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CONTENTS

PAGE NO.

1. INTRODUCTION 01

2. REQUIREMENTS OFIMPRESSION MATERIAL 02

3. COLLOIDS 03

4. REVERSIB LE HYDROCOLLOIDS 05

5. DUPLICATION WITH REVERSIB LE HYDROCOLLOIDS 19

6. IRREVERSIB LE HYDROCOLLOIDS 26

7. DUPLICATION WITH IRREVERSIB LE HYDROCOLLOIDS 438. LAMINATE TECHNIQUE 45

9. RECENT ADVANCES 48

10. CONCLUSION 5311. BIB LIOGRAPHY 54

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LIST OF PHOTOGRAPHS

PHOTO 01 REVERSIBLE HYDROCOLLOIDS

PHOTO 02 IRREVERSIB LE HYDROCOLLOIDS

PHOTO 03 TRAY MATERIAL (REVERSIBLE HYDROCOLLOID)

PHOTO 04 SYRINGE MATERIAL (REVERSIB LEHYDROCOLLOID)

PHOTO 05 RED ALGA

PHOTO 06 ARMAMENTARIUM FOR PREPARATION OF AGAR-AGAR

IMPRESSION MATERIAL

PHOTO 07 LIQUEFYING UNIT

PHOTO 08 TEMPERING UNIT

PHOTO 09 PLACEMENT OF SYRINGE MATERIAL

PHOTO 10 PLACEMENT OF TRAY MATERIAL

PHOTO 11 REVERSIBLE HYDROCOLLOID

PHOTO 12 CHOPPING AGAR INTO SMALL PIECES

PHOTO 13 AGAR ON THE TOP PORTION DOUBLEBOILER

PHOTO 14 EXPANDED VIEW OF THE DUPLICATING FLASK

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PHOTO 15 ASSEMBLEDVIEW OF THE DUPLICATING FLASK

PHOTO 16 CASTING THE FLASK

PHOTO 17 STORAGE UNIT CONTAINING PREPARED DUPLICATING

MATERIAL

PHOTO 18 POURING OF AGAR INTO THE FLASK

PHOTO 19 POURING OF AGAR UNDER STORAGE UNIT

PHOTO 20 TRAY OF RUNNING TAP WATER

PHOTO 21 REMOVING CAST FROM THE FLASK

PHOTO 22 HYDROCOLLOID MOLD

PHOTO 23 MAKING OF ALGINATEIMPRESSION

PHOTO 24 POURING OF THE ALGINATEIMPRESSION

PHOTO 25 AUTOMATIC MIXING FOR ALGINATE MATERIAL

PHOTO 26 LAMINATEIMPRESSION TECHNIQUE

PHOTO 27 HYDROGUM

PHOTO 28 NEOCOLLOID

PHOTO 29 TR I ALGIN

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Introduction

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Introduction

INTRODUCTION

Impressionmaterialsare use dto registerorreproducethe for man d

relationshipof th e teeth wit horaltissues . In dentistry wemakeimpressionof

teethandtheirsupportingst ructure sin cludegingival,alveolar bone or

residualridge,hardan dsoftpalatean d frenums whichar emuscle

attachments .

Thesereplicasaidsinth e construc tionofacceptableprosthesisof th e

missingstructures . Theimpressionis anegativereproduction,whileth e

replica (modelor cast )is the positivereproduc tion.

The impressionmust bean accuratedupl icationof th ehardandsoft

tissuesof interestan dsh ould bestableenough toallow disinfectionand

productionofamodel .no tal lthe impressionmaterialsar e compatible wit h

al lmodelmaterials .Because impression materialsar e used foravarietyof

purposes,thereis wide varietyof products available tomakeimpressionof

oraltissues.

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Requirements ofImpression Material

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Colloids

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Colloids

COLLOIDS

Colloidsar eoften classifie dasth e fourthstateof matter, th e colloidal

state, becauseof thesedifferences, inth est ruc ture, constitutionan d

rea ctions,

How doesa colloiddi ffer from asolidandli quid ? Lets asat firstexaminea

solutionof suga ran d water .Thesuga rmolecule s(solute ) ar eas sume d to be

dispersedin formallyin the water (solvent). Thereisno visible,physical

separation betweenth esoluble an d th esolventmolecule s . if the sugar

molecule sar ereplaced with large,visible,on -so lub le particle ssuchassand

(in water)th esystemistermedasuspension .if theseparticles become liq uids,

likeoi lin water,thesystem is calledasemulsion,The suspendedparticlesor

li quiddroplets, whi chdonotreadilydi ff use and tendto fal loutof th e

suspendingmedium unlessme chanicallyor chemicallyheldinpl ace . some

where betweenth eextremesof th everysmallmoleculesinth eso lution,an d

verylargeparticle sin suspension is the colloidso lutionorge l.

Truesolutionexitsasasinglephase. However, both the colloidan d

th esuspensionhavetwo phasesdispersedan ddispersion . inth e colloid th e

particle shi the dispersedphase consistof molecules thatar eheldtogether

either byprimaryorse condary forces . The sizeof th e colloidparticle srange

fro mIto 200 mm . The twophasesar eeither compatible ornon compatible .

Thusth edispersedphasemay notstaysuspendedinthe dispersionmedium.

In additiontoth eparticlesize, factors commontoan ytwophase

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Colloids

system, System, forexamplesurfaceenergy,surface chargean d wetability,

determineth est abilityof th e colloid.

Types of colloid:

Colloidalsubstances can be com binationofany statesof mater with th e

exceptionof gaseousstate. Forexample,li quid sorsolidsin ai rar e

calledaerosolsgases li quids orsolidsin li quid sar e calledlysosols, . gases

li quid san dsolidsinsolids called foams,solidemulsionsan dsolid

suspensionsrespectively. Allthe colloidaldispersionsare termedso lution

regardlessof th etypeof dispersionphase. Whe naliquid is usedas the

dispersionphase,he colloids calledlyohobic forliq uidpr eferringdispersed

spe cie san dlyohobic forliquidavoidingdispersedspecies The colloidal

materialuse d formakingimpressionsar eagaroralgindissolvedin water,

he ncethe namehydrocolloids.

The hydrocolloid impression materials are of t wo types:

1. Reversible hydrocolloid (A ga r Agar)2. Irreversiblehydrocolloid(A lginate)

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Reversible Hydrocolloid

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REVERSIBLE HYDROCOLLOID (ADA specification no.11)

Aga r underth e classificationof impressionmaterials is grouped under

reversible hydrocolloidset bytemperature changeandiselastic in

na ture .

A complexsulfatedpolymerof galactose units,extracted fromgelidium

cartilaginousgarcilaria con feruoides,andrelatedredalgae. Itisa

muc ilaginoussubstance thatmeltsatapproximately 100 c an dsolidifie sinto

age latapproximately 40 c. itis no tdigestedbymost becteriaandis use d us

agelin dental impressionmaterialsandasolid cu ltuemediami croorganism

(Accordingto GPT)

Reversible hydrocolloidsare available into forms:

1. Traymaterial2. SyringematerialHISTORY :

Aga r Agar hydrocolloids were first use din in dustryin 1925. The

firsttoothimpressons weremadein 197. Untilthat timeth e chemicals

usedto strengthenthe hydrocolloidwereharmfu ltohuma ntissue.

Hormer Verson Reedinhi sarticleregardingagarhaydrocolloid

stated th e useof agarin th eyear 1938 wherehe use d Agar Aga r chipsor

flakes whi ch wer emixedin toapot of boiling wateran dvarious

ingredients wereaddedintothe pot . whichincludedlong cotton

filaments, flakeof glueantibacterial chemicals,antifungal chemicals,

as bestos fibers,an dsubstance calledFiller

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Earth, to give th ematerial body . Thi s was boiled until it wasthe proper

consistency,then allowed to cool, untilitre acheda temperatureof

approximately 150 to 160 f. Watertrays wereno tavailable atthattime.

Smooth trays were use dan d undercuts weremade with sti cky wax or

compoundstops. The postdamstrayextensions were made in compound th e

tary was filled with th ehydrocolloidandpl acedina basinof waterat

approximately 120 to 125 andleft few minute s it wastheninsertedin to the

studentsmo uth an dheldasstillas possible. Anassistant(usuallyanother

student) filleda waterbu lb syringe with col dwateran dsquirtedthis col d

waterinto th estudentsmouth . Afte ratimethe impression wasremoved

an dif acc eptable atall, waspoure din some cas tstonematerial.

The abovetechnique workedoutafte rmanytrialan derror

pr ocedures.Later,alargemetalmixingsyringe waspurchased. The

material was pr ocessedas statedpreviouslyan d wasallowedto coo l

untilitgelled. Thematerial wasthen cutin to a cylindricalshapeto fit

th esyringe,pl ace in the mixingsyringean dpl aced into boiling water.

Whe nth ematerialre ache dso lstate,an internalplunger waspushed upand

do wn an dth ematerial wasmixed. The n th etrays were loaded from th e th e

mixingsyringe,placedintempering wateratabout 120F for few min ute san d

removed. Anyremainingsurfacemoisture wasremoved befor e th e tray was

insertedinth emouth.

The coolingpro cess wasthe same untilth e water coolertray

cam eto th emarket,mainlythrough th eeffortsof Thompsonan dothers.

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Thesea weed,orkelp,plantis th e tallestplant, eventaller thanth e

giantRedwood tree. Someof th e bes tseaweed (Kelp ) plantsgr ow in

aree f off the coastof lo wer Cal ifornia. The heightof the seawee dis

controlledbyth edepthof the reefs floor. Be for e world warII , Japanese

cam eto thisre ef andharvestedth eplants,loaded themonshipsan dtook

themto Japan wherethe sea weed was cleansed, boiled in water,andallowed

to ge l. Hegel wastransported back to Cal ifornia, whereit was converted

intoagaragarhydrocolloid for th edentalpr ofession.

Wit hth eadventof world warII , Japaneseships weredeniedthe useof

th esealanesto Cali fornia,an dth eproduc tionofagaragarhydrocolloid

closed this brough tabout th e discoveryof the alginates,orirreversible

hydrocolloids.

AAGAR HYDROCOLLOID:

Definition: itis an aqueousimpression materialused forre cording

maximumdetail,suchas thatrequiredto produc edies for fixedrestorations.

A gelatinous colloidalextractofredalga usedagellingagentan dprincipal

effective ingredientinreversiblehydrocolloid impressionmaterials.

Sol Gel Transformation : if th e concentrationof the dispersedphaseinthe

hydrocolloidis suf ficientthe solma y be changedto asemisolidmaterial

kno wnasge l. In th ege lstatedispersedphaseagglomerates forming chains

ormicelles. The fibrilsmay branchandintermeshto from a brushheap

struc ture.

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In agar th e fibrilsare heldtogether bysecondarymolecu la r forces. These

bondsarevery weakandthey breakatslightlyelevated temperatures and

becom ereestablishedas the hydrocolloidcools to room temperature.The

sti ffnessan dstrengthof th ege lar edirectl yrelatedtoth e brushhelpdensity

or concentration. Eg. The greaterthenumberof th edispersedphasein

th esol,the greaterth enumberof fibrils formedon gelation.

In agaralargepartof th est ructureof th ege lis occupied by water. If

th e water contentof th ege l is reduc edthe ge l willshrink,an dif the geltakes

up water,it willexpandorswell.

The ge lmay lose water byevaporation fro mit ssurfaceo byexudation

of fluidontothe surface byapr ocess knownas syneresis. The Exudates that

appearsonth esurfaceof the gelduringan daftersyneresisis notpure water.

Itma y beeitheralkalineoracidepending upon the compositionof the gel . If

th egelisplacedin waterth ege lswells becauseof absorptionof waterand

th epro ces sis calledim bibitions.

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GELTION PROCESS:

Thesettingof reversible hydrocolloidis calledgelation . the physical change

fro mso lto gel,andviceversa in duc ed bytemperature change . the

hydrocolloidge ldoesno treturnto th esolat th esametemperature at which

itsolidifie d. Thege lmust beheatedtoa higher temperatureknownas

li quefactiontemperature(70 to 100)to returnto it sso l condition. When

cooled th ematerialremainsaso l far below the liquificationtemperature .it

transformstoin to age l between 37 an d 50 th etemperature lag betweenth e

gelationtemperaturean dli quefactiondepends upo nseveral factorsin cluding

th emolecula r weightthe purityof agaran dthe ratioofagar to other

ingredients .

PROPERTIES:

Gelation temperature : afte r boiling for 8 mi nuteth ematerialshould be

fluidenough to extruded fro m th e container. Afte rtemperingth eso lsh ould

behomogenousan dshouldset between 37 c an d 45 c when cooled,as

req uired by ADA spe cificationrequires No. 11 for Agarimpressions.

PERMANENT DEFORMATION:

The ADA sp ecificationre quires thatth epermanenetdeformation beless than

1.5% afterthe material compressed 10% for 30 se condsmosttray typesof

agarimpressionmaterialreadily,meetthisrequirement with valuesof about

1%. This permanentde formationisslightlylowerthanthatof alginate

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impressionmaterial. However,areasonableth icknessof impressionmaterial

sho uld bepresent betweenth e trayandthe undercutareaso that compression

higher than 10% doesno toccur, si ncehigher compressionre sults inhigher

permanentde formation.

Flexibility: The ADA sp ecificationre quirement for flexibilityallowsa

rangeof 4% to 15% atastressof 14.2 psi (1000gm\ cm)an dmostagar

impressionmaterialmeetthisrequirement.

Strength:th e compressivestrengthofa typicalagarimpressionsystem is

8000gm\ cm which farexceedsthe ADA sp ecificationminimumof

2500gm\ cm th etearstrengthof agar is 700gm \cm.

Sin ceagar impressionar evis coelastic. The strengthpropertiesaretime

dependentan dhigher compressiveand tearstrengthagarha dhigherrateof

loading .

Dimensional Stability: Aga rimpressionar e beststoredin 100% relative

humidityif th egypsummodels cannot bepepaed immediately. Evenin 100%

humiditythis can bestoredonly foralimitedtimesuc hason eho ur without

shrinkageof th e impression caused bysyneesis .

Manipulation :

Armamentarium

1) Uni t which is having three cha mbers .The first cha mberis knownas liq uefication cham ber,

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Secon d cha mberiskn own as storage uni t .

Thirdisknown as tempering uni t.

Theimpression Procedure:

Gingivaldisplacementmaterial:

A wide assortmentof chemical sare usedin conj uc tion with cor d,yarn,

thread,ringsandothermaterials to relaxan ddisplacethe gingivaltissue

an dto controlhemorrhaging . somein use todayar eepinephrine,alum,

aluminimumpotassiumsulfat e,aluminimum chloridean dhemogent.

Preparation of hydrocolloid impression material :

Cleanliness,maintenance,an d careof th e conditionarandstrict

adherenttotimean d temperaturear emandatoryin th eagaragar

hydrocolloidimpressionte chnique.

The waterpotssh ould be cleanan d freeof any foreignmaterial,e, wax

calciumdeposits,an d scumfro mthe boiling water . conditionersstay cla n

fai lureto keepth post clean willre sultintempaturevariations . clean,coo l,

distilled water is paledinth ethreepots. The conditioner is turnedon . thirty

mi nute s,should beallowed for th e waterto reachthe desiredtemperatures

before pr oceeding . the boilingpo ttemperaturesh ould be 150f,andthe

temperingpo tshould be 11 0 to 115F.

The cap son th e tubesof hydrocolloidar etightened. Thetubesar epl acedin

th e conditioner, cap sdo wnif th eglass car pules of syringematerial

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ar e being use d,pl acethe rub berplungersdown. The wateris brough tto boil

an d boilingis continued for 10 mi nute s tubesthathave to bereboiledshould

no w haveanextra 2 mi nutes addedtoth e 10 min ute s . longer boilingharms

th ematerial . the tubesshould bele ftin th e boilingcompartmentabout 15

mi nute safte rth e boilingstops . then tub esof hydrocolloidare transferred to

th etemperingpo t.th esyringematerialis le ft in the boilingpo tif he metalor

plastic syringe is used,th e cap on the needleisremoved,andthe sti ckof

syringematerialis pl acedon th esyringeplunger,an d inserted in toth e

syringeth eplunger is pressedon,th e cap onth eneedleis screwedon,th us

formingavaccumin the syringean dth eneedle is placedenddo wn into th e

conditioner.

Tooth preparation:

Whe nthe agaragarhydrocolloidimpressionte chniqueisto be use d,afew

modificationsotherthanth e conventionalprepareationsh ould bedone . th e

groovesin threequartersof fiftheightpreparationsho uld belarger whe nth e

hydrocolloidimpressionmaterialis use dthenaregroovesina normal

preparation .

Box preparationssh ould be use dinsteadof groovesin the posteriorteeth

whenhydrocolloidmaterial is used to maketheimpression .

Tryassho uld beselectedandtriedinth e patientsmouth befor eth e

impressionmaterialispl acedinthem .

Theresh ould be 3 mmof impressionmaterialaroundth eteethocclusally

an dlaterally. For bestresults,threestopsshould be used to give th e

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tripodeffect. If possibleth estopsshouldreston the incisalsurfacesof

anteriorteethandocclusalsurfacesof the rightan dle ftposteriorteeth . if

thereare noteethavailable ,or if these theethhave been prepared,soft

tissuestopareasma y beselecte d.

Preimpression steps:

The preparedarea,abutments,andgingival tissuesare examined. A

sprayofdi luted, warmmo uth wash of choi ceis anexcellentmeansof

washingand

cleaningthe area. Adequat e cottonrollsar epla ced; cottonrollholdersare

mandatoryin th emandibu la rareas. The cotton trollsmust bepl acedand

maintainedapi callytoth egingival crestarea. If theyar eallowedtoexert

pressure onthisarea,th egingivaldisplacementpr ocedure wil l bew in vain.

Salivaejectorsar epl acedinth emo uth and th epreparedareaisdried

cauti ously tori dth esurfaceof moisture . The gingivaldisplacementmaterial

is pl acedaround th eprepared teeth to the circumferenceof the prepration.

No

loseendssho uld la poverthe gingivalissueorhangoutoverthe labialor

lingualtissue. A smalltip endmay beleftin the interproximalarea

to ai dnremoval.

The preparedareaandthe oral cavitysh ould bekept fre eof excesiver

moisture fro mth etimethe displacementmaterialisplaced untilthe

impressionhas beenremoved.

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Impression making:

Theagaragarhydrocolloidthatha s bee nstoredis no w removedandpl aced

in th eselecte dtray. The materialsho uld bepl acedinth etray without

lappingortrappingai r. Thepalatalareaof the maxillarytrayneedno t be

filled unlessth epatientha sadeepvaultin th epalate barorstrapmajor

connecto ris to be used. The filledtrayispl acedin th e tempering bat hat 110

to 115 F for 5 to 10 minute sor to the individualdentistsdesireafte ra few

impressionshave beenmade,th edentistha sagoodideaof the timean d

temperature bes tsuitedtohi sorhe rte chnique.

The syringe is removeds fromth e bath,an dsomematerialis extruded fro m

th eneedleto eliminatean y contaminatedsyringematerial. The displacement

materialisremoved,th eareaisinspectedquickly,andthe syringeneedleis

pl aced in the free gingivalsulcus. Thematerialis injecte d ce\arefu ll yar oud

th epreparedabu tment. Car emust betakenno ttotrapany airduring th e

pr ocedure. Theneedlesh ouldnot betakenb not to trapan yairtduring th e

pr ocedure. Theneedle sh ouldnotliftedoutandreplaceinth ematerialas

this will cause airpockets. Anyex ces ssyringematerialmay bequicklypl ace

in th eocclusa lsurfacesof th e unpreparedteethtoaidinth eeliminationof

voidsinth eimpressionof these w\areas.

The preparedan d filledtrayisremoved from the tempering bath befor e

of duringthe insertionof the syringematerialaguaz esq uar eis pl acedon

th esyrfaceto blotany excess waterand th ehosesare connecte d to the tray.

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Assoonath esyringematerialha s beenlaiddownon th eabu tments,th e

guaze isremovedan d th etrayisinsertedin the mouth . The gauzesquare

sho uld leaveanimprintof th eguaze onthe hydrocolloid whenitis removed.

If th eimprint is notvisible, there is tillexcessivemoistureon tesurfaceof

th ehydrocolloid,th esurfacemust be blottedagain befor epr oceeding. The

useof mirrioran dagentlerockingmotion willai d in the pla cementof the

tray. Thestops willaidinguidingan dsettingof the tray.

The patentsho uld beinth e uprightposition,an d th earchofpreparedteeth

sho uld beparallel withth e floor. Thepatientshould beinarelaxedposition,

an dthe lipssh ould berelaxed. Duringandafte rinsertionof th emandibula r

tray,th epatientstonguesho uld beraised upan d backinto th epalatalarea

an dthenrelaxed intoit snormalpositionorle fttorestonthe upperpartof

th etray. Thetraysho uld beplacedan dheldin the mouth bythe dentistitis

removed from th emouth .

Rth e water is allowedto circulatethrough th etubes an d th etray forthe

desiredperiodof time. The watersho uld be 65 to 72Fandsh ould be use d for

no tlessthan 5 mi nutes . The trayis removed withasnapoutmethod. Aftwer

th eimpressionhas beenmadeitis pl ac4dinto whereglassorastainless

steela covereddish in which 2% potassiumsulfat esolutionha s beenpla ced.

The potassiumsulfat egivesahardersurfaceto th estonedi ematerial.

Some,if notall,agaragarhydrocolloid contain boraxas a filler.

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Whe nth e impressionsetson th e bracketta blejust fora few mi nutes,

athin fil mof water formsonth esurface . The water fil m contains borax that

ha s bee nle eched fromth ehydrocolloidmaterial . boraxretards th ese tof di e

stone,andthe wayter fil m contaminatesth esurfaceof th edie,re sultingina

weaksurface that willremaininthe agaragarhydrocolloidmaterial when

th ediesareremoved. Thepotassiumsulfat eactsas an accelerator forthe

stone, counteractingthe retardingeffectof th e borax,th usproduc in ga

harderan dsharperdi e.

The potassiumsulfat eshouldnot be washedoutof the impressions befor e

th ediesarepo ured. The impressionmust be blo wn car efu lly,the imopression

sho uldno t bedehydrated, bu tan excessiveam ountof waterormoisture

sho uldno t beleftin the impression. The working catshould bepoured

immediatelyafterthe removal fro m th epotassiumsulfate bath . Excess water

ma y be blotted usingthe end cornerof a facia ltissue. Theocclusaldepths

ar e che cked carefu lly for waterdroplets. The stone cas t wil lhaveholesin

areasin whichth e waterha s beenleft.

CARE OF THE IMPRESSION ;

Procedure 1 :the agrreversible hydrocolloid impressionsho uld bepoure d

immediately. As with alginate impression,lengthyexposure of th e

hydrocolloidimpressionto ai r can re sultin dehydrationan d corresponding

distrotion.

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In accordance with man ufactacturessuggestions,soakthe impressionin

th erecommendedso lution. Suchas 2% potassiumsuifate, forrecommended

periodof time.Removeexcess moisture from th eimpression wit hagentle

streamofair. Dono t use astrong blastof ai rasth eimpressionmay be

separated from the tray. Moistureaccumuiationin tooth indentationsmay be

removed by usingabsorbenttissueoran ai rstringe.

Pouring the stone :

Afterproportioningthe stoneitis amechanicalspatulator underre duc ed

atmospheric pressure .

y Usegentlevibrationand car efu ll y flo w storeintothe impression.

y Addstoneinsmallamounttoon edistal cornerof the impressionandtiltth eimpression to allow the stoneto flo w intoeachtooth

indentations. Watchtheleadingedgeofthestoneasitflowsintoindentations .to

preventbridgingandresultantvoids.

y Buildroughareas with undercutsonthe uppersurfaceofthestoneofthe firststage.

y Suspendthepouredimpressioninatrayholdertopreventcontactofanyhydrocolloidwiththe benchtop.

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y Afterthe firstpourhassetandtheheatof crystallizationis beginningto cool,

placetheimpression withthestonein clearslurry waterfor3 to 5 minutes.

y Afterthis baseispouredwiththestone usingthesame W:Pratio.

y Separatetheimpression fromthe cast45 minutesto 1 hoursafterpouringthe first

stage.

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Duplication With


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Duplication procedure

Duplication :Theprocedureofaccuratelyreproducinga cast.

Refractory cast:a castmadeofmaterialsthatwillwithstandhightemperatures

withoutdisintegratingwhen usedinpartialdenture castingtechniqueshasexpansionto

compensate formetalshrinkage.

Reversiblehydrocolloid(Agar) molds: Reversiblehydrocolloidis usedmostoftento

makethemoldforduplicationsincethismaterialisheatreversibleitmay bereused

many

times . alginateirreversiblehydrocolloidmayalso be usedbyincreasingthevolumeof

waterto 3 timesthevolume used forregularimpressionhoweverreversiblehydrocolloid

isseentoproduceasmooth castandislessexpensive.

A duplicatingflaskwillbe usedtosupportcastandconfinethehydrocolloidsinceitaids

in controllingshrinkageitisasimpledesign consistingof 3 piecesthe basethe bodyand

thereservoirringtwoholesinthetopsurfaceofthe bodypermitairtoescapeasthe

duplicatingmaterialfillsisthe flask.

Procedures:

1. Themastercastmustbethoroughlysoakedis clearslurry water. A minimumof30 minutessoakingis usuallyrequired.

2. Placethe castonthe baseoftheduplicatingflasktomakethatthespacearoundandabovethe castinsufficientfortheduplicatingmaterial.

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Thereshouldbe (0.63) clearanceinalldirections. Ifthereisnoenoughspacethe

castmustbetrimmedoralargerflaskused.

3. The castis centeredonthe baseofthe flaskanditissecuredwiththreesmallpiecesofmodelingclay.

4. Theouterrimofthe flaskbaseis filledwithmodelingclayandtheseatthebodyofthe flaskfirmlyintotherim. Thisactasthesealandpreventsthe

hydrocolloidfromescaping. itisasloactasaninsultingarea whenthe flask

is beingcooledslowly.

5. Placethereservoirringinthe bodyofthe flask.

6. Placesmallballofmodelingclayadjacentto cutbynotoverthetwoventholesinthetopsurfaceofthe bodyofthe flask. These willbe usedto close

thehole whentheduplicationmaterialhas filledthe flask,antheairhas

escaped.

7. Checkthetemperatureoftheduplicatingmaterialinthestorage unit. Adouble boilercanalso be used. Fillthetopofthedouble boilerwithagarand

bottomofthe boilerwith water. Putthe boilertogetherandplaceiton fire,

andboilthe water. Removethe boilerfromthe fireandallow theagarto cool

for1 houruntilitreaches between 57oto 60o C.

8. Filltheduplicatingflaskwithagar. Ifthestorage unitis used, centertheduplicatingflaskunderthepouringspoutandopenthevalue. A stream

diameterof aleadpencilisdesired.

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9. Continueto fillthe flaskunittheagarstarstorunoutoftheholeontopoftheflask. Blocktheholes withmodelingplastic untilthe flaskandreservoirare

completely filled.

10.Cooltheduplicatingmaterialinthe flaskinanexactingmanner. Itshouldbeplacedonatrayof coolrunningtap water. The watershouldcontactonlythe

baseonthe flask. Coolingthe baseofthe flaskcausesthehydrocolloidto

shrinkinthedirectionofthelowertemperatureortowardthe cast,thus

causingittoadaptmore closelytothe cast. Thereservoirringsuppliesthe

additionalmaterialneededto compensate fortheshrinkage. Leavethe flask

inthe waterforatleast45 minutesto coolitcompletely .

11.Removethe flaskfromthe waterandremovethereservoirring. Usethesharpknife,andtrimthehydrocolloidflush withthetopofthe flask.

12.Invertthe flaskandgentlytwistandremovethe baseofthe flask.

13.Ifthemodelingplastic retention werenotremovedwith based,theyshouldberemovednow.

14.Investthetripof 2 knivesinthedepressiononeachsideofthe castmade bysmallamountsofmodelingclaythatheldthe cast. Pry upwardusingtheswift

actionandequalpressureonthe bothknives. The castmaybeloose firstwith

gentle blastofairaroundthe bordersofthe castbase.

15.Afterthe castisremoved,examinethehydrocolloidcarefully fortears 0voids. Tearsmayindicatethatthehydrocolloidisoldorspoiledandneeds

replacing. Ifitisacceptable,pouritimmediately.

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Modifications andImprovement of Techniques:

A technique usetoobtainedsharpermore completesubgingivaldetailindifficult

subgingivalpreparationisdescribedby Nichols C.F. andWoelfelJ.B. in which useof

milddetergentinthepreparedteethisdescribed. Thedetergentusedinivoryliquidsoap.

The useofdetergentgivessharper,more completesubgingival preprations.

Afterthetoothpreparationtheretraction cordsareplacedintothegingival

(theepinephrineimpregnatedcoilsis used0.5 mg).

Justbeforemakingtheimpressiontheretraction codeareremovedandthereasonis f

lushedwith wateranddriedwithair. The No. 000 brushisdippedintothedetergent

solutionandisappliedonthegingivalsulcusandcompletelyoverthepreparedtooth.

Thedetergentfacilities flow by breakingthesurfacetensionandlesseningtonumberof

bubblesintheimpressionmaterial. Italsoactsalubricant,presentingthenoftheedgeof

thehydrocolloidfromadheringinsideofthesulcularwallandtearingonremovalof

impression.

Aftermakingtheimpressionafterthegelledimpressiontrayisremoved fromthemouth.

Thesulculardetergentapplicationallowsthehydrocolloidmaterialtoslideaway without

tearingandtoaccuratelyreproducetheexcellentmarginaldetail.

______________________________________________________________________

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DISINFECTION :

Studiesof cross contaminationinthedentaloperatorylaboratoryandofdental

prosthesis

Have confirmedbacterialcolonization,disseminationandtransmittance. Theaseptic

technique,asapremiseofgooddentalpracticedemandsasterileenvironmentwhenever

possible.

Thereversiblehydrocolloidconditioningunit, whichincludes 3 watertanksatvarying

temperature, boilsmaintainsandtemperstheimpressionmaterial. Thehydrocolloidis

transferredbetween both untilitisinsertedintothepatientsmouth. Bydesignmany

sourcesof contamination can be cited,tapanddentalunitwaterareknownto certain

bacteria. Cross contamination frompatienttotankispossible;maintainingsterile water

tankfrom consecutivepatientisdifficult. Accordinglyhydrocolloidmaterialmodified

withvarioussubstratesispotentiallyandidealmedium forbacterialgrowth. Inthetestof

4 hydrocolloidconditioningwererandomlytestedforbacterialcontamination. Allwere

contaminatedbeyondU.S. Armyacceptablelimitsofpotability. Thepredominant

bacterialwerepsedumonsaeruginoseandp.maltophilia fromall4 units. A protocolof

aseptic techniquemustbeestablishedandfollowedforthe useofreversiblehydrocolloid

units containingwater. Ideallythe watershouldbechangedbetweeneachpatientandthe

unitstabilizedwithanon corrosive chemical. A recordshouldbemadeof caretakers

name,dateandtimeofsterilizationanditshouldbemadeof caretakersname,dateand

timeofsterilizationanditshouldbeaffixedtothe unit. Recommendations callforthe

additionof iodophororotherchemicalinthe waterofthetemperingbath.

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Howevertherequiredconcentrationandtimesofsterilizationmustbereviewed. The 3

chemicalsolutionthatareeffective forsterilizationaresodiumhypochlorite 0.5%, for30

minutes,iodophor0.5% for30 minutesandglutaraldehyde 2% for10 hours.

IMBIBITION AND SYNERESIS:

Asmightbeexpectedfromthestructureofthehydrocolloids,greatpartofthevolumeof

thegelisoccupiedbythe water. Ifthe watercontentofthegelisreduved,thegelwil

shrink,andifthegelthentakes up water,thegelwillexpandorswell. Suchpossible

changesindimensionareof considerableimportanceindentistry. Ifthesematerialsare

usedforobtainingimpressions,any changeindimensionoftheimpressionafterithas

beenremoved formthemouthisasourceoferror.

Thegelmaylose waterbyevaporation fromitssurface,orbytheexudingof fluidbya

processknownassyneresis. Thisisoneofthe characteristic propertiesofagel.the

exudatesthatappearsonthesurfaceofthegelduringandaftersyneresisisnotpre water

asisshown bythe factthatitmay beeitheralkalineoraciddependinguponthe

compositionofthegelinanyeventwhenever waterorflidisremovedfromthemicelles

ofthegelbysyneresisorotherwiseashrinkageofthegeloccurs.

Ifagelislackingin watercontent,asorptionof waterwilloccurbyaprocessknownas

imbibitions,ifitisplacedin contactwith water. A swellingofthegeloccursduring

imbibitions, untiltheoriginalwatercontentisrestored.

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Getsappeartoexhibita memoryinthisrespect;ifa certainamountof wateris

removed fromagelofagiven concentration,imbibition willoccuronlytotheextentthat

thelostwaterisrestored. Theminimalconcentrationofthegelatagiventemperatureis,

therefore,establishedbythe concentrationofthesolbeforegelation. Thus,itfollowsthat

whenahydrocolloidimpressionmaterialgelsaroundtheteeth,thespecific watercontent

isthenestablishedforthatparticularimpressionathatspecific temperature. Irreversible

hydrocolloidsetby chemicalreactionandelastic innature.

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Irreversible Hydrocolloid

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RESEARCH

WORK

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CONTENTS

PAGE NO

1. INTRODUCTION 01

2. REVIEW OF LITERATURE 03

3. MATERIAL AND METHODS 11

4. RESULTS 17

5. DISCUSSION 39

6. SUMMARY AND CONCLUSION 42

7. BIBLIOGRAPHY 43

8. ANNEXURE 46

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LIST OF TABLES AND GRAPHS

Sl. No. TITLE Page No.

Chart 1 NAME OF THE MATERIALS USED AND NAME 15OF MANUFACTURER

Table I SHOWS MEASUREMENT OF FRASACO 16MASTER MODEL AND THEIR MEAN VALUES

Table- IIto V SHOWS MEAN VALUE AND STANDARD 17-20DEVIATION, MEAN VALUE DIFFRENCE OF

EACHBRAND OF MATERIAL FROM THEMASTER MODEL OF REFERENCES MARKING

A-B,B-C, AND D-A RESPECTIVELY

Table- VItoIX SHOWS MEAN VALUE AND STANDARD 21-24

DEVIATION, MEAN VALUE DIFFRENCE OFEACH GROUP FROM THE MASTER MODEL

OF REFERENCES MARKING A-B,B-C, ANDD-A RESPECTIVELY

GraphItoIV SHOW THE DISCREPANCIES OF EACH 25-28

BRAND OF MATERIAL FOR REEFRENCE

MARKING A-B,B-C, C-D AND D-ARESPECTIVELY FROM THE MASTER MODEL

Graph Vto VIII SHOW THE DISCREPANCIES OF EACH 29-32GROUP OF FOR REFERENCE MARKING A-B,B-C,

C-D AND D-A RESPECTIVELY FROM THEMASTER MODEL

GraphIX SHOW THE COMPARATIVE PERCENTAGE 33

DIFFERENCE OF ALL GROUPS FORREFRENCE MARKING A-B,B-C, C-D AND

D-A

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ILLUSTRATIONS

SL. NO. TITLE

Fig. 1 SCHEMATIC REPRESENTATION OF MASTERMODEL SHOWING THE REFERENCE POINTS

Photo 1 ALGINATES USED IN THE STUDY

Photo 2 IMPROVED ALGINATES USED IN THE STUDY

Photo 3 ELASTOMERS USED IN THE STUDY

Photo 4 OCCLUSAL VIEW OF FRASACO DENTULOUSMASTER MODEL

Photo 5 FARASACO MODEL MOUNTED ON THE PHANTOMHEAD

Photo 6 ARMAMENTARIUM USED IN THE STUDY

Photo 7 IMPRESSIONS MADE OF GROUP I AND IIMATERIALS

Photo 8 IMPRESSIONS MADE OF GROUP III MATERIALS

Photo 9 OCCLUSAL VIEW OF THE CAST

Photo 10 CASTS PRODUCED FROM DIFFERENTIMPRESSION

MATERIALS

Photo 11 CASTS ON THE STUDY TABLE OF THE PROFILEPROJECTOR MICROSCOPE

Photo 12 PROFILE PROJECTOR MICROSCOPE USED FOR THESTUDY

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Introduction

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Introduction

Partialedentulismisoneof the commonestprosthodontic pr oblems, we

comeacross.This conditionis usuallytreatedbymeansofremovable or

fixedprosthesis .

Since th e introductionof Alginatein the year 1947,itisone of th emost

commonly use dimpressionmaterialin recordingthe partialedentulous

conditions. Butthe studies havesho wn thatthe alginatesar eno t

dimensionallysta ble andaccurateen oughto be usedasanimpression

material for fixedpartialdenture cases.

Whe nit comesto it saccuracyan ddimensionalst ability,elastomersar e

proved to besuperiorthan thatth ealginatesan dtheyare the most

pr eferredimpressionmaterials in partialedentulous conditions. Fro mthe

last coupl eof years,toovercom eth ede ficie ncie sof alginates,various

companieshave com eout with the improvisedalginate ( Chromatic alginate)

whichthey claim to beeq uivalent to the elastomersand can be used in cro wn

an d bridge cases.

Since they claimthatimprovisedalginatesare equivalentin qualityand

dimensionalacc uracyas comparedtoelastomer,thisstudy has been

planned with th e followin g aimsan dobjectives:-

\

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Introduction

Aims and Objectives:

1. To comparethedimensional accuracyofalginates withthatofimprovedalginates.

2. To comparethedimensionalaccuracyofalginates withthatofelastomers.3. To comparethedimensionalaccuracyofimprovedalginates withthatof

elastomers.

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Review of literature

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Review of Literature

BAILEY (1955)recommendedacrylic resin tray forrubber base

impression materials . He specified that this traysh ouldhavea spacerof

1 to 1.5 mmover the abutment teeth. Theocclusaland incisalsurfacesof

unprepared teethsh ouldno t be covered by thespace rso that they actas

stops fo r the tray . Perforations shou ld bemade to providemechanical

retention for the impression material. He believed thatan individualtray

preparedin this manner wou ld utilize t he utmostelasticityo f rubber

based impression materials .

ROSENTIEL (1955) carriedoutan investigation on thedimensional

accuracy with modelsobtained fr omrubber bas e impression materialof

a stainless steel diesimulating two bridge abutment . A copperplated

replica was obtained. Controlexperiments withother impression

materials sh owed it to compare favourably with th e more reliab leof the

oldermaterials . Reversibl ehydrocolloids gave the least satisfactory

result.

EUGENE W.SKINNER and NOEL E.HOBLIT (1956)studied the

accuracy of hydrocolloid impressionsa nd for this, they construc tedan

oversize model to simulate the conditions like the human m outh fora

one tooth bridge . Impressions in hydrocolloid were ob tainedof the

modeland theirdimensions were compared wit h thesimilardimensions

of themodel . In thisstudy the threereversible hydrocolloids impression

materials an d impression involving both typesof materials wer e

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consideredan d from this study theystated that th e impressions obtained

wi th the irreversibl ehydrocolloidmaterialare equal in accuracy to those

obtained with reversiblehydrocolloidmaterials .

CAUL H.J. (1957)out l ined the techniques that wouldavoidmany of

the inaccurac ies in th e use of alginate impression materials .

Caulsuggested that:

1)Alginatemixsh ouldhavea smooth creamy consisten cy .2)Pr ecooling the mixingequipment and using coo l water is indicated to

delay thesetting time. Since, this is a chemica lreaction the working

time wil l be lengthened by reduction of temperatureof t hemix.

3) Impression s hould be removed with a sudden an dsnap about 2-3minutes after time of set.

4) Impression s hould be pour ed instantaneo usly.5) Impression and casts houl d be separatedone hourafterpouring.6)Excellentaccuracy can beobtained with alginates if th ematerial is

usedproperly .

PHILLIPS (1958)summarized th e research on elastomeri c materials

andstarted that factorssuch as the us e of minimum bulkof materials,

bondingof the impression material to t he tray, adequate time in the

mouth and use of doublem ix technique wereessential foraccuracy.

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SNIPPER (1960)studied invivo theaccur acy of castingmade wi th

Thiokoland Sil icon eand comparison d rawn wa s that Thiokols, wh en

manipu latedassuggested, wi llproduce impressions of complete dental

archasan yotherelasti c impression material .

AGARWAL N.K. et al (1970) carriedouta study todeterminethe

accurate reproduc ibility of alginate impression materials . They tested

three brandsof alginate under the tradenameof Zelgan, Unidentan d

Dencerand with thesealginates theymade the impression of brassmetal

die with a perforated copper cap witha uniforms paceof 1.5 mm. Their

conclusion wa s that Zelgan Alginate material wasmore accurate than

others, if poured within 3 t o 10 minu tes .

JAMES A.STACKHOUSE Jr. (1975)con ductedastudyo na

comparison o f elastic impression materials in relation to consistency and

timerelation a ndhe concluded that, th e polyethermaterial compared

favorably with the other in mixing t ime, working t ime,and consistency.

1) There wer e no signi ficantdif ferences in accuracyamongallof th e Elastomers when pour ed within 30 minutes.

2)Diespoured immediately fr om thehydrocolloids didnotdiffersignificantly fro m thoseo f the othermaterials poured in 30 mi nutes.

3)The polyether wa s the moststableamongall the testedmaterials .5

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HOSES F.SAWYER et al (1976)conducteda stud yon theaccuracy

of castsproduced fro m two alginate hydrocolloids ( irreversib le) , one

hydrocolloid (reversib le) an dapolyetherrubber. When compared ,

they conc luded that th epolyetherimpression materialproduced the

mostaccurate casts. Thehydrocolloidsreversible casts we re the

secondmostaccurate,andthealginate ( irreversi blehydrocolloid)

produced the least accurate casts.

JEAN PIERR STAUFFER et al (1979)studied the accuracyof six

elastic impression materials used for complete arch fixedpartial

dentur esand fo r this, four types of impressionmaterials were used.

The accuracy wasevaluated by visua l comparison an d indirect

measurement methods and from this study they conclud ed that:

1)None of the testedmaterials allow sa fe finishingof a complete arch fixedpartial dentureon a castpoured fromone single

masterimpression .

2)Allof the testedmaterials can be used for impressions fora complete arch fixedpartial denture.

EAMES W.B et al (1979) studied theeffecto f bulkon theaccuracy

of elastomeri c impression materials Impression trays were fabricated

providing 2 , 4 and 6 mms pacer to determine the stability an daccuracyof

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nineelastomeri c impression materials on a simulated fu ll cro wn

Apreparation steel dieand from this study theystatedthat space of 2 mm

produced themost accurate impressions forallof th ematerials tested.

EAMS W.B et al (1979)studiedaccuracyanddimensionalstability

of elastomeri c impression materials in relation to makingof impression i n

a heatprocessedtray, with aspaceo f 2.4mm for impression material and

from the s tudy theystated that the impressionsshou ld be pouredassoonas

possib le . When pouredimmediately,manyof theavailab le materials

exhibi tsimilar characteristicsof s tabi l i ty.

OLA HANSSON and JAN EKLUND (1984) studied thedimensional

accuracy of threenew alginate with that of two agarhydrocolloidsandone

additionalsilico ne in relation to different stock traysa ndstated thatn ew

alginates we reasaccurate asother impressionmaterials in most clinical

conditionsa nd furtherstated that the use of perforatedandnon-

perforated

metalstock tray will cause inaccur acy. However when use din severe

undercutarea theystatedthatalginate were inferior to elastomers in

accuracy .

CHANG CHI LIN et al (1988) conducteda study o n the accuracyo f

Impression materials . Thematerials selected fors tudy were polyether,

vinylpolysiloxane, polysu lfide,reversiblehydrocolloids, irreversible

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hydrocolloidand irreversible reversible hydrocolloid comb ination . They

concluded thatthepolyethergave themostaccurater esul t, thesecon d

accurate wasvinyl polysiloxanes followed bypolysulfidesand irreversible

reversible hydrocolloidsand least accurate was irreversib lehydrocolloids.

P.A.ODMAN, T.M JENT (1988)conduct eda stud yon the accuracy

of impression materials in a semi-c linicalmodel . The materials selected

for thisstudy were irreversible hydrocolloid,reversiblehydrocolloidand

addition and condensationsilicone and theystated thatalltestedmaterials

seemedacceptable fo r clinical us e in crown andshort span bridge work.

GEORGIA S.DOVNIS et al (1991)conduc teda study to compare the

Marginal fitof complete arch fixedprosthesis unders imulated clinical

conditions. Prostheses wer e madeon casts construc ted fr om three

commonly used impression materials; Polyther, Polyvinylsiloxane

(Mediumviscosity a ndputty wash) and Reversiblehydrocolloids . A

maxillary dentofo rm with fourabutment teeth was usedas th emaster cast

andsix impressions was made with each material. Individual casting for

each abu tment wa smade on the stone casts. The abutment castings were

luted togetheron the ca st to provide a complete arch fixedpartial denture

usinga tic tonium framewo rkandacrylic resin . The marginal fitof the

abutment casting wasmeasuredon t hemaster cast before andaftert he

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prostheses we re luted togetherand theystatedthat the polyetherand both

addition and condensationsilicone impressionmaterials were significantly

more accurate than the reversible hydrocolloid in both situations. Allof

thesingle castings were clinically acceptable, but the lute drestorations

made fro mreversible hydrocolloids were not.

ANDERS ERIKSSON et al (1996) studiedirreversibl ehydrocolloids

used for cr own an d bridge impressions andstated thatall the irreversible

hydrocolloids,hydrocolloids if correctl y treated befor epouring with

compatiblegypsum, couldreproduce detailsof 20 m mand furtherstated

thatdetail reproductiond idnotimprove wi th the use of 2% potassi um

sulfat esolution, compared to wateror if the impression wer epoured

dry . In general, the alginate stabi l izerproduced casts wit h significantly

Betterdetail reproduction andsurface structure and theyalsostatedthat

an irreversi b le hydrocolloids impression shouldn ot come into contact wi th

any liqu id within the first 15 minutes.

KENNETH J.ANUSAVICE (1999)stated thatthemost of th e alginate

impression materials ar e not cap ableo f reproducing the finerdetails that

oneobserved wi th elastomeri c impressionmaterials . To improve the

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accuracy of the alginates, the surfactants can be us ed butaddition of a

layerof so lution over thesurface of th e impression also obscures the

accuracy .

JOSEPH NISSAN et al (2000) studied the accur acyof threeput ty

wa sh impression techniques usingthepolyvinyl siloxane impression

materialand they conc luded that th epolyvinyl silxane, 2 step, 2 mmrelief

putty wa sh impression technique was the mostaccurate for fabr icating

stonedies.

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Materials and Methods

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I. ARMAMENTARIUM USED IN THE STUDY

Frasaco dentulousmodel

Maxillary metallic dentu lous p erforatedstock tray(Coe Tray) Waterdispensing cup Alginatedispensingsco op Rubber bowl Curvedstainless steel mixingspatula Straightstainless steelmixingspatu la Automixinggun forelastomers Base former Vibrator Pr ofile Projector Microscope

II. MATERIALS USED IN THE STUDYForthiss tudy, the materials used were groupedas follows;

1. Group I: A lginate a . Zelgan ( Dentsply India)b. Alginoplast ( Heraeusand Kulzer Holland)

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2. Group II: Improvedalginate a . Litochrom (LASCOD Italy)b. Cavex (Cavex Holland 3. Group III: Elastomera . Pu tty consistency elastomer (3M, India, Reprosil, India)b. Light body elastomer (3M, India, Reprosil, India)

4. Tray adhesive (3M, Reprosil, India)

5. Diestone Type IV (Kalabahi, Karson, Mumba i)

6. Dentalplaster Type II (Kalabahi, Karson, Mumbai)Thepresent in-vitrostudy was carriedout in the Departmento f

Prosthodonti cs, Bapuji Dental Collegeand Hospital, Davangere.

Material andmethod followed in this study has been discussed under

the following headings.

1. Preaprationof themastermodel (Frasaco Model )2. Selection of th e stock tray foralginates andelastomer.3. Making impressionsof the mastermodel usingalginates, improved

alginates an delastomers .

4. Pouring the cas t5. Measurement of thedistance betwe en r eference points

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Materials and Methods1)Preapration of Master Model

The Frasaco maxillary dentulous model was selectedandr eference

markings of 1 mm in diameter wer emadeon the buccal cus p of first

pre-molars a ndmesio-buccal cusp of the first molar usinground

diamond bur. Thesemakings weremade on 14 , 24 , 26 & 16and wer e

namedas A, B, C, & D respec tively . Th edistance betwe en the above

markings wer e measured wi th a profile projector microscopean dkept

asa standardvalue.

2)Selection of the stock tray ;The maxillary perforatedstocktray (Coe tray) wa sselected wi th a

unifor mspaceof 4-6mm between the tray and the mastermodel to

make impression wit h alginate improvedalginate andelastomer.

3)Making impression of the master model using various impressionmaterials.

The Frasaco model wasm ountedon the phantomheadan d using

each group, 14 impressions wer emade.

Making Alginate Impression:

Manufacturers instruc tions werestrictly followedregarding the water:

Powde rration and themanipulation of Alginates Uniformly mixed

irreversibl ehydrocolloids we remade, loadedonto the selecte dperforated

stock tray and th e impressions were madeof themastermodel mountedon

thephantom. after 5 minut es (3 minutessetting time + 2 minutes waiting

time) ,

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impressions were removed from th e mastermodel and checked for the

accuracy,seven impressions weremade usingeach branda nda totalof 14

impressions were ob tained. Acceptable impression we repoured wi thdie

stone Type IV.

Making Improved Alginate Impression:

Similar to the Alginate impressions, 14 impressions of group II wer e

made, 7 of each brand we reobtainedandpoure d with die stone, Type IV.

Making Elastomeric Impression:

On theselectedst ocktray, the respective trayadhesive wa sappliedonto

the tissue surface and 2 m mat the borderof the stock tray. Then the tray

wa sairdrieda theroom temperat ure for 10 minu tes.

Putty consistency baseand catalyst we re takenaccording to

manufacturers instruc tionan dmixed till the unifo rm colour wa sobtained

andloadedonto t heselectedstock tray andon this th epolyethylene sheet

wa sappliedasa sp acerand impression was made . Aft er

this thepolyethylenesheet wa sremovedand light body was loadedonto

theputty usingautomixinggun and tray was again seatedonto the model

andimpression wasmade,similary 14 impressions were made,sevenof

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each brandand were checked fo rpresence of voids andacceptable

impressions were poured wi th diestone Type IV.

4)Pouring of the Cast:The die stone, Type IV was handmixed. Waterpowderratio wa s taken

according to ma nufaturers instruc tions in a clean rubber bowl. With the

help of straightstainless steel spat ul a it was uniformaly mixedandpoured

into the impression on themechanicalvibrator. Aftersetting, the casts

wereremoved fr om the impressionsandthe base wasp oured withdental

plaster Type II.

5)Measurement of the Dimensaional Accuracy:Measurements wer e made between th e fourreefrence points thatar e A to

B,B to C, C to D and D to A using NikonProfile Projector Microscope,

Japan atBapuji Institutse of Engineering and Technology, Davangere.

The readings were obtainedandsub jec ted tostatisticalanalysis .

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CHART 1

MaterialandGroup

Trade Name Manufactur er

Group I

Alginate

Zelgan Dentsply India Ltd.

Alginoplast Heraeus Kulzer,Italy

Group II

Improved Alginate

Cavex Cavex, Holland

Litochrom LASCOD , italy

Group III

Elastomeri c

3 M 3M, India

Reprosil Dentsply, India L td.

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Photographs

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Results

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RESULTS

TABLE I

1 2 3 Mean Value (mm)

A - B 42.645 42.645 42.645 42.645

B - C 12.801 12.801 12.801 12.801.

C - D 51.890 51.890 51.890 51.890

D - A 12.770 12.770 12.770 12.770

Showsthemeanvalueofreferencespointsonthemastermodelinmillimetersand

micrometers.

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Results

TABLE - 2

SHOWS THE MEAN AND STANDARD DEVIATION, DIFFRENCE ANDPERCENTAGE DIFFRENCE OF ALL MATERIALS FROM THE, MASTER

MODEL FOR REFERENCE MARKING A-B

One way ANOVA (F = 802.3)

Student- Newman KaulstestP

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Results

TABLE - 3

SHOWS THE MEAN AND STANDARD DEVIATION, DIFFERENCE ANDPERCENTAGE DIFFERENCE OF ALL MATERIALS FROM THE, MASTER

MODEL FOR REFERENCE MARKING B-C



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Results

TABLE - 4

SHOWS THE MEAN AND STANDARD DEVIATION, DIEFFRENCE ANDPERCENTAGE DIFFERENCE OF ALL MATERIALS FROM THE, MASTER

MODEL FOR REFERENCE MARKING C-D



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Results

TABLE - 5

SHOWS THE MEAN AND STANDARD DEVIATION, DIFFERENCE ANDPERCENTAGE DIFFERENCE OF ALL MATERIALS FROM THE, MASTER

MODEL FOR REFERENCE MARKING D-A



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Results

TABLE 6

SHOWS THE MEAN AND STANDARD DEVIATION, DIFFERENCE AND

PERCENTAGE DIFFERENCE AND PERCENTAGE DIFFERNCE FOR ALL THE

GROUPS FOR REFERENCE MARKINGS A-B

Impressiion

Material

DimensionalMeasurements (mm)

MasterModel Mean + S.D. Difference from

MasterModel

Percentage

Diffrence

-MasterModel

42.645 -

GroupIAlginate41.283+0.052 1.362+0.052 3.2%

GroupIIImproved

Alginate 42.032+0.067 0.613+0.067 1.4%

GroupIII

Elastomer 42.578+0.038 0.067+0.038 0.2%



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Results

TABLE 7

SHOWS THE MEAN AND STANDARD DEVIATION, DIFERENCE AND

PERCENTAGE DIFFERENCE FOR ALL THE GROUPS FOR REFERENCE

MARKINGS B-C

Impressiion

Material



MasterModel

PercentageDiffrence

MasterModel12.801 - -

GroupIAlginate12.569+0..46 0.232+0.046 1.8%

GroupIIImproved

Alginate 12.575+0.036 0.226+0.36 1.7

GroupIII

Elastomer 12.767+0.017 0.034+0.017 0.3%



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Results

TABLE 8

SHOWS MEAN AND STANDARD DEVIATION, DIFFERENCE AND


MARKINGS C-D

Impressiion

Material



MasterModel

PercentageDiffrence

MasterModel

51.890 - -

GroupIAlginate

50.673+0.041 1.217+0.041 2.4%

GroupIIImproved

Alginate 51.337+0.019 0.513+0.019 1.0%

GroupIII

Elastomer 51779+0.006 0.111+0.006 0.2%



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Results

TABLE 9

SHOWS MEAN AND STANDARD DEVIATION, DIFFERENCE AND


MARKINGS D-A

Impression

Material



MasterModel

PercentageDifference

MasterModel

12.770 - -

GroupIAlginate

12.303+0.042 0.467+0.042 3.7%

GroupIIImproved

Alginate 12.466+0.053 0.304+0.053 2.4%

GroupIII

Elastomer 12.694+0.005 0.076+0.005 0.6%



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GRAPHS

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RESULTS

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Results

The ai mof the presentstudyis to assess an d compare th edimensional

accuracyof alginatessan dimprovedalginates with thatof elastomer

mpressions

Material.

The material withtheirtradenamean dnameof theirmanufacturers

have beensho wnin Chart No.1.

The distance betweenthereference markings weremeasuredto kno w

th eacc ura cyof di fferencematerialsand compared withth emastermodel

values . For thisth etestsp ecimens (Casts) wereevaluated underProfile

Projector Microscopeamdthe accura cyof eachsp ecimen wasanalysed

Statistically by;

1) Wilcoxons signed rank test :it was usedto compareth eaccuracyofdi fferentmaterials with th emastermodel.

2) One way ANOVA test :inthistest,th emeandi screpancyof di fferentmaterials were sub jecte d.

3) Student-Newman Kauls test ;it was used forthe simultaneouscomparison betwee ndi fferentgro ups .

TABLES:

Table I:

Itsh ows th emeasurementsof the mastermodelan dtheirmeanvaluein

millimeter (mm ) an dmi crometer (u m).

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Results

Table II:

Itsho wsthe meanvaluean dstandarddeviation,meanvaluedi fference

an dthe pe rcentagedifferenceof each brand fro mth emaster-model for

reference marking A-B.

Table III:

Itsho wsthe meanvaluean dstandarddeviation,meansvaluedifference

an dthe pe rcentagesdi fferenceof each brand from themastermodel for

referencemarkingB-C.

Table IV:

Itsho wsthe meanva luean dstanderddeviation,meanvaluedi fference,

Andthe pe rcentagedifferenceof each brand fromth emastermodel for

referencesmarking C- D.

Table V:

Itsho wstemeanvalueandstanderddeviation,mean,valuedi fference

f

an dthe pe rcentagedifferenceof each brand fro mth emastermodel for

referencemarking D-A.

The ANOVAtest sh owedthat th ematerialsof Gro upI, GroupIIand

GroupIIIexhibitsignificantlydi fferentdimensional changes fromth e

master model. GroupII Ish ows th e leastdimensionalchange followed by

GroupIIan dth ehighestdimensionalchange wassh own by GroupI from the

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Results

mastermodel foral lre ferencemarkings. The F va lueof ANOVA test was

significan t foral lre ferencemarkingsinal lgroups. So, toknow whichgro up

di fferssignificantly from one an d th eother,Student- New Kauls testwas

used.

The Pvalueof Student Newman Kaultest wassignificant betweenth e

gr oups (P.01) withinthe gro ups ,

so

th evalueof ea chgro uphas bee n clubbedan d compared with the

master-mode.

Table VI, VII, VIII, and IXsh ows th emeanvaluean dstandard

deviation,meanvaluedi fferencean dth epe rcentagedi fferenceof eachgr oup

fro mth emastermodel forthe referencemarkings A- B, B-C, C-D an d D- A

respectively.

Whe nth emeanandstandarddeviation,meanva luedifferenceand

pe rcentagedifferenceof eachgr oup were compared with the master-model

an dstaticallyanalysed, Itsh owedth e followedmentionedpe rcentage

di screpancies.

Percentagediscrepancies of ea chgro up fro mth emastermodel:

A- B B-C C-D D-A

Gro oupI 3.2% 1.8% 2.4% 3.7%

Gro oupI 1.4% 1.7% 1.0% 2.4%

Gro oupI 0.2% 0.3% 0.2% 0.6%

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Results

So, fro mthesevalues it can berevealedthatth e GroupII I

elastomerssho wed least discrepancies fro m th emastermodel followed by

Group II

improvedalginatesan dth ehighestdi screpancies wasseenin GroupI

alginate .

Graph I, II, III and IVshows th e di screpanciesof eachgroup for

referencemarkings A-B,B-C, C- D,an d D-A respectively forth emaster

model.

Graph V, VI, VII and VIIIshowsth edi screpancie sof eachgr oup for

referencemarkings A-B,B-C, C- D,an d D-A respectively forth emaster

model.

Graph IXshows th e comparativepe rcentagedi fferenceof allgr oups

forreferencemarkings A- B,B-C, C- D,an d D-A respectively forthe master

model.

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Discussion

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Discussion

Forthe [properfittingofallthepartialprosthesis,theaccuracyofimpression

materialsplayanimportantrole. Fromthe beginningof 18th

and19th

centuries,many

researchesaregoingontoimprovetheaccuracyoftheimpressionmaterials.

In 1937,Sears usedagarhydrocolloidasanimpressionmaterialforthe firsttime.

In 1947,theirreversiblehydrocolloids cameintoexistence.

TheadvantagesofalginatediscussedbySkinner and Pomes were;

I. Low costII. Noheatinnecessary fortheirpreparationandnodangerof burningofmouth

of the patient.

III. Sufficientfluiditypriortothetimegelation.IV. Reducedriskoftrappingofair.

Caul H.J. outlinedthetechniquestoavoidtheinaccuraciesduringthe useof

alginateimpressionmaterial.

i) Alginatemixshouldhaveasmooth creamy consistency.ii) Pre coolingofthemixingequipmentandusingcoolwaterindicatetodelaythe

settingtime. Sincethisisthe chemicalreaction,the workingislengthenedby

reducingthetemperatureofthemix.

iii)Theimpressionshouldberemoved withsuddenandsnapabout2-3 minutesafterthetimeofset.

iv)Theimpressionshouldbepouredinstantaneously.v) Theimpressionshouldbeseparated1 hourafterpouring.

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Discussion

Agarwal er alsuggestedthataccuracyofthealginateimpressionmaterialis betterif

pouredwithin 3-10 minutes. SkinnerandCarlismprovedthatconsiderableerrorsinthe

accuracyofalginateoccurredwhen;

i) Thealginateimpression wasdriedwithanair-burst.ii) Themodelsurface wasdriedbeforetheimpression wastaken.iii)The wateratroomtemperature wasemployedinsteadofice water.

Chang-Chi-Lin et atprovedthatirreversiblehydrocolloidwasleastaccurate when

comparedwithothermaterials.

Toovercometheadvantagesofthealginate,inthepastrecentyearsseveralnew

materials formixedprosthesis basedonalginatehave beenintroduced. Asthenew

hydrocolloidsareonlyminormodifications oftheolderonesandthemanipulationis

almostsameasin 1947.

Ander et. Al. conductedastudyontheaccuracyofnew alginates and the

traditional

alginates. Accordingtothemnew alginatesare 2-3 time costlythantraditionalalginates

and they

statedthatthisstudydoesnotindicatethattheincreaseprize correspondstoasimilar

increaseinthesuccessofimpression,

Anne Pertzfeldt et alprovedfromtheirstudythattheaccuracyofthe blueprint

alginates was comparable withtheelastomers.

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Discussion

Fromtheresultsobtainedofthepresentstudy,ithas beenprovedthatthereis

significantdifferenceonthedimensionalaccuracy betweenthealginatesandthe

improvedalginates.

In 1975,theadditionalpolymerizingsilicones wereintroducedinthemarket.

There wasno by-productofthepolymerizingreactionandthematerialprovedto bemore

dimensionallystableandaccurate.

Ithas beenprovedbySawyer, Peutzfeldt, Chang-ChillinandAnusavicesthat

elastomersaremoreaccuratethenalginates.

B.A.Linke et alprovedfromtheirstudyonthedistortionanalysisof stone

castmade fromdifferentimpressionmaterialsandthey concludedthatsilicone

impression materialsproducedlessinter-abutmentdistortionthantheirreversible

hydrocolloidsandtheyalsostatedthatstatically significantdifferencesexistamongthe

differentimpressionmaterials.

Fromthepresentstudyitisprovedthatthesignificantdifferencesexists between

theelastomers,alginatesandimprovedalginatesontheaccuracyof impression.

Theresultofthisinvitrostudyshowedthatimprovedalginatesare betterthan

alginates buttheelastomersarethestillmoreaccurate. Sothe furtherstudiesare

requiredto co- relatetheresults clinically.

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Summary and Conclusion

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Summary and Conclusion

Thepresentstudy was con ducte dto compareth edimensional

accuracyof alginatesan d improvedalginates with thatof elastomers.

Forthisstudy , Frasacomodel was prepared with fourreference

markingsan dsevenimpressions weremade,totally 42 casts wereprepared

usingdifferent impressionmaterialsan dth edistance betweenth ere ference

markings A-B,B-C, C-D,and D-A on the casts were measuredan d compared

withth edistance between th ereferencemarkingson the mastermodel.

Mu lt igroup comparisonof referencemarkings wereanalysed by

One- Way ANOVA F-testfollowed byStudent-Newman Kauls test.

For mthisstudy is was concludedthat;

1) Improvedalginates were moredimensionallyaccu ratethanalginates.2) Elastomers weremoredimensionallyaccuratethanalginatesas wellas

fro mth eimprovedalginates.

3) Although elastomers weredimensionallymoreaccuratethanthe improvedalginates, bu tth edi screpancy was lessas comparedto

alginates.

4) Further clinicalstudyis req uired to comparean dassessthe accura cyofimprovedalginates with thatof th eelastomers.

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Bibliography

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Bibliography

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Annexure

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Annexure

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