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Restorative > Casting Alloys > Flashcards

Casting Alloys Flashcards

1
Q

What is an alloy?

A

an alloy is a mixture of one or more metallic elements

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2
Q

T/F alloys have better qualities than the metal used alone

A 
T
Cost
Bicompatibility
Mechanical properties
Easy of casting
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3
Q

What are some alloys used in dentistry?

A

Amalgam
Gold
SS
NiTi

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4
Q

WHat are the three stages in alloy fabrication?

A

FAC

Forming
Amalgamtion
Casting

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5
Q

WHat happen in the forming phase?

A

plastic deformation

hot and cold working eg extrusion, rolling, drawing

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6
Q

What happens in the amalgamtion phse?

A

blending mercury with other materials

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7
Q

What happens in the casting phase?

A

puring molten metal into mould

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8
Q

What technqiues tdo we use for dental casting alloy?

A

lost wax technique

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9
Q

What are the two groups of cating metal alloys?

A

Noble

Base Metal Casting

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10
Q

What are the two types of noble metal alloys?

A

Gold

Silver palladium

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11
Q

What are the three types of base metal casting alloys?

A

Titanium
Nickle Chromum
CoCr

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12
Q

T/F Noble metals do not regtain luster in clean dry air?

A

F

they do

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13
Q

What are noble metals resisnt to?

A 
oxidation
tarnish
corrosion 
casting 
soldering
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14
Q

What are the thre types of noble metals used?

A

platunum goeup
gold
silver

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15
Q

What metals are inside the platiunum group?

A 
platinum
iridum
osmim
ruthenium
rhodoim
palladium
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16
Q

WHat are the properties of gold?

A

soft malleable and ductile

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17
Q

T/F Gold has a relatively low strentgh>

A

T

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18
Q

When or not does gold tarnish?

A

gold does not tarnish in air or water at any temp

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19
Q

What type of oxidsing agnets can attcck gold?

A

very powerful ones

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20
Q

What acids is gold insoluble in?

A

nitric

sulphiric and hydrochloric

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21
Q

What acids is gold souble in?

A

when nitric and sulfuric acid is combined

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22
Q

What is the effect of impurities on golds properties?

A

eg lead and mercury

they are detrimental

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23
Q

WHat are the mechanical propertes of pt?

A

touch malleable and ductile

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24
Q

How com,on is Pt used now?

A

rarely since too expensive and has been replaced by oaladium

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25
Q

T.F Pt has a low corrosion resistance?

A

f

high

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26
Q

What is the metal poin of Pt compared to porcelain?

A

higher

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27
Q

Which noble metal is not used in its pure state in dentistry?

A

Palladium

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28
Q

WHat has Pd repalced?

A

Pt

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29
Q

What is the effect of Pd in silver>

A

helps prevent corrosion in mouth

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30
Q

What is the ffect of heating Pd improperly?

A

abosrobs H2 gas

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31
Q

What are the properties of Ag?

A

malleable and ductile

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32
Q

T/F Ag is harder than gold?

A

t

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33
Q

Which metal is the best known conductor of heat and elctricuty?

A

silver

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34
Q

What is the effect of clean dry air on silver?

A

none

not altered

35
Q

T/F Silver tarnishes in the mouth?

A

T

36
Q

Why does silver tarnish in the mouth?

A

combines with sulfur chlorine and phosphorus

37
Q

What happens when silber is in its molten state?

A

it occludes large amounts of ocygen which then evolves when silver solidifeies creating pits and voids

38
Q

Give examples of minor alloying elemnets?

A

Iridum

Ruthenium

39
Q

What is the effect of ruthenium and iridium?

A

they are both grain refinfing

40
Q

How much Ru and Ir are added to the metals?

A

50ppm 0.005%

which will increase grain number by 100

41
Q

T/F Ir and Ru can increase alloy tensile strength?

A

T

by 30% !!!!!!

42
Q

What effect does Ir and Ru have on hardness?

A

no effect

43
Q

What is the effect of Ir and Ru on tarnish?

A

increases tarnish resistance

44
Q

What is the effect of Ir and Ru on yiled streess?

A

sight increase

45
Q

WHat is the problem with using gold in ots pire state?

A

it is too soft

46
Q

What type of gold is used in fillings?

A

cohesive gold

47
Q

What types of gold are there?

A 
4 types
1 soft
2 medium
3 hard
4 v hard
48
Q

How does the gold content change from type 1 to 4?

A

it decreases

49
Q

What are the two ways of measuring gold content in a ental alloy?

A

Karat

Finess

50
Q

Karat measures what?

A

oarts of pure gold per 24

51
Q

How much is 12K gold?

How much is 18K gold?

A

12=50% gold

18=75%

52
Q

What does finess measure?

A

parts of pure gold per 1000

53
Q

WHen is finness usually used?

A

for measuring gold in solders

54
Q

Whaty does a finess of 650 mean?

A

65% gold

55
Q

What 5 metals are added to gold?

A 
copper
silver
palladium
platinum
zinc
56
Q

What is the pupose of copper in gold?

A

strengthening
lowers MP
tarnishes

57
Q

What is the pupose of silver in gold?

A

slightly strengthening and conunteract coppers reddish tint

58
Q

What is the purpse of Pt and Pd in gold?

A

increases Melting temp

59
Q

What is the purpose of Zn in gold?

A

acts as a scavenger during casting and impoves catability

60
Q

Which properties increase as you go from type 1 to type 4 gold?

A

hardness
Mod elasticiy
tensile strength
propotional limit

61
Q

Which properties decrease as you go from type 1 to type 4 gold?

A

Ductility

corrosion resistance

62
Q

When is type 1 gold used?

A

inlays where they are well suported an no large masticaroy forces
since it is v ductile, it can be burnshed and well adapted to margins

63
Q

Where is type 2 gold used?

A

inlays

better than type 1 just more brittle

64
Q

Where is type 3 gold used?

A 
areas where less support from tooth and high opposing stress
inlays
onlays
crown
short span bridge
65
Q

Where is type 4 gold used?

A

denture and long span bridg

66
Q

What are low contet gold alloys?

A

contain less than 65% gold

67
Q

What is the typical range of gold in low content gold alloys?

A

10-45%

68
Q

Which type of golds 1,2,3,4 are low content gold most like?

A

3 and 4 but more brittle

69
Q

What are silver palladium alloys?

A

xontain no or little gold

70
Q

What are the components of Ag-Pd alloys?

A

Bulk silver
25% Pd

Small: copper zinc indium occ. gold

71
Q

What are base metal casting alloys?

A

contain no or little gold, Ag, Pt or Pd

NiCr
CoCr
Ti and TiAlV

72
Q

WHen are NiCr used?

A

crown and bridge

73
Q

When are CoCr used?

A

dentire

74
Q

Where are Ti used?

A

implant

75
Q

Which two metals in the base metal casting alloys are interchangebel?

A

Ni and Co

76
Q

What is the percentage of Ni or Co and Cr in base metal casting alloys?

A

60% Ni or Co

30% Cr

77
Q

What is the metal point of Co/Ni Cr alloys?

A

1300-1500

78
Q

what is the purpose of adding Molybdenum to Co/Ni Cr alloys?

A

grain refining

79
Q

What os the modulus of elasticity for Co/Ni Cr alloys?

A

250 GPa

Gold is 70-100

80
Q

What is teh Vickers Hardness for Co/Ni Cr alloys?

A

350-400

type 4 Gold is 250-300

81
Q

WHat is the propeties of chromium and what perce tage is it added?

A

added at 25%

tarnish and corroson resistance due to passivation

82
Q

What happens if Cr is added at more than 30%?

A

difficulty casting and brittle

83
Q

What percentage is Co and Ni added and what is the differnce when using Ni vs Co?

A

form the bulk
65-78%

Ni alloys have: decreased Strngh, hardness, MOE fusion temps. Increaed ductulity and elongation

84
Q

What are the minor alloying elements added and what is the pirpse?

A

They control the most of the physical properties

Carbon: 0.1-0.5%
increases strengthm hardness and brittleness,
Beryllium: 0.5-2%
decreases fusion temp and allows for electrolytc etching
Mb: 3-6%
increases strength hardness and elongation
Al: 4-5%
Froms Ni3Al precipiate which increases tensile and yiled strength

Restorative (45 decks)

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