Tooth decay is also called dental caries, which is mainly caused by the loss of tooth minerals and the damage of dental tissues due to the fermentation of food residues by bacteria in the plaque accumulated on the tooth surface. There are several methods to judge tooth decay as follows: 1.Change of tooth color: Observe carefully whether there is any abnormal change of tooth color in the mirror, especially at the sulcus of the biting surface and the lip and tongue surface of the teeth, the gap between the two teeth of the front teeth, and the color of the lip and cheek surface of the teeth. If the color is ink-dipped, it is possible that the tooth has been decayed; 2.Change of tooth form and texture: the hard tissue of the tooth with decay will decalcify and become soft, and the surface will become incomplete, with holes or small pieces falling off; 3.Change of tooth surface cleanliness: the tooth surface often has pigmentation that cannot be removed by brushing; 4.Self-perceived symptoms: when encountering hot and cold stimulation or eating sweet and sour food, there is sore and uncomfortable feeling. Under normal circumstances, healthy adults are recommended to visit the dentist twice a year for oral health checkups. However, if the above symptoms occur, it is recommended to seek medical treatment promptly, and the dentist will carry out fluoride treatment, filling or tooth extraction according to the situation. Early treatment can prevent the caries from continuing to develop, which may damage the pulp nerve and cause pulpitis or apical inflammation.