Composite - Applications, Composition and Classification Flashcards
What are the 2 main components of composite resin
Glass filler particles and resin
Glass is hard whereas resin is soft
What are the other components of composite resin and what do they do
Camphorquinone - photo-initiator
Dimethacrylates - allow the mechanical properties to be varied
Silane coupling agent - allows intimate contact between filler and resin
Give examples of different filler particles
Various types of glass: Microfine silica Quartz Borosilicate glass Lithium aluminium silicate Barium aluminium silicate
What are the particle sizes of filler in conventional composite and what percentage volume do they take up
10-40 um
50%
What are the particle sizes of filler in microfine composite and what percentage volume do they take up
0.04-0.2 um
25%
What are the particle sizes of filler in fine composite and what percentage volume do they take up
0.5-3 um
60-70%
What are the particle sizes of filler in hybrid composite and what percentage volume do they take up
Range - 0.01-0.1 um and 1-10 um
70%
What are the common monomers used in composite resin
BIS-GMA
Urethane dimethacrylates
What are the characteristics of a monomer used in composite resin
Difunctional molecule - has C=C double bonds that facilitate cross liking
This generated growth of monomer molecules via free radical addition polymerisation
What is camphorquinone
A photo-initiator that needs blue light to be activated to produce electrically charged molecules which initiate polymerisation of BIS-GMA
What is the outcome of BIS-GMA polymerisation
Increased molecular weight, viscosity and strength
How much monomer is converted during polymerisation
35-80%
Describe how a island coupling agent works
It surrounds the surface area of the filler particles - providing efficient means of resin and filler coupling
How can composite resin be classified
By either:
Filler type
Curing method
Area of use
What are the different filler types of composite resin
Conventional
Micro filled
Hybrid
What are the different curing methods of composite resin
Light-cured
Self-cured
What are the different areas of use of composite resin and how does this impact what filler type is used
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
Describe a condensable material
Can be pressed into a cavity
Describe a syringeable composite
Good adaptation
The protruding material doesnt drop from its container
Describe a flowable composite
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
What are the effects of adding filler particles
Improved mechanical properties - strength, rigidity, hardness, abrasion resistance Lower thermal expansion Lower polymerisation shrinkage Less heat of polymerisation Improved aesthetics
How is the setting reaction initiated in self-cured composite
Two pastes are mixed together
How is the setting reaction initiated in light-cured composite
A single paste material activated using blue light (430-490nm)
Describe the chemistry of initiation of the setting reaction in light-cured composite
Blue light activates camphorquinone to form free radicals that then establish the polymerisation reaction
