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Pres/Res > Gypsum > Flashcards

Gypsum Flashcards

1
Q

model

A

a + likeness of an object

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2
Q

How gypsum is made

A

calcination-process of heating a solid will drive off volatile chemically combined components (i.e. water)

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3
Q

varying amts of heat

A

different products

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4
Q

Dihydrate

A

starting product2CaSo4.2H20

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5
Q

Beta Hemihydrate

A

plaster, irregular shape, spongy, more water

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6
Q

Alpha Hemihydrates

A

regular shape, dense, less water than beta

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7
Q

die stone

A

modified alpha hemihydrate, shorter and thicker crystals, less water than stone for mixing, higher strength than stone

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8
Q

mixing time mechanical

A

20-30 s

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9
Q

hand mix time

A

1 min

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10
Q

setting time, how to know intitial set

A

when the light-Gilmore needle can barely penetrate mixture

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11
Q

final setting determiner

A

barely a mark left by heavy gilmore needle

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12
Q

increase water/powder ratio

A

increased setting time, decreased strength, decreased setting expansion

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13
Q

longer vigorous mix means

A

shorter setting time

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14
Q

warm water

A

shorter setting time-erratic

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15
Q

chemical accelerants

A

Potassion S, NaCL, NaS, Borax

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16
Q

Borax

A

chemical accelerant which accelerates at low c and retards at high c

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17
Q

slurry water

A

provides additonal seeds of nucleation

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18
Q

setting expansion mech

A

crystal of dihydrate is an outgrowth, can intermesh and obstruct growth of adj crystals, excess water during drying –> porous

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19
Q

excess water loss during drying

A

porous structure

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20
Q

hydroscopic setting expansion

A

expansion that occurs when gypsum sets while immersed in water, 2x normal expansion, crystals grow more freely

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21
Q

wet strength

A

=green strength, less

22
Q

dry strength

A

st. when all excess water is used, 2-3 times of wet st.

23
Q

increase W/P ration

A

decrease st. (strength)-fewer hydrate crystals per unit V

24
Q

spatulation

A

increaed mixing time increases st.

25
Q

overmixing

A

dec st.-dec crystal interlocking

26
Q

inc mixing time

A

inc. st.

27
Q

type I gypsum

A

impression plaster, impressions and occlusal records-OBSOLETE-Runny

28
Q

Type II

A

Model plaster, study models, denture flasking, not used much

29
Q

Type III

A

dental stone, working casts and mounting on articulators

30
Q

IV

A

High st. dental stone and low expansion-for wax patterns-used often

31
Q

V

A

High st high expansion dental stone-dies for cast restirations w/ high casting shrinkage

32
Q

Mounting Stone

A

faster setting, low expansion, lower strength, altered type III

33
Q

Manipulation of Gypsum

A

storage, mL water, and stone powder in weight (grams)

34
Q

mixing by hand

A

parabolic bowl, stiff spatula, water into bowl, powder sifter onto water, mix 1 min (longer mix dec working time), reduce air entrapment (bubbles) by high frequency/low amplitude vibration

35
Q

longer mixing time for gypsum

A

dec working time

36
Q

mechanical mix

A

mix water and powder, stir, mix in vacuum, vibrate, attach hose and mix, take of lid, vibrate with lid just barely on, RINSE LID!! Vibrate on smaller machine while you put in each tooth slowly

37
Q

mechanical mix/pouring of an impression

A

mix water and powder, stir, mix in vacuum, vibrate, attach hose and mix, take of lid, vibrate with lid just barely on, RINSE LID!! Vibrate on smaller machine while you put in each tooth slowly, clean bowl out in garbage and sink

38
Q

T/F can use normal infetion control on cast?

A

True

39
Q

store above 130?

A

no

40
Q

gypsum composoition

A

Calcium sulfate dihydrate

41
Q

Add hardness to home water

A

gypsum

42
Q

Gypsum product uses in dentistry

A

diagnostic/models, working models, dies, mounting casts, denture processing, metal casting

43
Q

impression

A

a negative replica of the oral cavity

44
Q

a negative replica of the oral cavity

A

impression

45
Q

a positive likeness of an object

A

model

46
Q

Diagnostic study casts are useful for

A

Evaluating dentition
Treatment planning
Patient education
Tracking Progress of otho/pros

47
Q

a reproduction of a prepared tooth made from gypsum, metal, or refractory material

A

die

48
Q

110 to 130 degrees calcination product

A

Plasters and stone (calcium sulfate hemihydrate)

49
Q

130 to 200 degrees C calcination product

A

hexagonal anhydrite

50
Q

200 to 1000 degrees calcination product

A

orthothrombic anhydrite

Pres/Res (14 decks)

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