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Dental Materials > Dental Materials > Flashcards

Dental Materials Flashcards

1
Q

Three Classes of materials

A

metals
ceramics
polymers

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2
Q

mechanical properties of metal

A

hard, ductile (bends), strong

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3
Q

bonding of metal

A

1-3 electrons in their outer shell key in metallic bonds

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4
Q

free mobility of electrons makes them

A

thermally and electrically conductive

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5
Q

temperature while forming metal effects

A

the strength of the metal

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6
Q

molten metal leads to

A

polycrystalline structures (formation of grains)

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7
Q

metal is made to resist

A

deformation

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8
Q

mixing of metals makes

A

alloy

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9
Q

what metals make up amalgam

A

alloy + Hg

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10
Q

Mechanical Properties of ceramic

A

hard, brittle (shatters), strong

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11
Q

bonding types of ceramics

A

ionic and covalent (stronger than metallic bonds)

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12
Q

covalent bonds share or donate electrons

A

share

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13
Q

ionic bonds share or donate electrons

A

donate/accept

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14
Q

bonding of ceramics crystal wise are

A

semicrystalline or polycrystalline

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15
Q

ceramics melt at ____ temperatures to form

A

high

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16
Q

most common ceramics

A

SiO2
Al2O3
K2O

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17
Q

Mechanical properties of polymers

A

soft, ductile (bends), weak

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18
Q

bonding type of polymers

A

covalent bonds

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19
Q

long polymer chains (nonmetallic)

A

derive strength and properties form entanglement

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20
Q

free radical concept to make polymers

A

activation
initiation
propagation
termination

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21
Q

direct processing

A

stable material
rapid setting
room temperature
doesn’t last a long time

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22
Q

metal processing in general terms

A

high processing temperatures and indirect placement (except amalgam)

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23
Q

ceramic processing in general terms

A

high processing temperatures and indirect placement (exception: cements)

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24
Q

polymers processing in general terms

A

lower processing temperatures and direct placement (exception: indirect composites)
- impressions, temp crowns, restorations

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25
Q

Polymerization process Step 1

A

activation: free radical initiation

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26
Q

Polymerization process Step 2

A

initiation: free radical combination with monomer unit and double bond opening

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27
Q

Polymerization process Step 3

A

propagation: chain growth

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28
Q

Polymerization process Step 4

A

termination

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29
Q

polymerization can be initiated by:

A

light, heat, chemical mixin

30
Q

linear polymer cannot become

A

tangled because no long chain brances

31
Q

cross linked polymers can become

A

tangled because long chain branches and therefore mechanically stronger

32
Q

a composite is

A

a physical mixture of metals, ceramics, and polymers

33
Q

goal of composite

A

to achieve some intermediate properties between two material types

34
Q

rule of mixtures states

A

knowing phases present in strucutres of materials makes it possible to predict overall properties of combination

35
Q

role of fillers

A

chemically bond to resin phase to improve properties

  • increase filler volume
  • increase strength, modulus, viscosity, surface roughness
  • decrease shrinkage
36
Q

thermal expansion coefficient of tooth

A

9-11

37
Q

thermal expansion coefficient of amalgam

A

25

38
Q

thermal expansion coefficient of compostie

A

28-35

39
Q

ideally you want a composite that is close to the

A

tooth coefficient

40
Q

materials that are not insulators can spread temperature too fast and it will

A

cause pain

41
Q

composites have low …. and therefore dont need…

A

low thermal conductivity and do not need a base

42
Q

metals do or do not need a base in their composition

A

do

43
Q

color is defined in a

A

3D coordinate system

44
Q

hue

A

wavelength (color)

45
Q

value

A

intensity and brightness (white vs black)

46
Q

chroma

A

purity and concentration (density/intensity of color)

47
Q

metamerism**

A

two colors look the same under one light but then look different under another light

48
Q

mercury issues with amalgam

A

patients don’t like color/mercury
proper disposal of toxic material
some patients have reaction to amalgam

49
Q

operator issues with amalgam

A

controlling substance and removing wet surface

50
Q

mechanical properties of amalgam

A

brittle*
higher compressive strength than tensile strength
creep

51
Q

amalgam has good/poor edge strength

A

poor

52
Q

creep of amalgam

A

solid material moves slowly/deforms permanently under mechincal stress (long term)

53
Q

amalgam full strength at

A

1 week (basically same as strength after 24 hours)

54
Q

galvanic corrosion

A

between anode and cathode at interproximal contacts

55
Q

unpolished scratches (secondary anatomy) lead to:

A

lower pH and oxygen concentration of saliva

56
Q

chemical corrosion occurs form reaction with

A

sulfide ions on occlusal surface

57
Q

pits and scratches that aren’t polished

A

catch debris and cause corrosion

58
Q

gamma 1 (y1)

A

siver mercury

59
Q

gamma 2 (y2)

A

tin mercury

60
Q

Chemical composition

A

silver- 40-60%
Tin- 27-30
copper- 13-30
zinc- 1%

61
Q

Classification: High copper

A

> 12% copper

62
Q

high copper properties

A

longevity of restoration (resists deformation)

low creep values

63
Q

zinc containing properties

A

facilitatates lathe cut particles

improves corriosion resistance

64
Q

low copper

A

original mix (now high copper is used)

65
Q

elements used in alloying

A 
copper*
zinc
silver
tin
(indum, mercury, noble metals)
66
Q

Setting Reaction Phases

A

Initial contraction when alloy is absorbing mercury.
Expansion from formation and growth of y1 and y2.
Final absorption of mercury again causes contraction

67
Q

Starting alloy+ mercury

A

reaction phase

68
Q

Y steps

A

Y1 and y2 form initially (step 1), then Y2 dissapears (step 2)

69
Q

heat treatment of alloy

A

eliminates nonuniformity that exist in both lathe cut and spherical
- allows companies to control setting times of materials

70
Q

lathe cut

A

machined from cast ignot

Dental Materials (3 decks)

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