BioMaterials Flashcards
A material used to construct artificial organs, rehabilitation devices, or prostheses and replace natural body tissues, without causing any hard or negative reactions
Biomaterials
What are the three main classes of materials
Metals
Polymers
Ceramics
Mechanical properties of metal (3)
Hard
Ductile/tough
Strong
Bonding of metals: metallic elements have \_\_-\_\_ electrons in outer shell Electrons are key to \_\_\_\_\_\_\_\_\_\_\_ Electrons are \_\_\_\_\_\_\_\_ bound to nucleus Electrons have \_\_\_\_\_ mobility
1-3
key to metallic bonds
loosely
free mobility
What is the microstructure of pure metals (4)
Molten metal –> nuclei of crystallization –> crystal growth —> formation of crystal grains
Polycrystalline structures = pure _____
Metals
Thermal properties of metals
High processing temperature (except amalgam)
Metal alloys are processed for __________ and __________
Alloys are ______ and _____ ductile than pure metals
Cast metals for crowns and amalagms
Stronger and less ductile
Mechanical properties of ceramics (3)
Hard
Brittle
Strong
Bonding of ceramics via _____ and _______ bonds
Both are stronger than _______ bonds
Covalent and ionic
Metallic
Electron donor and acceptor
Weaker
Ionic bonds
Equally share electrons; non mobile ions
Covalent bonds
Thermal properties of ceramics
High processing temperature except cements
How ceramics are processed
Indirect placement
Microstructure of ceramics:
Mixture of _______ and ___________ elements
Most common ceramics in dentistry are 3 metal oxides….
_____ is a tetrahedron
Metallic and non-metallic
Most common ceramics: SiO2, Al2O3, K2O
SiO2 is the tetrahedron
Microstructure of ceramics:
Crystalline (long range order), crystalline silicate-_____, or _________; and ________
Crystalline (short range order) or amorphous silicate (______)
Most dental ceramics are ___________ or ______________
Silicate-quartz, crystobilite; and leucite
Glass
Semicrystalline or polycrystalline
Mechanical properties of polymers (3)
Soft
Ductile/tough
Weak
Bonding of polymers:
_________ bonds
High _______ weight
Long molecules composed of _________ elements and ________ elements (COHN)
Polymers are entangled in ______ chains
Derive strength and properties from ___________
Covalent Molecular Nonmetallic and organic Long Entanglement
Thermal properties of polymers
Lower processing temp except indirect composites
Processing of polymers:
Used as _______ processing materials
_________ placement
Polymerization; ___________ —-> _____________
Direct
Direct
Monomers –> polymers
Steps of polymerization (4)
- 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
What factors contribute to each materials mechanical properties (4)
atomic rearrangements (crystalline vs non-crystalline)
bonding
composition
defects
polymerization can be initiated by theses three things
light
heat
chemical mixing
ability to slide chains by each other
linear polymer (monomethacrylates)
covalent bonds; stronger and more brittle
limits movement
will not dissolve
cross-linked polymer (dimethacrylate)
physical mixture of metals, ceramics, and/or polymers
composite
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
chemically bonded to resin phase (matrix) to improve properties
fillers
relative rate of change during temperature changes
coefficient of thermal expansion
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
Teeth are ______ due to high mineral content
dental pulps can withstand small temperature changes over _____ times
insulators
short
metals have a _____ thermal conductivity so they need a _____-like base before placement
high
insulator
composites have a _____ thermal conductivity and do not need a base
low
defined on a 3D coordinate system
Color;
value (intensity), hue (wavelength), and chroma (purity)
material may have a different color under a different light source
metamerism
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
Patient Issues with Amalgam;
some patients may exhibit ________ _____ _______
many _________ are used
allergic skin reaction
alternatives
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
dental amalgams are any alloy made of Hg with a _____-____ alloy with varying amounts of ____ and small amounts of zinc
silver-tin
copper
zinc
Benefits of high copper amalgam (4)
greater clinical longevity
lower creep values
corrosion resistance
contains >12%
Zinc-containing vs zinc free (3)
zinc facilitates lathe-cut particles
improves corrosive resistance
no concern with Zn-free alloys about moisture contamination
Mercury to Alloy ratio
0.05, but depends of manufacturer
Silver –> Hg
major reaction phase in both high and low copper amalgam
Gamma 1 (product)
Tin —> Hg
only seen in low copper amalgam
Gamma 2 (product)
gamma is the _____ material + Hg –> reaction phases (____) + _______ alloy particles (core)
starting alloy particles
matrix
unreacted
first step in setting process of amalgam
both gamma 1 and gamma 2
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
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
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
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
Alloy particles have complex structure with three phases
γ(Ag3Sn) β(Ag-Sn) ε(Cu3Sn)
lathe cut
creates a wide range of sizes
from cast ingot
corrosion at inter proximal contact with gold alloys
galvanic corrosion
corrosion due to multiple phases
anode (corroding metal) and cathode (different metal) [2 different phases in amalgam]
ionic movement
electrochemical corrosion
corrosion at margins
crevice corrosion
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
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)
wetting can be anticipated on the basis of _______ and ________ of materials
hydrophobicity and hydrophilicity
allow penetration into areas with water
usually mixed with solvent (alcohol/acetone)
very low viscosity
allows for attachment to composite
hydrophilic fibers
angle where a liquid interference meets a solid surface
contact angle
ability of a liquid to maintain contact with surface
wet-ability
molecules can have _____ hydrophobic and hydrophilic properties
both
spontaneous destructive oxidation of metals (all metals do this)
corrosion
immune to corrosion
noble metals, like gold
produces a corrosive film that prevents further corrosion
titanium implants
Passive corrosion
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
absorption of water into the _______ (secondary bonds), causes a _________ change
hydrolytic degradation and release of components (primary bonds)
-water, enzymes, bacterial byproducts
polymers
dimensional
degradation products are related to
toxicity
Stress-Strain Curve
x axis = _____
y axis = _____
linear portion = _____
strain
stress
modulus
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
point on modulus from which the line starts to curve, and begin to irreversibly deform
elastic limit
area under curve to point of elastic strain (reversible deformation)
resilience
area under curve to point of fracture due to plastic strain (irreversible deformation)
toughness
_____ 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
multiple cycles of low stress
fatigue
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
create small cracks at one area, which eventually causes breakage at that point
cyclic stress
study of stress and strains
effects of forces on the motion of biomaterials and biologic structures
biomechanics
teeth are not completely ______, can lead to abfraction
rigid
________-______ stability due to enamel on sound dentin
when a tooth is unrestored, it is very strong
buccal-lingual
when the enamel wall is no longer ______, its resistance to fracture is much lower
AKA ________ weaken teeth
continuous
preparations
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
components of a composite resin (4)
organic resin phase
inorganic filler phase
bonding agent
visible light initiator
helps with the processing and handling of composites
BISGMA provides physical properties
viscosity high and cannot be used alone
resin
helps modulus and wear resistance
filler
trade offs of composite resins;
wear resistance and strength but ____ and has ___ processing
poor wear resistance but ___ with ____ processing
brittle, poor
tough, good
joining of polymers with covalent linkages
cross linking
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
different ____ sizes exist and control properties
silica or zinc inorganics
50-80% weight of composite
has surface -OH groups
filler
higher filler loading results in a \_\_\_\_\_\_ modulus, \_\_\_\_\_\_ strength \_\_\_\_\_\_ viscosity \_\_\_\_\_\_ in shrinkage
increase
increase
increase
decrease
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
binds inorganic filler so filler can bind to organic resin
uses the OH group on filler
forms chemical bridge
coupling agent
results from a density change of monomer to polymer
polymerization shrinkage
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
clinical consequences of shrinkage (2)
causes stress on tooth structure
can cause micro leaks and lead to secondary caries
2 components of glass-ionomer cements
acidic polymer and aqueous (water) solution (polyacid)
basic glass (aluminaflurosilicate)
+ a modifier
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
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-
how GI reaction differs from composite
no coupling agent needed
F- released
mechanisms not clearly understood
water based restorative
important for forming a mechanical bond as opposed to a chemical bond
microtags
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
differences between adhesives and composites (2)
lower level of filler to decrease viscosity in adhesives
additives in adhesives that help in bonding
both hydrophobic and hydrophilic properties are needed because composites are _______ and enamel/dentin is _________
hydrophobic
hydrophilic
designed to flow into pits
prevents further decay
etching recommended to prepare enamel
sealants
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
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
used to make a negative mold of dental structures
transfer to gypsum model (plaster/stone)
impression materials
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)
hydrophobic, synthetic impression materials
polysulfides, siloxane, polyethers
viscoelastic
ideal properties of impression materials (6)
low cost long shelf life biocompatible pleasant to patient dimensionally stable good handling properties
advantages of alginate being water based (7)
economical easy to use quick setting fair taste hydrophobic displaces blood/saliva stock trays
disadvantages of alginate being water based (5)
limited detail reproduction low tear resistance single pour only quick pouring required low dimensional stability
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
polysiloxanes can be made hydrophilic by simple addition of a ________ or chemical incorporation go hydrophilic moieties into _________ backbone
surfactant
silicone
improve detail registration and detail transfer for polysiloxanes - makes more hydrophilic
surfactants (can also use polyethers)
hydrophobic, but more hydrophilic than polysiloxanes bad tasting adhesives work well good dimensional stability fast stting stiff and low tear strength
polyethers
dehydrated form of calcium sulfate
gypsum materials
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
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
gypsum properties dependent on _________ and _________ structure
density and crystal structure
dental stone used for ______, not plaster
models
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
______ based materials have to last a long time
have a filler and dimethacrylate that cross links
provisional are normally temporary
denture
denture base is normally ______ cured
TRIAD is a custom tray material and is also _____
VLC
visibly light cured
provisional materials are normally ________ cured
similar to TRIAD cold cure not light cure
curing achieved by mixing
chemically
designed to absorb impact
high toughness, low rigidity
thermoplastic materials
can be melted or pressure processed
mouthguards
low softening point
thermally processed with hot water
vacuum formed - requires a dye
thermoplastic polymer
designed to absorb impact
high toughness, low rigidity
can’t be melt of pressure processed
copolymer controls properties
used to bind restoration of appliances to tooth structure
cements
glass ionomers
resin modified glass ionomers
zinc phosphates
zinc polyacrylate
water based cements
composites and compounds
resin based cements
zinc oxide eugenol
oil based cements
requirements for cements (2)
low viscosity but good mechanical properties
25um thickness
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
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
advantages of glass ionomers (5)
adheres to tooth structure fluoride release clinical record of retention (better than composite) dimensionally stable biocompatible
disadvantages of glass ionomers (5)
slow setting early dissolution optical properties stain resistance poor physical properties
protects pulp and minimizes post-op sensitivity
acts and thermal and chemical barrier
controls inflammation of pulp
controls fluid movement
liner and bases
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
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
defensive reparative dentin
15 days cell differentiates
30 days microscopic reparative dentin
15 days radiographic reparative dentin
pulp capping
in ______ pulp capping, you apply a calcium hydroxide layer
direct
zinc oxide eugenol (ZOE) - pain reduction = _______ ________
sedative restoration
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)
temporary materials melts at a lower temperature carve-able burns off dimensionally stable lower molecular weight in-between polymers and organic liquids
waxes
Low Cu amalgam doesn’t have a ______ phase, so therefore creep is more prevalent
N’
Cu6Sn5 is the ________ phase
It prevents the sliding of gamma 1 thus minimizing creep and marginal breakdown
n’ phase
