Comparison of elastomeric impression materials used in fixed prosthodontics.

Five elastomeric impression materials were evaluated: two polysulfides (one lead-cure and one non-lead cure), two silicones (one condensation polymerization and one addition polymerization), and one polyether. These materials were subjected to simulated clinical conditions. Two techniques were evaluated. All materials were evaluated initially with use of a custom tray and manufacturers' adhesive. A second evaluation was performed without using the tray system. Both techniques were subjected to statistical comparison. Conclusions of the research were as follows: 1. All impression materials that were poured immediately and evaluated using a custom tray and adhesive consistently demonstrated superior results in comparison to those tested without the custom tray. 2. Polyether material consistently yielded superior results with or without a custom tray when compared to the other impression materials. The additional polymerization silicone ranked second, followed by the lead-cure polysulfide and the condensation polymerization silicone, respectively.