During the mineralization period of the teeth, if tetracycline drugs are taken, the drugs can bind to the dental tissues to stain the teeth. The embryo of the milk tooth occurs at 2 months of embryonic life and mineralization begins at 5-6 months. The first permanent molars, which are the first to develop, occur at 4 months of embryonic life, and the first permanent molars are mineralized before the birth of the newborn, and all permanent teeth except wisdom teeth are mineralized by the age of 5. Tetracycline is deposited on the teeth, initially in yellow, then in bright yellow fluorescence under sunlight, and later gradually from yellow to brownish gray, this transformation is slow and can be facilitated by sunlight, so the incisal labial surface is most susceptible to discoloration. At the same time of tooth coloring, bone tissue is also colored, but the latter can be gradually removed with the metabolic activity of bone tissue coloring, however, the tooth coloring is permanent. Tetracycline can cross the placental barrier of the mother, so if the mother has taken tetracycline after the second trimester of pregnancy, the deciduous teeth can also be involved. Tetracycline is a broad-spectrum antibiotic catalyzed by the dehalogenated biosynthesis of chrysomycin, mainly tetracycline shrinkage (rarely used in China), desmethyl chrysomycin, tetracycline hydrochloride, oxytetracycline, chrysomycin, etc., with a wide spectrum of bacterial inhibition, which began to be used in clinical practice as early as 1948, and tetracycline drugs causing tooth staining were reported abroad in 1950. Later, it was reported that tetracycline was deposited in teeth, bones, and nails, and could also cause tooth enamel hypoplasia. In the 1970s, this aspect of the disease was not given much attention in China. Tetracycline causes tooth staining and enamel hypoplasia, which are only apparent when administered during the developmental period of teeth. Tetracycline can cause tooth staining and sometimes enamel hypoplasia due to the chelating nature of the tetracycline molecule, which can form stable orthophosphate complexes with dental tissues, which can inhibit both the nucleation and crystal expansion processes of mineralization, leading to mineralization hypoplasia. Enamel defects are produced.