用方丝弓拔牙矫治病例中 ,通常拔除第一前磨牙。在排齐前牙或内收切牙、减小前牙覆盖之前 ,需先使尖牙向远中移动 ,除采用闭隙垂直曲外 ,多数采用橡皮圈、橡皮链的拉力来达到此种目的[1] 。近年来 ,由于高弹性镍钛丝在固定正畸中的应用[2 ] ,尤其镍钛螺旋弹簧的使用 ,给固定正 With the square arch extraction treatment cases, the first premolar removal is usually removed. Before aligning the anterior teeth or adduction and incisors to reduce the coverage of the anterior teeth, the fangs should be moved first to the far. In addition to adopting the vertical curve of the closed space, most of them adopt the rubber band and rubber chain tension to achieve this purpose [ 1] . In recent years, due to the application of highly elastic nickel titanium wire in fixed orthodontics [2], especially the use of nickel-titanium coil springs, to fixed positive