Elastomeric Impression Materials Overview
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Elastomeric Impression Materials Overview

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Questions and Answers

Which of the following statements accurately describes a property of elastomeric impression materials?

  • They do not generate heat during the setting process.
  • They exhibit high dimensional stability over time.
  • They have high tear strength and flexibility. (correct)
  • They require minimal mixing for optimal performance.

    • What is a common issue associated with polysulphide elastomers during the setting process?

  • Rapid setting time leading to poor impression quality.
  • Minimal shrinkage during the curing process.
  • Messy handling due to lead dioxide by-products. (correct)
  • Increased viscosity making application difficult.

    • How does the setting reaction of elastomers primarily occur?

  • Via condensation polymerization with the release of ethyl alcohol. (correct)
  • Using thermal polymerization requiring an external heat source.
  • Through mechanical polymerization via vigorous mixing.
  • Through addition polymerization with minimal by-products.

    • Which viscosity class of elastomeric impression material is typically available only in silicones?

    <p>Putty (Extra heavy)</p> Signup and view all the answers

    What clinical significance do elastomers hold in dentistry?

    <p>They require custom trays to accommodate their thickness for proper application.</p> Signup and view all the answers

    Which elastomeric impression material has the highest stiffness?

    <p>Polyether</p> Signup and view all the answers

    What is the recommended time frame to pour models and dies for polysulfide and condensation silicones to achieve the greatest accuracy?

    <p>Within 30 minutes</p> Signup and view all the answers

    Which of the following factors can cause dimensional change in elastomeric impressions?

    <p>Increased ambient humidity</p> Signup and view all the answers

    How does rapid removal of impression materials affect tear strength?

    <p>Increases tear strength</p> Signup and view all the answers

    Which impression material has the best wettability?

    <p>Polyether</p> Signup and view all the answers

    Which mixing technique utilizes a self-contained system to achieve a homogeneous mixture?

    <p>Static automixing</p> Signup and view all the answers

    What is the effect of imbibition on elastomeric impressions?

    <p>It leads to expansion</p> Signup and view all the answers

    What is a significant clinical concern regarding impression stiffness during removal?

    <p>It may lead to exfoliation of loose teeth</p> Signup and view all the answers

    What is a primary disadvantage of hand mixing impression materials?

    <p>It can cause incorporation of air bubbles.</p> Signup and view all the answers

    Which technique uses a single viscosity for the impression material?

    <p>Monophase technique</p> Signup and view all the answers

    What advantage does static automixing provide over hand mixing?

    <p>Less of material waste</p> Signup and view all the answers

    What is a key characteristic of the dynamic mechanical mixing technique?

    <p>It is motor driven for high-speed mixing.</p> Signup and view all the answers

    In the multiple mix technique, what is a major disadvantage?

    <p>Higher viscosity material may displace lower viscosity material.</p> Signup and view all the answers

    What type of impression materials can be used in the putty-wash technique?

    <p>Combination of light and putty materials</p> Signup and view all the answers

    What is a common property of elastomers that is critical for their use in dental impressions?

    <p>High tear strength</p> Signup and view all the answers

    Which technique allows for the simultaneous use of two viscosity materials during an impression?

    <p>Multiple mix technique</p> Signup and view all the answers

    Study Notes

    Elastomeric Impression Materials

    • Polysulfide, Silicones, and Polyethers are the three main types of elastomeric impression materials.
    • Condensation Silicones are a type of silicone with a condensation polymerization reaction, releasing water as a by-product.
    • Addition Silicones are a type of silicone with an addition polymerization reaction, releasing ethyl alcohol as a by-product.
    • Hydrophobic Materials repel water.
    • Hydrophilic Materials attract water.

    Viscosity Classes

    • Low Viscosity (light body) is used for fine detail capture.
    • Medium Viscosity (regular body) is used for general impressions.
    • High Viscosity (heavy body) is used for supporting the impression.
    • Putty (Extra Heavy) is used for stabilizing the impression in the tray.

    Polysulfide Impression Materials

    • Supplied as two pastes (base & catalyst) in collapsible tubes.
    • Setting Reaction: Condensation polymerization.
    • Exothermic reaction (increase in temperature) during setting.
    • Release of water as a by-product causing dimensional instability.
    • Advantages: High flexibility, high tear strength, long working time, lower cost.
    • Disadvantages: Poor dimensional stability, long setting time, messy due to lead dioxide, requires custom or special trays.

    Silicone Impression Materials

    • Condensation Silicones:

      • Supplied as two pastes (base & catalyst) in collapsible tubes.
      • Setting reaction is condensation polymerization.
      • Clinical Significance:
        • Pseudoplasticity: Material flows easily when syringed and solidifies into a stable impression.
        • Advantages:
          • High flexibility and tear strength.
          • Good detail reproduction.
      • Disadvantages:
        • Dimensional instability.
        • Limited shelf life.
        • Requires a special tray.

    • Addition Silicones:

      • Available in one or two paste systems.
      • Clinical Significance:
        • Pseudoplasticity: Allows for one-step materials (monophase) with improved adaptation in the mouth.
      • Advantages:
        • Excellent dimensional stability.
        • Shorter setting time.
        • Fewer air bubbles.
      • Disadvantages:
        • Higher cost.
        • May need a special tray.

    Polyether Impression Materials

    • Supplied as two pastes (base & catalyst) in collapsible tubes.
    • Setting Reaction: Addition polymerization.
    • Advantages:
      • Excellent dimensional stability.
      • High rigidity and tear strength.
      • Good detail reproduction.
      • High wettability (adheres to wet surfaces).
      • High accuracy.
      • Can be poured up to one week after the impression.
    • Disadvantages:
      • May be difficult to remove from the mouth.
      • Requires special trays due to stiffness.

    Properties of Rubber Base Impression Materials

    • Flexibility and Stiffness:
      • Polysulfide is the least stiff (most flexible).
      • Polyether is the stiffest.
      • Clinical Significance:
        • Impression removal: Stiffness can affect loose teeth.
    • Dimensional Stability:
      • Influenced by polymerization shrinkage, loss of by-products, thermal contraction, and imbibition (absorption of water).
      • Condensation Silicone and Polysulfide should be poured within 30 minutes for optimal accuracy.
      • Addition Silicone and Polyether can be poured up to 24 hours or even a week.
    • Tear Strength:
      • Affected by the speed of removal (faster removal increases tear strength).
    • Detail Reproduction:
      • All elastomers can reproduce fine detail and are compatible with gypsum products.
    • Wettability:
      • Affected by the presence of surfactants.
      • Polyether has the best wettability.
    • Shelf Life:
      • Store tightly closed in a cool, dry environment.

    Manipulation of Elastomeric Impression Materials

    • Mixing Systems:
      • Hand Mixing:
        • Risk of incorporating air bubbles leading to voids in the impression.
      • Static Automixing:
        • Less mixing time.
        • Fewer bubbles.
        • Less waste.
        • Not suitable for putty consistency.
      • Dynamic Mechanical Mixing:
        • High speed and accuracy.
        • Easy to use.
        • Waste of material.
    • Impression Techniques:
      • Multiple Mix Technique (Dual-Viscosity):
        • Two viscosities (light and heavy) used simultaneously.
      • Monophase Technique (Single Viscosity):
        • One medium viscosity material.
        • Uses pseudoplasticity to adapt to the preparation.
      • Putty-Wash Technique:
        • Two-Stage (Reline): Light and putty consistency used in two stages.
        • Single-Stage: Light and putty consistency used in one stage.

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    Related Documents

    Elastomeric Impression Material Part II PDF

    Description

    This quiz explores the various types of elastomeric impression materials, including polysulfides, silicones, and polyethers. It covers aspects such as viscosity classes and the chemical reactions involved in different materials. Test your knowledge on the properties and uses of these essential dental materials.

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