为了脱身，其余的壳就会以逆时针方向绕着牙齿旋转。
The rest of the shell is rolled towards the tooth in an anticlockwise direction, in order to remove it.
英格兰莱切斯特大学的古生物学家Mark Purnell和同事们在埃德蒙顿龙的牙齿上发现了四组不同方向的纹路。
Specifically, paleontologist Mark Purnell of the University of Leicester in England and his colleagues found four sets of striations oriented in different directions on the teeth of Edmontosaurus.
牙线紧紧地贴着牙齿，往上向远离牙龈的方向移动，再沿着牙齿邻面向下移动，把这个动作跟牙线的前后移动组合在一块。
Hold the floss tightly against the tooth, and move it away from the gum. Slide it firmly down the tooth surface, combining this with a back-and-forth motion.
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