Here I would like to briefly introduce to you the materials used for dental fillings, which should be a common concern for patients with dental disease. There are three commonly used materials, silver amalgam, glass ionomer and nano-light curing material. I will simply categorize their retention principles as mechanical retention, bonded retention and chemical retention respectively, the first two can be categorized as physical retention. First, the silver amalgam think we are not unfamiliar, as early as a few decades ago this material is very common for dental materials, just when the fillings are silver, slowly oxidized over time into black. The characteristics of this material are very high mechanical strength and wear resistance, but the disadvantage is that it has very high requirements for tooth retention, which means that the shape of the cavity after preparation is very strict. Another fatal disadvantage is that it is very irritating to the pulp, so it is necessary to take protective measures for the pulp cavity before filling silver amalgam, otherwise there is a risk of causing pulp lesions. Based on the above points, silver amalgam is not suitable for all patients, the indications should be strictly controlled, and the color is poor and can only be used for posterior teeth. However, it is fair to say that once the indication is chosen correctly, this material is still very strong and durable. Second, glass ionomer This is the most common material I use in the clinic. This material is acceptable to everyone in terms of color and shade, and the adhesiveness and mechanical strength are quite good. With the renewal of the material, the bonding of glass ionomer is getting better and better, and the requirements of the retention shape are not as strict as before, so the damage to the dental tissue when preparing the cavity is relatively small. It is also very easy for us dentists to operate. Glass ion has another advantage that cannot be underestimated, that is, it has very little irritation to the dental pulp, even if it is deep caries, it is very safe to use, and even has the effect of anti-caries, and it is clinically applicable to all caries. The biggest advantage of this material is that it has good solidity, the color is close to the teeth, and it has the effect of faking; but the disadvantage is also obvious that it has strong irritation to the pulp. The bonding principle is very special, so I will briefly explain it to you. The surface of the tooth is first treated with an acid etching agent to form a honeycomb of micro-pores, and then the resin is embedded in these micro-pores by a bonding process. Therefore, this material also requires strict selection of indications, not all patients are suitable, and furthermore, it is expensive, and many patients are still not willing to accept it. Finally, I would like to tell you that no matter what the material is, it is not as strong as your own teeth, which can break when biting hard objects, let alone materials that are only bonded by external forces. Some patients questioned when they visited the clinic that the filling material did not fall off in the past, but the filling material now is falling off, not knowing that the solidity of the filling material is determined by many factors, such as the size, shape and location of the cavity, biting habits, oral hygiene condition, etc. After filling the teeth, we should not be paralyzed and correct the bad biting and hygiene habits, so as to prolong the life of the filling material.