For tooth decay and tooth defect, the common restoration methods are: 1.Silver amalgam filling: The advantage is that it is cheap. The disadvantage is that it cannot be used for front teeth because its color is metallic; there is no adhesion between silver amalgam and teeth due to shrinkage, and the edge of filling is not tight, and long-term use may cause caries to occur again at the junction of silver amalgam and teeth. 2.Resin filling: The advantage is that it is close to the color of the tooth. The disadvantage is that it can only be applied to fillings of smaller cavities due to shrinkage in the process of hardening. If the cavity is very big or involves the adjacent surface of the tooth, the resin filling is not so suitable in the long run. It is easy to break and fracture. It will lead to recurrence of caries or corked teeth, etc. 3.Inlay restoration: For a very large tooth defect, silver mercury and resin are not ideal. The ideal restoration method is to use inlay to restore the defective teeth. It can restore the shape and function of the tooth very well. Especially for cavities that are damaged to the adjacent surface of the tooth, the long-term effect is better. An inlay is a restoration or an intracoronal cement that is embedded inside a tooth to restore the form and function of a defective tooth. The advantage of cast inlays over silver amalgam fillings is their excellent mechanical properties. Indications for inlays: various severe defects involving cusps, incisors, marginal crests, and symphyseal surfaces, requiring occlusal reconstruction that cannot be restored with general materials; poor adjacent connections or severe food impaction due to dental defects, requiring restoration of adjacent contact points; fixed bridges with cavities in the abutment teeth or to place plugs or plugs for attachment, inlays can be designed as a base retainer. Inlay restoration is not a new dental restoration method, it is available in the textbooks of domestic undergraduate dentistry students, unfortunately, domestic dental education is not carried out much for one reason or another, and many teeth that need inlay restoration are filled with silver mercury or resin. Inlays can be classified according to the classification of materials as metal inlays, resin inlays, porcelain inlays, etc.