Impression Materials In Dentistry Question And Answers

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Impression Materials Important Notes

1. Classification of impression materials

  • Based on setting mechanisms
    • Chemical reaction
      • Plaster of Paris — Zinc oxide eugenol
      • Alginate
      • Nonaqueous elastomers
    • Thermally-induced physical reaction
      • Compound wax
      • Agar
  • Based on elasticity
    • Rigid materials
      • Plaster of Paris
      • Zinc oxide eugenol
      • Compound
  • Elastic material
    • Agar
    • Alginate
    • Non-aqueous elastomers

2. Types of elastomers

Impression Materials Types Of Elastomers

3. Addition silicone

  • They are type II silicone impression materials
  • They undergo an additional type of polymerization terminating in vinyl groups and cross-linked with hydride group
  • They have very little residual polymerization
  • Thus it is the most dimensionally stable
  • It is highly biocompatible
  • Addition silicone Advantages:
    • Dimensionally stable
    • Adequate tear strength
    • Pleasant odor and color
    • Multiple casts can be made from one impression
    • No volatile byproduct
  • Addition silicone Disadvantage
    • Impurities evolve hydrogen gas
    • This hydrogen gas produces pinpoint voids in the stone casts if poured immediately
    • It is prevented by
      • adding platinum or palladium
      • by delaying the pouring of impression

4. Composition of polyether impression material

Impression Materials Composition Of Polyether Impression Material

5. Impression techniques

  • Multiple mix technique
    • Two separate mixes are made
    • Heavy body material is placed in the tray
    • Light body is loaded in a syringe
    • Impression is made

Read And Learn More: Dental Materials Question and Answers

  • Single mix
    • Only one mix is made
    • Medium body material is used
    • Part of it is loaded in a tray and part is loaded in a syringe
    • Impression is made

6. Causes of the rough surface of elastomers

  • Incomplete polymerization caused by premature removal from the mouth
  • The improper ratio of mixing components
  • Too rapid polymerization caused by high humidity and high temperature

Impression Materials

Impression Materials Long Essay

Question 1. State the properties and uses of rubber-based materials
Answer:

Rubber Based Materials:

Rubber Based Materials Synonyms:

  • Rubber impression materials
  • Elastomeric impression materials

Rubber Based Materials Properties:

  • They are accurate impression material- they excellently reproduce the surface details
  • They are dimensionally stable
  • Available in various viscosity
  • The low viscosity is capable of reproducing even very fine details
  • They are generally hydrophobic
  • Resilience
  • They are flexible with near-complete elastic recovery
  • Its coefficient of thermal expansion Is high
  • It cannot melt, before melting they pass Into a gaseous state
  • They swell In the presence of certain solvents
  • They are Insoluble
  • They have lower creep resistance
  • Tear strength is excellent
  • They can be electroplated
  • As they don’t adhere well to the Impression tray, tray adhesive is used
  • It has a shelf life of about two years
  • It may cause dimensional changes due to
  1. Curing shrinkage
  2. Loss of byproducts
  3. Hydrophilic nature
  4. Thermal contraction
  5. Delayed pouring of cast

Rubber Based Materials Uses:

  • In fixed partial dentures for Impressions of prepared teeth
  • Impressions of dentulous mouths for removable partial dentures
  • Impressions of edentulous mouths for complete dentures
  • Polyether Is used for border molding
  • For bite registration
  • Silicon Is used for making refractory casts

Question 2. Advantages and disadvantages of elastomeric Impression material
Answer:

Advantages and disadvantages of elastomeric Impression material

Impression Materials Advantages And Disadvantages Of Elastomeric Impression Material

Question 3. What are elastomers? Write in detail about the types, composition, properties, and manipulation of additional silicone impression material.
Answer:

Elastomers:

  • It is a lightly cross-linked impression material that exhibits elastic behavior after setting.
  • It refers to a group of rubbery polymers, which are either chemically or physically cross-linked

Addition Silicones:

Addition Silicones Types:

  • It is available in four viscosities
  • Light bodied
  • Medium bodied
  • Heavy bodied
  • Putty

Addition Silicones Composition:

Impression Materials Addition Silicones Composition

Addition Silicones Properties:

Impression Materials Addition Silicones Properties

  • Setting time-5-9 minutes
  • Mixing time- 45 seconds
  • Shelf life-1 to 2 years

Manipulation:

1. For the paste

  • Dispense equal length of base and catalyst over a mixing pad
  • Incorporate first the catalyst into the base
  • Mixing is done by moving the spatula back and forth on the mixing pad
  • The process is continued until the mixed paste is uniform in color with no streaks of the base or catalyst

2. For putty

  • An equal number of scoops of each putty is dispensed
  • Material is then kneaded with fingers until a uniform color is obtained

Question 4. Classify impression materials and describe in detail about contents, setting, and properties of silicone rubber base impression materials
Answer:

Classification:

1. Based on setting mechanisms

  • Chemical reaction
    • Plaster of Paris
    • Zinc oxide eugenol
    • Alginate
    • Nonaqueous elastomers
  • Thermally-induced physical reaction
    • Compound wax
    • Agar

2. Based on elasticity

  • Rigid materials
    • Plaster of Paris
    • Zinc oxide eugenol
    • Compound wax
  • Elastic material
    • Agar
    • Alginate
    • Nonaqueous elastomers

Silicon Rubber Based Materials:

Silicon rubber-based materials are

  1. Condensation silicone
  2. Addition silicone

Impression Materials Silicon Rubber Based Materials

Impression Materials Short Essays

Question 1. What are nonaqueous elastomers and write any one of its composition?
Answer:

Nonaqueous Elastomers:

Nonaqueous elastomers are

  1. Polysulphides
  2. Polyether
  3. Condensation silicone
  4. Addition Silicones

Impression Materials Addition Silicone

Question 2. Ideal requirements of Impression materials
Answer:

Ideal Requirements:

  • They should be fluid enough to adapt to oral tissues
  • Should be viscous enough to be contained in the tray that is seated in the mouth
  • While in the mouth, they should set into a rubbery or rigid solid in a reasonable amount of time
  • The set impression should not tear or distort when removed
  • The impression made should be dimensionally stable
  • Stability should be maintained after the removal of a cast so that a second or third cast can be made
  • The material should be biocompatible
  • It should be cost-effective
  • Should be nontoxic
  • Should be acceptable to patients with pleasant odor and color
  • Should have an adequate shelf life
  • Easy to use with minimum equipment
  • Should have adequate strength
  • Should be compatible with the die and cast materials
  • Should be able to be electroplated

Question 3. Polysulphides
Answer:

Polysulphides

Polysulphides were the first elastomeric impression material to be introduced

Polysulphides Advantages:

  • Long working time
  • High tear resistance
  • Margins easily seen
  • Cheaper
  • Excellent surface reproduction
  • Good flexibility
  • Good shelf life
  • Can be electroplated

Polysulphides Disadvantages:

  • Unpleasant odor and color
  • Messy to work
  • Extremely viscous and sticky
  • Exhibit pseudo plasticity
  • High shrinkage occurs
  • Hydrophobic

Polysulphides Composition:

  • Base
    • Liquid polysulfide polymer
    • Inert fillers
  • Reactor
    • Lead dioxide
    • Dibutyl phthalate
    • Sulfur
    • Other substances like magnesium stearate and deodorants

Question 4. Elastomers
Answer:

Elastomers

  • A lightly cross-linked impression material that exhibits elastic behavior after setting is called elastomer
  • They contain large molecules with weak Interaction between them
  • They are liquid polymers that can be converted to solid rubber at room temperature

Elastomers Types:

1. According to chemistry

  • Polysulphides
  • Condensation silicone
  • Addition silicone
  • Polyether

2. According to viscosity

  • Light body
  • Medium body
  • Heavy body
  • Very heavy body

3. According to elasticity

  • Type 1
  • Type 2
  • Type 3

4. According to wettability

  • Hydrophilic
  • Hydrophobic

Elastomers Uses:

  • In fixed partial dentures for impressions of prepared teeth
  • Impressions of dentulous mouths for removable partial dentures
  • Impressions of edentulous mouths for complete dentures
  • Polyether is used for border molding
  • For bite registration
  • Silicon is used for making refractory casts

Question 5. Reline technique for elastomeric impression
Answer:

Reline technique for elastomeric impression

  • Reline technique is also called the two-stage putty wash technique
  • It is used to minimize the effect of Polymerisation shrinkage

Elastomeric impression Technique:

  • The thick putty material is made using a stock tray
  • Results in preliminary impression
  • Spacing is provided by either
    • Cutting away some of the tray putties or
    • Using a thin polyethylene sheet between putty and prepared tooth
  • The mix of thin consistency wash material is placed into putty
  • Putty wash and tray are seated into the mouth
  • The final impression is made

Question 6. Condensation silicon
Answer:

Condensation silicon

Condensation silicone is one of the silicone impression material

Condensation silicon Composition:

1. Base

  • Polymethyl siloxane
  • Colloidal silica
  • Color pigments

2. Accelerator

  • Orthoethyl silicate
  • Stannous octoate

Condensation silicon Advantages:

  • Putty for custom trays
  • Clean and pleasant
  • Good working time
  • Easily seen margins
  • Pleasant color and odor
  • Can be electroplated

Condensation silicon Disadvantages:

  • Curing shrinkage
  • Less shelf life
  • Hydrophobic

Impression Materials Short Question And Answers

Question 1. Rubber-based impression material
Answer:

Rubber-based impression material

  • It is a lightly cross-linked impression material that exhibits elastic behavior after setting.
  • It refers to a group of rubbery polymers, which are either chemically or physically cross-linked

Rubber-based impression material Uses:

  • In fixed partial dentures for impressions of prepared teeth
  • Impressions of dentulous mouths for removable partial dentures
  • Impressions of edentulous mouths for complete dentures
  • Polyether is used for border molding
  • For bite registration
  • Silicon is used for making refractory casts

Question 2. Addition silicone
Answer:

In addition, silicone is the most widely used impression material

Addition silicone Advantages:

  • Pleasant odor and color
  • Excellent surface reproduction
  • Dimensionally stable
  • Good tear strength
  • Can be electroplated

Addition silicone Disadvantages:

  • Cause allergic reactions
  • Hydrophobic
  • Less flexible
  • Extra spacing require in impression trays

Question 3. Cross-linking
Answer:

Cross-linking

The joining of polymer chains to form a three-dimensional network structure is called cross-linking

Question 4. Polyether
Answer:

Polyether

  • Polyether was introduced in Germany
  • It has good mechanical properties and dimensional stability

Polyether Advantages:

  • Fast setting
  • Clean
  • AutomLx dispense
  • Easily seen margins
  • Good stability
  • Hydrophilic
  • Can be electroplated

Polyether Disadvantages:

  • Cause allergic reactions
  • Heat decreases the setting time

Question 5. Tray adhesives.
Answer:

Tray adhesives

  • Tray adhesives are tacky liquids that are applied with a brush
  • They are used to obtain the most accurate impression possible by adhering impression material to the tray
  • It is advisable to use tray adhesive on all trays before making an impression
  • Each elastomer has a specific adhesive

Tray adhesives Method of application:

  • Apply a thin layer of tray adhesive to the tray using the applicator brush
  • Allow to dry for at least 3 minutes
  • Load the tray with impression material
  • Make an impression

Question 6. Multiple mix impression technique of elastomers.
Answer:

Multiple mix impression technique of elastomers

  • Two separate mixes are made
  • Heavy body material is placed in the tray
  • Light body is loaded in a syringe
  • Impression is made

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