Test 1 Flashcards
(114 cards)
1
Q
measured as gloss or percent reflection
A
Reflection
2
Q
measured as percentage for every wavelength
A
Absorbtion, Transmission
3
Q
change in direction of light due to a change in medium
A
Refraction
4
Q
light reflection in all directions
A
Scattering
5
Q
prevents passage of light
A
Opaque
6
Q
allows passage of light with little distortion
A
Transparent
7
Q
permits passage of light but disperses the light so that objects cannot be seen through
A
Translucent
8
Q
Color System: Wavelength
A
Hue
9
Q
Color System: Value
A
Black and white
10
Q
Color System: Chroma
A
Purity/ Saturation
11
Q
transmission of light by a substance that has absorbed light or other radiation
A
Fluorescence
12
Q
the force of attraction exerted on surface molecules of a liquid by the molecules beneath the surface
A
Surface tension
13
Q
atoms on solid surfaces have higher energy than the atoms in the bulk of a material
A
Surface Energy
14
Q
The adhesion of a molecule to a surface
A
Adsorption
15
Q
Involves the substance diffuses into the solid material
A
Absorption
16
Q
Hydrophillic, Low surface energy
A
Good Wetting
17
Q
Hydrophobic, High Surface energy
A
Poor Wetting
18
Q
Bonding agents and cements, Impression material need what type of wetting
A
Good Wetting- to replicate surface texture
19
Q
Composite restorations, crown materials, denture bases need what type of wetting
A
Poor Wetting- Repel bacteria and hinder biofilm formation
20
Q
Two metals that have high thermal conductivity
A
Gold, Copper
21
Q
The metal that has the lowest thermal conductivity
A
Amalgam
22
Q
Three non metals with low thermal conductivity
A
Gypsum, Porcelin, Composite Resin
23
Q
why do dental ceramics not use Koalin?
A
Because it adds opaque character and teeth are naturally fluourecent
24
Q
Consequences of metallic bonding?
A
is more thermally conductive
25
Why do we use alloys in mouth
they are stronger and more malleable unlike gold which can compress
26
Synthetic materials for use in the body
biomaterials
27
The property of a material to conduct heat
Thermal Conductivity
28
List metals in closest proximity to enamel in thermal conductivity
Amalgam, gold copper
29
List non metals in closest proximity to enamel in thermal conductivity
Porcelain, Resin composite and Gypsum
30
Due to thermal conductivity of most metals what is needed when a amalgam or gold crown is placed on a tooth
Thermal insulator- or a non metal
31
Heat needed to raise temperature 1 degree
specific heat
32
A measure of how quickly one reaches thermal equilibrium when exposed to temperature change
Thermal diffusivity
33
Relative change in dimension in response to temperature change
Coefficient of thermal expansion
34
Which material has closest coefficient of thermal expansion to enamel
Gold
35
What other materials have a close coefficient of thermal expansion to enamel
amalgam and resin composite
36
What materials have a coefficient of thermal expansion that is far from enamel
Silicon material, sealants, acrylic resin
37
Large differences in thermal expansion can cause
mechanical stress and sensitivity
38
Atoms that are situated in a repeating array over large distance 3-D shape
Crystalline Materials
39
Which materials have a crystalline structure
all metals, many ceramics, and certain polymers
40
atoms that lack a systematic and regular arrangement
Non-crystalline or Amorphous material
41
What materials have non crystalline structure
glass and some polymers
42
what is 3-D array of points coinciding with the sphere centers
Lattice
43
What are three basic crystal structures
Body centered Cubic, Face Centered Cubic and hexagonal closed package
44
How are imperfections introduced on materials
solidification, rapid cooling and heating, mechanical force, thermal stress
45
What are the three classifications of imperfections
point defects, Substitutional impurity, edge dislocation
46
imperfections in one or two atomic positions
point defects
47
One dimentional linear defects (dislocations)
Substitutional impurity
48
Two dimensional grain boundary distortion
Edge dislocation
49
materials composed of many small crystals
Polycrystalline
50
The boundary separating two crystals having different crystallographic orientation
Grain boundary
51
an area with high energy, chemically reactive and segregate impurities is call what
Grain boundary
52
Combination of two or more materials
Composite
53
Mixture of metallic elements at the atomic level
Alloy
54
What are four consequences to metallic bonding? good and bad
Thermal and electrical conductivity, Opacity of light, Strength, ductility, malleability, ability to form alloys
55
why are pure metals not usually used in dentistry
too soft and ductile
56
What can give harder materials instead of metals and is a mixture of metals that is formed by a liquid state first that is then allowed to cool
Alloy
57
A structurally homogeneous part of the system but has separate physical boundaries
Phase
58
a mixture of elements at the atomic level where one molecule replaces the other
Substitutional solid solution
59
a mixture of elements at the atomic level where one molecule fits in between the other
Interstitial solid solution
60
what is a mixture of elements with specific composition of stoichiometric ratio and give an example in dentistry
Intermatallic compound--amalgam
61
Tooth enamel is what type of material
bioceramic
62
compounds of metallic and non-metallic elements, frequently oxides, nitrides carbides
ceramics
63
what bonds predominantly make up ceramics
ionic bonds
64
Can ceramics be crystalline or amorphous, give and example of an amorphous ceramic
yes, glass is an amorphous ceramic
65
What is the structure of ceramics
crystalline two-layered sheet structure of aluminosilicates
66
What is an example of polymorphic crystalline ceramic forms
quartz
67
What is an example of non-crystalline ceramic form
silica glass
68
What dental porcelain (ceramic) is opaque
kaolin
69
What is a mixture of potassium aluminosilicate and sodium aluminosilicate
Feldspar
70
Dental porcelain is made predominately from what
Feldspar and quartz
71
Give 2 reasons ceramics are better than metals
Ceramics are chemically stable because of their oxidized state, more inert, they are insulators that can resis high temp
72
What materials are prone to corrosion that ceramics are not
Metals and alloys
73
What is the most common polymer in dentistry
gutta percha
74
What is a long chain molecule of repeating units, Carbons and hydrogens
polymer
75
Give 4 examples of natural polymer compounds
proteins, rubber, gutta percha and wax
76
Give 3 examples of synthetic polymer compounds
plastic, silicon, and acrylic
77
Give 4 dental applications of polymers
acrylic denture base, dental sealants, dental composite (bisGMA), dental adhesives
78
the ability of a structure to resist deflection when forces are applied
Stiffness
79
the ability to resist fracture when a structure is loaded or a material is stressed
Strength
80
how forces are distributed in a material, defined as force over area
Stress
81
relative deformation of a material, defined as the change in length divided by the original length.
Strain
82
reversible deformation
Elastic deformation
83
irreversible (permanent) deformation
Plastic deformation
84
a material that exhibits extensive plastic deformation before it break
ductile
85
a material that exhibits little or no plastic deformation before it breaks
brittle
86
failure of a structure or material that results in separation
fracture
87
area under the elastic portion of the stress-strain curve, which represents the energy needed to deform a material to the proportional limit
resilience
88
area under the elastic and plastic portion of the stress-strain curve, which represents the energy needed to cause fracture.
toughness
89
sensitivity of a material to cracks or flaws
fracture toughness
90
failure caused by repetitive or cyclic loading at loads that are lower than the ultimate strength of a structure or material.
fatigue
91
resistance of a material to gradual shear or tensile stresses. Used to describe how well a material flows
viscosity
92
stress-strain properties depend on how fast the stress or strain is applied, a material that has both elastic and viscous properties during deformation
viscoelastic
93
a solid material’s resistance to permanent surface deformation, calculated from indentation dimensions
hardness
94
maximum deformation (stretching) as a result of a tensile force
elongation
95
the relationship between stress and elastic strain and can be defined as the stress/ strain
Elastic modulus
96
The change in thickness due to elongation when a material is under stress is called
Poissons ratio
97
occurs when forces or stresses are directed in opposite direction
tension
98
occurs when forces or stresses are directed towards each other,
compression
99
occurs when coplanar forces or stresses are parallel but directed in opposite direction
shear
100
when forces cause rotational distortion in a structure or material
torsion
101
ultimate stress under tensile stress
tensile strength
102
ultimate stress under compressive stress
compressive strength
103
the ultimate strength of a cylindrical specimen where a compressive load causes tensile stresses
diametral tensile strength
104
compressive stresses at the upper side of the beam tensile stresses at the under side of the beam
flexural strength
105
under constant strain, stress decreases over time which viscoelastic strain
stress relaxation
106
under constant stress, strain increases over time, which viscoelastic strain
creep
107
In dental materials, creep is used to describe which time dependent property of the material
Viscoelastic strain
108
Viscosity is measured by applying
shear strain
109
Measure of how quickly thermal gradients build up in a material if heat is applied for only a short time is called
Thermal conductivity
110
stress is defined as
force/area
111
ionic bonding with a electron cloud is called
metallic bonding
112
the relative amount of deformation that a material undergoes while under stress is
strain
113
polymers are examples of materials that have
neither long nor short range order
114
what has the highest value of thermal expansion
wax
