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23 Fixed Prosth > 6/16 - Wax Patterns, Investing and Casting, 343-360, 363-376, S4a-S4c > Flashcards

6/16 - Wax Patterns, Investing and Casting, 343-360, 363-376, S4a-S4c Flashcards

1
Q

T/F: definitive restoration can be no better than wax pattern

A

TRUE

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2
Q

can a few extra minutes spent on the wax pattern save hours correcting the casting

A

YES

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3
Q

direct technique vs. indirect

A

direct: in patient mouth
indirect: outside patient mouth

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4
Q

which technique allows for better visualization and ready access to waxing the margin

A

indirect

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5
Q

which technique is the most popular technique: direct or indirect

A

indirect

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6
Q

Is type I wax direct or indirect

A

direct

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7
Q

is type II “inlay” wawax direct or indirect

A

indirect

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8
Q

what colors of wax should you use for wax up

A

red, green or blue

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9
Q

can you leave the pattern of the die on for long periods of time

A

NEVER

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10
Q

when should you invest the pattern

A

immediately after fabrication

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11
Q

what is a thin layer of wax resembling a thimble that is fabricated on the die to serve as a foundation for the final wax up

A

wax coping

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12
Q

how do you being wax up

A

lubricate the die and dip into molten wax (head start)

OR

begin without dipping

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13
Q

how to start building wax pattern

A
  1. begin with proximal contacts
  2. proximal surface should be mirror image of prox surface
  3. continue with axial contours
  4. lingual embrasures slightly larger than facial embrasures
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14
Q

what is the part of the axial contour that extends from the base of the gingival sulcus past the free margin of the gingiva

A

emergence profile

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15
Q

what extends to HOC, allows for effective oral hygiene, easier to evaluate with a periodontal probe

A

emergence profile

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16
Q

___ leads to inflammation, ___ leads to no significant changes

A

overcontour; undercontour

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17
Q

is is better to undercontour than overcontour

A

undercontour

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18
Q

when can you start waxing up occlusal surface

A

after building axial surfaces

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19
Q

what does max mesiopalatal cusp of first molar occlude

A

cusp-fossa: central fossa of first molar
cusp-marginal ridge: central fossa of the first molar

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20
Q

___ cusps placed as far lingually as possible and as far apart as possible

A

lingual

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21
Q

___ cusps are shorter than ___ cusps

A

lingual; facial

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22
Q

should you put excess wax on margins

A

YES

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23
Q

should you use a sharp instrument to remove excess wax from margin

A

NO! carving and burnishing

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24
Q

do you want highly polished wax up

A

not necessary, just need an extremely smooth surface

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25
should you place a thin layer of cyanoacrylate over the whole prep? why?
YES! this harden the die and acts as a spacer
26
where should you place die lube on cast
EVERYWHERE you don't want the wax to stick
27
what angle should the sprue be placed on wax up
45 degrees
28
when placing wax up inside the investing place
wax up should be slightly off center
29
should you use water to mix with CERAFINA?
NO! use special liquid Smoothex??
30
surrounding the wax pattern with a material that can accurately duplicate its shape
investing
31
removal of the wax pattern so that a mold is created into which molten alloy can be placed/forced
burnout
32
introducing the molten alloy into the previously prepared mold
casting
33
who is the person that introduced the lost wax technique
Taggart 1906
34
what alludes to the cost of the metal
precious
35
what refers to how the metal behaves chemically
noble
36
what pertains to the purity of the metal
Karat
37
what metals are resistant to corosion and oxidation in moist air
noble metal
38
examples of noble metals
1. gold 2. silver 3. copper 4. platinum
39
what are rare, naturally occurring and highly valuable metals
precious metal
40
examples of precious metals
1. gold, palladium and platinum 2. silver (less expensive but still rare so precious
41
what metals are both noble and precious
gold, silver, platinum, and palladium
42
how to calculate Karats
24x mass of gold/ total mass e.g. 50% gold alloy = 12 karat 50/100 = K/24 K=12
43
dental alloys are identified by the ___ content
gold
44
noble metals impart what?
tarnish resistance and ductility
45
___ lightens color and gives some noble qualities without increasing cost too much
silver
46
___ adds hardness and strength
copper
47
what must have a composition that is over 60% noble metal of which over 40% must be gold
high noble alloys
48
what must have at least 25% noble metal
noble alloys
49
what has less than 25% noble metal (often called base metal)
non-noble metals
50
chromium-cobalt and nickel-chromium are examples of what type of metal
non-noble(non-precious)
51
what are dental casting alloys? which one is cancer causing
1. nickel 2. beryllium - cancer causing 3. titanium (non-noble)
52
what are characteristics of investment materials
1. must precisely reproduce detailed form of wax pattern 2. must provide sufficient strength to withstand the heat of burnout and casting of metal 3. must expand sufficiently to compensate for solidification shrinkage of alloy
53
gold alloys shrink ___% and nickel-chromium alloys shrink ___% upon solidification
1.5, 2.4
54
how can you compensate for solidification shrinkage
expanding the mold
55
types of expansions
1. setting expansion 2. hygroscopic expansion 3. wax pattern expansion 4. thermal expansion
56
what type of expansion: - occurs by crystal growth of investment - 0.4%
setting expansion
57
what type of expansion: - letting investment set in a 100 degree water bath - 1.2%-2.2% - expansion occurs due to expansion of wax pattern caused by increased temperature of water
hygroscopic expansion
58
what type of expansion: low-temp burnout allows for wax expansion
wax pattern expansion
59
what type of expansion: - investment expands when heated in the open - high temp burnout method compensates for entire alloy shrinkage
thermal expansion
60
what does sprue former attach to
one end to wax pattern, the other end to crucible former
61
the channel left after the burnout is called what
the sprue
62
what is the sprue made of
10 or 12 gauge and made of wax, plastic or metal
63
where is the sprue former atached to wax pattern
at area of greatest bulk
64
how is the sprue attached
at a angle to allow free flow of molten metal (minimal turbulence)
65
Cera-Fina phosphate-bonded investments = __ degrees F
<1975
66
how many mm from wax pattern to top of device
6 mm
67
what is the name of the ring liner in the crucible
Kaolin liner (wet)
68
how to invest
1. wet liner after it is placed into the ring 2. vacuum mix is a must 3. connect the tubing 4. hand mix initially to incorporate liquid into the powder 5. follow instructions for machine mixing
69
why must you vacuum mix cera fina
hand mixing = 3X the amount of nodules
70
what does burnout do
prepare the mold for molten alloy and allows for thermal expansion
71
do you use the high temp technique or low temp technique for burnout
either
72
steps for burnout and casting
1. use high temp or low temp technique 2. use low temp technique if hygroscopic expansion(water bath) was used 3. remove the crucible former and place into over 4. gas-air torch 5. wind the arm, place ingots, melt the metal, place the ring into cradle 6. pull back on the arm and let go
73
how to clear the casting
1. do not quench base metal castings (put in water) 2. remove excess investment with hammer then a handpiece 3. sandblaster will remove the last bit of investment air abrade the surface 4. do not pickle base metal castings (soak in hot acid)
74
what are parts of the casting machine
1. cradle 2. crucible 3. pin 4. handle 5. counterweight
75
what happened when one large nodule is present on metal
air trapped during investing
76
what happened when there are multiple random nodules on metal
inadequate vacuum during mixing
77
what happened when there are nodules on underside only on metal
prolonged vibration after pouring
78
what happened if there is a shrink spot porosity on metal
sprue attachment too bulky. sprue too long or thing. button too small
79
what happened if theres random porosity on metal
dirt in wax pattern. loose particles of investment from sharp edge
80
what happened if there are fins on metal
dropped ring, rapid heating of wet or unhardened mold, liner flush with end of ring, excessive casting forces
81
what happened if there are short rounded margins with rounded or lumpy button on metal
alloy not hot enough or insufficient casting forces
82
what happened if theree are short, rounded margins with sharp button on metal
pattern too far from end of ring or if casting is shiny, incomplete burnout of wax
83
what happened if the metal has black, rough casting
breakdown of investment from excessive heat
84
T/F: quenching (put in water) of the investment should not be done because it makes it harder to remove the investment
TRUE
85
it may be necessary to remove the wax ___ mm from the marginal periphery of the pattern to ensure that it will seat all the way on the working cast
1 mm
86
which teeth have a lingual prominence of 0.5 mm
maxillary teeth and mandibular first premolars
87
which teeth have a lingual prominence of 0.75 mm
mandibular second premolars
88
which teeth have a lingual prominence of 1.0 mm
mandibular molars
89
is rexillium III precious or non-precious
non-precious (nickel-chrominum base)
90
rexillium contains ___% of beryllium
1.8
91
what non-precious alloy has an outstanding bond strength and is equivalent to precious ceramic alloys
rexillium III

23 Fixed Prosth (21 decks)

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