Types of Impression Taking in Dentistry
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Questions and Answers

What is the role of zinc acetate in the composition of the catalyst?

  • It acts as a plasticizer.
  • It is a flavoring material.
  • It serves as a filler.
  • It accelerates the setting time. (correct)
  • Which of the following ingredients is used to prevent the crystallization of the paste?

  • Calcium chloride
  • Eugenol
  • Zinc acetate (correct)
  • Waxes
  • What effect does longer mixing time have on the setting time?

  • It decreases the setting time. (correct)
  • It has no effect.
  • It results in a thicker consistency.
  • It increases the setting time.
  • Which of the following options serves as a plasticizer in the mix?

    <p>Linseed oil</p> Signup and view all the answers

    What materials can be added to thickening a thin paste?

    <p>Wax or inert powder</p> Signup and view all the answers

    What is the temperature range for immersing a set stone to separate it from the impression?

    <p>49C-60C</p> Signup and view all the answers

    What method is recommended for softening a large amount of material?

    <p>Moist heat method</p> Signup and view all the answers

    What happens if material is heated for an excessive period using the moist heat method?

    <p>It becomes brittle and grainy</p> Signup and view all the answers

    Which of the following is a disadvantage of using the moist heat method?

    <p>Water incorporation can alter plasticity</p> Signup and view all the answers

    What is the classification of Zoe Impression Paste?

    <p>Thermoset, Rigid</p> Signup and view all the answers

    What is the main purpose of the coloring pigments and flavoring agent in the material?

    <p>For aesthetic enhancement</p> Signup and view all the answers

    Which method of manipulation involves heating over a flame?

    <p>Dry heat method</p> Signup and view all the answers

    What is NOT a characteristic of Type I material?

    <p>15 minutes final setting time</p> Signup and view all the answers

    Which technique is used for the manner of withdrawal in impression taking?

    <p>Teasing method</p> Signup and view all the answers

    What is the primary purpose of using hardening agents in the material?

    <p>To enhance strength</p> Signup and view all the answers

    Which material does not require a separating medium?

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

    What is the dimensional change percentage of the impression compound during setting?

    <p>0.3-0.4%</p> Signup and view all the answers

    Which of the following is NOT a use of Zoe Impression Paste?

    <p>As a permanent crown material</p> Signup and view all the answers

    What is the recommended mixing time for Zoe Impression Paste?

    <p>30-45 seconds</p> Signup and view all the answers

    What role does inert oil serve in the composition of Zoe Impression Paste?

    <p>Acts as a plasticizer</p> Signup and view all the answers

    What is the setting time range for Zoe Impression Paste?

    <p>3-5 minutes</p> Signup and view all the answers

    Which factor prolongs the setting time of Zoe Impression Paste?

    <p>Presence of oil</p> Signup and view all the answers

    What is the primary function of eugenol in the composition of Zoe Impression Paste?

    <p>To mask irritation</p> Signup and view all the answers

    What type of impression material is an example of thermoplastic?

    <p>Impression compound</p> Signup and view all the answers

    Which of the following correctly describes impression plaster?

    <p>It sets through a hydration reaction.</p> Signup and view all the answers

    What is the proper proportion for mixing Zoe Impression Paste?

    <p>1:1</p> Signup and view all the answers

    What is meant by the 'teasing method' in the context of Zoe Impression Paste?

    <p>A method of withdrawal</p> Signup and view all the answers

    What is not a characteristic of thermoplastic materials?

    <p>They can undergo chemical changes upon heating.</p> Signup and view all the answers

    What is one of the components of the reactor/catalyst in Zoe Impression Paste?

    <p>Polymerized Rosin</p> Signup and view all the answers

    Which of the following is NOT a form of impression compound?

    <p>Liquid form</p> Signup and view all the answers

    What color is commonly associated with impression plaster?

    <p>Light pink</p> Signup and view all the answers

    What is the primary use of impression plaster?

    <p>Final impressions</p> Signup and view all the answers

    Which component is used in impression compound to help render it soluble?

    <p>Potato starch</p> Signup and view all the answers

    What type of impression is an impression compound primarily used for?

    <p>Preliminary impression</p> Signup and view all the answers

    What is NOT a method of dispensing impression plaster?

    <p>Stick forms</p> Signup and view all the answers

    What is the recommended water/powder (W/P) ratio for manipulating peppermint flavoring material?

    <p>0.50 - 0.75</p> Signup and view all the answers

    What is the setting time for peppermint flavoring material?

    <p>3-5 minutes</p> Signup and view all the answers

    Which type of impression compound is used for edentulous impressions?

    <p>Type I</p> Signup and view all the answers

    What kind of impression compound is characterized as low fusing and has a flow property?

    <p>Type I</p> Signup and view all the answers

    What is a major disadvantage of impression compounds?

    <p>Continuous flow can cause errors</p> Signup and view all the answers

    Which of the following components is responsible for the thermoplastic property of impression compounds?

    <p>Thermoplastic Resin</p> Signup and view all the answers

    What is characteristic of Type II impression compound?

    <p>More rigid than Type I</p> Signup and view all the answers

    What is the compressive strength of the impression compound?

    <p>580 +/- 290 PSI</p> Signup and view all the answers

    Which material acts as a plasticizer in impression compounds?

    <p>Stearic Acid</p> Signup and view all the answers

    What should be done after mixing peppermint flavoring material to avoid air bubbles?

    <p>Tap the tray gently</p> Signup and view all the answers

    Study Notes

    Perforated Tray and Water-Cooled Tray

    • Perforated trays are designed for better impression material retention.
    • Water-cooled trays help control temperature during the impression process.

    Types of Impression Taking

    • Thermoplastic Materials: Soft when heated and solidify upon cooling without chemical changes.
    • Examples: Modelling compound and impression compound.
    • Impression Types:
      • Single Impression
      • Double Impression (includes preliminary and final impressions)
        • Preliminary is less accurate; final is designed to correct defects.

    Impression Plaster

    • Known as Type I Dental Gypsum or Soluble Plaster.
    • Classifies as thermoset and rigid, primarily for final or secondary impression making.
    • Manner of dispensing: Powder mixed with water causing hydration leading to set; typically light pink color.
    • Used for making impressions of edentulous arches.

    Impression Compound

    • Also termed Modeling Plastic or Dental Impression Compound.
    • Classifies as thermoplastic and rigid, used for preliminary impressions.
    • Dispensed in various forms (cakes, sticks, cones) in colors like pink and brown.
    • Utilized for border molding and specific impression techniques.

    Manipulation of Materials

    • Water-Powder (W/P) Ratio: Recommended range of 0.50 - 0.75 to manage exothermic heat.
    • Mixing time: one minute in a single rotary motion to ensure thorough mixing.
    • Initial setting time is between 3 to 5 minutes.
    • To remove air, tap impression trays before seating in the patient's mouth.

    Properties of Impression Materials

    • Setting Expansion: Approximately 0.3%.
    • Compressive Strength: Averaged at 580 +/- 290 PSI.
    • Impression materials can be brittle and easily fractured.

    Types of Impression Compound

    • Type I: Known as true impression compound, low fusing (melting point 55 - 65°C), good flow properties, ideal for final impressions.
    • Type II: Tray compound, high fusing (70°C), used for rigider individual trays.

    Disadvantages of Impression Compound

    • Continuous flow properties can hinder immediate cast construction, potentially leading to errors.

    Zoe Impression Paste

    • Mixture forms a thin paste for custom trays.
    • Classifies as thermoset and rigid, not effective for recording undercuts.
    • Manner of dispensing: Two-paste system (base and catalyst) dispensed from collapsible tubes.
    • Types vary:
      • Type I (hard set) with a 3-6 min initial setting time.
      • Type II (soft set) with similar initial times.

    Factors Affecting Setting Time (ST)

    • High humidity and temperature reduce ST.
    • Cool mixing supplies extend ST.
    • Shorter mixing durations can compress ST, requiring careful control.

    Cast Construction

    • No separating medium is needed during cast construction.
    • After setting, immersion in hot water (49C-60C for 5-10 min) aids in separation from the impression.
    • Cast materials used with Zoe impression materials are primarily gypsum types.

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    Description

    This quiz covers various methods of impression taking in dentistry, including thermoplastic materials and the processes involved in single and double impressions. Understand the characteristics of water-cooled and perforated trays, as well as the implications of thermal changes on impression materials.

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