this presentation includes various impression materials used in our dental practice

1. PRESENTED BY
DR MEENAL ATHARKAR
MDS
DEPT OF ENDODONTICS
AND CONSERVATIVE
DENTISTRY

2.  INTRODUCTIONINTRODUCTION
 DEFINITIONDEFINITION::
 HEARTWELLHEARTWELL ((19921992))
 MM..MM DEVANDEVAN ((19951995))
 HISTORYHISTORY
 IDEALIDEAL REQUIREMENTSREQUIREMENTS –– ACCURATEACCURATE IMPRESSIONIMPRESSION::
CLASSIFICATIONCLASSIFICATION
CONTENTS
 CLASSIFICATIONCLASSIFICATION
 HYDROCOLLOIDSHYDROCOLLOIDS::
 AGAR (REVERSIBLE HYDROCOLLOIDS)AGAR (REVERSIBLE HYDROCOLLOIDS)
 ALGINATE (IRREVERSIBLE HYDROCOLLOID)ALGINATE (IRREVERSIBLE HYDROCOLLOID)
 LAMINATE TECHNIQUELAMINATE TECHNIQUE
 SHELF LIFESHELF LIFE
 EFFECTS OF MISHANDLING HYDROCOLLOIDSEFFECTS OF MISHANDLING HYDROCOLLOIDS

3.  NONNON--AQUEOUS ELASTOMERIC IMPRESSION MATERIALS:AQUEOUS ELASTOMERIC IMPRESSION MATERIALS:
 CLASSIFICATIONCLASSIFICATION
 COMPOSITION, SETTING REACTION, ADVANTAGES &COMPOSITION, SETTING REACTION, ADVANTAGES &
DISADVANTAGESDISADVANTAGES
 POLYSULFIDEPOLYSULFIDE
 CONDENSATION SILICONECONDENSATION SILICONE
 ADDITION SILICONEADDITION SILICONE
 POLYETHERPOLYETHER
 POLYETHER URETHANE DIMETHACRYLATEPOLYETHER URETHANE DIMETHACRYLATE
NEWER FORMULATIONSNEWER FORMULATIONS NEWER FORMULATIONSNEWER FORMULATIONS
 MANIPULATIONMANIPULATION
 PROPERTIESPROPERTIES
 INELASTIC IMPRESSION MATERIALS:INELASTIC IMPRESSION MATERIALS:
 IMPRESSION PLASTER (TYPE I)IMPRESSION PLASTER (TYPE I)
 IMPRESSION COMPOUNDIMPRESSION COMPOUND
 ZINCZINC--OXIDE EUGENOL IMPRESSION PASTEOXIDE EUGENOL IMPRESSION PASTE

4.  TRAYS:TRAYS:
 STOCK TRAYSSTOCK TRAYS
 PLASTIC TRAYSPLASTIC TRAYS
 DUAL ARCH TRAYSDUAL ARCH TRAYS
 METAL TRAYSMETAL TRAYS
 RIMRIM--LOCK TRAYSLOCK TRAYS
 CLEAR TRAYSCLEAR TRAYS
 CUSTOM TRAYSCUSTOM TRAYS
 TRAY ADHESIVESTRAY ADHESIVES
 GINGIVAL DISPLACEMENT:GINGIVAL DISPLACEMENT:
 INTRODUCTIONINTRODUCTION
 BIOLOGIC WIDTHBIOLOGIC WIDTH
 IMPORTANCEIMPORTANCE
 VIOLATIONVIOLATION
 TECHNIQUETECHNIQUE

5.  CHEMOCHEMO--MECHANICAL METHODSMECHANICAL METHODS
 SINGLE CORDSINGLE CORD
 DOUBLE CORDDOUBLE CORD
 INFUSION METHODINFUSION METHOD
 SURGICAL METHODSSURGICAL METHODS
 ROTARY CURRETAGEROTARY CURRETAGE
 ELECTROSURGERYELECTROSURGERY
 IMPRESSION TECHNIQUES:IMPRESSION TECHNIQUES:
 DOUBLE MIXDOUBLE MIX DOUBLE MIXDOUBLE MIX
 SINGLE MIXSINGLE MIX
 PUTTY/WASHPUTTY/WASH
 SIMULTANEOUSSIMULTANEOUS
 RELIEF CHANNELRELIEF CHANNEL
 2MM SPACER2MM SPACER

6.  COPPER BAND TECHNIQUECOPPER BAND TECHNIQUE
 DUAL ARCH IMPRESSION TECHNIQUEDUAL ARCH IMPRESSION TECHNIQUE
 SEGMENTAL IMPRESSION TECHNIQUESEGMENTAL IMPRESSION TECHNIQUE
 TOOTH/IMPLANT IMPRESSIONSTOOTH/IMPLANT IMPRESSIONS
 INDIRECT DOWEL, CORESINDIRECT DOWEL, CORES
 PINPIN--RETAINED RESTORATIONSRETAINED RESTORATIONS
 DISINFECTION OF IMPRESSIONSDISINFECTION OF IMPRESSIONS
 CONCEPTS OF TRANSPORTATION TO THE LABORATORYCONCEPTS OF TRANSPORTATION TO THE LABORATORY
 SUMMARY & CONCLUSIONSUMMARY & CONCLUSION
 REFERENCESREFERENCES

7. AnAn impressionimpression isis anan imprintimprint oror negativenegative likenesslikeness.. AA
goodgood impressionimpression isis invaluableinvaluable inin thethe fabricationfabrication ofof aa
functionallyfunctionally andand estheticallyesthetically pleasingpleasing prosthesisprosthesis..
INTRODUCTION
functionallyfunctionally andand estheticallyesthetically pleasingpleasing prosthesisprosthesis..
TheThe indirectindirect techniquetechnique forfor fabricatingfabricating inlays,inlays,
crowns,crowns, fixedfixed partialpartial denturedenture hashas beenbeen aa boonboon toto
thethe practicepractice ofof dentistrydentistry..

8. The materials currently available, easily fulfill all the
requirements that the practitioner may place on his
impression material.
However, the fact that these requirements are metHowever, the fact that these requirements are met
collectively and not by any single impression
material is the rub and is the reason why the dentist
must be knowledgeable about the properties of
impression materials and impression techniques.

9. DEFINITIONDEFINITION
 AnAn impressionimpression isis anan “imprint”“imprint” oror negativenegative likenesslikeness ofof thethe
teethteeth and/orand/or edentulousedentulous areas,areas, mademade inin plasticplastic materialmaterial
whichwhich becomesbecomes hardenedhardened oror setset whilewhile inin contactcontact withwith thethe
tissuetissue..tissuetissue..
--HeartwellHeartwell

10.  PhilipPhilip PfaffPfaff--17561756
 FirstFirst describeddescribed takingtaking impressionimpression withwith softenedsoftened waxwax
 ChristopheChristophe FrancoisFrancois DelabarreDelabarre--18201820
 IntroducedIntroduced thethe metalmetal impressionimpression traytray
HISTORY
 IntroducedIntroduced thethe metalmetal impressionimpression traytray
 ChapinChapin HarisHaris--18531853
 FirstFirst usedused PlasterPlaster ofof ParisParis forfor makingmaking impressionsimpressions..
 CharlesCharles StentStent--18571857
 IntroducedIntroduced thethe firstfirst impressionimpression compoundcompound

11.  SearsSears--19371937
 FirstFirst usedused agaragar hydrocolloidshydrocolloids forfor recordingrecording crowncrown
impressionsimpressions..
 UnitedUnited StatesStates--19451945
 IntroducedIntroduced alginatealginate duringduring WorldWorld WarWar IIII..
SLSL PearsonPearson--19551955 SLSL PearsonPearson--19551955
 DevelopedDeveloped syntheticsynthetic rubberrubber basebase impressionimpression materialsmaterials

12.  PolysulfidePolysulfide-- LateLate 19501950’S’S
 FirstFirst developeddeveloped asas anan industrialindustrial sealantsealant..
 CondensationCondensation SiliconeSilicone-- EarlyEarly 19601960’s’s
 AdditionAddition SiliconeSilicone--19701970’s’s
 PolyetherPolyether-- LateLate 19701970’s’s
 PolyetherPolyether UrethaneUrethane DimethacrylateDimethacrylate -- LateLate 19801980’s’s

13.  FluidFluid enoughenough toto adaptadapt toto thethe oraloral tissuestissues
 ViscousViscous enoughenough toto bebe containedcontained inin thethe traytray
 SettingSetting timetime –– setset intointo rubberyrubbery /rigid/rigid solidsolid inin reasonablereasonable
amountamount ofof timetime..
IDEAL REQUIREMENTS TO OBTAIN AN ACCURATE
IMPRESSION
amountamount ofof timetime..
 AdequateAdequate teartear resistanceresistance
 DimensionallyDimensionally stablestable
 BiocompatibleBiocompatible
 ProcessingProcessing equipmentequipment-- CostCost effectiveeffective

14. II.. BasedBased onon thethe degreedegree ofof tissuetissue compressioncompression
 MucostaticMucostatic
ExEx:: ImpressionImpression plasterplaster
ZOEZOE impressionimpression pastepaste
CLASSIFICATION
ZOEZOE impressionimpression pastepaste
 MucocompressiveMucocompressive
ExEx:: ElastomersElastomers

15. II. By setting mechanismII. By setting mechanism
A. Chemical
reaction
(irreversible)
By elasticity and use
Inelastic or rigid Elastic
Materials Use Material Use
1.Plaster of
Paris
Edentulous
ridge
1. Alginate
2. Non-aqueous
Teeth
and softParis
2.Zinc-oxide
eugenol
ridge
Interocclusal
records
2. Non-aqueous
elastomers
-Polysulfide
- Polyether
- Condensation silicone
- Addition silicone
and soft
tissue
B. Physical reaction
(reversible)
3.Impression
Compound
Preliminary
impression
3.Agar hydrocolloid Teeth
and soft
tissue

16. III. Based on the chemical compositionIII. Based on the chemical composition

17. HYDROCOLLOIDSHYDROCOLLOIDS
ColloidsColloids –– AA systemsystem consistingconsisting ofof aa poorlypoorly solvatedsolvated phasephase
inin aa mediummedium..
-- TwoTwo phasesphases
DispersedDispersed –– AA particleparticle inin solutionsolution
DispersionDispersion phasesphases-- AA solutionsolution contaningcontaning suspensionsuspension ofof
particlesparticles..

18.  TheThe colloidcolloid cancan existexist inin thethe formform ofof aa viscousviscous liquid,liquid,
knownknown asas aa solsol oror aa solid,solid, describeddescribed asas aa gelgel.. ifif thethe
particlesparticles areare suspendedsuspended inin water,water, thenthen thethe suspensionsuspension isis
calledcalled aa hydrocolloid,hydrocolloid, withwith thethe liquidliquid beingbeing aa hydrosolhydrosol
andand thethe solidsolid aa hydrogelhydrogel..andand thethe solidsolid aa hydrogelhydrogel..

19.  AllAll colloidalcolloidal dispersionsdispersions areare termedtermed solssols ..
 InIn thethe gelgel state,state, thethe disperseddispersed phasephase agglomerates,agglomerates,
formingforming chainschains oror fibrilsfibrils calledcalled micellesmicelles.. TheThe fibrilsfibrils
maymay branchbranch andand intermeshintermesh toto formform aa brushbrush--heapheap
structurestructure..
micellesmicelles brushbrush--heapheap
structurestructure

20.  AgarAgar -- secondarysecondary bondsbonds (weak)(weak) holdhold thethe fibrilsfibrils
togethertogether-- breakbreak atat slightlyslightly elevatedelevated temperaturestemperatures andand
becomebecome rere--establishedestablished asas itit coolscools toto roomroom
temperaturetemperature ..
AlginateAlginate -- thethe fibrilsfibrils areare formedformed byby chemicalchemical actionaction .. AlginateAlginate -- thethe fibrilsfibrils areare formedformed byby chemicalchemical actionaction ..
Dimensional effects:Dimensional effects:
 SyneresisSyneresis
 ImbibitionImbibition

21. AGARAGAR
(REVERSIBLE HYDROCOLLOID)(REVERSIBLE HYDROCOLLOID)

22. CHEMISTRYCHEMISTRY
 The hydroxyl (OH)groups undergo hydrogenThe hydroxyl (OH)groups undergo hydrogen
bonding, leading to the formation of a helicalbonding, leading to the formation of a helical
structure.structure.
 When heatedWhen heated, the hydrogen bonds are broken,, the hydrogen bonds are broken,
the helix is uncoiled and thethe helix is uncoiled and the gel is turned intogel is turned into aa
viscous fluid.viscous fluid.viscous fluid.viscous fluid.

23. Component Function Composition
Agar Brush – heap structure 13 – 17%
Borates Strength 0.2 – 0.5%
Sulfates Gypsum hardener 1.0 – 2.0%
Wax Filler 0.5 – 1.0%
Thixotropic
materials
Thickness 0.3 – 0.5%
Water Reaction 80%
Alkyl Benzoate Preservative 0.1%
Color and Flavors Taste & appearance Trace

24. PROPERTIES OF AGARPROPERTIES OF AGAR
Accuracy and Dimensional ChangeAccuracy and Dimensional Change
 A reproduction of upto 25 micrometers is achievable with
agar hydrocolloids.
 Agar impressions are highly accurate at the time of
removal from the mouth, but shrink when stored in airremoval from the mouth, but shrink when stored in air
and expand when stored in water.

25. Clinical ImportanceClinical Importance
 SyneresisSyneresis andand imbibitionimbibition cancan resultresult inin dimensionaldimensional
changeschanges andand thereforetherefore inaccurateinaccurate castscasts.. ToTo avoidavoid thisthis
hydrocolloidhydrocolloid impressionsimpressions shouldshould bebe pouredpoured
immediatelyimmediately..

26. GelationGelation processprocess
 GelGel SolSol ((liquefactionliquefaction temperaturetemperature ))
 SolSol GelGel ((gelationgelation temperaturetemperature ))
 TemperatureTemperature laglag makesmakes itit possiblepossible toto useuse agaragar asas TemperatureTemperature laglag makesmakes itit possiblepossible toto useuse agaragar asas
dentaldental impressionimpression materialmaterial..

27.  Elasticity and Elastic Recovery.
 Agar has a tear strength of 715 gm/cm2

28. MANIPULATIONMANIPULATION
Conditioning unitConditioning unit
 LiquefyingLiquefying :: PlacedPlaced inin
boilingboiling waterwater forfor 1010 minmin
 StorageStorage:: StoredStored inin solsol
conditioncondition atat 6565ooCCconditioncondition atat 6565 CC
 TemperingTempering :: atat 4545ooCC forfor
33--1010 minutesminutes

29. MAKING THE IMPRESSION MATERIAL

30.  Syringe material, directlySyringe material, directly
taken from storagetaken from storage
compartmentcompartment -- applied on toapplied on to
the prepared tooththe prepared tooth
 Tray hydrocolloid is removedTray hydrocolloid is removed
from the tempering basin,from the tempering basin,
outer layer removed andouter layer removed andouter layer removed andouter layer removed and
impression made.impression made.
 GelationGelation is accelerated byis accelerated by
circulating cool water (18circulating cool water (18--
2121ooC) through the tray for 3C) through the tray for 3--
5 min.5 min.

31. REMOVAL FROM THE MOUTHREMOVAL FROM THE MOUTH
 The tray is removed with a sharp pull in the occlusal
direction along the long axis of the prepared teeth.
Incorrect removal will cause internal strains in the
impression material.

32. PropertiesProperties (ANSI / ADA Spec. No. 11)(ANSI / ADA Spec. No. 11)
 ElasticElastic recoveryrecovery :: 9999%% afterafter materialmaterial isis compressedcompressed
2020%% forfor 11 secondsecond..
 FlexibilityFlexibility :: 1414--1515%%
 StrengthStrength :: CompressiveCompressive strengthstrength -- 80008000g/cmg/cm22
TearTear strengthstrength -- 800800 –– 900900 g/cmg/cm22

33. AdvantageAdvantage
 Accurate dies can be prepared, if the material is
properly handled.
 It has good elastic properties and reproduces most
undercut areas correctly.
 It is not hydrophobic, it gives good model surface.
 Good patient acceptability.
 Has good recovery from distortion.
 Can be reused as duplicating material.
 Cheap as compared to synthetic elastic materials.

34. DisadvantageDisadvantage
 Tear strength very less. Greater gingival retraction is
required for providing adequate bulk of the material.
 Only one model can be poured Only one model can be poured
 Although it can be reused; It is very difficult to sterilize.
moreover when it is reheated it will cause breakdown of the
polymer structure and it will become harder and stiffer.
(maximum 4 times)
 Initial extensive and expensive equipment required.
-Special equipment like water cooled trays and temperature
controlled bath are required.

35. ALGINATEALGINATE
(IRREVERSIBLE HYDROCOLLOID)(IRREVERSIBLE HYDROCOLLOID)

36. HistoryHistory
 Developed as a substitute for the agar impression
material when its supply become scarce during World
War II.
 A chemist from Scotland perceived that certain brown A chemist from Scotland perceived that certain brown
seaweed (algae) succumbs an atypical mucous
extraction.
Anhydro-β-d-mannuronic acid or
alginic acid (insoluble in water)

37.  I. According to concentration of
sodium phosphate
 Fast set 1.25 – 2min
 Regular set 3 – 4.5 min
Classification of alginate
(Robert G. Craig)
 Regular set 3 – 4.5 min
 II. According to concentration of filler
 Soft set
 Hard set

38. Component Function Weight
percentage
Potassium alginate Soluble alginate 15
Calcium sulfate Reactor 16
Potassium titanium Accelerator 3
Composition
Potassium titanium
Fluoride
Accelerator 3
Zinc oxide Filler particles 4
Diatomaceous
earth
Filler particles 60
Sodium phosphate Retarder 2

39.  Fine silica particles become airborne from the can when lid
is removed silicosis and pulmonary hypersensitivity.
 Dustless alginate glycol incorporated to agglomerate
the particles.the particles.

40. Setting ReactionSetting Reaction
Sodium Phosphate + CalciumCalcium sulphatesulphate
Calcium Sulfate Dihydrate ++
Sodium phosphateSodium phosphate
Na / Potassium alginateNa / Potassium alginate
CalciumCalcium AlginateAlginate

41.  ControllingControlling settingsetting timetime
 AmountAmount ofof retarderretarder addedadded (manufacturer)(manufacturer)
 ByBy alteringaltering thethe temperaturetemperature ofof waterwater..
-- RateRate ofof settingsetting reactionreaction doubleddoubled byby
temperaturetemperature increaseincrease ofof 1010ooCCtemperaturetemperature increaseincrease ofof 1010ooCC

42.  PermanentPermanent deformationdeformation :: 11--11..55%% forfor 1010%% strainstrain
 FlexibilityFlexibility :: 1414%% atat aa stressstress ofof 10001000 gg /cm/cm22
StrengthStrength :: CompressiveCompressive strength=strength= 50005000--90009000 g/cmg/cm22
•• PropertiesProperties
 StrengthStrength :: CompressiveCompressive strength=strength= 50005000--90009000 g/cmg/cm22
TearTear strength=strength= 380380--700700 g/cmg/cm22
 Dimension StabilityDimension Stability
 Elasticity and Elastic RecoveryElasticity and Elastic Recovery


43. ArmamentariumArmamentarium

44. ManipulationManipulation
 TheThe measuredmeasured powderpowder isis shiftedshifted intointo prepre--measuredmeasured waterwater ..
 AA vigorousvigorous figurefigure –– 88 motion,motion, withwith thethe mixmix beingbeing stroppedstropped
againstagainst thethe sidessides ofof rubberrubber mixingmixing bowlbowl..
 MixingMixing timetime betweenbetween 4545 secssecs –– 11 minmin
SmoothSmooth CreamyCreamy MixtureMixture

46. Over Mixing Results InOver Mixing Results In
 Reduction in final strengthReduction in final strength as the gel fibrils areas the gel fibrils are
destroyed.destroyed.
 Reduction in working time.Reduction in working time.
Under Mixing Results InUnder Mixing Results In
 Inadequate wetting,Inadequate wetting, lack of homogeneity andlack of homogeneity and reducedreduced
strength.strength.
 The mix beingThe mix being grainygrainy andand poorpoor recording ofrecording of detail.detail.

47. Trays used for alginate impressions

48. Laminate TechniqueLaminate Technique
(Alginate(Alginate –– Agar Method)Agar Method)
 TheThe traytray hydrocolloidhydrocolloid isis replacedreplaced withwith aa mixmix ofof chilledchilled
alginatealginate thatthat bondsbonds toto thethe syringesyringe agaragar ..
 AlginateAlginate gelsgels byby aa chemicalchemical reactionreaction AlginateAlginate gelsgels byby aa chemicalchemical reactionreaction
 AgarAgar gelsgels byby meansmeans ofof contactcontact withwith thethe coolcool hydrocolloidhydrocolloid..
 MaximumMaximum detaildetail isis producedproduced

49. AdvantageAdvantage
 Syringe agar gives better details
 Less air bubbles
 Water cooled trays are not required
 It sets faster than regular agar technique
ShortShort comingscomings
 BondBond betweenbetween agaragar andand alginatealginate isis notnot alwaysalways strongstrong..
 HigherHigher viscosityviscosity alginatealginate displacesdisplaces thethe agaragar duringduring seatingseating..
 DimensionalDimensional accuracyaccuracy ofof alginatealginate limitslimits thethe useuse toto singlesingle
unitsunits..

50. Wet Field TechniqueWet Field Technique
 TheThe areasareas toto bebe recordedrecorded areare actuallyactually floodedflooded withwith warmwarm
waterwater.. ThenThen thethe syringesyringe materialmaterial isis introducedintroduced quickly,quickly,
liberally,liberally, andand inin bulkbulk toto covercover thethe occlusalocclusal and/orand/or incisalincisal
areasareas onlyonly..
 WhileWhile thethe syringesyringe materialmaterial isis stillstill liquid,liquid, thethe traytray
materialmaterial isis seatedseated.. TheThe hydraulichydraulic pressurepressure ofof thethe viscousviscous
traytray materialsmaterials forcesforces thethe fluidfluid syringesyringe hydrocolloidhydrocolloid downdown
intointo thethe areasareas toto bebe restoredrestored..
 ThisThis motionmotion displacesdisplaces thethe syringesyringe materialsmaterials asas wellwell asas
bloodblood andand debrisdebris throughoutthroughout thethe sulcussulcus..

51.  AlginateAlginate inin thethe formform ofof solsol -- containingcontaining thethe waterwater butbut
nono sourcesource ofof calciumcalcium ionsions -- aa reactorreactor ofof PlasterPlaster ofof
ParisParis ..
 TwoTwo componentcomponent systemsystem (paste(paste form)form)
-- alginatealginate solsol
Modified alginatesModified alginates
-- calciumcalcium reactorreactor
AlginatesAlginates modifiedmodified byby thethe incorporationincorporation ofof siliconesilicone
polymerspolymers (paste(paste form)form)
-- finefine detaildetail reproductionreproduction
-- teartear resistanceresistance
-- poorpoor dimensionsdimensions stabilitystability

52.  StorageStorage temperaturetemperature
 MoistureMoisture contaminationcontamination
Shelf lifeShelf life
 MoistureMoisture contaminationcontamination

53. Effects of MishandlingEffects of Mishandling

55. DisinfectionDisinfection

56. Impression compoundImpression compound
(ANSI/ADA specification No.3)(ANSI/ADA specification No.3)

57. CompositionComposition
 WaxesWaxes
 Thermoplastic resinsThermoplastic resins
 FillerFiller
 Coloring agentColoring agent
 Shellac,Shellac, stearicstearic acid andacid and guttagutta perchapercha Shellac,Shellac, stearicstearic acid andacid and guttagutta perchapercha
ClassifiedClassified : Type I: Type I –– low fusinglow fusing
Type IIType II –– high fusinghigh fusing

58.  Current protocolCurrent protocol -- recommended by Centerrecommended by Center
for Disease Controlfor Disease Control
-- household bleach (1:10 dilution)household bleach (1:10 dilution)
-- iodophorsiodophors
-- synthetic phenolssynthetic phenols
••DisinfectionDisinfection
-- synthetic phenolssynthetic phenols
 Sprayed on exposed surfaceSprayed on exposed surface -- wrapped inwrapped in
disinfectant soaked paper toweldisinfectant soaked paper towel -- sealedsealed
plastic bag for 10 minplastic bag for 10 min
oror
 ImmersionImmersion -- not exceeding 10not exceeding 10 minsmins

59.  IntroducedIntroduced inin latelate 19501950’s’s –– overcomeovercome thethe drawbacksdrawbacks ofof hydrocolloidshydrocolloids
-- poorpoor dimensionaldimensional stabilitystability
-- inadequateinadequate teartear resistanceresistance
 SettingSetting occursoccurs throughthrough aa combinationcombination ofof chainchain lengtheninglengthening
NON-AQUEOUS ELASTOMERIC IMPRESSION MATERIALS
polymerizationpolymerization andand chemicalchemical crosscross linkinglinking
-- condensationcondensation reactionreaction
-- additionaddition reactionreaction
 TheThe chainschains ofof thesethese materialsmaterials uncoiluncoil onon stretchingstretching andand uponupon removalremoval
ofof thethe stressstress theythey bouncebounce backback oror snapsnap backback toto theirtheir relaxedrelaxed entangledentangled
statestate..

60. CLASSIFICATIONCLASSIFICATION
I. Chemically four kinds ofI. Chemically four kinds of elastomerselastomers
 PolysulfidePolysulfide
 Condensation polymerizing siliconeCondensation polymerizing silicone Condensation polymerizing siliconeCondensation polymerizing silicone
 Addition polymerizing siliconeAddition polymerizing silicone
 PolyetherPolyether

61. II. Based on the physical propertiesII. Based on the physical properties
((ADA specification No.19)ADA specification No.19)
Type Maximum%
Compression set
Maximum%
Flow
Maximum%
Shrinkage
(24 hours)
I 2.5 0.5 0.5I 2.5 0.5 0.5
II 2.5 0.5 1.0
III 5.5 2.0 0.5

62. III. Based on the viscosityIII. Based on the viscosity (ISO 4823)(ISO 4823)
 TypeType
33 --Low viscosity (light body)Low viscosity (light body)
22 --Medium viscosity (medium body)Medium viscosity (medium body)
11 --High viscosity (heavy body)High viscosity (heavy body)
00 --Very high viscosity (Putty)Very high viscosity (Putty)

63. According to method of polymerization:According to method of polymerization:
 Addition polymerization materialsAddition polymerization materials
 Condensation polymerization materialsCondensation polymerization materials

64. PolysulfidePolysulfide
(Synonyms : Rubber base,(Synonyms : Rubber base, MercaptonMercapton, Thiokol ), Thiokol )
Commercial names: Coe-flex, Omni-flex

65. Component Function
Base Paste
Polysulfide prepolymer with
terminal and pendant thiol
(-SH) groups.
This is further polymerized and
cross linked to form rubber
Dibutyl pthalate Platicizer to control viscosity
Inert filler
(lithopone or titanium
dioxide)
Sulfur
To provide the required
Strength
Accelerate the reaction
Reactor
paste
Lead dioxide (Brown)
Or
Hydrated copper
oxide (Green)
Oxidizer
Oleic or stearic acid Retarder to control the
rate of setting reactions
Plasticizer and fillers

66.  PackagedPackaged asas twotwo pastespastes
BaseBase (white)(white)
CatalystCatalyst (brown)(brown)
 AvailableAvailable inin threethree consistenciesconsistencies
 LightLight bodybody LightLight bodybody
 MediumMedium bodybody
 HeavyHeavy bodybody

67. The terminal and pendant thiol (SH ) group of each molecule is
oxidized by the addition of oxidizing agent present in the reaction
paste
Setting reactionSetting reaction
paste
Mercaptan + Lead dioxide Polysulfide rubber + Water
 Condensation type of reaction.

68. ApplicationApplication
 Widely used in operative & crown bridge procedure
 Low cost
 High accuracy

69. PropertiesProperties
 Mixing time: 45 seconds.Mixing time: 45 seconds.
 Working time :5Working time :5--7min7min

70. PropertiesProperties
 High tear resistance & enhanced elastic property
facilitates impression making in sulcular areas &
pinholes, & has improved dimensional stability over
hydrocolloids but less than addition silicon & polyether.
 Large undercut areas in interproximal region should be
blocked out in mouth with soft wax.
 Thin layer of moisture cause creases, folds & voids in
impression fins & assorted projections on cast.

71.  Unique property Radiopaque
Contributes to toxicity & tendency to irritate soft tissues
when it becomes trapped.
 Any hemorrage/fluid seepage in sulcus voids & Any hemorrage/fluid seepage in sulcus voids &
bubbles obscure the finish line.
 Least expensive elastomer.

72. Impression armamentariumImpression armamentarium
1) Polysulfide impression kit ( regular base &accelerator)
2) Polysulfide impression kit ( light base &accelerator)
3) Adhesive (butyl rubber cement)
4) Two mixing pad
Two stiff spatulas5) Two stiff spatulas
6) Syringe
7) Alcohol
8) Custom resin tray

73. Impression MakingImpression Making

77. Advantages Disadvantages
- High tear strength - Dimensionally unstable
- Long working time - Unacceptable odor
- Established precision - Untidy and stains clothing
- Economic - Long setting time
- Extensive shelf life - Least elastic recovery
- Less hydrophobic - Subsequent pours are less
accurate.

78. CONDENSATION SILICONECONDENSATION SILICONE
(SILICONE, POLYSILOXANE ORGANO(SILICONE, POLYSILOXANE ORGANO--TIN SILICONE)TIN SILICONE)
Commercial name: Sil 21, Coltex

79. Composition Components Function
Base paste
Hydroxyl terminated
polydimethyl siloxane
prepolymer
undergoes cross linking
to form rubber
Silica FillerSilica Filler
Reactor
Ethyl ortho-Silicate Cross linking agent
Stannous octate Catalyst

80. SETTING REACTIONSETTING REACTION
OrthoethylOrthoethyl Silicate +Silicate + DimethylDimethyl SiloxaneSiloxane
stannousstannous octoateoctoate
Silicon Rubber + Ethyl AlcoholSilicon Rubber + Ethyl Alcohol
 Limited shelf life of catalystLimited shelf life of catalyst -- instability of ethyl silicate ininstability of ethyl silicate in
the presence of tin compounds oxidation of tin.the presence of tin compounds oxidation of tin.

81.  Available as two consistenciesAvailable as two consistencies
 Putty (75%filler)Putty (75%filler)
 Light body (35%filler)Light body (35%filler)

82. PropertiesProperties
 Pleasant color & odour, non toxic.
 Setting time 6-8 min
 Excellent reproduction of surface details.
 Less dimensional stability, therefore cast should be
poured immediately.poured immediately.
 Tear strength 3000gm/cm2
 Stiffer & harder than polysulfide.

83. ArmamentariumArmamentarium
 Silicon impression kit(putty, base & accelerator)
 Tray adhesive(poly siloxane,ethly silicate)
 Mixing pad
 Stiff spatula
 Syringe Syringe
 Stock tray

84. Impression MakingImpression Making
 SelectSelect stockstock traytray
 ThinThin coatcoat ofof adhesiveadhesive
 22 scoopscoop ofof puttyputty onon padpad && 66
dropdrop ofof accceleratoracccelerator
 TransferTransfer onon palmpalm && kneedkneed
 Roll base &place in trayRoll base &place in tray
 Cover base with polyethyleneCover base with polyethylene
spacer & place in mouthspacer & place in mouth
 Remove tray after 2 minRemove tray after 2 min

85.  Peel off spacer
 Isolate
 On mixin pad, mix thin
wash silicon
 Add acclerator
 Place material in syringe
 Inject in sulcus, aorund
circumferance of
preparation
 Hold tray for 6 min

86. Advantages Disadvantages
- Agreeable odor & stain free - Inadequate dimensional
stability
- Satisfactory working & setting
time
- Inadequate shelf life
time
- Enhanced elastic recovery - Hydrophobic
- Adequate tear strength

87. ADDITION SILICONEADDITION SILICONE
{POLYVINYL SILOXANE, VINYL(POLYSILOXANE)}{POLYVINYL SILOXANE, VINYL(POLYSILOXANE)}
Commercial name: Reprosil, Provil

88. Components Function
Base paste
Hydroxyl terminated
polymethyl siloxane
prepolymer
Undergoes
cross linking
to form rubber
CompositionComposition
Colloidal silica Filler
Reactor
Polyvinyl silicone
prepolymer
Colloidal silica Filler
Chloroplatinic
acid
Catalyst

89.  Reaction occurs by crossReaction occurs by cross--linkinglinking
Polyvinyl silicone +Polyvinyl silicone +PolymethylPolymethyl siloxanesiloxane SiliconSilicon
RubberRubber
Chloroplatinic acidChloroplatinic acid
Setting reactionSetting reaction
RubberRubber
 No by product formedNo by product formed
 Imbalance between base and reactorImbalance between base and reactor-- hydrogen gashydrogen gas
 Hydrogen gas scavengerHydrogen gas scavenger -- platinum or palladiumplatinum or palladium

90.  Inherently hydrophobic nonionic surfactant
- allows impression material to readily wet soft
tissue
- enhance the ability of gypsum to obtain
maximum detail
 Sulfur contamination from natural latex gloves inhibits the
setting of addition silicones.
 Mixing guns have become more popular method for
dispensing & mixing,eliminating spatula & mixing pad.

91.  Available in 4 consistenciesAvailable in 4 consistencies
 Light bodyLight body
 Medium bodyMedium body
 Heavy bodyHeavy body
 PuttyPutty

92. PropertiesProperties
 Pleasant odor & color.
 Excellent reproduction of surface details
 Setting time 5-9 min
 Pouring delayed for 30 min, coz of release of hydrogen
gas.
 Best dimensional stability, low curing shrinkage(.17%), Best dimensional stability, low curing shrinkage(.17%),
lowest permenant deformation(.05%)
 Good tear strength
 Harder than poly sulfides.
 Setting inhibition caused by some brands of latex gloves.
 Can be electroplated.
 Shelf life 1-2 yrs.

93. Advantages Disadvantages
- Excellent dimensional accuracy - Hydrophobic
- Long term dimensional stability - Expensive
- Hydrogen gas evaluation
in some materials
- Pleasant to use
in some materials
- Short setting time - Hydrophilic formulations
imbibe moisture- Auto mix available
- If hydrophilic, good compatibility
with gypsum
- Sulfur contamination by
latex glove

94.  Newer Formulations
 Hydrophilic – addition of surfactant
 Hydrogen gas scavenger – Palladium
 Monophase – Shear thinning
 Stiffer – Bite registration
Bite registration paste Duplicating
material

95. ArmamentariumArmamentarium
1. Dispenser
2. Cartidge
3. Mixing tip
4. Mixing pad
Syringe5. Syringe
6. Custom adhesive tray
7. Tray adhesive

96. Impression MakingImpression Making
Double mix techniqueDouble mix technique

98.  Load tray with heavy
body
 Seat it firmly in mouth
 Hold for 7 min

99. POLYETHERPOLYETHER
((epimineepimine))
Commercial names: Impregum F, Polyjel

100. CompositionComposition
Base Paste
Imine terminated
prepolymer
Becomes cross linked
to form rubber
Silica Filler – to control
viscosity
Pthalate Plasticizer
Reactor
paste
Alkyl aromatic
sulfonate
Initiates cross linking
Silica Filler
Pthalate Plasticizer

101.  PolyetherPolyether ++ SulfonicSulfonic esterester CrossCross LinkedLinked RubberRubber
 ItIt isis curedcured byby aa reactionreaction b/wb/w aziridineaziridine ringring ,, whichwhich areare atat
thethe endend ofof polyetherpolyether moleculemolecule..
 MainMain chainchain isis copolymercopolymer ofof ethyleneethylene didi oxideoxide &&
Setting reactionSetting reaction
tetrahydrofuranetetrahydrofurane..
 CrossCross linkinglinking isis broughtbrought byby aromaticaromatic sulfonatesulfonate esterester viavia
imineimine groupgroup..
 ReactionReaction isis exothermicexothermic..

102. Available in 3 consistenciesAvailable in 3 consistencies
 Light bodyLight body
 Medium bodyMedium body Medium bodyMedium body
 Heavy body.Heavy body.

103. PropertiesProperties
 High dimension stability, accurate cast produced evenHigh dimension stability, accurate cast produced even
after 24 hrs.after 24 hrs.
 Affinity with water , making itAffinity with water , making it hydrophillichydrophillic..
 Material is stiff, undercuts must be blocked.Material is stiff, undercuts must be blocked. Material is stiff, undercuts must be blocked.Material is stiff, undercuts must be blocked.
 Allergic reaction exhibited 0.5% due to aromaticAllergic reaction exhibited 0.5% due to aromatic
sulfonatesulfonate catalyst.catalyst.
 Electroplated with silverElectroplated with silver
 Shelf life more than 2 yrs.Shelf life more than 2 yrs.

104. ArmamentariumArmamentarium
 Impression kit
 Tray adhesive
 Mixing pad
 Stiff spatula
Syringe Syringe
 Custom resin tray

105. Impression MakingImpression Making
Custom tray
Adhessive applied
Base & accelerator paste mixed
( unmixed- allergic reaction)( unmixed- allergic reaction)
Load back end of syringe(Load tray
simuntanously)
Inject impression in interproximal
areaseat tray firmly
Hold for 4 min

106. Advantages Disadvantages
Dimensional stability - Set material very stiff
Accuracy - Imbibition
Shorter setting time - Short working time.
Automix available - Allergic hypersensitivity in some cases.

107. POLYETHER URETHANEPOLYETHER URETHANE
DIMETHACRYLATEDIMETHACRYLATE
 CompositionComposition
-- polyether urethanepolyether urethane dimethacrylatedimethacrylate resin.resin.
-- diketonediketone initiatorinitiator
-- amine acceleratoramine accelerator-- amine acceleratoramine accelerator
-- 4040 –– 60% silica filler60% silica filler
 Clear tray, photo initiated by 400Clear tray, photo initiated by 400 –– 500 nm blue500 nm blue
lightlight
 AdvantageAdvantage -- unlimited working timeunlimited working time
-- short setting timeshort setting time
 DisadvantageDisadvantage -- surface polymerizationsurface polymerization

108.  MANIPULATIONMANIPULATION OFOF IMPRESSIONIMPRESSION MATERIALMATERIAL
 PastePaste formform -->> equalequal lengthslengths ofof basebase andand reactorreactor pastepaste
takentaken overover thethe mixingmixing padpad -- reactorreactor pastepaste isis firstfirst spreadspread
overover thethe basebase paste,paste, mixingmixing continuedcontinued untiluntil aa smooth,smooth,
homogenous,homogenous, streakstreak freefree mixmix isis obtainedobtained..
 WhenWhen reactorreactor suppliedsupplied inin liquidliquid formform -->> numbernumber ofof
dropsdrops perper unitunit lengthlength areare recommendedrecommended byby manufacturermanufacturer..
 TwoTwo puttyputty systemsystem -->> kneadedkneaded betweenbetween thethe fingersfingers

109. Automatic Mixing devicesAutomatic Mixing devices

110.  UsedUsed forfor lightlight andand mediummedium viscosityviscosity materialsmaterials ofof additionaddition
silicone,silicone, condensationcondensation siliconesilicone andand polyetherspolyethers,, notnot
polysulfidespolysulfides..
 prepackagedprepackaged cartridgescartridges
 disposabledisposable mixingmixing tiptip
 TheThe cartridgecartridge insertedinserted inin aa gungun likelike device,device, andand basebase andand
catalystcatalyst areare extrudedextruded intointo thethe spiralspiral mixingmixing tip,tip, wherewhere mixingmixing
occursoccurs asas theythey progressprogress toto thethe endend ofof thethe tubetube..

111.  AdvantagesAdvantages
 GreaterGreater uniformityuniformity inin proportioningproportioning andand inin
mixingmixing..
 LessLess airair incorporatedincorporated intointo thethe mixmix..
 MixingMixing timetime reducedreduced.. MixingMixing timetime reducedreduced..
 LessLess chancechance ofof mixmix gettinggetting contaminatedcontaminated
 LessLess wastagewastage ofof materialmaterial..

112. Dynamic mechanical mixerDynamic mechanical mixer

113.  TheThe devicedevice usesuses aa motormotor toto drivedrive parallelparallel plungersplungers
thatthat forceforce thethe materialsmaterials intointo aa mixingmixing tip,tip, andand thethe
spiralspiral insideinside thethe mixingmixing tiptip rotatesrotates asas thethe materialmaterial areare
extrudedextruded throughthrough thethe tiptip..extrudedextruded throughthrough thethe tiptip..
 HigherHigher viscosityviscosity materialmaterial cancan bebe mixedmixed..

114.  ViscoelasticityViscoelasticity -- dependence of an impressiondependence of an impression
material’s response to the speed of removalmaterial’s response to the speed of removal
PROPERTIESPROPERTIES
ViscoelasticViscoelastic PropertiesProperties
 ViscoelasticViscoelastic behaviorbehavior -- intermediate betweenintermediate between
that of an elastic solid and a viscous liquid.that of an elastic solid and a viscous liquid.

115.  Elastic solidElastic solid Spring, deforms instantly toSpring, deforms instantly to
a certain extent when one applies a specifica certain extent when one applies a specific
loadload -- deformation reversed completely ondeformation reversed completely on
removal of the load.removal of the load.
 Viscous liquidViscous liquid Oil dashpot, which does notOil dashpot, which does not
respond instantly but deforms as the load isrespond instantly but deforms as the load is
applied over timeapplied over time -- deformation is permanent.deformation is permanent.

116. MaxwellMaxwell--Voigt modelVoigt model

117.  Clinical importanceClinical importance
The amount of permanent deformationThe amount of permanent deformation
attributed to either dashpot, is dictated by theattributed to either dashpot, is dictated by the
duration of tension or compression exerted onduration of tension or compression exerted onduration of tension or compression exerted onduration of tension or compression exerted on
the materialsthe materials -- snap removalsnap removal

118.  Working and Setting time:Working and Setting time:
 Working time :Working time : is the time elapsed from the start ofis the time elapsed from the start of
mix until the material is loaded on to the tray /mix until the material is loaded on to the tray /
syringe.syringe.
 End of Working timeEnd of Working time --defined as the time when adefined as the time when a
blunt needle fails to penetrate a volume ofblunt needle fails to penetrate a volume of
impression material to a specified depth.impression material to a specified depth.
 Measured at room temperatureMeasured at room temperature
 Mixing timeMixing time : is the time required to obtain a: is the time required to obtain a
uniform mixuniform mix

119.  Setting timeSetting time -- defined as the transitional time atdefined as the transitional time at
which plastic properties which permit molding andwhich plastic properties which permit molding and
impression taking are lost and elastic propertiesimpression taking are lost and elastic properties
permitting removal of the impression material arepermitting removal of the impression material are
acquiredacquired
orororor
 When a blunt instrument fails to permanently indentWhen a blunt instrument fails to permanently indent
the set impression materials.the set impression materials.
 Measured at mouth temperature.Measured at mouth temperature.

120.  Effects of temperatureEffects of temperature
 IncreaseIncrease -- both working and setting timeboth working and setting time
decreased by accelerating the curing ratedecreased by accelerating the curing rate
DecreaseDecrease -- working time increased byworking time increased by DecreaseDecrease -- working time increased byworking time increased by
refrigerating the materials or mixing on arefrigerating the materials or mixing on a
chilled dry glass slabchilled dry glass slab

121.  Effect of viscosityEffect of viscosity
 IncreaseIncrease -- decrease working time and setting timedecrease working time and setting time
 Altering base / catalyst ratioAltering base / catalyst ratio : alter the: alter the
working and setting timeworking and setting time -- adversely affects theadversely affects the
mechanical propertiesmechanical properties

122. Impression
materials
Mean working
time (min)
Mean setting
time (min)
23oC 37oC 23oC 37oC
Polysulfide 6.0 4.3 16.0 12.5
Condensation 3.3 2.5 11.0 8.9Condensation
silicone
3.3 2.5 11.0 8.9
Addition silicone 3.1 1.8 8.9 5.9
Polyether 3.3 2.3 9.0 8.3

123.  Clinical importanceClinical importance
 Dual arch technique for single crown preparationDual arch technique for single crown preparation
Quick set materialQuick set material –– short working time.short working time.
 Full arch impression with multiple prepared teeth.Full arch impression with multiple prepared teeth.
Longer working timeLonger working time

124.  DIMENSIONAL STABILITYDIMENSIONAL STABILITY
 Five major sources of dimensionalFive major sources of dimensional
changeschanges
 Polymerization shrinkagePolymerization shrinkage
 Loss of by product (water or alcohol) duringLoss of by product (water or alcohol) during Loss of by product (water or alcohol) duringLoss of by product (water or alcohol) during
condensation reactioncondensation reaction
 Thermal contraction from oral temperature toThermal contraction from oral temperature to
room temperatureroom temperature
 ImbibitionImbibition -- exposed to water, disinfectant or highexposed to water, disinfectant or high
humidity environment over a period of timehumidity environment over a period of time
 Incomplete recovery of deformationIncomplete recovery of deformation

125.  Addition siliconeAddition silicone -- most stablemost stable
 PolyetherPolyether -- poured within 1 hourpoured within 1 hour
 Condensation siliconeCondensation silicone
 PolysulfidePolysulfide
-- poured withinpoured within
30 minutes30 minutes

126. ACCURACYACCURACY
 ANSI/ADA specification No.19ANSI/ADA specification No.19 -- reproduce finereproduce fine
detail ofdetail of 2525 μmμm or less.or less.
 Putty record onlyPutty record only uptoupto 7575 μmμm
 Corresponding specification for gypsum dieCorresponding specification for gypsum die
materials ismaterials is 50μm50μm
 Most accurateMost accurate -- Addition siliconeAddition silicone
-- Reversible hydrocolloidReversible hydrocolloid

127. ELASTICELASTIC RECOVERYRECOVERY::
 ElasticElastic recoveryrecovery --
“rebound”“rebound” backback toto itsits originaloriginal
shape,shape, whenwhen thethe setset
impressionimpression isis removedremoved fromfrom
thethe mouthmouth ..
CondensationCondensation
siliconesilicone
PVSPVS
thethe mouthmouth ..
 ElasticElastic recoveryrecovery cancan bebe
maximizedmaximized byby blockingblocking thethe
undercutsundercuts..
PolysulfidePolysulfide
PolyetherPolyether

128. RHEOLOGY:RHEOLOGY:
Light body materials flow readily into minuteLight body materials flow readily into minute
details.details.
 Tray or heavy body material provide moreTray or heavy body material provide more
rigidity to the impression .rigidity to the impression .
 Early versions of light body tended to flow offEarly versions of light body tended to flow off
the prepared tooth with timethe prepared tooth with time -- newer PVS andnewer PVS and
polyether arepolyether are thixotropicthixotropic..

129.  MonophasicMonophasic materialmaterial -- shear thinning effectshear thinning effect --
“false body” permits the material to stay in the“false body” permits the material to stay in the
tray without sagging or dripping, yet the sametray without sagging or dripping, yet the same
material can be used in a syringe.material can be used in a syringe.
 Material that exhibits this property of becomingMaterial that exhibits this property of becoming
more fluid when shear rate is increasedmore fluid when shear rate is increased --
thioxtrophicthioxtrophic

130. PolyPoly
etherether
PVSPVS
Flexibility
PolysulfidePolysulfide
CondensationCondensation
siliconesilicone

131.  PolyetherPolyether -- most rigidmost rigid
 Problem when dealing with long, thinProblem when dealing with long, thin
preparations ofpreparations of periodontallyperiodontally involved teethinvolved teeth
 Result in fracture of diesResult in fracture of dies Result in fracture of diesResult in fracture of dies
 AdvantageAdvantage -- dual arch impressionsdual arch impressions -- double bitedouble bite
trays are flexibletrays are flexible -- rigid material is advantageousrigid material is advantageous

132. TEAR STRENGTH:TEAR STRENGTH:
 Important propertyImportant property -- inin
inter proximal and subinter proximal and sub
gingival areas.gingival areas.
Influenced byInfluenced by
PolyetherPolyether
PolyPoly
sulfidesulfide
 Influenced byInfluenced by
 ConsistencyConsistency -- increasedincreased
viscosity increases tearviscosity increases tear
strengthstrength
 Manner of removalManner of removal --
rapid rate of force duringrapid rate of force during
removal increases tearremoval increases tear
strengthstrength
SiliconeSilicone
HydrocolloidsHydrocolloids

133.  HYDROPHILLICITY:HYDROPHILLICITY:
 Two different aspects of theTwo different aspects of the hydrophobichydrophobic
nature ofnature of elastomerselastomers::
 High contact angle that forms when polymerizedHigh contact angle that forms when polymerized
impressions are wetted with dental gypsum materialsimpressions are wetted with dental gypsum materials
 Lack of ability of the impression material to wet theLack of ability of the impression material to wet the
oral tissues during impression makingoral tissues during impression making

134.  PVS and Condensation siliconesPVS and Condensation silicones ––hydrophobichydrophobic
 Contains hydrophobic aliphatic hydrocarbon groupsContains hydrophobic aliphatic hydrocarbon groups
surrounding thesurrounding the siloxanesiloxane bondbond
 Polyether andPolyether and polsulfidespolsulfides -- hydrophilichydrophilic
 Contain functional groups that attract and interactContain functional groups that attract and interact Contain functional groups that attract and interactContain functional groups that attract and interact
with water molecules through hydrogen bondingwith water molecules through hydrogen bonding
 Newer materialsNewer materials -- classified as hydrophilicclassified as hydrophilic
 Including nonIncluding non--ionic surfactantsionic surfactants
 Grafting the surfactant to silicone polymerGrafting the surfactant to silicone polymer

135.  BIOCOMPATIBILITY:BIOCOMPATIBILITY:
 CellCell cytotoxicitycytotoxicity
 polysulfidepolysulfide -- lowestlowest
 polyetherpolyether -- highesthighest
 ElastomerElastomer –– induced biocompatibility problem occursinduced biocompatibility problem occurs ElastomerElastomer –– induced biocompatibility problem occursinduced biocompatibility problem occurs
when a segment is lodged in patients gingivalwhen a segment is lodged in patients gingival sulcussulcus --
gingival inflammationgingival inflammation
 RadiopacityRadiopacity of Polysulfideof Polysulfide
 Contact dermatitisContact dermatitis from polyether catalyst to dentalfrom polyether catalyst to dental
assistant has been reportedassistant has been reported

136. SHELF LIFE:SHELF LIFE:
 Stored in a dry, cool environment.Stored in a dry, cool environment.
 Tubes should be kept tightly closedTubes should be kept tightly closed
Arbitrarily suggested that no more than 6Arbitrarily suggested that no more than 6 Arbitrarily suggested that no more than 6Arbitrarily suggested that no more than 6
months supply should be kept on hand at anymonths supply should be kept on hand at any
time.time.

137.  Economic factorsEconomic factors
 Reversible hydrocolloid less expensive thanReversible hydrocolloid less expensive than
elastomerselastomers, but equipments associated with it, but equipments associated with it
compensates for the costcompensates for the cost
 Polyether and PVS most expensivePolyether and PVS most expensive Polyether and PVS most expensivePolyether and PVS most expensive
 Cost reduced by using autoCost reduced by using auto--mix devices &mix devices &
dual arch technique when indicateddual arch technique when indicated

138. MATERIALMATERIAL ADVANTAGESADVANTAGES DISADVANTAGESDISADVANTAGES
ALGINATEALGINATE Rapid set, HydrophilicRapid set, Hydrophilic
Low cost, No custom trayLow cost, No custom tray
requiredrequired
Poor accuracy & surfacePoor accuracy & surface
details, Low tear résistancedetails, Low tear résistance
Low stability.Low stability.
AGARAGAR--AGARAGAR Long working timeLong working time
HydrophilicHydrophilic
Low tear résistanceLow tear résistance
Low stabilityLow stability
Equipment requiredEquipment required
POLYSULFIDEPOLYSULFIDE High tear resistanceHigh tear resistance Long setting timeLong setting time
Unpleasant odor, StickyUnpleasant odor, StickyUnpleasant odor, StickyUnpleasant odor, Sticky
ADDITIONADDITION
SILICONESILICONE
Dimensional stability,Dimensional stability,
excellent accuracy, Autoexcellent accuracy, Auto
mix availablemix available
Hydrophobic, release ofHydrophobic, release of
hydrogen gas,hydrogen gas,
Most expensiveMost expensive
CONDENSATIONCONDENSATION
SILICONESILICONE
Fair accuracy, short settingFair accuracy, short setting
timetime
Release of AlcoholRelease of Alcohol
byproduct, Hydrophobic.byproduct, Hydrophobic.
POLYETHERPOLYETHER Dimensionally stable,Dimensionally stable,
accurate, Auto mixaccurate, Auto mix
availableavailable
Rigid,Rigid, imbibitionimbibition
short working time,short working time,

139.  Effects of mishandlingEffects of mishandling elastomerselastomers
 Rough or uneven surface on impressionRough or uneven surface on impression
 BubblesBubbles
 Irregularly shaped voidsIrregularly shaped voids Irregularly shaped voidsIrregularly shaped voids
 Rough or chalky stone castRough or chalky stone cast
 DistortionDistortion

140. DUPLICATING MATERIALSDUPLICATING MATERIALS
(ANSI/ADA Specification No. 20)(ANSI/ADA Specification No. 20)

141.  Hydrocolloids are used to duplicate dental castsHydrocolloids are used to duplicate dental casts
or modelsor models
-- construction of prosthetic appliances andconstruction of prosthetic appliances and
orthodontic productsorthodontic products
 Reversible (Agar) HydrocolloidReversible (Agar) Hydrocolloid
 Same composition as impression materialSame composition as impression material -- Same composition as impression materialSame composition as impression material --
water content is higherwater content is higher
 Classification (Classification (ANSI/ADA specification No.20)ANSI/ADA specification No.20)
 Type IType I –– Thermo reversibleThermo reversible
 Type IIType II –– Non reversibleNon reversible
 Silicones and polyetherSilicones and polyether -- expensiveexpensive

142. ZINCZINC--OXIDE EUGENOLOXIDE EUGENOL
IMPRESSION PASTESIMPRESSION PASTES
(ANSI / ADA SPECIFICATION No.16)(ANSI / ADA SPECIFICATION No.16)

143. Base Percentage Function
Zinc Oxide 87 Reactive ingredient
Fixed vegetable or
mineral oil
13 Plasticizer, off sets action
of eugenol as an irritant
Catalyst
Oil of cloves or eugenol 12 Oil of cloves contain 70% -
85%, eugenol less irritating
Gum or polymerized rosin 50 To accelerate settingGum or polymerized rosin 50 To accelerate setting
Filler 20 Strength
Lanolin 3
Resinous balsam 10 To increase flow and
improve mixing properties
Color 5

144.  Classified asClassified as
Type IType I –– hard paste (10 min)hard paste (10 min)
Type IIType II –– soft paste (15 min)soft paste (15 min)
 Setting timeSetting time
ShortenedShortened -- adding small amount ofadding small amount of
acceleratoraccelerator
-- drop of waterdrop of water-- drop of waterdrop of water
ProlongedProlonged -- cool mixing slabcool mixing slab
-- plasticizerplasticizer –– inert oil or waxinert oil or wax
 Dimensional stabilityDimensional stability
-- Less than 0.1% shrinkageLess than 0.1% shrinkage

145.  NonNon--eugenoleugenol pastespastes
 OrthoethoxybenzoicOrthoethoxybenzoic acid (EBA)acid (EBA) -- substitutesubstitute
forfor eugenoleugenol
 Bactericidal agents and other medicamentsBactericidal agents and other medicaments

146.  Surgical pastesSurgical pastes
 AfterAfter gingivectomygingivectomy
aid in the retention of a medicamentaid in the retention of a medicament
promote healingpromote healing
 Softer and slower in their setting reactionSofter and slower in their setting reaction

147.  Bite registration pastesBite registration pastes
 OcclusalOcclusal relationshipsrelationships -- impression plaster,impression plaster,
compound wax, resin and metal oxide pastecompound wax, resin and metal oxide paste
 ZOE pasteZOE paste -- construction of completeconstruction of complete ZOE pasteZOE paste -- construction of completeconstruction of complete
dentures and fixed or RPD.dentures and fixed or RPD.
 ZOEZOE interocclusalinterocclusal record more stable than onerecord more stable than one
made in waxmade in wax

148. ConclusionConclusion
TheThe abilityability toto recordrecord consistentlyconsistently goodgood impressionsimpressions isis
bothboth aa sciencescience andand anan artart..
ImpressionImpression techniques,techniques, methodsmethods andand materialsmaterials areare
evolvingevolving andand changingchanging butbut underlyingunderlying principlesprinciples andandevolvingevolving andand changingchanging butbut underlyingunderlying principlesprinciples andand
fundamentalsfundamentals remainremain constantconstant..
AnAn idealideal impressionimpression mustmust bebe inin thethe mindmind ofof thethe dentistdentist
beforebefore itit cancan bebe inin hishis handhand.. ItIt isis thisthis knowledgeknowledge andand
experienceexperience thatthat enablesenables aa dentistdentist toto createcreate desirabledesirable resultsresults

149. ReferencesReferences
 Philip’s science of Dental MaterialsPhilip’s science of Dental Materials –– Eleventh Edition.Eleventh Edition.
AnusaviceAnusavice
 Restorative Dental MaterialsRestorative Dental Materials -- Eleventh Edition. RobertEleventh Edition. Robert
G. CraigG. Craig
Fundamentals of FixedFundamentals of Fixed ProsthodonticsProsthodontics -- Third Edition.Third Edition. Fundamentals of FixedFundamentals of Fixed ProsthodonticsProsthodontics -- Third Edition.Third Edition.
ShillingburgShillingburg
 Contemporary FixedContemporary Fixed ProsthodonticsProsthodontics -- Second Edition.Second Edition.
RoseinsteilRoseinsteil Art and Science of Operative DentistryArt and Science of Operative Dentistry --
Fourth Edition.Fourth Edition. SturdevantSturdevant