30 Questions
What are the key properties of ideal impression materials used in Fixed Prosthodontics?
Dimensional stability, tear resistance, and ability to reproduce fine details
Why is it important to add perforations to custom trays for dentate patients?
To help in mechanical retention of impression material
What are the learning objectives related to impression materials in Fixed Prosthodontics?
Classify impression materials, identify the features of ideal and unacceptable impressions, compare different types of impression trays, list disinfection methods, identify impression techniques, and explain properties of ideal impression materials.
What are the key terms related to impression materials in Fixed Prosthodontics?
Impression material, impression tray, and dental impression
What are the specifications of a custom tray for dentate patients?
Thickness of tray 2-3 mm (acrylic material) and addition of 2mm diameter perforations
What are the advantages of elastomeric impression materials?
Good dimensional stability, high accuracy, and excellent tear strength
Which characteristic of ideal impression material is related to the material's ability to flow without slumping?
Wettability
What is the primary purpose of using two different materials with different viscosities in full coverage restorations?
To capture fine details and bulk
Which characteristic is NOT considered an ideal impression material characteristic?
High filler content
What is the primary purpose of measuring wettability in impression materials?
To test wetting properties
Which characteristic is critical for addressing troubleshooting in impression making?
Dimensional stability
What is the purpose of using hydrophilic impression materials despite their requirement for good moisture control?
To ensure accurate impressions
What is the purpose of a stopper and wax spacer in dental impression techniques?
To prevent impression material from making intimate contact with teeth and to temporarily fill space during custom tray construction
Why are custom trays preferred over stock trays for multiple teeth restoration?
They are rigid and minimize distortion
What is the advantage of using custom metal trays for dental impressions?
Rigidity and ability to accommodate material
Why is tray adhesive added to the impression tray?
To chemically retain and prevent distortion of the impression material
What is the purpose of capturing preparation stress with a spacer in the impression material?
To minimize distortion of the impression material
What is the significance of pouring elastomeric impression materials within 30 minutes of setting?
To ensure accurate reproduction of oral tissues
Which impression material undergoes cationic polymerization with no by-product formation?
Polyether
What is the main disadvantage of using latex gloves when mixing PVS putties?
They inhibit polymerization of PVS materials
What is the main advantage of polyether over addition silicone?
Hydrophilicity
What is the main reason for difficulties in removal from undercut areas when using addition silicones?
Stiffness
What type of gloves should be used to avoid contamination when handling condensation silicones?
Vinyl gloves
What is the shelf life of condensation silicones?
Limited
What is the working time for addition silicone (PVS) impression materials?
5 minutes
What is the setting time for polysulfide impression materials?
8-14 minutes
What is the required detail reproduction level for putty impression materials?
75 microns
What is the nature of surfactants added to hydrophobic silicones in dental impression materials?
Combat their nature and improve wettability
What is the nature of die stones in reproducing detail in dental impressions?
Required to reproduce detail down to 50 microns
What is the shelf-life limitation of condensation silicone impression materials?
Limited due to its sensitivity to heat and moisture
Study Notes
Dental Impression Materials Overview
- Dental impression materials capture details with low viscosity and must be removed from the patient's mouth without distortion
- Surfactants are added to hydrophobic silicones to combat their nature and improve wettability
- Elastomeric impression materials are required to record detail down to 20 microns
- Die stones are required to reproduce detail down to 50 microns
- Putty captures details down to 75 microns
- Working time for elastomeric impression materials is approximately 2 minutes, and setting time is 2-6 minutes
- Elastomeric impression materials have three types of viscosity: low, medium, and heavy
- Polysulfide materials have a thixotropic property and are supplied as two pastes: base and catalyst
- Polysulfide materials have a working time of 5-7 minutes and a setting time of 8-14 minutes
- Condensation silicone undergoes a condensation reaction that produces ethyl alcohol as a by-product, causing high shrinkage
- Addition silicone, also known as polyvinylsiloxanes (PVS), have a working time of 5 minutes and a setting time of 10-12 minutes
- Shelf-life of condensation silicone is limited due to its sensitivity to heat and moisture
Test your knowledge of dental impression materials with this overview quiz. Explore topics such as elastomeric materials, die stones, putty, polysulfide materials, condensation silicone, and addition silicone. Gain insight into working time, setting time, viscosity, and other essential characteristics of these materials.
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