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Impression materials must be disinfected to avoid cross-contamination before they are sent to the dental laboratory. However, whether aqueous state disinfectants affect material wettability is unclear.The purpose of this in vitro study was to compare the efficacy of gaseous ozone and sodium hypochlorite (NaOCl) in disinfecting light-body consistency hydrophilized polyvinyl siloxane (PVS) impression specimens inoculated with a cocktail of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Enterococcus faecalis. The effect of both disinfectants on the wettability of the material was also evaluated on uninoculated specimens.Disk-shaped specimens (N=140) were subjected to the either gaseous ozone or NaOCl for up to 30 minutes at room temperature. In the ozone group, the specimens were ozonated under a continuous stream of gaseous ozone at a concentration of 12.8 mg/L, while the specimens in the NaOCl group were immersed into 0.5% NaOCl solution. Reductions in the size of the bacterial population at the end of the exposure times were determined by the plate count technique. The contact angle measurements on the impression surface were used to determine the wettability of the specimens. Results were analyzed with 1-way ANOVA followed by the Tukey post hoc test (α=.05).The material exposed to both disinfectants for 30 minutes demonstrated a reduction in the number of bacteria of up to more than 3 log. The contact angle of water on the material increased significantly (P<.001) after only 5 minutes of contact with the NaOCl solution. However, the treatment with gaseous ozone for 30 minutes resulted in a reduced contact angle (P<.001).Gaseous ozone treatment was identified as a promising method of disinfecting polymerized PVS impression materials because of its positive effect on the wettability of the material.