Objective:To evaluate the effects of activator treatment on the development of jaw bone and dentition in juveniles with class Ⅱ division 1 malocclusion.Methods:Twenty-two patients (8 male,10～13 years old;14 female 9～12 years old) were treated with activator for 8～10 months and for more than 14 h each day,cephalograms were taken before and after treatment.The data were analyzed with Pancherz class Ⅱ correction analysis.Results:①SNA angle and ANB angle were significantly reduced(P<0.01).②Go-Me,NSL/ML and posterior vertical height were significantly increased(P<0.01).③The forward displacement of the first molar on the mandible was increased significantly (P<0.01).④The axial inclination of the upper incisors was reduced and that of the lower incisors increased significantly (P<0.01).Conclusion:The class Ⅱ correction with the activator is mainly accomplished through the reduction of the maxillary prognathism and stimulation of the mandiblllar retrognathism.%目的：探讨Activator对生长发育期Ⅱ类1分类患者的牙和颌骨的作用机制。方法：应用PancherzⅡ类错牙合矫正分析法(ClassⅡ correction analysis)结合传统测量项目对22例(男8例，女14例，年龄男10～13岁，女9～12岁)ANB角大于5°、前牙覆盖大于7 mm、磨牙完全远中或尖对尖远中关系患者的治疗前后X线头影测量分析项目进行配对t检验。结果：SNA减小，Go-Me增大， NSL/ML增大，ANB角减小，前后面高增加，下颌位置Pg/OLP前移均有显著性差异。上中切牙角变小，下切牙角度变大，下磨牙前移，磨牙关系得到改善。结论：Activator对下颌骨的矫形作用比较复杂，下颌骨的绝对长度增加，下颌平面角加大，SNB角无变化；Activator可以改善前牙的覆盖，后牙的Ⅱ类关系及Ⅱ类骨关系。
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