An RPA clasp is a modification of an RPI clasp. Which statement correctly describes their differences?

An RPA clasp is a modification of an RPI clasp. Which statement correctly describes their differences?

• A. RPI = infrabulge, has a mesial rest, distal proximal plate, I bar
• B. RPA = suprabulge, has a mesial rest, distal proximal plate, and Akers clasp
• C. RPA is a good alternative when there is a severe soft tissue undercut or shallow vestibule
• D. RPA is a modification of an RPI

Answer: (B)

The key idea is how retention is placed relative to the tooth. RPI uses an infrabulge retentive arm (an I-bar) that sits below the height of contour and engages undercuts from beneath, while still keeping a mesial rest and a distal proximal plate. RPA changes this by using a suprabulge retentive component (an Akers clasp) that sits above the height of contour and engages the same proximal undercut differently. So, RPA is a modification that retains the same mesial rest and distal proximal plate but swaps the I-bar for an Akers clasp, which is why describing it as suprabulge with a mesial rest, distal proximal plate, and Akers clasp best conveys the difference.

The key idea is how retention is placed relative to the tooth. RPI uses an infrabulge retentive arm (an I-bar) that sits below the height of contour and engages undercuts from beneath, while still keeping a mesial rest and a distal proximal plate. RPA changes this by using a suprabulge retentive component (an Akers clasp) that sits above the height of contour and engages the same proximal undercut differently. So, RPA is a modification that retains the same mesial rest and distal proximal plate but swaps the I-bar for an Akers clasp, which is why describing it as suprabulge with a mesial rest, distal proximal plate, and Akers clasp best conveys the difference.