Types of impressions: Previous Final

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Imprints, their classification, method of receipt. Classification of materials of imprint. Clinical, physical and chemical descriptions of materials for imprint. Impression is a negative (reverse) reflection of any organ of the dentomaxillar system: teeth, alveolar sprout or part, palate, nose, - PowerPoint PPT Presentation

Transcript of Types of impressions: Previous Final

  • Imprints, their classification, method of receipt. Classification of materials of imprint. Clinical, physical and chemical descriptions of materials for imprint

  • Impression is a negative (reverse) reflection of any organ of the dentomaxillar system: teeth, alveolar sprout or part, palate, nose, ear and others like that.

    Impression is a negative (reverse) reflection of hard and soft tissues, placed in the area of dental prosthesis and its borders which Is being taken by means of the special impression materials

  • Types of impressions:PreviousFinal

  • Final impressions:AnatomicalFunctional

  • Types of impressionsSingle layer

    Double layer

    Combined

  • Types of impressionsAnatomical (orientation) take with standard or individual tray in the state of calmness of tissues of prosthetic bed and tissues, which are placed on a border with them.Functional - take with individual tray by means of the special functional tests, in the case of making of removable constructions of dentures :compression - in the case of pressing of buffer areas of prosthetic bed, by masticatory pressure or by the hand of doctor; decompression - in the case of minimum pressure on the tissues of prosthetic bed

  • Double layer an exact reflection of gingival edge is taken by means of impression materials of the same group (previous layer + correction layer)Combined is taken by means of impression materials of different groups (previous layer + correction layer)Occlusalfor taking impression in position of central occlusion

  • Impression trays

    Standard: made factory- On maxillae different sizes- On mandible different sizesIndividual: made in dental laboratoryBy material:plasticmetallicwaxenPresence of retentin pointsperforatedunperforated

  • Impression trays for taking impression at the same time

  • Placing of impression tray in oral cavity

  • Impression of maxillae

  • Double layer impression

  • Impression MaterialsNon-elasticElasticAqueous hydrocolloidsAgarAlginateNon-aqueous elastomersPolysulfideSiliconesCondensationAdditionPolyether

  • IndicationsDiagnostic castspreliminaryopposing Indirect reconstructionfixedremovableBite registration

  • Elastomeric Impression MaterialsViscoelasticphysical properties varyrate of loadingRapidly removedecreases permanent deformationchains recoil from a recoverable distanceincreases tear strength

  • Impression MaterialsNon-elasticElasticAqueous HydrocolloidsNon-aqueous ElastomersCondensationAdditionAgar (reversible)Alginate (irreversible)

  • Aqueous HydrocolloidsColloidal suspensionschains align to form fibrilstraps water in intersticesTwo formssolviscous liquidgelelastic solidPlaced intra-orally as solconverts to gelthermal or chemical process

  • Aqueous HydrocolloidsSemi-permeable membranespoor dimensional stabilityEvaporationSyneresisfibril cross linking continuescontracts with timeexudes waterImbibitionwater absorptionswells

  • Reversible Hydrocolloid (Agar)Indicationscrown and bridgehigh accuracyExampleSlate Hydrocolloid (Van R)

  • CompositionAgarcomplex polysaccharideseaweedgelling agentBoraxstrengthPotassium sulfateimproves gypsum surfaceWater (85%)

  • ManipulationGel in tubessyringe and tray material

  • Manipulation3-chamber conditioning unit(1) liquefy at 100C for 10 minutesconverts gel to sol(2) store at 65Cplace in tray(3) temper at 46C for 3 minutesseat traycool with water at 13C for 3 minutesconverts sol to gel

  • AdvantagesDimensionally accurateHydrophilicdisplaces moisture, blood, fluidsInexpensiveafter initial equipmentNo custom tray or adhesivesPleasant flavorNo mixing required

  • DisadvantagesInitial expensespecial equipmentMaterial must be prepared in advancedTears easilyDimensionally unstableMust be poured immediatelyCan only be used for a single castDifficult to disinfect

  • Irreversible Hydrocolloid (Alginate)Most widely used impression material Indicationsstudy modelsremovable fixed partial denturesframeworkExamplesJeltrate (Dentsply/Caulk)Coe Alginate (GC America)

  • CompositionSodium alginatesalt of alginic acidmucous extraction of seaweed (algae)Calcium sulfatereactorSodium phosphateretarderFillerPotassium fluorideimproves gypsum surface

  • ManipulationWeigh powderPowder added to waterrubber bowlvacuum mixerMixed for 45 sec to 1 minPlace trayRemove 2 to 3 minutes after gelation (loss of tackiness)

  • AdvantagesInexpensiveEasy to useHydrophilicdisplace moisture, blood, fluidsStock trays

  • DisadvantagesTears easilyDimensionally unstableimmediate pour single castLower detail reproductionunacceptable for fixed prosHigh permanent deformationDifficult to disinfect

  • Non-Aqueous ElastomersSynthetic rubbersmimic natural rubberscarce during World War IILarge polymerssome chain lengtheningprimarily cross-linking Viscosity classeslow, medium, high, puttymonophasic

  • PolysulfideFirst dental elastomersIndicationscomplete dentureremovable fixed partial denturetissuecrown and bridgeExamplesPermlastic (Kerr)Omni-Flex (GC America)

  • CompositionBasepolysulfide polymersfillersplasticizersCatalystlead dioxide (or copper)fillersBy-productwater

  • --SH HS---------------------SHHS-- S H O = Pb = OHS-S-S---------------S-S- S S + 3PbO + H2OPolysulfide Reaction

  • ManipulationAdhesive to trayUniform layer custom trayEqual lengths of pastesMix thoroughlywithin one minuteSetting time 8 12 minutesPour within 1 hour

  • AdvantagesLower costcompared to silicones and polyethersLong working timeHigh tear strengthHigh flexibilityGood detail reproduction

  • DisadvantagesPoor dimensional stabilitywater by-productpour within one hoursingle pourCustom traysMessypaste-paste mixbad odormay stain clothingLong setting time

  • Condensation SiliconeIndicationscomplete denturescrown and bridgeExamplesSpeedex (Coltene/Whaledent)Primasil (TISS Dental)

  • CompositionBasepoly(dimethylsiloxane)tetraethylorthosilicatefillerCatalystmetal organic esterBy-productethyl alcoholPhillips 1996

  • Condensation Silicone Reactionmetal organic ester ethanol

  • ManipulationMix thoroughlypaste - pastepaste - liquidPutty-wash techniquereduces effect of polymerization shrinkagestock trayputty placedthin plastic sheet spacerpreliminary impressionintraoral custom trayinject wash material

  • AdvantagesBetter elastic propertiesClean, pleasantStock trayputty-washGood working and setting time

  • Disadvantages

    Poor dimensional stabilityhigh shrinkagepolymerizationevaporation of ethanol pour immediatelywithin 30 minutesHydrophobicpoor wettability

  • Addition SiliconesAKA: Vinyl polysiloxaneIndicationscrown and bridgedenturebite registrationExamplesExtrude (Kerr)Express (3M/ESPE)Aquasil (Dentsply Caulk)Genie (Sultan Chemists)Virtual (Ivoclar Vivadent)

  • CompositionImprovement over condensation siliconesno by-productFirst pastevinyl poly(dimethylsiloxane) prepolymerSecond pastesiloxane prepolymerCatalystchloroplatinic acidPhillips 1996

  • Chloroplatinic Acid CatalystAddition Silicone Reaction

  • ManipulationAdhesive to tray Double mixcustom trayheavy-bodylight-body to prepPutty-washstock tray

  • AdvantagesHighly accurateHigh dimensional stabilitypour up to one weekStock or custom traysMultiple castsEasy to mixPleasant odor

  • DisadvantagesExpensiveSulfur inhibits set latex glovesferric and Al sulfate retraction solutionPumice teeth before impressingShort working timeLower tear strengthPossible hydrogen gas releasebubbles on diepalladium added to absorb

  • Addition SiliconesSurfactants addedreduce contact angleimprovedcastabilitygypsumwettabilitystill need dry field clinically

  • PolyetherIndicationscrown and bridgebite registrationExamplesImpregum F (3M/ESPE)Permadyne (3M/ESPE)Pentamix (3M/ESPE)P2 (Heraeus Kulzer)Polygel (Dentsply Caulk)

  • Basedifunctional epimine-terminated prepolymerfillersplasticizersCatalystaromatic sulfonic acid esterfillersCationic polymerizationring opening and chain extension

    Composition

  • Polyether Reactioncatalystbasering opening

  • ManipulationAdhesive to traystock or custom trayvery stiffPaste-paste mixAuto-mixinghand-heldlow viscositymechanical dispenserhigh viscosity

  • AdvantagesHighly accurateGood dimensional stabilityStock or dual-arch traysGood surface detailPour within one weekkept dryMultiple castsGood wettability

  • DisadvantagesExpensiveShort working timeRigiddifficult to remove from undercutsBitter tasteLow tear strengthAbsorbs waterchanges dimension

  • Impression Material Usage*Civilian General DentistsCrown & Bridgevinylpolysiloxane81%alginate38%polyether28%Inlays and Onlaysvinylpolysiloxane71%polyether22%alginate20%

  • Impression Material Usage*Civilian General DentistsComplete denturesalginate58%vinylpolysiloxane55%polyether27%Partial denturesalginate78%vinylpolysiloxane43%polyether15%

  • Handling Properties

    AgarAlginatePolysulfideCondensation SiliconeAddition SiliconePolyetherPreparationBoil, temper, storePowder, water2 pastes2 pastes or paste/liquid2 pastes2 pastesEase of UseTechnique sensitiveGoodFairFairExcellentGoodPatient ReactionThermal ShockPleasant, cleanUnpleasant, stainsPleasant, cleanPleasantUnpleasant cleanEase of removalVery easyVery easyEasyModerateModerateModerate to difficultDisinfectionPoorPoorFairFairExcellentFair

  • Handling Properties

    AgarAlginatePolysulfideCondensation SiliconeAddition SiliconePolyetherWorking Time (min)7 152.55