Composite

Question 1

What is the composition of composites

Answer 1

Organic matrix
Inorganic filler
Coupling agent

Question 2

What is the organic matrix

Answer 2

A plastic resin that polymerises forming a continuous phase that binds the filler particles

Question 3

What is the inorganic filler

Answer 3

Reinforcing particles and fibres dispersed in the resin matrix

Question 4

What is the coupling agent

Answer 4

Bonding agent that bonds the fillers to the resin matrix

Question 5

What is the monomer phase of the organic matrix

Answer 5

The chemically active component of the composite which polymerises to give a glassy polymer when set
It is viscous resin fluid

Question 6

What does the organic matrix do

Answer 6

Holds the fillers in place

Question 7

What can happen if there is too much matrix present

Answer 7

High setting contraction
Low modulus
Poor wear resistance
High creep

Question 8

What do low viscosity monomers cause

Answer 8

High levels of polymerisation shrinkage

Question 9

What do high viscosity monomers cause

Answer 9

Large molecular weight so less polymerisation shrinkage

Question 10

What does filler reduce

Answer 10

Polymerisation shrinkage

Question 11

What do high amounts of fillers improve

Answer 11

The mechanical properties of composite

Question 12

What is traditional filler type

Answer 12

Macrofill

Question 13

What is a disadvantage of macrofill

Answer 13

Dull appearance due to filler particles protruding from resin surface

Question 14

What is an advantage of microfill filler

Answer 14

Can be polished very smooth surface finish

Question 15

What is a disadvantage of microfill filler

Answer 15

Very large surface area of filler in contact with resin
Difficult to obtain a high filler loading

Question 16

What are 4 advantages of hybrid blended filler

Answer 16

Favourable physical and optical properties
Improved wear resistance
Surface morphology superior to conventional but inferior to microfilled resins
Radiopacity possible

Question 17

What is a disadvantage of hybrid blended filler

Answer 17

Increased surface roughness with time

Question 18

What is hydrophobic in composite

Answer 18

The resin

Question 19

What is hydrophilic in composite

Answer 19

Filler

Question 20

what is a coupling agent used for

Answer 20

To bond the filler to the resin

Question 21

How does the coupling agent work

Answer 21

The hydrophilic end of the coupling agent reacts with surface hydroxyl groups of the filler via a condensation reaction

Question 22

How do chemically activated resins (self cure) work

Answer 22

Activator and initiator interact chemically to produce radicals

Question 23

How do light cured resins work

Answer 23

The tertiary amine reacts with the light initiator to form free radicals which then start off the addition polymerisation reaction

Question 24

what does the 37% phosphoric acid do to dentine

Answer 24

Remove the smear layer and expose collagen fibres which are hydrophilic

Question 25

What does the primer do

Answer 25

It acts as a linking bridge between the hydrophilic and hydrophobic surfaces
It contains a hydrophilic monomer whose molecules are bifunctional

Question 26

What does bond contain

Answer 26

HEMA but also other hydrophobic monomers similar to those in the resin based composites to be applied next