If you have caries, you should repair it in time. How much do you know about the problem of loosening and falling off of caries filling material? The causes of loosening and falling off of filling material are very complicated, and can be summarized as the following aspects in general. (1) Secondary caries makes the filling material loosen and fall off: the caries which occurs in the edge of filling body or under the filling body is called secondary caries. The reason of loosening and falling off of filling material caused by secondary caries is: ① The filling body is not tight: it shows that the filling body is not tight with the cavity wall. This is due to the existence of air bubbles or vacuoles. Air bubbles or blisters often occur at the edge or neck of the tooth. The reason for the formation of bubbles or blisters is that the filling pressure is not enough or the filling material is too thinly mixed. To prevent the formation of bubbles or blisters, choose the appropriate filling instruments for silver-mercury fillings and use forming clips for Class II cavities. The filling instruments are required to move in the buccal and lingual directions to fill the corners of each cavity wall. In this way, the filled material will not have hollow bubble phenomenon. In addition, various paste materials should be mixed into dough, because of its poor fluidity, small cotton balls of various pastes should be prepared for filling and squeezing various pastes. Place the mixed paste in the hole, and use the paste in time to squeeze the small cotton ball until the squeeze is full. If the tightly filled tooth is observed by the naked eye, but the gap of 10-20 micrometer can be seen under the electron microscope, it means there are air bubbles or vacuoles, which is the reason of poor filling, i.e. secondary caries. Therefore, the measure to prevent the secondary caries is to fill tightly. In addition, keeping the cavity dry is also one of the measures to do a good job of tight filling. ②Weak cavity wall tissues: The weak tissues may be chewed up and food embedment may occur. This is due to the weak cavity wall and poor resistance to pressure resulting in defect. In addition, no base enamel can also cause weak cavity wall, medical education, education network|collected because of the lack of dentin lining under the enamel, resistance to pressure is reduced. ③ Dissolution of material on the edge of cavity wall: It refers to the cushion material such as zinc oxide clove oil paste and zinc phosphate mucilage attached on the edge of cavity wall, especially on the cavity or the cavity of the neck of class II cavity, which can be dissolved by saliva, and the gap appears after dissolution and causes caries. In fact, it is not difficult to check whether there is cavity cushioning material attached after cushioning. To remove the cavity’s cushion material, a digging spoon is usually used. ④ Oral saliva contaminate the cavity: some materials become soft and dissolve immediately when they meet water, such as zinc phosphate mucoadhesive powder, which can cause the material and the tooth to be incompatible. To prevent oral saliva contamination, we often use the method of isolating saliva and blow dry the cavity with steam gun. (2) Severe caries, loss of retention performance: severe caries generally refers to the residual crown or residual root: in terms of the retention performance of both the residual crown or residual root, the residual crown is stronger than the residual root. In general, the residual crown or residual root does not have the normal retention, and is most likely to loosen and fall off the filling. Clinical attention should be paid to the fixation of the residual crown or root before restoration. The specific approach is to use root canal retention and insert root canal nails to increase retention. (3) Tooth fracture: tooth fracture mostly occurs in dead pulp teeth. Because the dead pulp teeth are brittle, the pressure resistance is reduced, and they are easy to break. To prevent fracture of dead pulp teeth: lower the bite; also use the shell crown restoration technique to prevent fracture. (4) Fracture of fillings: Fracture of fillings is most often caused in teeth with the tip in close contact with the filling material, which bears more chewing pressure than other teeth, and is medically known as traumatic dentition. Traumatic manifestation in the crown is commonly seen in the fracture of the crown, especially in the adjacent cavity, causing the fracture of the crown and the filling material on one side. This is often resolved clinically using the metal shell crown technique of restoration. These are the causes of loosening and loss of filling material.