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What is the role of zinc acetate in the composition of the catalyst?
Which of the following ingredients is used to prevent the crystallization of the paste?
What effect does longer mixing time have on the setting time?
Which of the following options serves as a plasticizer in the mix?
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What materials can be added to thickening a thin paste?
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What is the temperature range for immersing a set stone to separate it from the impression?
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What method is recommended for softening a large amount of material?
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What happens if material is heated for an excessive period using the moist heat method?
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Which of the following is a disadvantage of using the moist heat method?
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What is the classification of Zoe Impression Paste?
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What is the main purpose of the coloring pigments and flavoring agent in the material?
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Which method of manipulation involves heating over a flame?
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What is NOT a characteristic of Type I material?
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Which technique is used for the manner of withdrawal in impression taking?
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What is the primary purpose of using hardening agents in the material?
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Which material does not require a separating medium?
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What is the dimensional change percentage of the impression compound during setting?
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Which of the following is NOT a use of Zoe Impression Paste?
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What is the recommended mixing time for Zoe Impression Paste?
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What role does inert oil serve in the composition of Zoe Impression Paste?
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What is the setting time range for Zoe Impression Paste?
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Which factor prolongs the setting time of Zoe Impression Paste?
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What is the primary function of eugenol in the composition of Zoe Impression Paste?
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What type of impression material is an example of thermoplastic?
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Which of the following correctly describes impression plaster?
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What is the proper proportion for mixing Zoe Impression Paste?
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What is meant by the 'teasing method' in the context of Zoe Impression Paste?
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What is not a characteristic of thermoplastic materials?
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What is one of the components of the reactor/catalyst in Zoe Impression Paste?
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Which of the following is NOT a form of impression compound?
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What color is commonly associated with impression plaster?
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What is the primary use of impression plaster?
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Which component is used in impression compound to help render it soluble?
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What type of impression is an impression compound primarily used for?
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What is NOT a method of dispensing impression plaster?
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What is the recommended water/powder (W/P) ratio for manipulating peppermint flavoring material?
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What is the setting time for peppermint flavoring material?
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Which type of impression compound is used for edentulous impressions?
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What kind of impression compound is characterized as low fusing and has a flow property?
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What is a major disadvantage of impression compounds?
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Which of the following components is responsible for the thermoplastic property of impression compounds?
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What is characteristic of Type II impression compound?
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What is the compressive strength of the impression compound?
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Which material acts as a plasticizer in impression compounds?
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What should be done after mixing peppermint flavoring material to avoid air bubbles?
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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.
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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.
