Elastomers

Question 1

The process of changing the rubber
base product or liquid polymer to a rubber-like material.

Answer 1

Vulcanization/Curing

Question 2

Classification of Elastomers based on chemical composition

Answer 2

1. Polyether
2. Polysulfides
3. Silicones
   a. Addition
   b. Condensation

Question 3

Types of consistency/viscosity for rubber impressions

Answer 3

1. Light bodied impression
2. Regular/medium bodied
3. Heavy bodied

Question 4

A group of flexible chemical polymers that are either chemically
or physically cross-linked.

Answer 4

Elastomeric Impression Materials

Question 6

T or F

Elastomeric impression materials can be easily stretched and rapidly recover their original dimensions when applied stresses are released

Answer 6

True

Question 7

Introduced in Germany in late 1960’s and first elastomer to be developed as impression material.

Answer 7

Polyether

Question 8

Polyether Base and Catalyst

Answer 8

Base
- polyether polymer
- colloidal silica (filler)
- glycol ether or phthalate

Catalyst
- alkyl aromatic sulfonate

Question 9

Advantages of polyether

Answer 9

• Fast working and setting time
• Less hydrophobic (better wetting)
• Long shelf life
• Proven accuracy
• Adequate tear strength

Question 10

Disadvantages of polyether

Answer 10

• Clean but tastes bad
• Slightly more expensive
• Stiffness requires blocking undercuts

Question 11

First non-aqueous elastomeric impression material often called “rubber” or “rubber base”

Answer 11

Polysulfide

Question 12

Polysulfide Base and Catalyst

Answer 12

Base
- Lithopone and titanium
dioxide (filler)
- Dibutyl phthalate (plasticizer)
- Sulfur (0.5%)

Catalyst
- Lead dioxide (dark
brown color)
- Oleic and stearic acid
(retarders)

Question 13

Polysulfide disadvantages

Answer 13

• Requires a custom tray
• Odor (unpleasant)
• Messy and stains
  clothes
• Second pour is less
  accurate
• Potential for significant
  distortion

Question 13

It was the first type of silicone impression material, and also known as conventional silicones.

Answer 13

Condensation silicone

Question 13

supplied as a base paste and a low-viscosity liquid catalyst, a two-paste system, or a two-putty system

Answer 13

Condensation silicone

Question 13

Condensation silicones advantages

Answer 13

• Adequate working and
  setting time
• Pleasant odor and no
  staining
• Adequate tear strength
• Better elastic properties
  on removal

Question 13

Condensation silicone base and catalyst

Answer 13

Base
- Colloidal silica
- Metal oxide (filler)
- Colorants (homogenous
mix)

Catalyst
- Alkyl silicate and organo-tin compounds

Question 13

Condensation silicones disadvantages

Answer 13

• Poor dimensional
  stability
• Slightly more expensive
• Putty wash method is
  technique sensitive.
• Potential for significant
  distortion

Question 14

Frequently called as polyvinyl siloxane, and introduced after condensation silicones.

Answer 14

Addition silicone

Question 15

Commonly used in complete denture.

Answer 15

Addition silicone

Question 16

Advantages of Addition silicones

Answer 16

• Shorter setting time.
• Easy to mix (automatic mixing devices)

Question 17

Addition silicones disadvantages

Answer 17

• More expensive (automatic mixing
  device)
• Hydrogen gas evolution
  in some materials

Question 18

Suspension of fine particles within a liquid.

Answer 18

Colloids

Question 19

Colloids in water

Answer 19

hydrocolloid

Question 20

Types of Colloids (2)

Answer 20

Lyophilic - liquid loving sols Lyophobic - liquid hating

Question 21

Any solution in which the unit of the solute are sufficiently large so that it will not dialyze through a suitable membrane.

Answer 21

Colloids

Question 22

A substance that forms a gel with water.

Answer 22

Hydrocolloid

Question 23

Tis is made up of submicroscopic fibrils, with spaces in between called _____

Answer 23

Micelles

Question 24

Particles in a solution.

Answer 24

Dispersed particles

Question 25

solution containing a suspension of particles.

Answer 25

Dispersed Medium

Question 25

Suspension

Answer 25

The dispersed phase and the dispersion medium are not of like phase.

Question 25

Tendency to demonstrate a strong aversion to water.

Answer 25

Hydrophilic

Question 26

The dispersed phase is of the same phase as of the dispersion medium.

Answer 26

Emulsion

Question 26

Tendency to demonstrate a strong affinity for water.

Answer 26

Hydrophilic

Question 27

(agar) a colloid that contains water as the dispersion phase.

Answer 27

Hydrocolloid

Question 28

Agar impression material.

Answer 28

Reversible Hydrocolloid

Question 29

Alginate impression material.

Answer 29

Irreversible Hydrocolloid

Question 30

The transformation from a hydrocolloidnsol to gel.

Answer 30

Gelation

Question 31

The time needed to transform sol to gel.

Answer 31

Gelation time

Question 32

the temperature in which the sol is transformed into gel.

Answer 32

Gelation temperature

Question 33

The transformation from gel to sol.

Answer 33

Liquefaction

Question 34

Time needed to transform gel to sol

Answer 34

Liquefaction time

Question 35

the temperature at which the gel is transformed to sol at a higher temperature. (60-70C)

Answer 35

Liquefaction temperature

Question 36

the difference between gelation and liquefaction temperature.

Answer 36

Hysteresis

Question 37

Process of water sorption

Answer 37

Imbibition

Question 38

expression of fluid onto the surface of gel structures.

Answer 38

Syneresis

Question 39

expression of fluid onto the surface of gel structures.

Answer 39

Setting time

Question 40

The total time from the start of mixing to the final time at which an impression tray can be fully seated without distortion.

Answer 40

Working time