composite 1 Flashcards
what are the applications of direct filling materials?
new caries
abrasion/erosion
failed restoration/2nd caries
trauma
what are the ideal properties of direct filling materials?
mechanical -strong, rigid, hard bonding to tooth thermal properties aesthetics handling/viscosity smooth surface finish/polishable low setting shrinkage radiopaque anticariogenic biocompatible
of the 2 components of composite resin, which is hard and which is soft?
fillers = glass=hard resin = soft
what are the ingredients in composite resin?
filler particles resin camphorquinone -photo initiator dimethacrylates -allow mechanical properties to vary silane coupling agent -allows intimate contact between filler & resin
what filler particles can be used?
microfine silica quartz borosilicate glass lithium aluminium silicate barium aluminium silicate
what resin monomers are used?
BIS-GMA
-product of bisphenol-A and methacrylate
urethane dimethacrylates
what are the key characteristics of monomers?
difunctional molecule
undergoes free radical addition reaction-generates growth of monomer molecules
what is camphorquinone activated by?
blue light
what is caused by the reaction of camphorquinone and blue light?
produces radical molecules
these initiate free radical addition polymerisation of BID-GMA
leading to changes in resin properties
causes degree of conversion in resin
what resin properties can be changed by camphorquinone?
increased molecular weight, so increased viscosity, so increased strength
why are low weight dimethacrylates added?
to adjust viscosity & reactivity
what is the function of a silane coupling agent?
preferentially bond to glass and resin
normally water will bond to glass filler particles, preventing resin from bonding to glass surface
how do silanes achieve coupling?
methoxy groups hydrolyse to hydroxy groups react with absorbed water or -OH groups in filler
where is composite used?
where aesthetics important class III,IV,V permanent restorations class II limited occlusal wear labial veneers inlays, onlays cores modified forms as luting cements
what are the classifications of composite?
filler type curing method -light/self area of use anterior -microfilled, submicron hybrid posterior -heavily filled universal -submicron hybrid handling characteristics
what are the 3 handling characteristics of composite?
condensable
-amalgam feeling-greater porosity
syringeable
-good adaption, less porosities, easy to apply
flowable
-lower filler content, more shrinkage, difficult to apply
how does filler size range impact volume filled?
if only large filler particles, % uptake is small
by adding smaller particles greater vol. uptake
hybrid has high vol. uptake
what are the effects of adding filler particles?
improved mechanical properties lower thermal expansion lower polymerisation shrinkage less heat of polymerisation improves aesthetics some radiopaque
how does light curing occur?
blue light 449nm one paste polymerisation setting reaction -free radicals break resin C=C bonds forms solid, strong material
