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biomaterials > biomaterials > Flashcards

biomaterials Flashcards

1
Q

3 main classes of materials

A
  1. metals
  2. ceramic
  3. polymers
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2
Q

mechanical properties of metals

A
  1. hard
  2. ductile-tough
  3. strong
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3
Q

mechanical properties of ceramic

A
  1. hard
  2. brittle
  3. strong
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4
Q

mechanical properties of polymers

A
  1. soft
  2. ductile-tough
  3. weak
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5
Q

which have high processing temperatures

A

metals and ceramics

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6
Q

which tend to be used as direct processing materials

A

polymers

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7
Q

which tend to have low processing temperatures

A

polymers

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8
Q

metal bonding characteristics

A 
1,2,3 electrons in their outer shell
electrons are key
electrons are loosely bonded to nucleus
electrons have free mobility 
thermal and electrical conductivity 
ductility- bend without breaking
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9
Q

metal alloys

A

mixture of two or more metals
cast metal for crowns
amalgams

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10
Q

solid solution alloy is more what compared to pure metal

A

stronger, less ductile

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11
Q

microstructure of metals

A

polycrystalline grain structure

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12
Q

ceramic bonding characteristics

A 
ionic and covalent bonds
both are stronger than metallic bonds
covalent > ionic
ionic bonds- electron acceptor/donor
covalent bonds- equally share electrons
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13
Q

microstructure of ceramics (3 most common metallic oxides) (building block)

A 
mixture of metallic and non-metallic elements
1. SiO2
2. Al2O3
3. K20
SiO4 tetrahedron
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14
Q

crystalline structures of ceramics

A

long range order

crystalline silicate-quartz or crystobilate

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15
Q

noncrystalline structures of ceramics

A

short range order no long range or amorphous silicate-glass

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16
Q

most dental ceramics are ____ or _____

A

simicrystalline or polycrystalline

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17
Q

building block of dental porcelain

A

SiO4 tetrahedron- primarily a glass with some crystalline residuals

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18
Q

polymer bonding characteristics

A

covalent bonds
high molecular weight
long molecules composed of mainly nonmetallic elements
are entangled long chains
“cooked spaghetti”- entanglement gives strength

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19
Q

polymer formation

A

liquid (monomers)- solid (polymers) Polymerazation

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20
Q

resin matrix of polymerization

A

monomers

iniator

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21
Q

polymerization step 1

A

Activation- free radical initiation

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22
Q

polymerization step 2

A

initiation- free radical combination with monomer unit, double bond opening

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23
Q

polymerization step 3

A

propagation- chain growth, volume decreases, shrinkage

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24
Q

polymerization step 4

A

termination

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25
Q

monomer functional groups

A

linear chain

crosslinked (branched)

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26
Q

linear chains

A

monomethacrylates

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27
Q

crosslinked chains

A

dimethacrylates

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28
Q

polymerization initiated by what 3 things

A

light
heat
chemical mixing

29
Q

why is polymerization important

A 
direct placement
flowable material
trigger for setting
repaid setting
room temp setting run
30
Q

direct placement vs indirect placement

A

direct- one visit, less preparation, don’t last as long

indirect- multiple visit, last very long, expense

31
Q

which are indirect placement

A

metals and ceramics (exceptions metals- amalgam, ceramics- cements

32
Q

which is direct placement

A

polymers

33
Q

use of polymers in dentistry

A

provisionals- temp crowns (linear)
adhesives- crosslinked
registered materials- impression materials

34
Q

composites

A

physical mixture of metals, ceramics, polymers

want to get some intermediate of all the properties

35
Q

composite rule of mixture

A

By knowing the phases present in the structure of any material and interfacial interactions, it is possible to predict the overall properties fairly well

36
Q

composite dispersed phase

A

glass fillers

37
Q

composite matrix phase

A

monomer resin

38
Q

fillers

A

are chemically bonded to resin phase to improve properties (silane coupling agents)

39
Q

2 types of fillers

A

silicate glass

colloidal silica

40
Q

how do fillers affect properties

A

increase strength, modulus, viscosity and decreases shrinkage

41
Q

increasing filler size increases ______

A

surface roughness

42
Q

most dense to least dense materials

A

metallic, ceramic, polymer

43
Q

density =

A

weight/unit volume

44
Q

thermal expansion

A

most things expand when they heat up and contract when cooled.

45
Q

thermal expansion coefficient

A

The degree of expansion divided by the change in temperature

46
Q

heat flow

A

thermal conductivity. teeth are insulators due to high mineral content

47
Q

thermal conductivity

A

rate of heat conduction

48
Q

metals have _____ heat conductivity so they need what

A

high, need thermal insulator like base

49
Q

composites have ______ heat conductivity and do not need a what

A

low, base

50
Q

how is color defined?

A

3D coordinate system

51
Q

what are the 3 dimensions

A

Hue
value
chroma

52
Q

what is hue

A

wavelength

color

53
Q

what is value

A

intensity

brightness

54
Q

what is chroma

A

purity

density or concentration

55
Q

what is metamerism

A

when two objects appear the same color under one light source but different color under another light source

56
Q

mercury to alloy ratio

A

.5 depends on commercial product, modern products 42-45% Hg by weight

57
Q

factors for setting process

A

composition, size and shape of alloy particles

58
Q

two types of alloy particle shape

A

spherical

lathe-cut particles

59
Q

which particle resist forces of condensation more

A

lathe-cut particles- wetted with higher mercury:allow ratio

60
Q

how many sizes are typically observed in spherical particles

A

3

61
Q

how many particles are observed in lathe-cut particles

A

wide range usually, intentionally done by manufacturer for optimum condensation

62
Q

what are bricks

A

alloy particles in set material

63
Q

when is Hg found?

A

reaction phase, no free mercury after setting reaction.

64
Q

what is n’

A

Cu6Sn5 product of set reaction.

65
Q

advantages of dental amalgam

A

inexpensive
easily prepared direct restorative material
margin sealing capability.

66
Q

disadvantages of dental amalgam

A

poor esthetics compared to resin composites
weakening of tooth from removal of tooth structure
recurrent caries
brittle nature of material
wastewater pollution with Hg
sensitivity of properties to manipulation

67
Q

general setting reaction for amalgam is…

A

alloy + Hg —> dental amalgam

68
Q

majoy elements in alloy are

A

silver, tin, 2-30% copper and 0-1% zinc

69
Q

which should be selected more high or low copper

A

high copper- greater clinical longevity of restoration s and much lower creep values

biomaterials (4 decks)

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