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Published bySienna Rackley Modified over 10 years ago
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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 Design Underutilized
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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’ 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 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 Opti•Flex 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
GP’s should be aware of possibilities
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Advantages Esthetics Hygiene
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Advantages Stress distribution Single path of movement deep rest
directs stress along long axis Single path of movement
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Comfort - fewer lingual components
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
Can’t 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 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
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Summary - Esthetic Alternatives
No panacea significant disadvantages with some designs Costs Managing expectations is important Initially Long-term
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