Dental Materials Properties and Uses

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Questions and Answers

What is the purpose of using non-eugenol containing paste?

To improve the impression detail

To reduce irritation (correct)

To accelerate the setting reaction

To increase the thermal conductivity

What is the function of potassium sulfate in impression materials?

To reduce the thermal conductivity

To improve the impression detail

To increase the strength of the material

To accelerate the setting reaction (correct)

Which impression material is commonly used for making primary casts?

Thermoplastic material

Zinc oxide pastes

Impression plaster (correct)

Impression compound

Why is it necessary to pour the impressions immediately?

To prevent distortion of the impression Signup and view all the answers

What type of impression material is used for border molding?

Impression compound Signup and view all the answers

What is the characteristic of zinc oxide pastes?

Low thermal conductivity Signup and view all the answers

What is the main advantage of using β CaSO₄.½ H₂O over ᾁ-hemihydrate in impression plaster?

It requires a lower water-to-powder ratio, reducing the exothermic heat. Signup and view all the answers

What is the purpose of using Zincoxide and Eugenol (ZnO/E) in impression materials?

To make the material more rigid and non-elastic. Signup and view all the answers

What is the composition of impression plaster?

β CaSO₄.½ H₂O Signup and view all the answers

What is the primary use of impression plaster in dentistry?

To make secondary impressions for edentulous patients without bony undercuts. Signup and view all the answers

What is the setting time of impression plaster?

5 minutes Signup and view all the answers

Why is a separating medium required when using impression plaster?

To prevent the material from sticking to the cast. Signup and view all the answers

What is the dimensional stability of impression plaster?

0.06% change on setting Signup and view all the answers

What type of tray is recommended for use with impression plaster?

Acrylic tray Signup and view all the answers

What is the main reason for the dry mouth sensation during impression taking?

The impression compound absorbs water Signup and view all the answers

What is the characteristic of Type I Impression Compound?

It is a low-fusing impression compound Signup and view all the answers

What is the purpose of adding a plasticizer to the impression compound?

To decrease brittleness Signup and view all the answers

What is the primary role of inert oil in the Zinc Oxide Eugenol impression material?

To increase the fluidity of the paste Signup and view all the answers

What is the essential component for the hydrolysis of Zinc Oxide to its hydroxide?

Moisture Signup and view all the answers

What happens to the impression compound when it is heated to 45-55°C?

It softens Signup and view all the answers

What is the result of the reaction between Zinc Oxide and Eugenol?

Zinc Eugenolate Signup and view all the answers

What is the purpose of kneading the impression compound outside the water bath?

To avoid leaching out of constituents Signup and view all the answers

Why is it necessary to allow time for cooling during impression taking?

To reduce plastic flow and distortion on removal Signup and view all the answers

What is the effect of adding a drop of water to the Zinc Oxide Eugenol mixture?

Speeds up the setting reaction Signup and view all the answers

What is the characteristic of Type II Impression Compound?

It is a high-fusing impression compound Signup and view all the answers

What is a disadvantage of impression compound?

It has poor thermal conductivity Signup and view all the answers

Why is Type II Impression Compound used as a tray material?

It is sufficiently rigid and has less flow Signup and view all the answers

What is the characteristic of the Zinc Oxide Eugenol impression material that makes it suitable for edentulous patients?

Rigidity Signup and view all the answers

What is the purpose of applying Vaseline paste to the skin around the lips before taking an impression?

To prevent the material from adhering to the skin Signup and view all the answers

What is the characteristic of the Zinc Oxide Eugenol impression material that allows it to accurately register surface details?

Sufficient flow Signup and view all the answers

What is the advantage of using a cool glass slab for mixing the Zinc Oxide Eugenol pastes?

Slower setting reaction Signup and view all the answers

Why should impression compound be poured within one hour?

To minimize distortion Signup and view all the answers

What is a use of zinc oxide eugenol impression material?

Making secondary impressions for edentulous patients Signup and view all the answers

What is a component of zinc oxide eugenol impression material?

Oil of gloves Signup and view all the answers

What is a component of the base paste in zinc oxide eugenol impression material?

Zinc oxide powder Signup and view all the answers

What is a use of sheets of impression compound?

For making special trays Signup and view all the answers

What is a characteristic of impression compound?

High shrinkage on removal from the oral cavity Signup and view all the answers

What is the purpose of the catalyst reactor paste in zinc oxide eugenol impression material?

To act as an accelerator Signup and view all the answers

Study Notes

Zinc Oxide Pastes

Used for making impressions for edentulous patients
Can be used as a surgical pack in periodontal treatments, temporary filling material, surgical pack in dental surgeries, insulating base in deep cavities, temporary relining of dentures, and root-canal filling material
Can be used for occlusal bite registration
Require a non-eugenol containing paste in case of eugenol sensitivity
Where ZnO reacts with carboxylic acid instead of eugenol oil

Properties of Zinc Oxide Pastes

Rigid material, cannot record undercut areas
Adheres to acrylic tray material, no need for adhesive
Adheres to skin around lips, requires Vaseline paste protection
No separating medium required before pouring the cast material
Sufficient flow, accurate registration of surface details
Most dimensionally stable rigid impression material (less than 0.1% shrinkage on hardening)

Manipulation and Setting Reaction of Zinc Oxide Pastes

Equal lengths of each paste mixed on a glass slab or oil-resistant paper pad
Mixing time: 1 minute
Factors controlling setting time: drop of water, high temperature and humidity, smaller particle size of Zinc-oxide powder, prolonged mixing of both pastes, drop of oil, and cool glass slab for mixing
Setting reaction: chelation reaction

Impression Plaster

Used to make secondary impressions for edentulous patients without bony undercut
Powder mixed with water in a rubber bowl, low viscosity and high flow
Hydrophilic, good adaptation to soft tissues, perfect recording of fine details
Setting time: 5 minutes, rigid after setting, cannot record undercut areas
Very good dimensional stability (0.06% change on setting)
Should be used in acrylic special tray (1.5 spacer)
Requires separating medium

Impression Compound

Definition: rigid impression material that sets by a physical reaction, reversible, and thermoplastic
Composition: natural resin and waxes, plasticizer, filler, and coloring agent
Types: Type I (Low-fusing Impression Compound) and Type II (Tray Compound)
Manipulation: sheets inserted in hot water bath, kneaded outside water bath to avoid leaching out of constituents
Setting mechanism: physical process, reversible, changes its physical state by temperature change
Properties: rigid impression material, muco-compressive, high viscosity and low flow, poor thermal conductivity, and poor dimensional stability
Advantages: can be reused several times to correct mistakes and inaccuracies during impression taking

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Description

This quiz tests your knowledge of dental materials, their properties, and various uses in dentistry. Identify the correct uses of different materials in dental treatments.