## 4 Discussion
[22] and [PERSON] and [PERSON]'s research [23], immersion in disinfectant is one of the safest disinfection methods. Their literature states that the porosity of dental-impression materials leads to the penetration of microorganisms. By using the spraying method, the disinfectant cannot reach the entire surface of the impression. In most cases, the microorganisms penetrated through the porosities of the material into the deeper layers and will remain inside the impression material. On the other hand, [PERSON] et al. demonstrated that using Zeta 7 Spray is the most effective disinfection method for the impression materials contaminated with _Pseudomonas aeruginosa_[24]. The tested solutions were effective in the case of alginate impressions. The immersion of the impressions resulted in a higher microbial reduction, as [PERSON] et al. demonstrated in their study [25]; similar results were obtained in our study. The microorganisms on the surface of the dental impressions were reduced almost completely, when using the immersion-disinfection method. Ten minutes of immersion time did not affect the dimensional accuracy. After this period, the alginate impression must be immediately poured [26]. Some dentists avoid immersion because they believe that the impression will no longer have dimensional stability. According to [PERSON] et al., immersing an alginate impression in a disinfectant solution for 10 min does not affect the dimensional stability of the material [26]. More bacterial colonies were found on the surface of the condensation-silicone specimens, compared to the polyvinyl-siloxane specimens for each disinfectant used. This is probably due to a higher porosity of the material, which allows a deeper penetration of the microorganisms, where the disinfectants cannot act with high efficacy. A difference was also noticed between the number of colonies found on the surface of the light body compared with the putty consistency from the same type of silicone. This is probably due to the higher porosity of the putty materials, compared to the light-body ones. The infection control for polyvinyl siloxane materials can be done without considerable dimensional changes by autoclaving. The pouring of the casts must be delayed by 24 h to gain compensatory expansion [27]. Several studies demonstrated the dimensional stability of the addition silicones after a shorter immersion period than 60 min in 2% glutaraldehyde, sodium hypochlorite, or phenol solutions [27]. A chemical disinfection with 2% glutaraldehyde will result in more considerable dimensional changes than autoclaving [28]. [PERSON] et al. reported maximum stability after using different disinfectants for the heavy-body polyvinyl-siloxane impression materials [29]. Zeta 3 Soft spray is not adequate for impression disinfection; a high number of bacterial colonies were found on the surface of all impressions disinfected with this spray. Disinfecting the impressions with Zeta 3 Soft spray leads to a high risk of cross-contamination. An in-vivo study conducted by [PERSON] et al. showed that water wash reduced the microbial load by 11.7% (with no statistical difference). In comparison, all the other disinfectants used in the study reduced the microbial load by more than 99.9% [17]. Similar results were obtained in our in vitro study. In in vivo research conducted by [PERSON] et al., the results indicated that freshly prepared electrolyzed-oxidizing-water is a very effective method to reduce the microbial load (the microbial-reduction rate was 100%) in the case of addition-silicone impressions [30]. New ultraviolet disinfection-methods can be used to disinfect impressions without compromising their dimensional stability [23]. Gaseous-ozone treatment is also a promising method for disinfecting polyvinyl-siloxane impressions, which can increase the wettability of the material [31].