casting of metal Flashcards
(78 cards)
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
2
Q
2 methods of INVESTING
A
- vacuum
- hand
3
Q
materials used in placement of CASTING RING LINER
A, A, C, C
A
- asbestos (carcinogenic)
- aluminum silicate ceramic material
- cellulose paper
- ceramic (cellulose combination)
4
Q
types of CASTING MACHINE
A
- air pressure casting machine
- centrifugal casting machine
- induction melting casting machine
- spring-wound electrical restistance
5
Q
not rust, prevent mold roughness
kind of sprue
A
PLASTIC
6
Q
fluxes used to:
A
- prevent oxidation
- minimize porosity
- increase fluidity of metal
7
Q
- removes air bubbles
- porosity is reduced
- evacuate harmful gases
- 95% nodule free
method of investing
A
vacuum method
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
9
Q
most versatile
kind of sprue
A
wax
10
Q
*note: wax are colored to simplify examination of margin on the stone
A
11
Q
what is the purpose of SPRUE?
holds, determines, leads
A
- holds the wax pattern on the sprue base
- determines the position of the wax pattern within the investment and inlay ring
- leads the molten gold from crucible to molten cavity
12
Q
4th step in CASTING
A
burnout
13
Q
greater setting and thermal expansion
factors that will influence MOLD SIZE
A
two layer liner
14
Q
must be covered with wax
kind of sprue
A
METAL
15
Q
3rd step in CASTING
A
investing
16
Q
WHAT ARE THE TYPES OF WAX ACCORDING TO FLOW?
3 ITEMS
A
- TYPE A
- TYPE B
- TYPE C
17
Q
fuels used in FUSING NOBLE METAL
A
- mixture of natural and artificial gas and air
- oxygen (air acetylene)
18
Q
hard, low flow
type of wax
A
type A
19
Q
parts of ZONE OF FLAME
A
- combustion zone
- reducing/inner zone
- oxidizing zone
20
Q
INDICATIONS OF DIRECT TECHNIQUE
A
- small casting in anterior and bicuspid teeth
- adequate access
- 1 or 2 teeth restored
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
22
Q
materials used in PICKLING
A
- HCl 50%
- H2SO4
- ultrasonic device
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
24
Q
wax pattern cleaner
A
diluted synthetic detergent
25
**after how many hours an investment is ready for burnout?**
1 hour
26
**2nd step on casting**
spruing the pattern
27
**why liner should be shorter?**
* more uniform expansion
* prevent investment from falling out during handling
28
**COOLING process of CASTING**
* *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
29
**to achieve "carving accuracy"**
| avoid, carver, carve, carve
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
30
**first process**
* wax pattern
31
what is the chief cause of **distortion** of wax?
relaxation of stress during manipulation
32
**holds the investment together like *gypsum and phosphate***
binder
33
**material that forms the channel which molten metal travel to form the restoration; provides an ingate for molten metal**
SPRUE
34
**factors that affect the *accuracy*** **of the wax pattern**
| 3 items (T.W.C.)
* temp. of wax
* wax adaptation - helps overcome *shrinkage* when warm wax cools in the mouth
* carving accuracy
35
**4 kinds of SPRUE**
* wax
* plastic
* metal
* resin
36
**to try-in the casting before removing the sprue and sprue button**
seating, adjusting, and polishing of casting
37
**furnace**
* **initial tem = ?**
* **final temp or .... = ?** **for how many mins.?**
* 600F
* heat soaking, 1300F, 30mins
38
**what are the INVESTMENT MATERIALS**
| B, R
* binder
* refractory material
39
**placement of CASTING RING LINER**
* liner afford *greater normal setting expansion* of investment
* liner causes *semihygroscopic expansion*
* liner should be shorter than the ring
40
**indicates *surface oxidation by blowpipe flame****
cloudy surface
41
**methods of BURNOUT**
1. flush mold with *boiling waters*
2. heat
42
**formed from the reaction of ammonium hydrogen phosphate w/ magnesium oxide**
phosphate binder
43
**CEMENTATION**
| 5 items
* zinc phosphate
* zinc silicophosphate
* zinc polycarboxylate
* glass ionomer
* resin cement
44
**2 WAYS OF MAKING WAX PATTERN**
1. direct technique
2. indirect technique
45
**it is properly positioned to melt the alloy easily**
torch
46
**the machine is qound until the spring is under tension**
spring-wound electrical resistance
47
**types of CRUCIBLE**
* clay
* carbon
* quartz
48
**done immediately *after*** **burnout procedure**
casting
49
**lower of ... = greater expansion**
| factors that will influence MOLD SIZE
w/p ratio
50
**what is the purpose of *INVESTING*****?**
| confine, allow
* confine investment around the wax pattern
* allow the hardened investment to be handled safely *during burnout and casting*
51
**main ingredient of wax**
| 2 items
1. paraffin w/ gum dammar
2. carnauba
52
**this needs to take impression with *elastic material***
INDIRECT TECHNIQUE
53
**6th step in CASTING**
breakout casting from investment
54
**how short should be the liner than the ring?**
6 mm
55
**what to do on seating, adjusting, and polishing of casting**
* 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
**indicates *proper fusion***
mirror-like surface
57
**factors that will influence MOLD SIZE**
1. two layer liner
2. w/p ratio
58
**5th step on CASTING**
CASTING
59
**how to adapt wax on die?**
| 2 items.
what instrument? recommended on making pattern and minimizes?
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
**length of SPRUE**
| not, completely, rule
* 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
**OTHER TERM FOR CASTING OF METALS**
lost wax technique of casting
62
**helps overcome *shrinkage* when warm wax cools in the mouth**
Wax Adaptation
63
soft, more flow, used for ***indirect technique***
| type of wax
type C
64
**BURNOUT procedure**
* 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
**wax made from final restoration**
WAX PATTERN
66
**heat but not boil the metal *to remove oxides***
pickling
67
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**
phosphate-bonded investment
68
**types of INVESTMENT MATERIAL**
| 2 ITEMS
* gypsum-bonded investment
* phosphate-bonded investment
69
**WHAT IS THE FULL PROCESS ON *CASTING OF METALS*?**
| 1-9
wax pattern -> spruing -> investing -> burnout -> casting -> breakout casting from investment -> pickle casting -> remove sprue and polish -> deliver to patient
70
**7th step in CASTING**
pickling
71
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***
gypsum-bonded investment
72
**what happens if heated to a much higher temp**
| BURNOUT procedure
rough casting & contamination of *Au alloy w/ sulfur*
73
**used to hold alloy *before and during melting* of alloys**
crucible
74
**materials used as FLUXES**
* powdered charcoal
* borax powder with boric acid powder
75
medium, minimal flow, used for ***direct technique***
| type of wax
type B
76
**results in excessive occlusal contact**
incomplete seating of metal to die
77
**resists the heat of burnout and casting like *silica***
refractory material
78
* ***17%* free of defect**
| method of INVESTING
hand method
