Changes in airway dimensions and hyoid bone position following class II correction with forsus fatigue resistant device

The objective of this study was to investigate the effects of fixed functional therapy on oropharyngeal airway dimensions and hyoid bone positions in Class II patients and make comparison with an untreated Class II group. Eighteen patients (8 girls, 10 boys; mean age 13.62 +/- 1.92 years) who were treated with Forsus Fatique Resistant Device (FFRD) and 19 patients (11 girls, 8 boys; mean age 12.74 +/- 0.91 years) who served as control were enrolled. Cephalograms were used to assess linear, angular, and area measurements. Intragroup comparisons were made by paired t and Wilcoxon tests and intergroup comparisons were performed by independent t test. With respect to controls, FFRD group showed increased airway dimensions at soft palate (P < 0.05) and more forward positioning of the hyoid bone (P < 0.05). Dentoalveolar changes exhibited mesial movement of lower incisors and molars and reduction in overjet (P < 0.001) in FFRD group. Positive effects in oropharyngeal airway dimensions and increased values of hyoid bone displacement to a more forward position were found after fixed functional therapy. Treatment with fixed functional appliances is mostly based on mesial movement of mandibular dentition, which might influence changes in tongue posture. The present results might indicate that oropharyngeal airway dimensions may be affected by postural changes of the hyoid bone in consequence of dentoalveolar changes. Clinically, these may be considered especially in Class II cases with reduced airway dimensions.