The main cause of dental fluorosis is the excessive intake of fluoride during early childhood, usually before the age of seven in areas with high fluoride, which causes changes in the development of enamel cells, resulting in chalky white or yellowish-brown enamel and even enamel development defects. Clinically, it is common to see yellow or chalky spots on teeth, especially incisors, and even partial loss of teeth. Mild dental fluorosis is characterized by chalky changes in the teeth, with some white spots on top. Moderate fluorosis shows yellowish-brown spots, which can exceed 1/2 of the tooth surface or even cover the tooth surface. Severe dental fluorosis is diagnosed by yellowish-brown color change of the teeth, and even the presence of dental tissue defects.