A filling is a method of repairing a dental defect with an artificial substance, including two main steps: preparation of the cavity and filling. There are several methods to choose from: 1.Silver amalgam: the main advantage of this method is low price, but the disadvantage is that it cannot be used for front teeth because of its metallic color, and because there is no adhesion between silver amalgam and teeth, the edges of fillings are not tightly fitted, and long-term use can cause caries again at the junction of silver amalgam and teeth; 2.Resin filling: the advantage is that it is close to the color of teeth, but the disadvantage is that it shrinks in the process of hardening. If the cavity is big or involves the adjacent surface of the tooth, it is not very suitable, because it is easy to break and fracture, leading to the recurrence of cavity or tooth plugging, etc. At present, the emergence of nano-resin has greatly made up for this problem; 3, inlay restoration: for the larger defects of teeth, amalgam and resin are not very ideal, the more ideal restoration method is to use inlay to repair the defective teeth, which can be very good. The ideal restoration method is to use inlays to restore the defective tooth, which can repair the appearance and function of the tooth very well, especially for wormholes that are damaged to the tooth, the long-term effect is better.