Impression Materials

Question 1

Elastic Aqueous hydrocolloids (2)

Answer 1

Agar

Alginate

Question 2

Elastic Non-aqueous elastomers (3)

Answer 2

Polysulfide

Silicones (Condensation silicones & Addition silicones)

Polyether

Question 3

What is the syneresis process with respect to aqueous hydrocolloids?

Answer 3

fibril cross linking continues.

aqueous hydrocolloids contract over time and exudes water

Question 4

What is imbibition?

Answer 4

Water absorption & swelling of the aqueous hydrocolloids

Question 5

3 things that happen to aqueous hydrocolloids?

Answer 5

evaporation

syneresis

imbibition

Question 6

Key alginate disadvantages?

Answer 6

•SINGLE CAST•

Also:

tears easily

dimensionally unstable (immediate pour)

lower detail reproduction (not good for fixed pros)

high permanent deformation

difficult to disinfect

Question 7

What is the key advantage of addition silicones?

Answer 7

•Multiple casts•

Also:

highly accurate

high dimensional stability (pour up to one week)

stock or custom trays

easy to mix

pleasant odor

Question 8

Key disadvantage of polyether?

Answer 8

•RIGID (difficult to remove from undercuts)•

Also:

expensive

short working time

bitter taste

low tear strength

absorbs water (changes dimension)

Question 9

Stiffness (most to least) of impression materials

Answer 9

Polyether (most)

addition silicone

condensation silicone

polysulfide & hydrocolloids (least)