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Dental Materials > Dental Materials Pt. 2(12-26) > Flashcards

Dental Materials Pt. 2(12-26) Flashcards

1
Q

hydrophobic surface properties

A

composite put into tooth

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2
Q

hydrophilic surface properties

A

tooth surface

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3
Q

composite and tooth being opposite of each other (hydrophobic vs philic) adds…

A

strength to the bond

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4
Q

the angle a force by the jaw is applied to a tooth or composite effected the amount of force

A

the contact angle

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5
Q

different angles of the jaw can have

A

different forces

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6
Q

molecules can have both hydrophobic

A

and hydrophilic components (adhesives- bind to composite and tooth so compatible with both surfaces)

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7
Q

types of corrosion in metals

A

Galvanic corrosion
structure selective corrosion
crevice corrosion
stress corrosion

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8
Q

degredation in ceramics caused by

A

hydrolysis

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9
Q

hydolysis in ceramics

A

dissolution of oxides created by H-bonds (fluoride treatments dissolve ceramics)

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10
Q

polymers degraded by

A

hydrolysis

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11
Q

hydrolytic degredation in polymers caused by

A

water (absorb water and causes dimensional changes)
enzymes
bacteria

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12
Q

degradation products are related to

A

toxicity (mercury and plastics absorbed by body over time and cause harm)

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13
Q

Stress strain curve y axis

A

stress

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14
Q

stress strain curve x axis

A

strain

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15
Q

steep angle on stress strain curve

A

stiff and brittle, shatters with sharp forces

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16
Q

food resembling steep angle

A

pretzel

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17
Q

middle angle on stress strain curve

A

stiff and ductile, deforms then fails

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18
Q

food resembling middle angle

A

tootsie roll

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19
Q

low angle on stress strain curve

A

flexible and ductile, lots of manipulation before it breaks

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20
Q

food resembling low angle

A

liquorish

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21
Q

tendency to deform along an axis with opposing forces (stress and strain)

A

modulus

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22
Q

before failure or fraction occurs

A

toughness

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23
Q

before deformation occurs

A

resilience

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24
Q

how does heat affect mechanical properties

A

decrease strength because material becomes pliable and easily manipulated

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25
Q

creep

A

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

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26
Q

impressions want to be taken out____ to retain___

A

quickly to retain best impression without deformation

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27
Q

the ability of a material containing a crack to resist further fracture

A

fracture toughness

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28
Q

single cycle (force) overload such as biting on popcorn cornel leads to

A

cracks

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29
Q

cyclic stresses are

A

slow cracks propogating over time (fatigue of teeth) caused by soft foods

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30
Q

teeth are not completely rigid and can lead to

A

abfractions

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31
Q

how the teeth articulate with each other creating an ideal environment for mastication

A

buccal lingual stability

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32
Q

how do cavities lead to B-L instability?

A

taking out cavity removes tooth material and weakens structure, putting more stress on remaining tooth and causing cusp fractures

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33
Q

in composite resins, resin helps

A

processing and handling

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34
Q

in composite resins, filler helps

A

modulus and wear resistance

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35
Q

in composite resins, the role of coupling agent

A

bonding between filler and matrix

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36
Q

resin ______ viscosity and filler _____ viscosity, but decreases flowability

A

increases viscosity, increases viscosity (which ultimately improves mechanical properties)

37
Q

types of curing

A

chemical
heat
light

38
Q

what is corsslinking

A

the linking of polymers within resin which can alter density with number and degree of crosslinking

39
Q

crosslinking increases or decreases strength

A

increases

40
Q

cross linked groups need to be ______ for this process to be effective in increasing strength

A

bonded together

41
Q

smaller fillers are

A

better

42
Q

smaller fillers match

A

tooth structure and have better wear properties

43
Q

smaller fillers allow for better/worse polishing and finishing

A

better

44
Q

micron (fine) fillers

A

.5-3 um

loaded at 77-88wt%

45
Q

nano (microfine) fillers

A

.04-.2um
tendency to aggregate
38% maximum loading percentage

46
Q

nano in polymer matrix

A

20-30um particles
loading up to 50-60%
reduces aggregation and no coupling agent

47
Q

these form very strong bonds between fillers and resin

A

coupling agents

48
Q

coupling agents add what groups and what do they bond to

A

add methacryalte groups that can bond with polymer chains to surface of filler

49
Q

Shrinkage

A

density change of monomers into polymers

50
Q

shrinkage is important for

A

direct compostite restorations and materials that require dimensional stability

51
Q

shrinkage can cause cracks that lead to

A

secondary caries

52
Q

Components of glass ionomer cements

A

acidic polymer (polyacid)
basic class
water
modifiers (tartaric acid)

53
Q

glass ionomers are cured by

A

acid- base reaction

54
Q

reaction of poly acid and glass creates

A

salt bridges that form from poly acid to glass

55
Q

difference between composite bonds and glass ionomer bonds

A

composite has cross bridges between polymers and glass ionomer has salt bridges between poly acid and basicglass

56
Q

glass ionomers release

A

fluoride to help tooth strength once set

57
Q

difference between adhesives and composites

A

adhesives are 0-10% filler and composites are 70-80% filler

58
Q

adhesives are base on

A

composite resin chemistry

59
Q

hydrophilic modifiers promote

A

bonding

60
Q

enamel and dentin are hydrophilic/phobic

A

hydrophilic

61
Q

compsites are hydrophilic/hydrophobic

A

hydrophobic

62
Q

ahesive layers are hydrophibic/philic

A

both

63
Q

how do sealants differ from composites?

A 
preventative material
low viscosity (easy to flow/coat surface)
bonding is mostly mechanical (etching)
not for longevity
64
Q

oxygen inhibition layer in sealants interferes with

A

radical polymerization

65
Q

why is oxygen inhibition a problem?

A

surface is uncured and this is problem because sealants are so thin

66
Q

classes of impression materials

A

hydrocolloid and elastomers

67
Q

properties of hydrocolloid

A

alginate, irreversible, lacks some accuracy, sets via chemical and temperature

68
Q

properties of elastomers

A

higher tear strength, stable dimensions, rubber like polymer

69
Q

con of elastomers

A

expensive

70
Q

alginates are ___based

A

water based

71
Q

alginate is ___ crosslinked

A

calcium cross linked

72
Q

calcium cross linked is part of

A

initial reaction while material is still workable

73
Q

calcium cross links react with

A

sodium alginate to form gel

74
Q

advantages of alginate being water based

A

use water temp to manipulate setting time

75
Q

the colder the water

A

the slower the setting time

76
Q

advantages of alginate

A

cheap, easy, fast, tastes fine, hydrophilic, displaces blood and saliva

77
Q

disadvantages of alginate being water based

A

undergoes shrinkage or expansion with loss/gain of water

78
Q

syneresis

A

loss of water to surroundings

79
Q

imbibition

A

gain water from surroundings

80
Q

other disadvantages of alginate

A

limited detail, single pour only, work quickly, low dimensional stability

81
Q

what determines time alginate material will set

A

sodium phosphate levels (water temps)

82
Q

heating

A

expand

83
Q

cooling

A

contract

84
Q

fillers reduce

A

water soprtion

85
Q

water sorption promotes

A

hydrolysis

86
Q

water sorption degrades

A

matrix and matrix filler bonding

87
Q

smear layer is removed by

A

etching

88
Q

spherical

A

molten alloy blown through nozzle (wetted with less mercury than lathe cut

89
Q

expansion vs contraction steps

A
  • initial contraction when alloy is absorbing mercury
  • expansion from formation and growth of y1 and y2
  • final absorption of mercury again causes contraction

Dental Materials (3 decks)

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