Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

lecture 7- composite (dental materials) > composites > Flashcards

composites Flashcards

1
Q

In terms of make up, which two types of phases does composite consist of?

A

a dispersed phase (filler particles) distributed within a continuous phase (matrix phase)…the matrix phase is often fluid at some point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

A dental composite has traditionally indicated a mixture of _______ glass particles within an _______ monomer that is polymerized during the application

A

silcate glass particles acrylic monomer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the function of the silicate glass particles in composite? function of acrylic monomers in composite?

A

silicate glass- provides mechanical strength and scatters light to produce enamel like translucency acrylic- make the initial composite mixture moldable and fluid so it can flow into preperations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are bonding systems for composites generally made of?

A

acrylic monomers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

name three ways a bonding system interacts with a prep.

A

micromechanically interlock with the etched surfaces seal the walls of the preparations copolymerize with the composite restorative material that fills the tooth preparation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

name some other terms we use for dental composite

A

composite restorative materials, filled resins, composite resins, resin composites, resin-based composites, or filled composites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

the earliest composites used were which? what were they mixed with? name some disadvantages of this material

A

silicates phosphoric acid and glass polymers were too soluble in the oral environment were too hard on the pulp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is PMMA? Disadvantage of MMA? Disadv of PMMA?

A

poly methyl meth acrylate the methacrylate monomer (MMA) contracted too much during polymerization, permitting marginal leakage PMMA was not strong enough to support occlusal loads

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

MMA matrices were replaced by which material?

A

BIS-GMA (a difunctional monomer)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is BIS GMA and UDMA (similar to BIS GMA) diluted with so they aren’t so viscous?

A

TEGDMA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

To increase the bond between the silica particles and the continuous resin phase, the silica particles are precoated with films of_______

A

silane coupling agents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are silane coupling agents?

A

difunctional molecules; one end bonds to the hydroxyl groups on the silica surface, the other is capable of copolymerizing with double bonds of monomers in the matrix phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

why are lithium and Aluminum used as filler particles? what filler particles are used to increase radioopacity?

A

makes the glass easier to crush to generate small particles Barium (Ba), Zinc (Zn), Boron (B), Zirconium (Zr), and Yttrium (Y) ions have been used to produce radiopacity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Pure silica occurs in several crystalline forms in addition to glass….name 3 of them

A

crystobalite tridymite quartz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Crystalline forms of silica are stronger and harder, but results in composites that are difficult to _______ what gives you a smoother polish?

A

polish using smaller filler particles (ie microfill instead of midifill)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which 3 silicate glasses are currently the most popular fillers?

A

arium, zinc, and yttrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The fluidity of a mixture of filler and matrix monomer is affected by the fluidity of the ______ and the amount of ______ The principle factor controlling fluidity in composite is what?

A

monomer and the amount of filler incorporated friction between the filler particle surfaces and the monomer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

As the filler surface area increases, the fluidity _______ Large filler particles have a relatively ________ amount of surface area per unit of filler particle volume

A

decreases small

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what happens to surface area when smaller filler particles replace large ones? This situation is further exacerbated for microfiller particles made of _____, which tend to agglomerate into chains

A

surface area increases SiO2

20
Q

Define Surface Roughness (RA)? Surfaces with roughness values of what are considered to be very smooth? what is the most common range when using submicron polishing pastes?

A
  • average up and down symmetry 1um 0.2 - 0.6um
21
Q

the most common classification of composite material is based on what?

A

The most common classification method is based on: filler content (weight or volume percent), filler particle size method of filler addition

22
Q

Almost all important properties of composites are improved by using higher _______ levels

A

filler

23
Q

Disadvantage of large filler particle size? Disadv of small filler particle use?

A

tough to polish weaker

24
Q

The degree of filler addition is represented in terms of what? Because silica is about 3 times as dense as the matrix polymer, 75 weight % filler is equivalent to about _____volume % filler

A

weight % or volume % of filler 50

25
Q

in dentistry, what is more common: using weight% or volume% to measure filler addition?

A

much easier to measure and formulate composites using weight percentages rather than volume percentages

26
Q

particle size for macrofill? midifill? minifill? microfill? nanofill?

A

Macrofill: 10-100 μm Midifill: 1-10 μm Minifill: 0.1-1 μm Microfill: 0.01-0.1 μm Nanofill: 0.005-0.01

27
Q

What is a hybrid composite? what is used to define the hybrid type

A

Composites with mixed ranges of particle sizes the largest particle size range is used to define the hybrid type

28
Q

what is a homogeneous composite? what is a heterogeneous composite? If it includes novel filler modifications in addition to conventional fillers, then it is called_____ composite

A

consists simply of filler and uncured matrix If it includes precured composites or other unusual filler, it is called heterogeneous modified

29
Q

what is a traditional or “conventional composite”? filler particle size?

A

they replaced the silicate composites filler particles are 8-10um in size

30
Q

another name for a microfill (0.02-0.04um) composite? What does having a small filler particle size do?

A

fine finishing composites The small filler particle produce high viscosities, requiring addition of more monomer diluents, along with a reduced overall filler content to make it workable

31
Q

To lessen the viscosity problem of small filler particles in microfill composites, 2 strategies were developed. Describe them. What were these types of composites called?

A
  1. the microfill composite was precured 2. then ground into 1-20 μm particle powder, which bonded with the new material, providing islands with better properties, but could still be finished nicely These are known as heterogeneous microfills (or organic filler composites)
32
Q

After it was learned that highly filled microfills were difficult to use, composites were formulated with particles in the microfill range and also 2-5 μm range These allowed for higher filler levels and also good finishing, and were called ______ composites

A

hybrid

33
Q

do nanofiller particles interact with visible light?

A

no, the filler particle size is below the wavelength range for visible light = NO SCATTERING OR ABSORPTION OF LIGHT

34
Q

adv for using non silicate based composite fillers?

A

Non-silicate-based compositions can be used for nanofillers because they are effectively invisible, and do not tend to agglomerate in chains like silica particles

35
Q

what is an adv of using non silicate based composites as nanofillers?

A

they are effectively invisible, and do not tend to agglomerate in chains like silica particles Nanofillers are so small that they fit between polymer chains, permitting very high filler loading levels while still maintaining workable consistencies

36
Q

what is the advantage to using fibers in composite? disadv? Fibers must be longer than 1um…WHY? what are the dimensions of most current fibers?

A

The main advantage is their strength along the fiber axis hard to pack them efficiently or to orient their direction addition of fibers less than 1um long are carcinogenic (ie asbestos) Most current fibers are from 20-40 μm long and 5-10 μm in diameter

37
Q

what are flowable composites? what procedures are flowable composites best used for?

A

**Low-viscosity** materials that possess particle sizes and particles size distributions similar to those of hybrid composites, but with reduced filler content pit-and-fissure sealants or small anterior restorations

38
Q

True/ False ? In general, the mechanical properties of flowable composites are superior to those of standard hybrid composites

A

FALSE Flowable composites are weaker

39
Q

how is packable composite different from flowable composite?

A

less stickiness higher viscosity (stiffness)

40
Q

_____ monomers for composites used in the United States traditionally have been based in BIS-GMA as the primary monome

A

Matrix

41
Q

T/F UDMA, which is more popular than BIS GMA in Europe, is predicted to have better adhesion and/or resistance to color changes than BIS GMA

A

FALSE clinical studies have not been able to show this

42
Q

how were the original composites cured? most popular way of curing composite today?

A

self cured (chemical cured) amine accelerators (but discoloured in 3-5 years) most popular= visible light cured

43
Q

in what situations can light curing be inadequate?

A

If the composite thickness exceeds 1.5 to 2.0 mm, the light intensity can be inadequate to produce complete curing, especially with darker composites Interproximal locations

44
Q

what has been done to overcome the disadvantages of light curing?

A

compositions are dual-cured, combining self-curing and light-curing Self-curing rate is slow and designed to cure only those portions not adequately light-cured

45
Q

List some light sources that can be used to cure composites

A

quartz-tungsten-halogen (QTH) plasma-arc (PAC) laser light-emitting diode (LED)

46
Q

Moving the tip of the curing light closer to the surface ______ the depth of the cure

A

INCREASES

lecture 7- composite (dental materials) (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions