Moisture Effect on Elastomeric Impression Dimensional Accuracy and Detail Reproduction

Objective: To evaluate dimensional accuracy and surface detail reproduction of recently marketed impression materials under dry and moist conditions. Evaluated materials included reformulated automix polyether (PE, ImpregumSoft), vinyl polysiloxane (VPS, AquasilUltraXtra) with claims of hydrophilicity similar to PE, hybrid vinyl polyether silicone (VPES, Exa'lence) purportedly exhibiting PE hydrophilicity and VPS ease of handling. Methods: Using ANSI/ADA specification 19 protocols, 30 impressions of stainless steel dies were made with each material under dry, water, and saliva substitute conditions (10 impressions/condition/material). Dimensional accuracy was evaluated according to specification 19. Surface detail reproduction was evaluated in two ways: (1) continuous replication of at least two of three horizontal lines, (2) smooth surface quality based on surface texture and presence of pits/voids. Results: Conditions (dry, water, saliva substitute) did not cause significant adverse effects (p≥0.05) on dimensional accuracy of any material. Mean dimensional change ranged from -0.125±0.033% to 0.060±0.034%. With both surface detail analyses, there was a significant effect of condition on each material (p<0.05). Under dry and water conditions, all materials replicated 2 of 3 lines 100% of the time; with saliva substitute, 20% VPS, 10% PE, 0% VPES impressions exhibited satisfactory line replication. For the smooth surface evaluation, 100% of the impressions were satisfactory under dry conditions. With water, 100% VPS, 60% PE, 30% VPES impressions produced satisfactory surfaces; with saliva substitute, all materials produced unsatisfactory surfaces 100% of the time. Conclusions: Moisture did not adversely affect dimensional accuracy of any of the newly introduced impression materials. Overall surface detail reproduction varied depending on whether water or saliva substitute was used; with water, VPS performed better than PE or VPES. With saliva substitute, surface detail was poor for all materials due to a possible surface interaction with the materials; as a result, saliva substitute appears to be inappropriate for impression material testing.