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AVDC Flash Cards > Craig's Restoration Fundamentals of Material > Flashcards

Craig's Restoration Fundamentals of Material Flashcards

1
Q

Define Biomechanics

A

Study of how biological material interact and deform

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2
Q

Define Force

A

Generated when one body interacts with another (direct contact of distance (gravity))

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3
Q

Translation or deformation occurs with..

a. Body Constrained
b. No Constrain on body

A

a. If body constrained, deformation/change of shape occurs
b. If no constrain on body, then translation or movement of body occurs

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4
Q

Where is the highest occlusal force?

A

Highest is in posterior ridge closet to the mandibular hinge axis

The force decreases as it moves mesially

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5
Q

Define stress

A

When forces acts on constrained body, the body resists the force.

Internal reaction is equal in magnitude and opposite in direction to applied by external force

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6
Q

What is the formula for stress?

A

Stress = Force per area (Force/area)

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7
Q

What are the 2 basic types of Stress?

Sub types?

A
  1. Axial
    1. Tension
    2. Compression
  2. Shear
    1. Torsion
    2. Bending/Flexure
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8
Q

Define Tension

A

2 sets of forces directed away from each other in the same straight line

or

One end is constrained and the other end is subjected to a force directed away constraint

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9
Q

Define Compression

A

2 sets of forces directed towards each other in the same straight line

or

One surface is constrained and the other is subjected to a force directed toward the constraint

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10
Q

Define shear

A

2 sets of forces directed parallel to each other but not along the same straight line

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11
Q

Define torsion

A

Twisting of a body

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12
Q

Define Bending/Flexure

A

Applied bending moment

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13
Q

Define strain

A

change in length per original length of body when subjected to a load

Often reported as a %

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14
Q

Deformation from tensile force causes what change to the axis?

A

Elongation in the axis of the applied force

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15
Q

Deformation from compressive forces causes what change in the axis?

A

Compression/ shortening of the body in the axis of loading

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16
Q

What is this called?

Define it

A

Stress-Strain Curve

relationship of dental material studied by measuring the load and deformation and then calculating the corresponding stress and strain

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17
Q

Define A, B,

A

A: Proportional limits or elastic limits

Highest stress and which stress-strain curve is a straight line (i.e maximum stress that material will withstand WITHOUT permanent deformation)

B: Yield Strength

Point were material begins to functions in a plastic manner i.e. defines were transition from elastic to plastic behavior (estimates when material will start to deform permanently)

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18
Q

Define C, D

A

C: Ultimate Tensile/Compressive Strength

Maximum stress that a material can withstand before failure in tension or compression

D: Fracture Strength

Point at which a brittle material will fracture

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19
Q

Where is the elastic region?

Where is the plastic region?

A

area under 0-A = elastic region (able to return to normal length/ no deformation)

area under A-D = plastic region

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20
Q

Define Elongation

A

Deformation that results from the application of tensile force

Give indication of possible manipulation of alloy

Total elongation is a %

Includes both elastic and plastic elongation

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21
Q

The material is more brittle at (lower/high) % of elongation?

A

Lower % = brittle

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22
Q

The material is more plastic/permanent elongated at (higher/lower) %?

A

Higher % = more plastic/permanent elongation (permanently bent WITHOUT danger of fracturing)

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23
Q

Define Elastic modulus

A

Measures the elasticity of a material i.e. represents the stiffness of a material within the elastic range

Determined by the slope of the elastic portion of the stress-strain curve

Elastic Modules = stress/strain

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24
Q

“A” is stiffer/rigid or flexible

“B” is stiffer/rigid or flexible

A

“A” is stiffer/rigid (metals/ceramics) because has a steeper slope

“B” is flexible (elastomers/polymers) because has a shallow/lower slope

25
Q

Define Ductility of a material

A

Enable it to be drawn (stretched) and shaped into wires by been of tension (think turning wool on a spindle)

26
Q

Define Malleability

A

Malleus = Hammer

Enables it to be hammered or rolled into thin sheets without fracturing (think sheet metal)

27
Q

(High/Lower) degree of elongation indicates good malleability and ductility

A

High degree of elongation indicates good malleability and ductility

28
Q

Metals tend to be (ductile/brittle)

A

Metals tend to be ductile

29
Q

Ceramics tend to be (ductile/brittle)

A

Ceramics tend to be brittle

30
Q

Define Resilience

A

Resistance of a material to permanent deformation

Measured by area under the elastic portion of the stress-strain curve (0-A)

31
Q

Define Toughness

A

Resistance of a material to fracture

Area under the elastic and plastic portions of the stress-strain curve (0-D)

Brittle material have low toughness because little plastic deformation occurs before failure

32
Q

Which graph(s) are stiff/rigid; which are flexible?

A

Stiffer: 1,2, 3, 4 (steeper slopes)

Flexible 5,6,7,8 (less steep slopes)

33
Q

Which graph represents the toughest material?

A

Graph 1 = has the greatest area under the curve

34
Q

Which graph(s) have the greatest resilience?

A

Graph 5,6 because have greatest area from (0-A)

35
Q

Which graphs have the highest strength?

A

Graphs 1, 2, 5, 6 have the highest proportional limit

36
Q

Which graphs have the highest ductility?

A

Graphs 1, 3, 5, 7 (longest to get to D)

37
Q

Which graphs have the highest stiffness AND strength?

A

1 and 2 (steepest with highest proportional limit)

38
Q

Which graph(s) have the greatest stiffness, strength, ductile?

A

Graph 1 (steepest, highest proportional limit, longest)

39
Q

Amalgam, cements, ceramics, plaster, stone are (weaker/stonger) in tension than in compression?

A

Amalgam, cements, ceramics, plaster, stone are weaker in tension than in compression

40
Q

Define viscoelasticity

A

Material that have the mechanical properties dependent on loading rate and exhibit both elastic and viscous behavior

41
Q

Define viscosity

A

Resistance of fluid to flow and equal to the shear stress divided by the shear strain rate

42
Q

Define Thixotropy

A

Describes the change in viscosity of a material with time

43
Q

Elastomeric impression material have (high/low) viscosity

A

Elastomeric impression material have high viscosity to stay in place without flow

44
Q

Define creep

A

Increase in strain in a material under constant stress

45
Q

(Greater or lower) creep makes a material more susceptible to strain accumulation and fracture

A

Greater creep makes a material more susceptible to strain accumulation and fracture

46
Q

Define Hardness

A

Resistance to permanent surface indentation or penetration

Resistance to plastic deformation

47
Q

Define Friction

A

Resistance between contacting bodies when on moves relative to another

48
Q

Define Wear

A

Loss of material resulting from removal and relocation of materials through contact of two or more materials

49
Q

What are the 4 types of wear?

A
  1. Adhesive wear
  2. Corrosive wear
  3. Surface fatigue wear
  4. Abrasive wear
50
Q

Define sol

A

Resembles a solution but made up of colloidal particles dispersed in a liquid (when chilled or reaction transforms into a gel)

51
Q

Define adsorption

A

ADsorption: liquid/gas adheres to the surface of the solid/liquid firmly by the attachment of molecules

52
Q

Define absorption

A

ABsorption: substance absorbed diffuses into the solid material by a diffusion process

53
Q

Do detergents (increase/decrease) surface tension of water?

A

Detergents decrease surface tension of water

Its hydrophilic part is in water and its hydrophobic end is in air/wax

54
Q

(Increasing/Decreasing) the surface tension (Increases/Decreases) wetting

A

Decreasing** the surface tension **Increases wetting

55
Q

Define Wetting power of liquid

A

Represented by its tendency to spread on the surface of the solid

56
Q

The greater the tendency to wet the surface, the (lower/higher) the contact angle

57
Q

Complete wetting occurs at what contact angle?

58
Q

What occurs of the contact angle of solder is too great?

A

There will be no penetration into the fine detail of structures to be joined

AVDC Flash Cards (3 decks)

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