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Semester 2 Dental Materials > Chapter 9 Quiz 3 > Flashcards

Chapter 9 Quiz 3 Flashcards

1
Q

a mineral ground and heated to drive out water particles through a process called calcination

A

gypsum

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2
Q

what is gypsum in a powder form

A

calcium sulfate hemihydrate

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3
Q

what is gypsum powder mixed with to form a slurry that can be poured and shaped and will harden into a rigid mass

A

water

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4
Q

gypsum is mainly used for ___________ reproductions of oral structures that are obtained from a negative mold

A

positive

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5
Q

used to treatment plan and to observe treatment progress

A

study model

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6
Q

replica of a restoration or applicance

A

cast

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7
Q

a working replica of a single tooth

A

die

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8
Q

what are the three types of gypsum used in dentistry

A

plaster
stone
high strength/improved stone

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9
Q

gypsum rock is made of __________

A

calcium sulfate dihydrate

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10
Q

when gypsum rock is heated or __________, it becomes calcium sulfate _________ in its powdered form

A

dehydrated
hemihydrate

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11
Q

calcium sulfate hemihydrate can be turned into

A

alpha calcium sulfate hemihydrate or beta calcium sulfate hemihydrate

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12
Q

porous; weakest; least wear resistant; cheapest; white in color

A

plaster type II

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13
Q

what are plasters often used for

A

preliminary casts

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14
Q

what can plasters be attached to to simulate occlusion

A

articulator

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15
Q

what is the composition of plaster

A

B-hemihydrate (requires more H2O=weaker)

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16
Q

stronger and more expensive; light tan color

A

stone (type III)

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17
Q

what is the composition of stone

A

a-hemihydrate (requires some water=pretty strong)

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18
Q

stones are used for what

A

diagnostic casts,
casts for denture construction,
retainers,
aligners, and
custom trays

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19
Q

dense; strongest; most wear resistant; most expensive

A

high-strength/improved stone (type IV)

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20
Q

what is the composition of high-strength/improved stones

A

a-hemihydrate

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21
Q

what are high-strength/improved stones used for

A

casts/dies,
crown,
bridge,
and inlay fabrication

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22
Q

the more water needed in gypsum, the ________ the setting expansion and the ___________ the compressive strength of the final product

A

greater
lower

23
Q

because beta-calcium sulfate hemihydrate requires _______ water to reconstitute than the alpha-hemi-hydrate, it undergoes a __________ expansion and therefore has a _______ compressive strength compared to the alpha

A

more
greater
lower

24
Q

the proportion of water to powder used to make a workable mix of a particular gypsum product

A

water-powder ratio

25
Q

the water-powder ration depends on the type of _______

A

powder

26
Q

plaster requires more or less water

A

more = thinner

27
Q

improved stones require more or less water

A

less = thicker

28
Q

water-powder ratio of plaster

A

45-50mL/100g

29
Q

water-powder ration of stone

A

28-30mL/100g

30
Q

water-powder ratio of improved stone

A

19-24mL/100g

31
Q

which gypsum material is not too thin and not too thick

A

stone

32
Q

length of time from the start of the mix until the setting mass reaches a semi-hard stage

A

working time (initial setting time)

33
Q

length of time from the start of the mix until the setting mass becomes rigid and can be separated from the impression

A

final setting time

34
Q

how long is final setting time

A

30-45 minutes

35
Q

increase setting time so that it takes longer for the product to set

A

retarders

36
Q

what increases working time

A

retarders

37
Q

decrease setting time so that the product sets up faster

A

accelerators

38
Q

what will decrease the working time

A

accelerators

39
Q

all gypsum products expand ______ when they set

A

externally

40
Q

expansion is controlled by the addition of ________ and by proper mixing techniques

A

chemicals

41
Q

strength depends on the ______ of the material and is developed in the first 30-45 minutes of setting

A

porosity

42
Q

set gypsum is stable under normal conditions, but highly soluble in ________

A

water

43
Q

how long should you spatulate stone mixtures

A

30 seconds

44
Q

what does the vibrator do

A

remove air bubbles

45
Q

where should you place the stone from on the impression

A

distal to the last molar

46
Q

pile the remainder of material on top of the impression to cover all areas by about ________ inches

A

0.25

47
Q

allow gypsum mix to reach initial set which takes about _________ minutes and is evident by a loss of gloss

A

10

48
Q

how many mL of gypsum mix go into the base of the model

A

36 mL

49
Q

how thick should the paddy of the base be

A

1 inch

50
Q

where should the stone material NOT touch

A

on the plastic or metal tray

51
Q

how long should you wait before removing the cast from the impression

A

45-60 minutes

52
Q

_________ mL H2O per bag of stone to fill impression

A

38-40

53
Q

________ mL H2O per bag of stone for paddy

A

36-38

Semester 2 Dental Materials (8 decks)

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