composite resins
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what type of patient would composite, compomer and RMGIC be used in?
low caries risk = composite compomer mid RMGIC high
what are the main components of composite?
Glass filler soft resin / DMA camphorquinone silane coupling agent
benefits of the glass/silica filler?
improved mechanical and handling properties lower thermal expansion lower shrinkage better aesthetics in smaller fillers
why use camphorquinone? How does it work?
Use it to cure at time of choice, extends working time light activator sensitive to blue light blue light hits camphorquinone and induces free radical addition polymerisation to dimethylacrylate
why is the low weight dimethyl-acrylate used?
to decrease viscosity and reactivity It is the flowable monomer component of the resin. It sets when the camphorquinone in the mix is hit by UV. It polymerises fast and has little shrinkage.
what is the soft resin used for?
used to allow manipulation of composite before it is set, e.g. BIS-GMA
why use a silane coupling agent?
creates a bond between the resin and the filler particles this helps to counter PCS
what properties make composite ideal for usage?
good aesthetics good handling qualities light or self cure anti-cariogenic radiopaque biocompatible (not all monomer polymerised though) polishable
what types of filler are there?
nano hybrid microfine fine conventional bulk
how is flowable composite different to conventional?
flowable composite has much smaller and less filler particles, hence increased viscosity however it is weaker. viscosity allows it to adapt to base of cavity
what thermal properties does composite possess?
low thermal conductivity low thermal diffusivity high thermal coefficient (not good)
benefits of light cure? and cons?
cure on demand extended working time less waste premature polymerisation from dental light shrinkage depth of cure light and material mismatch