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Flashcards in Test review Deck (65)
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1
Q

T/F Polysulfide is accurate but not stable compared to other elastomers because of its biproduct

A

True

2
Q

Which elastomers can be poured multiple times with reasonable accuracy?

A

PVS

Polyether

3
Q

What is the stiffest of the elastomers

A

Polyether

4
Q

What has the best tear strength of the elastomer

A

Polysulfide

5
Q

What is the second best tear strength of the elastomer

A

PVS

6
Q

Why don’t we use alginate for all of our impressions?

A

-Alginate doesn’t reproduce fine detail well even though it is an accurate impression

7
Q

T/F Polysulfide doesn’t smell very good

A

True

8
Q

Which elastomer doesn’t taste very good?

A

-Polyether

9
Q

What are the two variables that relate to create distortion in impression material?

A
  • Time

- Compression

10
Q

What principles deal with elastic recovery?

A
  • Time

- Compression

11
Q

How long does it take alginate to rebound (elastic recovery)?

A

8 - 10 minutes

12
Q

How much is an alginate compressed during removal?

A

10%

13
Q

How do we decrease the amount of time alginate is compressed during removal?

A

-Snap it out (get air into vestibule)

14
Q

which temporary material has a higher exotherm?

A

-Polymethylmetacrylate

15
Q

Which temporary material shrinks more?

A

-Polymethylmethacrylate

16
Q

What properties make polymethylmethacrylate desirable?

A
  • Great fracture toughness
  • Not brittle
  • Easily added to (modify its shape easily)
17
Q

What can unifast do that others can’t?

A

Light curable so you can control the set.

18
Q

T/F Polyethylmethacrylate (SNAP) is soft

A

True

19
Q

Would you want to use polyethylmethacrylate for anything other than a single unit?

A

No

20
Q

What is one method to take a gypsum stone die reinforced and stronger to be more resistant to abrasion?

A

-Low viscosity cyanoacrylate (basically super glue)

21
Q

T/F Calciumsulfatedihydrate is mined out of the ground

A

-True

22
Q

What type of stone is densate used to make?

A

-Type IV and Type V

23
Q

What type of stone is hydrocal used to make?

A

-Type III

24
Q

What is the most refined form of gypsum?

A

-Calciumsulfatehydrite

25
Q

What is the most refined form of gypsum?

A

-Calciumsulfatehydrite

26
Q

What are the two most common ways to manufacture ceramic crowns?

A
  • Milled

- Heat pressed ceramic (EMAX/llithium disilicate)

27
Q

Zirconia is so hard it is milled in its green state?

A

Yes

28
Q

Zirconia is in a pre-sintered (green state/larger form) and then is heated, what happens when it is heated (sintered)?

A

-It shrinks

29
Q

If the light body is in the setting phase and then you insert the heavy body what happens to your bite record?

A

-It is inaccurate (open)

30
Q

If the heavy body material is starting to set but the light body is still fine what happens when you insert the heavy body?

A

-The die will shrink or be smaller

31
Q

What are the two biggest draw backs of hydrocolloids?

A
  • Imbibition

- syneresis (sweating)

32
Q

Dental stone casts reach their maximum strength after how many hours?

A

24 hours

33
Q

What does the modulus of elastisitity define?

A

-The stiffness of a material

34
Q

What material has the highest elastic modulus?

A

-Polyether

35
Q

Clinically the resistance and retention form are satisfied, where is the most ideal place to put your margins with respect to the gingiva (esthetics is not a factor because it is the back of the mouth?

A

-1 mm above the gingiva (.5 mm pre clinically)

36
Q

Clinically the resistance and retention form are satisfied, where is the most ideal place to put your margins with respect to the gingiva (esthetics is not a factor because it is the back of the mouth?

A

-1 mm above the gingiva (.5 mm pre clinically)

37
Q

What is alginate made from?

A

-Potassium alginic salts from seaweed

38
Q

If you under-reduce occlusaly what are consequences?

A
  • Material to thin

- Over contouring by the lab

39
Q

If you don’t have enough axial reduction what are the consequences?

A
  • Margins to thin
  • Over contoured axial crown
  • Create plaque trap with final crown
40
Q

If you increase taper do you increase or decrease resistance and retention?

A

-Decrease in both

41
Q

If you increase the surface area do you increase or decrease resistance and retention?

A
  • Increase retention

- Doesn’t always increase resistance

42
Q

What will the final marginal gap be if everything is perfect (done with the lost wax technique)?

A

-10 microns

43
Q

What three things always should be taken into consideration when doing a preparation?

A
  • Biological
  • Esthetics
  • Mechanical
44
Q

Why don’t we want you to use a posterior plastic bite tray in the clinic?

A

-They can bend

45
Q

Which impression materials can have their setting interfered with latex gloves?

A

-Addition PVS (sulfur in the latex)

46
Q

Which impression materials can have their setting interfered with latex gloves?

A

-Addition PVS (sulfur in the latex)

47
Q

Why is important to capture the area apical to the margin?

A
  • Makes it easier to trim and find the margin

- Helps make contours

48
Q

When impressions are set and done what do you want to avoid?

A
  • Extremes of temperature

- Extremes that cause distortion

49
Q

What are the main things you are trying to capture in your crown impression?

A
  • Die
  • Prepared tooth
  • Opposing anatomy
  • Occlusion
  • Good adjacent tooth surfaces
50
Q

What are some of the ways the impression material is kept adherent to trays?

A
  • Perforation
  • Rim lock
  • Adhesive sprays
51
Q

T/F Double sided mouth mirrors are a good retractor and a good visualizer

A

True

52
Q

Name some hemostatic chemicals?

A
  • Ferric sulfate
  • Epinephrine
  • Aluminum chloride
53
Q

Why do we use retractions cord?

A
  • Displace soft tissue temporarily

- Carrier of hemostatic agent

54
Q

T/F Retraction cord can be braided or woven

A

True

55
Q

What is the situation where you have to be careful using epinephrine as a hemostatic agent?

A
  • Heart problems

- Lacerated tissues can cause tachycardia

56
Q

How many ADA recognized gypsum types are there?

A

-5 types

57
Q

What is calcination?

A

-Process of driving water off of gypsum products during refinement process

58
Q

What type of stones are the hardest stones?

A
  • Type IV

- Type V

59
Q

Which stone is really hard and expands a lot?

A

-Type V

60
Q

What is the advantage of vacuum mixing stone?

A
  • Remove air bubbles
  • Harder set stone
  • More dense set stone
  • More abrasive resistant stone
61
Q

Which type dental stone exhibits the least amount of expansion?

A

-Type I MOUNTING Stone

62
Q

What is the Centrum?

A

-Cuspal tip against a flat surface at MI

63
Q

What is tripodisation?

A

-The mountain engages the valley near the tip but not directly at the tip. Need to have equal contact between the three points or else teeth will move

64
Q

What is the order that you place your models in the 3 M scanner

A

1) preparation arch
2) opposing arch
3) together
4) Die

65
Q

Where is the buccal placed in the scanner?

A

-The back