A, incorrect usage

The correct way to clean teeth is to cover the teeth by the side of cleaning strip, more contact area more better. Then clean the upper tooth from up to down, should clean tooth one by one.

Clean the lower tooth from down to up, should clean tooth one by one.

Besides, it is more effective to erase the tooth in the same direction than back and forth.

B, More times needed to erase stubborn tartar or tobacco teeth.

C, No obvious effects to yellow teeth caused by childhood malnutrition, long-term drinking high-fluorine water or taking tetracyclic , as well as the dental calculus .