Using 80g force to make the first molar mesial movement. 动物模型的建立:以兔上颌切牙为支抗牙,80g力拉上颌第一磨牙向近中移动。
Before ⅲ B period the first and second premolar of maxillary have made distal movement, but to stop in ⅲ B period, and slightly to mesial movement trend. 上颌第一第二前磨牙在ⅢB期以前都向远中运动,但到ⅢB期牙齿停止运动,并有略向近中运动的趋势。