Composite - Applications, Composition and Classification

Question 1

What are the 2 main components of composite resin

Answer 1

Glass filler particles and resin

Glass is hard whereas resin is soft

Question 2

What are the other components of composite resin and what do they do

Answer 2

Camphorquinone - photo-initiator
Dimethacrylates - allow the mechanical properties to be varied
Silane coupling agent - allows intimate contact between filler and resin

Question 3

Give examples of different filler particles

Answer 3

Various types of glass:
Microfine silica
Quartz
Borosilicate glass
Lithium aluminium silicate
Barium aluminium silicate

Question 4

What are the particle sizes of filler in conventional composite and what percentage volume do they take up

Answer 4

10-40 um

50%

Question 5

What are the particle sizes of filler in microfine composite and what percentage volume do they take up

Answer 5

0.04-0.2 um

25%

Question 6

What are the particle sizes of filler in fine composite and what percentage volume do they take up

Answer 6

0.5-3 um

60-70%

Question 7

What are the particle sizes of filler in hybrid composite and what percentage volume do they take up

Answer 7

Range - 0.01-0.1 um and 1-10 um

70%

Question 8

What are the common monomers used in composite resin

Answer 8

BIS-GMA

Urethane dimethacrylates

Question 9

What are the characteristics of a monomer used in composite resin

Answer 9

Difunctional molecule - has C=C double bonds that facilitate cross liking
This generated growth of monomer molecules via free radical addition polymerisation

Question 10

What is camphorquinone

Answer 10

A photo-initiator that needs blue light to be activated to produce electrically charged molecules which initiate polymerisation of BIS-GMA

Question 11

What is the outcome of BIS-GMA polymerisation

Answer 11

Increased molecular weight, viscosity and strength

Question 12

How much monomer is converted during polymerisation

Answer 12

35-80%

Question 13

Describe how a island coupling agent works

Answer 13

It surrounds the surface area of the filler particles - providing efficient means of resin and filler coupling

Question 14

How can composite resin be classified

Answer 14

By either:
Filler type
Curing method
Area of use

Question 15

What are the different filler types of composite resin

Answer 15

Conventional
Micro filled
Hybrid

Question 16

What are the different curing methods of composite resin

Answer 16

Light-cured

Self-cured

Question 17

What are the different areas of use of composite resin and how does this impact what filler type is used

Answer 17

Whether the composite is used in an anterior or posterior location
This will determine which filler particle loading is preferred eg - heavily filled resins are most suited to posterior teeth as they’re more robust and can withstand high loads/stresses

Question 18

Describe a condensable material

Answer 18

Can be pressed into a cavity

Question 19

Describe a syringeable composite

Answer 19

Good adaptation

The protruding material doesnt drop from its container

Question 20

Describe a flowable composite

Answer 20

Lower filler content
More shrinkage
Difficult to apply
Viscosity is much lower such that it drops out of the delivery nozzle forming a small pool

Question 21

What are the effects of adding filler particles

Answer 21

Improved mechanical properties - strength, rigidity, hardness, abrasion resistance
Lower thermal expansion
Lower polymerisation shrinkage
Less heat of polymerisation
Improved aesthetics

Question 22

How is the setting reaction initiated in self-cured composite

Answer 22

Two pastes are mixed together

Question 23

How is the setting reaction initiated in light-cured composite

Answer 23

A single paste material activated using blue light (430-490nm)

Question 24

Describe the chemistry of initiation of the setting reaction in light-cured composite

Answer 24

Blue light activates camphorquinone to form free radicals that then establish the polymerisation reaction