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Dental Materials > Fundamentals of Material Sciene > Flashcards

Fundamentals of Material Sciene Flashcards

1
Q

What are the occlusal force ranges seen in the posterior teeth?

A

200-3500N

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2
Q

What are the average forces seen in the bicuspids, cuspids, and incisors?

A

300, 200 and 150N

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3
Q

What is the equation and unit for stress?

A

Force(N)/Area

Pascal(Pa)

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4
Q

What are the two basic types of stress and explain them.

A

Axial: Two forces end to end
Shear: Moving across each other.

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5
Q

What direction does fragmentation occur in tensional and compressional stresses?

A

Tensional: Break inward.
Compressional: Break outward.

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6
Q

What is the definition of strain?

A

Deformation in a body due to stress.

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7
Q

For a stress-strain curve, define the following terms: Proportional limit, Yield point, Ultimate tensile strength, Fracture strength.

A

Proportional Limit: It is th highest point on the straight line where strain is equal to strength.
Yield Point: It is a constant and the point where material begins to act as a plastic
Ultimate Tensile Strength: Maximum stress before failure.
Fracture strength: stress at which a brittle material fractures.

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8
Q

When referring to Stress-Strain curves, where is the elastic region and where is the plastic region?

A

Elastic region is the area under the curve before the PL. The plastic region is the area under the curve after the PL.

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9
Q

Differentiate between the elastic limit and proportional limit.

A

Elastic Limit: Region of the stress-strain curve before the proportional limit.
Proportional Limit: The highest stress at which the stress strain curve is a straight line.

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10
Q

What is yield strength?

A

The stress at which the materials begin to function in a plastic manner. Has defined values of .1%, .2% or .5%.

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11
Q

What is elastic modulus?

A

The measure of elasticity of a material.

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12
Q

What is poisson’s ratio referring to?

A

The ratio seen when an object is stretched and the internal compression that will be seen.

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13
Q

Define ductility and malleability.

A

Ductility: Ability to be drawn and shaped into a wire.
Malleability: Ability to be hammered or rolled into thin sheets.

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14
Q

Define resilience.

A

The ability of a material to resist permanent deformation.

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15
Q

Define fracture toughness.

A

The ability to be plastically deformed without fracture.

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16
Q

What is the term matamerism mean?

A

When the properties of a material cause it to have different colors in different lighting.

17
Q

What is a metameric pair?

A

Pair of objects whose colors match in one light but will not in another.

18
Q

What is opalescence?

A

When a rainbow color is given off on the interior of an object.

19
Q

Define the difference between fluorescence and phosphorescence.

A

Fluorescence is emission of light by object that has absorbed light of different wave length
Phosphorescence is when it does not immediately release the light absorbed, but will emit it for a long time after.

20
Q

Define hue, chroma and value.

A

Hue: is the dominant color IE red or green.
Value: Identifies the lightness or darkness of a color
Chroma: Degree of saturation of a particular hue.

21
Q

what are the colors in the following shades A, B, C, D?

A

A- reddish brown
B- Reddish yellow
C- Greyish
D- Reddish grey

22
Q

What does viscoelasticity refer to?

A

Materials with properties dependent on loading rate and elastic behavior.

23
Q

What does viscosity refer to?

A

Resistance of a fluid to flow.

24
Q

Define hardness.

A

Resistance to permanent surface indentation.

25
Q

Define adsorption.

A

A liquid or gas adheres to the surface of solid or liquid and decreases surface energy.

26
Q

Define absorption.

A

Substrate diffuses into solid material by diffusion process

27
Q

Define sorption.

A

When adsorption and absorption exist at the same time.

28
Q

What does wetting mean?

A

Power of a liquid to spread on the surface of the solid.

29
Q

What is an opalescent material?

A

One that is able to scatter shorter wavelengths of light.

30
Q

What is index refraction?

A

Ratio of light velocity in vacuum to velocity in medium.

31
Q

What is scattering coefficient?

A

Fraction of incident light flux lost by reversal of direction in elementary layer.

32
Q

What is heat of fusion?

A

Heat required to convert 1 g material from solid to liquid.

33
Q

What is specific heat?

A

Heat needed to raise 1g of material by 1 degree C.

34
Q

What does dielectric mean?

A

Material that is able to provide electrical insulation.

35
Q

What is galvanism?

A

Results from difference in potential in the presence of metallic restorations.

36
Q

What is water sorption?

A

Amount of water absorbed on the surface and into the body of material.

Dental Materials (10 decks)

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