Tooth decay, commonly known as “worm teeth”, is due to the decalcification, softening and destruction of hard tissues of teeth, and finally form cavities. When the caries is superficial and there is no symptom yet, the treatment is very simple, if not filled in time, the caries will be more and more serious from superficial to deep, from small to big, and can be sensitive to cold, hot, sour, sweet and other food stimulation; when the lesion reaches the pulp, the patient will have severe pain, and the pain is aggravated at night because of the change of position, which affects the normal work and life, and the treatment is more troublesome, the nerve of the tooth must be killed first, and then it can be filled. If the lesion is not treated in time, it will cause periapical inflammation, periapical abscess, and even loose and fall off teeth, so the treatment of worm teeth is better as soon as possible, and it is better to fill the cavity when there is no symptom. In order to detect the worm teeth without symptom once a year, early detection and early treatment can stop the development of carious lesion and avoid the premature loss of teeth.