The causes of tooth staining, yellowing and blackening are generally divided into exogenous and endogenous: exogenous staining has a variety of causes, most of which are caused by plaque, pigment-producing bacteria, beverages and food attached to the tooth surface. Frequent consumption of beverages such as coffee and cola, as well as incomplete brushing of nociceptors and melanin-producing rods, can lead to tooth staining. The etiology of endogenous staining varies depending on the eruption of the tooth. Before tooth eruption, systemic diseases such as infantile hyperbilirubinemia and tetracycline drug application can affect tooth embryonic development and hard tissue formation leading to staining; after tooth eruption, chemical substances, trauma, and antibiotic use can also cause endogenous tooth staining. In Xuzhou area, due to geographical and historical reasons, the most common one is fluorosis tooth staining. The typical clinical manifestation of dental fluorosis is chalky to brown patches on the enamel of erupting teeth at the same time, and in severe cases, complicated by parenchymal defects of the enamel, usually seen in permanent teeth. Exogenous staining needs to be restored to the original shade of the tooth usually by scaling and sandblasting. Endogenous staining, on the other hand, is often accomplished by chemical bleaching or masking whitening. The biggest advantage of chemical bleaching is that it does not require wear and tear on your teeth, but the disadvantage is that the bleaching effect is limited and is usually used for mild to moderate tooth staining. Masking whitening includes porcelain veneers and various crown restorations (porcelain crowns, all-porcelain crowns). The advantage of masking whitening is that the whitening effect is good, the degree of tooth color can be controlled and there is no rebound, the disadvantage is that there are different degrees of wear and tear on one’s teeth. Several commonly used whitening methods: 1, home and in-clinic drug bleaching usually uses bleaching agents such as peroxide urea to bleach outside the mouth or into the root canals of the teeth by placing them in special brackets to absorb into the enamel and then oxidize the pigment in the teeth for intra-dental bleaching. This method is not effective for heavy fluorosis and tetracycline teeth, and some patients may have tooth sensitivity side effects, but these side effects are short-lived and reversible, and this type of bleaching is safe and effective. 2.Laser whitening It is the use of higher concentrations of bleaching agents to enhance and accelerate the bleaching effect of peroxide for teeth whitening, which can selectively act on the pigment particles deposited on the teeth to bleach the organic pigments in the teeth from the carbon ring structure to the hydrophilic non-pigment structure; at the same time, the light-absorbing macromolecules in the tooth structure are broken into small molecules, so that they no longer absorb light and discolor, thus achieving a safe whitening The effect of the treatment is safe. The appropriate dose of laser irradiation can simultaneously close the dentin tubules, reduce the permeability of dentin and reduce the symptoms of dentin sensitivity in the process of tooth bleaching. 3.Cold light whitening The principle of cold light whitening is to use the instrument to transmit the high-intensity blue light with wavelength between 480-520nm through more than 12,000 optical fibers with a total length of more than one mile, and filter out all harmful ultraviolet and infrared rays through two optical lenses with more than 30 coatings, and then irradiate the special whitening agent applied on the teeth to make the whitening agent pass through the dentin tubules in the shortest possible time. In the shortest time, the whitening agent passes through the dentin tubules and produces oxidation reduction with the pigments that have been deposited on the surface and deep in the teeth over the years, making the teeth white. The main components of the whitening agent are hydrogen peroxide and silicon peroxide with a diameter of 20nm or less. 4.Porcelain veneer refers to the whitening of the surface of the discolored teeth by grinding away the surface layer and then attaching the all-porcelain veneer to the tooth surface with a highly effective resin bonding agent. The color of porcelain veneers can be decided according to the patient’s own conditions and desires. Porcelain veneers have realistic enamel luster and less natural tooth removal (about 0.5-0.7mm for lip and cheek side removal) compared to all-porcelain crowns and porcelain crowns, which are very effective for medium to heavily discolored teeth. 5, all-porcelain crown, porcelain crown When the tooth discoloration is very serious or accompanied by tooth loss, patients can only choose all-porcelain crown or porcelain crown restoration. This method simply means that the natural tooth is ground down by a circle, about 2mm evenly, and then a crown is placed on the ground down tooth. If this sleeve is made entirely of porcelain powder, it is a full porcelain crown. The translucency of all-porcelain crowns is similar to that of normal teeth, and the aesthetic effect is very good.