As people’s living standards improve, the aesthetics of their teeth are becoming more and more of a concern. Many patients have yellow teeth, or even brown or black teeth. Depending on the coloration of the teeth, the treatment varies. For lightly stained teeth with no defects, bleaching is the ideal treatment. Nowadays, there are two main types of bleaching: home bleaching and cold light whitening. Home bleaching is a transparent mold made by the doctor according to the patient’s teeth, and the patient puts the medicine into the mold by himself and puts the mold on the teeth at night when he sleeps and takes it off during the day when he goes to work, which is more convenient. Cold light whitening is to apply a higher concentration of about 30% bleaching medication to the surface of the teeth and irradiate them with cold light. This method needs to be done in the office by a doctor. There is definitely demineralization of the teeth with bleaching, but this change can recover on its own because saliva contains calcium, phosphorus and other substances that can calcify the teeth. Also the use of fluoride toothpaste promotes its calcification even more.