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Complete Veneer Crown > Impression Materials > Flashcards

Flashcards in Impression Materials Deck (37)
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1

What do dimensional changes need to add up to?

zero

2

What are the three types of impression materials?

rigid, plastic and (visco)elastic

3

Viscoelastic impression materials are found as reversible (agar) or irreversible (alginate) ___.

hydrocolloids

4

Viscoelastic impression materials can also be found as synthetic ___. These are ___ that polymerize into ___.

elastomers; oligomers; elastomers

5

What are the different forms of synthetic elastomers?

polysulfide, silicone, polyether, and new product

6

Which is the most common for of synthetic elastomer?q

addition silicone

7

T/F. Light and heavy body impression materials are used separately to enhance the accuracy of the final impression.

False, they are used together.

8

T/F. The light impression material is used for detail while the heavy is used in the other areas.

True.

9

Define hydrocolloid.

Water is bound within a colloid matrix

10

Both Alginate (___)(reversible/irreversible) and Agar (___) (reversible/irreversible) lack dimensional stability with time and require ___ pouring of models.

irreversible; reversible; immediate

11

What type of polymer has no cross-linking and its physical state is reversibly controlled by temperature? For example, when heated it is fluid and when cooled it can be removed from the patient.

Thermoplastic

12

A ___ polymer is transformed from monomer to polymer and involves irreversible ___.

Thermoset; cross-linking

13

T/F. Condensation polymerization releases no by products.

False, addition polymerization releases no by-products whereas, condensation does.

14

During the change from liquid or paste into a solid, advantageous final properties are ___ (increased/decreased).

increased.

15

During the change from liquid/paste into a solid, the inherent density increase causes a volumetric ___ (shrinkage).

contraction

16

During the change from liquid/paste into a solid, heat of reaction causes material to ___ ___, but this is usually minor.

heat up.

17

During the change from liquid/paste into a solid, there is a ___ on cooling.

contraction

18

Polysulfide low molecular weight oligomers containing reactive ___ groups.

mercaptan

19

Polysulfide oxidized by lead dioxide or copper hydroxide to form a polysulfide ___ with a ___ condensate. This stains and does not taste good.

rubber; water

20

T/F. For polysulfides to be accurate, this material requires a rigid custom tray for minimal thickness of impression materials.

True.

21

T/F. Polysulfides recover from permenant deformation.

False, they do not recover from permanent deformation.

22

T/F. Polysulfides should be poured as quickly as possible.

True.

23

Silicones (Polysiloxanes) are inherently ___ but the addition type can be made more ___.

hydrophobic; hydophilic

24

What was the first type of silicone introduced?

condensation

25

How do you make the addition type of silicone more hydrophilic?

simple addition of surfactant or chemical incorporation of hydrophilic moieties into the silicone backbone.

26

Fluid material needs a ___ contact angle, therefore you want it to be ___.

low; hydrophilic

27

Why are contact angles important?

unset impression material over wet oral structures
unset gypsum-water mix into set impression

28

Condensation silicone have low molecular weight oligomers containing reactive terminal ___ groups which react with ortho-ethyl silicate and stannous octoate to form the three dimensional network rubber with the liberation of ___ ___.

hydroxyl; ethyl alcohol

29

With addition silicone, in the presence of ___ acid, ionic polymerization produces chain-lengthening and cross linking.

chloroplatinic

30

With addition silicone, if there is residual ___ groups present from the mucosa, a secondary reaction occurs which produces ___ gas.

hydroxyl; hydrogen