## 3 Results and Discussion
### Antimicrobial Activity  
The new formulations under study have passed all normative tests, being suitable for dental impression materials. At this point, all qualified for the last stage of the study, i.e., the antimicrobial activity investigation. For this purpose, the _Streptococcus mutans_ strand was used, a strain of bacteria commonly known for naturally habituating the oral cavity and being the main reason for _Caries dentin_. Three samples of alginate material containing 0.25-1% silver-based ceramics were made for testing. These concentrations were determined based on the information provided by the material manufacturer, who recommends using this raw material at a concentration of 0.05-1%, and the work of [PERSON] [29]. Figure 10 shows the degree of antibacterial activity that changes with increasing AlphaSan loading in the alginate material, compared to Kromopan. When the additive content was 1%, the antibacterial inhibition zone for _S. mutans_ was the largest and reached 4.5 mm. For the control sample (agar only), there was no inhibition zone present. For alginate Krompan, this value was 1 mm. This effect may be related to the ingredients contained in alignates, phosphates, and potassium fluorotianate, which decomposes in contact with water, releasing small amounts of hydrofluoric acid. For the composition studied, a higher AlphaSan loading causes an increase in the concentration of silver ions, resulting in a higher ion gradient between the alginate gel and agar, silver ion migration, and an increase in the inhibition zone, where the growth of microorganisms is observed. There are many scientific reports that are based on the effectiveness of silver in various forms as a bactericidal or bacteriostatic agent. Because of a large surface-to-volume ratio, silver nanoparticles exhibit remarkable antimicrobial activity, even at a low concentration. In addition, they are inexpensive and have shown low cytotoxicity and immunological response. The mechanism of the bacteriostatic action of silver ions has been presented in the literature. This is due to the fact that silver cations are attracted by the removal of charged sulphide anions present in the structure of proteins. The adhering ions are then responsible for increasing the permeability of the cytoplasmic membrane, which consequently leads to the disruption of the bacterial envelope. In the next stage, free silver ions are absorbed into the cells, which deactivates respiratory enzymes, producing reactive oxygen species, and disrupts the production of adenosine triphosphate. Reactive oxygen may be the main factor causing disruption of the cell membrane and modification of deoxyribonucleic acid (DNA). Since sulphur and phosphorus are important components of DNA, the interaction of silver ions with these two elements can cause problems in DNA replication, cell reproduction, and even result in the extinction of microorganisms. Moreover, Ag\({}^{+}\) ions can inhibit protein synthesis by denaturing ribosomes in the cytoplasm [44; 45]. Silver (and especially its nanoparticles) was also used as a bacteriostatic agent by other authors [21; 25], in specific concentration ranges from 0.1% to 5%. In the case of [PERSON] et al. [25], the concentration of nanoparticles was 0.1-0.2%. Therefore, the authors obtained smaller inhibition zones for this type of material than in the case of 0.25 CHX. According to [PERSON] et al. [21], silver ions have a strong bactericidal effect in diffusion tests and also extend the binding time of the material. This was confirmed in our tests. However, the use of silver nanoparticles causes the alginate material to change colour to grey. In our case, the use of silver-based ceramics, which are white, does not change the colour of the impression material. The addition of AlphaSan, described in the literature, was effective for the burn treatment material. [PERSON] proposed that silver ions can be released from material through various mechanisms and act as bacteriostatic agent.