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casting of metal Flashcards

1
Q

ADVANTAGES OF DIRECT TECHNIQUE

time? requires? no? less? good?

A
  • shorter time to construct, prepared, and inserted on same day
  • requires few materials
  • no temporary needed
  • less expensive
  • good fit for inlay
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2
Q

2 methods of INVESTING

A
  1. vacuum
  2. hand
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3
Q

materials used in placement of CASTING RING LINER

A, A, C, C

A
  1. asbestos (carcinogenic)
  2. aluminum silicate ceramic material
  3. cellulose paper
  4. ceramic (cellulose combination)
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4
Q

types of CASTING MACHINE

A
  1. air pressure casting machine
  2. centrifugal casting machine
  3. induction melting casting machine
  4. spring-wound electrical restistance
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5
Q

not rust, prevent mold roughness

kind of sprue

A

PLASTIC

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6
Q

fluxes used to:

A
  1. prevent oxidation
  2. minimize porosity
  3. increase fluidity of metal
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7
Q
  • removes air bubbles
  • porosity is reduced
  • evacuate harmful gases
  • 95% nodule free

method of investing

A

vacuum method

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8
Q

sizes of SPRUE

thicker, size, size, localized, attached

A
  • thicker than the thickest portion of the wax pattern
  • 8-12 gauze round sprue
  • 12-18 gause for small casting
  • localized shrinkage porosity (due to thin sprue
  • attached to a reservoir 1mm from the pattern
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9
Q

most versatile

kind of sprue

A

wax

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10
Q

*note: wax are colored to simplify examination of margin on the stone

A
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11
Q

what is the purpose of SPRUE?

holds, determines, leads

A
  1. holds the wax pattern on the sprue base
  2. determines the position of the wax pattern within the investment and inlay ring
  3. leads the molten gold from crucible to molten cavity
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12
Q

4th step in CASTING

A

burnout

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13
Q

greater setting and thermal expansion

factors that will influence MOLD SIZE

A

two layer liner

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14
Q

must be covered with wax

kind of sprue

A

METAL

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15
Q

3rd step in CASTING

A

investing

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16
Q

WHAT ARE THE TYPES OF WAX ACCORDING TO FLOW?

3 ITEMS

A
  1. TYPE A
  2. TYPE B
  3. TYPE C
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17
Q

fuels used in FUSING NOBLE METAL

A
  • mixture of natural and artificial gas and air
  • oxygen (air acetylene)
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18
Q

hard, low flow

type of wax

A

type A

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19
Q

parts of ZONE OF FLAME

A
  • combustion zone
  • reducing/inner zone
  • oxidizing zone
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20
Q

INDICATIONS OF DIRECT TECHNIQUE

A
  • small casting in anterior and bicuspid teeth
  • adequate access
  • 1 or 2 teeth restored
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21
Q

location of SPRUE

attached, should, attached, should, flare

A
  • attached to portion of pattern w/ largest cross-sectional areas and away from the thin/delicate parts
  • should be located so as not to obliterate centric occlusal relationship
  • attached to nonworking cusp
  • should not be attached at right angle or sharp angle to broad flat surface – turbulence of metal – suck-back porosity
  • flare the attachment of sprue
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22
Q

materials used in PICKLING

A
  • HCl 50%
  • H2SO4
  • ultrasonic device
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23
Q

substance adde to the surface of the molten metal to prevent oxygen in the air from coming in contact w/ hot metal

A

fluxes

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24
Q

wax pattern cleaner

A

diluted synthetic detergent

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25
Q

after how many hours an investment is ready for burnout?

A

1 hour

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26
Q

2nd step on casting

A

spruing the pattern

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27
Q

why liner should be shorter?

A
  • more uniform expansion
  • prevent investment from falling out during handling
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28
Q

COOLING process of CASTING

A
  • bench cooling the metal
  • quenching immediate placement of hot castings in water as soon as button has dull red glow metal is in annealed condition
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29
Q

to achieve “carving accuracy”

avoid, carver, carve, carve

A
  1. avoid melting wax
  2. carver should have smooth blunted edges for burnishing
  3. carve the proximal first then the occlusal
  4. carve from the wax to the cavosurface margin
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30
Q

first process

A
  • wax pattern
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31
Q

what is the chief cause of distortion of wax?

A

relaxation of stress during manipulation

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32
Q

holds the investment together like gypsum and phosphate

33
Q

material that forms the channel which molten metal travel to form the restoration; provides an ingate for molten metal

34
Q

factors that affect the accuracy of the wax pattern

3 items (T.W.C.)

A
  • temp. of wax
  • wax adaptation - helps overcome shrinkage when warm wax cools in the mouth
  • carving accuracy
35
Q

4 kinds of SPRUE

A
  • wax
  • plastic
  • metal
  • resin
36
Q

to try-in the casting before removing the sprue and sprue button

A

seating, adjusting, and polishing of casting

37
Q

furnace
* initial tem = ?
* final temp or …. = ? for how many mins.?

A
  • 600F
  • heat soaking, 1300F, 30mins
38
Q

what are the INVESTMENT MATERIALS

B, R

A
  • binder
  • refractory material
39
Q

placement of CASTING RING LINER

A
  • liner afford greater normal setting expansion of investment
  • liner causes semihygroscopic expansion
  • liner should be shorter than the ring
40
Q

indicates surface oxidation by blowpipe flame*

A

cloudy surface

41
Q

methods of BURNOUT

A
  1. flush mold with boiling waters
  2. heat
42
Q

formed from the reaction of ammonium hydrogen phosphate w/ magnesium oxide

A

phosphate binder

43
Q

CEMENTATION

5 items

A
  • zinc phosphate
  • zinc silicophosphate
  • zinc polycarboxylate
  • glass ionomer
  • resin cement
44
Q

2 WAYS OF MAKING WAX PATTERN

A
  1. direct technique
  2. indirect technique
45
Q

it is properly positioned to melt the alloy easily

46
Q

the machine is qound until the spring is under tension

A

spring-wound electrical resistance

47
Q

types of CRUCIBLE

A
  • clay
  • carbon
  • quartz
48
Q

done immediately after burnout procedure

49
Q

lower of … = greater expansion

factors that will influence MOLD SIZE

50
Q

what is the purpose of INVESTING?

confine, allow

A
  • confine investment around the wax pattern
  • allow the hardened investment to be handled safely during burnout and casting
51
Q

main ingredient of wax

2 items

A
  1. paraffin w/ gum dammar
  2. carnauba
52
Q

this needs to take impression with elastic material

A

INDIRECT TECHNIQUE

53
Q

6th step in CASTING

A

breakout casting from investment

54
Q

how short should be the liner than the ring?

55
Q

what to do on seating, adjusting, and polishing of casting

A
  • hand burnish the marginal metal on die
  • check occlusal contact w/ articulating paper
  • incomplete seating of metal to die results in excessive occlusal contact
56
Q

indicates proper fusion

A

mirror-like surface

57
Q

factors that will influence MOLD SIZE

A
  1. two layer liner
  2. w/p ratio
58
Q

5th step on CASTING

59
Q

how to adapt wax on die?

2 items.
what instrument? recommended on making pattern and minimizes?

A
  1. adapt wax to the die with **dry high heat instrument ** as possible
  2. melting of wax is recommended in making pattern on die. it will minimize residual stress in wax
60
Q

length of SPRUE

not, completely, rule

A
  • not too short/long
  • around 2-5mm
  • completely eliminate gas - back pressure porosity
  • rule to follow is 1/4 in./6mm of the open end of inlay ring
61
Q

OTHER TERM FOR CASTING OF METALS

A

lost wax technique of casting

62
Q

helps overcome shrinkage when warm wax cools in the mouth

A

Wax Adaptation

63
Q

soft, more flow, used for indirect technique

type of wax

64
Q

BURNOUT procedure

A
  • total time burnout
  • 2 1/4 for eliminating water and raising temperature of mold to 1300F
  • if heated to a much higher temp. = rough casting & contamination of Au alloy w/ sulfur
65
Q

wax made from final restoration

A

WAX PATTERN

66
Q

heat but not boil the metal to remove oxides

67
Q
  1. has additional chemical reaction when heated nad make it more resistant to heat
  2. for metal coping of PFM and PD framework
  3. wax pattern should be cleaned of debris, grease, oil
  4. use wax pattern cleaner
  5. a thin film of cleanser left in the pattern reduces the surface tension of the wax and permit better wetting of the investment
A

phosphate-bonded investment

68
Q

types of INVESTMENT MATERIAL

2 ITEMS

A
  • gypsum-bonded investment
  • phosphate-bonded investment
69
Q

WHAT IS THE FULL PROCESS ON CASTING OF METALS?

1-9

A

wax pattern -> spruing -> investing -> burnout -> casting -> breakout casting from investment -> pickle casting -> remove sprue and polish -> deliver to patient

70
Q

7th step in CASTING

71
Q
  1. utilizes gypsum as binder; used in casting application to metal alloys w/ melting range not more than 1200 degree C
  2. for inlay and metal crown casting
A

gypsum-bonded investment

72
Q

what happens if heated to a much higher temp

BURNOUT procedure

A

rough casting & contamination of Au alloy w/ sulfur

73
Q

used to hold alloy before and during melting of alloys

74
Q

materials used as FLUXES

A
  • powdered charcoal
  • borax powder with boric acid powder
75
Q

medium, minimal flow, used for direct technique

type of wax

76
Q

results in excessive occlusal contact

A

incomplete seating of metal to die

77
Q

resists the heat of burnout and casting like silica

A

refractory material

78
Q
  • 17% free of defect

method of INVESTING

A

hand method

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