Abstract

Objective: The aim of this study was to determine change of hyoid bone position following treatment with functional appliance in patients with class II division 1 malocclusion. Design: This study performed on pre and post treatment lateral cephalograms of 28 patients with class II div I malocclusion treated with Farmand functional appliance on average of 11 months. The range of age of girls was 10-13 years and boys 11-14 years. To study the results, t test and Pearsons correlation coefficient were used. Results: Hyoid bone shifted significantly (P.value < 0.01) forward in horizontal dimension and non significantly upward in vertical dimension. There was no significant difference between three groups in facial growth patterns with respect to hyoid bone position alterations in horizontal dimension but was significant between horizontal and vertical growth pattern in vertical dimension. (P value < 0.05). There was significant correlation between decrease of ANB angle with forward movement of hyoid bone. Conclusion: Following treatment with Farmand functional appliance, significant changes occur in the position and anterior displacement of the hyoid bone.