The long arm snap ring is also called the extension snap ring. It is used for loose abutments near the gap or those who cannot obtain sufficient retention force without undercuts. The long arm snap ring is to extend the snap ring arm to the undercut area of u200bu200bthe adjacent tooth near the gap abutment to obtain retention, and to protect the loose abutment with a fixed splint. No part of this snap ring should enter the undercut area of u200bu200bthe loose abutment near the gap. It is often used for abutments with loose abutments near the gap or with poor crown profiles. Extension snap rings can be cast or bent. 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. In the process of entering and exiting the undercut area through the high point of the abutment shape, the horizontal component force of the long arm snap ring on the abutment should be counteracted by the correspondingly designed snap ring opposing arm or guide plane plate, small connector, etc. Avoid damage to the abutment by lateral force. The starting part of the clasp of the long arm should be firm 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.