The invention concerns a dental implant assembly including an implant component (10) which is engaged in use with a bone structure and which has an internally threaded socket (14). The assembly also includes a dental component (20), typically an abutment, crown or prosthetic tooth, which seats on the implant component and which has a passage (24) through its base (22). The dental component is clamped to the implant component by a prosthetic retaining screw (28) having a head (32) and a shank (30) which passes through the passage and is screwed into the socket of the implant component. The invention is characterized in that a separate washer (36) including a low friction polymeric material is located rotatably on the shank of the screw adjacent the screw head in order to reduce friction between the head of the screw and the base of the dental component when the screw is tightened up.