Chapter 9 Quiz 3

Question 1

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

Answer 1

gypsum

Question 2

what is gypsum in a powder form

Answer 2

calcium sulfate hemihydrate

Question 3

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

Answer 3

water

Question 4

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

Answer 4

positive

Question 5

used to treatment plan and to observe treatment progress

Answer 5

study model

Question 6

replica of a restoration or applicance

Answer 6

cast

Question 7

a working replica of a single tooth

Answer 7

die

Question 8

what are the three types of gypsum used in dentistry

Answer 8

plaster
stone
high strength/improved stone

Question 9

gypsum rock is made of __________

Answer 9

calcium sulfate dihydrate

Question 10

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

Answer 10

dehydrated
hemihydrate

Question 11

calcium sulfate hemihydrate can be turned into

Answer 11

alpha calcium sulfate hemihydrate or beta calcium sulfate hemihydrate

Question 12

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

Answer 12

plaster type II

Question 13

what are plasters often used for

Answer 13

preliminary casts

Question 14

what can plasters be attached to to simulate occlusion

Answer 14

articulator

Question 15

what is the composition of plaster

Answer 15

B-hemihydrate (requires more H2O=weaker)

Question 16

stronger and more expensive; light tan color

Answer 16

stone (type III)

Question 17

what is the composition of stone

Answer 17

a-hemihydrate (requires some water=pretty strong)

Question 18

stones are used for what

Answer 18

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

Question 19

dense; strongest; most wear resistant; most expensive

Answer 19

high-strength/improved stone (type IV)

Question 20

what is the composition of high-strength/improved stones

Answer 20

a-hemihydrate

Question 21

what are high-strength/improved stones used for

Answer 21

casts/dies,
crown,
bridge,
and inlay fabrication

Question 22

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

Answer 22

greater
lower

Question 23

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

Answer 23

more
greater
lower

Question 24

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

Answer 24

water-powder ratio

Question 25

the water-powder ration depends on the type of _______

Answer 25

powder

Question 26

plaster requires more or less water

Answer 26

more = thinner

Question 27

improved stones require more or less water

Answer 27

less = thicker

Question 28

water-powder ratio of plaster

Answer 28

45-50mL/100g

Question 29

water-powder ration of stone

Answer 29

28-30mL/100g

Question 30

water-powder ratio of improved stone

Answer 30

19-24mL/100g

Question 31

which gypsum material is not too thin and not too thick

Answer 31

stone

Question 32

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

Answer 32

working time (initial setting time)

Question 33

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

Answer 33

final setting time

Question 34

how long is final setting time

Answer 34

30-45 minutes

Question 35

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

Answer 35

retarders

Question 36

what increases working time

Answer 36

retarders

Question 37

decrease setting time so that the product sets up faster

Answer 37

accelerators

Question 38

what will decrease the working time

Answer 38

accelerators

Question 39

all gypsum products expand ______ when they set

Answer 39

externally

Question 40

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

Answer 40

chemicals

Question 41

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

Answer 41

porosity

Question 42

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

Answer 42

water

Question 43

how long should you spatulate stone mixtures

Answer 43

30 seconds

Question 44

what does the vibrator do

Answer 44

remove air bubbles

Question 45

where should you place the stone from on the impression

Answer 45

distal to the last molar

Question 46

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

Answer 46

0.25

Question 47

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

Answer 47

10

Question 48

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

Answer 48

36 mL

Question 49

how thick should the paddy of the base be

Answer 49

1 inch

Question 50

where should the stone material NOT touch

Answer 50

on the plastic or metal tray

Question 51

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

Answer 51

45-60 minutes

Question 52

_________ mL H2O per bag of stone to fill impression

Answer 52

38-40

Question 53

________ mL H2O per bag of stone for paddy

Answer 53

36-38