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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
Q

should you place a thin layer of cyanoacrylate over the whole prep? why?

A

YES! this harden the die and acts as a spacer

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26
Q

where should you place die lube on cast

A

EVERYWHERE you don’t want the wax to stick

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27
Q

what angle should the sprue be placed on wax up

A

45 degrees

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28
Q

when placing wax up inside the investing place

A

wax up should be slightly off center

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29
Q

should you use water to mix with CERAFINA?

A

NO! use special liquid Smoothex??

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30
Q

surrounding the wax pattern with a material that can accurately duplicate its shape

A

investing

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31
Q

removal of the wax pattern so that a mold is created into which molten alloy can be placed/forced

A

burnout

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32
Q

introducing the molten alloy into the previously prepared mold

A

casting

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33
Q

who is the person that introduced the lost wax technique

A

Taggart 1906

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34
Q

what alludes to the cost of the metal

A

precious

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35
Q

what refers to how the metal behaves chemically

A

noble

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36
Q

what pertains to the purity of the metal

A

Karat

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37
Q

what metals are resistant to corosion and oxidation in moist air

A

noble metal

38
Q

examples of noble metals

A
  1. gold
  2. silver
  3. copper
  4. platinum
39
Q

what are rare, naturally occurring and highly valuable metals

A

precious metal

40
Q

examples of precious metals

A
  1. gold, palladium and platinum
  2. silver (less expensive but still rare so precious
41
Q

what metals are both noble and precious

A

gold, silver, platinum, and palladium

42
Q

how to calculate Karats

A

24x mass of gold/ total mass

e.g. 50% gold alloy = 12 karat
50/100 = K/24
K=12

43
Q

dental alloys are identified by the ___ content

44
Q

noble metals impart what?

A

tarnish resistance and ductility

45
Q

___ lightens color and gives some noble qualities without increasing cost too much

46
Q

___ adds hardness and strength

47
Q

what must have a composition that is over 60% noble metal of which over 40% must be gold

A

high noble alloys

48
Q

what must have at least 25% noble metal

A

noble alloys

49
Q

what has less than 25% noble metal (often called base metal)

A

non-noble metals

50
Q

chromium-cobalt and nickel-chromium are examples of what type of metal

A

non-noble(non-precious)

51
Q

what are dental casting alloys? which one is cancer causing

A
  1. nickel
  2. beryllium - cancer causing
  3. titanium (non-noble)
52
Q

what are characteristics of investment materials

A
  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
Q

gold alloys shrink ___% and nickel-chromium alloys shrink ___% upon solidification

54
Q

how can you compensate for solidification shrinkage

A

expanding the mold

55
Q

types of expansions

A
  1. setting expansion
  2. hygroscopic expansion
  3. wax pattern expansion
  4. thermal expansion
56
Q

what type of expansion:

  • occurs by crystal growth of investment
  • 0.4%
A

setting expansion

57
Q

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
A

hygroscopic expansion

58
Q

what type of expansion:

low-temp burnout allows for wax expansion

A

wax pattern expansion

59
Q

what type of expansion:

  • investment expands when heated in the open
  • high temp burnout method compensates for entire alloy shrinkage
A

thermal expansion

60
Q

what does sprue former attach to

A

one end to wax pattern, the other end to crucible former

61
Q

the channel left after the burnout is called what

62
Q

what is the sprue made of

A

10 or 12 gauge and made of wax, plastic or metal

63
Q

where is the sprue former atached to wax pattern

A

at area of greatest bulk

64
Q

how is the sprue attached

A

at a angle to allow free flow of molten metal (minimal turbulence)

65
Q

Cera-Fina phosphate-bonded investments = __ degrees F

66
Q

how many mm from wax pattern to top of device

67
Q

what is the name of the ring liner in the crucible

A

Kaolin liner (wet)

68
Q

how to invest

A
  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
Q

why must you vacuum mix cera fina

A

hand mixing = 3X the amount of nodules

70
Q

what does burnout do

A

prepare the mold for molten alloy and allows for thermal expansion

71
Q

do you use the high temp technique or low temp technique for burnout

72
Q

steps for burnout and casting

A
  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
Q

how to clear the casting

A
  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
Q

what are parts of the casting machine

A
  1. cradle
  2. crucible
  3. pin
  4. handle
  5. counterweight
75
Q

what happened when one large nodule is present on metal

A

air trapped during investing

76
Q

what happened when there are multiple random nodules on metal

A

inadequate vacuum during mixing

77
Q

what happened when there are nodules on underside only on metal

A

prolonged vibration after pouring

78
Q

what happened if there is a shrink spot porosity on metal

A

sprue attachment too bulky. sprue too long or thing. button too small

79
Q

what happened if theres random porosity on metal

A

dirt in wax pattern. loose particles of investment from sharp edge

80
Q

what happened if there are fins on metal

A

dropped ring, rapid heating of wet or unhardened mold, liner flush with end of ring, excessive casting forces

81
Q

what happened if there are short rounded margins with rounded or lumpy button on metal

A

alloy not hot enough or insufficient casting forces

82
Q

what happened if theree are short, rounded margins with sharp button on metal

A

pattern too far from end of ring or if casting is shiny, incomplete burnout of wax

83
Q

what happened if the metal has black, rough casting

A

breakdown of investment from excessive heat

84
Q

T/F: quenching (put in water) of the investment should not be done because it makes it harder to remove the investment

85
Q

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

86
Q

which teeth have a lingual prominence of 0.5 mm

A

maxillary teeth and mandibular first premolars

87
Q

which teeth have a lingual prominence of 0.75 mm

A

mandibular second premolars

88
Q

which teeth have a lingual prominence of 1.0 mm

A

mandibular molars

89
Q

is rexillium III precious or non-precious

A

non-precious (nickel-chrominum base)

90
Q

rexillium contains ___% of beryllium

91
Q

what non-precious alloy has an outstanding bond strength and is equivalent to precious ceramic alloys

A

rexillium III

23 Fixed Prosth (21 decks)

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