Impression Materials in Dentistry
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Questions and Answers

What is a disadvantage of using the moist heat method?

  • It can lead to excessive shrinkage. (correct)
  • It does not allow for temperature control.
  • It requires a longer preparation time.
  • It generates an unpleasant odor.
  • What is an advantage of impression compound?

  • Good flow properties. (correct)
  • High viscosity.
  • Poor flow characteristics.
  • High shrinkage rate.
  • Which base materials are used in a 2-paste system?

  • Zinc oxide and inert oil. (correct)
  • Olive oil and fillers.
  • Canada balsam and coloring material.
  • Polymerized rosin and hydrogenated rosin.
  • What can reduce the setting time of impression materials?

    <p>Using oil of cloves.</p> Signup and view all the answers

    What is a factor that can lead to a poor consistency in impression materials?

    <p>Inadequate mixing of components.</p> Signup and view all the answers

    What is a characteristic of the clingy impression compounds?

    <p>They shrink significantly over time.</p> Signup and view all the answers

    Which mixing tool is recommended for creating the impression compound?

    <p>A flexible stainless steel spatula.</p> Signup and view all the answers

    Which option is NOT typically used as a filler in the impression compound?

    <p>Sodium bicarbonate.</p> Signup and view all the answers

    What is a property of impression compound with poor behavior?

    <p>They are prone to warping.</p> Signup and view all the answers

    What should NOT be included when preparing the impression material?

    <p>Metal shavings.</p> Signup and view all the answers

    What is a characteristic of irreversible impression materials?

    <p>They undergo a chemical change when set.</p> Signup and view all the answers

    Which of the following is a type of elastic impression material?

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

    How are thermoset impression materials categorized?

    <p>They cannot revert to the original state.</p> Signup and view all the answers

    Which impression tray is designed to fit the unique contours of a patient's mouth?

    <p>Individual tray</p> Signup and view all the answers

    What is the primary feature of thermoplastic impression materials?

    <p>They can be remolded when heated.</p> Signup and view all the answers

    Which type of impression material is primarily used for creating study casts?

    <p>Plaster of Paris</p> Signup and view all the answers

    Which method is NOT a way to soften impression compound?

    <p>Soaking in cold water</p> Signup and view all the answers

    What is a significant property of rigid impression materials?

    <p>They can capture fine details accurately.</p> Signup and view all the answers

    Which impression material is categorized as a thermoplastic?

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

    Which type of impression material is suitable for edentulous patients?

    <p>Plaster of Paris</p> Signup and view all the answers

    Study Notes

    Impression Materials Overview

    • Impression materials are utilized to create negative reproductions (impressions) and positive reproductions (casts).
    • Accurate copying of the oral cavity is essential for effective dental procedures.

    Setting Mechanism

    • Irreversible setting indicates materials cannot revert to their original state.
    • Reversible setting signifies no chemical change occurs during the hardening process.

    Classification of Impression Materials

    • Study casts are made during the fabrication of individual trays.
    • Impression materials categorized by their hardening method: either thermoplastic or thermoset.
    • Classification based on physical properties: rigid/inelastic for edentulous patients & elastic for dentate patients.

    Types of Impression Materials

    • Thermoset (Irreversible):
      • Includes Plaster of Paris, ZOE paste, and rubber impression materials like polysulfide, polyether, condensation silicone, addition silicone.
    • Thermoplastic (Reversible):
      • Comprises modeling compounds and agar.

    Manner of Withdrawal

    • Rigid materials require teasing movement while elastic materials need a sudden pull parallel to the tooth's long axis.

    Impression Trays

    • Various types of impression trays:
      • Stock trays
      • Rim-locked trays
      • Individual trays
      • Perforated trays
      • Water-cooled trays

    Impression Compound

    • Has multiple names and classifications based on usage.
    • Can be dispensed in various colors.
    • Uses: Custom fitting for prosthetics, diagnostics, and treatment planning.

    Softening Methods for Impression Compound

    • Two primary methods for softening:
      • Dry Heat Method: Utilizes direct flame.
      • Moist Heat Method: Involves hot water.

    Disadvantages of Moist Heat Method

    • Potential for overheating and alteration of physical properties.
    • Can lead to inadequate impressions.

    Properties of Impression Compound

    • Shrinkage rates range from 0.3% to 0.4%.
    • Exhibits good flow properties but possesses disadvantages such as poor compatibility.

    Cast Construction and Separation

    • Use of plaster of paris is common; it can be applied in thin pastes without conventional washes.
    • Two-paste system identified as Type I and Type II.

    Components of Impression Compound

    • Base materials typically include zinc oxide and inert oils.
    • Reactors or catalysts like oil of cloves may be added alongside accelerators for enhanced performance.

    Additional Component Functions

    • Fillers, coloring materials, and flavoring agents enhance usability and appeal.

    Manipulation Techniques

    • The proper technique involves a flexible stainless steel spatula with broad strokes, mixing for 3-5 minutes.
    • Teasing methods can influence setting time, impacting consistency and material strength positively and negatively.

    Temperature Effects on Setting Time

    • Hot water application for 5-10 minutes can affect the setting characteristics of impression materials in Types II, III, and IV.

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    Description

    This quiz covers the different types of impression materials used in dentistry, focusing on their setting mechanisms and classifications. Learn about irreversible and reversible materials, along with their properties and applications in dental practice. Test your understanding of how these materials are used in producing accurate dental casts.

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