The development of tooth decay is fast and slow, tooth decay is also called worm tooth, professionally it is called dental caries, the development speed of dental caries is related to the nature of the caries itself. Clinically, there are acute caries, also called fierce caries and wet caries. This kind of caries often occurs in the milk teeth and young permanent teeth, and the development of this kind of caries is relatively rapid, from the first detection to the invasion of the whole tooth, it may only take a few months. But clinically there are also relatively chronic caries, such as adult chronic caries, this kind of caries from the first detection on the tooth surface to the gradual expansion, may 1-2 years will not expand to deeper parts, so for the caries there are fast and slow.