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26. designing of rpd


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shammasm, intro to dentures, removable prosthodontics, rpd

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26. designing of rpd

  1. 1. Designing of removable partial denture
  2. 2. Learning outcomes 1. List the differences between two main types of RPD’s. 2. Explain the design sequence. 3. Describe step by step procedure for designing RPD. 4. Explain the different color codes for designing RPD.
  3. 3. Replace what is missing and also preserve remaining tissues
  4. 4.  The objective of partial denture designing can be thought of as the control of denture movement while not exceeding the physiological tolerance of the oral structures.
  5. 5. Differentiation Between Two Main Types of Removable Partial Dentures
  6. 6. Class I and II Class III The manner in which each is supporte d Derive their primary support from tissues underlying the base and secondary support from the abutment teeth Derives all of its support from the abutment teeth
  7. 7. Class I and II Class III The method of impressio n making Dual impression/ functional impression Anatomic impression
  8. 8. Class I and II Class III The need for some kind of indirect retention Needed (because it rotates about a fulcrum) Not needed
  9. 9. Class I and II Class III The use of a base material that can be relined to compensat e for tissue changes. Acrylic- resin is generally used as a base material for distal extension bases. Metal bases are more frequently used in tooth- supported restorations, because relining is not as likely to be necessary.
  10. 10. Class I and II Class III Requirement s for direct retention a combination clasp could be used because it is a combination of cast and wrought materials incorporated into one direct retainer, RPI, RPA Akers, Embrasure, Ring clasp
  11. 11. Design Sequence  Path of insertion  Rests  Major connector  Minor connectors  Direct retainers  Indirect retainers
  12. 12. Rests Occlusal rests Premolars and molars Cingulum rests Maxillary canines Incisal rests Mandibular canines Interproximal occlusal rests On the dentulous side Extended occlusal rests Mesially tipped molars
  13. 13. Kennedy Class III Place rests adjacent to edentulous space (both ends). Exceptions: Teeth incapable of providing adequate support, poor crown/root ratio, or uncorrectable periodontal disease. If abutment tooth has improper anatomy for the indicated rest.
  14. 14. Place rests adjacent to edentulous space
  15. 15. Kennedy Class I & II Mesial rest preferred Distal rest preferred when: abutment is rotated plunger cusp/heavy centric contact on mesial large restoration on mesial
  16. 16.  If the rest is placed on the distal of the tooth adjacent to the edentulous area, when a posterior force is applied the tooth is tipped towards the edentulous area,
  17. 17.  which opens the proximal contacts between teeth and moves the tooth causing mobility and bone loss.
  18. 18.  When the rest is placed mesially (away from the edentulous area), the force tends to move the tooth towards the adjacent tooth mesially.  Thus the adjacent tooth absorbs some of the forces of occlusion.
  19. 19. Distal Extension-base RPD-Rest Position Distal rest Mesial rest
  20. 20.  A tooth is better able to tolerate vertically directed forces than horizontal forces.
  21. 21. kratochalkboard1.2.wmv
  22. 22.  If the rest is placed on the distal side of the abutment near the edentulous area, the forces are not vertical but almost horizontal in the region just next to the abutment.
  23. 23.  As you move the rest anteriorly, the forces are directed more favorably in a more vertical direction in relation to the edentulous area.
  24. 24. Major Connectors  Assess tori, height of floor of mouth, frenal attachments, which may affect major connector choice.
  25. 25. Mandibular Major Connectors Lingual bar Whenever possible (8 mm space) Linguoplate High frenum, floor of mouth less than 8 mm, resorption of ridges Want to stabilize teeth, May need to add teeth to RPD Want to avoid torus Sublingual bar When the height of the floor of the mouth in relation to the free gingival margins will be less than 6 mm.
  26. 26. Mandibular Major Connectors Lingual bar with cingulum bar (Kennedy Bar, Double Lingual Bar) When wide diastema exists between mandibular anterior teeth Cingulum bar (continuous bar) Excessive block-out of interproximal undercuts (crowding of teeth) Labial bar Malpositioned or lingually inclined teeth and Large mandibular tori
  27. 27. 1. Lingual bar 2. Sublingual bar 3. Cingulum bar (continuous bar) 4. Linguoplate 5. Lingual bar with cingulum bar
  28. 28. Maxillary Major Connectors Single palatal strap Bilateral tooth-supported prostheses Combination anterior and posterior palatal strap- type connector Class I and II arches, Long edentulous spans in Class II, modification 1 arches, Class IV arches, Inoperable palatal tori Palatal plate- type connector Some or all anterior teeth remain
  29. 29. Maxillary Major Connectors U-shaped palatal connector When a large inoperable palatal torus exists, and occasionally when several anterior teeth are to be replaced Single palatal bar - Anterior– posterior palatal bars -
  30. 30. U-shaped palatal connector
  31. 31. Lingual bar major connector should be located at least 3-4 mm inferior to gingival margins 3-4 mm
  32. 32. 6 mm Palatal major connector should be located at least 6 mm away from gingival margins.
  33. 33. Minor Connectors  Connects components to the major connector:  Direct retainer  Indirect retainer  Denture base
  34. 34.  Should be rigid  Should be located in an embrasure  Should taper towards the contact area
  35. 35. Between one minor connector and the other minor connector - 4 mm 4 mm
  36. 36.  Should form a right angle with the major connector 90o
  37. 37. DIRECT RETAINERS Occlusally approaching / Suprabulge / Circumferential/ Akers
  38. 38. DIRECT RETAINERS  Gingivally approaching / Infrabulge / Bar-type / Vertical projection • I bar • Y bar • T bar • Modified T bar
  39. 39. • Modified T bar • T bar
  40. 40. I-BAR Y-BAR
  41. 41. Direct Retainers Cl III  Clasp of Choice: Akers  Embrasure clasp: on dentulous side  Ring clasp: on single molar or tilted molar
  42. 42.  Use stress releasing retainers  More load transferred to residual ridge RPI RPA Combination Clasp Direct Retainers Cl I & II
  43. 43.  Clasp of Choice: RPI  If can’t use I-bar: RPA  High frenal attachment, soft tissue undercut, shallow vestibule  If can’t use mesial rest: Combination Clasp  Restoration, heavy occlusion, rotated tooth RPI RPA Combination Clasp
  44. 44. Number of Direct Retainers  4 - Greatest amount of retention  (e.g. Cl. III, mod 1)  3 - Less retentive, (Class II)  2 - Absolute minimum (Class I)
  45. 45. Indirect Retainers  For Class I & II only  Position on the opposite site of fulcrum line  Perpendicular and far from fulcrum line  Canine and premolar usually  Rest at each end of lingual plate
  46. 46.  FORM OF INDIRECT RETAINER  Auxiliary occlusal rest  Cingulum rest  Incisal rest
  47. 47.  Step by step procedure for designing
  48. 48. Drawing the Design  Absolute Accuracy  Technician to place elements in proper position & proportions
  49. 49. Drawing the Design  Absolute Accuracy  Single clear lines  No guessing involved
  50. 50. Armamentarium for survey & design
  51. 51. Color codes  Brown – metallic component  Blue – acrylic resin portion  Red – rest seat, areas of the teeth to be prepared, relieved or contoured, tripod marks  Black – survey lines, soft tissue undercuts, wrought wire clasp, type of tooth.
  52. 52. Red color- To denote action
  53. 53. Black color – To place survey lines
  54. 54. Brown color - For metal frame work
  55. 55. Blue color - For acrylic resin
  56. 56.  No single design philosophy can be considered "correct" over all others. Variations are possible as long as diagnostic information and good mechanical principles form the basis for the design.