Porcelain teeth from the structure of the inner crown and enamel porcelain layer composed of two parts, from the texture is divided into metal crowns, and all-ceramic inner crown porcelain, according to the different crowns, can be divided into 12 types of porcelain crowns. 1, nickel-chromium alloy porcelain crowns: nickel and chromium as the main components. Nickel is about 73.6% to 87.6%, chromium is 12.4% to 26.4%, the melting point of 1455 degrees casting shrinkage of 1.8% to 2.3, its cobalt content is higher than nickel-based alloys, generally 25%, there are elements such as Cu, W, Nb, Si, Ru, Al and Mo. As nickel can react with the saliva in the mouth, producing free nickel, accumulating in the crown and gum edge, it produces the familiar black line (gray stain). 2, titanium porcelain crown: due to the limitations of titanium casting technology and equipment, can not do so titanium alloy raw materials in inert gas casting, titanium alloy raw materials in the natural air within the casting, the result of titanium metal in the air oxidation volatilization. Coupled with the titanium itself is light, in the centrifugal casting, titanium metal backward, it can not enter the casting. The so-called “titanium alloy porcelain crown” are not in line with the standard of 6% titanium. The actual titanium content is sometimes lower than the titanium content of nickel-chromium 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 saliva toxicity of nickel metal. 4, pure titanium inner crown porcelain: “titanium” metal has excellent biosafety, light quality, but high hardness. Stable performance, is the ideal choice of oral prosthetic materials, pure titanium metal is the only one does not react with the body of the metal, is the highest biocompatibility of medical metals. In addition, titanium is hard, not easy to deformation, is the precious metal porcelain restorations in the more cost-effective. 5, gold alloy inner crown porcelain crown: its inner crown contains more than 84% gold, another containing platinum, palladium, not only can reduce the weight of the restoration, but also to strengthen its strength, not easy to metal allergy phenomenon, but also on the muscle protein decomposition absorption has certain help, is the precious metal porcelain in the delicate. Plus its only pure yellow base color, combined with porcelain, simulation of natural teeth index is very high. Due to the front teeth cosmetic, is still a good choice. Also because, its own metal elastic ductility is the best, the strongest cushioning ability, very suitable for the root of the tooth is short, poor bone restoration and cosmetic teeth, while the accuracy is relatively high. The price varies somewhat depending on the weight of the gold used. This kind of porcelain teeth are made quite a lot. 6, all-porcelain teeth: all-porcelain production is the first porcelain material firing the inner crown, all-porcelain teeth and metal porcelain teeth the biggest difference is the inner crown made of porcelain, a transparent skeleton, and then in the outer layer of firing on the porcelain powder. Because all-porcelain has good light transmission, and the body of absolutely no irritation, natural-looking, ①. Cast porcelain teeth: three generations, a generation of white garnet for the inner crown, also known as cast glass ceramic; second generation of lithium-based ceramic 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 overall casting. Cast porcelain is a kind of all-porcelain, the full name should be “cast and pressed all-porcelain”. It is the best choice for aesthetic restoration of anterior teeth because its strength is much higher. ②. Zirconia full porcelain crown: is a whole porcelain block by computer-assisted, semi-machined by milling machine, very strong, comparable to metal porcelain, non-toxic and harmless to the body, does not contain metal, strength and metal porcelain equivalent. Currently the most ideal porcelain restorations, anterior teeth cosmetic restorations. Due to the improvement of the 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 rate of enamel loss is minimal. It is suitable for any kind of high-end situation that requires porcelain fabrication. There is no effect on future MRI and CT examinations. When I worked in the restorative department of Beijing Dental Hospital, this kind of porcelain teeth were done quite a lot.