composite 1

Question 1

what are the applications of direct filling materials?

Answer 1

new caries
abrasion/erosion
failed restoration/2nd caries
trauma

Question 2

what are the ideal properties of direct filling materials?

Answer 2

mechanical
-strong, rigid, hard
bonding to tooth
thermal properties
aesthetics
handling/viscosity
smooth surface finish/polishable
low setting shrinkage
radiopaque
anticariogenic
biocompatible

Question 3

of the 2 components of composite resin, which is hard and which is soft?

Answer 3

fillers = glass=hard
resin = soft

Question 4

what are the ingredients in composite resin?

Answer 4

filler particles
resin
camphorquinone
-photo initiator
dimethacrylates
-allow mechanical properties to vary
silane coupling agent
-allows intimate contact between filler & resin

Question 5

what filler particles can be used?

Answer 5

microfine silica
quartz
borosilicate glass
lithium aluminium silicate
barium aluminium silicate

Question 6

what resin monomers are used?

Answer 6

BIS-GMA
-product of bisphenol-A and methacrylate
urethane dimethacrylates

Question 7

what are the key characteristics of monomers?

Answer 7

difunctional molecule

undergoes free radical addition reaction-generates growth of monomer molecules

Question 8

what is camphorquinone activated by?

Answer 8

blue light

Question 9

what is caused by the reaction of camphorquinone and blue light?

Answer 9

produces radical molecules
these initiate free radical addition polymerisation of BID-GMA
leading to changes in resin properties
causes degree of conversion in resin

Question 10

what resin properties can be changed by camphorquinone?

Answer 10

increased molecular weight, so increased viscosity, so increased strength

Question 11

why are low weight dimethacrylates added?

Answer 11

to adjust viscosity & reactivity

Question 12

what is the function of a silane coupling agent?

Answer 12

preferentially bond to glass and resin

normally water will bond to glass filler particles, preventing resin from bonding to glass surface

Question 13

how do silanes achieve coupling?

Answer 13

methoxy groups hydrolyse to hydroxy groups react with absorbed water or -OH groups in filler

Question 14

where is composite used?

Answer 14

where aesthetics important
class III,IV,V permanent restorations
class II limited occlusal wear
labial veneers
inlays, onlays
cores
modified forms as luting cements

Question 15

what are the classifications of composite?

Answer 15

filler type
curing method
-light/self
area of use
anterior
-microfilled, submicron hybrid
posterior
-heavily filled
universal
-submicron hybrid
handling characteristics

Question 16

what are the 3 handling characteristics of composite?

Answer 16

condensable
-amalgam feeling-greater porosity
syringeable
-good adaption, less porosities, easy to apply
flowable
-lower filler content, more shrinkage, difficult to apply

Question 17

how does filler size range impact volume filled?

Answer 17

if only large filler particles, % uptake is small
by adding smaller particles greater vol. uptake
hybrid has high vol. uptake

Question 18

what are the effects of adding filler particles?

Answer 18

improved mechanical properties
lower thermal expansion
lower polymerisation shrinkage
less heat of polymerisation
improves aesthetics
some radiopaque

Question 19

how does light curing occur?

Answer 19

blue light 449nm
one paste
polymerisation setting reaction
-free radicals break resin C=C bonds
forms solid, strong material