## 3 Results  
### Physico-Chemical Assay Results  
The adhesion of biological materials is determined by the physico-chemical properties of the substrate, particularly its topography and wettability, but also by the chemical composition of the substrate, which determines both the nature and quality of the adhesive force. Due to the shape of the crown, which is related to the surfaces in direct contact with the enamel, the physico-chemical properties were studied for the anterior and posterior surfaces. Due to the change in curvature of the surfaces tested, differences of up to 50% in the roughness values measured both along the line (Ra, Rq) and for the surface (Sa, Sq, Sz) can be observed from the results shown in the table (Table 2). A measure of the wettability of a surface is the wetting angle \(\theta\), the angle between the wetted surface of the solid and the tangent to the surface of the wetting liquid droplet, derived from its point of contact with the surface of the solid. From the results shown in Table 2, it can be seen that these coronae are characterized by a water contact angle value of less than 90, and the surface is considered hydrophilic. \begin{table}
\begin{tabular}{c c c} \hline
**Level** & **Cytotoxicity** & **Description of Colony Changes** \\ \hline
0 & None & No changes in both the surroundings of the material and under the material \\
1 & Low & Individual cells have become degenerated or deformed under the influence of the material \\
2 & Average & The zone of affected cells is limited to the area \\  & & under the material \\
3 & Medium & The zone of affected cells is limited to 1 cm around \\  & & the material \\
4 & High & Zone of affected cells exceeds the limit of 1 cm around the material \\ \hline \end{tabular}  
According to the aforementioned standard, cytotoxic material is at least grade 2.  
\end{table} 
Table 1: Cytotoxicity degree of the test material in direct contact (PN-EN ISO 10993-5:2009). Surface roughness significantly influences the contact angle and wettability of a surface. The impact of roughness depends on whether the droplet wets the surface ridges or if air pockets remain between the droplet and the surface. Figure 2 shows images of the surface topography of the Y-ZrO\({}_{2}\) ceramic with respect to the measurement surfaces: anterior and posterior. The results show the microporosity of each surface. In addition, the anterior surface of the crown is characterized by numerous scratches and pits, which also modify the surface roughness and waviness values. It is in these areas that the crown is most likely to come into contact with the enamel of the natural tooth, which interacts with it in the occlusion. As a result of this contact, the hardness of the crown must have a lower hardness value and a higher abrasion value than that of the tooth in order to avoid abrasion of the natural tooth. This microporosity of the zirconia ceramic can also be seen in the surface images shown in the figure (Figure 3), obtained at a magnification of \(\times\)4500. Using energy-dispersive X-ray diffraction analysis (EDS), which the Phenon ProX microscope (ThermoFisher Scientific, Wlatham, MA, USA) is equipped with, the surface content of the elements Y, Hf, Zr and O, of which these crowns are composed, was analyzed. Comparing the two surfaces, it can be seen that the highly polished surface (anterior side) has a higher concentration of Zr, Hf and Y ions. The findings from our analysis of the elemental composition of the surface are in accordance with the results obtained by X-ray diffraction (Figure 4). Figure 2: Comparison of the surface topography of a dental crown obtained with the Phenom ProX Desktop SEM: (**A**) anterior side; (**B**) top of crown; (**C**) posterior side; resolution 200 \(\upmu\)m (middle), 10 \(\upmu\)m (right side).