关键词: 推磨牙向后, 倾斜移动, 整体移动, 牙阻力中心

Abstract:

Objective:The aim of this study is to evaluate advantages and disadvantages of two types of appliances for maxillary molar distalization. Methods: Totally, 28 patientswith classÒmalocclusion resulting frommolars shiftingmesiallywere treated using two differentmolar distaliza- tion methods, including suing removable and fixed appliances. An intra-oral removable acrylic appliance with headgear for extra-oral traction resulted in tipping the maxillary firstmolars distally. The modified rapid helix expansion appliance (MRHEA), which consisted of bands, an- chorage teeth, Nance palatine bases, helix bars and connecting rods, made the maxillary firstmolarsmove parallel distally.Results: The de- sired efforts were gained in 7 or 9 months by using removable appliances, but only 2 or2.5 months if usingMRHEA. The treatment results of using removable appliances were dependent on patients.cooperation, however, the method of using fixed appliance overcame some shortcom- ings of othermolardistalization techniques, and this appliance would not lead to the distal inclination of the crown of the shifted teeth.Conclu- sion:These two methods could convert the classÒmolar relationship to classÑ. The MRHEA can save much chair-side time, and shorten the period of treatment, move molars distally parallel.

Key words: distraction, inclination movement, parallel movement, resistance centre for tooth