Objective The objective of this study is to investigate the position change of hyoid bone in obstructive sleep apnea and hypopnea syndrome（OSAHS） induced by oral appliance（OA） of double-pull rods and analyze rele- vant factors, subsequently investigate treatment mechanism of OA for OSAHS.Methods Nine OSAHS patients（male）, confirmed by polysomnography and excessive daytime sleepiness, were treated with OA of double-pull rods. After a 3- months treatment period, CT scan and three-dimensional reconstruction were made to each patient in central relation with and without OA respectively. The volume of upper airway and hyoid bone position were three-dimensional re- constructed and measured.Results After treatment with OA of double-pull rods, the hyoid bone position was obviously changed in horizontal （5.90±2.27）mm and vertical position （3.31±1.82）mm, the volume of upper airway was enlarged（32.36±14.58）%. ΔH-C3hor and ΔH-C3ver were positively related to Δvolume%（r=0.77, PConclusion The hyoid bone position significantly change after using OA of double-pull rods. Patients with smaller FH-MP have larger horizontal change of hyoid bone.
