Composites

Question 1

Composite definition

Answer 1

Material with 2+ distinct, structurally complementary substances (metals, ceramics, glasses, polymers) combine to produce structural/functional properties not present in any individual component

Question 2

Composite structures

Answer 2

MACRO composites
Separate materials bonded together
Ex: metal-ceramic restorations, veneers

Question 3

Composite materials

Answer 3

MICRO composites

constituent added to material to enchance its properties

Question 4

composite material fibers can be arranged…

Answer 4

aligned

random

Question 5

Particulate fillers

Answer 5

widely used in polymer-ceramic composites

Resin-based composites

Question 6

What are the constituents of dental resin composites? which are the main ones?

Answer 6

DIMETHACRYLATE RESIN
INORGANIC FILLERS
coupling agents
polymerization inhibitors
initiator/activator systems
UV stabilizers

**if you increase the % of one of these, the composite increases the properties of that constituent

Question 7

Dimethacrylate resins

Answer 7

vinyl polymer - addition polymerization

Set resin - rigid and tough

Question 8

What are the most common monomers in dimethacrylate resins? what are they combined with?

Answer 8

Bowen’s resin - Bis-GMA
Urethane dimethacrylate - UDMA

These are combined with TEGDMA

Question 9

What is the function of TEGDMA in dimethacrylate resins?

Answer 9

reduces viscosity of liquid resin before setting

Question 10

Name the types of fillers used in resin composites

Answer 10

silica
barium glass
zirconia/silica

Inorganic/mineral/ceramic

Question 11

functions of fillers in resin composites

Answer 11

Improve strength and wear resistance
Less shrinkage on setting
radiopacity

Question 12

How much of resin composites do fillers make up? %

Answer 12

50-80%

Question 13

What is the function of coupling agents in resin composites

Answer 13

Covalently link the polymeric resin (organic) to the ceramic fillers (inorganic)
Important: provide mechanical continuity
Transfer loads between fillers/resin without disruption of the material - strengthens interface

Question 14

What kind of coupling agents are used in resin composites?

Answer 14

Silane compounds

Question 15

Function of polymerization inhibitors in resin composites

Answer 15

Stability on storage

Question 16

Function of initiator/activator systems in resin composites

Answer 16

Start polymerization of resin

Usually for visible light curing

Question 17

What is the function of UV stabilizers in resin composites

Answer 17

Prevent yellowing in sunlight

Question 18

What are the conditions for polymer reinforcement in resin compsites

Answer 18

• Adhesion between polymer and filler
• Filler should be more rigid than polymer (higher modulus of elasticity)
• Filler can act as load bearing component of composite

Question 19

What are the effects of inorganic fillers (particulate) in resin composites?

Answer 19

improve compressive strength
increase hardness
less setting shrinkage
lwoer coefficient of thermal expansion
radiopacity
esthetics

Question 20

What are the two sizes of particulate fillers in resin composites

Answer 20

microcomposite

nanocomposite

Question 21

Nanocomposite particulate fillers

Answer 21

Developed to improve polishing and wear characteristics of composite in relation to esthetics

Question 22

Why are MCR/PFMs used in dentistry?

Answer 22

Get benefit of good mechanical properties of metallic metal & esthetics and wear performance of ceramics
= esthetic, strong, tough restoration

Question 23

What are the 2 main concerns when using MCRs?

Answer 23

1. color of alloy - esthetics

2. ceramic-alloy interface adhesion

Question 24

What is the nature of ceramic-metallic bonding

Answer 24

micromechanical

chemical

Question 25

micromechanical bonding in MCRs

Answer 25

Microabrasions on surface of alloy coping improves friction/retention of ceramic

Question 26

Chemical bonding in MCRs

Answer 26

OXIDE LINKS | Oxides already present in ceramic can chemically bond to oxide in alloy at the high temps of firing the porcelain

Question 27

How the esthetic concern of MCRs dealt with

Answer 27

DIFFERENT LAYERING OF CERAMIC Layer adj to alloy - opaque to hide color of alloy Top layers - tooth looking appearance

Question 28

Veneer

Answer 28

Thin, semi translucent shell Usually made from porcelain Made to fit over existing tooth

Question 29

Applications of veneers

Answer 29

Cosmetic alternative for conditions affecting anteriors: - Closing space - Chipped teeth - Whitening - Ortho concerns

Question 30

Treating a tooth with a veneer is considered a ____ approach

Answer 30

conservative | Little/no tooth reduction

Question 31

How are veneers bonded

Answer 31

Adhesive resin | PERMANENT - extremely strong and durable

Question 32

Alone, veneers are very ____, but when bonded to enamel, the resulting structure is _____

Answer 32

brittle | strong, tough, durable (biomimetics)