a denture retention system includes a denture and an abutment . the denture has an inner channel with an elastic liner having shaped cavities . the cavities have a shaft , a head at the closed end of the shaft and a concave ring between two convex sections on the shaft . the abutment has a shaft , a head at one end of the shaft , a protruding ring between two concave sections on the shaft and a threaded portion at the other end of the shaft portion . the surface of the cavity overlaps and engages the surface of the abutment to retain the denture in the cavity . the threaded part of the abutment threads into an implant or implants into a jaw . the cavity expands when the abutment is inserted or removed from the cavity , and contracts after insertion .