Porcelain teeth from the structure of the inner crown and glazed porcelain layer composed of two parts, from the texture is divided into metal crowns, and all-ceramic crowns porcelain, according to the different crowns, can be divided into 12 categories of porcelain crowns. 1, nickel-chromium alloy porcelain crown: nickel and chromium as the main components. Nickel is about 73.6% to 87.6%, chromium 12.4% to 26.4%, melting point of 1455 degrees casting shrinkage rate of 1.8% to 2.3, its cobalt content is higher than the nickel-based alloys, generally 25%, there are elements such as Cu, W, Nb, Si, Ru, Al and Mo. As nickel can react with saliva in the mouth to produce free nickel, accumulating in the crown and gum edge, it produces the familiar black line (gray staining). 2, titanium alloy porcelain crowns: due to the limitations of the cast titanium technology and equipment, can not do to let the titanium alloy raw materials in the inert gas casting, titanium alloy raw materials in the natural air casting, the result of titanium metal in the air oxidation volatilization. In addition, titanium itself is light in quality, in the centrifugal casting, titanium metal backward, it can not enter the casting. The so-called “titanium alloy porcelain crowns” do not meet the standard of 6% titanium content. The actual titanium content is sometimes lower than the titanium content of nickel-chrome porcelain itself. 3, cobalt chromium inner crown porcelain teeth: cobalt 58.5% -64.5%, molybdenum 4.5%-7%, chromium 26.5%-30%, can be seen, cobalt chromium porcelain abandoned the “nickel” added to avoid the salivary toxicity of nickel metal. 4, pure titanium inner crown porcelain: “titanium” metal has excellent biological safety, light weight, but high hardness. Stable performance, is the ideal choice of oral restorative materials, pure titanium metal is the only one does not react with the body of the metal, is the most biocompatible medical metal. In addition, titanium metal hard texture, not easy to deform, is a cost-effective restorations in the precious metal porcelain. 5, gold alloy inner crown porcelain crown: its inner crown containing gold in more than 84%, another containing platinum, palladium, not only can reduce the weight of the restoration, but also strengthen its strength, not easy to metal allergy phenomenon, but also on the body of the protein decomposition and absorption of a certain help, is the precious metal porcelain in the petite one. In addition to its only pure yellow background color, and porcelain combination, simulation of natural teeth index is very high. Due to the beauty of the front teeth, it is still a good choice. Also because, its own metal elasticity ductility is the best, the strongest cushioning ability, very suitable for tooth root short, poor bone quality of dental restoration and cosmetic, at the same time the accuracy is relatively high. Prices vary somewhat with the weight of the gold used. This kind of porcelain teeth do quite a lot. 6, all-ceramic teeth: all-ceramic production is the first porcelain material burned inner crown, all-ceramic teeth and metal porcelain teeth, the biggest difference is that the inner crown made of porcelain, is a transparent skeleton, and then burned on the outer layer of porcelain powder. Because all-ceramic has good light transmission, and the body’s absolutely no irritation, the sense of natural, ① cast porcelain teeth: three generations, a generation of white garnet for the inner crown, also known as the casting of glass ceramics; second generation of lithium-based ceramics for the inner crown. It is also commonly known as aluminum dioxide 95 corundum powder. The production process of cast porcelain teeth is to take a good dental mold after the whole casting. Cast porcelain is a kind of all-ceramic, the full name should be “cast all-ceramic”. The strength of the third generation is much improved, is the best choice for aesthetic restoration of the front teeth. Zirconium dioxide all-ceramic crown: is a whole porcelain block by the computer-assisted, by the milling machine semi-mechanical manufacturing, strength is very large, comparable to the metal porcelain, non-toxic and harmless to the body, does not contain metal, but the strength of the metal porcelain can be comparable. Currently the most ideal porcelain restoration, anterior teeth cosmetic restorations. Due to the improvement of zirconia process, the thickness of the base crown is reduced from the original 1 mm to 0.35 mm, the area of the tooth to be abraded becomes smaller, and the enamel loss rate is minimized. It is suitable for any kind of high-end situation that requires porcelain fabrication. It has no effect on future MRI and CT examinations.