Comparative Study of Dimensional Stability and Detail Reproduction of Reformulated and Nonreformulated Elastomeric Impression Materials.

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To evaluate the dimensional stability and the detail reproduction of five current elastomeric impression materials in vitro. The materials examined were: 3 different polyether impression materials, a vinyl polysiloxane impression material, and a vinyl polyether silicone impression material. All impression materials were of a medium viscosity. One stainless steel die was fabricated according to the ANSI/ADA specification no.19 criteria. Twenty impressions of this die were made for each material. Dimensional accuracy and surface detail were evaluated 24 hours after making the impressions using a measuring microscope. The data were analyzed using Welch's analysis of variance, Games-Howell Post-Hoc, and the Pearson's chi-square tests (α = 0.05). Statistical differences were observed in the mean percent dimensional stability (F [4,47] = 39, p < 0.001) of the tested impression materials. The highest dimensional change was recorded for the vinyl polysiloxane impression material, with a mean percent value of -0.09 ± 0.02% (p < 0.001). The lowest dimensional change was recorded for the Monophase polyether material with a mean percent value of -0.03 ± 0.01% (p < 0.038). The best surface detail reproduction results were obtained using the Monophase polyether material (90% acceptable impressions), with no significant differences (χ² [4] = 3.86, p = 0.483) observed between the Monophase and the rest impression materials. All materials exhibited acceptable dimensional stability, well below the ANSI/ADA specification no.19 standard of ≤0.5% dimensional change. All impression materials demonstrated acceptable surface detail reproduction with no significant differences between them.