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Questions and Answers
Which of the following statements accurately describes a property of elastomeric impression materials?
Which of the following statements accurately describes a property of elastomeric impression materials?
What is a common issue associated with polysulphide elastomers during the setting process?
What is a common issue associated with polysulphide elastomers during the setting process?
How does the setting reaction of elastomers primarily occur?
How does the setting reaction of elastomers primarily occur?
Which viscosity class of elastomeric impression material is typically available only in silicones?
Which viscosity class of elastomeric impression material is typically available only in silicones?
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What clinical significance do elastomers hold in dentistry?
What clinical significance do elastomers hold in dentistry?
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Which elastomeric impression material has the highest stiffness?
Which elastomeric impression material has the highest stiffness?
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What is the recommended time frame to pour models and dies for polysulfide and condensation silicones to achieve the greatest accuracy?
What is the recommended time frame to pour models and dies for polysulfide and condensation silicones to achieve the greatest accuracy?
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Which of the following factors can cause dimensional change in elastomeric impressions?
Which of the following factors can cause dimensional change in elastomeric impressions?
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How does rapid removal of impression materials affect tear strength?
How does rapid removal of impression materials affect tear strength?
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Which impression material has the best wettability?
Which impression material has the best wettability?
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Which mixing technique utilizes a self-contained system to achieve a homogeneous mixture?
Which mixing technique utilizes a self-contained system to achieve a homogeneous mixture?
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What is the effect of imbibition on elastomeric impressions?
What is the effect of imbibition on elastomeric impressions?
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What is a significant clinical concern regarding impression stiffness during removal?
What is a significant clinical concern regarding impression stiffness during removal?
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What is a primary disadvantage of hand mixing impression materials?
What is a primary disadvantage of hand mixing impression materials?
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Which technique uses a single viscosity for the impression material?
Which technique uses a single viscosity for the impression material?
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What advantage does static automixing provide over hand mixing?
What advantage does static automixing provide over hand mixing?
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What is a key characteristic of the dynamic mechanical mixing technique?
What is a key characteristic of the dynamic mechanical mixing technique?
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In the multiple mix technique, what is a major disadvantage?
In the multiple mix technique, what is a major disadvantage?
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What type of impression materials can be used in the putty-wash technique?
What type of impression materials can be used in the putty-wash technique?
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What is a common property of elastomers that is critical for their use in dental impressions?
What is a common property of elastomers that is critical for their use in dental impressions?
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Which technique allows for the simultaneous use of two viscosity materials during an impression?
Which technique allows for the simultaneous use of two viscosity materials during an impression?
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Study Notes
Elastomeric Impression Materials
- Polysulfide, Silicones, and Polyethers are the three main types of elastomeric impression materials.
- Condensation Silicones are a type of silicone with a condensation polymerization reaction, releasing water as a by-product.
- Addition Silicones are a type of silicone with an addition polymerization reaction, releasing ethyl alcohol as a by-product.
- Hydrophobic Materials repel water.
- Hydrophilic Materials attract water.
Viscosity Classes
- Low Viscosity (light body) is used for fine detail capture.
- Medium Viscosity (regular body) is used for general impressions.
- High Viscosity (heavy body) is used for supporting the impression.
- Putty (Extra Heavy) is used for stabilizing the impression in the tray.
Polysulfide Impression Materials
- Supplied as two pastes (base & catalyst) in collapsible tubes.
- Setting Reaction: Condensation polymerization.
- Exothermic reaction (increase in temperature) during setting.
- Release of water as a by-product causing dimensional instability.
- Advantages: High flexibility, high tear strength, long working time, lower cost.
- Disadvantages: Poor dimensional stability, long setting time, messy due to lead dioxide, requires custom or special trays.
Silicone Impression Materials
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Condensation Silicones:
- Supplied as two pastes (base & catalyst) in collapsible tubes.
- Setting reaction is condensation polymerization.
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Clinical Significance:
- Pseudoplasticity: Material flows easily when syringed and solidifies into a stable impression.
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Advantages:
- High flexibility and tear strength.
- Good detail reproduction.
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Disadvantages:
- Dimensional instability.
- Limited shelf life.
- Requires a special tray.
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Addition Silicones:
- Available in one or two paste systems.
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Clinical Significance:
- Pseudoplasticity: Allows for one-step materials (monophase) with improved adaptation in the mouth.
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Advantages:
- Excellent dimensional stability.
- Shorter setting time.
- Fewer air bubbles.
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Disadvantages:
- Higher cost.
- May need a special tray.
Polyether Impression Materials
- Supplied as two pastes (base & catalyst) in collapsible tubes.
- Setting Reaction: Addition polymerization.
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Advantages:
- Excellent dimensional stability.
- High rigidity and tear strength.
- Good detail reproduction.
- High wettability (adheres to wet surfaces).
- High accuracy.
- Can be poured up to one week after the impression.
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Disadvantages:
- May be difficult to remove from the mouth.
- Requires special trays due to stiffness.
Properties of Rubber Base Impression Materials
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Flexibility and Stiffness:
- Polysulfide is the least stiff (most flexible).
- Polyether is the stiffest.
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Clinical Significance:
- Impression removal: Stiffness can affect loose teeth.
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Dimensional Stability:
- Influenced by polymerization shrinkage, loss of by-products, thermal contraction, and imbibition (absorption of water).
- Condensation Silicone and Polysulfide should be poured within 30 minutes for optimal accuracy.
- Addition Silicone and Polyether can be poured up to 24 hours or even a week.
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Tear Strength:
- Affected by the speed of removal (faster removal increases tear strength).
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Detail Reproduction:
- All elastomers can reproduce fine detail and are compatible with gypsum products.
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Wettability:
- Affected by the presence of surfactants.
- Polyether has the best wettability.
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Shelf Life:
- Store tightly closed in a cool, dry environment.
Manipulation of Elastomeric Impression Materials
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Mixing Systems:
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Hand Mixing:
- Risk of incorporating air bubbles leading to voids in the impression.
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Static Automixing:
- Less mixing time.
- Fewer bubbles.
- Less waste.
- Not suitable for putty consistency.
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Dynamic Mechanical Mixing:
- High speed and accuracy.
- Easy to use.
- Waste of material.
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Hand Mixing:
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Impression Techniques:
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Multiple Mix Technique (Dual-Viscosity):
- Two viscosities (light and heavy) used simultaneously.
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Monophase Technique (Single Viscosity):
- One medium viscosity material.
- Uses pseudoplasticity to adapt to the preparation.
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Putty-Wash Technique:
- Two-Stage (Reline): Light and putty consistency used in two stages.
- Single-Stage: Light and putty consistency used in one stage.
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Multiple Mix Technique (Dual-Viscosity):
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Description
This quiz explores the various types of elastomeric impression materials, including polysulfides, silicones, and polyethers. It covers aspects such as viscosity classes and the chemical reactions involved in different materials. Test your knowledge on the properties and uses of these essential dental materials.
