BioMaterials Flashcards
(147 cards)
0
Q
A material used to construct artificial organs, rehabilitation devices, or prostheses and replace natural body tissues, without causing any hard or negative reactions
A
Biomaterials
1
Q
What are the three main classes of materials
A
Metals
Polymers
Ceramics
2
Q
Mechanical properties of metal (3)
A
Hard
Ductile/tough
Strong
3
Q
Bonding of metals: metallic elements have \_\_-\_\_ electrons in outer shell Electrons are key to \_\_\_\_\_\_\_\_\_\_\_ Electrons are \_\_\_\_\_\_\_\_ bound to nucleus Electrons have \_\_\_\_\_ mobility
A
1-3
key to metallic bonds
loosely
free mobility
4
Q
What is the microstructure of pure metals (4)
A
Molten metal –> nuclei of crystallization –> crystal growth —> formation of crystal grains
5
Q
Polycrystalline structures = pure _____
A
Metals
6
Q
Thermal properties of metals
A
High processing temperature (except amalgam)
7
Q
Metal alloys are processed for __________ and __________
Alloys are ______ and _____ ductile than pure metals
A
Cast metals for crowns and amalagms
Stronger and less ductile
8
Q
Mechanical properties of ceramics (3)
A
Hard
Brittle
Strong
9
Q
Bonding of ceramics via _____ and _______ bonds
Both are stronger than _______ bonds
A
Covalent and ionic
Metallic
10
Q
Electron donor and acceptor
Weaker
A
Ionic bonds
11
Q
Equally share electrons; non mobile ions
A
Covalent bonds
12
Q
Thermal properties of ceramics
A
High processing temperature except cements
13
Q
How ceramics are processed
A
Indirect placement
14
Q
Microstructure of ceramics:
Mixture of _______ and ___________ elements
Most common ceramics in dentistry are 3 metal oxides….
_____ is a tetrahedron
A
Metallic and non-metallic
Most common ceramics: SiO2, Al2O3, K2O
SiO2 is the tetrahedron
15
Q
Microstructure of ceramics:
Crystalline (long range order), crystalline silicate-_____, or _________; and ________
Crystalline (short range order) or amorphous silicate (______)
Most dental ceramics are ___________ or ______________
A
Silicate-quartz, crystobilite; and leucite
Glass
Semicrystalline or polycrystalline
16
Q
Mechanical properties of polymers (3)
A
Soft
Ductile/tough
Weak
17
Q
Bonding of polymers:
_________ bonds
High _______ weight
Long molecules composed of _________ elements and ________ elements (COHN)
Polymers are entangled in ______ chains
Derive strength and properties from ___________
A
Covalent Molecular Nonmetallic and organic Long Entanglement
18
Q
Thermal properties of polymers
A
Lower processing temp except indirect composites
19
Q
Processing of polymers:
Used as _______ processing materials
_________ placement
Polymerization; ___________ —-> _____________
A
Direct
Direct
Monomers –> polymers
20
Q
Steps of polymerization (4)
A
- Activation - production of free radicals
- Initiation - free radical combination with a monomer unit to create the beginning of a growing chain; double bond opening
- Propagation - continued addition of monomer units
- Termination - cancellation of growing chain end by any one several possible events
21
Q
What factors contribute to each materials mechanical properties (4)
A
atomic rearrangements (crystalline vs non-crystalline)
bonding
composition
defects
22
Q
polymerization can be initiated by theses three things
A
light
heat
chemical mixing
23
Q
ability to slide chains by each other
A
linear polymer (monomethacrylates)
24
covalent bonds; stronger and more brittle
limits movement
will not dissolve
cross-linked polymer (dimethacrylate)
25
physical mixture of metals, ceramics, and/or polymers
composite
26
by knowing the phase present in the structure of any material and interfacial interactions, it is possible to predict the overall properties fairly well
Rule of Mixtures
27
chemically bonded to resin phase (matrix) to improve properties
fillers
28
relative rate of change during temperature changes
coefficient of thermal expansion
29
Materials (teeth, amalgam, composite, etc) have ___________ coefficients of thermal expansion, inducing ________ which is the ingress or egress of fluid at the marginal level
different
| perlocation - fluid can leak into margin from separated amalgam
30
Teeth are ______ due to high mineral content
| dental pulps can withstand small temperature changes over _____ times
insulators
| short
31
metals have a _____ thermal conductivity so they need a _____-like base before placement
high
| insulator
32
composites have a _____ thermal conductivity and do not need a base
low
33
defined on a 3D coordinate system
Color;
| value (intensity), hue (wavelength), and chroma (purity)
34
material may have a different color under a different light source
metamerism
35
Disposal of Amalgam;
use _____-use capsules
use a ____-touch system when cleaning spills
discard old or damaged capsules that are prone to leaking
store amalgam in a _____ space with finely divided _____
avoid ________ heating
single
no
cool; sulfur
baseboard
36
Patient Issues with Amalgam;
some patients may exhibit ________ _____ _______
many _________ are used
allergic skin reaction
| alternatives
37
Operator Issues with Amalgam;
routes of mercury exposure: ____ contact, _____ of vapor, and ______ droplets
threshold limit value; ____ mgHg/m3
skin contact, inhalation of vapor, airborne droplets
| 0.05 mgHg/m3
38
dental amalgams are any alloy made of Hg with a _____-____ alloy with varying amounts of ____ and small amounts of zinc
silver-tin
copper
zinc
39
Benefits of high copper amalgam (4)
greater clinical longevity
lower creep values
corrosion resistance
contains >12%
40
Zinc-containing vs zinc free (3)
zinc facilitates lathe-cut particles
improves corrosive resistance
no concern with Zn-free alloys about moisture contamination
41
Mercury to Alloy ratio
0.05, but depends of manufacturer
42
Silver --> Hg
| major reaction phase in both high and low copper amalgam
Gamma 1 (product)
43
Tin ---> Hg
| only seen in low copper amalgam
Gamma 2 (product)
44
gamma is the _____ material + Hg --> reaction phases (____) + _______ alloy particles (core)
starting alloy particles
matrix
unreacted
45
first step in setting process of amalgam
both gamma 1 and gamma 2
46
second step in setting process of amalgam
disappearance of gamma 2, and formation of n' phase
| slower setting reaction than for HCSS products because of this second step
47
general characteristics of amalgam (4)
brittle under normal rates of loading (higher compressive (350) to tensile (70) strength)
poor edge strength
insufficient strength of set amalgam would increase amount of marginal breakdown
no free Hg in final set
48
the deformation that occurs as a result of constant force (load) on something; the force won't cause an immediate break, but will create deformation over time: low copper has the highest level
creep
| blocked by high n' value in high Cu values
49
clinical advantages of amalgam (4)
margin sealing capability (decreases micro-leakage over time)
corrosion products
easily prepared direct restorative material
relatively inexpensive compared with gold alloy
50
Alloy particles have complex structure with three phases
γ(Ag3Sn) β(Ag-Sn) ε(Cu3Sn)
51
lathe cut
creates a wide range of sizes
| from cast ingot
52
corrosion at inter proximal contact with gold alloys
galvanic corrosion
53
corrosion due to multiple phases
anode (corroding metal) and cathode (different metal) [2 different phases in amalgam]
ionic movement
electrochemical corrosion
54
corrosion at margins
crevice corrosion
55
corrosion from reaction with sulfide ions at occlusal surface
lower pH and oxygen concentration, and retained under plaque due to lower oxygen levels
chemical corrosion
56
measure of surface properties via contact angle used to measure how liquid interacts with solid
good wetting = _________
poor wetting = _________
good wetting = low contact angle (approach 0)
| poor wetting = high contact angle (approach 180)
57
wetting can be anticipated on the basis of _______ and ________ of materials
hydrophobicity and hydrophilicity
58
allow penetration into areas with water
usually mixed with solvent (alcohol/acetone)
very low viscosity
allows for attachment to composite
hydrophilic fibers
59
angle where a liquid interference meets a solid surface
contact angle
60
ability of a liquid to maintain contact with surface
wet-ability
61
molecules can have _____ hydrophobic and hydrophilic properties
both
62
spontaneous destructive oxidation of metals (all metals do this)
corrosion
63
immune to corrosion
noble metals, like gold
64
produces a corrosive film that prevents further corrosion
| titanium implants
Passive corrosion
65
normally occurs through dissolution of oxides created by H-bonding; effects of water in local areas of high acidity
chemical dissolution (corrosion/hydrolysis) of ceramics
66
absorption of water into the _______ (secondary bonds), causes a _________ change
hydrolytic degradation and release of components (primary bonds)
-water, enzymes, bacterial byproducts
polymers
| dimensional
67
degradation products are related to
toxicity
68
Stress-Strain Curve
x axis = _____
y axis = _____
linear portion = _____
strain
stress
modulus
69
represents the amount of strain (deformation) process in response to each amount of stress (load)
overall stiffness of a material
higher slope = can under go ____ stress
modulus (linear portion of stress-strain curve)
more stress
can handle more stress per strain
70
point on modulus from which the line starts to curve, and begin to irreversibly deform
elastic limit
71
area under curve to point of elastic strain (reversible deformation)
resilience
72
area under curve to point of fracture due to plastic strain (irreversible deformation)
toughness
73
_____ a material will cause the material to become soft and the mechanical property value decreases
stress-strain curve will shift to the _____ and ______
heating
| right and downward
74
multiple cycles of low stress
fatigue
75
measures a materials resistance to crack propagation
has high clinical correlation to clinical wear data
the amount of resistance to breakage when a crack in a sample is pulled apart
fracture toughness
76
create small cracks at one area, which eventually causes breakage at that point
cyclic stress
77
study of stress and strains
| effects of forces on the motion of biomaterials and biologic structures
biomechanics
78
teeth are not completely ______, can lead to abfraction
rigid
79
________-______ stability due to enamel on sound dentin
| when a tooth is unrestored, it is very strong
buccal-lingual
80
when the enamel wall is no longer ______, its resistance to fracture is much lower
AKA ________ weaken teeth
continuous
| preparations
81
esthetic direct restorative
cured by visible light
primary benefit is the combination of esthetics and ease of placement
hydrophobic - promotes bonding
moderate clinical outcomes
is a hybrid material of organic and inorganic phases ( ____ and ____)
composites
| resin and filler
82
components of a composite resin (4)
organic resin phase
inorganic filler phase
bonding agent
visible light initiator
83
helps with the processing and handling of composites
BISGMA provides physical properties
viscosity high and cannot be used alone
resin
84
helps modulus and wear resistance
filler
85
trade offs of composite resins;
wear resistance and strength but ____ and has ___ processing
poor wear resistance but ___ with ____ processing
brittle, poor
| tough, good
86
joining of polymers with covalent linkages
cross linking
87
additional _____ lead to a stiffer and stronger material
longer working time
curing develops mechanical properties
increases modulus
also depends on the materials you started with (stiff becomes stiffer)
cross-links
88
different ____ sizes exist and control properties
silica or zinc inorganics
50-80% weight of composite
has surface -OH groups
filler
89
```
higher filler loading results in a
______ modulus,
______ strength
______ viscosity
______ in shrinkage
```
increase
increase
increase
decrease
90
why fillers are small (5)
different sizes (micro, nano, micron, etc)
teeth are nano composites
smaller fillers have better wear properties
allows for better polishing and finish
expectation of better mechanical properties
91
binds inorganic filler so filler can bind to organic resin
uses the OH group on filler
forms chemical bridge
coupling agent
92
results from a density change of monomer to polymer
polymerization shrinkage
93
properties of polymerization shrinkage (4)
inherent property of double bond polymerization
measures by density change
important for direct composite restoratives
important for any material that requires dimensional stability
94
clinical consequences of shrinkage (2)
causes stress on tooth structure
| can cause micro leaks and lead to secondary caries
95
2 components of glass-ionomer cements
acidic polymer and aqueous (water) solution (polyacid)
basic glass (aluminaflurosilicate)
+ a modifier
96
properties of glass ionomers (4)
cured by acid base reaction
releases fluoride
good adhesion to tooth structure
salt bridges created slide, Al3+ can bind to 3 groups
97
curing reaction of glass ionomers (5)
- polyacid reacts with basic glass, glass releases Ca2+, Al3+, F-
- divalent Ca2+ ions quickly chelate with acid polymer chains
- not all the glass is consumed in reaction
- salt bridges (COO-) form from the polyacid and glass (Ca and Al)
- Al3+ replaces Ca2+, increasing strength and releasing F-
98
how GI reaction differs from composite
no coupling agent needed
F- released
mechanisms not clearly understood
water based restorative
99
important for forming a mechanical bond as opposed to a chemical bond
microtags
100
```
based upon composite resin chemistry
contains acids groups to promote bonding
dimethacrylates that are visible light cured
unfilled or lightly filled
bind to enamel
hydrophilic
```
adhesives
101
differences between adhesives and composites (2)
lower level of filler to decrease viscosity in adhesives
| additives in adhesives that help in bonding
102
both hydrophobic and hydrophilic properties are needed because composites are _______ and enamel/dentin is _________
hydrophobic
| hydrophilic
103
designed to flow into pits
prevents further decay
etching recommended to prepare enamel
sealants
104
differences between sealants and composites (3)
there is no filler, but otherwise the same chemistry
low viscosity, allows for easy pit flowing
prevents further decay
105
oxygen interferes with radical polymerization (inhibiting the polymerization of methacrylates)
at surface of composites or sealants, unpolymerized material must be removed
surface of VLC materials are often uncured
oxygen inhibition layer
106
used to make a negative mold of dental structures
| transfer to gypsum model (plaster/stone)
impression materials
107
```
used for making an impression
water based
resembles a solution, but made up of colloidal particles dispersed in a liquid
calcium cross-linked
temperature controlled (reversible)
chemically controlled (irreversible)
```
irreversible hydrocolloid (alginate)
108
hydrophobic, synthetic impression materials
| polysulfides, siloxane, polyethers
viscoelastic
109
ideal properties of impression materials (6)
```
low cost
long shelf life
biocompatible
pleasant to patient
dimensionally stable
good handling properties
```
110
advantages of alginate being water based (7)
```
economical
easy to use
quick setting
fair taste
hydrophobic
displaces blood/saliva
stock trays
```
111
disadvantages of alginate being water based (5)
```
limited detail reproduction
low tear resistance
single pour only
quick pouring required
low dimensional stability
```
112
inherently hydrophobic, but addition type can be made hydrophilic
condensation type was first introduced
hydrophobic but chemically and dimensionally stable
cross-linked by hydrosilation reaction
hydrophobicity may lead to voids when stone added
polysiloxanes
113
polysiloxanes can be made hydrophilic by simple addition of a ________ or chemical incorporation go hydrophilic moieties into _________ backbone
surfactant
| silicone
114
improve detail registration and detail transfer for polysiloxanes - makes more hydrophilic
surfactants (can also use polyethers)
115
```
hydrophobic, but more hydrophilic than polysiloxanes
bad tasting
adhesives work well
good dimensional stability
fast stting
stiff and low tear strength
```
polyethers
116
dehydrated form of calcium sulfate
gypsum materials
117
process of driving off water of calcium sulfate hemihydrate to form gypsum
gives rise to differences in gypsum materials
straightforward and reversible reaction
heat is released (exothermic)
calincation
118
when setting, growth and subsequent interlocking of gypsum _______ occurs
contributes to _______ and dimensional change
physical and mechanical properties can be influenced by differences of these
crystals
| strength
119
gypsum properties dependent on _________ and _________ structure
density and crystal structure
120
dental stone used for ______, not plaster
models
121
dense, regularly shaped, relatively nonporous cubodial crystal material
requires less water and is 2.5x stronger than plaster
widely used in cast making and molds requiring high crushing strength and abrasion resistance
dental stone
122
______ based materials have to last a long time
have a filler and dimethacrylate that cross links
provisional are normally temporary
denture
123
denture base is normally ______ cured
| TRIAD is a custom tray material and is also _____
VLC
| visibly light cured
124
provisional materials are normally ________ cured
similar to TRIAD cold cure not light cure
curing achieved by mixing
chemically
125
designed to absorb impact
high toughness, low rigidity
thermoplastic materials
can be melted or pressure processed
mouthguards
126
low softening point
thermally processed with hot water
vacuum formed - requires a dye
thermoplastic polymer
127
designed to absorb impact
high toughness, low rigidity
can't be melt of pressure processed
copolymer controls properties
128
used to bind restoration of appliances to tooth structure
cements
129
glass ionomers
resin modified glass ionomers
zinc phosphates
zinc polyacrylate
water based cements
130
composites and compounds
resin based cements
131
zinc oxide eugenol
oil based cements
132
requirements for cements (2)
low viscosity but good mechanical properties
| 25um thickness
133
how to balance the mechanical properties and viscosity of water based cements
adjust powder-liquid ratio
[powder = filler]
more filler = more viscosity = more modulus
low P:L ratio increases working time and setting time
134
resin cements are typical a one component system
viscosity and strength controlled by ______ loading
also by _____ molecular weight monomers
increased filler loading = increased ____ and ____
ortho bonding needs to be reversible
similar to composite resins
filler
low
viscosity and modulus
135
advantages of glass ionomers (5)
```
adheres to tooth structure
fluoride release
clinical record of retention (better than composite)
dimensionally stable
biocompatible
```
136
disadvantages of glass ionomers (5)
```
slow setting
early dissolution
optical properties
stain resistance
poor physical properties
```
137
protects pulp and minimizes post-op sensitivity
acts and thermal and chemical barrier
controls inflammation of pulp
controls fluid movement
liner and bases
138
relatively thin layer of material used to protect dentin from residual reactants that diffuse out of the restrain or oral fluids that may penetrate leaky restoration interface; lower viscosity
liner
139
provides thermal protection for the pulp to supplement mechanical support for the restoration by distributing local stress from the restoration across the underlying dental surface during amalgam condensation
requires greater mechanical properties
viscosity doesn't matter
base
140
defensive reparative dentin
15 days cell differentiates
30 days microscopic reparative dentin
15 days radiographic reparative dentin
pulp capping
141
in ______ pulp capping, you apply a calcium hydroxide layer
direct
142
zinc oxide eugenol (ZOE) - pain reduction = _______ ________
sedative restoration
143
```
intermediate restorative material
base and temporary - reinforced fillers, ZnO powder,
oil of clove (dulls pain)
expands when set-seals
can use under a composite
inhibits polymerization
```
reinforced zinc oxide eugenol (ZOE)
144
```
temporary materials
melts at a lower temperature
carve-able
burns off
dimensionally stable
lower molecular weight in-between polymers and organic liquids
```
waxes
145
Low Cu amalgam doesn't have a ______ phase, so therefore creep is more prevalent
N'
146
Cu6Sn5 is the ________ phase
| It prevents the sliding of gamma 1 thus minimizing creep and marginal breakdown
n' phase
