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Questions and Answers
What type of reaction is involved in the setting process of polysulfide impression material?
What type of reaction is involved in the setting process of polysulfide impression material?
- Irreversible
- Elastic
- Addition
- Chemical (correct)
Which impression material is hydrophilic?
Which impression material is hydrophilic?
- Condensation silicone
- Addition silicone
- Polyether (correct)
- Polysulfide
Polyether impression material is commonly used for making secondary impressions for dentulous and edentulous patients.
Polyether impression material is commonly used for making secondary impressions for dentulous and edentulous patients.
True (A)
What is the definition of an impression in dentistry?
What is the definition of an impression in dentistry?
What are some ideal requirements of impression materials? (Select all that apply)
What are some ideal requirements of impression materials? (Select all that apply)
What is the purpose of trays in dental impressions?
What is the purpose of trays in dental impressions?
Elastic impression materials are only used for edentulous patients.
Elastic impression materials are only used for edentulous patients.
Match the type of impression material with its setting mechanism:
Match the type of impression material with its setting mechanism:
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Study Notes
Impression Materials
- An impression is a negative reproduction of the teeth and surrounding oral structures.
- Impression material is used for making an impression, inserted into the mouth in a plastic form, and then set.
Ideal Requirements for Impression Materials
- Accurate to produce fine details
- Biocompatible with oral environment, non-toxic, and non-irritant
- Easily manipulated without complicated equipment
- Suitable working time
- Suitable setting time
- Acceptable taste and odor to the patient
- Accept addition and correction
- Easily disinfected without loss of accuracy
- Good shelf life
Factors Affecting Accuracy of Impression Materials
- Flow: sufficient flow to record all fine details and sufficient viscosity to be contained in the tray
- Hydrophilicity: hydrophilic to wet the oral tissues easily
- Dimensional accuracy: no dimensional changes during setting (neither expansion nor contraction)
- Adhesion to the tray: adheres to the tray during removal from the patient's mouth
- Elasticity: elastic after setting to record undercuts without distortion or fracture
- Dimensional stability: no dimensional changes during storage
- Compatibility with model and die materials: does not react with the model and die material or affect its setting reaction
Trays
- Types: metallic, plastic, perforated, non-perforated, stock, and special trays
- Used for making primary and secondary impressions
Impression Types
- Primary impression: low accuracy, uses stock tray
- Secondary impression: high accuracy, uses special tray
Wash Technique
- Involves using two impression materials over each other
- First material has high viscosity to fulfill the bulk of the stock tray, while the second one has high flow to record fine details
Classification of Impression Materials
- According to setting mechanism: reversible, irreversible
- According to behavior after setting: non-elastic (rigid), elastic
Non-Elastic Impression Materials
- Plaster impression material
- Impression compound
- Zinc oxide and eugenol
Elastic Impression Materials
- Hydrocolloids
- Elastomers
Hydrocolloids
- Agar impression material
- Alginate impression material
- Mixture types: true solutions, colloids, suspensions
- Synersis: loss of water, occurs when left in air, results in shrinkage
- Imbibition: uptake of water, occurs when immersed in water, results in expansion
Elastomers
- Types: polysulfide, polyether, addition silicone, condensation silicone
- Higher dimensional accuracy and stability than hydrocolloids
- More expensive than alginate
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