The snap ring is made of metal, and its function is to retain, stabilize and support. It is the main retainer for removable denture restorations. The structure of the clasp is divided into a clasp arm, a clasp body, a small connecting body and a supporting bracket. The clasp arm is a free part of the clasp, which is full of elasticity. The arm tip of the snap ring is located in the undercut area, which is the main part of the retaining effect of the snap ring. When the denture is put in, the elasticity of the arm end is retained by the snap ring, and it enters the undercut area through the contour protrusion of the abutment crown. When the dislocation force works, it will prevent the denture from dislocating in the direction. During the process of entering and exiting the undercut area of u200bu200bthe retaining arm through the high point of the abutment shape, the horizontal component force generated by the retaining arm on the abutment should be offset by the correspondingly designed clasp opposing arm or guide plane plate, small connecting body, etc. To avoid lateral force damage to the abutment. The initial part of the clasp arm should be relatively rigid and placed in the non-undercut area to stabilize and prevent lateral displacement of the denture. The shape of the snap ring arm is different according to the material used and the manufacturing method, and there are three commonly used circular, semicircular and flat shapes. The clasp body is also known as the clasp shoulder: it is the hard part connecting the clasp arm, the rest and the small connecting body. It can stabilize and support the denture and support the clasp arm at the same time, so the clasp body is required to have high strength, not easily deformed, located in the non-undercut area, and does not affect the occlusion. The small connector is the part of the snap ring embedded in the base or connected with the large connector, which mainly plays the role of connection, so that the snap ring and other parts of the denture are integrated into a whole. The connector should not enter the abutment or soft tissue undercut area, so as not to affect the seat. The support is often cast in one piece with the snap ring. The so-called three-arm snap ring is a general name for the support as an arm.