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

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

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 Blockout

Hidden Clasp/Twin Flex Uses retentive undercut on proximal surface Requires sufficient undercut Space for clasp movement - hygiene

Hidden Clasp 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

Flexible ‘Gasket’ RPD’s Virginia Partial - elastomeric Cu-Sil - elastomeric Flexite/Valplast - thermoplastic No clasps Cu-Sil

Flexible ‘Gasket’ RPD’s Difficult to adjust, polish Tend to tear, rough surface Cu-Sil

Virginia Removable Partial Denture Silicone gasket around teeth Compensates for lost bone/gingival height Patients generally favour

Virginia Removable Partial Denture Hygiene Caries potential Liner lifespan

Virginia Removable Partial Denture Hygiene Caries potential Liner lifespan

‘Invisible’ Clasps (Optiflex) Non-metal, white Opti•Flex Coating applied to metal clasps

‘Invisible’ Clasps (Optiflex) Thick, white, ugly clasp? Porous (plaque) Fatigue Bulky (comfort)

Other alternatives Bonding composite to clasp arm Anodizing clasp arm Precision & Semi-Precision Removable Partial Dentures

Overview of Prosthetic Attachments

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

Uses for Attachments Fixed Partial Dentures Lack of draw between abutments Stress distribution

Uses for Attachments Removable partial dentures Comfort Less Bulk Within confines of Crown

Uses for Attachments Removable partial dentures Esthetics Retention

Uses for Attachments Overdentures Retention

Classifications of Attachments By type of Prosthesis Intracoronal / Extracoronal Precision / Semi-Precision

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

Precision Attachments Milled prostheses

Semiprecision Attachments Less intimate fit Some leeway or resilience Principle to relieve stress

Overdenture Attachments Bars Balls Studs Magnets

Overdenture Attachments

Scope of Practice Generally beyond scope of GP GP’s should be aware of possibilities

Advantages Esthetics Hygiene

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

Comfort - fewer lingual components Advantages Comfort - fewer lingual components

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

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

Disadvantages Overdenture flange must draw with attachments Can’t place flange in some undercuts

Disadvantages Technique sensitive Lab Parallelism Casting Processing acrylic

Disadvantages Technique sensitive Dentist Tissue base impression Relating Base to teeth

Contraindications Short clinical crowns Large pulps Dexterity problems Bruxers?

Design Considerations: Precision Attachments Frictional retention Resilient or stress releasing Allows movement Lose stress distributing properties

Design Considerations Tissue Health Critical Compressible tissue - recovery Affects occlusion

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

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

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

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

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