Teeth will not turn yellow after demineralization and fluoride application. Yellowing of teeth can be caused by dental caries, dental fluorosis, pigmentation, plaque buildup, etc., which need to be treated according to the cause of the disease. 1. Dental caries: when dental caries, food debris, smoke, etc. can make the carious parts of the exogenous coloring, thus presenting a brownish-yellow color. At this time, it is necessary to carry out restorative dentistry as soon as possible to avoid the continued expansion of the lesion and the involvement of the pulp. 2. Dental fluorosis: If the intake of fluorine is too much before the age of 6-7, it can lead to poor mineralization of the teeth in the development and mineralization period, and some people’s teeth can be accompanied by etching, brown staining, enamel defects and other phenomena. In addition, fluorosis enamel surface layer has porosity, easy to adsorb foreign pigments, resulting in fluorosis, so that the teeth are yellow. 3. Pigmentation: Eating darker pigmented food regularly, such as tea, coffee, berries, etc., can make the food pigmentation deposited on the teeth, making the teeth yellow. You should pay attention to clean your teeth after eating and drinking, and you can improve the coloring situation by ultrasonic cleaning and sandblasting. 4. Accumulation of plaque: If you don’t pay attention to oral cleaning, the accumulation of plaque on the teeth or the formation of dental calculus, etc., can make the teeth yellow, and accompanied by oral odor. Can be improved through daily oral hygiene, for those who have calculus can be on the gingival cleaning, subgingival scraping and other methods to remove. When the teeth become yellow, it can be improved by paying attention to oral hygiene, and if it is not improved, it is recommended to consult the dentist in time.