Overview of Biomaterials- Amalgam and Intro to Composite Flashcards
1
Q
Any substance, other than a drug, that can be used to treat,
augment, or replace any tissue, organ, or function of the body is a
A
biomaterial
2
Q
•All dental materials which involve exposure to patients are
considered
A
biomaterials
3
Q
4 Major Classes of Dental Materials
A
Metals and Alloys
Porcelains and Ceramics
Polymers
Composites
4
Q
Polymers (2)
A
◦ Elastomeric (impression materials)
◦ Plastics (denture base, sealants)
5
Q
Composites (1)
A
◦ Polymers with fillers
6
Q
American Dental Association specifications (2)
A
◦ More than 10 specifications for dental materials, instruments, and equipment
◦ Restorative material specifications: related to material properties that should reflect clinical function
7
Q
Restorative material specifications: related to material properties that should reflect clinical function (3)
A
◦ In vitro (in glass)- tested in the laboratory
◦ In vivo (in the living being)
◦ Extrapolation of in vitro data to in vivo conditions should be done with caution
8
Q
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Food and Drug Administration (4)
A
◦ Safety, Efficacy
◦ Protect the public from hazardous or ineffective medical materials and devices
◦ 2009 FDA reclassification
◦ Direct to Consumer Orthodontics?
9
Q
2009 FDA reclassification (3)
A
◦ Reclassified amalgam from class I to class II
◦ Class I: lowest risk à Class III: highest risk
◦ Same as composites, crown and bridge alloys
10
Q
Performance of all dental materials depends on their
A
atomic structure
11
Q
Atomic structure determines (2) of materials
A
mechanical and physical properties
12
Q
Types of interatomic bonds (2)
A
◦ Primary: Ionic, covalent, metallic
◦ Secondary: Hydrogen bonds, Van der Waals force
13
Q
Primary Bonds: Ionic
A
Electrostatic attraction of positive and negative charges
14
Q
Primary Bonds: Ionic
Involves — — between ions
A
electron transfer
◦ One becomes positive, one becomes negative ex. NaF)
15
Q
Primary Bonds: Ionic
Properties (2)
A
◦ non-directional, strong bonds (100-200kcal/mole)
◦ No free electrons, good thermal and electrical insulator
16
Q
Primary Bonds: Ionic examples (2)
A
◦ Ceramics, gypsum
17
Q
Primary Bonds: Covalent
A
2 atoms share an electron
18
Q
Primary Bonds: Covalent
Properties (3)
A
◦ Directional bonds (50-100kcal/mole)
◦ Low electrical and thermal conductivity
◦ Water insoluble
19
Q
Primary Bonds: Covalent
Examples (4)
A
◦ Water, glass, polymers, composite
20
Q
Primary Bonds: Metallic
A
Cluster of positive metal ions surrounded by a gas of electrons
21
Q
Primary Bonds: Metallic
Properties (2)
A
◦ Non-directional bonds (100 kcal/mole)
◦ High electrical and thermal conductivity
22
Q
Primary Bonds: Metallic
Examples (2)
A
◦ Amalgam and gold alloys
23
Q
Classification of Material Properties (4)
A
Biological
Surface
Physical
Mechanical
24
Q
Biological Properties
A
The biological response to a material when in contact with the human body
25
Biological Properties
| Dental examples: (3)
◦ Allergies
◦ Pulp response
◦ Gingivitis, inflammation
26
Surface Properties
The unique properties of a material associated with its surface
27
Surface PropertiesExamples
Surface energy/tension; surface wetting
28
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| Dental examples of importance of surface wetting (6)
```
◦ Making and pouring impressions
◦ Investing and casting
◦ Tooth pellicle
◦ Denture retention
◦ Fluoride treatment
◦ Adhesive bonding
```
29
Physical Properties
| Depend on
the type of atoms and the bonding present in material
30
Physical Properties
| Size/Shape Effect
no effect
| -structure insensitive
31
Physical Properties
| Examples (3)
◦ Optical (color, translucency, gloss)
◦ Electrochemical: Tarnish, Corrosion
◦ Thermal: Conductivity, Diffusivity, Coefficient of thermal expansion
32
Thermal conductivity
◦ Quantity of heat passing through 1cm thickness of material
33
Thermal diffusivity
◦ How quickly crown interior approaches temperature of exterior
34
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| Thermal Expansion Coefficient
(α)(20-50°C)
Α= final length-original length
original length x (*C final - *C original)
35
Mechanical Properties
Reaction of a material to the application of an external force
36
Mechanical Properties
| Size/Shape effect
Size and shape of specimen affect properties
| ◦ Structure sensitive
37
Mechanical Properties
| Applied force referred to as ---
load
38
Stress
When load (force) applied to material, STRESS develops in response
39
Stress=
Load per unit area
| ◦ Measured in psi, MPa, kg/cm2
40
Fracture Stress- Strength
There is a limit to how much force a material can withstand before it breaks
41
Strength of material=
stress at fracture
42
Type of strength measured is dependent on
type of force applied
43
Types of Force/Stress (5)
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Tensile
Compressive
Torsion
Shear
Flexure
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44
Tensile Strength- PULLING force
Measure of the stress necessary to fracture a material by 2
| opposing forces directed away from each other
45
Lowest strength for most materials
Tensile Strength- PULLING force
46
Tension pulls the
atoms and structure apart
| ◦ Failure occurs at lower loads
47
Highest strength measure for most materials
Compressive Strength- PUSHING force
48
Compressive Strength- PUSHING force
Measure of the stress necessary to fracture a material by 2 opposing forces directed toward each other
49
Compression pushes
atoms and structure closer
| ◦ Usually require higher loads to cause failure
50
Torsion Strength- TWISTING force (4)
```
Not relevant to direct or indirect dental restorations
Torque wrench (torsion) used to place dental implants
Torsion test of experimental dental implant-bone interface stability/strength of
osseointegration
Torsional fatigue of endodontic rotary files
```
51
Shear Strength- SLIDING force (3)
Typically, intermediate strength between compressive and tensile
Stress necessary to rupture a material by 2 opposing parallel forces directed
toward each other but not in the same plane
Clinical situation with shear force/shear strength- implant bone interface
52
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| Shear stress/strength at implant-bone interface (2)
Cylinder (press fit) implants: high shear
| Threaded implants
53
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Threaded implants (2)
```
◦ Compressive stress below each thread (More ideal bone loading)
◦ Tension above thread, often see bone loss to level of 1st thread
54
Flexural Strength- BENDING force (2)
Measure of stress to cause failure in bending
| Flexural stress/strength relevant in numerous clinical situations
55
3-point Bend test (2)
◦ Compressive load
| ◦ Combination of compressive & tensile stress
56
Flexural strength is vital due to occlusal load (3)
◦ On direct restorations (Amalgam and composite)
◦ Indirect restorations (Bridges/FDPs, single crowns, onlays)
◦ Removable prosthodontics (Palatal flex in maxillary denture)
57
Examples of DENTAL STRESS (2)
Protrusive movement
| Posterior occlusion
58
Protrusive movement (2)
◦ Anterior teeth
| ◦ Flexure load on incisors
59
Posterior occlusion (3)
◦ Chewing = compressive load
◦ At marginal ridge contact areas
◦ At fossa areas
60
Occlusal Stress=
```
Occlusal load (force)/
Occlusal contact area
```
61
TRIPODIZED occlusal contacts
◦ Allows distribution of occlusal load across
maximum area
◦ = minimized stress
62
Premature contact results in decreased ---
AREA
63
Premature contact results in decreased AREA
| occlusal force? occlusal stress?
◦ Patient’s occlusal force stays the same
| ◦ BUT OCCLUSAL STRESS IS INCREASED
64
BUT OCCLUSAL STRESS IS INCREASED (2)
◦ Potential restoration failure
| ◦ Potential pain/discomfort for patient on biting
65
Strain
The DEFORMATION that occurs in a material when force is
| applied to the material
66
Strain=
change in length (deformation)/
| unit original length
67
how are stress and strain interrelated?
◦ If you have one, you will have the other
68
ELASTIC Strain
The TEMPORARY distortion of a material by applied force
69
elastin strain:
| Strain is BELOW THE
ELASTIC LIMIT
70
elastic strain:
| When force is removed, materials
reverts to original form
| ◦ Ex. Rubber band
71
PLASTIC Strain
PERMANENT distortion of a material
72
plastic strain:
| Strain is
BEYOND the elastic limit
◦ Elastic portion of strain recovered
◦ Plastic portion of strain NOT recovered
73
plastic strain:
| When force is removed, shape
remains changed
| ◦ Ex: bending a paper clip
74
Many benefits to amalgam: (4)
Easy to manipulate
Can be placed in its plastic state and carved before it hardens
Excellent physical properties
Cost effective (Including time to place)
75
Excellent physical properties (4)
◦ Strong and predictable
◦ Self-sealing
◦ Due to corrosion over time
◦ = effective barrier against recurrent caries
76
```
Amalgam composition:
Kerr Contour Amalgam:
Ag --%
Sn --%
Cu: --%
--% spherical, --% lathe cut
```
41
31
28
70
30
77
Amalgam- Composition
| In capsule with powder, mixed with
liquid mercury in triturator
78
Conventional Amalgam (2)
◦ Similar to G.V. Black’s original formula
| ◦ “low copper”
79
High Copper Amalgam (3)
◦ Contain 9-30% copper
◦ Superior to conventional
◦ Presence of copper nearly eliminates gamma-2 phase, resulting in stronger restoration
80
Phases of amalgam setting: (3)
Gamma
Gamma 1
Gamma 2
81
Gamma
◦ Tin and silver react with mercury, forms silver-mercury (gamma-1) and tin-mercury (gamma-2)
◦ Strong, corrosion resistant
82
Gamma-1
◦ Silver-mercury
| ◦ Weaker, susceptible to corrosion
83
Gamma-2
◦ Tin-mercury
| ◦ Weakest, most susceptible to corrosion
84
Add Copper=
creates a copper-tin phase (eta), eliminates tin-mercury gamma-2 phase
85
Lathe (2)
◦ Outdated- particles formed by cutting block of alloy with a lathe
◦ Resulted in large, irregular particles
86
Admixed (4)
◦ Lathe type particles mixed with small spheres
◦ Require more condensation force
◦ Most commonly used type of amalgam
◦ Low early strength (1-hour)
87
Spherical (4)
◦ Spherical shape
◦ Higher early strength (1-hour) and higher 24-hour strength than Admixed
◦ May be more difficult to achieve interproximal contact
◦ Require less condensation force
88
•Mercury to Alloy ratio (4)
* Less mercury in final restoration is superior
* Better strength and corrosion resistance
* Proper condensation and finishing results in less mercury in final restoration
* Admixed alloys ~50% mercury, Spherical alloys slightly less
89
•Trituration (3)
* Mixing the amalgam
* Longer and faster trituration= sets faster
* Follow manufacturer’s guidelines
90
•Condensation (2)
* Most critical variable
| * Undercondensation is the most common error made by dentists
91
•Carving and Finishing (1)
• Pre-carve and post-carve burnish recommended with high copper alloys
92
Overwhelming evidence that supports the safety of amalgam (3)
◦ Mercury vapor is released in chewing
◦ No side effects at such low doses (Such as those from having amalgam restorations in your mouth)
◦ Dental Professionals exposed to more mercury vapor than non-dental professionals (Would expect more adverse health affects due to exposure, but that is not the case)
93
Most of the “data” that suggests amalgam is
unsafe is anecdotal
| ◦ (Looks like they’re going after root canal treatment now)
94
Amalgam has not been found to play a role in --- diseases
neurodegenerative
95
Why not remove amalgam due to mercury concerns? (3)
◦ Unwarranted loss of tooth structure
◦ Unnecessary expense
◦ Limited longevity when replaced with inappropriate tooth colored restoration
96
Ways to classify composites (3)
◦ *Filler
◦ Handling
◦ Activation
97
Curing-
lights and methods
98
SKIPPED
| History of Tooth-colored Materials
```
Silicate cement, 1870’s, high solubility
Polymethyl methacrylate (PMMA), 1940’s
◦ Unfilled resin
◦ MMA resin mixed with PMMA polymer beads
◦ High polymerization shrinkage (7%),
High thermal expansion (90 ppm/°C)
◦ Marginal leakage
◦ Low strength
Composite resin, 1960’s
```
99
Composite
| Definition:
a physical mixture of 2 or more materials with superior
| properties as compared to the individual components.
100
Composite examples (4)
◦ Concrete: cement + gravel
◦ Fiberglass
◦ Dentin: collagen matrix + hydroxyapatite crystals
◦ Dental composites: Resin + Filler particles or Fibers
101
Dental Composite Uses (5)
1. Tooth-colored restorative material
2. Bonding agents (filler may be present)
3. Sealants (filled)
4. Composite resin luting agents (cement)
5. Resin-modified glass ionomer material
102
Dental Composite:
--- colored restorative material
Resin matrix phase reinforced by ---
May be referred to as: (4)
Tooth
dispersed filler particle phase bound to the resin by a silane coupling agent
composite resin, resin composite, composite
103
Dental Composite Components (6)
a. Resin matrix- Bis-GMA, TEGDMA
b. Filler particles - (Quartz, colloidal
silica)
c. Coupling agent
d. Activator-Initiator systemPhotoinitiator-camphorquinone
(sensitive to 470 nm visible light)
(Yearn, 1985)
e. Polymerization inhibitors
f. Optical modifiers
104
Bis-GMA:
bisphenol A diglycidyl methacrylate
| ◦ Matrix in US products
105
TEGDMA: triethyleneglycol dimethacrylate (3)
◦ ~30% added to Bis-GMA or UDMA
◦ diluting agent
◦ used to dilute the BisGMA and UDMA, which is very viscous
106
Too much TEGDMA will however increase the amount of
polymerization shrinkage. Helps to promote
extensive cross linking and results in a matrix that is more resistant to degradation by solvents. TEGDMA
is another difunctional monomer.
107
UDMA:
urethane dimethacrylate
| ◦ Matrix in European products, instead of Bis-GMA
108
Filler Particles
```
Crystalline silica (quartz),
Ba, Li, Al silicate glass, amorphous silica
```
109
Filler Particles are dispersed in
resin matrix
110
Filler Particles distribution varies depending on the
material
◦ filler loading %, expressed by weight or by volume
◦ filler size, and
◦ filler
111
Benefits of Filler Particles (6)
1.Reinforcement of resin matrix:
◦ Increase hardness, strength, elastic modulus, and wear resistance
2.DECREASED polymerization shrinkage: ~10% to ~2%
3.DECREASED thermal expansion and contraction
1.Fillers don’t expand or contract
4.Improved workability, handling
5.DECREASED water sorption
6.INCREASED radiopacity (Barium, Strontium, Zirconium)
112
Filler Size Distribution
| Good distribution necessary to
incorporate maximum amount of filler
113
Silane (4)
◦ Couples filler to resin matrix
◦ Allows stress transfer from flexible matrix to higher
modulus (aka less flexible) filler particle
◦Improves the mechanical properties
◦ Decreased water sorption along filler-resin
interface
114
```
Resin polymerization (free radical
addition rxn)
◦ Activation:
◦ Initiation:
◦ Propagation:
◦ Termination
```
◦ Activation: Activator converts initiator into a free radical
◦ Initiation: Free radical initiator starts the addition reaction
◦ Propagation: continued polymer chain growth
◦ Termination
115
Polymerization Inhibitor
| Prevent
spontaneous polymerization when dispensed
116
Polymerization Inhibitor
| Stop polymerization from
brief room light exposure (reacts with free
| radicals)
117
Polymerization Inhibitor
| Once the blue light is used,
all inhibitor quickly consumed= polymerization
| chain reaction starts.
118
Butylated hydroxytoluene (BHT)
◦ Food preservative, reduce oxidation
119
Pigments:
metal oxides
120
Opacifiers: (4)
◦ Titanium and aluminum oxide
◦ Control opacity or translucency
◦ Brand differences
◦ Dentin vs enamel composite shades
121
Different ways to classify composites based on: (3)
* Filler particle size and size distribution
* Handling characteristics
* Type of polymerization
122
Classification by Filler Size and Distribution (4)
1. Macrofill
2. Midifill
3. Microfill
4. Hybrids
123
4. Hybrids (3)
a. Midi-Micro Hybrid (Midi- or Microhybrid)
b. Mini-Micro Hybrid (Microhybrid)
c. Mini-Nano Hybrid (Nanohybrid)
124
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| Macrofill & Midifill Composites
```
NOT USED MUCH TODAY
10-100 µm (macro)
1-10 µm (midi)
65-70 wt%
Large fillers
◦ Rough surface finish
Not good size distribution
◦ Increased inter-filler resin space, low wear resistance
Prone to staining
Brands: Adaptic (macro)
Concise (midi), still on market
```
125
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| Microfill Composite
```
0.01-0.1 µm particles, colloidal silica
40-60 wt%
◦ Due to large filler surface area, difficult to increase filler fraction, too viscous
Excellent finish, Best wear resistance
Weakest
Use for esthetic, low-stress sites
◦ Class III
◦ Layer over hybrid, kit systems
Brands: Durafill VS, Epic TMPT, Renamel, Heliomolar
```
126
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| Hybrid Composites
```
Midi-Micro Hybrid (First hybrids)
◦ Typically called Microhybrids
◦ Mix of midi and microfillers,
1-10 & 0.01-0.1 µm
◦ 75-80 wt%
◦ Improved surface finish
compared to macro and midi composites
◦ High strength
◦ Many of the of current materials are hybrid
◦ Z250, Z100, Herculite, TPH, APH, Point 4
```
127
skipped
| Mini-Micro Hybrid
a. Also called Microhybrids
b. Mix of mini and microfillers,
0. 1-1 and 0.01-0.1 µm
c. 80-85 wt%
d. Newer material
1) Smoother finish than midi-micro hybrid
2) Slightly lower strength
e. Clearfil APX, 4-Seasons, Miris, Vitalescence, Synergy, Tetric, EsthetX
128
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| Mini-Nano Hybrid (Nanohybrid)
◦ Nanometer: 10-9 Micrometer: 10-6
◦ Mix of mini, and nanofillers,
0.1-1 and 0.001-0.01 µm (1-10 nm)
◦ ~80 wt%
◦ Newest materials: Filtek Supreme Ultra (what is used in clinic), Premise,
TPH3 (what you use in lab), Simile
◦ Strength comparable to microhybrids and finish
equivalent to microfills
◦ Not all “nanocomposites” contain nanofiller (<100
nm), filler size reported in nm,
i.e. 300 nm
129
Classification by Handling Characteristics (2)
1. Flowable
| 2. Packable
130
Flowable Composite
Low viscosity hybrid
reduced filler,
40-60 wt%, adapts better without handling ◦ Lower filler percentage, decreased modulus, increased flexibility
◦ Used under conventional composite at gingival floor of Class II
◦ Thought may compensate for polymerization shrinkage stress and reduce gap formation at gingival
floor; however, research does not support theory.
Many are not radiopaque
131
Many are not radiopaque
| ◦ Big problem=
difficult to distinguish from recurrent
| caries
132
RADIOPACITY
| Distinguish between
composite and recurrent caries
| Barium, strontium, zirconium filler
133
Flowable vs Hybrid
handling characteristic
filler characteristic
134
Flowable (2)
◦ more shrinkage (is lower filled)
| ◦ less stress (has more resin to relieve the stress as it cures)
135
Hybrid (2)
◦ less shrinkage (is higher filled)
| ◦ more stress
136
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Bulk fill
Newer technology-
Need high output lights ~
Are highly filled with...
```
bulk fill
1000 Mw/cm2
more translucent fillers (which do not shrink) and less resin matrix (which shrinks)
◦ Higher filled have more stress because there is less resin to relieve the stress when it cures
137
Classification by Polymerization
| Activation (3)
1. Self-cure, chemical activator
2. Light-cure, blue light activator
3. Dual-cure, combination of both
138
Light-cure Composite
```
One-paste system
Activator: Blue light (~470 nm)
Initiator:
◦ Camphorquinone (CQ), photoinitiator
◦ DMAEMA, alphiatic amine (accelerator)
```
139
Light-cure Composite
| Advantages (3)
a. Mixing not required, less porosity, increased
strength
b. Aliphatic amine (DMAEMA) more color stable
than self-cure aromatic tertiary amine
c. Better control of working time
140
Light-cure Composite
| Disadvantages (2)
a. Limited light penetration, ≤ 2mm increments, 20
sec
b. Blue light, retina damage – use orange shield
141
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| Curing equipment factors (4)
◦ Bulb output, ≥ 300-400 mW/cm2 (11mm tip)
(Not below 300 mW/cm2, Not below 550 mW/cm2 for TPH3 or Filtek Supreme)
◦ Fiber-optic bundle breakage
◦ Tip contamination or damage
◦ Infection barrier
142
Types of curing units: (4)
1. Quartz-tungsten-halogen
2. Plasma Arc
3. Laser
4. Light-emitting diodes (LED)
143
```
Light-cure Variables
Procedural factors (3)
```
◦ Exposure time
◦ Tip size: smaller tip= increase output, increase heat
◦ Distance: decrease Output when you increase
distance
144
```
Light-cure Variables
Restoration factors (3)
```
◦ Darker shades absorb light
◦ Smaller particles: increase light scatter
◦ Curing through tooth (decrease output)
145
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Curing Lights: Quartz tungsten halogen
(QTH)
Usually tested with an 11 mm diameter light tip
◦ However, if a 3 mm diameter tip is used then the output can increase 8 fold which also can
heat up the tooth greater than the 5-8 degrees that can cause pulp cell death
Don’t touch the tip to the material being cured
At 6.0 mm distances from the restoration the output at the tip can be 1/3 what
it should be.
Never look directly at the light it can cause retinal damage.
146
skipped
| Curing Lights: QTH– soft start or ramp cure
Starts low intensity, intensity increases
over time of cure
The theory is that a soft cure can allow
some stresses to be relieved in the
composite resin before it reaches the gel
stage; forms stronger long-chain polymers, decreases polymerization shrinkage
147
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Light Curing: equipment factors
Factors that reduce light output (4)
◦ Frosting of bulb, Light reflector degradation, Fiber optic bundle breakage
◦ Tip contamination by resin buildup - lower output
◦ Sterilization problems - frosting the tip
◦ Infection control barriers - need longer curing time
148
Classified by Activation:
| Dual-cure Composite (4)
Both light and chemical activator/initiator systems present
Used under ceramic inlays, onlays, crowns
◦ Composite cement
◦ Accommodate thicker areas, light may not penetrate adequately
149
Oxygen inhibited layer
~15 microns thick, on the outer layer which facilitates addition and wetting of subsequent
layers.
Just-cured composite may have 50% of the unreacted methacrylate groups to copolymerize
with the newly added material
Older restorations – will fully cure over time, do not have the unreacted methacrylate
groups
◦ Repair strength will be 50% of the original restoration. (Roughen with diamond)
150
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Important Properties of Dental
Composite (7)
1. Thermal expansion and contraction
2. Sorption
3. Surface finish
4. Wear resistance
5. Strength, elastic modulus
6. Degree of Conversion
7. Polymerization shrinkage
151
With polymerization shrinkage, stress occurs at the composite-tooth
interface. (3)
◦ Stress level will vary, depending on the type of restoration
configuration factor, C-factor
◦ C-factor = bonded/unbonded surfaces
Highest stress is Class I restoration (~13-17 Mpa)
152
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| Gap formed between adhesive and tooth
~ 5-20 microns
153
Managing Polymerization Shrinkage/Stress (5)
```
Incremental placement
◦ ¯ bonded/unbonded, each increment
◦ ¯ C-Factor, ¯ polymerization stress
◦ Is shrinkage reduced?
◦ No, stress is reduced
```
Self-cure composite
◦ Slower polymerization rate
◦ Internal flow, compensates for shrinkage
Soft-start cure - ¯ initial light intensity
◦ Decreased stress, disadv. - maybe ¯ conversion
Light-directed polymerization
◦ Composite does not shrink toward the light
Low shrinkage composite: Filtek LS 0.9% shrinkage ◦ Silorane resin, ring opening
154
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Bonding Agent
Primer/Adhesive Resin
◦ Resin matrix phase, unfilled
◦ Flows into etched dentin and enamel, micromechanical union
◦ Macro and micro resin tags, enamel
◦ 1-5 micron thick hybrid layer, dentin
◦ Co-polymerizes with the composite material
◦ Chemical union
155
Universal adhesives
| Chemistry game changer is
10-MDP Methacryloyoxy-decyl-dihydrogen-phosphate
156
skipped
| 10-MDP Methacryloyoxy-decyl-dihydrogen-phosphate (4)
Mechanism of action : A monomer that chemically interacts via ionic bonding to calcium in hydroxyapatite
Single bottle, no mix adhesive system
Can be used in total etch, self-etch or selective-etch mode (etch enamel only with phosphoric acid and rest of tooth with universal adhesive)
Monomer is a phosphate ester
