## 3 Results and Discussion
### Hardness
It is also important to note that the implant studied by the authors was a scaffold with a porous structure, which is why its surface was not subjected to the final polishing process, as was the case with the samples analyzed in this article. To determine the differences in physicochemical and mechanical properties, surface roughness and wettability, corrosion resistance with macroscopic evaluation and hardness measurements were carried out. The highest values of the roughness parameters Sa and Ra were recorded for the initial condition (bar after plastic working). The remaining results were quite similar, as surface treatment reduced the roughness of the specimens from both groups, regardless of the manufacturing process used for the materials (Figure 7). Steam sterilization reduced the roughness of the samples, except for the printed samples and bar after plastic working, which were sandblasted and then heat-treated and steam-sterilized [43]. The contact angle with distilled printed and Ti6 Al4V bar samples after plastic working was analyzed using the sitting drop method (Figure 9). The steam sterilization process influenced reducing the contact angle in all cases, indicating that the surface becomes more hydrophilic, although the Ra parameter for roughness increases. The lowest  
Figure 13: Results of Vickers hardness measurements: bar after plastic working samples (green), DMSL samples (blue). wettability angle, and therefore the highest surface energy, was recorded for DMLS samples 1, 2, 4. This is due to the surface modifications that occur during steam sterilization. Steam sterilization can lead to the formation of a more homogeneous and hydrophilic oxide layer on the surface of the material. This layer increases the surface energy by improving the material's ability to interact with water molecules, resulting in a lower contact angle [44]. Surface treatments such as grinding and mechanical polishing also significantly affect the change in contact angle; the greatest change was observed in samples printed after mechanical polishing, which had the lowest value of the Ra parameter (baseline samples). The pitting corrosion resistance test showed that both specimens made from bar after plastic working samples and DMLS-printed specimens exhibit pitting corrosion resistance over the entire measurement range. The results obtained for the printed specimens in the initial state are in accordance with the data presented by the authors [42; 45]. The corrosion potential, determined during the authors' own pitting corrosion resistance tests, was \(\mathrm{E_{cor}}=-0.130\) V, while in this publication, the value was \(\mathrm{E_{cor}}=-0.131\) V. Surface treatments such as sandblasting lead to the formation of an unstable and very thin surface layer, which can contribute to the initiation of pitting in the structure of the test material. Therefore, it can be concluded that mechanical polishing, both in the case of bar and printed samples, significantly increased the resistance to pitting corrosion. To confirm the results of the pitting corrosion resistance tests, a surface analysis of the specimens was carried out before and after the corrosion tests. The results of this analysis are shown in Figure 11. Surface analysis confirmed the absence of corrosion changes and pitting for samples from both groups. From the results obtained, it was observed that the printed samples in their initial state showed a higher hardness than the bar samples after plastic working. This is related to the different mechanical properties and chemical composition of the material, which are described in detail in [28; 33]. Heat treatment and steam sterilization contributed to an increase in hardness in both cases (\(p<0.05\)) compared to samples in the initial state. In [46], the authors performed heat treatments at 700 \({}^{\circ}\)C, 950 \({}^{\circ}\)C, and 1000 \({}^{\circ}\)C. Samples treated at 700 \({}^{\circ}\)C exhibited hardness values like those of the initial material.