Effects of chlorine-based and quaternary ammonium-based disinfectants on the wettability of a polyvinyl siloxane impression material

Statement of problem. Polyvinyl siloxane (PVS) impression materials must be cold disinfected before cast pouring to prevent cross-contamination among personnel and patients. However, disinfection may affect the ability of PVS impression materials to provide bubble-free stone surfaces because of the removal of surfactants. Purpose. The purpose of this in vitro study was to compare the water contact angles of a PVS impression material treated with either a quaternary ammonium-based (QAB) (DisCide Ultra) or a chlorine-based (CLB) (Dispatch) disinfectant for various exposure times. No disinfection and acetone-immersed (total surfactant removal) specimens were used as positive and negative controls. An additional purpose was to measure changes in the contact angles of the disinfected PVS impression material after applying a topical wetting agent. Material and methods. Flat and disk-shaped PVS specimens (n=5/test condition) were fabricated and subsequently exposed to disinfectants for different times (1 minute, 5 minutes, 30 minutes, 6 hours, and 24 hours). After disinfection, the contact angle with distilled water was determined over a 3-minute period using dynamic contact analysis. The same contact angle measurements were repeated after a wetting agent was applied to the previously disinfected specimens. Contact angles were statistically compared using 2-way ANOVA. The Sidak post hoc test was used to perform pairwise simple contrast and effect comparisons (alpha=.05). Results. The contact angle increased directly with disinfectant contact time. For the CLB product, the contact angle after 30-minute disinfection was not significantly different from that of 1 minute disinfection (P>.05). For the QAB product, exceeding 5-minutes of disinfection resulted in a significantly greater contact angle (P<.001). The application of a wetting agent made the disinfected PVS specimens less hydrophobic. Conclusions. A QAB disinfectant product is more effective at removing surfactant than a CLB disinfectant product. Therefore, a CLB disinfectant provides more working time and control. A wetting agent can reduce the hydrophobicity of a disinfected impression material if the duration of cold disinfection is less than 6 hours.