Polyvinyl Siloxane

Very stable impression material. Available in multiple viscosities. Polyvinyl siloxane (PVS), also called poly-vinyl siloxane, vinyl polysiloxane (VPS), or vinylpolysiloxane, is an addition-reaction silicone elastomer (an addition silicone). It is a viscous liquid that cures (solidifies) quickly into a rubber-like solid, taking the shape of whatever surface it was lying against while curing. As with two-part epoxy, its package keeps its two component liquids in separate tubes until the moment they are mixed and applied, because once mixed, they cure (harden) rapidly. Polyvinyl siloxane is widely used in dentistry as an impression material.

Polyether

Polyethers are presented as a base and activator paste of the same viscosity. Unlike the silicone impression materials, polyethers are only available in one viscosity and are therefore an example of a monophase impression material; the same viscosity material is syringed around the tooth preparation(s) as is loaded into the impression tray.

Polysulfide

An elastomeric impression material with a polysulfide base and a lead-sulphur activator that forms rubber on polymerization. Advantages of polysulfide impression materials are low cost, long working time, and high strength, flexibility and accuracy. Disadvantages are low dimensional stability (requiring custom trays), bad odor and long setting time.

Hydrocolloids

Among the oldest dental impression materials still in use, reversible hydrocolloid impression materials are formulated with agar and effectively solidify from their liquid state to a solid gel state in the mouth to capture a highly accurate impression. These materials are temperature sensitive, changing from liquid to solid at different temperatures, so they are often used with special water-cooled trays in order to capture the most accurate impressions. Because of the reversible nature of these materials, models should be poured immediately after the impression is taken. These materials work well because of their natural hydrophilicity and the fact that the material does not need to be mixed prior to being added to the impression tray. While these materials can be easy to use, it is usually only possible to pour one model per impression, which means reversible hydrocolloids need to be used under proper conditions and models must be created immediately after the impression is captured.