Dental Biomaterials

Front 1

density formula

Back 1

d=mass/voume

Front 2

gold alloys have how much more density than non-noble alloys

Back 2

twice as much

Front 3

reflection

Back 3

the amount of light that bounces off the surface of the material

Front 4

refraction

Back 4

the degree to which the light is bent when passing form one medium to another

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absorbance

Back 5

fraction of light absorbed by at a specified wavelength

Front 6

transmittance

Back 6

fraction of incident light at aa specified wavelength that passes through the material

Front 7

translucence

Back 7

peoperty of allowing light to pass through diffusely via an indirect path , scatters in multiple directions as passes thorough due to refraction within the object, causes a blurrier image

Front 8

opacity

Back 8

the property of blocking the passage of light

Front 9

enamel is made of________ crystals in a protein matrix and has a refractive index of _______ and is ______

Back 9

hydroxyapatote crystals, 1.65, translucent

Front 10

thermal conductivity

Back 10

the ability of a material to conduct heat


K= (cal/sec/cm2) / (deg C/cm)

Front 11

thermal diffusivity

Back 11

responses to transient temp changes (when hot food is ingested)
the temp is not constant, but changes depending on how well the heat is conducted and how much heat is absorbed in raising the temperature.

delta=K/pxCp

Front 12

Cp is

Back 12

specific heat
the number of calories required to rais the temp of one degree

Front 13

low specific heat and high thermal conductivity lead to

Back 13

high diffucsivites temperatures

Front 14

gold has 1/10 the specific heat of dentin and 500 times the thermal conductivity so......

Back 14

a pure gold filling would thus protect the tooth pulp very poorly from the termakl transient compared to natural dentin

Front 15

thermal expansion

Back 15

when materiasl undergo a temperatue increase, the vibrational motion of atoms and mean interatomi ( bond) increases

the result is an increase in volume

alpha= (delt L)/ (Lx delta T)......L= length and T= temp

Front 16

electrical resistivity

Back 16

p= (RxA)/l

restoration should have high resistivity to protect the pulp

Front 17

electromotive series

Back 17

the ease which a metal oxidizes in solution( gives up electrons)

Front 18

surface properties include

Back 18

surface energy, wetting, adhesion,

Front 19

surface energy is

Back 19

solids and liquids must have unsatisfied bonds on thier surface which increae energy dnesity , surface tension for liquid and surface free energy for solids
all systems try and achieve min energy state

Front 20

metals have _____ surface energies while hydrocarbon polymers have _________ surface energies

Back 20

high, low

Front 21

wetting is

Back 21

one way for a system to achieve a decrese in energy for a low surface tenison liquid to wet and spread ona g=high surface energy solid

Front 22

wetting occurs best when

Back 22

the solid has a high surface free energy
and the liquid has a low surface tension

Front 23

the contact area

Back 23

decreases with improved wetting

Front 24

wetting is measured by

Back 24

the angle formed between a drop of liquid and a sold surface

Front 25

some areas where wetting is crittical include

Back 25

wetting of wax patterens by casting investments,
wetting of teeth by impressions,
wetting of impression by gypsum products,
retention of dentures,
penetration of etched enamel and dentin by bonding resins and soldering

Front 26

adhesion depends directly on

Back 26

wetting

Front 27

adhesion based on wetting alone relies on

Back 27

secondary bonds ( van der wals forces)

Front 28

wetting is also iportant in adhesion involving

Back 28

micromechanical interlocking

Front 29

definition of polymer

Back 29

poly= many mer= unit or
10 or less is an oligomer

Front 30

monomer is

Back 30

a chemical compound capable of reacting to form a polymer . genrally become the repaeating units

Front 31

polymerization

Back 31

a chmeical reaction in which monomers are converted to polymers

Front 32

linear polymer

Back 32

example is polyethylese
forma linear chain

Front 33

branched polymer

Back 33

branching of a polymer chain
entanglemnt increases

Front 34

crosslinked polymer

Back 34

permanent connections between chains

Front 35

crosslinking happens when

Back 35

1- there is a crosslinker during the polymerization which formed the bonds
2- the monomer had more than 2 reactive sitesallowing the formation of branhes which were able to connect the neighboring chains

Front 36

copolymer

Back 36

formed by more than one type of monomer

Front 37

usually the order of the copolymer is

Back 37

random copolymer

Front 38

blocked copolymer

Back 38

is when a large group of one monmer tpye is connected together in a copolymer

Front 39

the longer the polymer chain the greater

Back 39

the number of enlargments (temporary connections) between the chain
the harder it is to distort the polymeric material
rigidity, strength, and melting temp increase

Front 40

tacticity

Back 40

the relative position of the side group of the polymer form one unit to the next

Front 41

the diffferent arranmgment of tacticity

Back 41

1-isotactic
2-syndiotactic
3-atactic

Front 42

isotactic

Back 42

when the relative position of the side group or brnaches of the polymer is always the same

Front 43

syndiotactic

Back 43

when the sequence relative position of the side groups or branches or branches is alternating

Front 44

atactic

Back 44

when the substitutes are randomly arranged

Front 45

due to the repeating structures of isotacic and syndiotactic polymers

Back 45

they can readily be formed into regular arrays and can readily crystalize

Front 46

atactic polymer like methyl mathacrylate are

Back 46

amorphous and so less brittle than crystaline

Front 47

another property of polymers that can affect material and mechanical characteristics is

Back 47

molecular organization

Front 48

polymer chemistry, chain length, brnching, crosslinking, and molecular orientation can be grouped into three categories

Back 48

1- mechanical properties
2-dissolution properties
3- thermal properties

Front 49

mechanical properties

Back 49

elastic- easily deformed but rapidly returns to original shape
plastic- redily deformed and molded into a new permanet shape...permanent deformation
viscoelastic- plastic flow and elastic recovery

Front 50

dissolution properties

Back 50

polymers absorb a solvent, swell and soften rather than dissolve , but as chain length decreases will dissolve
crosslinking inhibts complete chain seperation and disolution
amorphous polymers swell more
elastomers swell more than plastics

Front 51

plasticizing

Back 51

absorbed molecules push chain apart and facilitate inter chain slippage

Front 52

thermal properties

Back 52

thermoplastics- materials that soften when heated and can be molded . process is reversible since no new chemical bonds are formed.
thermosets- polymerization make new bonds that lock the material into a new shape, nonreversible , becuase applying heat speeds the solidifying reaction once solidified the material wont melt.

Front 53

glass transition temperature (Tg)

Back 53

a marked change from being glassy and brittle to being ductile or rubbery
** this is not due to polymer melting **
when a solid polymer is cold enough it is stiff hard and brittle and called glassy

Front 54

curing

Back 54

chemical reaction in which low molecular weight materials are converted into higher molecular weiht materials in order to obtain desired properties

Front 55

setting

Back 55

the extent to which curing has progressed
initial set- the material has undergone sufficient polymerization to hold its shape temporarily
final set- reaction is complete

Front 56

monomers may be joined together via different types of chamical reaction like

Back 56

addisiotn polymerization and condensation polymerization

Front 57

addition polymerization

Back 57

monomers add sequentially one to another in a chain growth reaction. polymers produced is a simple multiple of the monomer

Front 58

steps in addition polymerization

Back 58

1- activation
2-initiation
3-propagation
4-termination
-accelerator
- inhibitor

Front 59

condensation polymerization

Back 59

"growth polymerization"
all monomers react simulatinuously
catalyst is used to activate the monomer
small monomers are eliminated fromt he polymer chain
unit parts of the polymer have slightly different chemical formula than original monomer

Front 60

condensed byproducts degrade properties

evapoartion leads to ...............
retention leads to ____________

Back 60

porosity and shrinkage

plasticity (softening)

Front 61

ceramic

Back 61

materials made form highly reacted ( in the highest oxidized state) or otherwise inert chemical compounds - usually metal oxides

Front 62

dominante characteristics of cermaic material

Back 62

extremly stable, high melting temps, hard and brittle, low thermal expansionand contraction, electical insulator , colorless, insoluble , inert-do not corrode or react, highly oxidized ,bioogicaly compatable

Front 63

glass

Back 63

an amorphous single pahse ceramis
short range order
melting range (not point)
transparent
plastic like material with very high degree of thermal stability

Front 64

porcelain

Back 64

multiphase ceramic with crydtaline pahses dispersed in a glass
glass plase binds crystaline phases together
translucent or opaque
fabirication by thermal fusion of ceramic "frit" particles ( ground up glass_

Front 65

compostiiton of porcelain

Back 65

silicates
metal ions can replace si and alter properties

Front 66

ingrediaent used to form dentsal porclein

Back 66

1- quartz( strength and high melting pt)
2- feldspar(decrese fusing temp,softer glassy phase, increase solubility) -85% procelin
3-kaolin (a clay, increase viscosity to prevent slump)
4-pigmements (metal oxides, provide color shade for shade matching )

Front 67

building up and firing process for making crowns

Back 67

1- agglomerate
2-shape and condense
3-remove all water
4-fire
5-build up and refire
6- characterization
7- glazing

Front 68

progressive fusion to attain

Back 68

max density
min porosity
max transluceny

Front 69

light scattering for rough surface

Back 69

dull appearance

Front 70

light scattering when porosity

Back 70

inclusions and crystaline reagions produce translucency or opacity

Front 71

opacity

Back 71

zero light transmission
large amounts of scattering cause this
translucency

Front 72

color

Back 72

blue or violet can be scattered more than yellow or red

Front 73

absorption

Back 73

removal of a portion of light pasing through a material by electron interaction
pricipla cause of color
portion not absorbed is seen as the color that is reflected

Front 74

color space has 3 demensions

Back 74

hue
value
chroma

Front 75

hue

Back 75

cominant wavelenght

Front 76

value

Back 76

grey scale
white = high value balck = low value
the lumicity

Front 77

chroma

Back 77

color saturation or intensity
pastels have low chroma

Front 78

brittlness

Back 78

a material that is strong in compression but weak in tension and shear

Front 79

brittle failie is due to

Back 79

lack of ductility
( the inability to of dislocation to migrate to nw stable locations
cracks propagate from this

Front 80

crack initiation

Back 80

surface imerpfections act to concentrate stress
cracks are initiated when a shear or tenison is aplied
when brittle material is compressed cracks are closed

Front 81

brittle materials are strong in ________ but weak in ______

Back 81

compression, tension

Front 82

scratches and porosity are prime sources of ______ also knwon as ______

Back 82

surface imperfections , griffin flaws

Front 83

lisas cards have the rest of the porcilin

Back 83

....

Front 84

reflection

Back 84

the amount of light that bounces off the surface or a meterial

Front 85

refraction

Back 85

the degree to which light is bent when passing from one medium into another

Front 86

refractiion index

Back 86

ration of speed of light in a vaccum to that in a given material q

Front 87

combos of reflaciton and refraction gives rise to effects such as

Back 87

scattering , opactiy, transclucency and transparancy

Front 88

scattering

Back 88

when light refelcts off a rough surface, diffuse reflectance occurs ie the light is reflected in multiple directions and dull frosted appearance ir observed

Front 89

transclucent materials in dentistry are

Back 89

porcelin , composite resins, and dental particles

Front 90

transparency

Back 90

transmission of liht via direct path through a material , can see through clearly

Front 91

priamary colors

Back 91

additive and subtractive nature of light

Front 92

red blue green are primary colors ....

Back 92

often used in dentistry

Front 93

complex grey

Back 93

when complementary transparent colorants are overlapped they produce a neutral gray withought any loss of transparancy

Front 94

incandescent lamp

Back 94

tungsten light bulbs

Front 95

flourescnt light

Back 95

uv present

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natural light

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sun

Front 97

metamerism

Back 97

is an effect in whicg objects match when viewed with one source of light but not with another

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flourescence light

Back 98

emmitted at longer wavelength causing a color glow

Front 99

opalescence

Back 99

phnomenon in which material apears to be one color when light is reflected form it and another when light is transmitted through it

Front 100

spechtrometer

Back 100

an intrusment for optical measument of intesity relative vs wavelength

Front 101

L*A*B system

Back 101

l= lightness or value
a= red green
b= blue yellow
standard buy which color is measured

E > 3.3 can be detected clinically and precived as not matching

Front 102

munsell system

Back 102

system of visual comparison
mathces first the value then the chroma then the hue

Front 103

shade guides

Back 103

divid tooth color into four basic shade ranges

1-reddish brown
2- reddish yellow
3-gray
4-reddish gray

Front 104

different shade , the littler took with be precieved as

Back 104

larger

Front 105

glossier texture of a tooth , the tooth will be preciveed as

Back 105

larger

Front 106

force

Back 106

is the action which produces or tends to produce motion in a body or changes motion in a moving body
force has both magnitude and direction

Front 107

stress

Back 107

the response of the body has to the force,

stress= (force/area)

Front 108

stress components

Back 108

tensile
compressive
shear

Front 109

tensile stress

Back 109

result when a body subjected to two forces acting along the same line but directed away form eachother

Front 110

compression stresses

Back 110

result when a body is subjected to two forces acting along the same ling but directed towards one another

Front 111

shear stresses

Back 111

resulting when a body acted upon by two forces not acting along the same line

Front 112

strain

Back 112

the application of a stress to a body tends to produce a deformation

strain = cahnge in lenght / original length

Front 113

elastic deformation

Back 113

is the removal of the force causes the body to return to its original dimensions

Front 114

plastic deformations

Back 114

if upon removal of force the body does not return to its normal deminsions

Front 115

modulus of elasticity

Back 115

the slope of the linear protion of the curve in a stress strain diagram

Front 116

proportional limit (P)

Back 116

within the liner regino the stress is directly proportional to strain, stress beyond this limit deviates

Front 117

elastic limit (E)

Back 117

within the linear region the deofrmation is elastic and recoverable

Front 118

yield strength (Y)

Back 118

point where the material exhibits a specialized deivation from proportionality, line that goes parallel to linear line and intersects a point is where this point is

Front 119

ultimate strength (U)

Back 119

the greatest stress reached anywhere on the stress strain digragm

Front 120

breaking strength(B)

Back 120

stress at the point to fracture

Front 121

longation

Back 121

the deformtion resulting from the application of tenisil strength . determined by subtracting the strain at the elastic limit form the stress in quesiton

Front 122

resilience

Back 122

meausre of the energy per unti volume absorbed bya material in undergoing elastic deformation ,

the area under the stress strain curves up to the elastic limit

Front 123

toughness

Back 123

energy per unit volume absorbed by the material up to the point of fracture , the area under the entire stress strain curve including elastic and plastic regions

Front 124

diameter tensile test

Back 124

tensile strength of a material frequently calc from data generated by testing a cyllindrical sample in compression along a diameter , while load in compressive , internal stress are tensil and and can be calculated
s=(2P)/(piDT)

Front 125

transverse strength

Back 125

samples are fabricated at recatangle means and tested by applying the laod to the center whil supposrting the beam at both ends , the resulting breaking strength is calulated as the transverse strength

2=(3Pl)/(2bd)

Front 126

with stress strain behavior rate and time at while a load is placed do

Back 126

not affect the results , but for few it does apply

Front 127

impact tests

Back 127

materials which exibit plastic deformation at low rates of load behave more brittle as the rate increases

this test used to test impact resistance using a weight pendulum

Front 128

creep or flow

Back 128

some materials at the end of a load rate scale exhibit elastic behavior in conventional tests but behave more plasticly when loaded slowly

viscoelasticity indicated viscous( plastic behavior at low strain rates and elastic behavior at high strain rate

Front 129

fatigues

Back 129

any material stressed repeatedly below the elastic limit which can lead to fracture

Front 130

hardness

Back 130

measure of resistance of a material to permanant indentaions or penetration

Front 131

brinnel hardness tets

Back 131

test involves forcing a stell ball into the surface of the specimaen under a fixed load

BHN= (2L)/ (D[D-(D2-d2)]^1/2

Front 132

vickers hardness

Back 132

diamond pyramid testing, the indenter is a square based pyramid with 136 deg included angle between the opposite sides

VNH= (2Lsin 136/2)/(d2)

Front 133

knoop hardness

Back 133

measured with a pyramidal indenter but pyramid is assmetrical having a ratio of long to short diagonal of about 7/1

KHN=(L)/ .07028 d2)

Front 134

rockwall hardness

Back 134

the depth of penetration is measured rather than the area of penetration , different penetrations are used and a preloader may or may not be used. each combo of indentor size and shale preload and final load defines a unique rockwall scale.
rockawlall hardenss 87 means nothing Rockwall C hardness = 87 does

Front 135

solution hardening

Back 135

introducing A aomt into B lattic creates strain int the lattice which takes more energy to move a disslocation thoruhg this strained region and the alloy is harder (stronger ) than either elemnts involed

Front 136

work hardening

Back 136

genertaing more dislocationf by working the alloy tends to strengthen it

Front 137

dispersion hardening

Back 137

dislocation is pinned byt the particle and the allo strengthneed

Front 138

precipitation (age) hardening

Back 138

the precipitated phase acts like a dispered phase introduced form an external source which strengthens it