Resin Based Composites Flashcards by anisah h

What is an example of the heavy resin?

UDMA: urethane dimethacrylate

BIS-GMA: bisphoenol A glycldyl methacrylate

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Which two types of resins are inside composite?

Heavy

Diluant

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What is an example of a diluant resin?

TEGMA: triethylene dimethacrylate
MMA: methyl methacrylate

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What are the fillers used in composite?

Quartz and silica (sio2)

Quartz is just a differnt structure of silica

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What size are the filler particles?

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

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What is the problem with the traditional filler sizes?

They have a poor surface finish and rough

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What is the problem with the microfilmed fillers?

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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What is the advantage of the hybrid fillers?

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

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What is the purpose of the coupling agent?

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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What material is used as the coupling agent?

Usually a silane

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

Gamma MPTS

Gamma methacryloxypropyltrimethoxysilane

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What is the purpose of the initiator system in composite?

2 components

Produces free radicals that initiate polymerisation

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What is the purpose of hydro quinine?

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

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T/F composites are radiopque?

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What makes composite radiopque?

Heavy metal fillers containing barium and strontium salts

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How do most composites cure?

Blue light with a wavelength of 460-480nm

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

Alpha DI ketone eg Camphoroquinone

Amine

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What can inhibit polymerisation?

Oxygen

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

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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What other types of curing method are there for composites?

Chemically cured

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

nn dihydroxyl p toludine and benzoyl peroxide

Reaction starts as soon as they are mixed together

What is the typical setting shrinkage for composites?

2-4%

How can we reduce setting shrinkage?

Increase filler loading and use larger monomers

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

How much rise in temp is there upon setting?

6 degrees

What is the working time and setting time for composite?

Working time is unlimited | Setting time is 40s

What is the effect of increasing filler loadin?

Polymerisation shrinkage is reduced | Coefficient of thermal expansion reduces

How can composite deteriorate?

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

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

The spaces reduce hence polymerisation shrinkage

Where does the shrinkage occur?

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

Which techniques are there to reduce shrinkage?

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

T/F chemically cured compostes shrink less?

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

What is silorane?

Cyclic monomer derbies from siloxane a and oxiranes

What is the settin shrinkage for siloranes?

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

What is the effect if the siloxane backbone in siloranes?

This is hydrophobic so reduced chance of water sorption | Better colour stability

What is the effect of oxiranes moieties?

This leads to cat ionic polymerisation

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

What are viscous bonding resins?

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

What is super bond?

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

What can happen with nano sized fillers?

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

Aesthetics of the composite are controlled by which composer?

Filler particles

How much is the filler loading in composite?

60-70% filler

Silanes are what kind of compound?

Bifunctional

What happens when the light is shone in the composite?

Some absorbed by pigments and fillers Some scattered Some is transmitted

Darker shades mean what?

Absorbed more light therefor has shorter depth of cure

The more fillers mean what?

More likely to be scattered and thus shorter depth of cure

How much intensity f light is needed?

300milliwatts/ sq cm

What do colloid fillers do?

Bounce the light around inside so increase depth of cure

What causes intrinsic staining of composite?

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