In vitro study of the number of surface defects in monophase and two-phase addition silicone impressions

Monophase addition-cured silicone impression materials in stock trays are considered to be alternatives to two-phase systems used with custom trays.

This study compared the number of surface defects in addition-cured silicone impressions recorded with monophase materials in stock trays and two-phase impressions in custom trays.

The number of voids visible on the surface of impressions recorded in vitro were counted. Two monophase impression materials. (President Monobody system 75, Bayer Cutter) in stock trays were compared with impressions recorded with two-phase addition silicone materials (President Plus light-body/regular-body and Zhermack Elite light-body/medium-body) in custom trays. A total of 200 automixed impressions, 50 with each material, were recorded of 50 dentoform molar teeth prepared for full veneer crowns. Impressions were examined for surface voids anywhere on the prepared part of the tooth by a trained examiner.

Mean number of voids observed for the monophase impressions were 3.0 +/- 2.2 for President Monobody system and 3.4 +/- 2.0 for Bayer Cutter system. Mean number of voids for the two-phase materials were 0.8 +/- 1.0 for President Plus, and 1.0 +/- 1.1 for Zhermack Elite. No significant differences were observed for number of voids between the monophase materials or between the two-phase systems (ANOVA and Neuman-Keuls p > 0.05). However, both two-phase materials in custom trays had significantly fewer surface voids than the two-monophase materials (ANOVA and Neuman-Keuls, p < 0.001) used in stock trays.

Monophase addition-cured impression materials in stock trays carries an increased risk of void formation on the surface of the impression when compared with two-phase addition silicone materials in custom trays.