SPSS 24 software package was used for t test and one-way variance analysis. RESULTS: After 8 months, the airway volume and the minimal cross sectional area of the oropharynx in the control group were not significantly changed, but significantly increased in the experimental group (P<0.001), especially in the higher tongue position group (P<0.05). CONCLUSIONS: Twin-block can significantly increase the oropharyngeal airway volume and minimum cross-sectional area in patients with Class II division 1 malocclusion and mandibular retrusion. In addition, mandibular advancement dose not correlate with airway improvement and the right tongue position has an obvious effect on airway opening in mandibular advancement.