关键词: 直丝弓, 滑动法, 关闭曲法, 拔牙, 支抗

Abstract:

Objective    To compare the differences between closing loop and sliding technique in anchorage demand and treatment time. Methods    Totally 33 cases of Class Ⅱ division 1 or Class Ⅰbimaxillary protrusion malocclusion，who were treated by 4-premolar-extraction or 2-premolar-extraction，were selected and divided into two groups randomly. In all cases，the second maxillary molars were bonded at the beginning of treatment and no special method was used to improve the anchorage. The 0.46 mm straight wire appliance and two-step method were used. After the alignment and leveling as well as the retraction of canine，closing loops were used in one group（16 cases）and sliding technique was used in the other group（17 cases）for incisor retraction. Cephalometric films before and after treatment were taken and analysed. Results        The first maxillary molar moved mesially for（3.4 ± 1.4）mm and（3.0 ± 1.8）mm in sliding technique group and closing loop group respectively. There were no significant differences between the two groups（P > 0.05）. The time of incisor retraction was（6.0 ± 2.4）months and（6.4 ± 2.2）months in sliding technique group and closing loop group respectively. The difference was not significant（P > 0.05）. Conclusion    Orthodontic doctors could use closing loop or sliding technique according to personal habits in space closure with two-step method，using 0.46 mm straight wire appliance while the second maxillary molar is bonded at the beginning of the treatment.

Key words: straight wire；sliding technique；closing loop；extraction；anchorage