Pres Res: Mechanical Properties of Dental Materials Flashcards Preview

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Flashcards in Pres Res: Mechanical Properties of Dental Materials Deck (20)
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1
Q

Type of deformation for elastic:

A

Recoverable

2
Q

Type of deformation for plastic:

A

Permanent

3
Q

The maximum stress that a material will withstand without permanent deformation:

A

Elastic limit

* looking at the material

4
Q

The greatest stress that a material will sustain without a deviation from the linear proportionality of stress to strain:

  • essentially same as elastic stress, but differs by definition.
  • looking at the graph.
A

Proportional limit

5
Q

The stress value at which a material exhibits a specified amount of strain:

A

Yield strength

* Usually 0.2% (percent offset) is used.

6
Q

The maximum stress that a material can withstand before failure in tension:

A

Ultimate Tensile Strength

7
Q

The stress at which a material fractures:

* not necessarily equal to ultimate strength.

A

Fracture Strength

8
Q

The slope of a line on stress-strain graph indicates:

A

Stiffness within elastic range.
Steep slope= stiff
Gradual slope= flexible

9
Q

Examples of brittle dental materials:

A

amalgam
composites
cements
ceramics

10
Q

The ability of a material to be plastically deformed:

A

Ductility

Ex: gold

11
Q

The resistance of a material to permanent deformation:

* area under elastic portion

A

Resiliency

12
Q

The resistance of a material to fracture:

* area under entire curve

A

Toughness

13
Q

The maximum stress that a material can withstand before failure in compression:

A

Ultimate compressive strength

14
Q

The maximum stress that a material can withstand before failure in shear mode:

A

Shear strength

15
Q

A measure of a material’s resistance to brittle fracture when a crack is present:

A

Fracture Toughness

16
Q

Viscosity (slope) remains constant:

Ex: water, some dental cements and impression materials

A

Newtonian fluid

17
Q

No flow until a certain shear stress is reached (yield point):
Ex: toothpaste
* Line starts higher up on y-axis

A

Plastic

18
Q

Decreasing viscosity (slope) as shear rate increases:
- easier to mix with increase stirring speed.
Ex: silicone impression materials some endodontic cements
* line looks ductile, runs low.

A

Pseudoplastic

19
Q

Viscosity (slope) increase with shear rate:
- Harder to mix with increased stirring (shear rate)
Ex: denture- base resins
* exponential line

A

Dilitant

20
Q

Time- dependent decrease in viscosity (slope):
- Yield pt. (similar to plastic)
- Not reversible shear stress/strain rate curve (structure alteration).
Ex: tap new ketchup bottle, flows (yield point), next time usually don’t have to tap to get flow.

A

Thixotropic