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Janes' Veterinary Dentistry_CP > Phillips science of dental materials > Flashcards

Phillips science of dental materials Flashcards

1
Q

According to Phillips science of dental materials, which of these materials displays the best wetting, which displays the worst?

A

Clean glass is best, angle approaches 0

Teflon is worst, angle is >90 degrees

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2
Q

According to Phillips Science of dental materials,

What is depicted in this graph by points

A (no plastic deformation has occurred),

B (0.2% plastic deformation has occurred),

C (Material fractured),

D (slope of this portion of the line?

A

A - proportional limit

B - Yield strength (0.2%)

C - Ultimate strength

D - Elastic modulus

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3
Q

According to Phillips Science of dental materials,

These are stress strain curves for 3 materials undergoing tensile stress.

What do letters A-F represent?

A

A, C, E (and F) Represent the ultimate tensile strength (stress required to fracture) of materials A, B and C

B, D, and F (also E since E=F) represent the proportional limit - end of the linear part of the stress/strain curve or amount of stress a material can withstand before plastic deformation occurs.

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4
Q

According to Phillips Science of dental materials,

These are stress strain curves for 3 materials undergoing tensile stress.

What material has the highest modulus of elasticity?

A

Material A - steepest straight portion of stress strain curve

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5
Q

According to Phillips Science of dental materials,

These are stress strain curves for 3 materials undergoing tensile stress.

What do letters G, H and I represent?

A

The ductility of materials C, B, and A respectively.

This is the percent elongation in the plastic phase of deformation.

A is most ductile

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6
Q

According to Phillips Science of dental materials,

These are stress strain curves for 3 materials undergoing tensile stress.

Which material is most brittle? Which is least?

A

Most brittle is C - has no plastic phase of deformation, breaks before any plastic deformation occurs

Least brittle is A - has the longest plastic phase of deformation.

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7
Q
A
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8
Q

According to Phillips science of dental materials,

What Contact angle indicates no wetting

A

180

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9
Q

According to Phillips science of dental materials,

what contact angle indicates complete wetting?

A

0

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10
Q

According to Phillips science of dental materials,

What is the difference between adhesion and cohesion?

A

adhesion is the sticking of a substance to something different, cohesion is how well atoms/molecules stick to other atoms/molecules that are the same

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11
Q

According to Phillips science of dental materials,

What is wetting?

A

The ability of a liquid to maintain contact with a solid surface; it reflects the intermolecular interactions when the two are brought in intimate contact.

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12
Q

According to Phillips science of dental materials,

What is a thixotropic material?

A

Property of gels and other fluids to become less viscous and flow when subjected to steady shear forces through being shaken, stirred, squeezed, patted, or vibrated. When the shear force is decreased to zero, the viscosity increases to the original value. Also known as shear thinning, in which the greater the applied shear force, the less the resistance to flow

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13
Q

According to Phillips science of dental materials,

What is creep?

A

Time-dependent plastic strain of a solid under a static load or constant stress.

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14
Q

According to Phillips science of dental materials,

What is the coefficient of thermal expansion>?

A

AKA (linear coefficient of expansion)—Change in length per unit of the original length of a material when its temperature is raised by 1 K (1 °C).

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15
Q

According to Phillips science of dental materials,

What is corrosion?

A

Chemical or electrochemical process in which a solid, usually a metal, is attacked by an environmental agent, resulting in partial or complete dissolution

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16
Q

According to Phillips science of dental materials,

What is brittleness?

A

Relative inability of a material to deform plastically before it fractures.

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17
Q

According to Phillips science of dental materials,

What is Compressive stress

A

Compressive force per unit area perpendicular to the direction of applied force.

18
Q

According to Phillips science of dental materials,

What is Compressive strength

A

Compressive stress at fracture.

19
Q

According to Phillips science of dental materials,

What is Ductility?

A

Relative ability of a material to elongate plastically under a tensile stress. This property is reported quantitatively as percent elongation.

20
Q

According to Phillips science of dental materials,

What is Elastic strain?

A

Amount of deformation that is recovered instantaneously when an externally applied force or pressure is reduced or eliminated.

21
Q

According to Phillips science of dental materials,

What is Elastic modulus?

A

(also modulus of elasticity and Young’s modulus)—Stiffness of a material that is calculated as the ratio of elastic stress to elastic strain.

22
Q

According to Phillips science of dental materials,

What is Flexural strength?

A

(bending strength or modulus of rupture)—Force per unit area at the instant of fracture in a test specimen subjected to flexural loading.

23
Q

According to Phillips science of dental materials,

What is Flexural stress?

A

bending stress —Force per unit area of a material that is subjected to flexural loading.

24
Q

According to Phillips science of dental materials,

What is Hardness?

A

Resistance of a material to plastic deformation, which is typically produced by an indentation force

25
Q

According to Phillips science of dental materials,

What is Plastic strain?

A

Irreversible deformation that remains when the externally applied force is reduced or eliminated.

26
Q

According to Phillips science of dental materials,

What is pressure? What is stress?

A

Pressure—Force per unit area acting on the surface of a material Stress—Force per unit area within a structure subjected to a force or pressure

27
Q

According to Phillips science of dental materials,

What is the proportional limit?

A

Magnitude of elastic stress above which plastic deformation occurs.

28
Q

According to Phillips science of dental materials,

What is resilience?

A

The amount of elastic energy per unit volume that is sustained on loading and released upon unloading of a test specimen.

29
Q

According to Phillips science of dental materials,

What is shear stress?

A

Ratio of shear force to the original cross-sectional area parallel to the direction of the applied force.

30
Q

According to Phillips science of dental materials,

What is shear strength?

A

Shear stress at the point of fracture

31
Q

According to Phillips science of dental materials,

What is stress?

A

Force per unit area within a structure subjected to a force or pressure

32
Q

According to Phillips science of dental materials,

What is Strain?

A

Change in dimension per unit initial dimension. For tensile and compressive strain, a change in length is measured relative to the initial reference length.

33
Q

According to Phillips science of dental materials,

What is Stress concentration?

A

Area or point of significantly higher stress that occurs because of a structural discontinuity such as a crack or pore or a marked change in dimension.

34
Q

According to Phillips science of dental materials,

What is ultimate strength?

A

stress at the point of fracture (ultimate strength).

35
Q

According to Phillips science of dental materials,

What is tensile stress?

A

Ratio of tensile force to the original cross-sectional area perpendicular to the direction of applied force.

36
Q

According to Phillips science of dental materials,

What is tensile strength?

A

Tensile stress at the instant of fracture.

37
Q

According to Phillips science of dental materials,

What is Toughness?

A

Ability of a material to absorb elastic energy and to deform plastically before fracturing; measured as the total area under a plot of tensile stress versus strain.

38
Q

According to Phillips science of dental materials,

What is yield strength?

A

The stress at which a test specimen exhibits a specific amount of plastic strain.

39
Q

According to Phillips science of dental materials,

What happens to a material when stress is applied to a material that is below the proportional limit, and the stress is removed?

A

It will return to original shape as below the proportional limit only elastic deformation occurs

40
Q

According to Phillips science of dental materials,

What happens to a material when stress is applied to a material that is beyond the proportional limit, and the stress is removed?

A

It will not return to it’s original form as some plastic deformation will have occurred.

Janes' Veterinary Dentistry_CP (87 decks)

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