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principles of PD design.pptx
This document discusses principles of removable partial denture (RPD) design, including Kennedy classification systems for different clinical situations, considerations for support and retention, and a systematic approach to RPD design. Key points covered include differentiating tooth-supported versus tissue-supported designs, using minor connectors along guiding planes for optimal stress distribution, and employing techniques like indirect retainers and reciprocal clasps to restrict horizontal movement. The summary concludes that RPD design should be systematically developed based on factors like the location of support and how retention is achieved.
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principles of PD design.pptx
- 1. Principles of RPD Design AmmarGhanem Salem 4th year KBMS- Restorative Department
- 2. Essentials of RPD design Kennedy classification Systematicapproach to RPD design 01 Differences between classification regarding support and retention 02 03 04 Table of contents Additional considerations of RPD Conclusions 05 06
- 3. Class I Bilateraledentulous areas located posterior to natural teeth Class II Unilateral edentulous area located posterior to natural teeth Class III Unilateral edentulous area with natural teeth remaining both anterior and posterior to it Class IV Single but bilateral –crossing the midline- edentulous area located anterior to the remaining natural teeth Kennedy classification
- 5. Differnces in support Toothsupported RPD have less movement because resistance is provided by teeth. Tooth-tissue supported RPD have variable potential for support. Differences regarding classifications
- 7. CI and CIIprimary support from tissue underlying base, and secondary support from abutment teeth. CIII all its support from abutment teeth.
- 8. CI and CIIrequire dual selective pressure impression, while CIII can be done in single stage impression. Indirect retainer is needed for CI and CII due to fulcrum effect.
- 9. The length andcontour of residual ridge significantly influence the amount of support and stability needed.
- 10. Flat ridge providegood support but poor stability. Displaceable tissue provide poor support and poor stability.
- 11. Approaching undercut from occlusalor gingival direction Cast circumferential Clasp Design It provide direct retention CIII Require clasp at each end of edentulous span
- 12. Clasp Design CI andCII The direct retainer not only should resist vertical dislodging forces but also should be able to flex sufficiently to dissipate the stresses that torquing on terminal abutment from leverage effect. Mesial rest seat reduce leverage effect by changing fulcrum point. Wrought wire (WW) provide more flex in all directions than cast half round (cross-section) arm, also bar clasp type can be used. Use of combination clasp (circumferential arm + rigid reciprocating arm) is indicated, where only MB undercut exists or gross tissue undercut cervical and buccal to abutment tooth.
- 13. Essentials of RPDDesign How to be supported ? Systematic development of design How to be retained ? Connecting units Outline and join edentulous area to other components
- 14. How to be supported? 01 Ideal rest location for CIII is on abutment adjacent to each edentulous space. Consider: periodontal health, crown and root morphologies, crown to root ratio, location of tooth in the arch, location of tooth to other supporting units. CI and CII need same consideration with adding evaluation of residual ridge
- 15. How to besupported ? Maximal contact of proximal plate minor connector with guiding plane produces more horizontal distribution of stress to abutment teeth.
- 16. How to besupported ? Minimal contact or disengagement of minor connector with guiding plane allows rotation around fulcrum on MO rest producing more vertical stress to ridge.
- 17. How to besupported ? Minor connector with guiding plane from marginal ridge to junction of middle and gingival 3rd of abutment tooth distributes load vertically to the ridge and horizontally to abutment tooth.
- 18. Connect tooth and tissue supportunits through major and minor connectors 02
- 19. How to Retain? 03 Byplacement of clasps and intimate relationship of denture base and major connectors with underlying tissues.
- 20. Connect the retention unitsto support units 04
- 21. Outline and join theedentulous area to already established design components 05
- 22. framework parts Minor connectors Join majorconnector to other parts Direct retainers Retention and resistance Major connectors Connect parts on one side to the opposite Guiding plane and rest seats Direct prosthesis during removal and placement and resist tissueward movement Indirect retainers Restrict movement of base away from tissue 1 2 3 4 5
- 23. Direct retainers CIII Two functions: 1.Retain prosthesis against dislodging forces without damage to abutment teeth. 2. Aid in resisting any tendency of denture to be displaced in a horizontal plane. Intracoronal frictional retainers are ideal. circumferential and bar type extracoronal retainers are effective
- 24. Direct retainers CI-II In additionto the two functions, it should act as stress breaker due to tissue-ward movement during function. It should have clasp arm with flex end to accomplish stress breaking without sacrificing horizontal stabilization.
- 25. Guiding plane Two ormore parallel vertical surfaces of abutment teeth to direct a prosthesis during placement and removal. Preferred to be more than two abutments on wide separate positions.
- 26. Guiding plane In situationof lone standing abutment
- 27. Indirect retainers Needed onlyin class I and II where distal extension exists. Should be as anterior as possible from fulcrum line. Cannot function effectively on inclined tooth or single weak incisor.
- 28. Sequencing Design approach 1. Rest 2.Major connectors 3. Minor connectors 4. Denture base connectors 5. Retainers
- 29. Systematic approch todesign CI Mandible Maxilla support Occlusal rest, cingulum rest, denture base palatal coverage Major c. Anteroposterior palatal strap, full coverage stability Guide planes, indirect retainers, reciprocal clasp, palatal plating. Retention RPI, RPA, or combination clasp support Same Denture base using selective pressure technique stability Same Lingual plating Major c. Lingual bar or lingual plate Retention Same
- 30. Systematic approch todesign CII Mandible Maxilla support Occlusal rest, cingulum rest, denture base Major c. Anteroposterior palatal strap, horseshoe stability Guide planes, indirect retainers, reciprocal clasp, palatal plating. Retention RPI, RPA, or combination clasp (DE side) Embrasure clasp, circumferential clasp (Dentate side) support Same Denture base using selective pressure technique stability Same Lingual plating Major c. Lingual bar or lingual plate Retention RPI, RPA, Combination clasp
- 31. Systematic approch todesign CIII Mandible Maxilla support Occlusal rest, cingulum rest Major c. Palatal strap Palatal bar stability Guide planes, reciprocal clasp Retention circumferential clasp, I bar clasp support Same stability Same Major c. Lingual bar Retention same
- 32. Implant considerations inRPD design aim to reduce distal extension movement and enhancing support if placed at distal most tooth position Additional considerations influencing design
- 33. Additional considerations influencing design Internalclip attachments Overlay abutments Splint bars Overlay attachments Component partial 1 2 3 4 5
- 34. Splint bar When severalmissing anterior teeth with length span that cannot be replaced with FPD + large amount of residual ridge defect Complete assembly of abutment and bar are cemented then impression is done. Framework extend to cover upon bar.
- 35. Internal clip attachment Provide supportand retention. Custom bar and clip.
- 36. Overlay abutment Saving teeth inmolar region through endodontic and periodontal treatment. Including reduction of clinical crown in slightly elevated dome shaped abutment.
- 37. Component partial Individual separate partsare fabricated. Tissue support and tooth support individually fabricated then joined with high impact acrylic resin.
- 38. Conclusions The design ofthe partial denture framework should be systematically developed and outlined on an accurate diagnostic cast based on the following prosthesis concepts: where the prosthesis is supported, how the support is connected, how the prosthesis is retained, how the retention and support are connected, and how edentulous base support is connected.
- 39.
Editor's Notes
- #6 Other factors affecting support: -opposing dentition. -occlusion. -broad dissipation of occlusal relationship at MI
- #7 Tissue distortion over edentulous ridge 500 um under 4 N, whereas abutment teeth show only 20 um under same load.
- #10 The longer the area covered by denture base the greater the leverage.
- #11 It can be addressed with dental implant
- #13 Tissue-ward movement affected by: quality of soft tissue, accuracy of denture base, and total occlusal load applied.
- #15 Quality of ridge, extent of edentulous space covered by denture base, type and accuracy of impression, accuracy of base, design characteristics of components of framework, and anticipated load.
- #20 For successful clasp design: Avoid direct transmission of tipping or torquing forces to abutment. Accommodate basic principles of clasp design. Provide retention against reasonable dislodging forces. Compatible with undercut location, tissue contour, and esthetic desires of the patient.
- #25 Cast clasp used for tooth supported side while wrought wire for distal extension side to reduce torque. In case of severe tissue undercut or only MB undercut exist then a combination of retentive arm with tapered wrought wire is used.
- #26 Function: Provide one path of placement and removal. To ensure the intended action of reciprocal, stabilizing, and retentive components. To eliminate gross food traps between abutment and other components.
- #27 Inevitable torquing forces.
- #34 And implants
- #35 Act as guide plane Aid in resisting horizontal rotation. Should be lingually positioned to allow arrangement of teeth.
- #36 Metal or nylon clips fit the bar which is retained within metal housing or embedded by spurs or loops into resin base.