Zinc Polycarboxylate Cement Composition and Mixing
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Questions and Answers

What is a key advantage of polycarboxylate cement regarding its biological properties?

  • It has low tensile strength.
  • It completely neutralizes acidity.
  • It causes irritation to the pulp.
  • It has a soothing effect on the pulp. (correct)

    • Which statement accurately describes a disadvantage of polycarboxylate cement?

  • It has a longer working time compared to other cements.
  • It has high solubility in oral fluids.
  • It requires complex mixing techniques.
  • It exhibits lower compressive strength than zinc phosphate. (correct)

    • Which property of polycarboxylate cement aids in achieving good adhesion to tooth structure?

  • High irritancy.
  • High film thickness.
  • Low viscosity.
  • Low solubility. (correct)

    • What effect does water have on the working time of water-based cements?

    <p>It increases the setting time significantly.</p> Signup and view all the answers

    What should be done to extend the working time of zinc phosphate cement?

    <p>Add a special retarder during preparation.</p> Signup and view all the answers

    What is the working time for polycarboxylate cement?

    <p>2.5 min</p> Signup and view all the answers

    What effect does time have on the viscosity of polycarboxylate cement?

    <p>Increases with time</p> Signup and view all the answers

    Which method helps in bonding polycarboxylate cement to restorations?

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

    What is the recommended thickness for the film of polycarboxylate cement?

    <p>25µ</p> Signup and view all the answers

    How is the chemical bond of polycarboxylate cement to tooth structure primarily established?

    <p>With carboxyl groups</p> Signup and view all the answers

    What should be done to the tooth structure before applying polycarboxylate cement?

    <p>Condition with 10% polyacrylic acid</p> Signup and view all the answers

    Which property of polycarboxylate cement is lower compared to zinc phosphate cement?

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

    What is a clinical consideration when using polycarboxylate cement?

    <p>Apply shearing stress during spatulation</p> Signup and view all the answers

    What is the primary component of the powder used in zinc polycarboxylate cement?

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

    Which acid is used in the liquid composition of zinc polycarboxylate cement to prevent gelation on standing?

    <p>Itaconic acid</p> Signup and view all the answers

    Which is NOT an application of zinc polycarboxylate cement?

    <p>Permanent restorations</p> Signup and view all the answers

    What is the purpose of adding tartaric acid to the liquid composition of zinc polycarboxylate cement?

    <p>Modify working time</p> Signup and view all the answers

    Which of the following best describes the microstructure of set polycarboxylate cement?

    <p>Amorphous gel matrix with unreacted ZnO</p> Signup and view all the answers

    What are the presentations of zinc polycarboxylate cement?

    <p>Powder &amp; distilled water; Powder &amp; liquid</p> Signup and view all the answers

    What role do residual glass particles play in the structure of zinc polycarboxylate cement?

    <p>Contribute to strength</p> Signup and view all the answers

    Which component enhances the manipulation of zinc polycarboxylate cement during application?

    <p>Polyacrylic acid</p> Signup and view all the answers

    Study Notes

    Zinc Polycarboxylate Cement

    • Composition:
      • Powder:
        • 90% Zinc Oxide (ZnO)
        • 8.2% Magnesium Oxide (MgO)
        • 1.4% Silicon dioxide (SiO2)
        • trace amounts of Bismuth Oxide (Bi2O3)
        • trace amounts of Stannous Fluoride (SnF2) for strength modification and manipulation enhancement.
      • Liquid:
        • 32-40% polyacrylic acid
        • Itaconic acid to prevent gelation on standing
        • Tartaric acid to modify working and setting time
        • Water
    • Setting Reaction: Zinc oxide reacts with polyacrylic acid (PAA) in the presence of water, forming zinc polycarboxylate. This results in a gel structure containing unreacted ZnO powder.
    • Mixing Procedure and Precautions:
      • Mix the powder and liquid on a cool, dry, non-porous surface.
      • Ensure proper dispensing and folding of the powder to avoid air inclusions.
      • Adequate mixing is crucial to ensure proper consistency and setting characteristics.
    • Mixing Time: 30 seconds
    • Working Time: 2.5 minutes
    • Setting Time: 6 minutes
    • Viscosity:
      • High initial viscosity
      • Reduced with pressure during mixing and seating.
      • Lower film thickness than zinc phosphate cement (approx. 25µ).
      • Increased viscosity over time.
    • Clinical Considerations:
      • Apply shearing stress (mixing) to ensure proper consistency.
      • Apply vibration and pressure when seating the restoration.
    • Bonding:
      • To Tooth Structure:
        • Chemical bond (adhesion) to calcium in enamel and dentin.
        • Adhesion depends on the presence of unreacted carboxyl groups.
        • Apply cement while it is shiny (before gloss loss) to ensure strong bonding.
        • Clean and dry tooth structure before applying the cement.
        • Conditioning of dentin with 10% polyacrylic acid is essential for removal of the smear layer.
      • To Restorations:
        • Chemical bond to stainless steel and non-precious alloys due to their active surface chemistry.
        • Mechanical bond to gold alloys using surface irregularities.
        • Tin plating can create a chemical bond to gold alloys.
    • Solubility: Soluble in oral fluids, solubility increases with lower powder/liquid ratios.
    • Mechanical Properties:
      • Compressive strength is lower than zinc phosphate cement.
      • Tensile strength is higher than zinc phosphate cement, making it less brittle.
      • Modulus of elasticity is lower than zinc phosphate cement, making it less stiff.
    • Biological Properties:
      • Biologically compatible and has a bland effect on the pulp.
      • Rapid neutralization, large molecule size, and immediate bonding contribute to its biocompatibility.
      • When used in deep cavities near the pulp, a calcium hydroxide liner is recommended for added protection.

    Applications

    • Cementation:
      • Cast restorations
      • Orthodontic brackets
    • Bases and Liners: Under other restorations
    • Temporary restorations

    Advantages:

    • Low irritancy
    • Adhesion to tooth structure
    • Easy manipulation
    • Higher tensile strength than zinc phosphate cement.
    • Low solubility
    • Low film thickness

    Disadvantages:

    • Accurate proportioning of materials is crucial for successful setting.
    • Short working time.
    • Lower compressive strength than zinc phosphate cement.
    • Higher viscosity than zinc phosphate cement, which can be controlled.

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    Related Documents

    Zinc Polycarboxylate Cement Lecture Notes PDF

    Description

    Explore the intricacies of Zinc Polycarboxylate Cement, including its composition, setting reactions, and proper mixing procedures. Learn about the importance of each component and precautions for optimal results. This quiz is essential for understanding dental materials in clinical applications.

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