Dimensional Accuracy and Surface Detail Reproduction of Hydrophilic Polyvinylsiloxane Impression Material Tested under Dry and Moist Salivary Conditions: An In vitro Study

Background: The dimensional accuracy and surface detail reproduction of impression materials play a major role in determining the extent to which indirectly produced prostheses and restorations have an acceptable fit. The purpose of the present study was to compare the dimensional accuracy and surface detail reproduction of hydrophilic polyvinylsiloxane (PVS) impression material tested under dry and moist salivary conditions. Methods: The study samples were assigned two groups based on the condition in which they were made. One group consisted of casts obtained from impressions made in dry condition (n = 12), while the other group consisted of casts obtained from impressions made in moist salivary conditions (n = 12). Impressions of the master model were made using hydrophilic PVS impression material by two-step putty-wash technique and working casts were obtained. Dimensional accuracy was measured by comparing the inter-abutment distance in each cast to the master model using a profile projector with an accuracy of 0.001 mm, while surface detail reproduction was evaluated using the American Dental Association specification No. 19 criteria of continuous replication of at least two of the three horizontal lines. Descriptive statistics such as mean and standard deviation were calculated for both the groups. Differences from the master model were analyzed by paired t-test, while one-way analysis of variance (ANOVA) was used for intergroup comparisons. P <= 0.05 was considered statistically significant. Results: One-way ANOVA revealed a highly significant difference in the dimensional accuracy of impressions made under moist conditions as against those which were made under dry condition (P < 0.001). The percentage change in dimension of 0.6% in Group A casts and 0.3% in Group B casts, also, showed a high clinical significance. Under dry condition, the impression material satisfactorily replicated the surface details in 100% of the cases, while under moist conditions, only 58% of the impressions were found to be satisfactory. Conclusion: The presence of moisture caused a significant adverse impact on the dimensional accuracy and surface detail reproduction of hydrophilic PVS impression material underlying the clinical significance of moisture control for successful impressions.