Statement of Problem: Dentists and dental laboratory technicians’ awareness of the dangers of cross-contaminations has made them seek the best ways to control and eradicate the main sources of infections.Purpose: The aim of this study was to evaluate the effects of spraying Deconex on three different impression materials.Materials and Method: In this in vitro experimental study, 30 circular samples of different impression materials, such as alginate, silicone and polyether impression materials were separately contaminated with Staphylococcus aureus (ATCC29213), Pseudomonas aeruginosa (ATCC27853), and Candida albicans fungus (PTCC5027). Except for the control samples, all the other samples were disinfected with Deconex through spraying. Then, they were kept in plastic bags which were stuffed with humid rolled cotton for 5 and 10 minutes. In order to isolate bacteria, the samples were immersed in 2% trypsin for one hour and then the solution was diluted with normal saline in proportion of 1, ½ and 1/4. The trypsin suspensions were transferred to culture plates and the number of colonies was counted after 24 and 48 hours for bacteria and after 72 hours for fungus. Data analysis was done through running Mann-Whitney Test ( a = 0.05).Results: There was a significant difference between the effect of Deconex on silicone and its effect on polyether for all the mentioned microorganisms after 5 minutes (p <0.05). The highest percentage of bacterial growth prevention was recorded for silicone impression material. Deconex completely eradicated the three kinds of microorganisms after 5 and 10 minutes in the silicon group. Deconex was not capable to eliminate all three microorganisms in the polyether and the alginate groups; with the exception of Pseudomonas aeruginosa after10 minutes.Conclusion: The results of the present study indicated that Deconex has the highest capacity when it is used with silicone; it eradicates all microorganisms in both 5 and 10 minutes.