Alternatives to Clasp-Retained Removable Partial Dentures Rotational Path Hidden Clasp/Twin...
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Transcript of Alternatives to Clasp-Retained Removable Partial Dentures Rotational Path Hidden Clasp/Twin...
Alternatives to Clasp-Retained Removable Partial Dentures
Alternatives to Clasp-Retained Removable Partial Dentures
Rotational Path
Hidden Clasp/Twin Flex/Saddle Lock
Equipoise
Virginia Partial
‘Invisible’ Clasps (Optiflex)
Attachment 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)
Fractured Abutments Kennedy Class IV (Category I)
Rotational Path RPDRotational Path RPD
Elimination of clasps on one side of RPD
Place rigid element into undercut
Rotate other end into place (clasps)
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 PlacePlace in Undercut, Rotate Clasp into Place
PrinciplesPrinciples
Large deep rests to provide support, reciprocation
Reciprocation from adjacent teeth
End that rotates must not have rigid elements in undercut
Large deep rests to provide support, reciprocation
Reciprocation from adjacent teeth
End that rotates must not have rigid elements in undercut
PreparationsPreparations
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
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 DesignUnderutilizedEffective RPD DesignUnderutilized
Potential ProblemsPotential Problems
Impossible to adjust Modification spaces (large blockout) Require sufficient undercut Require ability to hide metal
guiding plate Requires good laboratory support
Blockout
Impossible to adjust Modification spaces (large blockout) Require sufficient undercut Require ability to hide metal
guiding plate Requires good laboratory support
Blockout
Hidden Clasp/Twin FlexHidden Clasp/Twin Flex
Uses retentive undercut on proximal surface
Requires sufficient undercut
Space for clasp movement - hygiene
Uses retentive undercut on proximal surface
Requires sufficient undercut
Space for clasp movement - hygiene
Hidden ClaspHidden Clasp
Designed by lab (retentoscope)
If insufficient retention, labs tend to bring the clasp around to facial
Variable retention (Soo et al, 1996)
Designed by lab (retentoscope)
If insufficient retention, labs tend to bring the clasp around to facial
Variable retention (Soo et al, 1996)
Hidden Clasp ResultsHidden Clasp Results
EquipoiseEquipoise
Lingual back-action clasp reciprocated Minimal facial clasp display.
Lingual back-action clasp reciprocated Minimal facial clasp display.
1mm1mm
EquipoiseEquipoise
EquipoiseEquipoise
Greater preparation Minimal Stress release Kennedy Class III situations Visible metal mesial embrasure display
Greater preparation Minimal Stress release Kennedy Class III situations Visible metal mesial embrasure display
Flexible ‘Gasket’ RPD’sFlexible ‘Gasket’ RPD’s
Virginia Partial - elastomeric Cu-Sil - elastomeric Flexite/Valplast - thermoplastic No clasps
Virginia Partial - elastomeric Cu-Sil - elastomeric Flexite/Valplast - thermoplastic No clasps Cu-SilCu-Sil
Flexible ‘Gasket’ RPD’sFlexible ‘Gasket’ RPD’s
Difficult to adjust, polish Tend to tear, rough surface
Difficult to adjust, polish Tend to tear, rough surface
Cu-SilCu-Sil
Virginia Removable Partial Denture Virginia Removable Partial Denture
Silicone gasket around teeth Compensates for lost bone/gingival height Patients generally favour
Silicone gasket around teeth Compensates for lost bone/gingival height Patients generally favour
Virginia Removable Partial Denture Virginia Removable Partial Denture
Hygiene Caries potential Liner lifespan
Hygiene Caries potential Liner lifespan
Virginia Removable Partial Denture Virginia Removable Partial Denture
Hygiene Caries potential Liner lifespan
Hygiene Caries potential Liner lifespan
‘Invisible’ Clasps (Optiflex)‘Invisible’ Clasps (Optiflex)
Non-metal, white
Opti•Flex Coating applied to metal clasps
Non-metal, white
Opti•Flex Coating applied to metal clasps
‘Invisible’ Clasps (Optiflex)‘Invisible’ Clasps (Optiflex)
Thick, white, ugly clasp? Porous (plaque) Fatigue Bulky (comfort)
Thick, white, ugly clasp? Porous (plaque) Fatigue Bulky (comfort)
Other alternativesOther alternatives
Bonding composite to clasp arm Anodizing clasp arm Precision & Semi-Precision Removable
Partial Dentures
Bonding composite to clasp arm Anodizing clasp arm Precision & Semi-Precision Removable
Partial Dentures
Overview of Prosthetic AttachmentsOverview of Prosthetic Attachments
AttachmentsAttachments Type of direct retainer Metal receptacle (matrix =
female) attached to• An abutment or• A prosthesis
Closely fitting component (Patrix = male) mates with the receptacle
Type of direct retainer Metal receptacle (matrix =
female) attached to• An abutment or• A prosthesis
Closely fitting component (Patrix = male) mates with the receptacle
Uses for AttachmentsUses for Attachments
Fixed Partial Dentures Lack of draw between
abutments Stress distribution
Fixed Partial Dentures Lack of draw between
abutments Stress distribution
Uses for AttachmentsUses for Attachments
Removable partial dentures Comfort
• Less Bulk• Within confines of Crown
Removable partial dentures Comfort
• Less Bulk• Within confines of Crown
Uses for AttachmentsUses for Attachments
Removable partial dentures Esthetics Retention
Removable partial dentures Esthetics Retention
Uses for AttachmentsUses for Attachments
Overdentures• Retention
Overdentures• Retention
Classifications of AttachmentsClassifications of Attachments
By type of Prosthesis Intracoronal / Extracoronal Precision / Semi-Precision
By type of Prosthesis Intracoronal / Extracoronal Precision / Semi-Precision
Intracoronal AttachmentsIntracoronal AttachmentsFemale portion of attachment within a crownFemale portion of attachment within a crown
Extracoronal Attachments Extracoronal Attachments
Portion of attachment outside of crown/retainer contoursPortion of attachment outside of crown/retainer contours
Precision AttachmentsPrecision Attachments
Box or key way One path of insertion Allows minimal to no rotation
Box or key way One path of insertion Allows minimal to no rotation
Precision AttachmentsPrecision Attachments Milled prostheses Milled prostheses
Semiprecision AttachmentsSemiprecision Attachments
Less intimate fit Some leeway or resilience Principle to relieve stress
Less intimate fit Some leeway or resilience Principle to relieve stress
Overdenture AttachmentsOverdenture Attachments Bars Balls Studs Magnets
Bars Balls Studs Magnets
Overdenture AttachmentsOverdenture Attachments
Scope of PracticeScope of Practice
Generally beyond scope of GP GP’s should be aware of possibilities
Generally beyond scope of GP GP’s should be aware of possibilities
AdvantagesAdvantages
Esthetics Hygiene
Esthetics Hygiene
Advantages Advantages
Stress distribution deep rest directs stress along long axis
Single path of movement
Stress distribution deep rest directs stress along long axis
Single path of movement
Advantages Advantages
Comfort - fewer lingual componentsComfort - fewer lingual components
Disadvantages Disadvantages Cost Maintenance
Critical More complex types
need more maintenance
If poorly maintained• Catastrophic failures• Patient response
Cost Maintenance
Critical More complex types
need more maintenance
If poorly maintained• Catastrophic failures• Patient response
DisadvantagesDisadvantages
Extra tooth preparation for intracoronal
If insufficient reduction• over-contoured retainer
Major reduction of non-restored teeth
Extra tooth preparation for intracoronal
If insufficient reduction• over-contoured retainer
Major reduction of non-restored teeth
DisadvantagesDisadvantages
Overdenture flange must draw with attachments
Can’t place flange in some undercuts
Overdenture flange must draw with attachments
Can’t place flange in some undercuts
DisadvantagesDisadvantages
Technique sensitive Lab
Parallelism Casting Processing
acrylic
Technique sensitive Lab
Parallelism Casting Processing
acrylic
DisadvantagesDisadvantages
Technique sensitive Dentist
Tissue base impression
Relating Base to teeth
Technique sensitive Dentist
Tissue base impression
Relating Base to teeth
ContraindicationsContraindications
Short clinical crowns Large pulps Dexterity problems Bruxers?
Short clinical crowns Large pulps Dexterity problems Bruxers?
Design Considerations Design Considerations
Tissue Health Critical Compressible tissue - recovery Affects occlusion
Tissue Health Critical Compressible tissue - recovery Affects occlusion
Patient InstructionsPatient Instructions
Routine adjustments required Prevent major problems
Dental checkups twice a year
Advise type of attachments Record attachment type and replacement #
in chart
Routine adjustments required Prevent major problems
Dental checkups twice a year
Advise type of attachments Record attachment type and replacement #
in chart
Summary - Attachment RPD’s 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
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
Summary - Esthetic Alternatives Summary - Esthetic Alternatives
No panacea significant disadvantages with some designs
Costs Managing expectations is important
Initially Long-term
No panacea significant disadvantages with some designs
Costs Managing expectations is important
Initially Long-term