Podcast
Questions and Answers
The function of an impression material is to accurately record the dimensions of oral tissues and their spatial ______.
The function of an impression material is to accurately record the dimensions of oral tissues and their spatial ______.
relationships
A positive reproduction obtained from an impression is referred to as a ______ when large areas of oral tissues are involved.
A positive reproduction obtained from an impression is referred to as a ______ when large areas of oral tissues are involved.
model
Thermoplastic impression materials soften under heat and solidify when ______.
Thermoplastic impression materials soften under heat and solidify when ______.
cooled
An individual tray is a self-made tray created specifically for one ______.
An individual tray is a self-made tray created specifically for one ______.
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Type I dental gypsum is an example of a ______ impression material that hardens by chemical reaction.
Type I dental gypsum is an example of a ______ impression material that hardens by chemical reaction.
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Impression plasters are plasters of Paris to which ______ have been added to regulate the setting time.
Impression plasters are plasters of Paris to which ______ have been added to regulate the setting time.
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The W:P ratio for manipulating impression plasters is typically between ______ and 0.7.
The W:P ratio for manipulating impression plasters is typically between ______ and 0.7.
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To facilitate easy removal of the cast, a coat of ______ should be painted onto the impression plaster before pouring in gypsum.
To facilitate easy removal of the cast, a coat of ______ should be painted onto the impression plaster before pouring in gypsum.
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The maximum setting time for impression plaster is typically between ______ and 5 minutes.
The maximum setting time for impression plaster is typically between ______ and 5 minutes.
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Type II impression compound is also known as ______ compound.
Type II impression compound is also known as ______ compound.
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Study Notes
Impression Materials Overview
- Impression materials capture the dimensions and spatial relationships of oral tissues.
- The negative impression obtained is used to create a positive model or cast by pouring dental stone or similar material.
Types of Impressions
- Preliminary Impression: Initial impression for study cast development.
- Secondary/Final/Wash Impression: Corrective impressions for master or working cast creation for prosthesis.
Classification by Use in Dentistry
- Restorative Dentistry: Does not use modeling compound impression materials.
- Prosthodontics: Involves creating prosthetic devices.
- Orthodontics: Focuses on dental alignment and braces.
Classification by Manner of Hardening
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Thermoplastic Impression Materials:
- Softens with heat and solidifies upon cooling; no chemical change during this process.
- Examples: modeling compound, agar, waxes.
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Thermoset Impression Materials:
- Hardens via chemical reaction upon mixing.
- Examples: dental gypsum (Type I), alginate, rubber materials (polysulfide, silicone, polyether), zinc oxide eugenol pastes.
Types of Impression Materials
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Rigid Impression Materials: Hardens upon removal; used in edentulous mouths without undercuts.
- Examples: modeling compound, impression plaster, zinc oxide eugenol paste.
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Elastic Impression Materials: Flexible upon removal, suitable for areas with undercuts.
- Examples: alginate, agar, rubber impression materials.
Impression Trays
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Stock Trays: Pre-manufactured trays.
- Non-perforated: For modeling compound.
- Rim-locked: Added retention for impression material.
- Perforated: Enhances retention and pressure release.
- Individual Trays: Custom-made trays tailored to the patient's mouth using acrylic or shellac.
- Water-Cooled Tray: Specifically designed for agar impression material.
Impression Plaster
- Hardly used due to rigidity and fragility but valued for short setting times.
- Primarily for mounting casts or occlusal bite registrations, classified as thermoset and rigid.
- Color: Light pink.
- Composition includes CaSO4·2H2O, and potato starch for easy removal post-setting.
Manipulation of Impression Plaster
- Mix using a plaster bowl at a water-to-powder ratio of 0.6-0.7.
- Increase water to reduce exothermic heat during mixing.
- Setting time ranges from 3 to 5 minutes.
- Withdraw carefully from the mouth with a teasing motion to avoid fracture.
Casting and Separation Techniques
- Apply a separating medium (Colorgard) to the impression before pouring the gypsum cast.
- Allow the cast to set for 30–60 minutes before separation.
- Submerging in hot water aids in the de-molding process.
Modeling Compound Types
- Type I: Low fusing compound, softens at 55-65°C; often used for final impressions or check impressions.
- Type II: Tray compound tailored for specific applications.
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Description
Test your knowledge about dental impression materials and their functions. This quiz covers the process of creating impressions and the importance of accurately recording oral tissue dimensions. Learn about the materials used and their setting properties.
