Fixed restorations of the oral cavity are subdivided into: metal restorations, metal porcelain restorations, all-ceramic restorations. First, metal restoration The use of gold alloy, titanium alloy, stainless steel and other metals to produce crowns, the appearance of stainless steel color, mainly for posterior restorations, the main advantage: the price is relatively low, high strength; disadvantages of nickel-chromium alloy to the human body has a certain degree of allergenicity, biocompatibility is poor, the color is not beautiful. At present, it is basically replaced by porcelain restorations. Second, metal porcelain restorations 1, nickel-chromium porcelain teeth: nickel-chromium alloy in nickel and chromium as the main components. Nickel-chromium alloy has many advantages, hardness. But after a period of time will appear gum black line and other problems, affecting the aesthetics, has rarely been used for front teeth. 2, cobalt-chromium alloy porcelain teeth: mainly for the toxicity of nickel and beryllium and developed, biocompatible relative to nickel-chromium alloy is better, not easy to allergic, generally does not lead to changes in gum color, is currently a more ideal mid-range porcelain teeth. 3, silver palladium alloy porcelain: belongs to the semi-precious metal: higher corrosion resistance, biocompatibility is good, basically no gum color change, aesthetic effect is good. 4, gold alloy porcelain teeth: good biocompatibility, color better than ordinary alloy porcelain teeth. Gold alloy porcelain teeth with gold as the main component, while adding white gold, platinum and other precious metal components. Depending on the manufacturing process, they are divided into casting and gold deposition, the latter having higher precision than the former, without bubbles or impurities. Precious metal porcelain dental edge fit is good, their own teeth are not easy to corrosion, gold porcelain bonding force is good, not easy to chipped porcelain, etc., is the current metal porcelain in the very ideal choice. Third, all-ceramic restoration Compared with metal porcelain teeth, no metal inner crown, excellent biocompatibility, realistic color form, with high aesthetic performance, is currently the most ideal restoration. Zirconia is an excellent high-tech biomaterial with good biocompatibility, no irritation to the gums, no allergic reaction and high strength. Zirconia porcelain teeth have a very high quality, not only because of its materials, expensive equipment, but also because it uses today’s most advanced computer-aided design, laser scanning, and then computer program-controlled grinding production, as perfect as possible, for the production of single crowns or bridges for anterior and posterior teeth. Another very important point: all-ceramic crowns have no image on the MRI imaging results, metal porcelain teeth because of the presence of metal inner crowns, for MRI, may have to be affected.