Dentosphere : World of Dentistry

 # RPI clasp in a distal extension cast partial denture:

A. Used for buccally tilted molar

B. Provides push type retention

C. Provides pull type retention

D. Is contraindicated

The correct answer is:

B. Provides push type retention

Explanation:

The RPI clasp (Rest, Proximal plate, I-bar) system in a distal extension removable partial denture provides push-type retention because the I-bar clasp moves in a downward direction towards the gingiva when the denture base moves occlusally during function. This ensures that forces are directed in a manner that minimizes torque on the abutment tooth and enhances tissue support.

Breakdown of Key Features:

1. Rest: Positioned mesially to redirect forces along the long axis of the abutment tooth.
2. Proximal Plate: Contacts the guiding plane to stabilize the denture and control path of insertion and removal.
3. I-bar clasp: Engages an undercut and moves gingivally (pushes) as the denture is seated or when occlusal forces displace the denture base.

The push-type action of the I-bar helps maintain a stress-relieving design by allowing movement and reducing torque on the abutment during function.