Impression materials Flashcards Preview

Dental Materials > Impression materials > Flashcards

Flashcards in Impression materials Deck (63)
Loading flashcards...
1

What is the purpose of using impression materials and gypsum materials?

fabricate diagnostic cast

2

What is the purpose of impression materials?

makes NEGATIVE mold of dental structures

3

What is the synonymous term for irreversible hydrocolloid?

alginate for impression

4

What are the characteristics of ideal impression materials?

low cost, long self life, bio-compatible, stable, good handling, pleasant to patient

5

What are two rigid impression materials?

zinc oxide eugenol and plaster

6

What are two plastic impression materials?

wax and compound

7

What are two elastic impression materials?

hydrocolloids and elastomers

8

What are the limitations of alginate?

not used for crown or bridge impression because of the lack of accuracy

9

define sol

resembles a solution but is made of colloidal particles dispersed in liquid

10

What is the product of alginic acid in water?

sol

11

How can sol transform into gel?

through control of temperature and chemical

12

Define gel

entangles network of solid colloidal particles in which liquid is trapped in the interstices and held by capillary forces

13

When transforming from sol to gel, which control is reversible

temperature is reversible
chemically is irreversible

14

What is the purpose of a reactant in impression material?

allows for cross linking

15

What is the purpose of a retarder in impression material?

it controls the reaction

16

What is the purpose of a reinforced filler in impression material?

adds body and strength

17

What is the purpose of potassium sulfate or alkani zinc fluorides in impression material?

provides good surfaces on gypsum dies

18

What is the affect of increasing the powder and decreasing the water in alginate?

Lowering the W/P ratio causes an increase in strength, increase tear resistance, decreases working/setting time

19

How does lowering the temperature affect alignate?

increasing working/setting time

20

What is mixing time a measure of?

how long it takes to form uniform blend

21

What is working time a measure of?

how long from the beginning of the reaction until the setting begins

22

What is setting time a measure of?

how long from the beginning of the mix until the setting reaction is over

23

Is syneresis the gain or loss of eater to the surrounding?

loss

24

Is imbibition the gain or loss of water into the surrounding?

gain

25

What are the advantages of alginate?

economical, easy to use, quick setting, quick setting, fair tasting, hydrophilic, displace saliva/blood, stick trays

26

What are the disadvantages of alginate?

limited detail reproduction, low tear resistance, single pour only, quick pouring required, low dimensional stability

27

What are three well known hydrophobic impression materials?

polysulfides
polysiloxanes
polyethers

28

Doe hydrophobic materials have a high or low contact angle?

high angle because the water beads up

29

How are polysiloxanes made less hydrophobic?

use of a surfactant or incoperating moieties into the silicone backbone

30

How is polysiloxanes controled?

by molecular weight of the oligomers