1. Alternatives to Clasp-Retained Removable Partial Dentures
Rotational Path
Hidden Clasp/Twin Flex/Saddle Lock
Equipoise
Virginia Partial
‘Invisible’ Clasps (Optiflex)
Attachment Partial Dentures

2. Fractured Abutments Kennedy Class IV (Category I)

3. Rotational Path RPD Elimination of clasps on one side of RPD
Place rigid element into undercut
Rotate other end into place (clasps)

4. Place in Undercut, Rotate Clasp into Place

6. Principles Large deep rests to provide support, reciprocation
Reciprocation from adjacent teeth
End that rotates must not have rigid elements in undercut

7. Preparations Sufficient reduction if placing a crown
Avoid undercuts in rests
Prepare axis close to rotational axis
Dovetail if no other element to keep abutment from moving

8. Effective RPD Design Underutilized

9. Potential Problems Impossible to adjust
Modification spaces (large blockout)
Require sufficient undercut
Require ability to hide metal guiding plate
Requires good laboratory support
Blockout

10. Hidden Clasp/Twin Flex
Uses retentive undercut on proximal surface
Requires sufficient undercut
Space for clasp movement - hygiene

11. Hidden Clasp Designed by lab (retentoscope)
If insufficient retention, labs tend to bring the clasp around to facial
Variable retention (Soo et al, 1996)

12. Hidden Clasp Results

13. Equipoise Lingual back-action clasp reciprocated
Minimal facial clasp display.
1mm

14. Equipoise

15. Equipoise Greater preparation Minimal Stress release
Kennedy Class III situations
Visible metal mesial embrasure display

16. Flexible ‘Gasket’ RPD’s
Virginia Partial - elastomeric
Cu-Sil - elastomeric
Flexite/Valplast - thermoplastic
No clasps
Cu-Sil

17. Flexible ‘Gasket’ RPD’s
Difficult to adjust, polish
Tend to tear, rough surface
Cu-Sil

18. Virginia Removable Partial Denture
Silicone gasket around teeth
Compensates for lost bone/gingival height
Patients generally favour

19. Virginia Removable Partial Denture
Hygiene
Caries potential
Liner lifespan

20. Virginia Removable Partial Denture
Hygiene
Caries potential
Liner lifespan

21. ‘Invisible’ Clasps (Optiflex)
Non-metal, white
Opti•Flex Coating applied to metal clasps

22. ‘Invisible’ Clasps (Optiflex)
Thick, white, ugly clasp?
Porous (plaque)
Fatigue
Bulky (comfort)

23. Other alternatives Bonding composite to clasp arm Anodizing clasp arm
Precision & Semi-Precision Removable Partial Dentures

24. Overview of Prosthetic Attachments

25. Attachments Type of direct retainer
Metal receptacle (matrix = female) attached to
An abutment or
A prosthesis
Closely fitting component (Patrix = male) mates with the receptacle

26. Uses for Attachments Fixed Partial Dentures
Lack of draw between abutments
Stress distribution

27. Uses for Attachments Removable partial dentures Comfort Less Bulk
Within confines of Crown

28. Uses for Attachments
Removable partial dentures
Esthetics
Retention

29. Uses for Attachments
Overdentures
Retention

30. Classifications of Attachments
By type of Prosthesis
Intracoronal / Extracoronal
Precision / Semi-Precision

31. Intracoronal Attachments
Female portion of attachment within a crown

32. Extracoronal Attachments
Portion of attachment outside of crown/retainer contours

33. Precision Attachments
Box or key way
One path of insertion
Allows minimal to no rotation

34. Precision Attachments
Milled prostheses

35. Semiprecision Attachments
Less intimate fit
Some leeway or resilience
Principle to relieve stress

36. Overdenture Attachments
Bars
Balls
Studs
Magnets

38. Overdenture Attachments

39. Scope of Practice Generally beyond scope of GP
GP’s should be aware of possibilities

40. Advantages
Esthetics
Hygiene

41. Advantages Stress distribution Single path of movement deep rest
directs stress along long axis
Single path of movement

42. Comfort - fewer lingual components
Advantages
Comfort - fewer lingual components

43. Disadvantages Cost Maintenance Critical
More complex types need more maintenance
If poorly maintained
Catastrophic failures
Patient response

44. Disadvantages Extra tooth preparation for intracoronal
If insufficient reduction
over-contoured retainer
Major reduction of non-restored teeth

45. Disadvantages Overdenture flange must draw with attachments
Can’t place flange in some undercuts

46. Disadvantages Technique sensitive Lab Parallelism Casting
Processing acrylic

47. Disadvantages Technique sensitive Dentist Tissue base impression
Relating Base to teeth

48. Contraindications Short clinical crowns Large pulps Dexterity problems
Bruxers?

49. Design Considerations:
Precision Attachments
Frictional retention
Resilient or stress releasing
Allows movement
Lose stress distributing properties

50. Design Considerations
Tissue Health
Critical
Compressible tissue - recovery
Affects occlusion

51. Design Considerations
Stress distribution
Splinting advised by some to distribute stress - probably not needed
Splinting complicates hygiene
Tooth vs. tissue borne - some advise not on distal extension (precision)
Cervical placement of forces

52. Design Considerations
Metal - expensive, cast-to or solder
Plastic forms - cheaper, casting errors

53. Patient Instructions Removed & cleaned at least once/day
Do not apply pressure - bending
Nonabrasive denture toothpaste
Soft tooth brush
No bleach

54. Patient Instructions
Leave precision attachment RPD in at all times except for cleaning
Use vibrating motion when removing or replacing the denture - Do not force

55. Patient Instructions Routine adjustments required
Prevent major problems
Dental checkups twice a year
Advise type of attachments
Record attachment type and replacement # in chart

56. Summary - Attachment RPD’s
Attractive Advantages
Maintenance critical and costly
Long term success if:
Dentist uses utmost care
Patient follows care & maintenance regime
If dentist or patient careless, ultimately fails

57. Summary - Esthetic Alternatives
No panacea
significant disadvantages with some designs
Costs
Managing expectations is important
Initially
Long-term