ELASTOMERIC / SILICONE MATERIAL
¤ Used for secondary impression generally
¤ Primary impression for knife-edge ridge cases only
¤ Setting reaction is by polymerization type of setting reaction here

POLYSULFIDE
- Hydrophobic
- Catalyst – lead, therefore bad taste, least patient acceptance – disadvantage
- Most biocompatible material due to the sulfide content
- By-products after polymerization – water, which is a large molecule, thus not the best impression material
- Can do electroplating – advantage
- Used in cases with deep undercuts- rubbery consistency
- It has the consistency of thycol rubber, - high tear strength
- Not expensive – advantage
- Must pour the cast within 30 mins
- Not compatible with epoxy resin