Dental Materials I Flashcards Preview

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Flashcards in Dental Materials I Deck (64):
1

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

Ceramics

2

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

Polymers

*acrylics, waxes, cements

3

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

Composites

4

What is the structure of enamel?

96% Hydroxyapatite

Ca10(PO4)6(OH)2

5

What 2 structural units make up enamel?

Cylindrical Enamel rods
Interrod enamel

6

What is found around the Enamel Rod?

Rod sheath

*narrow space delineating rod and interrod enamel
**keyhole shaped

7

What makes up the bulk of the Dentin?

Intertubular dentin

8

What is Intertubular Dentin made out of?

Collagen matrix embedded with hydroxyapatite

9

What lines the tubular walls in Dentin?

What is it made of?

Peritubular Dentin

Mostly hydroxyapatite crystals

10

T/F
Peritubular Dentin increases with age

True

11

What makes up 60% of Dentin?

Other 40%?

Intertubular dentin

Peritubular dentin

12

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

Covalent
Ionic
Metallic

13

What are the strongest and simplest atomic building blocks?

Covalent bonds

(shared electrons)

14

What are the concerns of Biological properties of materials?

Toxicity and Sensitivity rxns

*occur locally or systemically

15

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

Low Surface Energy

16

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

Wettability

17

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

Adsorption

18

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

High
Low

19

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

Absorption

20

What is the best and most expensive biocompatability test?

Usage tests

21

Where is material placed in a Usage Test?

Identical to clinical use
(in humans, etc)

22

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

Microleakage

23

What causes microleakage?

Gap between tooth and restoration

*influx irritates pulp

24

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

0.5mm

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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