Setting Characteristics of Alginate Impression Materials

In order to obtain an accurate impression, it is important to determine the working and setting time of impression material. The determinations of the working and setting time, by assessing elastic recovery than any other properties of impression materials, are more realistic and critical. The authors introduced the pulsating rheometer as an instrument for measuring changes in elastic recovery during setting. The purpose of this investigation is to measure the amount of elastic recovery during setting and to determine the working and setting time of commercial alginate impression materials. Zelgan, Algifit new mix, Orthojel and Algipaste had short working time. These materials must be worked as quickly as possible after mixing. The setting times of alginate impression materials used in this investigation were shorter than those of elastomeric impression materials. The values of elastic recovery at the setting time of all materials tested, except Orthojel, were 95 to 98%, which were lower values compared with those of elastomeric impression materials. The elastic recovery of alginate impression materials deteriorated as the duration of strain increased.