Test One: Behavior Of Materials

Question 0

rank the following materials according to increasing 
thermal diffusivity (decreasing thermal insulation ability): amalgam, gold alloy, dentin, cement base.

Answer 0

Dentin, cement base, amalgam, gold alloy

Question 1

rank the following materials according to increasing

thermal expansion: tooth, amalgam, unfilled acrylic, composite

Answer 1

Tooth, amalgam, composite, acrylic

Question 2

How is modulus of elasticity a structure insensitive property?

Answer 2

Property that is not sensitive to alteration to the structure of the material such as heat treatment, work hardening, or any other type of conditioning

Question 3

How does force relate to stress and strain?

Answer 3

It is directly proportional to both

Question 4

At what point does strain deviate/increase from what was expected?

Answer 4

Plastic deformation

Question 5

How do you determine modulus of elasticity of a material?

Answer 5

Stress divided by strain below the elastic/proportional limit (before plastic deformation)

Question 6

What determines toughness?

Answer 6

Energy required to fracture the material

Question 7

What determines resilience of a material?

Answer 7

Integrated area under only the elastic region is a measure of the ability of a material to store elastic energy (like a spring)

Question 8

Materials with a lot of plastic behavior are called what?

Answer 8

Ductile

Question 9

Materials with little plastic behavior are called what?

Answer 9

Brittle

Question 10

Two examples where elongation of metals is important clinically

Answer 10

1- burnishing the margin of a crown (low yield strength with gold alloys makes its easier to burnish)
2- bending of a clasp on a partial denture to adjust retention

Question 11

What happens during work hardening?

Answer 11

Metals are stressed above their proportional limit–become stronger and harder but more brittle

Question 12

Fracture toughness

Answer 12

the resistance of a material to brittle fracture when a crack is present in or at the surface of the material

Question 13

What is mode I for fracture toughness?

Answer 13

Tensile/opening mode. the values of stress and crack length can be used to calculate a parameter called KIc, which is a designation of the fracture toughness of a material

Question 14

The resistance of an object to indentation

Answer 14

Hardness

Question 15

rank the following materials according
to increasing hardness: acrylic resin, dentin, enamel, gold alloy, amal-
gam, dental porcelain, nonprecious alloys

Answer 15

Acrylic resin, dentin, gold alloy, amalgam, enamel, nonprecious alloys, and dental porcelain

Question 16

Thermal diffusivity

Answer 16

The speed with which heat flows through a material, taking heat capacity (the amount of heat that has to flow into a material to raise it one degree) into account

Question 17

The property of a material that expresses the amount that the material expands during firing heating/cooling

Answer 17

Thermal expansion