Four first bicuspids of every patient were extracted and all patients were treated with the Alexander technique. The study casts were taken before(T_1), after treatment(T_2) and 27.8 months averagely follow-up(T_3).

• 设计减数4个第一前磨牙；采用亚历山大矫正技术；对矫治前(T1)、矫治后(T2)及保持结束后平均27.；8个月的观察期(T3)内的模型进行测量。