Composite Flashcards
What is the composition of composites
Organic matrix
Inorganic filler
Coupling agent
What is the organic matrix
A plastic resin that polymerises forming a continuous phase that binds the filler particles
What is the inorganic filler
Reinforcing particles and fibres dispersed in the resin matrix
What is the coupling agent
Bonding agent that bonds the fillers to the resin matrix
What is the monomer phase of the organic matrix
The chemically active component of the composite which polymerises to give a glassy polymer when set
It is viscous resin fluid
What does the organic matrix do
Holds the fillers in place
What can happen if there is too much matrix present
High setting contraction
Low modulus
Poor wear resistance
High creep
What do low viscosity monomers cause
High levels of polymerisation shrinkage
What do high viscosity monomers cause
Large molecular weight so less polymerisation shrinkage
What does filler reduce
Polymerisation shrinkage
What do high amounts of fillers improve
The mechanical properties of composite
What is traditional filler type
Macrofill
What is a disadvantage of macrofill
Dull appearance due to filler particles protruding from resin surface
What is an advantage of microfill filler
Can be polished very smooth surface finish
What is a disadvantage of microfill filler
Very large surface area of filler in contact with resin
Difficult to obtain a high filler loading
What are 4 advantages of hybrid blended filler
Favourable physical and optical properties
Improved wear resistance
Surface morphology superior to conventional but inferior to microfilled resins
Radiopacity possible
What is a disadvantage of hybrid blended filler
Increased surface roughness with time
What is hydrophobic in composite
The resin
What is hydrophilic in composite
Filler
what is a coupling agent used for
To bond the filler to the resin
How does the coupling agent work
The hydrophilic end of the coupling agent reacts with surface hydroxyl groups of the filler via a condensation reaction
How do chemically activated resins (self cure) work
Activator and initiator interact chemically to produce radicals
How do light cured resins work
The tertiary amine reacts with the light initiator to form free radicals which then start off the addition polymerisation reaction
what does the 37% phosphoric acid do to dentine
Remove the smear layer and expose collagen fibres which are hydrophilic
What does the primer do
It acts as a linking bridge between the hydrophilic and hydrophobic surfaces
It contains a hydrophilic monomer whose molecules are bifunctional
What does bond contain
HEMA but also other hydrophobic monomers similar to those in the resin based composites to be applied next
