Tooth bleaching is applicable to a wide range of teeth, such as pigmentation, tobacco spots, wine spots, fluorosis, tetracycline teeth, dead pulp teeth and other teeth color abnormalities, can be improved by bleaching. Since tooth bleaching uses the oxidation reduction effect of drugs to bleach yellowed teeth to white. Redox bleaching agents such as strong acids can penetrate along the surface of the teeth to the inside of the teeth and stimulate the pulp, causing congestion and swelling of the pulp, resulting in pulpitis. During the bleaching process, the bleach solution penetrates into the surrounding gums and other soft tissues, causing burns, recession and pain in the gums. Frequent bleaching of teeth can aggravate the irritation of pulp and periodontal tissues, as well as extra-root resorption. The effects of dental bleaching agents do not last long and teeth usually regain their original color after 1-2 years. Besides, during the process of tooth bleaching, tooth sensitivity and soreness may occur, which is a normal phenomenon and can be relieved by using desensitizing toothpaste. It is worth noting that tooth bleaching is not a permanent solution. After tooth bleaching, the tooth color will return to different degrees, but the tooth bleaching effect can be maintained at a stable level within 1-3 years. After the color has returned, re-bleaching will work 5-7 times faster than the original.