Background:
For many years, alginate masses have remained the most frequently chosen impression materials in the initial stages of treatment due to their numerous advantages, such as ease of insertion and removal from the oral cavity or low cost of the material. In recent years, alginate masses called "extended-pour" have appeared on the dental market, allowing to make a plaster models even after a few days.

Aim:
The aim of the study was a three-dimensional evaluation of extended-pour alginate impressions depending on the environment and storage time.

Material and methods:
Series of three-dimensional images of forty impressions made of high dimensional stability alginate have been tested. The scans were divided into groups depending on the conditions of storing the impressions. The three-dimensional images were superimposed using graphic software and the deviations were calculated. Data in the form of 5600 deviation values were subjected to statistical analysis.

Results:
The lowest mean values ​​of deviations in the 24 hours of the study were obtained for the group kept in a double-zipped bag at room temperature without the presence of an external source to increase humidity. The highest mean deviations were obtained at 144 hours of study for impressions stored in a double-zipped bag at the temperature of 5°C without the presence of an external source of humidity.

Conclusions:
The storage time and environment affect the spatial dimensions of the high dimensional stability alginate impressions. The presence of an external source of humidity during the storage of the alginate impressions does not significantly improve the dimensional stability.