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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
what are the disadvantages of amalgam
- no color match - corrosion, tarnish - marginal breakdown - creep- open margins - high thermal conductivity
26
what is creep
creep causes amalgam to flow and the unsupported amalgam protrudes away from margins
27
what happens to the unsupported edges with creep
weak and become corroded, ditch around margins
28
What does polishing an amalgam do
decreases corrosion
29
what is used to polish amalgam from course to fine
bur pumice tin oxide
30
What are the main components of ceramic- a glass material
Kaolin Feldspar and quartz metallic oxides
31
What is Kaolin
a clay found on riverbanks, becomes cohesive when wet
32
what is feldspar and quartz
mined from the earth and can be ground into powders, similar to sand
33
what are metallic oxides
ceramic pigments
34
What happens to feldspar when its subjected to high temperature
they fuse and form glass of the same shape
35
what doesnt change when feldspar is heated to high temp
silica particles
36
because of the feldspar and silica actions in high temps this means
a cohesive mixture that can hold its shape is formed
37
What is the difference between ceramic and porcelain
different amounts of feldspar, kaolin and silica
38
how is porcelain made
fired, which is baking at a high temp
39
how is ceramic made
cast or machine milled
40
What is fusion temperature
temp at which grains of porcelain powder fuses to form a ceramic mass
41
What is a glaze
creates a smooth, translucent surface similar to enamel
42
What are properties of ceramic/porcelain
- excellent electrical and thermal insulator - low thermal expansion - low tensile strength - high compressive strength
43
What can porcelain be affected by
fluorine containing acids APF
44
What is a disadvantage of porcelain
harder than tooth structure, can cause wear of opposing teeth
45
What is a cad cam
computer that are used to design and cut ceramic restorations
46
What are veneers
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
What are the 2 types of veneers
direct and indirect
48
What are chemical/mechanical precautions for porcelain and composite
- Porcelain needs to be protected from APF | - Composite veneers are subject to scratchin
49
The lower the reactivity of metal the_____________*
higher its nobility
50
What are characteristics of noble metals
resistant to corrosion and oxidation, precious metals
51
WHat are characteristics of metals*
elements that conduct heat and electricity, lustrous, melleable and ductile
52
what are noble alloys
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
What is an example of a noble metal
gold alloys
54
What is the gold for in gold alloys
soft, contributes to color, tarnish, and corrosion resistant, malleable and ductility
55
what is the copper for in gold alloys
lowers melting temp, contributes to harness and strength and corrosion resistance
56
What is silver for in gold alloys*
neutralizes reddish color from copper
57
what is platinum in gold alloys
increases strength and melting temp
58
What is palladium in gold alloys
less expensive than platinum, same purpose
59
What are examples of base metal alloys
``` titanium nickel/chromium nickel/cobalt molybdenum tungsten ```
60
* what base metal alloy is not sued any more because of allergy concerns
Nickel/ Nickel chromium
61
what is a common base alloy, used in substructure for crowns
nickel chromium
62
What is a karat
parts of pure gold in 24 parts 100% gold=24 karat 75% gold=18 karat
63
What is fineness of gold
parts of pure gold in 1000 parts of alloy 100% gold-1000 fineness 75% gold-750 fineness
64
What are the types of gold
type 1 and 2, 3, 4
65
What is type 1 gold
- soft, for simple inlays
66
what is type 2 gold
-medium, 2-3 surface inlays and onlays
67
What is type 3 gold
hard, crown and bridge
68
what is type 4 gold
extra hard, partial dentures

Dental Materials (6 decks)

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