Alternatives to Clasp-Retained Removable Partial Dentures

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Alternatives to Clasp-Retained Removable Partial
Dentures

• Rotational Path
• Hidden Clasp/Twin Flex/Saddle Lock
• Equipoise
• Virginia Partial
• Invisible Clasps (Optiflex)
• Attachment Partial Dentures

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Fractured Abutments Kennedy Class IV (Category I)
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Rotational Path RPD

• Elimination of clasps on one side of RPD
• Place rigid element into undercut
• Rotate other end into place (clasps)

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Place in Undercut, Rotate Clasp into Place
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Principles

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

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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

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Effective RPD DesignUnderutilized
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Potential Problems

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

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Hidden Clasp/Twin Flex

• Uses retentive undercut on proximal surface
• Requires sufficient undercut
• Space for clasp movement - hygiene

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Hidden Clasp

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

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Hidden Clasp Results
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Equipoise
Lingual back-action clasp reciprocated Minimal
facial clasp display.
1mm
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Equipoise
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Equipoise

• Greater preparation
• Minimal Stress release
• Kennedy Class III situations
• Visible metal mesial embrasure display

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Flexible Gasket RPDs

• Virginia Partial - elastomeric
• Cu-Sil - elastomeric
• Flexite/Valplast - thermoplastic
• No clasps

Cu-Sil
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Flexible Gasket RPDs

• Difficult to adjust, polish
• Tend to tear, rough surface

Cu-Sil
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Virginia Removable Partial Denture

• Silicone gasket around teeth
• Compensates for lost bone/gingival height
• Patients generally favour

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Virginia Removable Partial Denture

• Hygiene
• Caries potential
• Liner lifespan

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Virginia Removable Partial Denture

• Hygiene
• Caries potential
• Liner lifespan

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Invisible Clasps (Optiflex)

• Non-metal, white
• OptiFlex Coating applied to metal clasps

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Invisible Clasps (Optiflex)

• Thick, white, ugly clasp?
• Porous (plaque)
• Fatigue
• Bulky (comfort)

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Other alternatives

• Bonding composite to clasp arm
• Anodizing clasp arm
• Precision Semi-Precision Removable Partial
  Dentures

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Overview of Prosthetic Attachments
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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

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Uses for Attachments

• Fixed Partial Dentures
• Lack of draw between abutments
• Stress distribution

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Uses for Attachments

• Removable partial dentures
• Comfort
• Less Bulk
• Within confines of Crown

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Uses for Attachments

• Removable partial dentures
• Esthetics
• Retention

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Uses for Attachments

• Overdentures
• Retention

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Classifications of Attachments

• By type of Prosthesis
• Intracoronal / Extracoronal
• Precision / Semi-Precision

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Intracoronal Attachments

• Female portion of attachment within a crown

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Extracoronal Attachments

• Portion of attachment outside of crown/retainer
  contours

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Precision Attachments

• Box or key way
• One path of insertion
• Allows minimal to no rotation

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Precision Attachments

• Milled prostheses

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Semiprecision Attachments

• Less intimate fit
• Some leeway or resilience
• Principle to relieve stress

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Overdenture Attachments

• Bars
• Balls
• Studs
• Magnets

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Overdenture Attachments
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Scope of Practice

• Generally beyond scope of GP
• GPs should be aware of possibilities

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Advantages

• Esthetics
• Hygiene

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Advantages

• Stress distribution
• deep rest
• directs stress along long axis
• Single path of movement

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Advantages

• Comfort - fewer lingual components

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Disadvantages

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

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Disadvantages

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

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Disadvantages

• Overdenture flange must draw with attachments
• Cant place flange in some undercuts

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Disadvantages

• Technique sensitive
• Lab
• Parallelism
• Casting
• Processing acrylic

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Disadvantages

• Technique sensitive
• Dentist
• Tissue base impression
• Relating Base to teeth

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Contraindications

• Short clinical crowns
• Large pulps
• Dexterity problems
• Bruxers?

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Design Considerations

• Precision Attachments
• Frictional retention
• Resilient or stress releasing
• Allows movement
• Lose stress distributing properties

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Design Considerations

• Tissue Health
• Critical
• Compressible tissue - recovery
• Affects occlusion

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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

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Design Considerations

• Metal - expensive, cast-to or solder
• Plastic forms - cheaper, casting errors

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Patient Instructions

• Removed cleaned at least once/day
• Do not apply pressure - bending
• Nonabrasive denture toothpaste
• Soft tooth brush
• No bleach

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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

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Patient Instructions

• Routine adjustments required
• Prevent major problems
• Dental checkups twice a year
• Advise type of attachments
• Record attachment type and replacement in chart

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Summary - Attachment RPDs

• 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

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Summary - Esthetic Alternatives

• No panacea
• significant disadvantages with some designs
• Costs
• Managing expectations is important
• Initially
• Long-term