Which of the following feature sets defines an RPI clasp?

Which of the following feature sets defines an RPI clasp?

• A. Infrabulge design with a mesial rest, distal proximal plate, I bar
• B. Suprabulge design with a mesial rest, distal proximal plate, Akers clasp
• C. Minor connector with guiding plane
• D. Major connector with occlusal rest

Answer: (A)

An RPI clasp is defined by a three-part arrangement that sits on an infrabulge path: a rest on the tooth for vertical support, a proximal plate on the distal (or mesial) proximal surface to stabilize and provide reciprocal action, and an I-bar that engages undercuts on the buccal or lingual aspect for retention. The infrabulge design means the retention components extend below the height of contour, allowing the clasp to engage undercuts without bulky coverage, which helps preserve periodontal health and provide discreet retention. The mesial rest provides vertical support and prevents tipping; the distal proximal plate stabilizes the abutment and resists rotation by contacting the proximal surface; and the I-bar delivers retention by engaging an undercut with minimal tooth preparation. This combination specifically characterizes the RPI design. The other options describe different clasp types or framework features (suprabulge Akers clasp, minor connector with guiding plane, or major connector with an occlusal rest) and do not define the RPI pattern.

An RPI clasp is defined by a three-part arrangement that sits on an infrabulge path: a rest on the tooth for vertical support, a proximal plate on the distal (or mesial) proximal surface to stabilize and provide reciprocal action, and an I-bar that engages undercuts on the buccal or lingual aspect for retention. The infrabulge design means the retention components extend below the height of contour, allowing the clasp to engage undercuts without bulky coverage, which helps preserve periodontal health and provide discreet retention. The mesial rest provides vertical support and prevents tipping; the distal proximal plate stabilizes the abutment and resists rotation by contacting the proximal surface; and the I-bar delivers retention by engaging an undercut with minimal tooth preparation. This combination specifically characterizes the RPI design. The other options describe different clasp types or framework features (suprabulge Akers clasp, minor connector with guiding plane, or major connector with an occlusal rest) and do not define the RPI pattern.