Clinically Relevant Application Times of Impression Materials

In-vitro testing of hydrophilicity or rheological properties of impression materials during setting is usually done at certain time points during working time. E.g. hydrophilicity is often measured 30 s after mixing. In order to enhance the clinical relevance of future data, that are used to improve the materials wetting or flow properties, the time course during clinical application of impression materials was thoroughly analyzed with a main focus on the time from start of mixing until the contact of the regular body material with the abutments.

Methods:

Working times of 86 clinical cases (48 different patients treated by 14 different clinicians) were measured and analyzed using Impregum Penta as type 2 and Permadyne Garant 2:1 (3M ESPE) as type 3 with the one–step technique. In all, 69 natural abutment teeth, 15 implants, and 2 implants/natural abutment were included. The times measured include the clinically relevant time from the loading of the impression tray until the first contact of the regular material with the abutments. Differences between clinicians for their times needed for impression taking were calculated applying the Wilcoxon-test (p<0.05).

Results:

The median time (n=86) from the loading of the impression tray until the first contact of the regular material with the abutments was 46.5 s, the 10th and 90th percentiles were 24.1 s and 78.0 s, respectively. The time of impression taking was significantly dependent on the respective clinician (p<0.001). Thus, the real working time is longer than the times often used in in-vitro tests.

Conclusion:

Our data show, that nearly 50 s pass by at statistic average until the regular body material contacts the abutments, i.e. the relevant working time. Therefore, future in-vitro studies of hydrophilicity or flow properties during working time should consider these clinically relevant application times.