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Biomaterials 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 biomaterial

A

Biomaterial

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2
Q

4 Major Classes of Dental Materials

A
  • Metals and Alloys
  • Porcelains and Ceramics
  • Polymers
  • Composites
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3
Q

Reclassified_______ from class I to class II

A

amalgam

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4
Q

Types of interatomic bonds:

Primary

A

Ionic, covalent, metallic

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5
Q

Types of interatomic bonds:

secondary

A

Hydrogen bonds, Van der Waals forces

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6
Q
  • Electrostatic attraction of positive and negative charges
  • Involves electron transfer between ions
  • Properties:
  • non-directional, strong bonds
    • 100-200kcal/mole
  • No free electrons, good thermal and electrical insulators

• Examples
- Ceramics, gypsum

A

Ionic

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7
Q

Valence electrons shared by 2 atoms

Properties
• Often directional bonds
• 50-100kcal/mole
• Low electrical and thermal conductivity
• Water insoluble

Examples:
Water, glass, polymers, composite

A

Covalent

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8
Q

Cluster of positive metal ions surrounded by a gas of electrons.

Properties
• Non-directional bonds
• 100 kcal/mole
• High electrical and thermal conductivity

Examples
• Amalgam and gold alloys

A

Metallic

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9
Q

Physical Properties
Depend on the type of _____ and
the bonding present in material

A

atoms

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10
Q

Quantity of heat passing through 1 cm thickness of material.

A

thermal conductivity

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11
Q

How quickly crown interior approaches temp of exterior

A

Thermal Diffusivity

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12
Q

Applied force referred to as _______.

A

load

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13
Q

When load (force) applied to material,_____ develops in response

A

STRESS

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14
Q

Strength of material= stress at______.

A

fracture

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15
Q

• Tensile • Compressive • Torsion • Shear • Flexure

A

Types of Force/Stress

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16
Q

Tensile Strength-_______ force

A

PULLING

lowest strength for most materials

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17
Q

Measure of the stress necessary to fracture a material by 2

opposing forces directed away from each other

A

Tensile Strength

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18
Q

Measure of the stress necessary to fracture a material by 2

opposing forces directed toward each other

A

Compressive Strength

Highest strength measure for most materials

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19
Q

Torsion Strength-______ force

A

TWISTING

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20
Q

Shear Strength-______ force

A

SLIDING

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21
Q

Stress necessary to rupture a material by 2 opposing

parallel forces directed toward each other but not in the same plane

A

Shear Strength

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22
Q

Flexural Strength-______ force

A

BENDING

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23
Q

Protrusive movement

A

Examples of DENTAL STRESS on the anterior teeth.

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24
Q

Posterior occlusion

A

Examples of DENTAL STRESS of chewing

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25
tripodized occlusal contacts allow:
minimal stress by distributing occlusal load across maximum area.
26
Premature Contact results in
OCCLUSAL STRESS IS INCREASED | and Potential restoration failure
27
The DEFORMATION that occurs in a material when force is | applied to the material
strain
28
______ and_____ are interrelated | • If you have one, you will have the other
Stress strain
29
The TEMPORARY distortion of a material by applied force. When force is removed, materials reverts to original form.
elastic strain
30
PERMANENT distortion of a material
PLASTIC Strain
31
Deformation BELOW the elastic limit
Elasticity
32
Plastic deformation (elongation) from tensile stress
Ductility
33
``` Plastic deformation (elongation) from COMPRESSIVE stress ```
Malleability
34
the quality of having minimal to no plastic deformation
Brittleness
35
The quality of stiffness of a material
Modulus of Elasticity
36
Energy absorbed to reach elastic limit
Resilience
37
Energy absorbed to cause fracture
Toughness
38
Mechanical properties of Ceramics
Strong, brittle, stiff
39
Mechanical properties of metal/alloy
Strong, stiff, some elasticity, ductile
40
Mechanical properties of dental composite
Weaker, brittle, lower elastic modulus
41
Mechanical properties of Elastomeric polymer
Weaker, lower elastic modulus, ductile
42
solid mixture of 2 or more metals
alloy
43
* Ag 40-74% * Sn 26-30% * Cu 2-30% * Zn 0-1%
Composition of alloy powder
44
• High copper content
12-30%
45
• Low copper content
2-6%
46
* More Hg needed to wet powder * More condensation pressure needed * ROUGHEST surface
Lathe cut of alloy
47
* Atomize liquid alloy into spheres * Less Hg needed to wet spheres * More plastic * Easier to achieve interproximal contact * SMOOTHEST surface
Spherical particles of alloy
48
* Combination of lathe and spherical * Better condensation properties * Hg 47-50% * Smoother than lathe
• Admixed
49
What is used at the school of dentistry?
• Admixed
50
* Gamma phase: Strong, hard * Gamma 1 phase: Brittle intermediate strength * Gamma 2 phase: weak, prone to corrosion, increased creep
Amalgam phases
51
With high copper content, what is increased and what is eliminated?
Increased strength and hardness the gamma phase II is eliminated.
52
• Too much= decreased strength • Problem ameliorated with pre-capsulated alloys
mercury content
53
• Under OR over triturated= decreased strength
Trituration
54
* Express excess Hg to surface= INCREASE strength • Minimize porosite * Adapt amalgam to cavity walls: 45 degree angle to walls * Condensation pressure: lathe cut requires most pressure, spherical requires least
Condensation technique
55
* Greater time elapsed, lower strength | * Discard amalgam not condensed within 3-4 minutes
Elapsed time between trituration and condensation
56
• Decrease density= decrease strength • Undertrituration • Improper or delayed condensation
Porosity
57
• 20 minutes= 6% of 1 week compressive strength • 8 hours=70% of 1-week strength • Caution patients to avoid heavy occlusion for first 8 hours
Hardening rate of amalgam: time after condensation
58
Time -temperature-strain relationship
CREEP
59
_____ correlated to marginal breakdown | • “ditched” margins
Creep
60
______ Cu amalgams= higher creep | • Conversely,_____ Cu amalgam= lower creep
Low high
61
* Formation of a surface layer * Oxide, sulfide, or chloride flim * GAIN of material
Tarnish
62
* Deterioration of metal by reaction with the environment * Electrochemical process: metal dissolution (pitting) * LOSS of material * Gamma 2 phase is most susceptible * Thus, low Cu alloys have higher corrosion susceptibility
Corrosion
63
* Occurs between dissimilar metal restorations contacting each other * Example: gold crown occluding with amalgam restoration * Gold is cathode, amalgam is anode * Amalgam loses material
• Galvanic Corrosion
64
``` Electric potential between dissimilar metals • Circuit closes when in occlusion • Results in pain • Resolves over time • Tarnish develops ```
Galvanic Shock
65
• Occurs are margins of amalgam restoration ADVANTAGE: • Corrosion seals margins-> decreased microleakage • Occurs more quickly with low Cu alloys
crevice corrosion
66
Average replacement age LOW Cu (no Zn):
5-10 years
67
Average replacement age HIGH Cu (with Zn):
14-25 years
68
* Easy to place * Less technique sensitive * More durable * Resistant to fracture * Not abrasive to opposing teeth
Amalgam advantages
69
* Esthetics * Does not bond to tooth * Subject to corrosion and tarnish * Marginal breakdown and microleakage
Amalgam disadvantages
70
T/F Amalgam is not free mercury
true
71
* Requires office to use amalgam separators • Prohibits flushing waste amalgam down the drain • Prohibits use of bleach or chlorine containing cleaners * May lead to dissolution of Hg from amalgam
• 2017 EPA ruling concerning dental practices

Operative (12 decks)

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