There are many reasons for yellowing of teeth, such as the problem of tooth quality itself, as well as dental calculus, smoking and drinking tea, medication and living area, etc., which may cause yellowing of teeth. 1. Yellowish teeth: Some people have yellowish teeth, so their teeth will look a little yellow. 2. Dental calculus: If there is calculus on the teeth, or if there is a plaque problem, it will easily affect the color of the teeth and appear yellowish. 3. Smoking and tea drinking: people who often drink tea or have the habit of smoking are also prone to yellowing of teeth due to pigmentation. 4. Drug reasons: some people take tetracycline during childhood, which causes tetracycline to be deposited on the dentin, thus making the teeth yellow and black. 5. Living area: If the water in the area where you live has a high level of water fluoride in the childhood stage. It is easy to cause dental fluorosis, mainly because the fluorine pigment destroys the enamel, resulting in yellowing of the teeth. It is recommended to change bad habits, such as quitting smoking, pay attention to maintaining oral hygiene, you can regularly go to the hospital stomatology department to do dental cleaning, which can effectively remove dental calculus, improve the problem of yellowing teeth.