Immediate Effect of Twin Block Appliance on the Airway on a Sample of Patients with Class II division 1 Malocclusion on Skeletal II Base

There is a background relationship between the mode of breathing and antero-posterior jaw relation. Severe mandibular deficiency has been linked to reduced oropharyngeal airway dimension. Dental literature reported many studies on functional appliances and their effects, but there are few published studies on their effects on the airway. Objectives: To investigate the immediate effect of the Twin block (TB) functional appliance on the airway in patients with class II division1 malocclusion on skeletal II base and to measure the immediate changes in the position of the hyoid bone after insertion of the TB appliance. Materials and Methods: Two lateral cephalometric radiographs were taken and analyzed one before and one after insertion of the TB appliance for the 19 patients. The age range 10-14 years. Immediate change in the airway was performed by measuring the changes in the vertical position of the hyoid bone relative to the mandibular plane (H1) and to the (cv3-RGN) plane (H2). The change in the airway can be measured by the change in the vertical position of the hyoid bone before and after insertion of TB appliance (H-H1 ) + (H-H2 ). Results: The hyoid bone changes in a more superior position after the insertion of the TB appliance. The mean change was 11.8mm, with SD 2.8mm (P = 0.0001) at 0.01% level. Conclusion: Vertical hyoid bone position was changed in a more superior position immediately after the insertion of the TB appliance on patients with class II division 1 malocclusion on skeletal II base. Further, the TB has an immediate positive effect in the airway