Composite

Question 1

What is a composite material?

Answer 1

2 or more constituent materials with different physical or chemical properties that when combined, produce a material with characteristics different from the individual components

Question 2

What are some examples of composites in the human body?

Answer 2

Enamel, dentin, bone, muscle, cells

Question 3

What is resin composite?

Answer 3

Reinforced polymer used for restoring enamel and dentin

Question 4

What is the correct term for composite resin?

Answer 4

Polymer matrix composite or Particular-reinforced polymer matrix composite

Question 5

How are composites classified?

Answer 5

By particle size and percent distribution of inorganic filler

Question 6

What types of composites are best for restorative procedures?

Answer 6

Microfilled - best esthetics, good finish, continued smoothness, lacks strength; Hybrid - Good esthetics and strength - lacks long term smoothness

Question 7

What were the first polymeric direct restorative material?

Answer 7

Silicates in 1878

Question 8

What is acrylic restorative resin?

Answer 8

Unfilled, low molecular weight polymers without reinforcing filler particles

Question 9

What about composites made them better than acrylic restorative resin?

Answer 9

Improved physical properties (i.e. lower coefficient of thermal expansion)

Question 10

In multipurpose composites, what are the 4 major components?

Answer 10

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

Question 11

What are the organic polymer matrix materials that are common in multi-purpose composites?

Answer 11

Dimethacrylates (Bis-GMA), Urethane dimethacrylate (UDMA)

Question 12

What are the inorganic filler particles used in multipurpose composites?

Answer 12

• Glass/quartz, colloidal silica, or zirconia-silica nanoclusters

Question 13

What is the most common coupling agent?

Answer 13

Silane (organosilane) KNOW THIS

Question 14

What does silane do in multipurpose composites?

Answer 14

Acts as a coupling agent that binds the inorganic filler particles to the organic matrix; Forms a homopolymer film on the surface of the filler; Bond degrades in contact with water intraorally

Question 15

What are some common initiator-accelerator systems used in multipurpose composites?

how can the material set Hannah

Answer 15

Chemical cure, light cure, or dual cure

Question 16

By what reaction do resin monomers undergo to harden?

Answer 16

Free radical polymerization

Question 17

What is free radical polymerization inhibited by?

Answer 17

Oxygen - leaves a soft sticky surface, or oxygen inhibited layer

Question 18

What is the weakest part of a composite resin?

Answer 18

Matrix - needs filler particles

Question 19

If you have more filler, what happens?

Answer 19

Material is stronger and more abrasion resistant; Greater resistance to wear!

Question 20

If a composite has no filler, it is called _____________________. If it does have filler particles, it is called a ______________________.

Answer 20

Unfilled resin, filled resin

Question 21

What is the function of the filler?

Answer 21

To reinforce the resin matrix, provide the appropriate degree of translucency, and control the volumetric shrinkage during polymerization

Question 22

What are some common classifications of filler?

Answer 22

Microfilled, Microhybrids, Nano hybrids

Question 23

What is free radical polymerization?

Answer 23

Chain reaction requiring free radicals from either a chemical cure or a diketone-amine system in visible blue light; 3 stages; Inhibited by oxygen

Question 24

What are the three steps of free radical polymerization reactions?

Answer 24

Initiation, propagation, termination

Question 25

In initiator-accelerator systems, what is the photoactivator used with blue light?

Answer 25

"Camphorquinone

Question 26

What are the important properties of composites?

Answer 26

Working and setting time, Polymerization shrinkage, Thermal properties, Water sorption, Solubility, Color stability

Question 27

When considering the working and setting time of composites, what should be considered?

Answer 27

Light cured occurs on demand, continues for 24 hours; Chemical cure: 1-1.5 min working time, 4-5 min setting time

Question 28

What considering polymerization shrinkage, what can be done to reduce these effects?

Answer 28

Adding composite in 2mm increments independently can reduce the net effects of polymerization shrinkage; More filler = less shrinkage

Question 29

When considering the thermal properties of composites, what should be considered?

Answer 29

Linear coefficient of thermal expansion is higher for composites than enamel or dentin; "More polymer = more expansion

Question 30

When considering composites, what should be considered about water sorption?

Answer 30

It causes volumetric expansion; More sorption with microfine compared to microhybrids

Question 31

When considering composites, what should be considered about solubility?

Answer 31

Composites have varying solubility; Inadequate light intensity/duration -> inadequate polymerization -> Greater water sorption and solubility reduced resistance to wear

Question 32

When considering composites, what should be considered about color stability?

Answer 32

Composites are resistant to color changes due to oxidation but are susceptible to staining

Question 33

What are the mechanical properties of composite resins?

Answer 33

Strength and modulus, Knoop hardness, Bond strength to enamel and dentin, Depth of cure, Radiopacity, Wear rates, Biocompatibilty

Question 34

What is strength and modulus?

Answer 34

Flexural and compression strength of composite influences by volume % of filler particles; The higher the %, the stronger the composite; (hybrids better than microfilled)

Question 35

What is knoop hardness?

Answer 35

Microhardness of a material; Composites are less hard than enamel or amalgam; Can be misleading on composites with large filler particles

Question 36

The more filler you have =

Answer 36

more strength, will not polish as well

Question 37

The finer filler you have =

Answer 37

The more polishable it is

Question 38

What is bond strength to enamel and dentin?

Answer 38

Results from micromechanical retention; In dentin, hybrid layer of bonding agent and collagen is formed and bonding adhesive penetrates dental tubules

Question 39

What force holds composites into the tooth?

Answer 39

Micromechanical retention

Question 40

What is depth of cure?

Answer 40

Influenced by several factors: distance from source, intensity of source, curing time, scatter of light, color of composite, concentration of photo-initiator); Light source should be as close to surface w/o touching; Depth of cure is 2-2.5 mm

Question 41

Does a larger light source mean better?

Answer 41

No, you must consider irradiance which is different from size

Question 42

When using a light cure, should you tilt the light source to that it is angled?

Answer 42

No - it should remain perpendicular

Question 43

What is radiopacity?

Answer 43

Modern composites use atoms with high molecular weight allowing viewing of composites on radiograph (Barium)

Question 44

What atom is commonly used in composites to increase radiopacity?

Answer 44

Barium

Question 45

What are wear rates?

Answer 45

Early composites had significant wear; Current hybrid and posterior composites show acceptable wear

Question 46

What biocompatibility factors should be considered about composites?

Answer 46

All major components - ex. Bis-GMA - show cytotoxicity; Cured composites release very little of these components; Composites place directly over pulpal tissue pose a higher risk of adverse biological responses

Question 47

What does etching allow?

Answer 47

Phosphoric acid & bonding agent placement allow for micromechanical retention

Question 48

What should be considered about the mixing of composites?

Answer 48

Should be done with a coated metal or plastic spatula to avoid abrasion of metal and possible discoloration

Question 49

How can you place composites?

Answer 49

Using plastic or coated metal instruments, or using a composite gun

Question 50

Most chemical/duel cure composites are dispensed with _________________________.

Answer 50

Auto-mixing tips

Question 51

What is the range of output for Blue LED curing lights?

Answer 51

450-490 nm

Question 52

Can you look at the light when curing?

Answer 52

No

Question 53

Why is a specific range of wavelengths used in light curing?

Answer 53

Matches the absorption spectrum of camphorquinone

Question 54

For gross reduction of a composite, you should use a _____________________________. For final finishing, you should use a ___________________________.

Answer 54

Diamond/carbide finishing bur, or finishing disks/strips, Abrasive-impregnated rubber rotary instruments or rubber cup with polishing pastes

Question 55

Why should there be a smooth surface of restorations?

Answer 55

To prevent plaque retention

Question 56

What are the steps of the composite procedure?

Answer 56

Acid etch - 10-15 sec; Wash - excess water removal; Bonding agent - adhesive universal; Scrub into dentin - 20 sec; Thin with air - 5 sec; Light cure - 10 sec; Composite resin - per manufacturer's instructions - 20-40 sec