Chapter 2 Components od RPD O6U ( Dr Mai Diab ) (1).pdf

CHAPTER 2 COMPONENTS OF RPD COMPONENT PARTS OF REMOVABLE PARTIAL DENTURES Components of metallic removable partial dentures are all rigid, with the exception of the flexible retentive clasp arm located in an und...

CHAPTER 2 COMPONENTS OF RPD COMPONENT PARTS OF REMOVABLE PARTIAL DENTURES Components of metallic removable partial dentures are all rigid, with the exception of the flexible retentive clasp arm located in an undercut area for retaining the restoration against dislodging forces. The components of removable partial denture are: 1. Denture bases. 2. Artificial teeth. 3. Supporting rests. 4. Connectors: a- Major connectors. b- Minor connectors. 5. Retainers: a- Direct retainers. b- Indirect retainers. 1 4a 2 5a 3 4b 5b Fig.3-1: The component parts of typical Fig.3-2: Flexible clasp arm engaging mandibular partial denture. tooth undercut Page - 13 - of 15  CHAPTER 2 COMPONENTS OF RPD These Components May Provide One or More of the Following Functions: 1-Support: a. The resistance of a denture to tissue ward movement (Fig.3-3a, 3-4). b. Adequate and wide distribution of the load to the teeth and mucosa. 2- Retention: The resistance of a denture to vertical displacement force (to move away from its tissue foundation) (Fig.3-3,b). 3- Indirect retention: The resistance of denture rotation away from the tissues about an axis (Fig.3-5). 4- Bracing: The resistance of a denture to lateral forces (Fig.3-6 and 3-7). 5- Reciprocation: The resistance of lateral forces on the abutment during insertion and removal of the removable partial denture (Fig.3-8). Reciprocation is required as the denture is being displaced occlusally whilst the bracing function, comes into play when the denture is fully seated. 6- Stability: The resistance of a denture to tipping movement. Tipping movement: Vertical rotation around a line parallel to ridge crest (twisting of the denture base) (Fig.3-9). Fig.3-3,a: Support is the resistance of a Fig.3-3,b: Retention is the resistance of a denture to tissue-ward movement. denture to tissue away movement. Page - 14 - of 15 CHAPTER 2 COMPONENTS OF RPD Fig. 3-4: support in distal-extension Fig. 3-5: denture rotation away from the denture is gained through the tissues about an axis. denture base and the occlusal rest. Fig.3-6: Bracing is the resistance of a Fig. 3-7: Lateral borders of the ridge must be denture to lateral forces. covered to provide bracing and stability for distal-extension dentures. Fig.3-8: Reciprocation: (1) If the clasp arm is unopposed the tooth is displaced and much of the retentive capability will be lost. (2) If the retentive clasp is opposed by a rigid component which maintains contact with the tooth as the retentive arm moves, displacement of the tooth is resisted Fig.3-9: When cervically directed force is applied to one side only rotation can occur around longitudinal axis formed by crest of residual ridge(twisting of the denture base). Page - 15 - of 15