Silicone rubber is always soft because both silicone rubber and alginate are silicone rubber, which is not easy to lose water and has strong fidelity. After taking the mold, the model material can be poured immediately, or within 48 hours, or sometimes it can be sent to the manufacturer for pouring. Silicone rubber and alginate are two kinds of impression materials. However, alginate impression material is easy to lose water and deform, so the model material should be poured immediately after taking the mold, especially in summer or when the temperature is high. The main function of silicone rubber is to remove saliva or blood pollution. The second mold taking is to correct the position of the first mold taking and realize the positioning. Silicone rubber impression material is a fine impression material, and the female die obtained by using it is more accurate and stable than ordinary alginate impression material. Using silicone rubber impression material to make the female die of fixed prosthesis is beneficial for the later technicians to make it, so that the made prosthesis can be more closely combined with tooth tissue. The use of silicone rubber impression material needs the cooperation of doctors, nurses and patients.