RPD Review Questions

Answer to Question #188

The correct answer is

The RPA concept has occasionally been recommended for distal extension RPDs and includes a distal guide plate, a mesial rest, and a circumferential retentive arm originating from the guide plate. Problem: If the originating portion of the arm lies above the height of contour, it will pre-empt the mesial rest and will act like a distal rest on an inclined plane. The retentive tip will now engage the undercut during functional movement of the extension base.