Composite

Question 1

uses for composite

Answer 1

primary/secondary caries, abrasion, erosion, trauma

Question 2

mechanical properties of composite

Answer 2

smooth surface finish/polishable, low setting shrinkage, technique sensitive

Question 3

chemical properties of composite

Answer 3

thermal expansion coefficient is high, compared to tooth material and GIC/amalgam [bad]
- 25-68ppm *C
under cold stimulus, composite can shrink away from cavosurface margins
thermal conductivity and diffusivity are low [good]

Question 4

biological properties

Answer 4

biocompatibility is generally low, not usually anti-cariogenic but some release fluoride

Question 5

components of composite

Answer 5

filler particles, resin, camphorquinone, low weight dimethacrylates, silane coupling agent

Question 6

filler particles [component]

Answer 6

increase proportion of filler = decreased thermal expansion coefficient [good]
improve mechanical properties of material = strength, rigidity, hardness, abrasion resistance, low polymerisation contraction, greater strength, improved aesthetics
conventionally glass/quartz

Question 7

resin [component]

Answer 7

monomers are used, a difunctional molecule C=C, facilitates crosslinking and undergoes free radical addition polymerisation
BIS-GMA = bisophenol A and glycidyl methacrylate

Question 8

comphorquinone [component]

Answer 8

is the blue light activation, releases free radical, allows setting
free radicals bond to BIS-GMA resin which changes resin to increased molecular weight, viscosity and strength
degree of conversion of resin 35-80%
reacts with blue light at 440nm, 2mm depth cure

Question 9

low weight dimethacrylates

Answer 9

TEGDMA - triethylene glycol dimethycrylate
added to adjust viscosity and reactivity [like paint thinner]

Question 10

silane coupling agent

Answer 10

allows glass to preferentially bond to resin and glass rather than water [prevents water just bonding to glass filler]

Question 11

depth of cure definition

Answer 11

the depth at which material hardness is about 80% that of the cured surface

Question 12

things that can go wrong before restoration is complete

Answer 12

cavity preparation - caries left, unsupported enamel
bonding
contacts with teeth
placement
countering contraction stress
aesthetics

Question 13

configuration factor

Answer 13

the ratio of bonded to unbonded surfaces

Question 14

polymerisation contraction stress

Answer 14

pressure put on adhesive and tooth structure, can cause debonding and marginal gaps if incorrect

Question 15

high polymerisation contraction stress

Answer 15

not good, increased stress, deformation and fracture

Question 16

low polymerisation stress

Answer 16

good, reduced stress

Question 17

how should composite be placed

Answer 17

in increments, one layer on floor of cavity, walls of cavity shouldnt be joined together if can be avoided
this is how to reduce configuration factor and polymerisation contraction stress