Dimensional stability of impression elastic materials: an in vitro study

OBJECTIVE: The aim of this in-vitro study is to be able to provide useful information to implement adequate preservation of the impression before and during sending to the appropriate dental prosthetic laboratories, allowing good management of the materials used and the time spent in the chair. MATERIALS AND METHODS: The study evaluated a total of 210 specimens, of which 168 alginate specimens and 42 silicone specimens, taking a total of 18,228 measurements. The dimensional stability was assessed by measuring linear dimensions and the weight at certain time points. RESULTS: The effects within the sample group due to the time factor, the combination of time and alginate, the combination of time and environment are significantly important, both for Linear Dimension and for Weight. The effects of the factors between groups, “type of alginate” and “type of environment” are also significant. For silicones, the storage temperature and the type of mixing were not considered as factors that can influence their behavior. On the other hand, the combination of time and silicone is significant in the linear dimension, in fact the various types of silicone vary over time in different ways. Instead, the interaction between time and the type of conservation environment does not generate significant differences. CONCLUSION: This first hypothesis has been refused, the data obtained show that the various brands of alginates on the market demonstrate different characteristics of stability as a function of time. The second hypothesis was confirmed by the data obtained, in fact the impressions made with silicones can be stored at room temperature in airtight containers even up to 30 days without excessive dimensional variations.