6- Impression Materials

Question 1

Mucostatic

Answer 1

Impression does not distort mucosa
Low viscosity
Ex. Plaster, Light body PVS

Question 2

Mucocompressive

Answer 2

Material compresses/distorts mucosa

Question 3

Thermoplastic

Answer 3

No cross linkage

Chains can move freely- will not return to original shape

Question 4

Thermoset

Answer 4

Rigid, fully cross linked- chains can’t move

Question 5

Elastomer

Answer 5

Some cross linkage, is and elastic polymer

Question 6

Types of Elastomers

Answer 6

Polysulfides (not used anymore)
Condensation silicones
Polyether ex
Addition silicones

Question 7

Advantages of Condensation Silicone

Answer 7

Clean 
No staining 
Highly elastic 
More accurate than polysulfides 
Adequate tear strength

Question 8

Disadvantages of Condensation Silicone

Answer 8

Alcohol evaporation= lack of dimensional stability
Slow polymerization= long setting time
Short working time
Hydrophobic- needs to be electroplated to be used with gypsum

Question 9

Advantages of Addition PVS

Answer 9

Highly accurate 
High dimensional stability 
Pours up to 1 week 
Stock/custom trays
Multiple casts 
Easy to mix
Pleasant odour

Question 10

Disadvantages of Addition PVS

Answer 10

Expensive
Sulfur proteins inhibit setting (can’t use latent gloves)
Short working time 
Hydrophobic - causes air bubbles 
Lower tear strength 
H2 release

Question 11

Advantages of Polyether

Answer 11

Accurate 
Good dimensional stability 
Can be poured up to 3 days 
Good surface detail retention 
Hydrophlic- good wettability  (no air bubbles)
Multiple casts 
Easy to mix

Question 12

Disadvantages of Polyether

Answer 12

Expensive 
Very rigid (but still an elastomer) 
Short working time 
Hydrophilic (absorbs water)
Bitter taste