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RPI Rest Function — NDEB AFK MCQ

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HardProsthodonticsRPI Rest FunctionNDEB AFK

Which of the following correctly describes the purpose of the 'occlusal rest' in the RPI (rest, proximal plate, I-bar) clasp system for a distal extension RPD?

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Correct answer: C — To direct forces along the long axis of the abutment tooth and act as a fulcrum for the rotational movement of the distal extension base

In the RPI system (Krol, 1973), the mesial occlusal rest serves to direct occlusal forces along the long axis of the abutment tooth and acts as the primary support component. It also serves as a fulcrum point — when the distal extension base rotates toward the ridge under function, the rest acts as the pivot point, allowing the I-bar clasp to disengage from the undercut (reducing torque on the abutment). This is a key difference from circumferential clasps, which remain engaged during rotation and transmit more stress to the abutment.

Reference: Carr – McCracken's Removable Partial Prosthodontics, 13th ed., 2015