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Resin Composites Flashcards

1
Q

in the 1950’s/1960’s what were used?

A

silicates

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2
Q

silicates were the earliest what?

A

tooth coloured material

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3
Q

silicates are the product of?

A

an acid base reaction of aluminasilicate glass, phosphoric acid

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4
Q

properties of silicates?

A

release F
moisture sensitive
erosion prone
brittle

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5
Q

what were used in the 1960’s/1980’s?

A

acrylics

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6
Q

where were acrylics derived from?

A

denture making products

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7
Q

what form did acrylics come in?

what type of set were they?

A

powder to liquid

chem set = limited working time

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8
Q

what were acrylics powder component?

A

polymethylmethacrylate pmma beads under 50nanometres

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9
Q

liquid portion of acrylics?

what was the chem activator?

A

methyl methacrylate monomer

chem activator = tertirary amine

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10
Q

acrylic setting reaction is?

A

free radical addition polymerisation

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11
Q

stages of a free radical addition polymerization of methyl methacrylate?

A

activation
initiation
propogation
termination

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12
Q

what happens at the termination stage?

A

chain attaches to impurity/free radical or further growing chain

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13
Q

what is the mechanism of polymerization?

A

free radical addition

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14
Q

material contracts on?
reaction is?
what gives poor colour stability?
must use correct?

A

polymerization
exothermic
tertiary amine not all used up
powder:liquid

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15
Q

compared to silicates, acrylics are less? exhibit?

A

less prone to erosion, soluble, acidic, britlle

exhibit lower thermal diffusivity

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16
Q

acrylics match?
do not use long term if?
setting reaction is?
residual mma causes?

A

tooth shade
if amine present
exothermic
pulp irritancy

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17
Q

acrylics interact with?
contract what % by volume?
low?
poor?

A

eugenol
6%
low hardness
poor abrasion resistance

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18
Q

in 1951 Knock and Glenn?

A

introduced inert filler particles to reduce shrinkage = also weakened the material

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19
Q

in 1963 Bowens composite had?

A

BISGMA resin matrix

coupling agent and filler particles

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20
Q

what is a resin composite?

A

a combination of 2 different chemical materials with distinct interface separating the components and properties which could not have been achieved alone.

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21
Q

early composites retained?

later became?

A

acrylics free radical addition polymerization - 2 pastes mixed together = reduced working time and incorporated porosities
later = light cured

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22
Q

resin matrix includes?

A

methacrylate/dimethycrylate monomers e.g BISGMA
includes monomers e.g TEGMA
inhibitors

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23
Q

what does TEGMA allow?

A

controls viscosity
facilitates manufacturers filler addition
easier clinical handling

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24
Q

what does the viscosity of the matrix polymer do?

A

reduces mobility of unreacted monomers

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25
what do unreacted monomers allow?
space for chairside repair
26
what does the C to C double bond take part in?
take part in free radical polymerisation
27
in new products based on silaranes, ring opening occurs, producing what?
expansion that offsets shrinkage | still an overall contraction
28
types of silaranes?
siloxanes - hydrophobicity | oxiranes - ring opening polymerisation
29
how are they cationic cured?
``` camphorquinone - photosensitiser iodium salt electron donor - decomposes iodium salt to an acidic cation ring opening polymerisation less shrinkage ```
30
what kind of fillers can be used?
quartz silica glasses - aluminasilicate, borosilicate, barium oxide
31
what kinds of coupling agents?
6-methacryloxypropylthimethaxyslane = gamma silane difunctional - methacrylate characteristics - silane interacts and bonds with glass good wetting = 1g->412m2
32
if you increase the % of filler what happens to surface hardness?
increased surface hardness
33
if you increase the % of filler what happens to the setting contraction?
decrease in % volume setting contraction
34
if you increase the % of filler what happens to the thermal expansion?
decreased thermal expansion
35
In what forms composites be activated chemically?
powder/liquid mixed paste/liquid mixed encapsulated
36
early light set composite was? | composite light set today was?
early - UV | today - camphorquinone - protects eyes, sets a little under operating light
37
how does camphorquinone cause setting?
yields the necessary free radicals to start polymerisation becomes excited at 460-480nm (visible blue light) most readily generated by quartz halogen lights
38
how does shrinkage occur?
resins are susceptible to shrinkage on polymerisation may be modified methacrylate or a chemical that on setting expands due to ring opening mechanism - e.g oxirane = expansion in resin volumes offsets to a degree the shrinkage
39
what aspect of the filler controls the properties?
type concentration particle size/distribution
40
resin and filler are useless without a?
coupling agent
41
what does a coupling agent do?
transfers stresses generated under loading from rigid/brtille filler to more flexible and ductile polymer matrix
42
what does the filler act as?
a shock absorber
43
how are composites classified?
by mode of activation | filler particle size/distribution
44
conventional composite particle size? by weight?
1-50micrometre | 60-80% by weight
45
microfilled composite?
0.01-0.1um | 30-60% by weight
46
hybrid?
``` mean = 0.04um hybrid 75% 1 8% 2 total = 83-90 by weight ```
47
nanocomposites?
particles less than 1um
48
handling classifications?
packable - highly viscous, packaging = challenge | flowable - more fluid less filler
49
intended clinical application | ISO 4049 type 1? type 2?
1 - cavities including occlusal surfaces | 2 - all other polymer based filling and restorative material
50
for a material to be on the market what must it conform with?
ISO 4049
51
what happens to the viscosity of composite on leaving the tube?
increases
52
what kind of set does composite have?
exothermic
53
where does the setting contraction go towards?
not towards light source
54
thermal properties of composite?
mismatch tooth for thermal expansion = risks marginal prelocation thermal diffusivity matches dentine
55
if chemically activated what is the working time like?
less working time
56
extended working time if activated how?
light activated gradual set from outer to inner distance light from surface and use incremental curing
57
physical properties of composite are reduced with what?
porosities
58
what is considered to be more important than compressive strength?
tensile and flexural strength
59
what is tribology?
composite changes with function/loss of resin rich outer layer
60
thermal properties of composite are proportional to what?
filler content
61
if filler is increased what happens to the coefficient of heat expansion?
increase
62
mechanical properties of composite are dependent on?
filler content and type efficiency of coulping degree of porosity
63
increased porosity and reduced coupling, what happens to the strength?
reduced strength with porosity | reduced strength with coupling by 30%
64
increased porosity and reduced coupling, what happens to the amount of fatigue composite can take?
reduced fatigue with porosity | reduced fatigue with coupling by 30%
65
why may composite stain?
resin matrix can take up fluids e.g wine
66
what creates a picture frame stain?
marginal deterioration

Dental Materials (13 decks)

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