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Biomaterials Exam 1 > Composites > Flashcards

Composites Flashcards

1
Q

Composite definition

A

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

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2
Q

Composite structures

A

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

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3
Q

Composite materials

A

MICRO composites

constituent added to material to enchance its properties

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4
Q

composite material fibers can be arranged…

A

aligned

random

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5
Q

Particulate fillers

A

widely used in polymer-ceramic composites

Resin-based composites

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6
Q

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

A 
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

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7
Q

Dimethacrylate resins

A

vinyl polymer - addition polymerization

Set resin - rigid and tough

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8
Q

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

A

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

These are combined with TEGDMA

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9
Q

What is the function of TEGDMA in dimethacrylate resins?

A

reduces viscosity of liquid resin before setting

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10
Q

Name the types of fillers used in resin composites

A

silica
barium glass
zirconia/silica

Inorganic/mineral/ceramic

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11
Q

functions of fillers in resin composites

A

Improve strength and wear resistance
Less shrinkage on setting
radiopacity

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12
Q

How much of resin composites do fillers make up? %

A

50-80%

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13
Q

What is the function of coupling agents in resin composites

A

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

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14
Q

What kind of coupling agents are used in resin composites?

A

Silane compounds

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15
Q

Function of polymerization inhibitors in resin composites

A

Stability on storage

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16
Q

Function of initiator/activator systems in resin composites

A

Start polymerization of resin

Usually for visible light curing

17
Q

What is the function of UV stabilizers in resin composites

A

Prevent yellowing in sunlight

18
Q

What are the conditions for polymer reinforcement in resin compsites

A
  • 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
19
Q

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

A 
improve compressive strength
increase hardness
less setting shrinkage
lwoer coefficient of thermal expansion
radiopacity
esthetics
20
Q

What are the two sizes of particulate fillers in resin composites

A

microcomposite

nanocomposite

21
Q

Nanocomposite particulate fillers

A

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

22
Q

Why are MCR/PFMs used in dentistry?

A

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

23
Q

What are the 2 main concerns when using MCRs?

A
  1. color of alloy - esthetics

2. ceramic-alloy interface adhesion

24
Q

What is the nature of ceramic-metallic bonding

A

micromechanical

chemical

25
Q

micromechanical bonding in MCRs

A

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

26
Q

Chemical bonding in MCRs

A

OXIDE LINKS

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

27
Q

How the esthetic concern of MCRs dealt with

A

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

28
Q

Veneer

A

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

29
Q

Applications of veneers

A

Cosmetic alternative for conditions affecting anteriors:

  • Closing space
  • Chipped teeth
  • Whitening
  • Ortho concerns
30
Q

Treating a tooth with a veneer is considered a ____ approach

A

conservative

Little/no tooth reduction

31
Q

How are veneers bonded

A

Adhesive resin

PERMANENT - extremely strong and durable

32
Q

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

A

brittle

strong, tough, durable (biomimetics)

Biomaterials Exam 1 (7 decks)

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