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Dental material > Dental pt7 > Flashcards

Dental pt7 Flashcards

1
Q

Stress formula, unit

A

stress=F/cross sectional area (f/cm2)

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2
Q

Def stress

A

force apply to material NO depends only on force ALSO shape (cross section)
inversely prop cross sectional area ; proportional to load

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3
Q

Types stress

A

tensile
compressive
shear

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4
Q

Charac of all 3 stresses

A

all present at 1
func under same rule - if stress > strength material -> structure fail

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5
Q

What force when breakage occurs

A

tensile force

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6
Q

Strain def

A

temporary elongation when interxs tensile stress -> longer

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7
Q

Calc value strain

A

length increase/og length

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8
Q

Elasticity def

A

material have constant ratio stress-strain

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9
Q

Modulus elasticity def, entails

A

constant of constant ratio stress/strain
x2 stress -> x2 strain
diff material - diff charac - diff constant ratio -> modulus elasticity

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10
Q

Proportional limit/ elastic limit

A

greater stress when stress prop strain

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11
Q

Yield strength/ yield point

A

strength measure at stress w/ little strain

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12
Q

Ultimate tensile strength

A

(stretched to max) -> stress at breakage

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13
Q

Work hardening

A

metals stress > prop limit -> hardening
-> stronger
-> harder
-> > brittle

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14
Q

Elongation

A

total strain (elastic, plastic) at fracture

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15
Q

Charac modulus elasticity

A

inherent property
NO alter

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16
Q

Plasticity

A

elastic/ prop limit exceeds
-> plastic behavior

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17
Q

Types of plasticity material

A

Ductile - high plastic behavior/ permanent deform
Brittle - little/NO plastic behavior

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18
Q

Toughness

A

entire A under stress-strain curve
how much E required -> fracture material

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19
Q

Resilience

A

A under elastic reg
how much elastic E stored

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20
Q

Fatigue

A

cycles loading, unloading -> fracture even w/o ultimate tensile strength
ex: mastication

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21
Q

Newtonian fluid shows

A

constant viscosity
constant flow - INDEPENDENT strain rate

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22
Q

Formula newtonian fluid

A

n=o/e
viscosity= shear stress/ strain - flow rate

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23
Q

Types of fluids depends on flow when stress

A

Plastic (stress)
Pseudoplastic (shear)
Dilatant (pressure)

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24
Q

Plastic fluid

A

min stress -> flow

25
Q

Pseudoplastic fluid

A

increase shear -> increase flow

26
Q

Dilatant fluid

A

increase pressure -> increase rigidity

27
Q

Hardness

A

resistance material to indentation/penetration

28
Q

Tests hardness material - Birnell hardness no. BHN

A

hardened steel ball
measure dia -> test hardness

29
Q

Tests hardness material - Vickers hardness no. VHN/ diamond pyramid hardness test

A

pyramidal diamond
measure diagonals square indent -> avg 2 dimensions

30
Q

Formula VHN

A

1.85 x (F/d1xd2)

31
Q

Compare VHN - BHN

A

VHN=1.05 + BHN

32
Q

Thermal prop dentin

A

thermal insulator

33
Q

Thermal conductivity/ thermal diffusivity

A

rate heat flows thru material

34
Q

Thermal conductivity K measured by

A

speed heat (calorie) travels thru thickness (1cm) when 1 side maintain at constant temp + 1 celcius higher
(speed-thickness-heat)

35
Q

Thermal diffusivity

A

how fast int surface heats up when ext heated

36
Q

Formula thermal diffusivity

A

h= k/ (Cp +p)

h: thermal diffusivity of material (mm2/sec)
k: thermal conductivity
Cp: heat capacity
p: density

37
Q

Thermal expansion in dental

A

some restorative material have coeff very diff than tooth -> can cause damage
-> use porcelain, porcelain fused metal - same contraction rate on cooling from firing temp

38
Q

Electrochem series

A

list elements based on tendency gain/lose e-

39
Q

Reference standard electrochem series

A

potential of standard hydrogen electrode 0.000V

40
Q

Ex metal large pos electrode potential

A

Gold
Platinum

41
Q

Effect metal w/ large pos electrode potential

A

resistant OX, corrosion

42
Q

Formation electrolytic cell

A

large diff btw electrode potential 2 metals same solution -> form electrolytic cell -> discomf
ex: Au, Al

43
Q

Electric resistivity

A

resistance material to flow electric current

44
Q

Formula resistance

A

R=p(l/A)
R: resistance (Ohms)
p: resistivty
l: length
A: cross sectional area

45
Q

Ceramics def

A

any material have metallic comp + non metallic comp -> have crystalline/ amorphous structure

46
Q

Common material in dental is also ceramic

A

dental cement
porcelain
gypsum

47
Q

Sub groups ceramics

A

Crystalline cermics (Al2O3) - insulators ; high melting point ; britlle
Inorg salts
Glass - amorphous (CaO, Na2O, K2O)

48
Q

Metals def

A

pos ions w/ metallic bond (Strong bond)
crystalline structure (always solid crystal)
e- cloud -> conduct electricity, heat
soft ferromag prop

49
Q

Sub groups metals

A

Pure metals - same elements (solid/liquid - Hg)
Alloys - 1/more metallic comp - has new metallic prop
Intermetallic - all metals

50
Q

Effect Cu, Al in alloy

A

increase strength
> susceptible - corrosion

51
Q

Backbone polymer

A

C
Si

52
Q

Structure polymer

A

crystalline
amorphous

53
Q

Categories polymer

A

rigid polymer
waxes
elastomers

54
Q

Charac poly

A

soft
can become rigid
heat resistant

55
Q

Tg of rigid poly

A

Tg > room temp

56
Q

Tg elastomer

A

Tg < room temp

57
Q

Plasticizer use

A

uncross cross linked -> decrease Tg -> more elastic

58
Q

Charac plasticizer

A

less water needed (b/c water form hydrophilic mono)
poly shrinkage
free mono -> toxicity (b/c abdsorption plasticizer neg charges form in mono -> repel)

Dental material (7 decks)

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