Focused Quiz: 10/27 Flashcards
1
Q
Lower contact angle, higher or lower hydrophilicity?
A
higher
2
Q
Property important in order to get sub-gingival details:
A
tear strength
3
Q
This property tells about the rigidity of the material:
A
strain in compression
4
Q
Material usually used for final impressions, dimensionally stable:
A
VPS
5
Q
Inelastic materials:
A
plaster, compound, waxes, ZnO-eugenol
6
Q
Aqueous hydrocolloids:
A
Agar (reversible) and Alginate (irreversible)
7
Q
Non-aquesous elastomers:
A
polysulfide, silicone, polyether
8
Q
types of silicone:
A
addition, condensation
9
Q
Colloid:
A
microscopically, uniformly dispersed throughout another substance
10
Q
2 phases of colloidal system:
A
dispersion (solvent?), dispersed (solute?)
11
Q
All hydrocolloids have this as the dispersion phase:
A
water
12
Q
First elastomeric IM:
A
agar (reversible hydrocolloid)
13
Q
Agar, organic or inorganic?
A
organic
14
Q
Components of agar:
A
polysaccharide extract from seaweed, borate, sulfate, diatomaceous earth, clay, silica, wax, rubber, thixotrophic (gel that can liquify when activated) materials, water
15
Q
Function of seaweed in agar:
A
colloidal particles, basis of gel
16
Q
Function of borate in agar:
A
strength
17
Q
Function of sulfate in agar:
A
hardener
18
Q
Function of diatomaceous earth, clay, silica, wax, and rubber in agar:
A
fillers
19
Q
Function of thixotrophic materials in agar:
A
thickeners (thixo/ thick)
20
Q
Function of water in agar:
A
reaction medium
21
Q
2 components in the highest proportion in agar:
A
seaweed (polysaccharide extract of), sulfate (hardener), then fillers, then thickeners, then strenghteners
22
Q
Major issue w using agar:
A
requires special equip and prep: hydrocolloid condition/ water bath, water cooled tray connected to rubber hose
23
Q
To accelerate gelation of agar:
A
circulate cool water (18-21’C) thru water cooled tray for 3-5m
24
Q
Adv of agar:
A
very hydrophilic, used in moisture, no adhesives or custom tray, easy to pour, acceptable detail, good taste, cheap, non-toxic, non-staining
25
Disad of agar:
pour immediately and only once, compatible only w die stone, tech sensitive, prepared in advance, low tear strength, special equip
26
Most widely used IM:
alginate
27
Indications, alginate:
complete/ partial dentures, opposing and study models, temp crowns and bridge impressions, whitening trays, mouth guard, ortho impressions
28
Components of alginate:
sodium phosphate, sodium alginate, potassium alginate, potassium titanium fluoride, calcium sulfate, zinc oxide, diatomaceous earth
29
Function of sodium and potassium alginates:
soluble alginate
30
Function of calcium sulfate:
Reactor
31
Function of zinc oxide and diatomaceous earth:
filler particle
32
Function of potassium titanium fluoride:
hardener (think titanium = strong)
33
Function of sodium phosphate:
retarder (oleic or stearic acid in polysulfides)
34
Greatest to least percentage of the components of alginate:
diatomaceous earth (filler), calcium sulfate (reactor), sodium and potassium alginates (soluble alginate), zinc oxide (filler), potassium titanium fluoride (hardener), sodium phosphate (retarder)
35
Chemical reaction of alginate:
Na/K-alginate and calcium sulfate plus water --> Ca+2 alginate and K sulfate
36
Final gel of alginate consists of:
(brush heap of) calcium alginate fibril network around unreacted Na+ alginate sol, water, filler particles, by products
37
Mixing time of alginate:
45-60s, fast vs. normal set
38
Type I alginate:
fast setting, not less than 1m or more than 2m, mixing time: 45s, working time: 30-75s (best for gaggers?)
39
Type II alginate:
normal setting, gels bw 2 and 4.5m, mixing time: 1m, working time: 2-3.5m
40
Gelation time of alginate, best regulated by:
amt of retarder, (also w/p ratio, mixing time (not rec), water temp)
41
Why is changing w/p ratio and mixing time not rec?
alters strength and quality
42
Purpose of smearing alginate on teeth prior to seating impression tray?
ask. I assume it helps with picking up surface detail
43
Disinfection of alginate:
spray or immersion for less than 10m
44
Disinfectants for alginate:
chlorine compounds, iodophors, short term glutaraldehyde (IGC) (same as impression compound, short term vs. 2% alkaline)
45
TF? Alginate is dimensionally stable.
F
46
Syneresis:
loss of water, evaporation or exuding, shrinkage
47
Shelf life, alginate:
1yr
48
When will alginate fail to set or set too rapidly?
elevated temp
49
Store alginate here:
cool, dry, air tight container
50
Adv of alginate:
chemical set, hydrophilic, cheap, easy to manipulate, comfortable for pt, no equip
51
Disadv of alginate:
dimensional accuracy, tear strength, reproduction of detail, poured immediately and only once, diff to disinfect
52
Causes of grainy material in agar:
inadequate boiling, storage temp too low, storage time too long
53
Causes of tearing of agar:
inadequate bulk, premature removal, syringe (light body) partially gelled when seated
54
Causes of voids/bubble in agar:
gelation of material (preventing flow) or material too cold
55
Causes of grainy material in alginate:
improper or prolonged mixing, low w/p ratio
56
Causes of separation of syringe materials (light body) in alginate or agar:
premature gelation of either material
57
Causes of tearing of alginate:
moisture contamination, inadequate bulk, premature removal
58
Causes of voids/bubble in alginate:
aerated during mixing, moisture/ debris on tissue, undue (inappropriate) gelation preventing flow
59
Use when extremely accurate impression is needed:
elastomeric
60
3 types of elastomeric IM's:
Light/extra light body, monophase (medium bodied?), heavy body and putty
61
Light/extra light body is aka:
syringe or wash material
62
How can monophase be used?
syringe and tray material
63
Tray material:
heavy body, putty, or monophase
64
Function of heavy body:
force light body into close contact
65
Catalyst is aka:
accelerator
66
First non-aq elastomer:
polysulfide
67
polysulfide by product:
water, distortion
68
TF? Water will increase the setting time of polysulfides:
F. decrease (Does this mean the reaction rate increases as it proceeds due to the by product formation of water?)
69
IM w exothermic setting reaction:
polysulfide
70
Composition of polysulfide base:
polysulfide polymer, sulfur-containing mercaptan (80-85%), sulfur, dibutyl phthalate, titanium dioxide
71
Function of titanium dioxide in polysulfide IM:
filler
72
Function of dibutyl phthalate in polysulfide IM:
plasticizer, viscocity
73
Function of sulfur in polysulfide IM:
enhance reaction
74
Composition of catalyst, polysulfide IM:
lead oxide, oleic or stearic acid
75
Function of lead oxide in polysulfide IM:
oxidizing agent
76
Function of oleic or stearic acid in polysulfide IM:
retarders
77
Reaction of polysulfide IM:
MERCAPTAN + lead dioxide --> POLYSULFIDE + lead oxide + water
78
Setting time of polysulfide IM:
8-12m
79
Pour up polysulfide IM's within:
1hr, water lost, shrinkage
80
Adv of polysulfide IM's:
HIGHEST TEAR STRENGTH, cheap, detail, slightly hydrophilic, working time, flexible, EASIEST TO REMOVE, even from undercuts
81
The temp of the plate on which you mix (this/these material(s)) affects setting time:
polysulfide and condensation silicone
82
Disadv of polysulfide IM:
bad taste/smell, poured w/in 1hr, dimensional stability, need custom tray and adhesives, 10m in mouth, humidity and temp dec working time, stain clothes
83
Condensation silicone by product:
ethyl alcohol
84
Composition of base, condensation:
hydroxyl dimethyl siloxane, calcium carbonate, silica (both fillers)
85
Composition of catalyst, condensation:
alkyl silicate, stannous octate suspension
86
condensation silicone reaction:
dimethyl and orthoethyl siloxane(s) reacted w stannous octate --> silicone rubber and ethanol
87
Why is condensation silicone IM difficult to mix?
disparity in viscosity of the components
88
The putty we use for the external surface form is what type of material?
condensation silicone IM (check) (or is it addition?)
89
Adv of condensation silicone IM:
odorless, rel short working time (6-8m), recovery from deformation, used w putty to customize a custom tray, more elastic that polysulfides, can be removed from undercuts (why is con more elastic than polysulfide, but polys is easier to remove from undercuts?), less affected by high temp and humidity
90
Materials that can be removed from undercuts:
condensation and polysulfide material (not polyethers)
91
Which are more elastic, polysulfide IM or condensation materials?
condensation silicone
92
Disadv to condensation Silicone materials:
Shrinkage, Sulfur inhibits setting, need Surfactant to pour gypsum cast, Shelf life, hydrophobic, poor wetting, dry field ESSENTIAL, alcohol by-product, less dimensional stability, pour w/in 30m,
93
Function of surfactant with condensation silicone:
hydrophobic material, decreases surface tension, allows water based material to spread on surface
94
Addition silicone:
Latex gloves/sulfur inhibits setting, set is highly cross-linked, no by-produts, least toxic and non-irritating elastomer, most are hydrophobic and need surfactant before pouring
95
Addition silicone is aka:
vinyl polysiloxane (VPS), polyvinyl siloxane (PVS)
96
Least toxic and non-irritating IM:
Addition silicone:
97
Indications for addition silicone:
final, implant, or edentulous impressions, matrix for "wax-up", matrix for temp, study models
98
Base of addition silicone:
polymethylhydrogensiloxane, divinylpoysiloxane,
99
Catalyst of addition silicone:
divinylpolysiloxane, platinum salts, fillers, activators, retarders, nonionic surfactants
100
Latex, retraction cords, rubber dam, and retraction or fluid will inhibit the setting of:
addition and condensation silicones (vinylpolysiloxanes, sulfur powder, wear vinyl gloves)
101
Disinfection of addition silicone:
tap water, dry w air, glutaraldehydes, chlorine, iodophors, phenolic sprays (PIGC)
102
Adv of addition silicone:
MOST DIMENSIONALLY STABLE (final impressions!), accurate, doesn't need to be poured immediately, poured more than once, fast recovery from deformation, adequate tear strength, no smell or taste, customizing of stock trays, stable in most disinfecting solutions, automixing devices, monophase or single viscosity materials
103
Diadv of addition silicone:
expensive, sulfur inhibits polymerization, many hydrophobic, difficult to pour wo surfactant, need dry working env
104
Single step medium viscosity:
polyether, 60's
105
Stiffest IM:
polyether (stiffest, yet polysulfide has greater tear resistance?)
106
Base composition of polyether IM:
polyether polymer, colloidal silica (filler), plasticizer
107
Catalyst composition of polyether IM:
Aromatic sulfonic acid esther (cross-linking agent), thickening agent
108
Cross-linking agent in catalyst of polyether IMl:
Aromatic sulfonic acid esther
109
TF? Polyether is only available in one viscosity.
F
110
Is curing rate more sensitive to temperature for polyether or addition silicone?
addition silicone
111
Adv of polyether IM:
very accurate, tray adhesive stronger than those for silicones, short setting time (5m in mouth), dimensionally stable if kept dry (no volatile by product), doesn't need to be poured immediately, auto mixing device available, higher tear resistance than silicones but lower than polysulfide.
112
Arrange polyethers, silicones, and polysulfides from lowest to higher tear resistance:
silicones, polyether, polysulifde
113
Disadv of polyether IM:
expensive, bad taste, short working time may limit # of prepped teeth to be captured on in impression, stiff on setting, difficult to remove from mouth w undercuts, more diff to separate cast from impression, stiffness may result in die breakage, slightly less elastic than VPS
114
Reasons to redo impression:
materiial has visible streaks in it/ not properly mixed, tray shows thru at critical areas, voids, folds, creases in critical areas, even uninterupted extension of impression beyond margins of prepped teeth, material separated from tray
115
consequences of bad impression:
not enough space for proper resto fabrication and esthetics, inability to seat resto, high occlusion, open margins, weak resto, rest failure
116
Triple tray is aka:
double arch
117
Good impression of prep:
all of prep and adjacent teeth
118
To avoid air entrapment in wash material:
immerse syringe tip in wash material
119
Result of blood or saliva contamination of impression:
air bubbles/ voids, can't displace by itself
120
Leave this much space of lateral retraction:
more than 0.5mm
121
Tray movement during setting results in:
drag
122
How full should the impression tray be?
2/3 full
123
Causes exposed tray:
not enough material or too much pressure
124
Reasons why IM might not set:
latex, expired, improper storage
125
Result of using wash that is incompatible w heavy body:
lamination, separation of the two (this could also happen if you don't let it set enough)
126
Inelastic IM's:
insig amt of elastic deformation during bending or tensile stress, mostly used for edentulous, can't use for pts w deep undercuts
127
Impression plaster:
ADA specification No-25 Type 1 gypsum product
128
Indications for impression plaster:
prelim impression for edentuolous
129
Composition of impression plaster:
Calcium sulfate hemihydrate, potassium sulfate-accelerator, borax - retarder, starch
130
Function of potassium sulfate in impression plaster:
accelerator
131
Function of borax in impression plaster:
retarder
132
Overall rxn of impression plaster:
hemi- to dihydrate
133
Do this before pouring impression plaster:
separating medium (saturated soap solution) on the surface
134
Adv of impression plaster:
good surface detail, excellent dimensional stability, setting rate can be controlled
135
Disadv to impression plaster:
pt discomfort, can't be used in undercut areas
136
Impression compound is aka:
modelling plastic
137
Forms impression compound comes in:
sheets and sticks
138
2 types of impression compound:
Low fusing/ impression compound, high fusing/tray compound
139
Low fusing compound is used for:
impressions, fusing temp 55-60'C
140
high fusing compound is used for:
forming trays in mouth, fusing temp: 70'C
141
Indications for use of Type 2 impression compound:
border moulding
142
Composition of impression compound:
waxes, thermoplastic resins, filler, coloring agent, plasticizer (shellac, stearic acid and gutta percha) - improves plasticity and workability
143
Composition of plasticizer in impression compound:
shellac, stearic acid and gutta purcha
144
Temp at which impression compound loses plasticity is called, what temp is it?
fusion temperature/ glass transition temp (?)(37-39'C)
145
What can happen if direct flame is used for impression compound:
boiling or ignition
146
Prolonged immersion or overheating of impression compound can lead to the product being:
brittle and grainy
147
Make the cast or die within this time frame after using impression compound:
1hr
148
Disinfection of impression compound:
2% alkaline glutaraldehyde, iodophors or chlorine compounds (IGC) (same as alginate 2% alkaline vs. short term)
149
Adv of impression compound:
non irritant, non toxic, reusable, reheated and readapted, can support other materials for wash impression
150
Problem with reusing impression compound:
constituents are leached out
151
Disadv of impression compound:
poor dimensional stability, poor surface detail, distort if removed from undercuts, soft tissue will be compressed
152
Indications for ZOE:
IM for edentulous arch, surgical dressing, bite registration paste, temp material, RCT filling, cement medium, temp relining material for dentures
153
Components of base of ZOE:
zinc oxide and fixed vegetable or mineral oil
154
Components of catalyst of ZOE:
gum or polymerized ROSIN, silica filler, oil of cloves (70-85% eugenol), resinous balsam, accelerator (zinc acetate, glacial acetic acid), lanolin
155
What is the accelerator in the accelerator of ZOE composed of?
zinc acetate, glacial acetic acid
156
What does the acid-base reaction of ZOE form?
a chelate (chelation reaction)
157
To shorten setting time of ZOE:
accelerator (zing acetate), drop of water to eugenol paste, extend mixing time, alter paste ratios
158
To lengthen setting time of ZOE:
cool spatula and mix slab, add inert oils and waxes during mixing (olive oil or petrolatum), alter paste ratios
159
Disinfection of ZOE:
immersion preferred, glutaraldehyde or iodophors, not compatible w phenolic compounds, but phenolic spray can be used (PIG spray)
160
ZOE is not compatible w this type of disinfectant.
phenolic compounds, but phenolic sprays can be used
161
Adv of ZOE:
dimensionally stable (less than 0.1%), good surface detail, minor defect can be corrected locally wo discarding a good impression, no separating medium required before pouring
162
Disadv of ZOE:
Can't be used in undercuts, burning sensation for some bc of eugenol, difficult to handle
163
Top 3 most commonly used IM's:
Alginate, then PVS, then polyether
164
Easiest and hardest to use:
easiest: addition, hardest: agar
165
3 most pleasant:
alginate, addition, condensation
166
Easiest and hardest to remove:
Easy: polysulfide, Moderate: condensation, addition, polyether (hardest)
167
Easiest and hardest to disinfect:
easy: addition, hardest: agar, alginate
168
Best and worst in terms of wettability and castability:
best: agar, alginate, worst: polysulfide, condensation
169
Elastic recovery, highest to lowest:
addition, polyether, condensation, agar, alginate, polysulfide (AdPecaGalps)
170
Shrinkage, most and least:
most: agar, alginate, least: addition
171
Highest and lowest tear strength:
highest: polysulfide, lowest: alginate
172
Working time, longest to shortest:
agar, polysulfide, silicones, alginate / polyether
173
Setting time, shortest to longest:
alginate, polyether, agar, silicones, polysulfide
174
stiffness, most to least:
polyether, addition silicone, condensation silicone, polysulfide/ hydrocolloids
175
Tear strength, greatest to least:
polysulfide, addition, polyether, condensation, hydrocolloids
176
Cost, lowest to highest:
alginate, agar/ polysulfide, condensation, addition, polyether
177
Dimensional stability, best to worst:
addition, polyether, polysulfide, condensation, hydrocolloid
178
Wettabilty best to worst:
hydrocolloids, polyether, hydrophilic addition, polysulfide, hydrophobic addition / condensation
179
Castability, best to worst:
hydrocolloids, hydrophilic addition, polyether, polysulfide, hydrophobic addition / condensation
180
Most widely used material for study models:
alginate: inexpensive, displaces moisture, lower detail reproduction, dimensionally unstable
181
Most widely used material for prosthodontics:
addition silicones: accurate, dimensionally stable, user friendly, expensive
182
Require surfactant when pouring up:
addition/ condensation
183
Can be poured more than once:
addition
184
Easiest to disinfect, least shrinkage, highest elastic recovery, pleasant taste, can be poured more than once:
addition
185
2 that give of by products:
polysulfide: water, condensation: ethyl alcohol
