The I-bar is more esthetic in most instances since it contacts the tooth minimally.
The RPI clasp is best used on caries prone patients. An advantage of an infrabulge clasp system (I-bar) is minimal tooth contact and minimal distortion of normal tooth contours. This leads to improved tissue stimulation and oral hygiene and decreased caries and periodontal problems.
The I-bar, proximal plate and mesial rest and minor connector provide adequate encirclement by engaging more than 180 of the tooth. Encirclement of an abutment prevents permanent tooth movement by contacting the tooth at a minimum of three points. The RPI clasp system accomplishes this on the mesial with the minor connector, which connects the rest to the major connector, on the distal with a guide plane and on the facial with the I-bar infrabulge clasp.
A mesial rest eliminates the potential “pump handle” effect that a force on the base would provide with a distal rest. On a distal extension RPD, a clasp in an undercut forward of the axis of rotation (which would occur with a distal rest) has the potential for torquing the abutment when functional forces are applied (a class I lever). When an I-bar clasp assembly with a mesial rest functions properly, the retentive tip moves downward and forward into a deeper undercut when functional forces are applied and prevents the “pump handle” effect on the tooth.