1988 Volume 7 Issue 6 Pages 861-874
The dimensional changes of two types of alginate impression material in air, 100% relative humidity and water were measured by means of an electronic micrometer with a non-pressure method.The effects of impression thickness, impression diameter and retentive conditions of impression with a tray were examined.The effects of three factors examined were all statistically significant as determined by an analysis of variance.The effect of impression thickness was particuraly great.The minimum impression thickness resulted in the minimum dimensional change.When the impression diameter was minimal, the contraction in air increased.A high expansion in water was observed in the absence of a tray.The number and diameter of the retentive hole in the perforated tray had little effect.These findings indicate that the alginate impression of 2.5〜5mm thickness and maximum diameter(width)ratained with a perforated tray will provide the best dimensional stability.
