1 / 25

Elastomeric Impression Materials

Elastomeric Impression Materials. Part 1. Dr. Noland Naidoo. Classification. Introduction. R ubberlike elastic impression materials C urrently referred to as elastomers or elastomeric impression materials .

francis
Télécharger la présentation

Elastomeric Impression Materials

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ElastomericImpression Materials Part 1 Dr. Noland Naidoo

  2. Classification

  3. Introduction • Rubberlike elastic impression materials • Currently referred to as elastomers or elastomeric impression materials. • Elastomeric material consists of large molecules or polymers that are joined by a small amount of cross-linking • Cross linking form a three-dimensional network • The amount of cross-linking determines the stiffness and elastic behaviour of the material

  4. Requirements • Accuracy- must reproduce the entire surface upon which the prosthesis to be made will fit • Elasticity- low elastic modulus and high elastic range • Dimensional stability- the way in which accuracy varies with time after recording the impression • Ease of handling • Good tear strength • Non-toxic and non-irritating • Compatible with die and model materials

  5. Classification

  6. Classification • The ADA considers three types of elastomeric material and each type can be further divided into four viscosity classes: • light body • medium body • heavy body • putty

  7. Polysulphides • Supplied in the form of two pastes- a base and a catalyst • Examples: Permlastic(SDS/Kerr), Coe-Flex, Omniflex (GC America) • The base paste consists of: • Polysulphide polymer • Suitable filler (titanium dioxide or lithopone) • Plasticizer ( eg. dibutyl phthalate) • Sulphur – small amount that enhances reaction ( catalyst)

  8. Polysulphides • The catalyst paste: • Lead dioxide • Plasticizer- chlorinated parafin • Approx same amount of filler as in base paste • Oleic or stearic acid- retarders- control the rate of setting

  9. Polysulphides • Must be used with a special tray • Reasonable tear strength and good elastic properties • Unpleasant odor and taste • Work well in the presence of moisture- moderately hydrophilic • Used commonly for crown and bridge impressions • Casts should be poured within 24hrs of impression but not immediately as to allow for full elastic recoil • Reported incidences of allergic reaction to patients sensitive to latex • Impressions made from polysulfide materials should be poured within 30 minutes following removal from the mouth, because in the first hour they undergo 50% of their 24-hour shrinkage.

  10. Polysulphides

  11. Polysulphides

  12. Silicones Condensation silicone impression material • Supplied in a base paste and low viscosity liquid • Examples: Speedex (Coltene/Whaledent), Accoe (GC America) McCabe and Walls, 2008

  13. Silicones Condensation silicone impression material • Setting characteristics more favourable than polysulphide • Setting time shorter and elasticity developed earlier • Very hydrophobic- repelled by water or saliva therefore necessary to dry areas of the mouth for an acurate impression • Adequate tear resistance for most purposes • Models must be poured as soon as possible after impression recordings • The increased use of addition silicones has lead to a gradual decline in the use of addition silicone

  14. Silicones Condensation silicone impression material

  15. SiliconesAddition silicone impression material • Also supplied as two paste • The hydroxyl group from the condensation silicone is replaced by vinyl group • Examples: Extrude, Take 1 (SDS/Kerr), President (Coltene/Whaledent), Express, Imprint II (3M ESPE), Examix, Exaflex(GC America), Reprosil, Aquasil, Hydrosil(Dentsply/Caulk)

  16. SiliconesAddition silicone impression material • Properties are similar to condensation silicones • They have near ideal elasticity with adequate tear resistance and setting characteristics • The use of the light body and putty enables accurate impressions to be recorded • Dimensional stability is greater than condensation silicones • Also inherently hydrophobic therefore a dry field is required during impression recording • Although surface active agents have been added to newer materials to make it less hydrophobic

  17. SiliconesAddition silicone impression material • Handling characteristics similar to condensation silicone • Routinely used for crown and bridge impressions • Preferred to condensation silicones due to its dimensional stability.

  18. SiliconesAddition silicone impression material

  19. SiliconesAddition silicone impression material

  20. Polyethers • Also supplied as two pastes and automix • Examples: Impregum F, Permadyne (3M ESPE), Polyjel • (Dentsply/Caulk) McCabe and Walls, 2008

  21. Polyethers • Tear resistance and elasticity approaching that of silicones • Relatively rigid when set • It is dimensionally stable under relatively low humidity conditions • The set material is hydrophilic and absorbs moisture under high humidity conditions • Can record accurate impression even when perfect moisture control is not achieved

  22. Polyethers • The major disadvantage is its rigidity during its set state- but this is also an advantage , e.g. when taking impressions for implants

  23. Polyethers

  24. Comparison of the properties of elastomeric impression material McCabe and Walls, 2008

  25. End of Part 1

More Related