elastomeric imp .mat

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elastomeric imp .mat

  1. 1. Elastomeric impression materialsDone byDr: Hind NihadSupervisor : Dr. Ali Dr.Yasir
  2. 2. Elastomeric impression materials• These are basically synthetic rubber based materials which wereinitially called as Rubber Impression materials but currently they areknown as Non aqueous Elastomeric Impression materials• A material that is used when an extremely accurate impression isessential. The term elastomeric means having elastic or rubberlikequalities.•
  3. 3. Classification of Elastomeric impression materials:• Till now the Elastomeric impression materials are devided into3types based on the material used• 1-polysulfied• 2-polyether• 3-silicone - Addition -condensation•
  4. 4. Polysulfide Impression MaterialThese materials are also known as thiokol rubbers as theyare derived from thiolsBase: polysulfide. and an inert filler, such as titaniumdioxide-activator paste :(containing lead dioxide, which gives thedistinctive brown colour, sulphur and dibutyl ordioctylphthalate). Catalysts: Copper hydroxides, zinc peroxide, organichydroperoxide fig (1)
  5. 5. • Indications• –complete denture• –removable & fixed partial denture• Advantages• Good wettability• Good surface detail• Easy to remove• High tear strength• Disadvantages• a long working and setting time (8 to 10 minutes)• High permanent deformation• Unpleasant taste and odour• Must pour within 1 hour• Take care when disinfecting
  6. 6. Manipulation and Technique Considerations for Polysulfide Material -Dispense pastes at the topof the mixing pad. -Mix pastes with the tip ofa spatula to incorporate thematerial first.• Transfer the material tothe fresh surface of the mixing pad. and Thinnen polysulfide film fig (2)
  7. 7. • Impression should be removed quickly after setting-do not rock the tray• The setting process or the polysulphide impression material is highly susceptible to changes in environmental conditions, such as temperature and humidity variation fig (3)
  8. 8. POLYETHER IMPRESION MATERIALComposition:• The polyethers come as two-paste system• Base paste : imine terminated polymer(polyether)• Accelerator paste:Alkyl aromatic sulfonateIndications• –crown and bridge• –bite registration Advantages• 1- Hydrophilic• 2-Good surface detail• 3-Good dimensional accuracy• 4-Good resistance to deformation• 5-Highly acceptable to patient• 6-good dimensional stability fig (4)
  9. 9. Disadvantages:• 1-stiffness requires blocking undercuts Difficult to remove andthus multiple casts can’t be poured• 2-High permanent deformation• 3-Swells in disinfectants or moist environments• 4-low tear strength• 5-Take care when disinfecting• 6-slightly more expensive
  10. 10. Silicones• There are two important groups of silicone impression materials.One group is known as the condensation-cured silicones and the otheras the addition-cured silicones. Both are based on the polydimethylsiloxane polymer but have different end groups, giving rise todifferent curing mechanisms. Syringe tray special tray stock tray fig (5)
  11. 11. CONDENSATION SILICONES• Also known as conventional silicones. These materials are based on apolydimethyl siloxane polymer with hydroxyl terminal groups.Composition:• Base paste : Containing silicone fluid and a filler.• Activator paste: tetra-ethyl silicate (the crosslinking agent).• It is important that the amount of activator paste used is carefullycontrolled. Insufficient TES gives rise to an incomplete cure, leaving amaterial with poor mechanical characteristics, such as high permanentset. Conversely an excess of TES also gives an incomplete cure, leavingmany unreacted ethyl end groups
  12. 12. • Advantages:• .1- Good surface detail (dry surfaces)• 2-Good dimensional accuracy• 3-low permanent deformation• 4-Wide range of viscosities• 5-Easy to disinfect• 6-Highly acceptable to patient Pleasant odor & no staining.Disadvantages:• 1-Hydrophobic• 2-Shrinks on storage• 3-Must pour within 1 hour• 4-low tear strength•
  13. 13. Addition-Cured Silicones• These materials are similar to the condensation-cured silicones, inthat they are also based on a polydimethyl Siloxane polymer;however, in this case the terminal groups are vinyl’s groupThe addition-cured silicones present as a :• Base paste :polyvinyl siloxane, silanol and a filler• Catalyst paste: polyvinyl siloxane, platinum catalyst and a filler. fig (6)
  14. 14. Advantages:• 1-Good surface detail (dry surfaces)• 2-Good dimensional accuracy• 3-Good storage stability• 4-low permanent deformation• 5-Wide range of viscosities• 6-Easy to disinfect• 7-Highly acceptable to patient•• Disadvantages:• 1-Hydrophobic (unless surfactant added)• 2-low tear strength
  15. 15. • Indications• –crown and bridge and implant• –denture• –bite registration CONSISTENCIES Putty The addition-cured silicones - wash fig (7)
  16. 16. • The elastomeric impression materials are available in a range of viscosities, depending on the amount of filler that is incorporated• Polysulphides : heavy, medium and light bodied impression ,paste forms are available, there is no putty version.• Polyethers• These materials are available only in a single viscosity and can be used in a special tray using a single viscosity mix.• CCS & ACS• A wide range of viscosities are available, varying from a putty, to aheavy, a medium and a light bodied material Thus, these materials canalso be used in a wide range of impression techniques.
  17. 17. Mechanical Properties1-Stiffness• The stiffness of the impression material once it has set can be a majorconsideration in the case with which it is removed from undercuts.PS < CCS < ACS < PE2-Permanent Set• Ideally, when the impression is removed from an undercut, the deformationthat results should be totally and immediately recoverable. it is important thatthe elastomeric materials are removed from the mouth by a sharp tug.PS > PE > CCS > ACS3-Tear Strength• The tear strength of the impression material is also important when animpression is taken of the dentate patient.PS > PE > CCS > ACS• too high a tear strength may give rise to difficulties in removing theimpression from the mouth in Cases where the impression material has flowedinto the interdental spaces.
  18. 18. • 4-Reproduction of Surface DetailAll of the elastomeric impression materials are able to reproduce the detailsof the surface very accurately when a low-viscosity material is employed.• the lower the viscosity, the better the reproduction• 5-Dimensional Stability and AccuracyIs affected by the amount of filler present, in that the higher the fillerloading, the smaller the shrinkage• The amount of light bodied material used should always be kept to aminimum.PE =ACS < PS < CCS
  19. 19. MIXING SYSTEMS hand mixing, static Automixing, dynamic mechanical mixing • Hand mixing• hand mixing is with the two putty systems, offered both with condensation and addition silicones. Scoops are supplied by the manufacturer for dispensing, and the putties are most often kneaded with fingers until free from streaks.
  20. 20. Static Automixing fig (8)The base and catalyst are in separate cylinders of theplastic cartridge. The cartridge is placed in a mixing gun containing twoplungers that are advanced by a ratchet mechanism toextrude equal quantities of base and catalyst
  21. 21. • dynamic mechanical mixing• The catalyst and base aresupplied in large plastic bagshoused in a cartridge, which is inserted into the top of the mixing machine.A new, plastic mixing tip is placedon the frontof the machine, and whenthe button is depressed parallel plungers push againstthe collapsible plastic bags, thereby opening the bags and forcing material into the dynamic mixing tip fig (9)
  22. 22. Impression Technique Twin-Mix Technique Two-Stage With Spacer Technique Two-Stage Without Spacer Technique Twin-Mix Technique fig (10)
  23. 23. • 1-The potential problems with this technique are related to the removal of the addition-cured silicones• 2- Another problem that may arise is that the puttymay displace the wash in areas where surface accuracy isdesirable. Two-Stage With Spacer Technique• fig (11)
  24. 24. • more of the wash material is required in thistechnique than in the twin-mix approach, and this meansthat there is more setting shrinkage, as the wash has amuch lower filler content. This is especially the casewith the condensation-cured silicones, which also showmore shrinkage on storage.• Two-Stage Without Spacer Technique The two-stage without spacer technique is inappropriate for addition-cured silicones because the primary impression would be extremely difficult to remove from undercuts, once it has set, due to the high stiffness of the putty
  25. 25. • DISINFECTING IMPRESSIONSFor addition silicone (hydrophobic) soak sodium hypochlorite(1:10concentration) for 3 minutes Polyether materials cannot be immersed in disinfectants due topotential for absorption and distortion only spray
  26. 26. Thank you

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