DISCUSS THE FACTORS THAT NEED

TO BE CONSIDERED IN SELECTING

THE RIGHT CLASP ASSEMBLY FOR

A REMOVABLE PARTIAL DENTURE

(RPD)

WELLINGTON J. NII DARKO

OUTLINE

• INTRODUCTION

•FACTORS TO CONSIDER

•CONCLUSION

INTRODUCTION

• A CLASP ASSEMBLY IS THE PART OF AN RPD THAT ACTS AS A DIRECT RETAINER AND/OR STABILIZER FOR THE PROSTHESIS BY PARTIALLY ENCOMPASSING OR CONTACTING AN ABUTMENT TOOTH

INTRODUCTION

•COMPONENTS•FUNCTIONS•TYPES OF CLASPS

FACTORS

• POSITION OF UNDERCUT

• HEALTH OF THE PERIODONTAL LIGAMENT

• SHAPE OF SULCUS

• OCCLUSION

• HYGIENE

• AESTHETICS/ APPEARANCE

• BRACING

• LENGTH OF THE CLASP

POSITION OF UNDERCUT

• Diagonal survey lines

• Larger undercut furthest away

• Typical designs

POSITION OF UNDERCUT

• Larger undercut nearer to saddle

• Ring clasp

• ‘I’ bar

POSITION OF UNDERCUT

• Tilted

• Low survey line on buccal surface

• High survey line on lingual surface

• Ring clasp

POSITION OF UNDERCUT

• High survey line

• Alter crown shape

• Flexible gingivally approaching clasp

• Occlusally approaching clasp(more flexible platinum-gold-paladium wrought wire clasp)

HEALTH OF THE PERIODONTAL LIGAMENT

• RETENTIVE CLASP TRANSMITS EXTRA FORCE TO THE PERIODONTIUM

• THE HEALTH OF THE PERIODONTIUM AS WELL AS THE AREA OF ATTACHMENT AND MAGNITUDE OF THE FORCE IS KEY TO THE REACTION TO THESE FORCES

• RPD SHOULD NOT BE PROVIDED FOR PEOPLE WITH ACTIVE PERIODONTAL DISEASE

HEALTH OF THE PERIODONTAL LIGAMENT

• OCCLUSALLY APPROACHING CLASPS ARE CONTRAINDICATED IN TEETH WITH REDUCED PERIODONTAL SUPPORT- IRRITATES THE TISSUES

• GINGIVALLY APPROACHNG CLASPS MORE SUITABLE FOR PERIODONTALLY COMPROMISED TEETH- MORE FLEXIBLE

HEALTH OF THE PERIODONTAL LIGAMENT

• Periodontal attachment loss

• Arrested disease process

• More damage if relatively inflexible clasp system used

• More flexible gingivally approaching clasp

• CAUTION- root caries. Wrought wire occlusally approaching clasp

SHAPE OF THE SULCUS

• Anatomical obstacles

• Prominent frenal attachment- trauma

• Surgical excision of frenal attachment

SHAPE OF THE SULCUS

• Undercut in the sulcus

• Arm spaced from ridge to prevent trauma

OCCLUSION

• OCCLUSALLY APPROACHING CLASP LOCATED ABOVE THE SURVEY LINE- SUFFICIENT SPACE NEEDED (TOOTH PREPARATION)

• GINGIVALLY APPROACHING CLASPS HAVE NO ROLE IN OCCLUSION

HYGIENE

• GINGIVALLY APPROACHING CLASP CROSSES THE GINGIVAL MARGIN

• ONE CLASP ENCOURAGES MORE PLAQUE THAN THE OTHER?

• GINGIVALLY APPROACHING CLASP COULD POSE GREATER THREAT IN PATIENTS WITH POOR ORAL HYGIENE

• INCREASED RISK OF ROOT CARIES ESPECIALLY WITH RECESSION

AESTHETICS/ APPEARANCE

• Either type can detract from appearance(anterior teeth)

• Gingivally approaching clasp has potential for being hidden in the disto buccal aspect of the tooth provided there is suitable undercut area

AESTHETICS/ APPEARANCE

• Tooth coloured polyoxymethylene occlusally approaching clasp as alternative

• Bulkier

• Require deeper undercut

• Less adjustable

• High cost

BRACING• Occlusally

approaching clasp more rigid and has more contact with tooth above survey line

• Transmits more horizontal force

• More efficient bracing component

LENGTH OF THE CLASP• Only terminal third

• Too much of clasp arm

• High force required

• Strain on periodontal ligament fibres

• Exceeds proportional limit of alloy- distortion of clasp

LENGTH OF THE CLASP

• Only at tip

• Length not restricted by the dimensions of the clasped tooth

• Can be increased to give greater flexibility

• Advantageous in tooth with reduced periodontal attachment

CONCLUSION• CLASP ASSEMBLY,FUNCTIONS, TYPES

• FACTORS INFLUENCING THE CHOICE OF CLASP ASSEMBLYPosition of undercutHealth of the periodontal ligamentShape of the sulcusOcclusionHygiene Aesthetics/ AppearanceBracing Length of clasp

REFERENCES• BRITISH DENTAL JOURNAL, VOLUME 189, NO. 12,

DECEMBER 23 2000

• DEEPAK, N.V., KARTHIKEYAN, R. TEXTBOOK OF PROSTHODONTICS. 4TH EDITION. JITENDAR P V. 2007.

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