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Pres/Res > Pres Res unit 1-materials > Flashcards

Pres Res unit 1-materials Flashcards

1
Q

Occlusal Force trend

A

decreases from molars to incisors

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2
Q

everyday chewing force

A

10N

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3
Q

movement of teeth during chewing

A

axial and horizontal

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4
Q

Force is defined by

A

point of application, magnitude, and direction of application

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5
Q

average max biting force

A

756N

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6
Q

Stress Strain Curves

A

A certain amt of force is required to move an object (rubberband) a distance deltaL; divide Force and deformation are devided by the cross-section of area and the length so that the force is independent of size since it changes

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7
Q

stress is equal to and units

A

force/area in Pascals (1MPa=1,000,000 Pa) Pa=N/m^2

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8
Q

shearing

A

forces on diff planes in opposite directions (i.e. force on top to left and force on bottom to right)

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9
Q

Torsion

A

twisting

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10
Q

Strain

A

no units, deformation/length; undergoes change in length

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11
Q

Elastic

A

deformation will not be permanent (rubber band)

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12
Q

Plastic

A

permanent deformation; relocation of atoms

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13
Q

universal testing machine

A

produces stress-strain curves

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14
Q

stress strain curve

A

will determine elasticity vs placitity

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15
Q

Elastic limit

A

looks at material, to determine the boundary between elastic and plastic

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16
Q

Proportional limit

A

use a machine to determine the boundary between elastic and plastic

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17
Q

Stress-strain curve

A

the stress value at which a material exhibits a specified permanent strain

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18
Q

ceramic materials

A

break before they permanently deform, such as ceramics

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19
Q

Ultimate tensile strength

A

the max stress a material can withstand before failure in tension

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20
Q

Fracture Strength

A

the stress at which a material fractures; not necessarily equal to ultimate strenght

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21
Q

Elastic Modulus/Young’s modulas

A

represents the stiffness within the elastic range E=theta/E=stress/strain

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22
Q

Stiffness of Cobalt chrome

A

good/stiff

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23
Q

Acrylic resin and composite resin stiffness

A

not very (relative)

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24
Q

Brittle materials in dentistry (not ductile)

A

Amalgam, composites, cements, and ceramics

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25
Q

Ductility

A

ability of a plastic to be deformed

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26
Q

Dutility trend

A

gold silver most

Lead tin least

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27
Q

Resilience

A

resistance to deformation., energy absorbed per V material

28
Q

Toughness

A

resistance of a material to fracture, or energy absorbed

29
Q

Stress strain comparisons

A

see charts
Brittle-straight line
Ductile- curved line

Taller line-strong
Shorter line-weak

Does not go far in x direction/high slope-stiff

Further in x-flexible (not much slope)
Tough- will bend a lot before breaking

Resielent- graph will not bend, stays elastic
Tough-graph will bend, becomes plastic but hard to fracture

30
Q

Ultimate compression strenght

A

amt of stress to compress a material

31
Q

impact strength

A

energy required to fracture a material under impact force

32
Q

diametral compression test

A

indirect tensile test, test brittle materials for tensile strength

33
Q

shear strength

A

max stress before failure in shear mode; used for bond strength testing

34
Q

Bending creates

A

areas of compression (of side angle getting smaller); neutral axis on object; larger angle is under tension (more likely to fail)

35
Q

cantilever Bending Test

A

tests bending, force applied down

36
Q

Bending moment

A

force x distance (basically torque)

37
Q

Flexural strength

A

denture materials and ortho wires, transverse strength, 3 point bend test

38
Q

Torsion

A

twistin, important in endo files for root canals, shear stretch

39
Q

Fatique

A

progressive fracture under repeating loading

40
Q

Stress to cycles to failure

A

shows endurance limit, may fail over long periods of small or larger stress

41
Q

Factors Affecting Fatique

A

environment: temp, humidity, pH
Surface features
Material history

42
Q

Fracture Toughness

A

A measure of material’s resistance to a brittle fracture when a crack is present; good for brittle materials (flaws in metal are more forgiving than ceramics)

43
Q

Viscoelasticity

A

has elastic and flow qualities; some elastic and plastic deformation is possible;

44
Q

Creep

A

Viscoelastc property-time dependent strain of a material under a static/constant stress

45
Q

Stress Relaxation

A

Viscoelastic- reduction in stress in a material subjected to constant strain- think ortho bands which apply less force after application

46
Q

Hardness

A

resistance to permanent surface indentation

47
Q

Brinell Hardness Test

A

used for metals; hardened steel ball indenter is used and diameter is measured

48
Q

Rockwell Hardness Test

A

Used for metals and plastics; a ball or cone used

49
Q

Vickers Hardness Test

A

microscopic, for metals and plastics-softer material loses out-porcelain hardest

50
Q

Knoop Hardness Test

A

micro indentation test , rhombic based pyramidal diamond

51
Q

Wear

A

loss of material; relocation

52
Q

Bruxism

A

pathological form of wear

53
Q

Abrasive two body wear

A

to surfaces rubbing, grinding

54
Q

abrasive three body

A

food between two teeth

55
Q

corrosive wear

A

wear coupled with a chemical attack

56
Q

Rheology

A

study of flow of matter

57
Q

Viscosity

A

fluids resistance to flow

58
Q

newtonian fluid

A

viscosity remains constant (water)

59
Q

Plastic

A

no flow until a certain shear stress is reached (yield point) toothpaste

60
Q

Psuedoplastic

A

decreasing viscosity as shear rate increases (stir faster and it gets thinner/easier)

61
Q

Dilatant

A

viscosity increases with a shear rate (harder to mix as you stir)

62
Q

Thixotropic

A

Time dependent decreasing in viscosity, has yield point, curve is not reversible (ketchup bottle)

63
Q

Burnishing

A

closing the metal margin of a metal crown-recovery of elastic strain but NOT plastic

64
Q

Barcol

A

additional hardness test-resin composites

65
Q

Shore

A

used for rubber

Pres/Res (14 decks)

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