## 4 Discussion  
The most common method of impression disinfection is the chemical method, due to its simple applicability. The chemical-agent efficacy is influenced mainly by the type and \begin{table}
\begin{tabular}{c c c c} \hline  & **Zeta 7 Spray vs.** & **Zeta 7 Spray vs. Zeta** & **Zeta 7 Solution vs.** \\  & **Zeta 7 Solution** & **3 Soft** & **Zeta 3 Soft** \\ \hline \multicolumn{4}{c}{_p Value_} \\ \hline Tropicalgin & 0.0329 * & 0.0329 * & \textless{}0.0001 *** \\ \hline Zetaplus & 0.0746 & 0.0206 * & \textless{}0.0001 * \\ \hline Oranwash L & 0.0288 * & 0.0288 * & \textless{}0.0001 * \\ \hline Elite HD + Putty Soft & 0.601 & 0.0041 ** & \textless{}0.0001 * \\ \hline Elite HD + Light Body & 0.323 & 0.0039 ** & \textless{}0.0001 * \\ \hline \end{tabular}
* significant, ** very significant, *** extremely significant.  
\end{table} 
Table 6: The comparison of the results of the disinfection efficacy between the three used disinfectants. Figure 6: The number of microbial colonies for all impression materials before and after disinfection. the number of microorganisms, the concentration and the action time of the disinfectants, and the impression material for which it is used [15]. It is recommended that to label the impressions sent to the dental laboratory, dentists inform the dental technician about the disinfection status. This is to control the cross-infections, and avoid multiple disinfections, which can compromise the dimensional stability and the surface characteristics of the materials [16]. Several studies demonstrated that simply washing the silicone impression with water does not effectively reduce the microbial load of the material surface, and is not suitable for preventing cross-infections [17; 18]. Our findings are in concordance with this research. For disinfection, alcohol, sodium hypochlorite, and glutaraldehyde-based disinfectants are more effective. The disinfection of alginate and polyvinyl-siloxane impressions with these disinfectants will result in adequate disinfection without compromising the quality of the materials [18; 19]. [PERSON] et al. demonstrated that Indian dental technicians have insufficient knowledge about contamination possibilities through impressions [20]. [PERSON] et al. recommend education programs for dental technicians concerning the importance of impression disinfection [6]. Our results demonstrate the efficacy of the two examined, specific disinfectants (Zeta 7 Spray and Zeta 7 Solution) in reducing the number of microbial colonies on the impression material's surface. According to our results, for two impression materials (Oranwash L and Tropicalgin), the Zeta 7 Solution is more appropriate for eliminating surface microorganisms. In the case of the other impression materials used, no significant differences were recorded between the action of the Zeta 7 solution and the Zeta 7 Spray. In a similar study to ours, conducted by [PERSON] et al., the antimicrobial efficacy of UVC radiation, gaseous ozone, and liquid chemicals used to disinfect silicone dental-impression materials was evaluated. In this study, the C-silicone used was Oranwash L, Zetaplus, and A-silicone Panasil (putty, medium, light). A mixture of three microbial strains for sample inoculation, _P. aeruginosa_ ATCC 27853, _S. aureus_ ATCC 6538, and _C. albicans_ ATCC 10231 (ATCC, Manassas, VA, USA) was used. The chemical solutions used for disinfection were Zeta 7 solution and Zeta 7 spray. The reported result was in accordance with ours, in that all disinfection methods evaluated were effective against selected oral pathogens (_P. aeruginosa, S. aureus, and C. albicans_) which were used to contaminate both types of C-silicone [21]. The Zeta 7 Solution, based on quaternary ammonium salts, reduced almost entirely the microorganisms load from the impressions surfaces; in the case of Oranwash L and Elite HD+ Light Body, no microorganisms were found on the culture media. According to [PERSON] et al.