The tear resistance of various impression materials with and without modifiers

In this study, we measured the tear resistance of several commonly used impression materials. In the first part, a trouser-leg tear test was used to determine tear energies for 15 impression materials in three major groups (polysulfides, addition-reaction silicones, and polyethers). One brand of polysulfide demonstrated the highest tear resistance. In general, generic types of impression material could not be ranked according to tear energy. In the second part of the study, we measured the effect of the addition of a system modifier (retarder/thinner) on the tear resistance of four addition-reaction silicones and two polyethers. Retarder/thinners significantly reduced the tear resistance of five of the six materials tested.