Dr. Johnston (Impression Materials)

Question 1

three categories of impression materials

Answer 1

• rigid/brittle (plaster)
• plastic (wax)
• elastic (hydrocolloids and elastomers)(what we use)

Question 2

reversible hydrocolloid

Answer 2

agar (requires special equipment)

Question 3

irreversible hydrocolloid

Answer 3

alginate (cheap and easy)

Question 4

what are some characteristics of polysufides (what we use)

Answer 4

• conforms well to preped tooth
• requires custom tray
• ASAP pouring

Question 5

silicones are inherently ____ but if you add SURFACTANT they become _____

Answer 5

• hydrophobic

- hydrophilic

Question 6

do we want a large or small contact angle?

Answer 6

small

Question 7

oligomers containing REACTIVE TERMINAL HYDROXYL groups that react and form a 3D network rubber

Answer 7

condensation silicon

Question 8

what is special about addition silicon?

Answer 8

pouring of the model should be delayed until all of this hydrogen is liberated (no latex gloves)

Question 9

requires a custom tray and irritates the skin

Answer 9

polyether

Question 10

ideal impression materials have a ___ setting time

Answer 10

short

Question 11

the time required for ____ ____ after removal from the mouth is easily spent preparing for the pouring of the cast and is no cause for further delay

Answer 11

anelastic recovery

*reforms to how you want it to be in the mouth