15 Questions
What is the purpose of an impression tray in dentistry?
To carry, confine & control the impression material in the patient's mouth
What are the requirements of an impression tray?
It should retain its shape throughout the impression procedure and while pouring stone on the impression
How should the border extension of an impression tray be positioned?
2mm short of the vestibular depth with no interference with muscle or frenal attachment
Which material can be used to fabricate metallic trays?
Stainless steel
What type of trays can be classified as non-metallic?
Plastic trays and acrylic resin trays
What is the function of the spacer in the custom tray?
To properly position the tray during border molding
What is the function of the handle in the custom tray?
Supports the lip while making impression
What is the purpose of applying a separating medium on the cast?
To prevent acrylic resin from sticking to the cast
Why should disposable trays be recommended?
To prevent cross-contamination
What is the purpose of fabricating two posterior handles for mandibular trays?
As finger rests to stabilize tray in mouth
What type of impression material is suitable for close-fit trays?
Impression materials of low viscosity
What is the primary purpose of stock trays?
To make primary impressions
What type of custom tray uses wax spacer to provide space for impression material?
Tray with spacer and stops
Which factor affects the selection of stock trays?
Size of the arch
What are the materials used for fabricating custom trays?
Shellac base plate, impression compound, and cold, hot or light cure acrylic resin
Study Notes
- Method of fabrication of trays: Stock trays (full arch, sectional, quadrant), Custom trays or Special trays
- According to the presence or absence of teeth: Edentulous trays (rounded cross-section), Dentulous trays (square cross-section)
- Stock trays: Reusable, comes in specific sizes, used to make primary impression, materials include Al, Tin, Brass or Plastic
- Factors affecting selection of stock tray: Type of impression material, size of the arch, form of the arch, and coverage of anatomical landmarks
- Custom trays: Fabricated on a patient's cast, unique to the patient, used for making final impression, materials include shellac base plate, impression compound, and cold, hot or light cure acrylic resin
- Factors affecting selection of custom tray: Materials used, compatibility with impression material, and accuracy of fit
- Types of custom trays: Close-fit tray, tray with spacer and stops
- Close-fit tray: Adapted directly onto the cast without wax spacer, used with impression materials of low viscosity
- Tray with spacer and stops: Uses wax spacer to provide space for impression material, used with impression materials of high viscosity
- Advantages of special trays: More accurate impression, even thickness of impression material, easier fabrication, better retention, and less bulky.
Test your knowledge about dental impression trays and their usage in prosthetic dentistry. Learn about the definition of dental impressions and the purpose of impression trays.
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