RPD Review Questions

Answer to Question #6

The correct answer is

Incorrect. All of the clasps should be cast. Since there is no functional movement of a class III RPD, there is no need for the stress-breaking effects of wrought wire clasps.

Correct. Lower molars, particularly second or third molars, frequently have no facial undercuts. In addition, the normal drift of the teeth is to the lingual, accentuating lingual undercuts and minimizing facial undercuts.

Incorrect. Modified T-bars would be the retainers of choice if the undercuts were on the distofacial. I-bars could be used but the tiny space between the I-bars and the denture base would create food traps and would make the plastic very difficult to finish properly. In addition, the I-bars would tend to be very short and inflexible.

Incorrect. Only one arm of each clasp assembly should extend into an undercut (be retentive). The other arm must be rigid to provide bracing or reciprocation and thus cannot extend into an undercut and provide retention.