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Alternatives to Clasp-Retained Removable Partial Dentures

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Presentation on theme: "Alternatives to Clasp-Retained Removable Partial Dentures"— Presentation transcript:

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

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

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