effect of pouring time and storage temperature on dimensional stability of casts made from irreversible hydrocolloid

objective: the aim of this study was to evaluate the dimensional stability of casts made from an alginate impression material poured immediately and stored after specific periods. materials and methods: the common alginate used in iran (super; iralgin, golchai co., tehran, iran) was tested. a master model was mounted on a special device and used to obtain the impressions. these impressions were stored at 23°c (sd=1) and 4°c (sd=1) in 100% relative humidity, then poured with gypsum immediately and again after 12, 25, 45 and 60 minutes. the casts were measured with a traveling microscope with the precision of 0.5 micrometer. results: the dimensional stability of the alginate and impressions were both significantly time and temperature dependent. the impressions were dimensionally stable significantly until 12 minutes of storage at room temperature and until 45 minutes of storage at 4°c (sd=1). conclusion: the dimensional stability of the alginate impressions was influenced by the storage time and environment temperature, but a humid environment and 4°c (sd=1) temperature may delay the pouring.