Statement of problem.The wettability of silicone impression materials is poor, which may lead to voids within casts. All impression materials should be disinfected before use, but disinfection may affect their wettability. Purpose.This study evaluated the effect of disinfection procedures and the use of a surface wetting agent on the wettability of 4 addition-polymerized silicone impression materials. Material and methods.Testing specimens were made from 4 addition silicone materials (light-bodied President, light-bodied Extrude, medium-bodied Extrude, and Aquasil). Two disinfection solutions (Actichlor and Perform) and 1 wetting agent (Vacufilm) were used. The test conditions were as follows: (A) dry, (B) Vacufilm, (C) Actichlor (10-minute soak), (D) Actichlor (10-minute soak) and Vacufilm, (E) Perform (10 minute-soak), and (F) Perform (10-minute soak) and Vacufilm. A dynamic contact angle analyzer was used to measure the wettability of specimens. Mean results were compared with 1-way ANOVA, and multiple comparisons were made with the Bonferroni method. Results.Treatments C, D, and F had no significant effect on the wettability of the materials. Treatment B significantly reduced the contact angle for light-bodied President (P<.01) and Aquasil (P<.05). Treatment E significantly increased the contact angle for light- and medium-bodied Extrude and Aquasil (P<.001). Conclusion.Disinfection with Actichlor is recommended in preference to Perform to maintain the wettability of impression materials. Treatment with Vacufilm after disinfection is recommended to improve the wettability of materials and thus reduce the likelihood of voids within casts. (J Prosthet Dent 2001;86:165-7.)