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Tim's Cards > Dental Materials I > Flashcards

Dental Materials I Flashcards

(64 cards)

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1
Q

What are chemically intimate mixtures of metallic and non-metallic elements which allow covalent or ionic bonding?
(includes dental porcelains, refractories)

A

Ceramics

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2
Q

What are long molecules composed of non-metallic elements and bonded covalently?

A

Polymers

*acrylics, waxes, cements

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3
Q

Physical mixtures of metals, ceramics, or polymers (including resins, ionomers, compomers, bonding agents, cements) are?

A

Composites

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4
Q

What is the structure of enamel?

A

96% Hydroxyapatite

Ca10(PO4)6(OH)2

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5
Q

What 2 structural units make up enamel?

A

Cylindrical Enamel rods

Interrod enamel

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6
Q

What is found around the Enamel Rod?

A

Rod sheath

  • narrow space delineating rod and interrod enamel
  • *keyhole shaped
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7
Q

What makes up the bulk of the Dentin?

A

Intertubular dentin

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8
Q

What is Intertubular Dentin made out of?

A

Collagen matrix embedded with hydroxyapatite

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9
Q

What lines the tubular walls in Dentin?

What is it made of?

A

Peritubular Dentin

Mostly hydroxyapatite crystals

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10
Q

T/F

Peritubular Dentin increases with age

A

True

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11
Q

What makes up 60% of Dentin?

Other 40%?

A

Intertubular dentin

Peritubular dentin

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12
Q

What are the 3 types of Primary bonds that serve as building blocks in dental materials?

A

Covalent
Ionic
Metallic

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13
Q

What are the strongest and simplest atomic building blocks?

A

Covalent bonds

shared electrons

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14
Q

What are the concerns of Biological properties of materials?

A

Toxicity and Sensitivity rxns

*occur locally or systemically

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15
Q

What type of liquid will readily spread over a high surface energy substrate?

A

Low Surface Energy

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16
Q

What is the measure of the affinity of a liquid for a solid as indicated by the spreading of a drop?

A

Wettability

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17
Q

The ability of a dissimilar substance to adhere to the surface of a solid is know as…

A

Adsorption

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18
Q

____ energy surfaces will adsorb molecules more readily than ____ energy surfaces.

A

High

Low

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19
Q

The diffusion of liquid into the solid material is known as…

A

Absorption

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20
Q

What is the best and most expensive biocompatability test?

A

Usage tests

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21
Q

Where is material placed in a Usage Test?

A

Identical to clinical use

in humans, etc

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22
Q

What may happen if a material doesn’t bond with sufficient strength to resist contraction upon polymerization, wear, or thermal cycling?

A

Microleakage

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23
Q

What causes microleakage?

A

Gap between tooth and restoration

*influx irritates pulp

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24
Q

What is the RDT - Remaining Dental Thickness minimum requirement for pulp protection?

A

0.5mm

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25
How is Stress calculated?
Ratio of force per area
26
Name 5 types of stress.
``` Tension Compression Shear Torsion Bending ```
27
What is the definition of Strain?
Deformation caused by stress
28
What does the highest linear portion of a Stress Strain curve delineate?
Proportional Limit
29
What is the greatest stress sustained without permanent deformation?
Elastic Limit
30
What is the difference between Elastic and Plastic deformation?
Elastic is Non-permanent Plastic rearranges molecules and is Permanent
31
The point on a stress strain curve at which material is no longer elastic and is being displaced in a plastic manner is called?
Yield Strength
32
What amount of permanent strain defines Yield Strength?
0. 2% | - totally arbitrary
33
How can permanent deformation of dental material be bad? | Be good?
Filling moves - bad occlusion Orthodontic wires bent - better movement
34
Where does Ultimate Strength occur on the Stress Strain graph?
At the top *this is max stress
35
What defines the stress at which material fractures?
Fracture strength
36
T/F | Fracture strength and Ultimate strength are the same thing.
False
37
What is the deformation that results from the application of tensile stress?
Elongation *expressed in %
38
A steep slope in the Stress Strain graph suggests:
High rigidity High Elastic Modulus (E)
39
Elastic Modulus =
Stress / Strain
40
A flat slope, or a low Elastic Modulus indicates...
Flexibility
41
The higher the value of E, the ______ the material.
More rigid
42
How is Resilience measured?
Area under Elastic portion of Stress-Strain graph
43
How is Toughness measured?
Area under Elastic and Plastic portions of graph
44
What does Fracture Toughness refer to?
Toughness of materials with defects, cracks, or flaws
45
What materials are generally weakened by fractures?
Brittle
46
How is tensile stress measured in brittle materials?
Diametral Compression Test
47
Why will brittle materials have a short non-linear portion in a Stress-Strain graph?
The plastic response is small *fractures
48
T/F | Material can't be tough and brittle
True
49
``` Stress Strain graph for the following: Stiff Ductile Strong Tough ```
Lecture 2 Slide 30
50
Stress Strain graph Stipp Brittle Strong
2;30
51
Stress Strain graph Stiff Ductile Weak
2;30
52
Stress Strain graph Stiff Brittle Weak
2;30
53
``` Stress Strain graph Flexible Ductile Strong Resilient ```
2;30
54
``` Stress Strain graph Flexible Brittle Strong Resilient ```
2;30
55
Stress Strain graph Flexible Ductile Weak
2;30
56
Stress Strain graph Flexible Brittle Weak
2;30
57
Something breaks after repeated loading is known as...
Fatigue Strength
58
If a material can be loaded an infinite number of times without failing, this is known as...
Endurance Limit
59
How fast something is loaded is known as...
Rate of Loading *important for dentures
60
A material that is independent of loading rate is...
Elastic
61
Materials dependent on Loading Rate are know as...
Viscoelastic
62
What is the resistance of a fluid to flow?
Viscosity
63
What is the increase in strain of a material under constant stress?
Creep
64
What is important for polymers in thin sections and is dependent on the loading rate?
Tear Strength

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