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Tim's Cards > Dental Materials I > Flashcards

Dental Materials I Flashcards

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
Q

How is Stress calculated?

A

Ratio of force per area

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26
Q

Name 5 types of stress.

A 
Tension 
Compression
Shear 
Torsion
Bending
27
Q

What is the definition of Strain?

A

Deformation caused by stress

28
Q

What does the highest linear portion of a Stress Strain curve delineate?

A

Proportional Limit

29
Q

What is the greatest stress sustained without permanent deformation?

A

Elastic Limit

30
Q

What is the difference between Elastic and Plastic deformation?

A

Elastic is Non-permanent

Plastic rearranges molecules and is Permanent

31
Q

The point on a stress strain curve at which material is no longer elastic and is being displaced in a plastic manner is called?

A

Yield Strength

32
Q

What amount of permanent strain defines Yield Strength?

A
  1. 2%

- totally arbitrary

33
Q

How can permanent deformation of dental material be bad?

Be good?

A

Filling moves - bad occlusion

Orthodontic wires bent - better movement

34
Q

Where does Ultimate Strength occur on the Stress Strain graph?

A

At the top

*this is max stress

35
Q

What defines the stress at which material fractures?

A

Fracture strength

36
Q

T/F

Fracture strength and Ultimate strength are the same thing.

A

False

37
Q

What is the deformation that results from the application of tensile stress?

A

Elongation

*expressed in %

38
Q

A steep slope in the Stress Strain graph suggests:

A

High rigidity

High Elastic Modulus (E)

39
Q

Elastic Modulus =

A

Stress / Strain

40
Q

A flat slope, or a low Elastic Modulus indicates…

A

Flexibility

41
Q

The higher the value of E, the ______ the material.

A

More rigid

42
Q

How is Resilience measured?

A

Area under Elastic portion of Stress-Strain graph

43
Q

How is Toughness measured?

A

Area under Elastic and Plastic portions of graph

44
Q

What does Fracture Toughness refer to?

A

Toughness of materials with defects, cracks, or flaws

45
Q

What materials are generally weakened by fractures?

A

Brittle

46
Q

How is tensile stress measured in brittle materials?

A

Diametral Compression Test

47
Q

Why will brittle materials have a short non-linear portion in a Stress-Strain graph?

A

The plastic response is small

*fractures

48
Q

T/F

Material can’t be tough and brittle

A

True

49
Q 
Stress Strain graph for the following:
Stiff
Ductile
Strong 
Tough
A

Lecture 2 Slide 30

50
Q

Stress Strain graph
Stipp
Brittle
Strong

A

2;30

51
Q

Stress Strain graph
Stiff
Ductile
Weak

A

2;30

52
Q

Stress Strain graph
Stiff
Brittle
Weak

A

2;30

53
Q 
Stress Strain graph
Flexible
Ductile
Strong
Resilient
A

2;30

54
Q 
Stress Strain graph
Flexible
Brittle
Strong
Resilient
A

2;30

55
Q

Stress Strain graph
Flexible
Ductile
Weak

A

2;30

56
Q

Stress Strain graph
Flexible
Brittle
Weak

A

2;30

57
Q

Something breaks after repeated loading is known as…

A

Fatigue Strength

58
Q

If a material can be loaded an infinite number of times without failing, this is known as…

A

Endurance Limit

59
Q

How fast something is loaded is known as…

A

Rate of Loading

*important for dentures

60
Q

A material that is independent of loading rate is…

A

Elastic

61
Q

Materials dependent on Loading Rate are know as…

A

Viscoelastic

62
Q

What is the resistance of a fluid to flow?

A

Viscosity

63
Q

What is the increase in strain of a material under constant stress?

A

Creep

64
Q

What is important for polymers in thin sections and is dependent on the loading rate?

A

Tear Strength

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