Knocking effect and function is can be strong teeth, promote digestion. 1. Strong teeth: knocking can promote the periodontal membrane, pulp cavity and periodontal blood circulation, increase the supply of nutrients to the teeth, so that strong teeth, not easy to have caries and so on. In addition, the biting muscle is not easy to atrophy, cheeks are not easy to collapse, chewing is more powerful, teeth are not easy to fall off and loose. 2. Promote digestion: saliva contains amylase, lysozyme and secretory antibody immunoglobulin and other substances, not only can help digest food, but also has sterilization, antivirus and other detoxification effect. Knocking should not be too strong, if the strength is too big to damage the teeth, it is easy to cause the surface of the teeth to appear a slight hidden crack. The frequency of knocking should be decided according to the individual’s oral condition.