Invisalign is a type of removable denture, which is known for its elastic resin retainer, located at the gingival margin of natural teeth, and its good simulation. Elastomeric resin is a new type of prosthetic material, which was introduced to China from the United States in 1995. Its characteristics are high strength, suitable elasticity, good flexibility and translucency*, its color is close to the natural gingival tissue, with good bionic effect and very good concealment. It and the elastic resin for soft lining of denture are two materials with different chemical structure, performance and usage, which have no chemical bonding with the soft lining resin and traditional resin artificial teeth. (1) Elastomeric resin retainer has better retention effect because it can be retained by soft tissue recess, especially in cases where the crowns of abutment teeth are too short or the recess is small, it can make better use of the recess and is not easy to fall off, and because the retainer of denture forms a surface contact with the surface of abutment teeth, it has much greater friction than metal retainer with only point line contact. (2) The elastic resin retainer is designed to be placed on the cervical part of the tooth and the alveolar ridge underneath to jointly withstand external forces, and its elasticity and toughness can also cushion the masticatory pressure in the missing tooth area and play a physiological massage role, and produce less damage to the abutment teeth such as lateral stress. In addition, the elastic retainer and abutment are well closed to the abutment teeth, so it is not easy to accumulate food. (3) All movable dentures made of elastic resin are generally mucosa-supported, and the force is not easily dispersed. force is not easily dispersed and chewing efficiency is low. Elastic resin is not easily polished to a high degree, not easily repaired after damage, and cannot be relined. The conventional PMMA resin base and the metal-made conventional removable denture and the invisible denture use metal retainer, when the former teeth as abutment, easy to expose the metal, affecting the aesthetics; the non-elastic part of the base, the connector and the retainer must be cushioned in the natural tooth recess area, leaving a space easy to accumulate food; but the conventional removable denture also has its unique superiority*, it can be designed as a tooth-supported and mixed-supported, and the force can be easily dispersed, and can withstand large chewing efficiency. The force can be easily dispersed and can withstand large? It can be designed as tooth-supported and hybrid-supported, and the force can be easily dispersed to withstand large forces. The PMMA base can be highly polished and chemically bonded to the resin artificial teeth, so it is easy to repair, add artificial teeth and relining process. In terms of processing, the invisible denture is fundamentally different from the traditional PMMA resin. The traditional PMMA thermocoagulation resin is completed by a programmed heat treatment process, with heat-induced curing and programmed water bath temperature control between 60-100℃, while the invisible denture requires an injection process, a special resin infusion machine, a special elastic resin (ValPlast, USA), a resin electric baking oven The process is completed by natural cooling at 287°C after injection. The invisible denture is “theoretically” suitable for all kinds of missing teeth, even if the front and back teeth are missing at intervals, the remaining teeth have a large recess, and there is no common seating channel, the invisible denture can still be used, because the invisible denture base has a high elasticity *, can be twisted, the denture can be put in place by twisting and rotating, after the seating is not only good retention, and good closure The denture is not only well seated, but also well closed and will not embed food. Although the invisible denture has the above advantages, but the traditional invisible denture for posterior restorations, due to the use of simple mucosal support type, the normal chewing pressure will accelerate the resorption of the alveolar ridge in the missing tooth area, so more scholars advocate the invisible denture restoration into the posterior teeth can be used as a transitional restoration or semi-permanent restoration. Finally, it is worth mentioning that when dealing with cases of tooth loss in the molar area and major tooth loss, some scholars have used a combination of elastic resin and traditional PMMA resin and cast brackets designed to disperse? forces to achieve good restorative results. However, because of the lack of chemical bonding between the three and the different processing techniques, the design and fabrication are complicated, and not many of them are carried out at present.