One miniscrew of experiment group was placed with intentional root contact with upper third premolar, and 1 of control group was placed without root contact at the contralateral side.

• 对照组植入迷你骨钉1支于对侧同样部位，但使迷你骨钉不与牙齿牙根接触。并拔除上颚两侧第二小臼齿。