Impression material Flashcards
1
Q
What are FOUR types of non-aqueous elastomers?
A
- Polysulfides
- Condensation silicones
- Polyethers
- Polyvinyl Siloxanes (PVS)
2
Q
Polysulfide:
- Reaction type and byproduct
- Disadvantages
A
- Reaction type: Condensation (SH, Pb2O)
- Byproduct: H2O
- Disadvantages: poor dimensional stability (water loss, temp change, continued polymerisation) Offensive odour
3
Q
Condensation silicones:
- Byproduct
A
- Byproduct: alcohol (smell)
NOTE: stability: PVS > condensation silicones > polysulfides
4
Q
PVS:
- Reaction type and byproduct
- Advantage
- Disadvantage
A
- Reaction type: addition
- Byproduct: hydrogen gas
- Advantage: very dimensionally stable
- Disadvantage: setting retarded by sulfur in latex gloves and astringident solutions
5
Q
Polyethers:
- Reaction type
- Disadvantages
- Advantage
A
- Reaction type: cationic polymerisation of imine end groups
- Disadvantages: very stiff, odour
- Advantage: very good shelf life (~5yrs)