Brainscape's Knowledge GenomeTM

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


See full index

Dental Materials > Fundamentals 2 > Flashcards

Fundamentals 2 Flashcards

1
Q

What are mechanical properties?

A

Change of material dimensions due to external forces, such as mastication

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

What is viscosity?

A

Resistance of a fluid to flow.

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

Viscosity measures __________. The higher the viscosity, the ___________ and _______ resistance to flow

A

internal friction

internal friction, greater

Thiccer materials are most viscous

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

Higher viscosity materials behave like ______ while lower viscosity materials behave like ______

A

solid

liquid

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

What is the shear thinning phenomena?

A

It describes the affect on viscosity of a material if subjecting to stress.

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

Shear Thinning describes a ______ in viscosity as stress is ______.

Is this Newtionian?

A

Decrease

Added

no

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

What word is used to describe materials whose viscosity is unaffected by external stress?

A

Newtionian

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

Shear Thickening describes a ______ in viscosity as stress is ______.

Is this Newtonian?

A

increase, stress

NO

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

Shear Thinning examples

A
  1. Squeezing ketchup out of a bottle
  2. Squeezing toothpaste out
  3. Blood in our body as it flows
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

High to low viscosity describes ______.

The vice versa describes what?

A

Shear thinning

Shear thickning

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

Examples of Shear Thickening

A

Cornstarch

Moonsand

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

Why is viscosity important?

A
  1. Viscosity can change during preparation of materials
  2. Dispensing of dental material into tissue so it reaches pits and fissures
  3. Consistency and Manipulation ability of material
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the ideal viscosity of impression materials?

A

Low viscosity outside the mouth so it captures all anatomy but increasing viscosity in the mouth so it sets!

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

What is viscoelasticity?

A

Elastic + Viscous Behavior

Springy + Dampening behavior where materials behaves like solid and fluid

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

What is the difference of the Stress/Strain curve between fully elastic materials and viscoelastic ones?

A

Fully Elastic Materials will have the same linear path for load and unload.

Viscoelastic Materials will have a slight convexity for the load and a slight concavity for the unload.

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

Viscoelastic materials ______ energy when stress is________ . As a result the Stress Strain curve is ________.

What shape does it form?

A

lose , loaded-unloaded.

NOT proportional

A Hysteresis

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

Describe the strain vs time graphs for materials with the following properties.

Elastic

Viscoelastic

Viscous

A

Elastic- It will look like a rectangle. Increase in strain on y-axis, strain will be consistent with constant stress. When stress is removed strain will drop right back to zero.

Viscous- Strain will gradually increase linearly (sloped) as stress is applied. Strain will be consistent with constant stress. HOWEVER, when stress is removed, strain does not recover. ( Sloped line + 0 slope line

Viscoelastic - Stress will cause a convexed increase in strain. The elastic property will attempt to recover the material when stress is reduced caused a vertical decrease in strain. However, the viscous property will prevent full elastic behavior and cause a concave decrease. Looks like Shark fin

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

The more viscoelastic, the more ______ behavior.

A

Viscous

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

Purely elastic materials dissipate energy when load is applied then removed.

True or False

A

FALSE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Plastic deformation results in a _________ of energy which is uncharacteristic of _____ materials.

A

Loss

Elastic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Viscous materials loose energy through the ______ cycle because the ______________.

How can we quantify this energy?

A

loading/unloading

energy lost during loading is never fully recovered

Area in between hysteresis!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is creep?

A

Effect of constant stress over TIME on strain

Think coat hanger.

Strain will increase in a convex curve
Stress will remain constant (Slope 0 horizontal)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is stress relaxation?

A

Effect of constant strain over time on stress.

Stress will decrease in a convex fashion
Strain will remain constant (Slope 0)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are the 5 viscoelastic dental materials?

A
  1. Dentin
  2. Enamel
  3. Cells
  4. Impression Material
  5. SOME acrylic dentures
25
Q

How do we calculate dimensional change?

A

((New-Initial)/ Initial ) / 100

26
Q

What can cause contraction and expansion?

A

Temperature
Water Intake
Mechanical (Stress)
Polymerization

27
Q

We want the material with the ____ dimensional changes.

28
Q

What are bulk properties?

A

Mechanical, electrical or thermodynamical properties

Effect on organism, taste, nutritional value

Material density

Size and distribution

29
Q

What are surface properties?

A

Wettability

Flowability

Reactivity

30
Q

Why are surface properties important?

A

This is what interacts with environment.

31
Q

Why are bulk properties important ?

A

The add functionality to the material

32
Q

What is hardness?

A

The measure of the resistance to localized plastic deformation induced by either mechanical indent or abrasion.

33
Q

What is the hardness test?

A

Describes how much a material indents due to the load of a material.

TIP of load insertion in indentation of material is measured

34
Q

What is the difference between the hardness tests?

A

The shape of the tip

35
Q

The ______ properties of the tip material must be similar to the ______ of the material being measured in a hardness test.

A

Surface

Bulk

36
Q

Brinell Hardness Test

Tip Shape
What materials are tested with this?

A

Ball

Metals

37
Q

Rockwell Hardness Test

Tip Shape

A

Cylinder with 120 degree cone shaped indenter

Widely used

38
Q

Vickers Hardness Test

Tip Shape
What materials are tested with this?

A

Square-based pyramid shape tip

VERY SMALL material

39
Q

Why is the Vickers Hardness test important?

A

It has a very high resolution so it can be used for materials that change at the MICRON level

100 micron view

40
Q

Nano-indentation

Tip Shape
What materials are tested with this?

A

BERKOVICH TIP- 3-side Pyramidal

Diamond tip

very very small shape

4 micron view

41
Q

Which hardness test has the SMALLEST spatial resolution?

A

Nano-indentation w/ berkovich tip

42
Q

High hardness correlates with high ___________.

A

Wear resistance

43
Q

What is wettability?

A

How well does a liquid spread over a surface?

44
Q

How is wettability measured?

A

Contact angle between surface and tangent of water

45
Q

Non-wetting surface

A

180 degree contact angle

Water is a perfect ball

46
Q

Perfectly wetting surface

A

0 degree contact angle

Water is spread and coating surface

47
Q

Wetting

A

90 degree contact angle

Water is a flatter hemisphere

48
Q

Hydrophilic surfaces will produce contact angles _____________.

A

Less than 90 degrees

High surface detal

49
Q

Hydrophobic surfaces will produce contact angles at __________.

A

More than 90 degrees

Low surface detail

50
Q

What is surface detail?

Which material have highest surface detail?

A

How much can the material pick up of a surface?

Hydrophilic because hydrophobic materials will not coat the surface

51
Q

High surface energy describes the property of just one material.

True or False?

A

FALSE

TWO Material interaction

52
Q

High surface energy indicates _________ interaction.

These tend to be hydro______.

A

High

Hydrophilic

53
Q

What materials have high surface energy?

A

Metal, Kapton, Polyester, ABS, Acrylic

54
Q

What materials have low surface energy?

A

Polyestyrene

Acetal

EVA

Teflon

55
Q

Pan material is made of _____. This is why things don’t stick!

56
Q

What can affect the wettability/surface energy of a material?

A

Cleanliness of substrate (dust,saliva, particles)

Roughness

57
Q

What word can be interchanged with surface energy?

58
Q

The less wettable a substance is, the _________ contact angle.

Dental Materials (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions