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Dental Materials > Non Elastic Impression Pt. 2 > Flashcards

Non Elastic Impression Pt. 2 Flashcards

1
Q

Name nonelastic impression materials

A
  1. Impression plaster
  2. impression compound
  3. zinc oxide eugenol impression paste
  4. compression waxes
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2
Q

Name the components of impression plaster

A
  1. Main ingredient - beta calcium sulphate hemi hydrate
  2. anti-expansion agent - potassium sulphate
  3. retarder - borax
  4. pigment - Alazarin red 
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3
Q

What are the manipulative variables of impression plaster

A
  1. High water powder ratio
  2. special tray
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4
Q

What are the advantages of impression plaster

A
  1. Mucostatic impression technique
  2. Hydrophilic
  3. Accuracy
  4. Minimal dimensional change
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5
Q

What are the disadvantages of impression plaster

A
  1. Dryness of mouth
  2. Very brittle
  3. not suitable for recording undercuts
  4. difficult to remove
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6
Q

How do you disinfect impression plaster

A

10 minutes soaked in 10% sodium hypo chlorite solution

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7
Q

What’s the use of impression plaster

A

patients with excessively mobile soft tissues overlying the residual alveolar bone

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8
Q

Which nonelastic impression materials are thermoplastic

A
  1. Impression compound
  2. Impression waxes
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9
Q

What is the function of filler in impression compound

A
  1. increasing viscosity of the softened material
  2. reduces thermal contraction
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10
Q

What is the function of lubricant in impression compound

A

Improves flow properties

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11
Q

What is the composition of impression compound

A
  1. Thermal plastic material 47% natural or synthetic raisins and waxes
  2. filler 50% Talc
  3. Lubricant 3% stearic acid
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12
Q

What are the uses of the different types of impression compounds

A
  1. Type one- low fusing and medium fusing: Used as impression material, Border extension and single crown impression
  2. Type two - higher fusing: used to construct impression trays
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13
Q

What is copper ring technique

A

It is use from making an impression of a single crown. Copper tube is used. It’s places around the tooth and acts as a tray. Type one impression compound is softened and pressed over the tooth in the ring. electroform dies

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14
Q

What are the factors affecting performance of impression compound Sheet form during manipulation

A
  1. Conditioning temperature
  2. time of conditioning in water bath
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15
Q

What is the ideal conditioning temperature for impression compound sheet form

A

55 to 60°C

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16
Q

What are the properties of impression compound

A
  1. Flow
  2. Viscosity
  3. rigidity
  4. poor Elastic properties
  5. Cannot be used for undercuts
  6. large value of coefficient of thermal expansion
17
Q

What are the three factors that combine to produce significant internal stress is within the impression compound

A
  1. High value of coefficient of thermal expansion
  2. poor thermal conductivity
  3. high temperature drop from softening temperature room temperature
18
Q

What is the composition of zinc oxide eugenol paste one

A
  1. Zinc oxide
  2. olive oil, linseed oil or equivalent
  3. zinc acetate
  4. water
19
Q

What is the composition of paste two zinc oxide eugenol 

A
  1. Eugenol (oil of cloves)
  2. Kaolin, talc or equivalent
20
Q

What is the function of zinc acetate and water in zinc oxide eugenol 

A

To accelerate setting

21
Q

What is the function of kaolin/ talc in zinc oxide eugenol paste

A

Inert filler used to make a paste

22
Q

How do you Accelerate the setting reaction of zinc oxide eugenol 

A
  1. Increasing temperature
  2. increasing humidity
  3. Presence of water and certain ionizable salts
  4. Speculation time (the longer the paste is mixed the quicker it will set)
23
Q

What is the nature of the setting reaction of zinc oxide eugenol?

A

Ionic

24
Q

What are the properties of zinc oxide eugenol 

A
  1. Low viscosity
  2. pseudo plastic nature
  3. Easy manipulation
  4. rigid
  5. good dimensional stability
25
Q

What are the disadvantages of zinc oxide eugenol

A
  1. Allergies to eugenol
  2. Distort or fracture when remove from undercuts
  3. lack of elasticity
  4. Sticky and adheres to tissues
  5. only sets quickly in thin sections
  6. requires a special tray
26
Q

What are the applications of nonelastic impression materials

A
  1. No undercuts
  2. Edentulous patients
27
Q

Which Nonelastic impression material is reversible

A

Impression compound

28
Q

What are the advantages of impression Compound

A
  1. Non-irritant and nontoxic
  2. reusable in the same patient
  3. can be reheated and re adopted
  4. support other materials for wash impression
  5. can be electroplated
29
Q

What are the disadvantages of impression compound

A
  1. Poor Surface detail
  2. distortion occurs when removed from undercuts
  3. poor dimensional stability
30
Q

What are the uses of zincoxide eugenol impression pastes 

A
  1. Impressions of EDENTULOUS ridges
  2. bite registration
  3. spotting denture sore spots
  4. fixing occlusal blocks during jaw relation. 
31
Q

What is the water: powder ratio for impression plaster

A

50 to 60 ml :100 mg

32
Q

What is the percentage of expansion that occurs when impression plasters mix with water.
What will be the percentage when mixed with anti-expansion solution

A

0.3% to 0.6%
0.05%

33
Q

Which Non-elastic impression material is mucostatic 

A

Impression plaster
Impression wax

Dental Materials (4 decks)

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