## 2 Materials and Methods
The following roughness parameters were used to evaluate the surfaces:  
* The Ra parameter evaluates the average of the peaks and valleys on the scanned surface within the evaluation length;
* The Rz parameter evaluates the average height between the five highest peaks, as well as the average depth between the five lowest valleys, on the scanned surface;
* The Rt parameter evaluates the difference between the height of the highest peak and the depth of the deepest valley within the evaluation length. To determine the surface roughness of the samples and the differences between the processes to which they were subjected, the Hommel-Etamic Nanoscan 855 Jenoptik, Vienna, Austria equipment presented in Figure 1 was used. The Hommel-Etamic Nanoscan 855 has a resolution of 0.6 nanometers on a 20 mm measuring range. The investigated roughness parameters were evaluated for each individual sample. To collect the profile, the sample was fixed to the table of the equipment and assessed using a probe with a 2 um tip and a scanning speed of 0.25 mm/s. The equipment used to perform SEM analyses to provide information on film morphology (shape, size, and size distribution of crystallites) was a TESCAN VEGA, Kohoutovice, Czech Republic, having the following characteristics: energy--200 eV-30 keV, \begin{table}
\begin{tabular}{l c c} \hline \hline
**Blasting Material** & **Size Range,** & **Working** \\  & **[mm]** & **Pressure, [Bar]** \\ \hline
1. White electrocorundum F90, mixed with sintered & & \\ hydroxyapatite with a particle size \(\leq\) 63 μm, in a ratio & 0.15–0.20 & 6 \\ of 3:1 & & \\  2. White electrocorundum F90, mixed with sintered & & \\   hydroxyapatite with a particle size \(\leq\) 63 μm, in a ratio & 0.15–0.20 & 3 \\ of 3:1 & & \\  3. Fine white electrocorundum mixed with sintered & & \\  hydroxyapatite with a particle size \(\leq\) 63 μm, in a ratio & 0.10–0.15 & 6 \\ of 3:1 & & \\  4. Fine white electrocorundum mixed with sintered & & \\  hydroxyapatite with a particle size \(\leq\) 63 μm, in a ratio & 0.10–0.15 & 3 \\ of 3:1 & & \\  5. White electrocorundum F90 & 0.15–0.20 & 6 \\  6. White electrocorundum F90 & 0.15–0.20 & 3 \\  7. Fine white electrocorundum & 0.10–0.15 & 6 \\  8. Fine white electrocorundum & 0.10–0.15 & 3 \\  9. Glass balls & 0.04–0.07 & 6 \\  10. Glass balls & 0.04–0.07 & 3 \\  11. Olivine & 0.1–0.5 & 6 \\  12. Olivine & 0.1–0.5 & 3 \\  13. Red garnet & 0.40–0.80 & 6 \\  14. Red garnet & 0.40–0.80 & 3 \\  15. Brown electrocorundum & 0.120–0.212 & 6 \\  16. Brown electrocorundum & 0.120–0.212 & 3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Blasting material group setting. beam current--1 pA to 2 \(\mu\)A, resolution--3 nm at 30 keV, magnification 1\(\times\)-1,000,000\(\times\), Figure 2.  
The samples were carefully fixed on the inner microscope Winchester bench without touching their surface. The samples were examined, and the images were acquired using energy settings between 15 and 30 keV. Before the in vitro experiments, to prevent bacterial and fungal contamination, all sandblasted Ti (TiCP4) and Ti6 Al4V alloy disks were individually sterilized in Petri dishes by autoclave for 30 min at 120 \({}^{\circ}\)C.  
Gingival epithelial cells (Innoprot, Derio, Spain, REF: P10864) were cultured in the specific medium for epithelial cells supplemented with 2% fetal bovine serum (FBS), 1% penicillin-streptomycin (PE/ST), and growth factors for epithelial cells (EpiCGS) in sterile culture dishes, on which poly-L-lysine (2 \(\mu\)g/cm\({}^{2}\)) was previously deposited by incubation  
Figure 1: Hommel-Etamic Nanoscan 855 was used to determine the surface roughness of the sandblasted samples. Figure 2: TSCAN VEGA SEM microscope used for SEM analysis. at 37 \({}^{\circ}\)C for at least 1 h. The cells were kept in culture in the incubator at 37 \({}^{\circ}\)C in a humid atmosphere with 5% CO\({}_{2}\). Propagation in cell culture when 90% confluence was reached was achieved using trypsin/EDTA solution.