Effect of Disinfection on the Surface Roughness of Dental Casts Retrieved from Addition Silicone Impressions

Background and aim: Changes in the physical properties of casts retrieved from disinfected impressions are a common problem in the fabrication of dental prostheses. However, there are limited data available about the effect of disinfecting solutions on the surface roughness of casts. This study aimed to assess the surface roughness of casts retrieved from addition silicone impressions disinfected by immersion in three different disinfectants for 5 and 30 minutes. Materials and methods: This in-vitro experimental study was conducted on 49 casts in 7 groups (n=7). A standard stainless steel die was used according to ANSI/ADA specification no. 25, and impressions were made using a low-viscosity addition silicone impression material. The impressions were disinfected by immersion in 1% sodium hypochlorite (NaOCl), 2.4% glutaraldehyde, or 5% povidone-iodine for 5 and 30 minutes. All impressions were poured with type IV dental stone, and their surface roughness (Ra) was measured using a digital hand-held roughness tester. Data were analyzed using two-way analysis of variance (ANOVA) and Tukey's test. Results: One-way ANOVA showed a statistically significant difference between the control group and the other 6 groups (P=0.004). 1% NaOCl/5 minutes was the only group which presented a different result from the control group (P=0.012). Two-way ANOVA showed that over time, the surface roughness of casts retrieved from silicone impressions disinfected by immersion in a disinfectant decreased (P=0.002), but no significant difference was noted between the disinfectant agents (P=0.243).  Conclusion: The type of the disinfectant had no significant effect on surface roughness, although an increased duration of disinfection decreased the surface roughness of casts.