composite material
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name 5 different restorative materials
• composite resins • amalgam • glass ionomers • compomers • ceramics
when do you use direct filling materials
• new dental caries • abrasion / erosion • failed restoration / secondary caries • trauma
what are the ideal properties of composite
• mechanical • bonding to tooth / compatible with bonding systems • thermal properties • aesthetics • radiopaque • handling / viscosity • anticariogenic • smooth surface finish / polishing • low setting shrinkage • biocompatible
what traits are included in mechanical properties
• strength • rigidity • hardness want it to be strong enough to withstand forces and be long lasting
what are the 2 main components of composite
• glass ionomer particles > hard • resin material > soft > holds the particles together
what are the components of composite resin
• filler particles • resin • camphorquinone • low weight dimethacrylates • silane coupling agent
what is camphorquinone
the photo initiator
why is low weight dimethacrylates added
to improve the product
name filler particles in glass
• microfine silica • quartz • borosilicate glass • lithium aluminium silicate • barium aluminium silicate • others
compare the particle size and % volume of different types of composite
conventional: > Particle Size = 10-40um > % volume = 50 microfine > Particle Size = 0.04-0.2 um > % volume = 25 fine > Particle Size = 0.5-3um > % volume = 60-70 hybrid > Particle Size = range > % volume = 70
what is meant by hybrid composite?
a mix of large particles and smaller sizes
what does more filler particles do to the material
increases the hardness of the material
what monomers are used in resins
> BIS-GMA [reaction product of bisphenol-A and glycidyl methacrylate] > urethane dimethacrylates§
what are the key characteristics of monomer
> difunctional molecule • C = C bonds • facilitate crosslinking (needed for polymerisation reaction) > undergoes free radical addition polymerisation [need composite to be cured to be a rigid, strong material with a hard surface]
what is camphorquinone activated by
blue light (curing light)
what does camphorquinone produce
radical molecules (electrical charge) these initiate free radial addition polymerisation of BIS-GMA [goes from the paste like material to undergo polymerisation and from the cross links so they end up a much stronger material]
what changes does the the camphorquinone product / reaction lead to in resin properties
> increased molecular weight increased viscosity increased strength causes a degree of conversion of resin (35-80% unreacted monomer)
give an example of a low weight dimethacrylates
TEGDMA
why is low weight dimethacrylates added
to adjust viscosity and reactivity to improve the material [material would set too quickly without this being added so you would have no time to work in the patient’s mouth - allows more time as it slows it down a little]
why is silane coupling agent added
use to preferentially bond to glass and also bond to resin a good bond between filler particles and resin is essential so this helps with that
what effect does water have on the bond between filler particles and resin
normally water will adhere to the glass filler particles and this prevents resin from bonding to the glass surface
name resin-filler particle coupling materials (unsure if this is even a q im not sure what i meant in my notes lol typical x)
> silane eg methacryloxypropyltrimethoxysilane > methoxy groups hydrolyse to hydroxyl groups react with absorbed water or -OH groups in filler
what are the uses of composite
> aesthetic importance class III, IV and V permanent restorations class II - limited occlusal wear labial veneers inlays, onlays indirect technique) cores modified forms as luting cements (some dual cured)
what are the classifications of composite
> filler type curing method area of use handling characteristics