The clinical manifestation of dental fluorosis is characterized by chalky to brownish plaques on the enamel that erupted during the same period, and in severe cases, it is complicated by parenchymal defects in the enamel. Clinically, it is often divided into three types according to its mild, moderate and severe degree: chalky (mild), colored (moderate) and defective (severe). In 1931, Churchill firstly affirmed that high fluoride content in water is the cause of this disease. In the same year, Smith used fluoride for rat experiments, proving that high fluoride content can produce this disease. It is generally believed that 1ppm (1mg/L) of fluoride in water is appropriate, and this concentration can effectively prevent caries and does not cause dental fluorosis. However, there are some differences in individual factors and other living conditions, as well as in the perception of fluoride. Drinking water is one of the largest sources of fluoride intake, and the intake of water fluoride is determined by the age of the person, climatic conditions, and dietary habits. The optimal concentration of water fluoride depends on the local average annual maximum temperature, which is 0.7~1.2ppm in the U.S.A. and 0.7ppm in Guangzhou, and our country has a vast area with a big difference in temperature between the north and the south, so there can’t be only one suitable concentration. Therefore, our current water quality standard fluoride concentration of 0.5-1ppm should be appropriate. The absorption of fluoride in food depends on the solubility of inorganic fluoride in food and the content of calcium. If you add calcium compounds, the absorption of fluoride is significantly reduced. Animal experiments have confirmed that adequate amounts of vitamins A and D and moderate amounts of calcium and phosphorus can reduce the damage caused by fluoride to the body. This shows that high fluoride content is not the only cause of dental fluorosis, because not everyone in areas with slightly higher fluoride content in the water suffers from the disease. In addition, the occurrence of dental fluorosis depends on how much fluoride enters the body. Fluoride mainly damages the enamel cells of the tooth germ during enamel development, therefore, dental fluorosis can only occur if too much fluoride enters the body during the period of tooth mineralization. If before the age of 6, 7 years old, long-term living in the drinking water fluoride content of high endemic areas, even if later moved elsewhere, can not avoid the later eruption of permanent teeth involved; Conversely, such as 7 years of age before moving into high fluoride area, there is no dental fluorosis. Alkaline phosphatase can hydrolyze a variety of phospholipids, providing sufficient inorganic phosphorus in bone and tooth metabolism as raw material for bone salt formation. When fluoride concentrations increase, alkaline phosphatase activity can be inhibited, resulting in skeletal disorders such as enamel hypoplasia, undermineralization, and brittle bone. The result is poor mineralization of the intercolumnar matrix and hypermineralization of the enamel columns. This is more pronounced in superficial enamel; superficial enamel contains about 10 times more fluoride than deep enamel. Therefore, superficial enamel in dental fluorosis is porous and easily adsorbs foreign pigments such as manganese and iron compounds to produce fluorosis. The amount of microporosity in severe dental fluorosis can be as high as 10% to 25%, located between the enamel columns and distributed along the transverse lines. If the volume occupied by this porosity is large, the enamel surface collapses, forming a nested enamel hypoplasia.