As the plaque gets harder and thicker, it becomes what is known as dental calculus or tartar, a hard calcified layer that is irtually impossible to shift with normal brushing, you would hae to get the dental hygienist to do it.

• 菌斑变硬增厚，即形成所谓的牙垢或牙石，它是一层很硬的钙化层，一般不能通过刷牙去除，必须得请牙医处理。