Questions and Answers
What is a disadvantage of using the moist heat method?
What is an advantage of impression compound?
Which base materials are used in a 2-paste system?
What can reduce the setting time of impression materials?
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What is a factor that can lead to a poor consistency in impression materials?
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What is a characteristic of the clingy impression compounds?
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Which mixing tool is recommended for creating the impression compound?
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Which option is NOT typically used as a filler in the impression compound?
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What is a property of impression compound with poor behavior?
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What should NOT be included when preparing the impression material?
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What is a characteristic of irreversible impression materials?
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Which of the following is a type of elastic impression material?
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How are thermoset impression materials categorized?
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Which impression tray is designed to fit the unique contours of a patient's mouth?
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What is the primary feature of thermoplastic impression materials?
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Which type of impression material is primarily used for creating study casts?
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Which method is NOT a way to soften impression compound?
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What is a significant property of rigid impression materials?
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Which impression material is categorized as a thermoplastic?
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Which type of impression material is suitable for edentulous patients?
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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.
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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.
