Mainly introduce the knowledge points of casting snap ring
There are many types of clasp, and the classification methods are different. In addition to the classification according to the relationship between the clasp and the observation line, it is generally classified according to the production method and the number of clasp arms. The retaining ring is made of wax, embedded, and made of high-melting alloy through casting process. Casting snap rings include annular snap rings and rod snap rings. Circular clasp: It surrounds 3 faces and 4 axis angles of the abutment tooth, that is, it wraps more than 3/4 of the crown of the abutment tooth. This kind of snap ring was first applied by Aker (1936), so it is also called Aker snap ring. The annular snap ring is suitable for the abutment with healthy periodontal tissue and good crown shape, and its supporting, retaining and stabilizing effects are good. Rod snap ring: Rod snap ring was first proposed by Roach (1934), so it is also known as Roach snap ring. This snap ring has relatively independent buccal and lingual arms. The snap ring arm is protruded from the metal bracket of the base, the retention mesh in the base or the size connector, and is convex from the gum to the abutment. Click on the undercut area. Its retention is a push-type retention from bottom to top, so it is also called a push-type snap ring. It is suitable for the abutment teeth with free and missing posterior teeth, and its retention effect is good, but the stabilization effect is poor.