06 Impression Materials Flashcards
What are advantages of the elastomeric Polysulfide (rubber base)?
- Excellent tear strength
- Excellent detail reproduction
- Flows well into sulcus
What are disadvantages of the elastomeric Polysulfide (rubber base)?
- Long working and setting time
- Messy, difficult to mix
- Unpleasant taste/odor
What are advantages of the elastomeric Polyether?
- Very accurate
- Rigid
- Sets quickly
- Can be poured multiple times
- Does not need to be immediately poured
- Hydrophilic
- Good wetabilty by gypsum
What are disadvantages of the elastomeric Polyether?
- Rigid
- Low tear strength
- Absorbs moisture
- Expensive
What are advantages of the elastomeric Polyvinyl Siloxane?
- Very accurate
- Low permanent deformation
- Can be poured multiple times
- Does not need to be immediately poured
- Hydrophilic
What are disadvantages of the elastomeric Polyvinyl Siloxane?
- Expensive
- Releases hydrogen gas
- Powdered gloves inhibit set of putty
Rank these materials from low shrinkage to high - polyether, PVS, polysulfide, condensation silicones
Polyether < PVS < Polysulfides < Condensation silicones (which is why they need to be poured immediately)
Rank from low (1%) to high (3-6%) in terms of permanent deformation. polyether, PVS, polysulfide, condensation silicones
- PVS (low)
- Condensation silicones
- Polyether
- Polysulfide (high)
Rank rigidity
polyether, PVS, polysulfide, condensation silicones
- Polysulfide (flexible)
- Condensation silicones
- PVS
- Polyether (rigid)
Rank tear strength
polyether, PVS, polysulfide, condensation silicones
- Polyether (low tear strength)
- PVS / Condensation
- Polysulfides (high tear strength)
Rank setting time
polyether, PVS, polysulfide, condensation silicones
- PVS, polyether (4 minutes)
- Condensation silicones
- Polysulfides (10 minutes)
Polysulfides are what in terms of flexibility, tear strength, setting time, deformation
- Most flexible
- Highest tear strength
- Longest setting time
- Highest deformation
Polyethers are what in terms of shrinkage, setting time, deformation, tear strength, rigidity
- Low shrinkage
- Short setting time
- Average deformation
- Lowest tear strength
- Most rigid
Addition silicones are what in terms of shrinkage, permanent deformation, setting time, tear strength, rigidity
- Low shrinkage
- Low permanent deformation
- Short setting time
- Avg tear strength and rigidity
Polysulfides are great for what cases?
- Removable (dentures and distal rpd)
Polyethers are great for what cases?
- Triple tray
- Implants
- Minimal undercuts
Addition silicones are great for what case?
- All fixed
2. All removable
What are indicates for triple tray usage?
- Single unit
- When restoring in MI
- Stable, mutually protected occlusion
- Tray does not interfere with closing
- Must have posterior stop distal to tooth
What is the goal of a final impression in fixed?
To capture the contours of the unprepared tooth apical to the preparation margin as well as all teeth in the arch and the soft tissues immediately surrounding the tooth prep
ViscoStat functions through which chemical? How does it work? Acidic?
Fe2(SO4)3 - ferric sulfate
Precipitates blood proteins on contact
Very acidic (can cause tissue damage)
Hemodent/Viscostat Clear functions through which chemical? How does it work?
Aluminum chloride
Constricts vessels and causes loss of fluid
