Elastomers Flashcards
1
Q
Elastomers are for what kinds of work
A
Crown and bridge work
2
Q
Used when high degree of accuracy is needed
A
Elastomers
3
Q
Rubber polymers, soft and rubber-like, easily stretched and rapidly recover
A
Elastomers
4
Q
Elastomers are produced by
A
Vulcanization/ curing
5
Q
Cross linking process that involves sulfur mercaptan groups
A
Vulcanization/curing
6
Q
More fillers added
Increase or decrease of consistency of paste?
Increase or decrease of fluidity?
A
Increase consistency of paste
Decrease fluidity
7
Q
Three types of viscosities
A
Light-body materials
Medium-body materials
Heavy-body materials
8
Q
Syringing around prepared teeth to register finest details
A
Light-body materials
9
Q
Type of viscosity that is too fluid when held in tray
A
Light-body material
10
Q
Intermediate viscosity.
Viscous enough to fill and remain in tray.
Can be syringed like light-body
A
Medium-body materials
11
Q
Putty
Fill the tray
Provide support for less viscous
A
Heavy-body materials
12
Q
Ultimately more flexible light-body materials
A
Heavy-body materials
13
Q
2 advantages of elastomers over hydrocolloids
A
Good tear resistance
Dimensional stability
14
Q
Disadvantage of elastomers
A
Hydrophobic in nature
15
Q
Types of elastomers
A
Polysulfide
Condensation silicone
Addition silicon
Polyether
16
Q
Oldest most economic elastomer
A
Polysulfide
17
Q
Not the most accurate and stable
And is supplied in 2 tubes
A
Polysulfide
18
Q
2 tubes of polysulfide
A
Base
Catalyst
19
Q
Chemical group containing long-chain organic polymer with many SH groups
A
Mercaptan
20
Q
Meaning of SH groups
A
Sulfhydril
21
Q
Liquid polymer made by mixing with fillers (silica particles) plus oils that improve handling of paste
A
Base paste
22
Q
Usually pigmented white, stains clothing
A
Base paste
23
Q
Composition of Base paste of polysulfide
A
Polysulfide
Filler
Plasticizer
24
Q
Composition of base paste that GIVES BODY
A
filler
25
Composition of base paste that controls viscosity
Plasticizer
26
Contains Lead Dioxide and additional sulfur that both enhance the chemical reaction for transforming Paste to elastic rubber
Catalyst paste
27
Lead Dioxide and additional sulfur enhance chemical reaction for transforming?
Paste to elastic rubber
28
Paste that provide odor of the polysulfide
Catalyst paste
29
T or F
| Catalyst paste also stains cloth and skin
True
30
Composition of Catalyst Paste
Lead Dioxide
Sulfur
Inert oil
31
Composition of catalyst paste that causes polymerization and cross-linking
Lead Dioxide
32
Composition of catalyst paste that facilitates reaction
Sulfur
33
Composition of catalyst paste that forms a paste
Inert oil
34
T or F
| Polysulfide is easy to use
False
| Polysulfide is more difficult to use
35
T or F
| Polysulfide has a slightly greater tear strength
True
36
T or F
| Polysulfide has more objectionable characteristics
True
37
Polysulfide is useful for teeth with?
Deep undercuts
38
Polysulfide manipulation
Squeeze equal length with 1 INCH INTERVAL
Mix 5-10 seconds, circular motion, CATALYST TO BASE
mixing 45 SECONDS
Full working time 5-7 MINS
39
Advantages of polysulfide
```
Dimensional stability
Accuracy
Different viscosities
Long working time
Long shelf life
```
DAD LL
40
Disadvantages of polysulfide
Lead-oxide has toxic effects
Lead oxide stains
Unpleasant rubbery smell
Only be used in special tray
41
Working time of polysulfide
5-7 mins
42
Polysulfide is non toxic because?
When lead dioxide is mixed with catalyst, it becomes non toxic
43
Permanent deformation during removal of polysulfide, how many percent?
2% - 3%
44
T or F
| Polysulfide is compatible with die and cast materials
True
45
Shelf life of polysulfide is extended when placed in?
Refrigerator
46
T or F
| Polysulfide has a WHITE BASE and COLORED CATALYST
True
47
Polysulfide can be used repeatedly
Dimensional stability
48
Flow after setting of polysulfide
Pouring stone
49
Consistency of polysulfide
Viscosity depends on reinforcing agents available
50
Polysulfide doesn't tear easily
Flexibility
51
T or F
Polysulfide is compatible with electroforming.
It is good in reproducing details.
Both statements are true
52
Althought it is stable, this elastomer should be casted in 24hrs
Condensation Silicone
53
Tor F
| Both pastes of condensation silicon contain liquid silicone polymer.
True
54
Liquid silicone is made from?
Polydimethylsiloxane
55
Polydimethylsiloxane contain many?
OH (hydroxyl) groups
56
Which contains ORTHOALKYLSILICATE in condensation silicon, base or catalyst paste?
Base paste
57
It is an organic molecule that causes polymer chains to become cross linked
Orthoalkylsilicate
58
Cross-linked polymer chains in condensation silicon results to?
Transforming paste to fairly rigid and dimensionally stable
59
It is a paste of condensation silicone that contains TIN OCTATE CATALYST
Catalyst paste of condensation silicon
60
T or F
| Catalyst paste of condensation silicon also contains the same component as base paste
True
61
Which is labeled as the liquid components in condensation silicon, base or catalyst?
Catalyst paste
62
Advantages of condensation silicone
Accurate
Ease of use
Used On severe undercuts
63
Disadvantages of condensation silicon
Hydrogen evolution
| Cause irritation
64
Reaction in condensation silicon
Dimethylsilohexane +ortho-ethyl silicate + tin octate ➡️silicone rubber + ethanol
65
T or F
| Condensation silicon has a short working time
True
| CS has 6-8 mins working time
66
What happens during the 1ST hour of condensation silicon
Most dimensional changes occur
67
T or F
| Condensation silicon is also non toxic
True
68
T or F
| Condensation silicone is compatible with model plaster and electropating
True
69
What elastomer has poor wettability
Condensation silicon
70
What elastomer has
LOW permanent deformation and
LOW flow and flexibility but has
HIGH tear strength
Condensation silicone
71
Addition silicone is also known as?
Polyvinylsiloxanes
72
Polyvinylsiloxanes in addition silicones contains
Silicone polymers that have many Vinyl groups
73
Addition silicon is supplied in 3 forms
Two paste system
Gun-and-cartridge system
Heavy putty
74
One of the 3 forms of supply of addition silicon where
Base and catalyst are dispersed from side by side
Gun-and-cartridge system
75
One of the 3 forma of supply of addition silicon that
Is used in the PUTTY-WASH technique.
Base and catalyst in plastic tubes
Putty scooped out and mixed by hand
Heavy Putty
76
T or F
| Addition silicons are hydrophobic materials
True
This characteristic has led to some problems with air bubbles trapped on the surfaceof the impression when pouring gypsum cast and dies
77
Advantages of addition silicone
Accurate
Ease of use
FAST SETTING
Wide range viscosities
78
Disadvantages of addition silicon
Hydrogen evolution - can result in pinpoint voids in the gypsum casts
TO COMPENSATE FOR THE HYDROGEN GAS, wait for an HOUR OR MORE before pouring the impression
79
Reaction of addition silicone
Hydrogen containing silohexane + vinyl terminal + chloroplatinic acid ➡️ silicone rubber
80
What elastomer has the LOWEST DIMENSIONAL CHANGE from all impression materials
Addition silicone
81
Elastomer that has superior accuracy
Addition silicone
82
```
T or F
Addition silicone has
Short working time
Low flexibility
Less tissue reaction
```
True
83
T or F
In addition silicone, silicones are HIGHLY HYDROPHOBIC. Surface is poorly wetted by water with CONTACT ANGLE OF 90 deg which INCREASES surface bubbles
True
84
Stiffest type of elastomer
Polyether
85
Name of this elastomer is derived from the fact that they are composed of POLYETHER POLYMER MOLECULES
Polyether
86
Polyether is used for what kinds of work
Crown and bridge work, partial dentures, implants and overdentures
87
Composition of base paste of polyether
Polyether
| Filler
88
Composition of catalyst paste of polyether
SULPHONIC ACID ESTER
89
Composition of catalyst paste of polyether that enhances further polymerization and crosslinking of the polymer chains during chemical reaction.
Reaction is responsible for transforming PASTE TO STIFF POLYETHER RUBBER
Sulphonic acid ester
90
Full arch impression made from these materials may be difficult to remove from the mouth because of its stiffness
Polyether
91
Advantages of polyether
Accuracy
Ease of use
GOOD ON UNDERCUTS
92
Disadvantages of polyether
Sulphonic acid ester cause allergic reactions
Poor tear strength
Rapid setting time
Stiff set material
93
Reaction of polyether
Polyether + sulphonic ester ➡️ cross-linked rubber
94
Elastomer that has the SHORTEST WORKING TIME
Polyether
95
Elastomer that has
Less permanent deformation
LOW FLOW, HIGH STIFFNESS
and absorbs water, dried after disinfecting
Polyether
96
T or F
In elastomers, Working and setting time DECREASES as viscosity INCREASES
True
97
All materials change dimensionally.
Changed is greater for POLYSULFIDE and CONDENSATION SILICONE.
Stored impression must be kept in a dry cool environment
Dimensional stability
98
Rubber impression materials capable of reproducing details
Reproduction of details
99
T or F
| Elastic properties of elastomers improve with an INCREASE IN CURING TIME in the mouth
True
100
The LONGER the impression can remain in the mouth, LESS distortion upon removal
Elasticity
101
Ranking of tear strength from lowest to higest
Hydrocolloids (agar and alginate)
Silicones ( CS and AS)
Polyether
Polysulfide
102
Probability of allergic/toxic reactions is small
Biocompatibility
Contact dermatitis from POLYETHER has been reported
103
Properly compounded-does nit deteriorate
Shelf life
104
Mixing and handling
T or F
Equal lengths of base and catalyst dispensed but not touching
True
105
Mixing and handling
T or F
Viscous nature - stiff tapered steel slatula is used to mix
True
106
Mixing and handling
T or F
First Catalyst paste is picked up on spatula, add to base, mix for 10 secs, circular motion
True
107
Mixing and handling
T or F
Material is wiped across entire surface of pad with pressing motion
Aim is to produce HOMOGENOUS creamy consistency
True
108
Mixing and handling
T or F
Material can be loaded in syringe or the setting tray
Elastomers often use acrylic custom tray
True
109
Mixing and handling
T or F
Elastomeric impression should be removed from mouth with steady force
True
110
Failure to produce acceptable gypsum is associated with error in mishandling rather than deficiency in material properties
Effects of mishandling
111
Pastes supplied in two cylinder tubes mounted side by side
| Second tube contains PLASTIC PROPELLER TYPE ASSEMBLY attached to end of cylinder tubes
Gun and cartridge system
112
T or F
| In gun and cartridge system, as material is extruded, two diff pastes are mixed together to produce homogenous material
True
113
Syringe- inject material around tooth prep
| While the assistant load the impression tray material dispensed directly form the gun
Gun and cartridge system
114
Cleanup of spatula is easy, just...
Wait for material to set then peel off
115
Certain elastomeric materials should be poured asap except for
Addition silicone and Polyether
116
Delay pouring of addition silicone for atleast
45 mins to 1hr
117
What will happen If impression is poured too soon
It will produce tiny bubbles on surface
118
T or F
| Delay in pouring has no effect on dimensional stability
True
