Impression techniques

this presentation includes various techniques used while taking impressions in dental practice.

1. PRESENTED BY:PRESENTED BY:
DR MEENAL ATHARKAR
MDS
DEPT OF ENDO AND CONS

2. 
Based on the position of the mouth

Open mouth technique

Closed mouth technique (functional impression )

Based on the pressure applied

Positive pressure

Negative pressure

Selective pressure technique

3. 
Based on the mixing technique

Double mix

Heavy-light body technique

Putty wash technique
One stage –simultaneous
Two stage –relief channel
-2mm spacer technique-2mm spacer technique

Single mix or monophasetechnique

According to the tray used

Custom tray impressions

Stock tray impressions

4. 
Thelightbodymaterialisinjectedfromthefilledsyringe
withinandaroundthetoothpreparation.

Thetrayfilledwithheavybodymaterialisinsertedinthe
mouthandseatedoverthesyringematerial.mouthandseatedoverthesyringematerial.

Thetwomaterialsbondtogetheronsetting.

Mostcommonlyusedwithcustomtray.

6. 
Advantages

Overcomesthepolymerizationshrinkageofthelight
bodymaterial

Marginsduplicatedinlightbody

Disadvantages

Useofcustomtray

Anassistantrequiredformixingthematerial-
tray/syringesimultaneously

Marginsduplicatedinheavybodyincaseofexcess
pressure

7. 
Mediumviscosityofpolyetherandadditionsiliconesused
inastocktray

Onlyonemixismade,partofthematerialplacedinthe
trayandanotherportionplacedinthesyringeforinjectiontrayandanotherportionplacedinthesyringeforinjection
inthecavitypreparationoronpreparedteeth

Successofthistechniquedependsonthe pseudoplastic
behaviorofthesetwomaterials

8. 
Advantages

Reduced wastage of the material

Less time consumption

Avoids the time involved in fabrication of custom tray

Disadvantages

Relatively high viscosity and reduced flow of the
monophasematerials, makes their injection onto the
preparation more difficult to control -increased incidence
of surface voids

10. 
Lightbodymaterialsyringedontothepreparation
whiletheputtymaterialloadedinastocktrayis
simultaneouslyinsertedintothemouth.simultaneouslyinsertedintothemouth.

12. 
Advantages

Reducedchairsidetime

Disadvantages

Absolutelackofcontrolinthebulkofwash
material.

Bymixingputty,syringematerialsimultaneously,

Bymixingputty,syringematerialsimultaneously,
settingdistortionofputtyincludedinoverall
distortionofimpression.

Possibilityofmarginsduplicatedinputtymedium

Tendencyofbubblestobeformedandoccludedin
thesetimpression

13. 
Pre-operativeputtyimpressionismadeintraorally

Intheareawheretheteetharetobeprepared
impressionmaterialisremovedorchannelsprepared
usingputtycutterinstrumentusingputtycutterinstrument

Theimpressionisthenrelinedwithlowviscosity
material

15. 
Advantages

Impression can be captured with the wash materials

Disadvantages

To confine the wash material to area of relieved impression

If entire area is washed -creates hydraulic displacement of

If entire area is washed -creates hydraulic displacement of
putty impression resulting in smaller dies

16. 
2mmthicknesswaxspacerispreparedonadiagnostic
cast,occlusalstopsareprovidedonnon-functional
cusps

Aputtyimpressionismadewithastocktrayresulting
inaputtycustomtraywith2mmspaceforthewashinaputtycustomtraywith2mmspaceforthewash
material

Puttycustomtrayisthenwashedwithlightbody
material

18. 
Advantages

Washstagecarriedoutaftertheputtyhassetand
contracted.

Controlledwashbulkcompensatesforthiscontraction
withminimaldimensionalchange.

Disadvantages

Extrachairsidetime

Extramaterial

19. 
Thistechniquewasusedtosalvageanimpressionof
multiplepreparationswhentherewereonlyvague
marginsononeortwopreparationsthatwerenot
adequatelyreplicatedintheimpression.adequatelyreplicatedintheimpression.

Coppertubeispreparedthatextends1mmbeyond
thefinishline.

21. 
Topone-thirdofcoppertubefilledwithimpression
compoundandsealedonthepreparation.

2mmofcompoundwasremovedfromtheimpressed
occlusalsurfacefortherubberbase.

Disadvantages

Disadvantages

Cancausedamagetotheattachmentapparatus

Timeconsuming

22. 
Thistechniquecapturesthepreparedteeth,theopposing
archandtheocclusalarticulationinmaximumarchandtheocclusalarticulationinmaximum
intercuspation(MIP)simultaneously.

23. 
Indications

Usedwithamaximumoftwopreparedteeth

Unpreparedstopsanteriorandposteriortotheprepared
teethshouldbepresent

Usedonlywithpatientsthathaveexistinganteriorguidance

Usedonlywithpatientsthathaveexistinganteriorguidance

Mustbeabletoclosecompletelyinmaximumintercuspation
positionwiththeimpressiontrayinplace

24. 
Contraindications

Presenceofthirdmolars

Rapidlyascendingramus

Excesssofttissuedistaltothemolars

25. 
Advantages

AccuraterecordingoftheMIP

Eliminatesanymandibularflexurethatmightbe
associatedwithopening

Disadvantages

Disadvantages

Complicatedlaboratoryprocedure

26. 
Impressionsofmultiplepreparedteethduetoinherent
limitsinworkingtimeanddifficultiesmaintaining
moisturecontrol

Archisbrokendownintosegmentsoftwopreparedteeth
Customtraypreparedforeachsegmentwith1mmofwax

Customtraypreparedforeachsegmentwith1mmofwax
relief,traysshouldextend3mmpastthegingivalmargin

27. 
Lowviscositymaterialisloadedintothesyringeas
wellasthesegmentaltray,andthenanimpression
made.

Procedurerepeatedwitheachsegment.

Finallyanoverimpressionismadeusingastocktray.
UsesUses

Whenmoisturecontrolisdifficultinspecificpatients.

Whenmakingsimultaneouslyimpressionsofimplants
andpreparedteeth.

28. 
Indicatedwhenmultipledowelcoresarerequiredorwhen
radicularattachmentsaretobeused

A25gaugelocalanaestheticneedles-venttoallowairto
escapeastheimpressionmaterialisinjectedintothecanal
space

Needleisgraduallyremovedwhilethelowviscosity
materialsisinjectedintothecanal

Plasticimpressiondowelcoatedwithadhesiveisinserted
intothecanal

Procedureisrepeatedwithmultipledowelsandfinallyan
overimpressionismade

30. 
Elastomersarestrongenoughtoreproduceapinhole
withouttearing

Howevertoovoidbubbles

Cementtube:thetubefilledwithimpressionmaterialis
squeezedintoeachpinhole,makingsurenoairistrappedby
insertingandremovinganexplorerintothematerialinsertingandremovinganexplorerintothematerial

Lentulospirals:rotatedslowlyalongthesidesofthepin-
hole

Reversiblehydrocolloid-specialnylonbristlesareused
toregisterthepinhole

31. 
Itistheelectrodepositionofmetals(silver,copper)on
thesurfaceoftheimpressiontoimprovetheabrasion
resistanceofgypsum

Advantages

Increasedhardnessofthedie

Excellentabrasionresistance
Dieissostrongthatwaxpatterns&goldcastingscanbe

Dieissostrongthatwaxpatterns&goldcastingscanbe
burnishedwithlittledistortionordamagetothedie

Disadvantages

Toxicityofcyanidebaths

Timerequiredtopreparethedie

Expenseoflaborandmaterials

Limitedcontrolofdieaccuracy

32. DISINFECTIONOFIMPRESSION

Thedentalimpressionisoneofthewaysbywhich
pathogenscanleavetheoperatoryandspreadtheirrisk
abroad.
Theimpressionmustberenderedharmlessbefore

Theimpressionmustberenderedharmlessbefore
beingpassedontoanotherpersonwhowillworkwithit
orwiththegypsumcastmadefromit,outsidethedental
operatory.

33. 
Chemicaldisinfectantsusedforthispurpose

Chlorinecompounds

Syntheticphenoliccompounds

Glutaraldehydes

Iodophors
Phenolic/alcoholiccombinations

Phenolic/alcoholiccombinations

34. Material Material Method Method Disinfectant Disinfectant

AlginateAlginate

AgarAgar--agaragar
Disinfectant with shortDisinfectant with short--
term exposure time term exposure time
(<10min )(<10min )
Chlorine compounds or Chlorine compounds or
iodophorsiodophors

PolysulfidePolysulfide

Silicone Silicone
Immersion time should Immersion time should
not exceed the not exceed the
recommended pouring recommended pouring
Glutaraldehydes, Glutaraldehydes,
Chlorine compounds, Chlorine compounds,
iodophors, phenolicsiodophors, phenolics

Silicone Silicone
recommended pouring recommended pouring
timetime
iodophors, phenolicsiodophors, phenolics

Polyether Polyether Disinfectant with shortDisinfectant with short--
term exposure time term exposure time
(<10min )(<10min )
Chlorine compounds or Chlorine compounds or
iodophorsiodophors

35. 
Analternativemethodforthehydrophilicmaterials:

Disinfectantcanbesprayedontheimpression-wrappedin
adisinfectantsoakedpapertowelandplacedinsealed
plasticbagfor10min.

Longimmersiontimemaycausethesurfactantin
hydrophilicPVStoleachoutandrendertheimpression
lesshydrophilic.lesshydrophilic.

36. 
Ultraviolettreatment-effectiveagainstCandida
organisms,andtherewasnoadverseeffectoneither
dimensionalchangeorsurfaceroughnessofimpression
materials

Disadvantages-cannotkillmicroorganismsthatare
shadowedfromtheemission

UVlightunitshouldbedesignedinsuchaway,thatthe
impressionrotatesonthetableandunitsurroundedby
mirror

37. 
Sentwellcleaned(rinsed)andundisinfectedina
biohazard-labeled,heatsealedplasticbag
OROR

Debride,clean(rinse)andadequatelydisinfectit,place
itinasealedtransportbaglabeledwiththeprecautions
taken

39. Theabilitytorecordconsistentlygoodimpressionsis
bothascienceandanart.
Impressiontechniques,methodsandmaterialsare
evolvingandchangingbutunderlyingprinciplesandevolvingandchangingbutunderlyingprinciplesand
fundamentalsremainconstant.
Anidealimpressionmustbeinthemindofthedentist
beforeitcanbeinhishand.Itisthisknowledgeand
experiencethatenablesadentisttocreatedesirableresults

40. 
Philip’s science of Dental Materials –Eleventh Edition.
Anusavice

Restorative Dental Materials -Eleventh Edition. Robert
G. Craig

Fundamentals of Fixed Prosthodontics-Third Edition.
Shillingburg

Contemporary Fixed Prosthodontics-Second Edition.
RoseinsteilArt and Science of Operative Dentistry -
Fourth Edition. Sturdevant