Black things on teeth are not necessarily cavities, may be the occurrence of the following: First, long-term tea, coffee or smoking and other exogenous pigments will be deposited on the tooth surface, hard and relatively smooth texture, can be removed through ultrasonic cleaning and sandblasting; Second, when suffering from tetracycline teeth or fluorosis, the tooth surface to form a dark brown plaque, superficial lesions can be removed by gold steel sand car needle grinding, seriously affect the aesthetic All-porcelain veneer bonding and restoration can be made. Third, long-term accumulation of food residues and soft scale will form black calculus in the cervical part of the teeth, which can be scraped away by manual instruments; Fourth, tooth decay occurs when the black area forms an obvious cavity and the X-ray shows a lower density than the surrounding tooth tissue.