The degree of whiteness of teeth is related to the external image of a person. Yellow teeth not only affect the image, but also can easily lead to low self-esteem of the organism. Usually yellow teeth are caused by ageing yellow teeth, drugs and water hygiene habits, food. 1, ageing yellow teeth: with the growth of age, teeth will naturally aging, teeth will also gradually become dull yellow from bright white. This is mainly due to the human body in the process of ageing, there will be a continuous loss of minerals, causing changes in tooth color. 2, drugs and water quality: the body for a long time to take tetracycline drugs can easily cause tooth discoloration. And in some areas due to poor water quality, the water contains high fluoride, long-term drinking will also lead to yellow teeth, usually daily brushing is unable to remove the pigment buried in the deeper layer of the teeth, only through special methods to restore white teeth. 3, hygiene habits: If you do not pay attention to oral hygiene in daily life, do not develop good habits, usually after chewing food, food residues will remain on the surface of the teeth, after bacterial fermentation, can produce some acidic substances, resulting in tooth corrosion and yellow teeth. 4, food: food is the main cause of yellow teeth, some colored food, such as cola, red wine, coffee, tea, these substances can produce some chemical substances closely covered in the original white teeth to make it discolored. Usually yellowing of teeth is usually caused by the above-mentioned reasons, and it is recommended to go to regular dentist for regular health care.