| Summary: | Introduction: Obstructive Sleep Apnea Syndrome (OSAS) regulate pharyngeal airway volume. Forward displacement of mandibular repositioning appliances has advantage over an improvement of pharyngeal airway space and a change in the hyoid bone position. This study aims to assess the changes in the pharyngeal airway dimensions and hyoid bone position in growing individuals with retrognathic mandible treated with Fixed Twin Block (FTB) and Forsus Fatigue Resistant Device (FRD) to correct the skeletal Class II pattern. Materials and Methods: 40 skeletal Class II pattern patients were included in the study, to assess the pharyngeal airway space at three levels, upper pharyngeal width (UPW), middle pharyngeal width (MPW), and lower pharyngeal width (LPW). Hyoid bone measurements were Vertical dimension H-HOR and Horizontal dimension was H- VER. The study patients were divided into three groups and in each group 20 patients. Group-A treated with FTB appliance and Group-B treated with Forsus FRD appliance and Group C served as control group. At pre and post functional treatment condition, lateral cephalograms were evaluated. Results: Cephalometric analysis revealed a significant increase in the mean change of MPW (P = 0.005) between the FTB and the control group. There was significant, mean change seen of pre, post UPW, mean change of MPW over groups (P<0.01). Statistical significant difference was noted in the mean change of mandibular corpus length over groups and also when compared with FTB-Control (P<0.01). A significant difference in the mean change of the mandibular unit length, premandibular corpus length over the groups was noted. Conclusion: The FTB appliance was more effective in correcting the skeletal class II malocclusion as compared to the Forsus FRD appliance and therefore, there was marked improvement in the oropharyngeal airway dimensions (UPW, MPW) and hyoid bone displacement (anterior and superior).
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