impression techniques in rpd

“ Good technique pays off ” is not merely a motto to hang on a

wall but these are words of wisdom…

IMPRESSION TECHNIQUES

IN RPD

PRESENTED BY:APURVA THAMPI

1ST YR PG

CONTENTS• INTRODUCTION• TERMINOLOGIES• COMPLETE DENTURE IMPRESSION V/S RPD

IMPRESSION • IMPRESSION MATERIALS• ANATOMIC FORM AND FUNCTIONAL FORM• CONCEPT OF FUNCTIONAL IMPRESSION• NEED OF FUNCTIONAL IMPRESSION

• INDICATION FOR FUNCTIONAL IMPRESSION• OBJECTIVES OF FUNCTIONAL IMPRESSION

• DISTAL EXTENSION BASED PARTIAL DENTURE 3

CONTENTS• MCLEAN’S PHYSIOLOGIC IMPRESSION

TECHNIQUE• HINDEL’S MODIFICATIONS• FUNCTIONAL RELINING METHOD• FLUID WAX TECHNIQUE• SELECTIVE PRESSURE IMPRESSION• ALTERED CAST TECHNIQUE• MODIFICATIONS OF ALTERED CAST TECHNIQUE• REVIEW OF LITERATURE• SUMMARY• CONCLUSION• BIBLIOGRAPHY

INTRODUCTION

• Preservation of remaining tissues.• Contribute to trauma to the surrounding

tissues. • Stress tolerance of supporting anatomic

structures, • Denture base always moves towards the

supporting muscle. • Support for the partial denture to be

considered

Rationale behind using

RPD….

IMPRESSION

A NEGATIVE LIKENESS OR COPY IN REVERSE OF THE SURFACE OF AN OBJECT ; IMPRINT OF TEETH AND ADJACENT STRUCTURES FOR USE IN DENTISTRY.

GPT – 8

PARTIAL DENTURE IMPRESSION

A NEGATIVE LIKENESS OF A PART OR ALL OF A PARTIALLY EDENTULOUS ARCH –

GPT – 8

Terminology

A RECEPTACLE IN TO WHICH SUITABLE IMPRESSION MATERIAL IS PLACED TO MAKE NEGATIVE LIKENESS

ORA DEVICE THAT IS USED TO CARRY, CONFINE AND

CONTROL IMPRESSION MATERIAL WHILE MAKING AN IMPRESSION.

IMPRESSION TRAYS

RPD IMPRESSION VS COMPLETE DENTURE

COMPLETE DENTURE IMPRESSION THE EDENTULOUS MUCOSA WITH UNDERLYING BONE ONLY

PARTIAL DENTURE IMPRESSION RELATIVE SOFT YIELDING TISSUES (THE ORAL MUCOSA) + HARD UNYIELDING SUBSTANCE (THE REMAINING TEETH).

IMPRESSION MATERIALS• NON-ELASTIC• ELASTIC

• AQUEOUS HYDROCOLLOIDS• AGAR• ALGINATE

• NON-AQUEOUS ELASTOMERS• POLYSULFIDE• SILICONES

• CONDENSATION• ADDITION

• POLYETHER

Non-elastic

Elastic

Aqueous Hydrocolloids

Non-aqueous Elastomers

Polysulfide

Silicones

Polyether

Condensation

Addition

Agar (reversible)

Alginate (irreversible)

Plaster

Compound

ZnO - Eugenol

O’Brien Dental Materials & their Selection 1997

FACTORS THAT INFLUENCE THE SELECTION OF IMPRESSION MATERIALS ARE

Convenience of use

Time of manipulation and setting time

Operator training and preference

Need for special trays

BASED ON THE METHOD OF IMPRESSION MAKING

RESIDUAL RIDGE

Anatomic form

Functional form

ANATOMIC FORM• THE SURFACE OF THE RESIDUAL RIDGE AT

• IT IS THE SHAPE OF THE RIDGE BEFORE FUNCTIONAL LOAD IS APPLIED.

FUNCTIONAL FORM • IT MEANS THE SHAPE OF THE RESIDUAL RIDGE

TISSUE WHEN IT IS FUNCTIONING TO SUPPORT THE DENTURE BASE.

• IT IS THE SHAPE OF THE RIDGE AFTER FUNCTIONAL LOAD IS APPLIED.

16Anatomic or Resting form Supporting or Functional form

McCracken’s Removable Partial Prosthodontics 3rd edition

IMPRESSION MATERIALS ANATOMIC

IMPRESSIONS

• IRREVERSIBLE HYDROCOLLOID

• ELASTOMERIC IMPRESSION MATERIALS

• REVERSIBLE HYDROCOLLOID

FUNCTIONAL IMPRESSIONS

• FLUID WAXES• METALLIC PASTES• ELASTOMERIC IMPRESSION

MATERIALS• SOFT RELINERS

CONCEPT OF FUNCTIONAL IMPRESSION

THE TERM FUNCTIONAL IMPRESSION MEANS RECORDING THE FUNCTIONAL FORM OF THE RESIDUAL RIDGE TISSUE & TO OBTAIN UNIFORMITY OF SUPPORT

WHEN THE FUNCTIONAL LOAD IS APPLIED.

• Record and relate the tissues under uniform loading

• Distribute the load over as large an area as possible

• Accurately delineate the peripheral extent of the denture base

Therefore, the impression must…

INITIALLY…..

• APPLEGATE IMPRESSION WAX TO LOAD FUNCTIONALLY THE RESIDUAL RIDGE

• HINDEL FREE END DENTURE BASE UNDER MASTICATORY LOAD SHOULD BE RELATED TO METAL FRAMEWORK WHEN IT IS SEATED

• HOLMES USED FOUR DIFFERENT MATERIALS WITH ALTERED CAST TECHNIQUE

• LEUPOLD & KRATOCHVIL USED ZINC-OXIDE EUGENOL PASTE TO RECORD THE SHAPE OF RESIDUAL RIDGES

Leupold RJ, A comparative study of impression procedures for distal extension removable partial dentures. J Prosthet Dent 1966; 16:708.

• KRAMER & SINGER USED A DOUBLE IMPRESSION TECHNIQUE BASED ON LOAD DISTRIBUTION BY HINDEL

• MCCRACKEN FUNCTIONAL TECHNIQUE SHOULD BE USED WHEN CONSTRUCTING MANDIBULAR DISTAL EXTENSION BASED PARTIAL DENTURE

Leupold RJ, A comparative study of impression procedures for distal extension removable partial dentures. J Prosthet Dent 1966; 16:708.

NEED OF FUNCTIONAL IMPRESSION• THE DISPLACEABILITY OF THE MUCOSA OF RESIDUAL

RIDGE IS NOT UNIFORM.• IN CASES OF DISTAL EXTENSION BASED PARTIAL

DENTURE.• SHORT SPAN DISTAL EXTENSION BASES.

INDICATIONS FOR FUNCTIONAL IMPRESSION

Mandibular distal extension partial dentures • Mainly kennedy’s

class I & II edentulous arches.

OBJECTIVES OF FUNCTIONAL IMPRESSION(O.C. APPLEGATE)

To obtain the maximum area of coverage

Traumatic impact on any area must be avoided

At rest there must be no islands of ischemia

Under work loads all areas must receive massage stimuli. 24

SUPPORT OF DISTAL EXTENSION BASED PARTIAL DENTURE

minor support abutment teeth

major support elastic fibrous connective tissue pad

FACTORS INFLUENCING THE SUPPORT OF DISTAL EXTENSION BASE

• CONTOUR & QUALITY OF RESIDUAL RIDGE

Stewart’s clinical Removable partial denture prosthodontics – 4th ed

EXTENT OF RESIDUAL RIDGE COVERAGE BY THE DENTURE BASE

Stewart’s clinical Removable partial denture prosthodontics – 4th ed

TYPE & ACCURACY OF IMPRESSION REGISTRATION

Stewart’s clinical Removable partial denture prosthodontics – 4th edMcCracken’s Removable Partial Prosthodontics

ACCURACY OF FIT OF DENTURE BASE

29Stewart’s clinical Removable partial denture prosthodontics – 4th ed

•Design of partial denture framework

30McCracken’s Removable Partial Prosthodontics

TOTAL OCCLUSAL LOAD APPLIED

McCracken’s Removable Partial Prosthodontics

METHODS OF FUNCTIONAL IMPRESSION

PHYSIOLOGIC OR FUNCTIONAL IMPRESSION

SELECTED PRESSURE IMPRESSION TECHNIQUE

McLean's method

Functional relining method

Hindel’s modification for

McLean's method

The Fluid wax technique 32

MCLEAN’S PHYSIOLOGIC METHOD

Clinical Removable Partial Prosthodontics – Stewart. 3rd edition

McLean “The basic problem of partial denture

stabilization is to equalize the

resilient and non resilient support”

Custom tray over a preliminary cast

Functional impression of extension area under occlusal load

Hydrocolloid impression over the first impression made under finger pressure.

• FINGER PRESSURE NOT EQUAL TO BITING PRESSURE

• CLOSELY AFFECT THE DIRECT RETENTION

Disadvantages-

• IMPRESSION IS MADE WITH A MODIFIED TRAY APPLYING FINGER PRESSURE.

HINDEL’S MODIFICATION

HINDLE’S FINGER LOADING

• TISSUES ARE IN CONSTANT STAGE OF COMPRESSION

• ISCHEMIA AND BONE RESORPTION

• PREMATURE CONTACTS AT REST.

Disadvantage

THE MAIN PURPOSE OF THESE TECHNIQUES WAS TO RELATE AN IMPRESSION OF THE

EDENTULOUS RIDGE TO THE TEETH UNDER A FORM OF FUNCTIONAL LOADING.

FUNCTIONAL RELINE METHOD

LAYER OF RELIEF GIVEN

THE DENTURE IS PROCESSED & FITTED IN THE MOUTH IN CUSTOMARY MANNER, EXCEPT THAT THE RELIEF METAL IS LEFT IN PLACE.

It should be worn for a trial period of a week & all needed adjustments are done

THE RELIEF METAL IS STRIPPED OFF FROM THE ACRYLIC.

LOW FUSING MODELING COMPOUND IS ADDED IN INCREMENTS

BORDER MOLDING DONE.

1 MM MODELING PLASTIC IS REMOVED FROM THE INTAGLIO SURFACE.

IMPRESSION MADE USING ONE OF THE CORRECTIVE MATERIALS : FLUID WAX, ZINC-OXIDE EUGENOL PASTES

OR ANY ELASTOMERIC IMPRESSION MATERIAL.

FUNCTIONAL RELINE METHOD

DISADVANTAGE

• OCCLUSION MAY BE ALTERED SLIGHTLY • FINE LINE OF DEMARCATION BETWEEN THE

NEWLY ADDED & OLD RESIN OF THE DENTURE

FLUID WAX TECHNIQUE

53Clinical Removable Partial Prosthodontics – Stewart. 3rd edition

THE MOST FREQUENTLY USED WAXES ARE

Korrecta wax no. 4 - Dr. O.C.& S.G. Applegate at University of Michigan

IOWA wax -Developed by Dr.Smith at University of IOWA

Korrecta wax no. 4 is slightly more fluid than IOWA wax

THE ARMANTARIUM FOR FLUID WAX TECHNIQUE. (51- 54 DEGREE CELSIUS)

UNDERCUTS ELIMINATED USING BASEPLATE WAX

SEPARATING MEDIUM APPLIED TO THE CAST.

FRAMEWORK SEATED ON THE CAST.

TRAY MATERIAL ADAPTED 1-2 MM RELIEF BETWEEN RESIDUAL RIDGE AND INTAGLIO SURFACE

OF TRAY.

EXCESS MATERIAL REMOVED.

Tray border smoothed using laboratory bur.Should be 2 mm short of border extension

required.

FLUID WAX PAINTED ONTO THE INTAGLIO SURFACE OF TRAY (1 -2 MM)

Assembly seated in patients mouth.(5 -7 mins)

COMPLETED IMPRESSION.CHECK FOR PROPER TISSUE CONTACT

SELECTIVE TISSUE PLACEMENT IMPRESSION

METHOD

Direct more force to those portions of

ridge able to absorb stress

without adverse response & to

protect the areas of ridge which are

least able to absorb forces.

Framework tried on the cast

Tray outline marked for extension

FRAMEWORK WITH TRAY FABRICATED ON IT WITH HOLES ON ITS RIDGE.

AREAS IN WHICH RELIEF IS TO BE PROVIDED IS MARKED

TRAY IS BEING RELIEVED BEFORE THE FINAL

IMPRESSION IS MADE

Acrylic resin impression trays

with holes

Framework with tray tried

in patient’s mouth

Functional impression

made67

WELCOME BACK!

ALTERED CAST TECHNIQUE

ALTERED CAST : A FINAL CAST THAT IS REVISED IN PART BEFORE PROCESSING A DENTURE BASE—CALLED ALSO CORRECTED CAST, MODIFIED CAST

ALTERED CAST PARTIAL DENTURE IMPRESSION : A NEGATIVE LIKENESS OF A PORTION OR PORTIONS OF THE EDENTULOUS DENTURE BEARING AREA(S) MADE INDEPENDENT OF AND AFTER THE INITIAL IMPRESSION OF THE NATURAL TEETH.

• ALSO KNOWN AS CORRECTED CAST OR SPLIT CAST TECHNIQUE.

• IT IS MAINLY A MODIFICATION OF FUNCTIONAL IMPRESSION THROUGH LABORATORY PROCEDURE.

• FUNCTIONAL IMPRESSION FOR THIS TECHNIQUE CAN BE MADE USING ANY MENTIONED MATERIALS AND TECHNIQUES.

71Robert J. Leupold And Frank J. Kratochvil:An Altered-cast Procedure To Improve Tissue SupportFor Removable Partial Dentures .J Prosthet Dent 1965:672-679

Functional impression made

Final impression

72McCracken’s Removable Partial Prosthodontics 12thedition

Edentulous area cut from the master cast

Framework with attached impression seated on the master cast

It is imperative that all the rests occupy their proper position on the cast

Assembly from underside of the cast

Peripheral borders of the impression are

protected with utility wax

THE NEWLY OBTAINED ALTERED CAST WITH NEWLY ADDED STONE

ALTERNATE TECHNIQUES

Boxed elastomeric final impression in which edentulousridges have been separated with contoured baseplate

wax (A arrows) and sealed to anatomic contour ofimpression at base. Triangular wax bars (B arrows) are attached

to make dovetails (three separate compartments ofimpression).

Izharul Haque Ansari: A new procedure for separating the edentulous distal extension portion from the master cast when an altered cast is made. J Prosthet Dent 1994;72:666-9.

Mix of properly proportioned dental stone vibrated into three compartments of impression. Impression

must be overfilled to make solid base to prevent premature separation

Master east ready for duplication. Three to 5 mm thick base (line shown by arrow) below level of separating wax to

prevent premature separation while cast is handled to make the framework.

Base of the cast has been trimmed to line shown by arrows

immersion in boiling slurry water.

View from bottom of master cast after base has been trimmed to expose separating

wax and wax dovetails.

Edentulous portions separated from rest of master cast when removed from boiling clear slurry water.

Appearance of dovetails for additional retention for dental stone.

ALTERNATE BOXING TECHNIQUE

Leila Jahangiri, Patrick Mascarenhas and Donald Kitzis: A simple technique for boxing impressions for fabrication of altered casts. J Prosthet Dent 2001;85:519-20

Kevin D. Plummer:Technique for boxing an altered cast impression. J Prosthet Dent 1982;47:573-575

Replacement of impression and framework on master

cast after removal of edentulous distal extension

areas of cast.

Framework is luted to master cast with sticky wax.

Protection of teeth in master cast with irreversible

hydrocolloid.

Immersion of master cast and frame assembly within

supporting base.

Framework with corrected impression

is seated into a plaster mix contained bv wax boxing

sheet.Leila Jahangiri, Patrick Mascarenhas and Donald Kitzis: A simple technique for boxing impressions for

fabrication of altered casts. J Prosthet Dent 2001;85:519-20

• MAKE A SUPPORT BASE MIX WITH• 2 PARTS (26 ML) CORNSTARCH • 1 PART (13 ML) FINE PUMICE, AND • 1 PART (13 ML) PLASTER.

• ADD TO 115 ML WATER. POUR THE MATERIAL INTO A DENTURE FLASK.

• LET SET FOR 15 MINUTES. • SEPARATE MASTER CAST FROM THE SUPPORTING BASE AND

IRREVERSIBLE HYDROCOLLOID

• MIX 50% CORNSTARCH AND 50% WHITE MODELING PLASTER BY VOLUME WITH WATER TO A CREAMY CONSISTENCY. POUR THIS INTO THE BOXING WAX FORM. PLACE THE IMPRESSION IN THE MIXTURE.

• ALLOW THE MIXTURE TO SET FOR 10 MINUTES.• SEAL THE PREVIOUSLY USED BOXING WAX TO THE TRIMMED

BASE LEAVING AT LEAST 20 MM FROM THE TOP OF THE BOXING WAX TO THE HIGHEST POINT ON THE IMPRESSION.

• SOAK THE MASTER CAST IN SLURRY WATER FOR 5 MINUTES. POUR THE CAST USING THE SAME STONE AS THE ORIGINAL MASTER CAST. NO SEPARATING MEDIUM IS NEEDED

• WHEN THE STONE IS SET, REMOVE THE BOXING WAX AND PLACE THE CAST IN A WATER BATH OF 110” F

• SEPARATE THE PLASTER/CORNSTARCH MIXTURE WITH PLASTER PLIERS AND YOUR FINGERS.

Boxing wax placed around plaster base and cast leaving at least 20 mm from top of

wax to highest point on impression.

Completed altered cast.

ALTERNATE BOXING TECHNIQUE

Ming-Sheh Chen, W.A. Eichhold, Chao-Chin Chien and D.A. Curtis : An altered-cast impression technique that eliminates conventional cast dissecting and impression boxing. J Prosthet Dent 1987;57:471-474

94Ming-Sheh Chen, W.A. Eichhold, Chao-Chin Chien and D.A. Curtis : An altered-cast impression technique that eliminates conventional cast dissecting and impression boxing. J Prosthet Dent 1987;57:471-474

Tissue surface of final impression.

Lingual surface of custom tray. Only 3 mm of

impression material is left over and above border

flange.

Tissue surface of distal-extension with irreversible hydrocolloid pickup impression. Irreversible hydrocolloid is overextended 3

to 5 mm arounddistal-extension region.

Irreversible hydrocolloid pickup impression after trimming is completed.

Itshows relationship

between final impression, irreversible

hydrocolloid land, and stock metal tray.

Tissue surface of final impression is surrounded

by a uniform land of irreversible hydrocolloid.

Tissue surface of pickup impression. Note waxblockout (arrows) of all undesirable mechanical

undercuts.

Master cast obtained by this method.

ALTERNATIVE TO ALTERED CAST TECHNIQUE

Herman B. Dumbrigue and Josephine F. Esquivel: Selective-pressure single impression procedure for tooth-mucosa–supported removable partial dentures. J Prosthet Dent 1998;80:259-61

101Herman B. Dumbrigue and Josephine F. Esquivel: Selective-pressure single impression procedure for tooth-mucosa–supported removable partial dentures. J Prosthet Dent 1998;80:259-61

Aluminum foil and two sheets of baseplate wax

overdiagnostic cast before tray

fabrication.

Custom tray fabricated with extensions reduced 2 mm

short of vestibule.

Custom tray with softened modeling compoundreseated on diagnostic cast. Modeling compound

overresidual ridges shaped appropriately before

intraoral placement.

Border molding procedure completed.

Richard P. Frank et al :clinical outcome of altered cast impression procedure compared with use of A one piece castJ prosthet dent 2004;91:468-76

ALTERED CAST PROCEDURE DOES NOT OFFER SIGNIFICANT ADVANTAGES OVER ONE PIECE

CAST IF THE FOLLOWING STANDARDS ARE MET :

• COMPLETE EXTENSION OF IMPRESSION• USE OF MAGNIFICATION TO ADJUST AND

ENSURE COMPLETE SEATING OF THE FRAMEWORK.

• COVERAGE OF RETROMOLAR PAD AND BUCCAL SHELF AREA BY THE BASE

IMPRESSION TECHNIQUE FOR MAXILLARY REMOVABLE PARTIAL DENTURES

- C D. LEACH & T E. DONOVAN JPD 1983 (50)2,283-285

A MODIFICATION OF THE ALTERED CAST TECHNIQUE-RICHARD BAUMAN & JAMES .D B – JPD 1982(47) 2, 212-213

FOR THE PRODUCTION OF ACCURATE MASTER CAST THE IMPRESSION TECHNIQUE FAR OUT WEIGHTS THE SELECTION OF THE IMPRESSION MATERIAL.

CONCLUSION

1. GLOSSARY OF PROSTHODONTIC TERMS -8 TH EDN, 2005.

2. STEWART, RUDD, KUEBKER : CLINICAL REMOVABLE PARTIAL PROSTHODONTICS.

3. MCGIVNEY GP, ALAN B CARR DAVID T BROWN : MCCRACKEN’S REMOVABLE PARTIAL DENTURES-11 TH EDN.

4. KENNETH D RUDD, MORROW: DENTAL LAB, PROCEDURE FOR REMOVABLE PARTIAL DENTURES.

BIBLIOGRAPHY

AN ALTERED CAST PROCEDURE TO IMPROVE TISSUE SUPPORT FOR REMOVABLE PARTIAL DENTURES - R J. LEUPOLD, F J. KRATOCHVIL : JPD 1965(15), 4, 672- 678

SINGLE- TRAY DUAL- IMPRESSION TECHNIQUE FOR DISTAL EXTENSION PARTIAL DENTURES JOSEPH A. R- JPD 1970(24,1,41-46)

IMPRESSION TECHNIQUE FOR MAXILLARY REMOVABLE PARTIAL DENTURES- C D. LEACH & T E. DONOVAN JPD 1983 (50)2,283-285

AN ALTERED CAST IMPRESSION TECHNIQUE THAT ELIMINATES CONVENTIONAL CAST DISSECTING & IMPRESSSION BOXING - M S. CHEN AND et al - JPD 1987 (57) 4, 471-474

A MODIFICATION OF THE ALTERED CAST TECHNIQUE -RICHARD BAUMAN & JAMES .D B – JPD 1982(47) 2, 212-213

AN IMPRESSION TECHNIQUE TO MAKE NEW MASTER CAST FOR AN EXISTING REMOVABLE PARTIAL DENTURE -PHILIP J. R - JPD 1992 (67) 4, 488-490

THANK YOUAND

HAVE A PLEASANT DAY!

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