## 4 Discussion
acidophilus_) species, including lactic acid bacilli, in addition to the caries pathogens described above, are considered to be associated with the ECC process. These bacteria are pioneering microorganisms in the progression of the carious process, especially in dentin. Compared to our study performed on stainless steel crowns [32], where _S. mutans_ showed no adhesion to SSC steel crowns, in the case of zirconia crowns, _S. mutans_ adhered at a level of 5.25 \(\times\) 10\({}^{6}\)-8 \(\times\) 10\({}^{6}\) CFU/mL. The difference in our results may have to do with the different surfaces of the material and also the biofilm model. The biofilm on steel crowns was used in a single-species model. Single-species biofilms are typically used to evaluate adhesion to dental materials [48]. In the current study, we created a three-species _Streptococcus-Candida-Lactobacillus_ biofilm to replicate conditions more similar to those in the oral cavity. The susceptibility of in vitro biomaterial surfaces to adhesion is quite different in a multispecies environment than for a single species [49]. _C. albicans_ and _S. mutans_ show synergistic behavior in mixed biofilms [41]. In the presence of sugar, _Candida_ can form a complex biofilm and attach to _S. mutans_; thanks to carbohydrates, with the use of glucosyltransferase B, they form sticky glucans, which form a scaffold to _S. mutans_. In the natural oral environment, these microorganisms affect each other's properties, amplifying their negative effects on the tissues that create the oral environment [50]. _S. oralis_ and _C. albicans_ combined form stronger biofilms than either microorganism alone. An enhancement of _C. albicans_ invasiveness and promotion of bacterial biomass proliferation were observed in the presence of _S. mutans_[44; 51]. In our study, the observation was that both strains of _C. albicans_ used in the biofilm showed a similar level of cell adhesion to the surface of zirconia crowns at 6.25 \(\times\) 10\({}^{6}\)-1.05 \(\times\) 10\({}^{6}\). Both quantitative assessment of the adhesion ability of the strains analyzed, the formation of a mixed biofilm and the confocal microscopy results showed that the microorganism with the highest adherence is _L. rhamnus_ at a level of 3.4 \(\times\) 10\({}^{7}\)\(\pm\) 9.89 \(\times\) 10\({}^{6}\) CFU/mL for version I and 3.15 \(\times\) 10\({}^{7}\)\(\pm\) 1.41 \(\times\) 10\({}^{6}\) for version II. _L. rhamnus_ has the ability to interfere with caries-forming biofilm formation by various processes, such as through the formation of biosurfactants and a reduction in biofilm acidity [52; 53]. Figures 6-8 provide the results of the microbiological tests, while Table 2 shows the exact values of the degree of adhesion of the different microbial strains. _L. rhamnus GG_ demineralizes both enamel and dentin. In its mixed form with _S. mutans_, it induces similar or even increased demineralization compared to the action of _S. mutans_ alone [53]. [PERSON] et al. evaluated the adhesion of _S. aureus_ to the surface of tooth fragments and stainless steel fragments. The study showed that the teeth used in the study had a rougher surface and were more prone to biofilm formation, as opposed to stainless steel, which is smooth [38]. The process of biofilm formation on a surface is related to its nature and properties, such as porosity or roughness, which determine the degree of surface development. One way of influencing this parameter is the type of initial and final treatment to which the material is subjected. In the case of ceramics, the processes that strongly influence the quality of this surface are surface glazing and subsequent polishing. Both processes aim to obtain a smooth surface, which improves both the physical and functional properties of the material, such as the elimination of irregularities and fine scratches in the material, but also influences the biological properties of the surface.