## 4 Discussion  
The human oral cavity offers a unique environment for microorganisms to form complex biofilms. It hosts several hundred species of microorganisms, including bacteria, fungi, protozoa, and viruses [36]. The first stage of biofilm formation in the oral cavity is for free-living microorganisms to adhere to the surface and cover it with an acquired membrane (pellicule) [37]. This includes both natural structures (enamel, dentin, mucosal epithelium) and restorative or prosthetic materials (implants, dental fillings, crowns) [37]. Through simple chemical bonds (van der Waals forces, electrostatic and Lewis electron forces), gravitational forces, and surface tension, microorganisms begin to adhere to the membrane surface. Bacteria bind to the membrane within the first few hours after brushing teeth. Priority is given to \"early colonizers\", which include bacteria of the genus _Streptococcus_, _Eikenella_, _Streptococcus_, _Neisseria_, and _Haemophilus_. \"Late colonizers\" attach to pioneer bacteria to form coaggregates. Such abilities are attributed to bacteria of the genera _Eubacterium_, _Actinomyces_, _Prerotella_, _Porphyomonas_, and _Fusobacterium_[38; 39; 40; 41]. A biofilm is an organized cluster of bacteria and fungi, characterized by numerous synergistic and antagonistic interactions that create microbial interdependencies and confer resistance to external factors [42; 43]. In the oral cavity, biofilm plays a significant role in the development of caries, gingivitis, and periodontitis [44]. Although biofilm formation on dental \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Material** & **Sample Number** & **Description of Morphological Changes in Cell Culture** & **Evaluation of Changes in Cell Culture** & **Cytotoxicity** \\ \hline \multirow{4}{*}{Zirconia} & & Changes in the morphology of the cells with the tested material & & \\  & & (rounded cells, shrunken cells, & \\  & & & stunted growth of the culture); & 2 & Moderate \\  & & & near the sample up to 1 cm and in the rest of the culture, cell & & \\  & & & morphology normal & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Cytotoxicity degree of the test material in the direct contact (PN-EN ISO 10993-5:2009). Figure 9: Morphological image of Balb/3T3 fibroblasts after 24 H incubation with dental crown, from left to right: control culture without contact with tested material; 1 cm from the edge of the specimen; more than 1 cm away from the specimen; at the edge of the sample; under the specimen; further away from the specimen. Magnification 100\(\times\). biomaterials may appear harmless, it poses risks similar to those of periodontal disease and peri-implantitis [39; 45]. Biofilm formation around dental fillings can lead to secondary caries [39]. Therefore, there is a significant need for innovative materials that minimize bacterial adhesion to their surfaces [32]. Developing artificial dental materials with reduced bacterial adhesion is crucial for maintaining oral health [40]. Zirconium (zirconium oxide) was introduced by [PERSON] in 1789. It is distinguished by its lack of cytotoxicity and anti-adhesive properties regarding bacteria [46]. The aim of our study was the formation of three species of biofilms on the surfaces of zirconia crowns. We investigated the in vitro adhesion abilities of _Streptococcus mutans_, _Candida albicans_ and _Lactobacillus rhamnosus_. _S. mutans_ was chosen in our study because it is commonly associated with dental caries and periodontitis [41]. Moreover, placing the crown in the mouth creates a new niche for the adhesion of _S. mutans_, among other microorganisms, which plays a crucial role in the development of secondary caries on the cemented tooth. In the long term, this may impact the clinical success of the restored tooth [33]. _Candida albicans_ is often isolated along with S. mutans from carious lesions in children with severe early childhood caries (ECC) [47]. The Lactobacillus (_Lactobacillus casei_, _L. rhamnus_, _L.