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AU17 - Dental Materials 3 > Impression Materials > Flashcards

Impression Materials Flashcards

1
Q

T/F: Good handling properties, transmission of information to models, and reproduction of detail are important characteristics of impression materials.

A

True

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2
Q

Impression materials are divided into what three physical conditions?

A
  1. rigid
  2. plastic
  3. ViscoElastic
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3
Q

ZOE and Plaster are _____ set materials.

A

Rigid

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4
Q

Wax and Compound are _____ set materials.

A

Plastic

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5
Q

Hydrocolloids and Elastomers are _____ set materials.

A

ViscoElastic

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6
Q

T/F: Agar is a reversible hydrocolloid.

A

True

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7
Q

T/F: Alginate is a reversible hydrocolloid.

A

False: alginate is irriversible

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8
Q

Polysulfide, Silicone, and Polyether are what type of impression material?

A

Synthetic Elastomers (ViscoElastic)

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9
Q

T/F: Alginate sets by crosslinking iron ions.

A

False: crosslinked by CALCIUM ions (calcium sulfate dihydrate)

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10
Q

T/F: Positive handling properties of alginate are established by diatomaceous earth.

A

True

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11
Q

Reproduction of detail is determined by _____ and ____ of the impression material.

A

viscosity

wettability

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12
Q

T/F: The contact angle is important for the oral environment and pouring up with gypsum.

A

True

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13
Q

True or False: Alginate has poor dimensional stability.

A

True

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14
Q

Alginate should be poured within _____ minutes.

A

ten

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15
Q

T/F: Agar has a lesser degree of recovery when compared to Alginate.

A

FALSE

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16
Q

T/F: Alginate is more accurate than Agar.

A

FALSE

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17
Q

The greater accuracy of agar is due to the greater degree of _______ around the undercuts of teeth.

A

recovery after deformation

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18
Q

Tear strength is a function of rate of _____.

A

strain

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19
Q

T/F: Polysulfide impression materials are considered to be the new elastic impression material.

A

True

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20
Q

______ is a low molecular weight oligomer that contains reactive mercaptan groups.

A

Polysulfide

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21
Q

T/F: Polysulfide conforms well to a prepared tooth, resulting in good surface detail.

A

True

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22
Q

Polysulfide oxidized by ______ = polysulfide rubber with ___ condensate.

A 
lead dioxide (or copper hydroxide)
water
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23
Q

T/F: For polysulfide to be accurate, the material requires a rigid custom tray for minimal thickness of impression material.

A

True

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24
Q

T/F: Polysulfides do not recover from permanent deformation as well as some other impression materials.

A

True

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25
Q

T/F: Models should be poured as quickly as possible for all impression materials.

A

False, not PVS

26
Q

T/F: Polysulfide is the most expensive elastomer.

A

False (among the least expensive)

27
Q

T/F: You can add additional layers to polysulfide.

A

True, it bonds to itself

28
Q

T/F: Polysulfide shrinkage is reduced due to attachment of the material to the mouth.

A

False, due to attachment to the TRAY

29
Q

T/F: Polysulfide can stain clothing.

A

True

30
Q

T/F: Polysulfide is fast setting.

A

False

31
Q

T/F: Polysulfide tastes good.

A

False

32
Q

T/F: Polysulfide should be poured within 10 mins.

A

False, within 1 hour

33
Q

Polysiloxanes (silicones) are inherently ______ but addition type can be made _____.

A

hydrophobic

hydrophilic

34
Q

T/F: Polysiloxanes are made hydrophilic by the addition of surfactant.

A

True

35
Q

T/F: Polysiloxanes taste better than polysulfides.

A

True

36
Q

What is major consideration in transferring polysiloxane into models?

A

siloxanes can cause voids upon addition of stone slurry

37
Q

T/F: Siloxanes are less stable than alginate or polysulfide.

A

False, more stable

38
Q

T/F: When using condensation silicones, models may be poured any time within a few days.

A

False, pour as quickly as possible, after one hour the dimensional change increases at a constant rate

39
Q

T/F: Condensations silicones taste bad and stain clothing.

A

FALSE, no staining and no objection to tastes

40
Q

T/F: Condensation silicones have poor dimensional stability.

A

True

41
Q

What are the major issues with condensation silicones? (2)

A
  1. stability after cure

2. mixing/handling properties (paste + liquid system)

42
Q

Addition silicones are very ______ _____. Condensation silicones are dimensionally unstable.

A

(+) dimensionally stable

43
Q

PVS is which type of imppresion material?

A

Addition silicone

44
Q

T/F: PVS is a two part system.

A

True, the spiral tips mix it up and allow for hydrosilation reaction to produce chain lengthening and cross linking

45
Q

Why should you wait before pouring PVS impressions?

A

the secondary reaction produces hydrogen, all hydrogen should be liberated before pouring the models… would cause bubbles!

46
Q

T/F: The working time of PVS can be lengthened.

A

True, by addition of a retarder

47
Q

T/F: Polyethers are hydrophilic.

A

True

48
Q

T/F: Polysiloxanes are hydrophobic.

A

True

49
Q

T/F: Polyethers taste bad.

A

True

50
Q

When using polyether, contact of the unmixed ester with skin or mucosa could cause ____.

A

contact dermatitis

51
Q

T/F: Polyether requires a custom tray.

A

True

52
Q

Polyether is difficult to remove from _____.

A

undercuts

53
Q

What are the four requirements of “ideal” impression materials?

A
  1. low cost
  2. long shelf life
  3. biocompatibility
  4. pleasant to patient
54
Q

Which impression materials have good wetting on moist oral structures (low contact angle, easy to pour)?

A

agar
alginate
polysulfide

55
Q

Which impression materials have fair/good wetting (aka ease of pouring)?

A

condensation silicone
addition silicone
polyether

56
Q

Which material has the highest tear strength?

A

Polysulfide

57
Q

Vinylsiloxane ether (VSE) is a new material that incorporates aspects of two materials to make a better impression. The _____ component acts as a surfactant.

A

polyether
(polyethers are hydrophilic)
“ethers like water”….to remember, think “i like Easter”

58
Q

T/F: Both traditional and digital impression will produce clinically acceptable crowns.

A

True

59
Q

T/F: There is a greater margin of error with digital impressions.

A

True

60
Q

T/F: Prostheses fabricated from digital impressions showed fewer gaps in the occlusal surfaces.

A

False, MORE gaps

61
Q

In the additive printing process, a slurry of zirconia and dispersants are ____ at 1450 Celsius.

A

sintered

  • the slurry is extruded and gelled
    (aka: make a powdered material coalesce into a solid or porous mass by heating it, and usually also compressing it, without liquefaction)
62
Q

T/F: 3D printing can be used in dentistry for surgical guides, wax ups, models, and methacrylate based resins (provisionals).

A

True

AU17 - Dental Materials 3 (6 decks)

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