Comparison of Elastomeric Impression Materials

Requirements for Materials Used in Complete Dentures

• A key requirement for materials used to make complete dentures is that they should have adequate wettability of oral tissues.

Prosthodontic Impression Materials

• The requirement that is NOT needed for prosthodontic impression materials is high strength.
• Type I compound refers to a material used for border molding.
• A desired mechanical property for materials used in complete dentures is the ability to set into a rubbery/rigid solid in a reasonable amount of time.

Impression Materials' Properties

• A key factor for an impression material's shelf life is the storage conditions.
• Adequate wettability of oral tissues is necessary for impression materials to ensure proper flow and adaptation.
• The property essential for preventing tears during removal of prosthodontic impressions is high tear strength.
• Impression materials should set into a rubbery/rigid solid in a reasonable amount of time to ensure accurate impressions.

Type I Compound

• The main function of wax spacer when using Type I compound for border molding is to create a space for the impression material.

Polysulfide Polymer

• The principal ingredient of the Base o Polysulfide polymer is polysulfide.
• The material used as a plasticizer for viscosity in the Base o Polysulfide polymer is dibutyl phthalate.
• The function of oleic or stearic acid in the Base o Polysulfide polymer is to act as a surfactant.
• Titanium oxide and Zinc are used as opaque fillers in the Base o Polysulfide polymer paste.
• Lead dioxide, hydrated copper oxide, or organic peroxide play the role of catalysts in the Accelerator/Reactor of Polysulfide polymer.

Addition Silicones

• The component used as an initiator in Addition Silicones is platinum.
• The function of oil-based diluents in Addition Silicones is to reduce the viscosity of the material.
• The component that thickens the accelerator paste in Addition Silicones is silica.
• The cast can be poured up to 24 hours after making the impression for Addition Silicones.

Elastomeric Impression Materials

• Latex gloves inhibit polymerization of some elastomeric impression materials.
• Polyether Elastomer has the highest flow rate among elastomeric impression materials.
• Silicone impressions can distort from heat and chemicals.
• A disadvantage of using Polysulfide Rubber (Mercaptan) as an elastomeric impression material is its unpleasant odor.
• The WT (working time) is 2.5 minutes for a specific material mentioned in the text because of the combination of its base and catalyst.
• Condensation Silicones require a custom tray for usage.
• Air incorporation and contamination can cause stone imperfections.
• A common disadvantage shared by Condensation Silicones and Polyethers is their high permanent deformation.
• Polyethers are known for having high stiffness and being hard to remove.
• Addition Silicones are hydrophobic, making them difficult to pour in stone.
• Silicone impressions have a unique characteristic of being resistant to distortion.
• Condensation Silicones are described as having 'Low Flow rates'.
• Impressions must be poured ASAP within 30 minutes-1 hour to prevent distortion and inaccuracy.
• A key property of Addition Silicones that makes them stand out is their high precision and accuracy.
• Silicone impressions can be damaged by heat and chemicals.
• Polyethers are not suitable for pouring in stone due to their high water absorption and subsequent expansion.
• The flexibility of a material is impacted by the molecular structure and the degree of cross-linking.
• Among the listed elastomeric impression materials, Polyethers have the highest tear strength.
• A drawback of materials with low tear strength is that they are prone to tearing during removal.
• Condensation Silicones have a lower viscosity and have a tendency to flow down the throat when used.