Defined the retainer for a removable partial prosthetic as " any portion of the device that touches the teeth and helps to prevent the withdrawal would as a result, portions of the approximal plaque of the older connectors contribute to the retention by the parallelism of the proximal plates between itself and the frictional contact of metal and the tooth. Retainers are flexible the casting is designed deliberately to penetrate the undercuts in the teeth brackets in order to oppose the removal of the device and help prevent its eviction.There are two basic types of seals direct, according to the classification of DeVan:1. Retainers infraecuatoriales. 2. Retainers supraecuatoriales.
