Composites

Question 1

What is a Composite?

Answer 1

A solid with 2 or more distinct constituent materials or phases(enamel, bone, dentin and reinforced polymers all qualify)

Question 2

Composite is normally referred to as:

Answer 2

reinforced polymer system used for restoring hard tissues

Question 3

What are the 4 components of a composite?

Answer 3

1. organic polymer matrix
2. Inorganic filler particles
3. Coupling agent
4. Initiator-accelerator system

Question 4

What usually makes up the organic polymer matrix?

Answer 4

Bis-GMA, UDMA or Silorane-new low-shrinkage monomer

Question 5

4 types of inorganic filler particles

Answer 5

1. quartz or glass
2. sol-gel derived ceramics
3. microfine silica
4. nanoparticles

Question 6

What is the biggest component of a composite by weight

Answer 6

Inorganic filler particles

Question 7

What do inorganic filler particles provide for composite

Answer 7

1. translucency

2. reduces shrinkage 3.reinforces resin matrix

Question 8

What does a coupling agent do?

Answer 8

forms a bond between inorganic filler particles and organic resin matrix. Also makes hydrophobic and enhances mechanical properies
-silane is most common

Question 9

What does the initiator-accelerator system do?

Answer 9

polymerize and cross-links system into a hardened mass Ex:camphorquinone absorbs blue light

Question 10

Purpose of composites

Answer 10

esthetics, high stress areas. (they have lower wear and lower expansion than acrylics and silica)

Question 11

Composites are classified by:

Answer 11

1. Shape
2. particle size
3. Particle distribution of the filler

Question 12

Are nano hybrids a true nanofill?

Answer 12

no because they are mixed with bigger chunks

Question 13

Nanofills particle size

Answer 13

1-100 nm

Question 14

Camphorquinone

Answer 14

absorbs blue light and starts curing process

is an initiator-accelerator

Question 15

how are composites polymerized

Answer 15

free radical addition polymerization of methacrylate monomers

Question 16

Stages of polymerization

Answer 16

1. intiation
2. Propagation
3. Termination

Question 17

What factors influence degree of polymerization?

Answer 17

vanderwalls space(molecular bond length) and free space(due to random thermal energy and rotational mvmt)

Question 18

Methods to decrease contraction during polymerization

Answer 18

1. add more inorganic filler
2. add more prepolymerized particles
3. use methylacrylate particles with HIGH molecular wieght

Question 19

Activation and polymerization methods inculde

Answer 19

• light activation via blue light (465nm)
• chemical activation
• dual curing (chem and light)

Question 20

how long does setting reaction continue?

Answer 20

24 hours

Question 21

when is mechanical strength attained after placing composite?

Answer 21

immediately after curing the restoration

Question 22

how long does it take composite to loose capability to flow when exposed to light?

Answer 22

60-90 seconds

Question 23

Setting times for chemically activated composites range from

Answer 23

3-5min

Question 24

What do inorganic oxides provide to a composite?

Answer 24

coloration

Question 25

What properties can be improved if composites are judiciously developed?

Answer 25

- modulus - strength - fracture toughness - wear resistance - thermal expansion - chemical corrosion resistance

Question 26

what size particles are mixed in micro hybrids?

Answer 26

.04-1 micrometers

Question 27

Microhybrid qualities

Answer 27

good stress and wear resistance but get dull with time

Question 28

what is cermet?

Answer 28

glasses fused with metals such as gold, silver and titanium

Question 29

what is the purpose of cermet?

Answer 29

to improve the strength of glass ionomers

Question 30

what are the properties of macrfills?

Answer 30

- early composites - spherical or irregular shaped particles - opaque - low resistance to wear

Question 31

What is a hybrid composite?

Answer 31

two types of fillers blended together, has irregular shapes -fine particles 2-4 micrometers and 5-15%microfine particles(usually silica)

Question 32

what makes up microhybrid composites?

Answer 32

77-84%filler by weight - fine particles size .04-.1 micrometer blended with microfine silica - has irregular shapes

Question 33

what does distribution of filler particles provide

Answer 33

efficient packing so high filler loading is possible

Question 34

Hybrids and microhybrids pros and cons

Answer 34

good clinical wear resistance, mechanical properties for stress-bearing spots Lose surface polish, becoming rough and dull

Question 35

purpose of fillers:

Answer 35

1. reinforce resin matrix 2. provide appropriate translucency 3. control volume shrinkage of the composite during polymerization

Question 36

Most common monomers used are:

Answer 36

aromatic dimethacrylates (also bisGMA and UDMA) -high viscosity so dilutants must be added

Question 37

coupling agent

Answer 37

silane applied to inorganic particles to surface treat the fillers before being mixed with the unreacted monomers

Question 38

which composite type has the best polish and esthetics?

Answer 38

Microfilled(but has higher shrinkage)

Question 39

Which composite has the highest volume of inorganic filler?

Answer 39

Nanocomposite 78.5%

Question 40

Which composite has the lowest volume of inorganic filler?

Answer 40

Flowable-syringeable and lower modulus | disadvantage: has higher wear

Question 41

Advantages of nanocomposite

Answer 41

high polish, high strength , high modulus

Question 42

disadvantage of microfilmed composite

Answer 42

higher shrinkage

Question 43

disadvantage of flowable composite

Answer 43

higher wear

Question 44

advantages of multipurpose composite

Answer 44

high strength high modulus

Question 45

are Glass ionomers classified as composites?

Answer 45

yes

Question 46

Glass ionomer properties include

Answer 46

water based material | acid-base setting reaction

Question 47

high elastic modulus

Answer 47

more stiff

Question 48

low elastic modulus

Answer 48

less stiff, higher fracture toughness