[Changes of hyoid bone position following treatment of class II div1 malocclusion with Farmand functional appliance]

Unlike other bones of the head and neck, hyoid bone has no bony articulations. It is connected to mandible, cranium and pharynx through muscles and ligaments. During treatment with functional appliance in patients with class II div1 malocclusion, mandible is positioned in inferior and anterior direction. Regarding the relation between hyoid and mandibular bone, alterations of hyoid bone position can be a result of functional appliance therapy. The aim of this study was to evaluate the changes of hyoid bone position following treatment with Farm and functional appliance in patients with class II div 1 malocclusion. In this before-after clinical trial, 28 patients with class II div 1 malocclusion which were under treatment with Farm and functional appliance for 11 months were selected. Facial growth in vertical, normal or horizontal direction was determined by cephalometric measurement. Data were analyzed with Paired-t test to compare the differences of mean values pre and post treatment. Variance analysis was used to compare the three growth patterns. P<0.05 was considered as the limit of significance. Hyoid bone shifted significantly forward in horizontal dimension [P<0.01] and non-significantly upward in vertical dimension. There was no significant difference among the three studied groups with respect to hyoid bone position alterations in horizontal dimension but significant difference was observed between horizontal and vertical growth pattern in vertical dimension [P<0.05]. There was significant correlation between decrease of ANB angle and forward movement of hyoid bone. Based on the results of this study, treatment with Farm and functional appliance [Fa II] leads to significant alterations in the position and anterior displacement of the hyoid bone

[Changes of oropharynx space and posterior surface of the tongue following treatment with farmand functional appliance]

During treatment with functional appliance in patient with class II division I malocclusion, mandible is postured inferiorly and anteriorly. Considering the relation between mandible with tongue and oropharynx space, functional appliance therapy can alter the tongue position and oropharynx space. This study aimed to determine the changes of oropharynx space and posterior surface of the tongue position following treatment with Farmand functional appliances in patients with class II division I malocclusions. In this clinical trial study, 28 pre and post treatment cephalometric radiographs of patients with class II division I malocclusions were investigated. The age rang of females was 10-13 years and in males it was 11-14 years. The patients were treated by Farmand functional applicne for 11 months. McNamara analysis and some linear variables were used to determine the positional changes of tongue and oropharynx space. Paired-t test was used to compare the pre and post treatment differences of mean values. Variance analysis was used to compare the growth patterns of the patients. Tongue moved significantly forward [p<0.001] but non-significantly downward. Oropharynx space increased significantly in sagittal dimension [p<0.001]. There was a significant correlation between decrease of ANB angle with forward movement of tongue [p<0.05] as well as with the increase in extent of oropharynx space in the sagittal dimension [p<0.05]. Treatment with Farmand functional appliance showed significant alteration in tongue position and as a result, increased the extent of oropharyngeal space