Objective: Oral rehabilitation success is enhanced by an accurate and reproducible final impression. The purpose of this study is to evaluate the dimensional changes of a polyether and addition silicone subjected to disinfection and/or sterilization after a long storage period.Material and methods: Ninety samples were obtained from polyether Impregum~(TM) Penta~(TM) (3M ESPE~(TM), Seefeld, Germany) and 90 of addition silicone Imprint~(TM) 4 Penta~(TM) Putty (3M ESPE~(TM), Seefeld, Germany) according to ISO 4823:2000. The samples of each material were split to form three groups with 30 samples each: a control group, a hypochlorite group (disinfection) and an autoclave group (sterilization). Samples were stored in the Portuguese Institute for Quality for six months at 23?°C. Samples were measured by laser interferometry, according to the Michelson technique before calculating dimensional stability according ISO 4823:2000. A statistical analysis via a three-way mixed ANOVA was performed.Results: Significant shrinkage of Impregum~(TM) Penta~(TM) was 0.77?±?0.17% in the control group, 0.42?±?0.19% in the hypochlorite group and 0.52?±?0.28% in the autoclave group. For Imprint~(TM) 4 Penta~(TM) Putty, the control group had a shrinkage of 0.42?±?0.12%, the hypochlorite group 0.36?±?0.09% and the autoclave group 0.59?±?0.13%.Conclusions: The long-term storage of samples subjected to disinfection with 5.25% hypochlorite or autoclave sterilization can be used in a clinical setting as the dimensional changes are below the maximum permitted by the ISO 4823:2000, since there are no clinically significant changes in the dimension of the samples during the storage period.
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