Dimensional Changes of Alginate Dental Impression Materials-An Invitro Study

Dentists are always looking ahead for more dimensionally stable material for accurate and successful fabrication of prosthesis in this competitive world. Arrival of newer materials and increased material market puts dentists in dilemma for selection of material.

The study evaluated the effect of variations in time of pour and temperature on dimensional stability of three brands of commercially available alginates.

Velplast, Marieflex & Zelgan alginate impression materials were evaluated by measuring dimensional accuracy of the master cast. A die was prepared and mounted on the apparatus for the ease of impression making. The prepared casts were categorized into five groups and made up of three brands of alginate impression material with variation in time of pour viz: immediate, 20&40 minutes interval and with varying temperature of 25(0)C, 30(0)C & 40(0)C.

Impressions showed least distortion at varying degrees of temperature for 20 minutes, but the values obtained by storing of alginate impressions for 20 minutes at 30(0)C were found to be nearly accurate than the values obtained by storing of impression at 40(0)C. However, storing showed shrinkage of impressions.

Marieflex showed better accuracy in comparison with other two materials. Maintenance of temperature and humidity play key role during storage & transport to prevent distortion. But the study suggests immediate pouring which will minimize the distortion. The manipulation instructions, temperature of mixing water, environment & water powder ratio also plays key role in minimizing the distortion.