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Questions and Answers
What is a significant disadvantage of using polysulfide as an impression material?
What is a significant disadvantage of using polysulfide as an impression material?
What type of polymerization does polysulfide undergo?
What type of polymerization does polysulfide undergo?
Which characteristic of polysulfide is considered an advantage?
Which characteristic of polysulfide is considered an advantage?
How long should polysulfide be poured within to ensure accuracy?
How long should polysulfide be poured within to ensure accuracy?
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What is a primary characteristic of elastomeric impression materials?
What is a primary characteristic of elastomeric impression materials?
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Which type of impression material has the highest dimensional stability?
Which type of impression material has the highest dimensional stability?
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What is a disadvantage of using Polyether as an impression material?
What is a disadvantage of using Polyether as an impression material?
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Which impression material is hydrophilic?
Which impression material is hydrophilic?
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What by-product is generated during condensation polymerization of silicon?
What by-product is generated during condensation polymerization of silicon?
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Which type of impression material should be poured within 30 minutes of setting?
Which type of impression material should be poured within 30 minutes of setting?
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Which impression material has no by-products during polymerization?
Which impression material has no by-products during polymerization?
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What is a common challenge with hydrophobic impression materials?
What is a common challenge with hydrophobic impression materials?
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Which of the following materials is known for having the best elastic properties?
Which of the following materials is known for having the best elastic properties?
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Which impression material is considered irreversible and most widely used for study models?
Which impression material is considered irreversible and most widely used for study models?
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What is a key advantage of using hydrocolloids in dental impressions?
What is a key advantage of using hydrocolloids in dental impressions?
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What characteristic must impression materials have for easy manipulation?
What characteristic must impression materials have for easy manipulation?
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What is one major disadvantage of using irreversible hydrocolloid materials like alginate?
What is one major disadvantage of using irreversible hydrocolloid materials like alginate?
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Which of the following materials is considered an elastomer in impression making?
Which of the following materials is considered an elastomer in impression making?
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Which method is NOT typically used for controlling hemorrhage during impression taking?
Which method is NOT typically used for controlling hemorrhage during impression taking?
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What is a primary requirement for the immediate pouring of some impression materials?
What is a primary requirement for the immediate pouring of some impression materials?
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Which type of impression material is known to exhibit excellent dimensional stability?
Which type of impression material is known to exhibit excellent dimensional stability?
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What is the primary purpose of an impression in dental practice?
What is the primary purpose of an impression in dental practice?
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Which of the following imperfections should be avoided in an impression?
Which of the following imperfections should be avoided in an impression?
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What is a key requirement for impression trays?
What is a key requirement for impression trays?
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What is the function of the displacement cord during impression making?
What is the function of the displacement cord during impression making?
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Which type of impression tray is more accurate?
Which type of impression tray is more accurate?
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What thickness should be maintained for the impression material in special trays?
What thickness should be maintained for the impression material in special trays?
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Which method can be used to control hemorrhage during the impression making process?
Which method can be used to control hemorrhage during the impression making process?
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Why is moisture control considered a challenge in taking impressions?
Why is moisture control considered a challenge in taking impressions?
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Study Notes
Tissue Management and Impression Making
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Impressions are negative likenesses of teeth and surrounding structures. They are essential for creating fixed restorations in the lab.
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An acceptable impression should have:
- Prepared/unprepared tooth surfaces
- Accurate margins
- Accurate surrounding structures
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Impressions should be free from:
- Air bubbles
- Tears
- Other imperfections
Impression Trays
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Requirements:
- Rigid
- Dimensionally stable
- Provide even space for impression material
- Proper extension
- Retentive for impression material
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Types:
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Stock trays:
- Metallic/plastic
- Time-saving
- Material usage
- Require sterilization
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Special trays:
- Acrylic resin
- More accurate
- Material usage
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Stock trays:
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Thickness: Typically 2-3mm
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Separation: 2mm separation that extends 3-5 mm apically to the gingival margin and 3mm beyond the most distal tooth.
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Tissue Stops: Usually on non-functioning cusps of unprepared teeth
Impression Materials
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Properties:
- Easy to mix and handle
- Fluid
- Reasonable working and setting time
- Non-harmful
- Elastic
- Adhere to the tray
- Stable
- Easy to pour
- Acceptable to the patient
- Multiple pouring
Classification of Impression Materials
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Elastic Impression Materials:
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Aqueous Hydrocolloids:
- Irreversible (Alginate): Widely used, suitable for study models or opposing non-prepped dentition.
- Reversible (Agar): Excellent dimensional stability and hydrophilic, requires immediate pouring.
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Elastomers:
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Polysulfide: First dental elastomeric material, 2 pastes with 3 viscosities. Hydrophobic and uses condensation polymerization.
- Advantages: Long working time, high tear strength, high flexibility, good flow and detail.
- Disadvantages: Poor dimensional stability, water byproduct, pour within 1 hour, single pour, requires special tray, smelly, stains, long setting time, impacted by temperature and humidity
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Polyether: 2 pastes with 3 viscosities, no by-products, hydrophilic. Can be hand mixed or automated. Additional polymerization.
- Advantages: High accuracy, high dimensional stability, stock or special trays, good surface details, pour within 1 week (saved dry).
- Disadvantages: Short working time, highly rigid, low tear strength, absorbs water
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Condensation Silicons: Base and catalyst in 4 viscosities, Hydrophobic and Condensation polymerization.
- Advantages: Better elastic properties, good working and setting time, stock or special trays.
- Disadvantages: Poor dimensional stability, high shrinkage, needs to be poured within 30 minutes, hydrophobic, low tear strength .
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Addition Silicons: Base and catalyst with 4 viscosities, Addition polymerization, no by-products, hydrophobic.
- Advantages: Highly accurate, high dimensional stability (pour within 1 week), stock or special tray, multiple pouring, easy to mix.
- Disadvantages: Surfer inhibit polymerization, Latex gloves contain sulfur, Short working time, lower tear strength, absorbs water, hydrophobic
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Polysulfide: First dental elastomeric material, 2 pastes with 3 viscosities. Hydrophobic and uses condensation polymerization.
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Aqueous Hydrocolloids:
Comparisons of Impression Materials
- Working time: Alginate < Polyether < Silicons < Polysulfide < Agar
- Setting time: Alginate < Polyether < Agar < Silicons < Polysulfide
- Stiffness: Polyether > Silicons > Polysulfide > Hydrocolloids
- Tear Strength: Polysulfide > Silicons > Polyether > Silicons > Hydrocolloid
- Cost: Alginate < Agar < Polysulfide < Silicons < Polyether
- Dimensional Stability: Silicons > Polyether > Polysulfide > Silicons > Hydrocolloid
- Wettability: Hydrocolloids > Polyether > Silicons > Polysulfide > Silicons
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Description
This quiz delves into the essential techniques of tissue management and impression making in dental restorations. You'll explore the characteristics of acceptable impressions and the requirements for different types of impression trays. Test your knowledge to ensure accuracy and efficiency in creating dental impressions.
