RESUMEN
Dental impressions are routinely contaminated with varying amounts of blood and saliva. This study investigated transferability and sustainability of oral flora on irreversible hydrocolloid and elastomeric impression materials. In this experimental study a sterilized maxillary typodont was contaminated through immersing in a solution containing approximately 10[8] bacteria/ml of Staphylococcuse, Streptococcuse and Candida albicans. Impressions were taken of contaminated typodont with irreversible hydrocolloid [Bayer-iralgin], and condensational silicone [Speedex]. The impressions were rinsed with water and were placed in specific culture. The colony growth was investigated and the remainder of viable organisms was estimated. In the next stage of the study, samples were taken from impressions after 30 and 60 minutes, and 3 and 5 hours in order to evaluate the persistence of microorganisms. In the third stage, after preparing microbial suspension, the effectiveness of two different concentration of sodium hypochlorite was investigated in four different times. Kolmogrove-Smirnov, three-way ANOVA, and Tukey-HSD-served for statistical analysis. Type of impression material, time, and type of microorganisms significantly influenced the number of transmitted colonies [P=0.0001]. Also, all interaction effects were statistically significant [P=0.0001]. All tested microorganisms had grown in disinfected alginate and Speedex after immersion in 0.5% NaCIO for one minute, but no bacterial growth was observed in both alginate and Speedex after 3, 5, and 10 minutes immersion. Regarding 0.6% NaCIO, microorganisms were detected only in alginate material Bayer-Iralgin and only after one minute immersion. The results showed hydrocolloidal materials are more capable of carrying microorganisms compared to elastomeric materials specially Iralgin