Polysulphide Impression Material in Dentistry
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Questions and Answers

What is the purpose of sulfur in the accelerator paste of polysulphide impression material?

  • To increase the setting time
  • To promote polymerization reaction (correct)
  • To reduce the viscosity of the material
  • To improve the flexibility of the material

    • What is the main advantage of using polysulphide impression material for impressions of crowns and bridges?

  • It has a high tear strength
  • It can be used with stock trays
  • It is more accurate than alginate (correct)
  • It has a long working time

    • What is a disadvantage of polysulphide impression material?

  • It is expensive to use
  • It has a short working time
  • It has an offensive odor and taste (correct)
  • It has a low tear strength

    • What is the recommended way to mix polysulphide impression material?

    <p>Mix the two pastes with a spatula in a swirling and stropping motion</p> Signup and view all the answers

    What property of polysulphide impression material makes it suitable for full denture impressions?

    <p>High flexibility</p> Signup and view all the answers

    Why should the tissue be thoroughly dry when using polysulphide impression material?

    <p>Because the material is hydrophobic</p> Signup and view all the answers

    What is an advantage of polysulphide impression material over alginate?

    <p>It is more accurate</p> Signup and view all the answers

    What can be done to polysulphide impression material to improve its dimensional stability?

    <p>Electroplate it with copper</p> Signup and view all the answers

    Which of the following factors can inhibit the setting time of addition silicone (AS)?

    <p>All of the above</p> Signup and view all the answers

    Which of the following is NOT an advantage of silicone elastomeric impression materials?

    <p>Low cost</p> Signup and view all the answers

    Which of the following is a disadvantage of addition silicone (AS)?

    <p>Hydrogen gas release during setting</p> Signup and view all the answers

    Which of the following properties refers to the resistance to fracture of an elastomeric material?

    <p>Tear strength</p> Signup and view all the answers

    Which of the following is an appropriate disinfectant for polysulfide and silicone elastomeric impression materials?

    <p>All of the above</p> Signup and view all the answers

    Which of the following is an alternative name for addition silicone?

    <p>Vinyl polysiloxane</p> Signup and view all the answers

    Which elastomeric impression material exhibits the highest dimensional stability?

    <p>Addition silicone</p> Signup and view all the answers

    Which of the following is a factor affecting the dimensional stability of elastomeric impression materials (EMIMs)?

    <p>All of the above</p> Signup and view all the answers

    What is a characteristic of polyether impression material?

    <p>It provides elastic recovery with minimal distortion.</p> Signup and view all the answers

    Which statement is true regarding addition silicone materials?

    <p>They are known for their excellent dimensional stability.</p> Signup and view all the answers

    What is a common property of elastomeric impression materials?

    <p>They can undergo elastic recovery after deformation.</p> Signup and view all the answers

    What is the ideal manipulation time for elastomeric impression materials after mixing?

    <p>Within the first three minutes of mixing.</p> Signup and view all the answers

    Which type of silicone is known for curing through a condensation reaction?

    <p>Condensation silicone.</p> Signup and view all the answers

    What effect does filler content have on the shrinkage of elastomeric impression materials?

    <p>More filler content results in decreased shrinkage.</p> Signup and view all the answers

    What is the first elastomeric impression material commonly used in dentistry?

    <p>Polysulphide.</p> Signup and view all the answers

    Which statement accurately describes the stages of polymerization in elastomeric impression materials?

    <p>Final set progresses to a solid rubbery mass.</p> Signup and view all the answers

    Study Notes

    Composition of Accelerator Paste

    • Contains lead dioxide, dibutyl phthalate, magnesium stearate, and sulfur for polymerization.

    Uses of Polysulphide Impression Material

    • Ideal for impressions of crowns and bridges with a light-bodied injected material.
    • Heavy-bodied material used in trays optimizes accuracy.
    • Custom trays increase the precision of dental impressions.
    • Light and medium-bodied materials are used for full denture impressions.

    Properties of Polysulphide

    • Offers greater accuracy than alginate but less than other elastomeric materials.
    • Excellent detail reproduction and lowest viscosity among elastomers.
    • High tear strength and hydrophobic; requires dry tissues for application.
    • Notable for an unpleasant odor and the longest working time of 4-6 minutes.
    • Working and setting times are influenced by heat and humidity.
    • Susceptible to distortion from water loss through evaporation.
    • Provides good flexibility and elastic recovery; can be electroplated with copper.

    Advantages and Disadvantages of Polysulphide

    • Advantages:
      • More accurate than alginate; long working time (4-7 minutes).
      • High tear resistance and long shelf life.
      • Cost-effective and demonstrates high flexibility.
    • Disadvantages:
      • Offensive odor and taste; needs immediate pouring with dental stone.
      • Stains clothing and can experience significant distortion due to water loss.
      • Longer setting time (7-10 minutes) and not as accurate as other elastomeric materials.

    Mixing Polysulphide Impression

    • Equal lengths of two pastes dispensed and mixed on a paper pad until homogeneous.
    • Components include divinyl polysiloxane, inert oils, fillers, platinum salt, palladium, and retarders.

    Properties of Addition Silicone

    • Highest dimensional stability among elastomers.
    • Good tear strength with excellent surface detail reproduction.
    • Exhibits the lowest curing shrinkage and lowest permanent distortion.
    • Can be electroplated with copper and silver.

    Advantages and Disadvantages of Addition Silicone

    • Advantages:
      • Adequate strength, high accuracy, and short setting time.
      • High dimensional stability with minimal distortion.
    • Disadvantages:
      • Hydrogen gas generation may affect dimensional stability.
      • More expensive and hydrophobic.

    Factors Affecting Setting Time of Addition Silicone

    • Sulfur contamination from latex gloves can inhibit setting.
    • Materials used in gingival retraction cord, such as aluminum sulfate.
    • Residues from acrylics, methacrylates, and petroleum jelly can interfere with the reaction.

    Disinfection Methods for Elastomers

    • Polysulphide and silicones may be disinfected by immersion.
    • Recommended exposure time should not exceed 30 minutes; suitable disinfectants include glutaraldehyde, chlorine compounds, iodophors, and phenolics.
    • Polyether should be immersed with caution; short-term exposure minimizes distortion.

    Dimensional Changes in Elastomeric Impression Materials

    • Curing shrinkage and incomplete elastic recovery are key factors.
    • Filler content affects shrinkage—more fillers result in less shrinkage.
    • Loss of water (notably in polyether) and thermal contraction impact dimensional stability.
    • Timing of pouring impressions also influences the outcome.

    Types of Elastomeric Materials

    • Commonly used elastomeric materials in dental practice include polysulphide, polyether, silicone, and polysiloxane (polyvinyl siloxane).

    Curing Process of Elastomeric Impression Material

    • Polymerization begins upon contact of base and catalyst, proceeding through three stages:
      • Initial set: Paste stiffens without elasticity.
      • Final set: Paste becomes elastic, evolving into a solid rubbery mass.
      • Final cure: Occurs within 1 to 24 hours.

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    Description

    This quiz covers the composition and use of polysulphide impression material in dentistry, including its application in crowns and bridges.

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