Then tie power chain or elastic line on the hook and bracket (or band) to form two identical rotated strengths, but in opposite direction, to help correct torsiversion.
在拉钩与托槽或带环上分别挂橡皮链或弹力线形成一组方向相反、力量相等的旋转力作用于扭转牙达到矫治。
3
Roller chain models are available only in hook suspension.