Tooth decay is manifested as a small black hole on the tooth which seems to be bitten off by insects, so it is commonly called “worm tooth”. The caries has nothing to do with bugs. There are many reasons for tooth decay, which may be related to the body factor, food factor and bacteria factor. For example, some people inherit the condition of teeth and mouth from their parents, so they are easy to suffer from tooth decay; some of them in the fetus or in the infant period after birth, due to the lack of some raw materials needed to form teeth in the mother’s or infant’s food, such as vitamin A, C, D, minerals calcium, phosphorus, trace elements fluorine, etc., so that the tooth structure is defective and easy to be affected by other unfavorable factors; children’s teeth do not grow up When children’s teeth are not neatly grown, they can easily hide food residues and bacteria, which creates the conditions for the occurrence of dental caries; furthermore, the nature of saliva and certain diseases of the body can affect the internal and external environment of teeth, which constitute the factors prone to the occurrence of dental caries. The occurrence of dental caries is produced under the combined effect of the above factors. The carbohydrates in food, especially sugar, remain in some places on the surface of teeth which are not easy to remove, providing nutrition for bacteria and making them multiply, and at the same time decomposing the food residues by decaying them, producing acidic substances and chemical reactions on the tooth surface, causing decalcification on the tooth surface, forming tooth defects and cavities. Of course, if the bacteria or food stay on the tooth surface for a very short time and can be removed in time, then it will not form caries. Therefore, scholars also consider time as one of the factors of caries. When the caries reaches the dentin, the tooth pain will occur when eating sweet, sour, hot or cold food; if not treated in time, the caries will continue to develop, and when the bacteria invade the tooth pulp (commonly known as dental nerve), the spontaneous pain will appear, especially the night pain at night, making people restless and unable to sleep at night, which is often said that “toothache is not a disease, but pain is fatal”. This is the symptom of pulpitis, which is often said as “toothache is not a disease, but pain is fatal”. When the cavity becomes bigger and bigger, the whole tooth will be rotten. The broken teeth will affect the chewing and digestion; affect the normal replacement of teeth and cause the misalignment of teeth. In addition, if the pulpitis is not treated, it will secondary to the periapical inflammation of teeth and form chronic periapical inflammation, which not only makes the gum swell and pain frequently, but also the jaw bone resorption occurs, and because the bacterial infection can affect the health of other organs of the body, such as causing diseases of joints, heart and kidney organs. Therefore, once you suffer from tooth decay, you should not take it lightly and should treat it timely.