To compare the linear dimensional accuracy of die prepared from gypsum materials using different mixing technique made from different

impression materials.

Materials and method:

Two hundred and forty impressions of the master die were made using polyvinyl siloxane (Group A) and alginate (Group B) impression material

with one hundred and twenty samples each. In each group thirty dies were made for a gypsum material with ten dies per mixing technique– hand

mixing, hand and vacuum mixing and vacuum mixing. The dimensions of the experimental dies were compared with the dimensions of master die

to get the linear dimensional discrepancy. The mean values were calculated and statistically analyzed using one way ANOVA and independent

sample test.

Results: The obtained value were tabulated in which the mean and standard deviations were analysed using one way analysis of variance

(ANOVA).Multiple range test by Tukey– Post Hoc test and Independent samples test was employed to identify the significant groups at 5% level. In

this study, P< 0.05 was considered as the level of significance.

Conclusion:

Ÿ Type III gypsum material (Orthokal) showed the maximum linear dimensional accuracy when compared to other gypsum materials.

Ÿ Hand mixing and hand followed by vacuum mixing techniques was better and similar in reproducing the linear dimensional accuracy of the

dies than the vacuum mixing of the gypsum material

Ÿ No statistically significant difference between polyvinyl siloxane and alginate impression material in the linear dimensional accuracy.