Usama Shafiq, Shoaib Rahim, Amna Saleem, Mehrunnisa Anwari.
Effect of pouring time on the dimensional stability of alginate impression material.
Pak Oral Dental J Jan ;36(3):495-7.
The purpose of this study was to determine whether the alginate impression material produces a dimensionally accurate casts when pouring gypsum product into the impression is delayed for 1 hour or 2 hours by using specified storage conditions compared to immediate pouring. A Randomized Control Trial (in vitro experiment) was conducted in the Department of Prosthodontics, Armed Forces Institute of Dentistry over a duration of 03 months. Ninety impressions were made of a stainless steel die and were randomly divided into three groups. The 30 control group impressions were poured only after rinsing with tap water, whereas the 30 experimental group-A impressions were poured after 01 hours and 30 experimental Group-B impressions were poured after 02 hours. The dimensional change in the diameter and height of the raised column and the distance between two lines were measured in the casts of all groups. Using “Independent Samples Kruskal Wallis Test” there was significant differences (p<0.05) in the mean dimensional change (that is, Height and diameter of the raised column as well as distance between the two lines on the raised column) between 3 pouring times, that is, immediate pouring, delayed pouring after 1 hour and 2 hours. A Post-Hoc test showed that the mean dimensional changes were statistically significantly lower for delayed pouring after 1 hour and 2 hours from original die compared to immediate pouring (p<0.05). The dimensional accuracy of casts produced from alginate impression materials is time dependent. Even under specified storage conditions there was statistically significant difference in the dimensional change after 1 hour and 2 hours delay in pouring. Research is needed to compare the dimensional stability among different brands.
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