Dental Impression Materials Quiz

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Questions and Answers

Which property is essential for impression materials to ensure they do not break or tear upon removal from the mouth?

Good dimensional accuracy

Dimensional stability

Elastic properties

Sufficient mechanical strength (correct)

What characterizes thermoplastic impression materials?

They are non-reversible

They soften and harden by heat (correct)

They harden by chemical reaction

They are used only for undercuts

Why are non-elastic impression materials used only when no undercuts exist?

They are cheaper compared to elastic materials

They do not provide sufficient detail

They cannot accommodate changes in shape

They are difficult to remove if undercuts are present (correct)

Which of the following is an example of a reversible impression material?

Impression compounds Signup and view all the answers

Which property is NOT typically fulfilled by any single impression material?

Permanent deformation after strain Signup and view all the answers

Which of the following describes elastic impression materials?

Capable of returning to original shape Signup and view all the answers

What is the primary classification basis for impression materials mentioned?

Method of setting Signup and view all the answers

Which of the following is considered a non-elastic impression material?

Plaster of Paris Signup and view all the answers

What is a notable disadvantage of polysulfide elastomeric impression materials?

Poor patient acceptance due to odor Signup and view all the answers

What is the consequence of losing water as a by-product during the polymerization of polysulfide impression materials?

Reduced dimensional stability Signup and view all the answers

Which type of elastomeric impression material is considered the most flexible?

Polysulfide Signup and view all the answers

What must be done within 30 minutes after removing polysulfide impressions from the oral cavity?

Cast the impressions Signup and view all the answers

What advantage does condensation silicone have over polysulfide materials?

Lower cost Signup and view all the answers

What is the result of having to use custom-made trays for polysulfide materials?

Greater chance of distortion Signup and view all the answers

Which of the following statements is true regarding the disadvantages of polysulfide impression materials?

They can stain clothing Signup and view all the answers

What does the reaction in polysulfide impression materials involve when it interacts with lead oxide?

Production of polysulfide rubber and water Signup and view all the answers

What does a dental impression primarily serve to create?

A negative imprint of the teeth and soft tissues Signup and view all the answers

Which property is NOT desirable in impression materials?

Strong chemical odor Signup and view all the answers

For what reason might dental casts be created?

To plan treatments and construct restorations Signup and view all the answers

Which of the following is a characteristic of ideal impression materials regarding their setting?

They provide a long working time for dental professionals Signup and view all the answers

What type of reproduction is obtained from pouring a dental impression?

Positive reproduction called a dental cast Signup and view all the answers

Which of the following is considered an undesirable property of impression materials?

Releases gas during setting Signup and view all the answers

What is the primary purpose of introducing impression material in an unset condition?

To allow for easy removal post-setting Signup and view all the answers

Which of the following statements about the working and setting time of impression materials is true?

Longer working times allow more flexibility for the dental professional Signup and view all the answers

What is a characteristic of the one-step impression technique?

Both putty and wash materials are mixed nearly simultaneously. Signup and view all the answers

What is a disadvantage of the two-step unspaced impression technique?

It is difficult to reseat the set putty in the mouth. Signup and view all the answers

Which method can create a space for the light wash in a two-step spaced impression?

Applying a polythene spacer over the teeth. Signup and view all the answers

What is a primary advantage of intra-oral scanning over traditional impression methods?

Allows for adjustments to the virtual impression. Signup and view all the answers

What is a major challenge associated with optical impressions?

Start-up costs can be high for the necessary equipment. Signup and view all the answers

In the dual-viscosity impression technique, what role does the high-viscosity material play?

It forces the low-viscosity material into fine details. Signup and view all the answers

Which option is not considered a benefit of intra-oral scanning?

It requires manual adjustment of impressions. Signup and view all the answers

What is a potential consequence of saliva contamination in the two-step unspaced impression technique?

It may prevent the light body wash from adhering properly. Signup and view all the answers

What is the working time of fast set alginate after mixing?

1 minute Signup and view all the answers

How can cooler water affect the setting time of alginate?

It increases the setting time. Signup and view all the answers

What is a significant advantage of using polyether impression materials?

They are hydrophilic and have high dimensional stability. Signup and view all the answers

Which of the following is NOT a use of alginate impression material?

Impression of cavity preparations Signup and view all the answers

What is the best storage condition for alginate impression material to avoid shrinkage?

At 100% relative humidity Signup and view all the answers

Which of the following is a disadvantage of polyether impression materials?

They may cause allergic reactions in some individuals. Signup and view all the answers

Which of the following is an advantage of reversible hydrocolloids like agar?

Good detail reproduction Signup and view all the answers

What characteristic of polyether materials helps in delaying casting?

Their accuracy in dimensional stability. Signup and view all the answers

What is a defining feature of the single-viscosity impression technique?

It involves a medium viscosity material for both filling and syringing. Signup and view all the answers

What equipment is NOT typically needed for manipulating alginate impression material?

A dental drill Signup and view all the answers

What effect does warmer water have on the setting time of alginate?

It shortens the setting time. Signup and view all the answers

Which of the following statements about polyether materials is true?

They are suitable for making impressions with a syringe tray technique. Signup and view all the answers

Which material has largely replaced agar due to its cost and prolonged chair time?

Rubber-based impression materials Signup and view all the answers

What is the main purpose of using dual-viscosity technique?

To allow for more accurate impressions by using two different materials Signup and view all the answers

Why is the cost of polyether materials considered high?

The advanced properties and performance of the materials increase production expenses. Signup and view all the answers

What is a common feature of both the single-viscosity and dual-viscosity impression techniques?

Both techniques can utilize polyether materials for high accuracy. Signup and view all the answers

Study Notes

Introduction to Prosthetic Impressions

A set impression is a negative reproduction of oral tissues.
A positive reproduction is used to recreate the form of teeth and surrounding tissues.
Impression material is placed inside the mouth in a plastic state, maintained in position until set, and then removed.
When poured with dental stone, a positive replication of the mouth ("dental cast") is created.
This process allows for dental work even without the patient present.

Desirable Properties for Impression Materials

Adequate shelf life: Materials should last a reasonable amount of time.
Acceptable odor and taste: The impression material shouldn't have an unpleasant scent or taste.
Biologically acceptable: No toxic or irritating components.
Easily manipulated: Easy to use with minimal equipment is preferred.
Setting characteristics: A suitable working time and setting time are needed. Ideal materials offer longer working times for professionals and minimize setting time for patients.
The material should readily wet oral tissues, not be affected by oral fluids, and avoid releasing gas during setting.
Properties of the set material: Adequate mechanical strength to avoid breakage or tearing during removal. Elastic properties with no permanent deformation after strain, and good dimensional accuracy. Stable over varying temperatures and humidity conditions.

Classification of Impression Materials

Method of setting:
Thermoset: Hardening by chemical reaction (e.g., plaster of Paris, alginates, rubber impressions.). These are irreversible.
Thermoplastic: Softening and hardening by heat (e.g., impression compounds). These are reversible.
Based on setting and elasticity:
Rigid: (e.g., impression plaster, zinc oxide eugenol).
Elastic: (e.g., alginate, polysulfide, polyether, silicone, agar hydrocolloid)
Behavior after setting:
Non-elastic: Used when no undercuts exist (e.g., plaster of Paris, zinc oxide eugenol).
Elastic: Used when undercuts exist (e.g., hydrocolloids, rubber impressions)
Materials:
Waxes: Different types used for various applications.
Plaster: (Plaster of Paris) - a rigid material.
Zinc oxide-Eugenol: A rigid material.
Impression materials: A variety of materials, some in powder form, used to take impressions.
Alginate: An elastic material.
Hydrocolloids: (agar-agar and alginate). These are reversible or irreversible.
Elastomers: (polysulfides, silicones, polyethers). These are chemically cross-linked and have good tear resistance and dimensional stability.
Poly(vinyl siloxanes) are a type of silicone

Impression Materials (Specifics)

Alginate:
Advantages: Ease of mixing, minimal equipment, flexibility, accuracy, low cost.
Disadvantages: Limited detail reproduction, poor dimensional stability, unsuitable for high-accuracy cases (e.g., fixed partial dentures), short shelf life.
Uses: Preparing study casts, creating models, removable partial dentures, athletic mouth protectors.
Storage: 100% relative humidity, to avoid syneresis and imbibition.
Manipulation: Specific equipment (powder/water cups, mixing bowls, spatulas)
Agar:
Advantages: Excellent detail reproduction, well tolerated by patients, good dimensional recovery,
Disadvantages: High setup costs, special equipment needed (temp ranges),
Characteristics: reversible and involves a sol-gel transformation during impression taking.
Elastomers:
Types: Polysulfides, Silicones, Polyethers.
Advantages: High accuracy, great dimensional stability, ease of manipulation, can use undercuts.
Disadvantages: Shrinkage if not cast immediately.
Mixing types: Hand mixing, Static auto mixing, Dynamic mechanical mixing
Impression techniques: Simultaneous dual-viscosity technique, single-viscosity technique, putty-wash technique.
Optical impressions:
Advantages: No need for materials or trays, can be stored digitally, 3D/360-degree view of preparation, and no disinfection required.
Disadvantages: High start-up costs, requires training, and more equipment.
Intra-oral scanning: Modern technique offers a time-saving procedure.

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Description

Test your knowledge on the properties and types of dental impression materials in this informative quiz. Discover essential characteristics, the significance of elasticity, and the unique qualities of different materials used in dentistry. Perfect for students and professionals alike!