The tetracycline family of drugs, taken during the developmental mineralization of the tooth, can be bound into the dental tissue and stain the tooth. Since enamel and dentin are formed simultaneously on opposite sides of a basement membrane, the same dose can form a yellow layer in both tissues; however, deposition is four times higher in dentin than in enamel, and only diffuse, non-banded pigmentation is present in enamel. This is due to the fact that dentin apatite crystals are small and have a larger total surface area than enamel apatite crystals, thus allowing the dentin to absorb far more tetracycline than the enamel. Because the yellow layer is wavy and cap-like, roughly resembling the shape of a tooth, the staining caused by a single dose can be seen on most of the surface of a tooth; whereas long intervals of repeated doses do not appear as interval horizontal staining. Along with tooth staining, there is also staining of the bone tissue, but the latter can be gradually removed with the physiological metabolic activity of the bone tissue; however, all tooth staining is permanent. In addition, tetracycline can also cause staining of milk teeth in the mother through the placenta. The main effect of tetracycline on teeth is staining, sometimes combined with enamel hypoplasia. Due to the chelating nature of the tetracycline molecule, it forms a solid tetracycline orthophosphate complex with dental tissue, which inhibits the growth of the two upper phases of mineralization, i.e. nucleation and crystallization. The degree of influence of tetracycline on tooth staining and enamel hypoplasia is related to the following factors: (1) the color of the tetracycline family of drugs themselves, e.g., cadmium yellow for demethylchrysin and lemon yellow for hygromycin. (2) The color presented by degradation of tetracycline, because tetracycline is sensitive to light and can discolor under ultraviolet light or sunlight. (3) Tetracycline in the dentin, the degree of dentin coloration varies depending on the depth of the binding site, when the coloring zone is closer to the enamel dentin boundary, the easier to color, therefore, in early infancy, the formation of the outer layer of dentin, the greatest impact of the drug. (4) with the structure of the enamel itself, in severe enamel hypoplasia, enamel completely lost, the coloring dentin obviously exposed; if mild enamel hypoplasia, enamel loss of transparency and chalky white, can cover the coloring dentin, but make the tooth color close to normal. What are the manifestations of tetracycline teeth and how to diagnose? 1.History The teeth have been treated with large doses of several short courses of medication (tetracyclines) before the age of 6-7 years. 2.Clinical manifestations Teeth are yellowish light gray or dark gray, generally the coloring of anterior teeth is more obvious than that of posterior teeth milk teeth than permanent teeth. In severe cases, there is enamel hypoplasia. 3.Differential diagnosis The excitation fluorescence can be observed by irradiating the tetracycline teeth with UV light, which can be distinguished from the hereditary papillary dentin. Clinical manifestation】 1, yellow, in the sunlight, then show bright yellow fluorescence, and then gradually from yellow to brown or dark gray. This transformation is slow and can be promoted by sunlight, so the labial surface of incisors is the first to change color. 2, front teeth than back teeth coloring obvious; milk teeth coloring and more obvious than permanent teeth, because the enamel of milk teeth is thinner and more transparent, not easy to cover the color of tetracycline bond in dentin. 3, the degree of tooth coloring is related to the type of tetracycline, dose and the number of dosing. It is generally believed that tetracycline shrinkage, norethindrone and tetracycline hydrochloride cause more obvious coloring than hygromycin and chlortetracycline. In permanent teeth, the number of courses of tetracycline is positively related to the degree of staining, but a large dose taken in a short period of time has a greater effect than an equal total dose given over a long period of time. 4, tetracycline causes tooth staining and enamel hypoplasia, both of which are only apparent when administered during tooth development. Generally speaking, after the age of 6 to 7 years old, the drug will not cause striking tooth discoloration. What diseases can complicate tetracycline teeth? It can cause enamel hypoplasia. Enamel hypoplasia is a disease in which the tooth structure is abnormal. It is the result of a disorder in the formation of the enamel matrix. The causes of enamel hypoplasia: there are nutritional deficiency factors, especially vitamins C and D have the greatest influence; endocrine factors, infant and maternal diseases, such as pediatric measles and scarlet fever. Rubella and toxemia suffered by the mother during pregnancy can also make the enamel formed during this period incomplete.