What is the first elastomeric impression material introduced?
Polysulfide
Introduced in 1950, originally developed as an industrial sealant.
List the four types of elastomers based on chemistry.
- Polysulfide
- Condensation polymerizing silicones
- Addition polymerizing silicones
- Polyether
What are the three types of polymerization reactions seen in elastomers?
- Addition polymerization
- Condensation polymerization
- Crosslinking
What is the viscosity classification for elastomeric impression materials?
- Type 0—Putty consistency
- Type 1—Heavy-bodied consistency
- Type 2—Medium-bodied consistency
- Type 3—Light-bodied consistency
What are the uses of elastomeric impression materials?
- Impressions for fixed partial dentures
- Impressions of dentulous mouths for removable partial dentures
- Impressions of edentulous mouths for complete dentures
- Border molding of edentulous custom trays
- Bite registration
- Making refractory casts
What is the shelf life of elastomeric impression materials?
About two years
Silicones have a slightly lower shelf life.
What are the general properties of elastomeric materials?
- Excellent reproduction of surface details
- Hydrophobic (except polyether)
- Good elastic properties
- Dimensionally stable
- Excellent tear strength
- Low adhesion to impression tray
What is the setting time for polysulfide impression material?
12.5 minutes
Setting time can be longer in colder climates.
What is the primary disadvantage of polysulfide impression materials?
- Unpleasant odor and color
- Staining
- Long setting time
- Hydrophobic
What is the composition of condensation silicone?
- Ortho ethyl silicate
- Dimethyl siloxane
- Stannous octoate (catalyst)
- Ethyl alcohol (by-product)
What are the properties of addition silicone?
- Pleasant odor and color
- Setting time of 5 to 9 minutes
- Best dimensional stability among elastomers
- Good tear strength
- Extremely hydrophobic
What are the properties of polyether impression materials?
- Pleasant odor and taste
- Good dimensional stability
- Good strength
- Hydrophilic
- Short working time
What are the techniques for making impressions with elastomeric materials?
- Multiple-Mix Technique
- Monophase Technique
What is the primary application of tray adhesives?
To retain elastomeric materials to the impression tray
Each elastomer type has a specific adhesive.
What is the chemical reaction that occurs in addition silicones?
Cross-linking between vinyl groups and silane (hydride groups)
Reaction is activated by platinum salt.
What is the effect of sulfur compounds on addition silicones?
They retard the setting of silicones
Latex gloves can be a source of sulfur contamination.
