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Restorative > Resin Based Composites > Flashcards

Resin Based Composites Flashcards

0
Q

What is an example of the heavy resin?

A

UDMA: urethane dimethacrylate

BIS-GMA: bisphoenol A glycldyl methacrylate

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1
Q

Which two types of resins are inside composite?

A

Heavy

Diluant

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2
Q

What is an example of a diluant resin?

A

TEGMA: triethylene dimethacrylate
MMA: methyl methacrylate

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3
Q

What are the fillers used in composite?

A

Quartz and silica (sio2)

Quartz is just a differnt structure of silica

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4
Q

What size are the filler particles?

A

Traditional 10-20 microns
Microfilled 10-50nm
Hybrid (15-20 microns and 10-50 nm)
Nano particles

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5
Q

What is the problem with the traditional filler sizes?

A

They have a poor surface finish and rough

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6
Q

What is the problem with the microfilmed fillers?

A

Difficult to get a filler loading of more than 20% so resin is cures and ground up mad filled resin chunks then used as filler for final resin to achieve filler loading of 50%

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7
Q

What is the advantage of the hybrid fillers?

A

Good compromise and can get small particle hybrids where largely parcules are 0.1-6 mincrons

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8
Q

What is the purpose of the coupling agent?

A

There is not inherent bonding between the filler and the resin and this without the coupling agent you would get cracks propagating

They form a covalent bond to the filler and resin

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9
Q

What material is used as the coupling agent?

A

Usually a silane

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10
Q

What is the name of the most common type of coupling agent used?

A

Gamma MPTS

Gamma methacryloxypropyltrimethoxysilane

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11
Q

What is the purpose of the initiator system in composite?

A

2 components

Produces free radicals that initiate polymerisation

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12
Q

What is the purpose of hydro quinine?

A

This is added at 0.5% and used to prevent polymerisation and thus extend the shelf life

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13
Q

T/F composites are radiopque?

A

T

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14
Q

What makes composite radiopque?

A

Heavy metal fillers containing barium and strontium salts

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15
Q

How do most composites cure?

A

Blue light with a wavelength of 460-480nm

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16
Q

What type of compounds are the initiatior and give an example ?

A

Alpha DI ketone eg Camphoroquinone

Amine

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17
Q

What can inhibit polymerisation?

A

Oxygen

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18
Q

What are the factors which affect the depth of cure for composites?

A 
Wavelength 460-480nm
Time of curing 40s
Power of light source 
Distance from source
Oxygen inhibition
Filler content 
Shade of composite
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19
Q

What other types of curing method are there for composites?

A

Chemically cured

20
Q

What are the activator and initiator system use in chemically cured composites?

A

nn dihydroxyl p toludine and benzoyl peroxide

Reaction starts as soon as they are mixed together

21
Q

What is the typical setting shrinkage for composites?

A

2-4%

22
Q

How can we reduce setting shrinkage?

A

Increase filler loading and use larger monomers

23
Q

T/F the reaction is for light cured is exothermic?

A

T

24
Q

How much rise in temp is there upon setting?

A

6 degrees

25
Q

What is the working time and setting time for composite?

A

Working time is unlimited

Setting time is 40s

26
Q

What is the effect of increasing filler loadin?

A

Polymerisation shrinkage is reduced

Coefficient of thermal expansion reduces

27
Q

How can composite deteriorate?

A

Wear: worn down by teeth and other material s
Stain: picks up stain at margins of of the surface is rough
Water sorptkon: can cause deterioration of mechanical properties and may occur over months and years

28
Q

What happens between the spaces of the monomers when they are cured?

A

The spaces reduce hence polymerisation shrinkage

29
Q

Where does the shrinkage occur?

A

Good bond: shrinkage occurs betwen material and tooth at the interface
Poor bond: shrinkage occurs in the bulk which will lead to failure

30
Q

Which techniques are there to reduce shrinkage?

A

Incremental building
Pulsed light curing (not sure how effective)
Cure through the enamel which cures the margin first and prevents stress in the bond
Increase filler loading
Cavity design

31
Q

T/F chemically cured compostes shrink less?

A

T
Likely because they have

internal pores which can expand to accommodate shrinkage of material

Longer pre gel phase: more chance of the stresses being relieved befor the final shape of the composite is made

32
Q

What is silorane?

A

Cyclic monomer derbies from siloxane a and oxiranes

33
Q

What is the settin shrinkage for siloranes?

A

Less than 1% since rings open up as length of monomer increase in the polymer form and this less gaps

34
Q

What is the effect if the siloxane backbone in siloranes?

A

This is hydrophobic so reduced chance of water sorption

Better colour stability

35
Q

What is the effect of oxiranes moieties?

A

This leads to cat ionic polymerisation

36
Q

T/F the light stability for siloranes of better than normal composite?

A

T

37
Q

What are viscous bonding resins?

A

When the VBR is used it accommodates composite shrinkage and relieve the stress

Eg Virtebond

38
Q

What is super bond?

A

Resin bonding system occurs on contact with water eg tissue surface which means where the polymerisation starts is where the bonding occurs at the tissue surface

39
Q

What can happen with nano sized fillers?

A

They can clump together acting as a normal filler and not a nano

40
Q

Aesthetics of the composite are controlled by which composer?

A

Filler particles

41
Q

How much is the filler loading in composite?

A

60-70% filler

42
Q

Silanes are what kind of compound?

A

Bifunctional

43
Q

What happens when the light is shone in the composite?

A

Some absorbed by pigments and fillers
Some scattered
Some is transmitted

44
Q

Darker shades mean what?

A

Absorbed more light therefor has shorter depth of cure

45
Q

The more fillers mean what?

A

More likely to be scattered and thus shorter depth of cure

46
Q

How much intensity f light is needed?

A

300milliwatts/ sq cm

47
Q

What do colloid fillers do?

A

Bounce the light around inside so increase depth of cure

48
Q

What causes intrinsic staining of composite?

A

Chemical reaction occurring in the composite and needs to be replaced!

Restorative (45 decks)

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