There are two main methods for teeth whitening: first, ultrasonic scaling and tooth surface polishing; second, cold light whitening treatment. Ultrasonic scaling and tooth surface polishing are suitable for teeth yellowing caused by exogenous staining of teeth, such as people who have the habit of smoking, drinking tea and coffee, there will be a layer of dark brown pigmentation on the tooth surface, and people with poor oral hygiene have yellow soft tartar and black tartar on their teeth. For this kind of black and yellow unattractive teeth, ultrasonic scaling can be used to remove the pigment and tartar, and then use the tooth surface polishing method to make the teeth bright and shiny, so as to achieve the effect of whitening teeth. The cold light whitening method mainly treats endogenous tooth coloring, such as age-related yellowing of teeth, tetracycline and fluorosis, which can be used to bleach the teeth and enhance the shade of teeth.