Transcript RPD_files/Esthetic RPD`s & Prec Att Undergrad

Alternatives to Clasp-Retained
Removable Partial Dentures
Rotational Path
Hidden Clasp/Twin Flex/Saddle Lock
Equipoise
Virginia Partial
‘Invisible’ Clasps (Optiflex)
Attachment Partial Dentures
Fractured Abutments
Kennedy Class IV (Category I)
Rotational Path RPD
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Elimination of clasps
on one side of RPD
Place rigid element
into undercut
Rotate other end into
place (clasps)
Place in Undercut, Rotate Clasp into Place
Principles
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Large deep rests to
provide support,
reciprocation
Reciprocation from
adjacent teeth
End that rotates must
not have rigid
elements in undercut
Preparations
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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
Effective RPD Design
Underutilized
Potential Problems
Impossible to adjust
 Modification spaces (large blockout)
 Require sufficient undercut
 Require ability to hide metal
guiding plate
 Requires good laboratory support
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Blockout
Hidden Clasp/Twin Flex
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Uses retentive
undercut on proximal
surface
Requires sufficient
undercut
Space for clasp
movement - hygiene
Hidden Clasp
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Designed by lab
(retentoscope)
If insufficient
retention, labs tend to
bring the clasp
around to facial
Variable retention
(Soo et al, 1996)
Hidden Clasp Results
Equipoise
Lingual back-action clasp
reciprocated
Minimal facial clasp display.
1mm
Equipoise
Equipoise
Greater preparation
 Minimal Stress release
 Kennedy Class III situations
 Visible metal mesial embrasure display
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Flexible ‘Gasket’ RPD’s
Virginia Partial - elastomeric
 Cu-Sil - elastomeric
 Flexite/Valplast - thermoplastic
 No clasps
Cu-Sil
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Flexible ‘Gasket’ RPD’s
Difficult to adjust, polish
 Tend to tear, rough surface
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Cu-Sil
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)
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Non-metal, white
Opti•Flex
Coating
applied to metal
clasps
‘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
Attachments
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Type of direct retainer
Metal receptacle (matrix =
female) attached to
• An abutment or
• A prosthesis
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Closely fitting component
(Patrix = male) mates with
the receptacle
Uses for Attachments
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Fixed Partial Dentures
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Lack of draw between
abutments
Stress distribution
Uses for Attachments
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Removable partial dentures
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Comfort
• Less Bulk
• Within confines of Crown
Uses for Attachments
Removable partial dentures
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Esthetics
Retention
Uses for Attachments
 Overdentures
• Retention
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
Extracoronal Attachments
Portion of attachment outside of crown/retainer contours
Precision Attachments
Box or key way
 One path of insertion
 Allows minimal to no rotation
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Precision Attachments
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Milled prostheses
Semiprecision Attachments
Less intimate fit
 Some leeway or resilience
 Principle to relieve stress
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Overdenture Attachments
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Bars
Balls
Studs
Magnets
Overdenture Attachments
Scope of Practice
Generally beyond scope of GP
 GP’s should be aware of possibilities
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Advantages
Esthetics
 Hygiene
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Advantages
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Stress distribution
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deep rest
directs stress along long axis
Single path of movement
Advantages
Comfort - fewer lingual components
Disadvantages
Cost
 Maintenance
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Critical
 More complex types
need more
maintenance
 If poorly maintained
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• Catastrophic failures
• Patient response
Disadvantages
Extra tooth preparation
for intracoronal
 If insufficient reduction
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• over-contoured retainer
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Major reduction of
non-restored teeth
Disadvantages
Overdenture
flange must draw
with attachments
 Can’t place
flange in some
undercuts
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Disadvantages
Technique sensitive
 Lab
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Parallelism
 Casting
 Processing
acrylic
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Disadvantages
Technique sensitive
 Dentist
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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
 Tissue Health
 Critical
 Compressible tissue - recovery
 Affects occlusion
Patient Instructions
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Routine adjustments required
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Prevent major problems
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Dental checkups twice a year
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Advise type of attachments
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Record attachment type and replacement #
in chart
Summary - Attachment RPD’s
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Attractive Advantages
Maintenance critical and costly
Long term success if:
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Dentist uses utmost care
Patient follows care & maintenance regime
If dentist or patient careless, ultimately
fails
Summary - Esthetic Alternatives
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No panacea
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significant disadvantages with some designs
Costs
Managing expectations is important
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Initially
Long-term