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Flashcards in Dental Materials Deck (293)
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61

What are the 2 types of lab research?

1. In vitro
2. In vivo

62

What 5 basic factors are tested in in-vitro testing?

1. Physico-mechanical properties
2. Biological properties: cytotoxicity; organ, tissue, cell cultures
3. Genotoxicity: damage to genetic info causing mutations
4. Oestrogenic activity
5. Basic sciences: efficacy and safety of therapeutic, rehabilitative, preventative regimes

63

What kind of tests are done in-vivo?

Implants: material implanted into animal
Allergy tests
Limited usage studies: animal/clinical testing; long, tedious but most clinically relevant

64

What types of animal tests are there?

Past: material ground and fed to animal; implanted into animal
Now: material used in required area

65

Why is clinical testing preferred?

Most accurate and efficacious depending on:
Number of patients
Group of patients
Length of trial

66

What is the downfall of clinical testing?

Clinical symptoms don't evaluate real world damage
Will have material in OC for years not weeks

67

What are some of the ways in which post-market surveillance is important?

Provide early warning signs of unsuspected adverse effects
Elicit predisposing factors to adverse reactions
Compare adverse reactions between similar products
Permit continued safety monitoring

68

Who are at risk of adverse reactions from DMs?

Dentist
Dental nurse
Dentinal technician
Patient

69

Who is most at risk of adverse reactions to DMs? Why?

Dentist/technician
Inc. risk as inc. exposure to material

70

How can risks be reduced?

Proper packaging
Following manufactures instructions
Non-contact operative techniques

71

What are the 3 main types of force?

1. Uniaxial
2. Biaxial
3. Triaxial

72

What are the 3 types of uniaxial force?

1. Tensile: away from each other
2. Compressive: towards each other
3. Shear: towards, one from top side other from bottom side

73

What are forces defined by?

Where they are applied, in what direction and how big they are

74

What is stress?

Force applied per unit area

75

Define strain

Deformation of object due to stress

76

What is Hooke's law?

Stress is proportional to strain

77

What is Young's modulus?

Ratio of stress to strain i.e. stress/strain is a pressure (Pa)

78

What can be determined from a stress-strain curve?

Ductility, strength, elastic modulus, resilience, toughness, flexibility

79

What is a fracture?

Separation of a material into 2+ pieces under action of stress

80

What are the 2 types of fracture?

Brittle: little/no plastic deformation, low toughness
Ductile: significant plastic deformation, high toughness

81

What are the steps in a fractureb

1. Crack formation
2. Crack propagation

82

Describe the stress-strain plot for a brittle material

Almost linear due to low plastic deformation

83

Describe a direct tensile measurement

Dumbbell shaped test specimens, ensures central fracture

Used for metals, rigid polymers, rubbery polymers

84

What are compressive tests used for?

Ceramics
Hard polymers

85

What is a diametral/indirect tensile test?

Compression across diameter

86

What are the 6 static strengths?

1. Compressive
2. Tensile
3. Shear
4. Torsion
5. Flexure
6. Diametral tensile

87

What is hardness?

Resistance to indentation/permanent deformation when compressive force applied

88

What is fracture toughness?

Resistance of a material to failure from fracture starting at pre-existing crack

89

Define tear strength and energy

Strength: force needed to initiate/continue tearing
Energy: measure of energy per unit area of newly torn surface

90

Define impact

Resistance to fracture from rapid loading measured as energy absorbed at fracture