Test 1 Flashcards
1
Q
What are the qualities of metals?
A
High thermal and electrical conductivity Ductility Opacity Luster Atoms in regular or crystalline arrangement High atomic bond strength
2
Q
What are the components of a crystalline arrangement?
A
Regular arrangement
Liquid to solid
3 spatial dimensions
3
Q
What are the qualities of ceramics/porcelain?
A
Combination of kaolin, feldspar, and quarts.
Used to fabricate inlays, onlays, crowns, bridges and veneers.
Generally very brittle.
High melting point.
Low thermal and electrical conductivity.
Not very chemically reactive
4
Q
Define thermoplastic
A
molded without chemical reaction taking place; change takes place with temperature changes
5
Q
Define thermosetting
A
chemical change takes place during molding
6
Q
Define monomer
A
any small organic molecule that can be bound to similar molecules to form a polymer
7
Q
Define polymer
A
material composed of many repeating units called monomers.
Plastics: synthetic
Rubber: natural
8
Q
Define polymerization
A
the conversion of low-molecular weight compounds (monomers) to high-molecular weight compounds (polymers)
9
Q
Define copolymer
A
contains two or more different monomers
10
Q
Define cross-linking agent
A
network of adjacent polymer chains. Increases the resulting polymer stronger
11
Q
Define Composite or composite resin
A
a dimethacrylic acid polymer material that is heavily filled and used for direct restorations, veneers, inlays, cementation and sealants.
12
Q
True or False: Composite is the same material as resin
A
True: they are the same material but composite has more fillers which increases the strength.
13
Q
What is galvanic response?
A
the coupling of two dissimilar metals. (i.e. gold vs. amalgam)
14
Q
What is thermal conductivity?
A
the rate at which heat flows through a material.
15
Q
What is solubility?
A
Ability to dissolve in liquid.
The liquid in which a substance dissolves is a solvent.
16
Q
What is sorption/absorption?
A
The uptake of fluids into a solid.
This can be helpful or detrimental.
Detrimental when restorations or cements deteriorate.
17
Q
What is the primary molecular interaction of composite?
A
result of forming chemical bonds.
systems based on polyacrylic acid.
i.e. Zinc polycarboxylate cements, glass ionomer
18
Q
What is the secondary molecular interaction of composite?
A
physical forces with no chemical union. this is the most common type
19
Q
What is the wetting angle?
A
the angle that is measured through the liquid, at which a liquid interface meets a solid surface.
How well a liquid covers the surface of a solid.
20
Q
What is a high contact (wetting) angle?
A
less of surface is covered
21
Q
What is a low contact (wetting) angle?
A
more of surface is covered
good adhesive has contact angle that approaches zero
22
Q
What are some examples of materials that have lower wetting angles?
A
Wetting impression material.
Bonding agent
23
Q
What is disintegration?
A
breaking up of a solid
end process of fluid and material interactions
all dental materials are place in a fluid environment
24
Q
What is adhesion?
A
Means of attaching two solids together.
Force of attraction between molecules or atoms on two different surfaces.
25
What is cohesion?
Force attracting molecules within a given material. A force that causes like to attach to one another
26
What is hue?
considered color name. The hue of natural teeth is yellow.
27
What is value?
The lightness or darkness of a color or hue
| 1=black, 2=white
28
What is chroma?
the vividness or strength of a color or hue
29
What is translucency?
Refers to the way light is affected when entering a substance
Transparent: permits light to pass through.
Opaque: absorbs all of the light.
30
What is metamerism?
colors that look different under different light sources.
31
What is fluorescence?
the emission of previously absorbed energy as light at a different wavelength. Property of some materials to emit light radiation, usually ultraviolet.
32
What is corrosion?
Deterioration of a metal by a chemical or electrochemical reaction.
Pitting!
Saliva acts as a conducting medium between metal materials
33
What is tarnish?
deterioration involves only the surface resulting in discoloration.
34
What is stress?
the amount of force applied to a specific area.
| Stress=force/area
35
Define strain.
Internal rearrangement of atoms to adjust to the stress.
Deformation is a change in shape that results from strain.
Strain=deformation/length
36
What is tensile?
forces on an object directed away from each other.
stretched or elongated
the ability of a material to resist pulling
37
Define compressive.
Resistance in the material to the external force.
| Ability to resist pushing.
38
Define shear.
ability to resist tearing-forces directed parallel to each other. (scissors)
39
What is elastic limit?
Measures the stiffness of a material
maximum stress without permanent deformation
material cannot regain its size and or shape
Proportional limit is used interchangeably with elastic limit*
40
Compression
denting
41
Tension
stretching
42
Shearing
bending
43
Torsion
twisting
44
What is ultimate strength?
the point just before fracture
45
What is ductility?
ability of a material to be drawn into a wire.
ductility=elongation
low ductility=brittleness
46
What is malleability?
ability to be hammered or rolled into thin sheets without fracture-compression
47
What is resilience?
The energy necessary to cause permanent deformation
48
What is toughness?
the ability of material to resist fracture
49
Define creep.
Gradual permanent change in dimension that occurs in an object due to constant loading.
Flow after set (amalgam)
50
Define Viscosity.
resistance of material to flow
51
What is thixotropic?
some materials have a high viscosity, but change with pressure (mixing).
i.e. impression material
52
What is rockwell hardness?
the depth of an indentation made with a steel ball.
i.e. composites
(vertically)
53
What is Knoop hardness?
measuring the length of a diagonal made with a diamond indenter.
i.e. metals and porcelain
(horizontally)
54
Define fatigue.
Created by the repeated application of stress to an object causing tiny cracks to be generated within the structure until failure occurs.
*Stress=force applied to a specific area
55
Mouthguards are made of what material?
Flexible polymer sheets
56
What is a splint used for?
more rigid than mouth guards
used to distribute biting or grinding forces to prevent injury to teeth, alveolar bone or TMJ
rigid cover over maxillary teeth
57
What is a periodontal splint for?
used to transfer forces to adjacent teeth allowing compromised tooth support.
Made of wire,mesh, metal or plastic
58
Describe temporary restorations.
designed to be placed on a tooth for limited time
maintain integrity and function of dentition
protect tooth from oral environment and mastication forces
59
What materials are used in temporary restorations?
Acrylic resin-these are exothermic (give off heat)
composite
synthetic resins
60
Define resin
a class of solid or soft organic compounds of natural or synthetic origin. High molecular weight, most are polymers.
i.e. polyvinyl, polyethylene, polystyrene.
Combined with chemicals to form plastics
61
Define synthetic
made by chemical synthesis, which is combining of elements into a whole
62
Zinc Oxide Eugenol
ZOE.
consists of zinc oxide particles, additive and eugenol (oil of cloves)
eugenol is acidic, can irritate pulp, but also stimulated secondary dent which insulates pulp.
Cannot be used under composite materials, inhibits polymerization.
Has sedative effects
i.e. IRM
63
What is a base used for?
thick material
absorb biting forces
thermal insulation
irritation to stimulate secondary dentin
64
The current belief on bases is...
pulpal sensitivity is caused by micro-leakage not temperature change.
Bond material is now preferred which eliminates micro-leakage
65
True or False. Only certain dental cements can be used as bases.
False. Any dental cement can be used as a base.
66
Why can't ZOE be used under composite restorations?
it inhibits polymerization.
67
What is zinc phosphate?
exothermic base.
initial set is very acidic
Not recommended in deep cavity prep unless calcium hydroxide is placed first to protect the pulp.
one of the oldest of cements-rarely used as base
68
What is polycarboxylate?
base, acidic but pH rises with time, kinder to pulp
| can be placed under all restorations but is generally used under amalgam
69
What is the primary use of polycarboxylate?
cement
70
What is a glass ionomer?
most popular base: strength, bonding, fluoride, non-irritating, anticariogenic
bonds to dentin and releases fluoride
Because it is a polymer, it bonds to other polymer materials used in restorations
71
What are some of the advantages of glass ionomer?
reduces microleakage because of bonding
can be used under all restorations
self and light cured
dual cure
72
What are the components of acrylic resin?
acrylic acid polymer bonding agent
bonds to both enamel and dentin
resin cements are basically fluid composites-less fillers
73
When do you use ZOE?
when restoration will be temporary
74
When do you use calcium hydroxide?
for a deep preparation
75
When do you use acrylic resin/glass ionomer?
as a bonding agent under esthetic polymers, composite, glass ionomer, and their hybrids
76
What is a varnish?
used to seal cut dentin. it dissolves slowly in oral fluids and is not permanent
it is being replaced with bonding agents
*used only under amalgam-newer amalgams do not corrode as fast, older amalgams corroded faster and sealed microleakage
77
What is a liner used for?
to seal dentin and medicate pulp
78
Describe calcium hydroxide.
```
has a basic pH
readily dissolves in oral fluids
it neutralized the pH
decreased bacterial growth
promotes secondary dentin
placed in deepest part of restoration
being replaced by bonding material that is not soluble and does not weaken tooth
```
79
Review of base.
absorbs biting forces and insulates the pulp from temperature changes.
80
Review of varnish.
Seals cut dentin tubules
81
Review of liners.
reduces acidity, stimulates pulp and is a bonding material
82
When are glass ionomers used?
direct restorations, core buildups, sealants, bonding agent
83
What is a blend?
a combination of composite and glass ionomer
84
What is a compomer?
hybrid of composites and glass ionomer cements. also a blend
85
What is polyacid modified glass ionomer?
more glass ionomer than composite. blend.
86
What is polyacid modified resin composite?
more composite than glass ionomer. blend
87
Composites, glass ionomers and blends are all...
polymers with reinforcing particles locked in the polymer framework.
88
Polymethyl/methacrylate, or PMMA is...
a polymer made up of multiple methacrylate monomers.
89
What are dimethacrylate resins?
most popular in dentistry.
reaction between bisphenol-A and glycidyl methacrylate=Bis-GMA
cross linked polymer
increased stiffness and strength and lower water absorption
less shrinkage
90
What is triethylenglycol dimethacryate?
dimethacrylate
| reduces viscosity
91
What are some filler particles in composites?
Silicates (quartz)
Radiopaque materials
silane
92
How are composites classified?
by filler size
93
What are the three composite filler size classifications?
macrofill 10-20 microns (marshmallows)
midifill .1-1 microns (jelly beans)
microfill .01-.1 microns (nerds)
94
How are composites polymerized?
chemically activated
| light activated-increases heat, increased kinetic energy
95
What is a smear layer?
compacted debris on enamel or dentin from cavity prep
| this limits bonding strength and is removed by etching
96
Describe amalgam.
alloy containing mercury
| mercury is only pure metal that is liquid at room temperature
97
What is an alloy?
mixture of 2 or more metallic substances.
98
What are amalgams classified as?
composition: high or low copper
| and particle size
99
What is the composition of amalgam?
```
mercury-Hg
Silver-Ag
tin-Sn
Copper-Cu
Zinc-Zn (may or may not have zinc)
```
100
What are some properties of amalgam restorations?
```
load bearing restorations for posterior teeth
pin-retained
retrograde canal filling material
root surface restoration
inexpensive
```
101
Property of zinc in amalgam?
zinc is not always present
it adds plasticity, makes it easier to condense
if it is contaminated by moisture there is an uncontrolled over enlargement of the amalgam
102
What are the properties of copper in amalgam?
it increases strength, hardness, controlled setting expansion and corrosion resistance.
Majority of alloys today are high copper content.
103
Is an amalgam with a high copper content or low copper content better?
high copper content
104
What is gamma 2?
not a good thing!
reaction with Tin and mercury
responsible for negative characteristics of lower copper amalgam
weakest phase
105
What are advantages of high copper amalgam?
silver and mercury=gamma 1
this is the most common reaction
more gamma 1 then stronger alloy
106
Describe lathe cut amalgam.
grinding a solid metal alloy bar on a lathe. rough irregular filings of various sizes
107
Describe spherical alloys.
made by spraying molten alloy into a vacuum and letting the drops fall. As drops fall they become round balls
108
Describe admixed alloys.
contain both lathe cut and spherical particles.
| BEST
109
What is the common particle size for most alloys today?
spherical or admixed. spherical particles reinforce structure due to regular shape, can be packed closer together
110
What are some advantages of amalgam?
easy to insert
not overly technique sensitive
adequately resists fracture
reasonably long service life
111
What are some disadvantages of amalgam?
```
poor color match
subject to corrosion, tarnish and galvanic shock
eventually shows marginal breakdown
creep-leads to open margins or fractures
high thermal conductivity
```
112
Describe creep
creep causes amalgam to flow and the unsupported amalgam protrudes away from margins.
causes a ditch around margins
113
What are the components of ceramics?
Kaolin (clay found on riverbanks)
Feldspar and Quartz
Metallic oxides (pigment)
114
What are the differences between ceramics and porcelain?
porcelain is fired at high temperatures
| ceramic is cast or machine milled
115
Define fusion temperature.
temperature at which grains of porcelain powder fuse to form a ceramic mass
116
Define glaze.
creates smooth, translucent surface similar to enamel in appearance
117
What are some properties of ceramics?
excellent electrical and thermal insulator
low thermal expansion
low tensile strength
high compressive strength
118
Describe CAD CAM
computers used to design and cut ceramic restorations
| less wear on opposing enamel (ceramic)
119
What are veneers?
a thin layer of tooth-colored material cemented or bonded to the facial surface of a natural or replacement tooth to improve its appearance
120
What are the two types of veneers?
direct composite veneer
| indirect composite veneer (made in lab)
121
What are some chemical/mechanical precautions with porcelain?
needs to be protected from APF or other acids
| can be scratched
122
True or False. The lower the reactivity of a metal, the higher its nobility.
true
123
What are noble alloys?
combine larger amounts of precious metals with smaller amounts of base metals to create strong, hard, mixtures that are highly resistant to tarnish and corrosion. more expensive
124
Describe gold restorations
soft, contributes to color, tarnish and corrosion resistant, malleable and ductility
125
Describe copper restorations
lowers melting temp, contributes to hardness, strength and corrosion resistance
126
Describe silver in restorations
neutralized reddish color from copper, contributes to hardness and strength
127
Describe platinum in restorations
increases strength and melting temp, is white
128
Describe palladium in restorations
less expensive than platinum, same purpose. also white
129
What are the base metal alloys?
```
titanium
nickel/chromium
nickel/cobalt
molybdenum
tungsten
```
130
Describe characteristics of nickel/chromium.
not used as often now due to nickel allergies
| casting metal substructure for PFM crowns/bridges
131
What is a karat?
parts of pure gold in 24 parts:
100% gold = 24 karat
75% gold= 18 karat
132
Describe fineness
parts of pure gold in 1000 parts of alloy:
100% gold=1000 fineness
75% gold= 750 fineness
133
How many types of gold are there?
4
134
Describe type 1 gold.
soft, used for simple inlays
135
Describe type 2 gold.
medium, used for 2-3 surface inlays and onlays
136
Describe type 3 gold.
hard, crown and bridge
137
describe type 4 gold.
extra hard, partial dentures
138
What is a bridge?
an indirect restoration that replaces one or more missing teeth and is cemented or bonded in position
139
What is a pontic?
replacement tooth on a bridge
140
What is a maryland bridge?
bridge bonded to adjacent teeth
141
What is a cantilevered bridge?
bridge that has a pontic on either or both sides
