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