Plastics dental plate expansion screw

摘要

The body of the expansion screw (10,12) has a channel (40) to admit the plastics of the plate, the channel surface contacting the plastics being extended to the internally threaded screw bore. The screw spindle (14) has opposed thread sectors (14c-14f) so as to screw into the second screw body (12) itself also channelled right through to the screw bore as for body (10). The channel can form a hole at right angles to the screw bore or parallel to this, in which case the channel is set back from the inside surface of the bore. A channel parallel to the bore can also be produced by a slot through the wall of the screw bore concerned. Additional components include guide pins (16) of optional section, eg. circular or flat, and notched at the ends to form endstops (16a,b), the screw being located by collar (18) until potted into the plate for convenient handling. Thus the plastics flows down the channel so as to set in place and supplement the bored part of the screw thread.