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Dental Materials > Composite resins > Flashcards

Composite resins Flashcards

1
Q

What are the three types of components every compost has

A

Resin Matrix, Inorganic filler, and coupling agents

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2
Q

What (in general) makes up the resin matrix

A

monomer, initiator, inhibitors, pigments

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3
Q

How do the inorganic fillers affect cmpsts

A

creates strength, more filler ore strength

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4
Q

How can composites be classified

A

by monomer type, or filler particle type

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5
Q

What are two types of monomers

A

Methacrylate

silorane

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6
Q

What are the 4 types of compost particle

A

macrofil, microfilm, hybrid, nano

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7
Q

What do monomers due?

A

binds filler particles together providing workability.

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8
Q

What kind of money is sometimes mixed in with BisGMA to lower viscosity

A

TEGMA

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9
Q

What are the three steps of polymerization

A

Initiation
propagation
termination

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10
Q

What happens during initiation

A

chemical, light, or heat stimulus produce reactive free radicals

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11
Q

what happens during propagation

A

monomer units going due to free radical to form polymer network (think dominoes falling)
yields 50-60% conversion

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12
Q

Whats the average shrinkage noted with polymerization

A

1-6%

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13
Q

what is a good % by weight for composites..% by volume

A

50-86% by weight 35-71% by volume

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14
Q

what features give your composites less wear?

A

Smaller partial size to decrease abrasion
heavier filled to decrease attrition (large chunks breaking off)
non contact areas
less restoration surface area
restoration in anterior v posterior
higher cure

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15
Q

what do coupling agents do?

A

chemically bond filler particles to matrix

transfers stresses overal strength increases

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16
Q

what are the advantages of using light activation

A

longer working time
greater polymerization
reduced porosity
better color stability

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17
Q

what is the disadvantage to using a light cured resin

A

limited depth of cure

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18
Q

what are the two chemicals used in chemical activation

A

initiator-benzoyl peroxide

activator tertiary amine

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19
Q

Where do the radicals attack during polymerization

A

double carbon bonds of the resin

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20
Q

microfil have what particle size

A

40-50nm

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21
Q

nano composites have what particle size range

A

5-100nm

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22
Q

what are the micro hybrid particle sizes

A

.6 - 1 microns plus 40 nm particles

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23
Q

How does particle size affect polishability

A

smaller particles finer polished

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24
Q

do microfilms have a coupling agent

A

no, so inferior properties
also radiolucent
ok for class 5

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25
Q

Z250 is what class

A

microhybrid

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26
Q

what coupling agent do nano composites use

A

silane

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27
Q

what kind of filler distribution do nano composites have

A

broad with high loading increasing stregnth

28
Q

What aspect of nano composites increases polish retention

A

addition of nanometer filler particles

29
Q

Filtek supreme ultra is what % by weight filled

A

78%

30
Q

What are the two types of filler particles in Filtek Supreme Ultra

A

nanomers .02-.07 microns
nano clusters the act as single unit
.6-1.4microns

31
Q

controlled clinical studies say what when comparing wear of micro hybrid and nanofil

A

no sig difference in wear after 5 years but nanofil maintained a better polish

32
Q

Whats the difference between nano composites and nanohybrid

A

composite has just nanometer sized particles throughout matrix whereas hybrids also have conventional fillers like sillica

33
Q

What composite has the best flexural strength

A

Z250

34
Q

whats a drawback of Z250

A

higher polymerization shrinkage 3%

35
Q

how does composite clinical behavior comapre

A

limited studies
short observation times
large differences not easily demonstrated

36
Q

What is a newer developed monomer that supposedly decreases shrinkage

A

Silorane

37
Q

What is silorane

A

a ring monomer that opens during reaction.

uses camphorquinone and iodonium salt initiation

38
Q

does shrinkage matter?

A

Clinical study showed no advantage between siloxane v methacrylate in 5 year study

39
Q

Why are flowable composites flowable

A

less filler content and less viscous monomers (TEGMA)

40
Q

How do flowables compare to hybrids

A

mechanical properties are less and polymerization shrinkage is higher

41
Q

Do liners under direct composites improve marginal integrity or reduction of post op sensitivity

A

no clinical evidence for either

42
Q

Can flowables be used in class one preps

A

Controlled clinical studies showed no difference at two years between flowable and a nano fill similar results for class 2 restorations

43
Q

do self adhesive flowables work

A

less shear bond strength than etch/adhesive

44
Q

How does heating affect composites

A

reduces viscosity but doesn’t seem to affect other properties

45
Q

when testing depth of cure what must be the hardness of the deepest level to be considered cured

A

80% of top hardness

46
Q

how does depth of composite affect cure

A

deeper composites attenuate the light decreasing the cure (same with darker shades)

47
Q

what happens to cusps deflection with bulk placement

A

Increased due to C factor, but this may not be clinically significant

48
Q

which type of fill has been shown to contain greater porosity: Incremental or bulk

A

Incremental

49
Q

what properties might increase depth of cure for a composite

A

increased translucency, additional photo initiators, just more photo initiators

50
Q

what is sonic fill

A

Single step bulk fill, using trigger sided cure can get up to 5mm, sonic activation decreases viscosity but its expensive

51
Q

How do stress reducing monomers work

A

use fragmenting monomers that can break during polymerization reducing the stress on the prep.

52
Q

Are bulk fill flowables a definitive restoration

A

No, Require covering by a restorative composite. they are very translucent.
overall lack of clinical studies

53
Q

what are some advantages of dual cure composites

A

unlimited depth cure
less stress (but greater shrinkage) due to slower cure
less porosity because its bulk fill
equivocal fracture toughness

54
Q

What are some disadvantages of dual cure bulk fill composites

A

color stability. Amines can discolor over time
its incompatible with simplified bonding agents
2x microleakage

55
Q

what was the northern lights consensus statement on light cured bulk fill composites as far as advantages

A

may reduce placement time
may reduce air voids
may have stress reduction

56
Q

what was the northern lights consensus statement on light cured bulk fill composites as far as disadvantages

A

may need more than one increment depending on depth
need supplemental cure from buccal and lingual
learning curve
may not be as esthetic due to translucency

57
Q

are composites bio comparable to the pulp

A

yes with good seal

58
Q

are there allergic reactions to composites

A

rarely with hema

59
Q

any cytotoxicity of composities

A

maybe but short lived so not a chronic source

60
Q

from a biocompatibility standpoint why is degree of cure important

A

decreases free monomer.

61
Q

Whats BPA

A

Bisphenol A
Acts like estrogen
disruption in animal hormone activity but role in human hormone yet to be determined

62
Q

BPA and dental resins

A

BPA used to make most resins
salivary enzymes breakdown bis dma
detected in saliva and urine in minute amount
overall much less than consumer item

63
Q

how can reduce boa exposure

A

rubber damn

remove air inhibited layer

64
Q

study of BPA urinary concentrations

A

Transient increase in BPA concentration that was no longer detectable at 14 days

65
Q

ADA position onBPA

A

unwanted concern

Dental Materials (9 decks)

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