The main function of the snap ring is to install it in the ring groove and form an artificial appropriate shoulder on the shaft or in the hole of the body to ensure the specified position of the part. According to the assembly method of the snap ring, it can be divided into axially assembled snap ring and radially mounted snap ring. The clasp arm is the free part of the clasp and is elastic. 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 shape 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 damage to the abutment by lateral force. The initial part of the clasp arm should be 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 production method, and the commonly used three are circular, semicircular and flat.