Detail Reproduction of Three Elastomeric Impression Materials Using Different Models

OBJECTIVES: To measure and compare in vitro detail reproduction of three medium bodied elastomeric impression materials employing bovine enamel & dentin models and the standard ADA stainless steel die under dry and wet conditions. The null hypothesis was that detail reproduction of the impressions will not differ with the model type or in wet or dry conditions.

METHODS: Impressions, using a poly-vinyl siloxane (Aquasil), a polyether (Impregum) and a polysiloxane-polyether hybrid (Senn), were made under dry and wet conditions of bovine enamel & dentin models and the standard ADA die scored with horizontal lines of dimensions 20um, 50 um and 75um respectively, as recommended in ANSI/ADA Specification 19. A thin, uniform layer of artificial saliva was painted on each model prior to impression making in wet environment. All the three models and their impressions were scanned using a non-contact surface profilometer (Proscan 2000, Scantron, UK) to measure the line widths and heights. Superimposition of impression scans over model scans was done to evaluate height and width differences, which were compared using the GLIMMIX procedure followed by Tukey's post-hoc comparisons.

RESULTS: The three line widths and heights differed significantly among models (p<0.0001) & conditions (p<0.0001). No significant differences were seen for detail reproduction between the impression materials under dry conditions. Under wet conditions, impressions of bovine models differed significantly from their dry counterparts (p<0.0001). Aquasil reproduced detail reproduction as well as Impregum (p=0.6953) while Senn fared significantly worse. Overall, surface detail deteriorated when the mold was wet.

CONCLUSIONS: Even though hydrophilic elastomeric impression materials are used clinically these three representatives from three different classes of materials could not produce accurate detail reproduction from a wet bovine or wet stainless steel model.