RPD Review Questions

Answer to Question #78

The correct answer is

Correct. A mesial rest and I-bar is the best choice. The I-bar lies at or behind the axis of rotation and would release during functional movement of the denture base. It is our #1 choice if the undercut is in the appropriate location, if an infrabulge clasp can be used, and if there is no contraindication to placement of a rest on the mesio-occlusal surface.

Incorrect. Although a modified T-bar could work, it is not the first choice, especially when most of the undercut lies on the mesiofacial surface.

Incorrect. This would be the "RPA" concept. The problem is that the originating portion of the clasp is rigid and would lie above the survey line. It would function like a rest on an inclined plane---not a good idea!

Incorrect. Although a distal rest and WW circumferential clasp could work in this situation, it is not our first choice. We would rather have a clasp arm that releases during functional movement (downward, tissueward) movement of the denture base.