Lateral force can not brushback and forth otherwise they will damage gums.
不可横向来回用力刷,否则会损伤牙龈。
2
Big diameter pipe can be composed of several round steel brush together, at both ends with wire tightly, within the lumen pull brushback and forth, until the metal color, reoccupy cotton brush clean.
Brush on the origin of different in history, said the most recorded in history is the story of Penpower brush making, but modern scholars believe that there is a brushback in Penpower existed before.