With the continuous improvement of people’s living standards and the popularization of oral health care knowledge, the concept of green restorations has begun to enter the public’s field of vision and has been highly valued. While porcelain restorations are pursuing the beauty of their appearance, the inner crowns of porcelain teeth have also begun to receive more attention. What is green restoration? What should be noted about green restorations? The key lies in the choice of material for the crown. The potential disadvantages of nickel-chromium porcelain alloy non-precious metal nickel-chromium alloy porcelain teeth are made of nickel-chromium alloy for the inner crown, the surface layer of porcelain. Its material is made of: from nickel, chromium, beryllium, manganese and other metals. Characterized by high strength, low price, and able to form a dense oxide layer, it is a kind of porcelain teeth most commonly used in China. However, the biggest problem with Nichrome is that some patients can experience allergy symptoms. Nickel-chromium alloy porcelain teeth on the person’s biggest irritation and adverse reactions mainly from the nickel metal. Due to the high activity of nickel metal compared to other metals, there is a free release of the metal, which produces free black lines on the gums, and a slight toxic reaction. Foreign data show that 15-20% of women and 1-2% of men who wear nickel-containing hand jewelry are allergic and experience inflammatory reactions of the skin and mucous membranes. The probability of occurrence of allergies in the oral cavity statistics are rarely reported, but should not be as high as the probability of skin allergies, but once allergic to both the patient’s pain and the physician to bring a lot of trouble. Nickel-chromium alloy is not enough also manifested in the color gray and black, although the alloy surface for the porcelain covered and not revealed, but in the neck porcelain and metal joints can be black lines appear, especially after a long time is more obvious. In addition, recent studies have shown that nickel-containing dust, aerosol and human long-term contact can cause conjunctivitis, bronchitis, skin inflammation, and even become nasopharyngeal carcinoma, lung cancer carcinogenic factors. The relevant departments of some European countries warned against the use of nickel content of more than 1% of the alloy, while the nickel content of porcelain is generally between 62 ~ 82%, so nichrome alloy porcelain teeth in these countries has actually lost the market. Studies have shown that the amount of chromium in the alloy has an absolute effect on the corrosion resistance of Ni-Cr alloys in the oral cavity. When the content of chromium in the nickel-chromium alloy exceeds 20%, the alloy is relatively stable and has a high corrosion resistance. On the contrary, the alloy is very susceptible to corrosion, nickel ions continue to precipitate, the human body will cause discoloration of the gums after absorption of black and other symptoms. Some inferior nickel-chromium alloys contain beryllium (carcinogenic metal), which is harmful to human body, even if the content is very low, it will cause great harm to health. Precious metal and cobalt chromium porcelain alloy Precious metal porcelain alloy main elements for gold, palladium, platinum and so on. The processing technology and composition ratio of this type of alloy are very delicate, and cannot be produced domestically at present. The outstanding advantage of precious metal alloy is that it is non-toxic and non-irritating, rarely causing allergies, and the restorations made are of high precision. In addition, the gold alloy orange-yellow background color and human teeth and gingival tissues close to the tone, there is no gray-black edge of the problem, appear beautiful and natural. Hypersensitive people may have an allergic reaction to gold, then you can choose pure titanium porcelain crowns. Pure titanium is highly inert and does not have any allergic reaction. However, the combination strength of pure titanium and porcelain (gold and porcelain bonding) is not as strong as porcelain and precious gold alloy and nickel-chromium alloy, and also has the disadvantage of gray and black background color. Precious metal porcelain with its excellent biocompatibility has been recommended by the industry, but due to the expensive price of precious metal porcelain restoration, coupled with the international price of gold continues to rise, the domestic ordinary patients are more difficult to accept. Cobalt chromium porcelain alloy Nickel chromium porcelain has many disadvantages, the high price of precious metals, the people are very difficult to accept, a few years ago there is titanium alloy in the middle of the price, it is now proved that titanium alloy also contains nickel, and nickel-chromium alloy is not very different, especially titanium alloy after casting, after testing has been no titanium, and also some disputes have arisen from this, so titanium alloy is slowly launched into the market, so the middle of the price ceramic who can Who can compete with the middle price of porcelain? Undoubtedly cobalt chromium alloy porcelain has the advantage. Cobalt chromium alloy was first used to make artificial joints, with outstanding biocompatibility, is now widely used in the field of oral restoration, because it does not contain nickel and beryllium elements harmful to the human body, safe, reliable and reasonably priced cobalt chromium alloy has become the first choice of European and American patients with non-precious metal porcelain restoration.