“ I” Bar Retainers: Reciprocation An active “I” bar retainer can be reciprocated by one of the following: Opposing reciprocating clasp at 0.00 (“I” bar or “C” clasp) A combination of rest, minor connector and proximal plate. “ I” Bar Retainers – Design Principles The tip should be positioned at the point of greatest mesial distal curvature on the tooth “ I” Bar Retainers Design Principles When properly designed the “I” bar engages the undercut down into the 0.25 mm region but the occlusal-incisal tip terminates at the height of contour When designed in this way the RPD will slide in out of place with a smooth frictional resistance Height of contour “ I” Bar Retainers Design Principles When properly designed the “I” bar engages the undercut down into the 0.25 mm region but the occlusal-incisal tip terminates at the height of contour When designed in this way the RPD will slide in out of place with a smooth frictional resistance Height of contour. An active “I” Bar requires only 0.25 mm undercut. Ideally “I” bar terminates in gingival 1/3 of the tooth.

“ I” Bar Retainers Design Principles A space is created between “I” bar and mucosa (it is crossing over) to prevent tissue hypertrophy (arrows).

Horizontal portion of the “I” bar is placed on attached tissue whenever possible Connection of “I” bar to RPD casting should be in placed in the interproximal area between denture teeth (arrow). “ I” Bar Retainers Design Principles “ I” bar should cross tooth tissue junction at right angles and parallel to long axis of tooth. Better Esthetics “ I” bars Only the tips are visible in most patients “ I” Bar Retainers : Maximum natural cleansing action Passive functional movement of an extension prosthesis (when the rest is properly positioned) Benefits “ I” Bar Retainers: Minimal tooth contact Allows for easier adjustment of the retainer Enables exact placement of retention contact This very important in extention base RPD’s Minimal Interference with natural tooth contour Benefits “ I” Bar Retainers: Effectiveness of retention is dependent upon the stability of the RPD which in turn is dependent on the presence of properly designed minor connectors, guide-planes and proximal plates In particular, properly contoured guide planes-proximal plates are integral to successful use of “I” bar retainers “ I” Bar Retainers: Low retentive value compared to other types This is due to minimal tooth engagement and partly to purposeful design since support, stability and control of tooth position is established with positive rests, minor connectors and proximal plates Types of Retainers (Clasps) Infra-bulge “ I”-Bar The approach of the direct retainer is from below the height of contour Supra-bulge clasp Circumferential clasp The approach of the direct retainer is from above the height of contour. Retainers, Clasp Assemblies and Indirect Retainers Clasp assembly The part of a removable partial denture that acts as a direct retainer (clasp) and/or stabilizer (minor connectors, proximal plates etc) for a prosthesis by partially encompassing an abutment tooth Retainers, Clasp Assemblies and Indirect Retainers Direct retainers That component of a removable partial denture used to retain and prevent dislodgment of a clasp assembly or attachment. Retainers, Clasp Assemblies and Indirect Retainers No portion of this program of instruction may be reproduced, recorded or transferred by any means electronic, digital, photographic, mechanical etc., or by any information storage or retrieval system, without prior permission. Retainers, Clasp Assemblies and Indirect Retainers Ting Ling Chang, Takahiro Ogawa and John Beumer III Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry This program of instruction is protected by copyright ©. Retainers, Clasp Assemblies and Indirect Retainers - Course Transcript

Height of contour definition