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Dental Materials > Test #1-3 > Flashcards

Test #1-3 Flashcards

1
Q

what is an amalgam

A

an alloy containing mercury

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2
Q

what is the only pure metal that is liquid at room temp

A

mercury

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3
Q

what is an alloy

A

a mixture of 2 or more metallic substances

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4
Q

how are amalgams classified

A

according to composition and particle size

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5
Q

Conventional amalgam is _____ in copper

A

low

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6
Q

What is the composition of amalgam

A 
mercury
silver
tin
copper
zinc
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7
Q

What are the applications for using amalgam

A

load bearing restorations in posterior
pin-retained rest.
retrograde canal filling
root surface rest

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8
Q

What does zinc add to an amalgam

A

adds plasticity, makes it easier to condense

when contaminated with moisture=overenlargement of amalg

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9
Q

What does copper do in an amalgam

A

increases strength, harness, setting expansion and corrosion resistance

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10
Q

What is the copper content of the majority of alloys today*

A

high copper

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11
Q

What do low copper amalgams contain that is responsible for negative characteristics of low copper amaglams*

A

Gamma 2

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12
Q

What is the weakest phase of low copper amalgams

A

Gamma 2

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13
Q

What makes low copper amalgams more suseptible to corrosion

A

Gamma 2

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14
Q

What is Gamma 2

A

reaction wiht tin and mercury

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15
Q

What is the most common copper amaglam reaction

A

Gamma 1

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16
Q

What is a gamma 1 reaction

A

silver and mercury

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17
Q

the more gamma one in a high copper alloy…

A

the stronger the alloy is

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18
Q

What does Gamma 1 do

A
  • holds original alloy particles together

- corrosion resistant

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19
Q

In the amalgam particles sizes what is a lathe cut

A

grinding of a solid metal alloy bar on a lathe, rough irregular findings of various sizes

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20
Q

In the amalgam particle size what is a spherical alloy

A

-made my spraying molten alloy into a vacuum and letting the drops fall, as they fall they become round balls

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21
Q

What is an admixed alloy

A

contains both lathe cut and spherical particles

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22
Q

What kind of particles are most alloys today

A

spherical or admixed

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23
Q

do to spherical particles regular shape they can

A

-reinforce and can be packed closer together

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24
Q

what are the advantages of amalgam

A
  • easy to insert
  • not techique sensitive
  • resists fracture
  • long service life
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25
Q

what are the disadvantages of amalgam

A
  • no color match
  • corrosion, tarnish
  • marginal breakdown
  • creep- open margins
  • high thermal conductivity
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26
Q

what is creep

A

creep causes amalgam to flow and the unsupported amalgam protrudes away from margins

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27
Q

what happens to the unsupported edges with creep

A

weak and become corroded, ditch around margins

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28
Q

What does polishing an amalgam do

A

decreases corrosion

29
Q

what is used to polish amalgam from course to fine

A

bur
pumice
tin oxide

30
Q

What are the main components of ceramic- a glass material

A

Kaolin
Feldspar and quartz
metallic oxides

31
Q

What is Kaolin

A

a clay found on riverbanks, becomes cohesive when wet

32
Q

what is feldspar and quartz

A

mined from the earth and can be ground into powders, similar to sand

33
Q

what are metallic oxides

A

ceramic pigments

34
Q

What happens to feldspar when its subjected to high temperature

A

they fuse and form glass of the same shape

35
Q

what doesnt change when feldspar is heated to high temp

A

silica particles

36
Q

because of the feldspar and silica actions in high temps this means

A

a cohesive mixture that can hold its shape is formed

37
Q

What is the difference between ceramic and porcelain

A

different amounts of feldspar, kaolin and silica

38
Q

how is porcelain made

A

fired, which is baking at a high temp

39
Q

how is ceramic made

A

cast or machine milled

40
Q

What is fusion temperature

A

temp at which grains of porcelain powder fuses to form a ceramic mass

41
Q

What is a glaze

A

creates a smooth, translucent surface similar to enamel

42
Q

What are properties of ceramic/porcelain

A
  • excellent electrical and thermal insulator
  • low thermal expansion
  • low tensile strength
  • high compressive strength
43
Q

What can porcelain be affected by

A

fluorine containing acids APF

44
Q

What is a disadvantage of porcelain

A

harder than tooth structure, can cause wear of opposing teeth

45
Q

What is a cad cam

A

computer that are used to design and cut ceramic restorations

46
Q

What are veneers

A

a thin layer of tooth colored material cemented or bonded to the facial surface of a natural or replacement tooth to improve its appearance

47
Q

What are the 2 types of veneers

A

direct and indirect

48
Q

What are chemical/mechanical precautions for porcelain and composite

A
  • Porcelain needs to be protected from APF

- Composite veneers are subject to scratchin

49
Q

The lower the reactivity of metal the_____________*

A

higher its nobility

50
Q

What are characteristics of noble metals

A

resistant to corrosion and oxidation, precious metals

51
Q

WHat are characteristics of metals*

A

elements that conduct heat and electricity, lustrous, melleable and ductile

52
Q

what are noble alloys

A

combines larger amts of precious metals with smaller amts of base metals to create strong, hard miextures that are highly resistant to tarnish and corrosion, expensive

53
Q

What is an example of a noble metal

A

gold alloys

54
Q

What is the gold for in gold alloys

A

soft, contributes to color, tarnish, and corrosion resistant, malleable and ductility

55
Q

what is the copper for in gold alloys

A

lowers melting temp, contributes to harness and strength and corrosion resistance

56
Q

What is silver for in gold alloys*

A

neutralizes reddish color from copper

57
Q

what is platinum in gold alloys

A

increases strength and melting temp

58
Q

What is palladium in gold alloys

A

less expensive than platinum, same purpose

59
Q

What are examples of base metal alloys

A 
titanium
nickel/chromium
nickel/cobalt
molybdenum
tungsten
60
Q
  • what base metal alloy is not sued any more because of allergy concerns
A

Nickel/ Nickel chromium

61
Q

what is a common base alloy, used in substructure for crowns

A

nickel chromium

62
Q

What is a karat

A

parts of pure gold in 24 parts
100% gold=24 karat
75% gold=18 karat

63
Q

What is fineness of gold

A

parts of pure gold in 1000 parts of alloy
100% gold-1000 fineness
75% gold-750 fineness

64
Q

What are the types of gold

A

type 1 and 2, 3, 4

65
Q

What is type 1 gold

A
  • soft, for simple inlays
66
Q

what is type 2 gold

A

-medium, 2-3 surface inlays and onlays

67
Q

What is type 3 gold

A

hard, crown and bridge

68
Q

what is type 4 gold

A

extra hard, partial dentures

Dental Materials (6 decks)

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