The Study Of Twin-Block And Activator Appliances On The Structural Change Of Class Ⅱ Upper Airway In Adolescence

Objectives: To observe the changes of upper airway diameter and hyoid position before and after functional correction with Twin-Block and Activator appliances in adolescents with skeletal type Ⅱ mandibular retraction,and to evaluate the improvement of upper airway diameter and hyoid position in patients with skeletal type II mandibular retraction.Method: Thirty patients with non-high angle and mandibular retraction at the peak of growth or the previous year(CVS2-3)were randomly divided into two groups.Fifteen patients in the first group wore Twin-Block appliance(TB group)and 15 patients in the second group wore Activator appliance(AC group).The X-ray lateral cephalometric films of the two groups before and after correction were analyzed and compared.The sagittal diameter of upper airway,shape of soft palate and hyoid position were measured.The cephalometric analysis was carried out by SPSS statistical software.The changes of upper airway shape and hyoid position before and after treatment were compared by paired t test.The differences of upper airway shape improvement between the two functional appliances were compared by independent sample t test.Results: The velopharyngeal segment diameter(Ve1-Ve2,P1-P2),glossopharyngeal segment diameter(Pas1-Pas2),hyoid position(AH-CVP,AH-NP,AH-MP,AH-Or,AH-RGn)of the two groups were corrected.There were significant differences(P< 0.05),but there were no significant differences in nasopharyngeal segment diameter(PNS-S,PNS-Aa,PNS-adl,PNS-ad2),laryngopharyngeal segment diameter(Va1-Va2),soft palate shape(PNS-P1,Sp1-Sp2),hyoid position(AH-FH,AH-SN,AH-PP,AH-PNS).The comparison of the two groups showed that Ve1-Ve2,Pas1-Pas2 and AH-MP had statistical significance(P < 0.05),while the other indicators had no statistical significance.Conclusion: Both Twin-Block and Activator appliance can enlarge the upper airway oropharyngeal segment(posterior soft palate space,posterior soft palate apex space and sagittal diameter of posterior lingual root space),upgrade and move the hyoid bone forward,relieve the obstruction point of upper airway,improve the ventilation function and sleep quality of patients.Compared with Activator appliance,Twin-Block appliance can improve the sagittal diameter of posterior soft palate space and posterior lingual root space in adolescent patients with skeletal type II.It will provide data support and guidance for the selection of functional orthodontic appliances of bone type II in adolescence in future clinical diagnosis and treatment.