V2I6P31

‘RPA or RPI’ Concept – What is your choice? – A Review

Dr. B. Lakshmana Rao^1*

Abstract

For patients who are partially edentulous, removable partial dentures (RPDs) are an economical and biologically responsible treatment option.  The RPA (Rest–Proximal Plate–Akers clasp) and RPI (Rest–Proximal Plate–I-bar clasp) concepts have been identified as biologically advantageous designs among the different clasp assemblies used in RPD design, especially in distal extension cases (Kennedy Class I and II).  As stress-releasing clasp assemblies, both systems are designed to reduce damaging torquing forces on abutment teeth while under functional loading.  A mesial occlusal rest, a guide plane on the distal surface, and a gingivally approaching I-bar clasp that disengages during occlusal loading are the main components of the RPI system, which was first put forth by Krol in the 1970s. It provides superior biomechanical benefits, better gingival health, and improved aesthetics.  The RPA system is more appropriate in anatomical circumstances where I-bar placement is contraindicated because, despite having a similar structure, it substitutes a traditional circumferential clasp (Akers clasp) that wraps around the abutment tooth for the I-bar. Both RPA and RPI systems now have greater accuracy, flexibility, and patient comfort thanks to recent developments in CAD-CAM technology, digital framework design, and the use of biocompatible alloys like titanium and NiTi.  Evidence-based improvement of these designs has also been aided by technologies such as laser sintering and finite element analysis (FEA).  In summary, functional RPD design relies heavily on both RPA and RPI systems.  But because of its superior stress-distribution properties, aesthetic appeal, and periodontal compatibility, the RPI system is widely favored and is a mainstay of modern prosthodontic practice.

Keywords:

Removable Partial Dentures; Rest, Proximal Plate I bar (RPI) Concept; Rest Proximal Plate Akers Clasp (RPA) Concept; Biomechanical Principles in RPD Design