## 3 Results  
The microscopical aspect of the novel disc presented with a very high porosity and a uniform 3D framework at the SEM observation (Figure 1A,B). At 480\(\times\) of magnification, the surface appeared as a net of melted metal uniformly interconnected by craters, filled by sintered metallic particles (Figure 1C). The porous aspect of the material was even more evident from the 3D reconstruction (Figure 1D). Analyzing and comparing the three surfaces at higher magnification (1200\(\times\)) and in the 3D reconstruction, the greater difference in superficial topographies between the three groups was evident: the machined one (Figure 2A,D) had a regular superficial structural appearance, with characteristic circumferential and parallel lines; DAE (Figure 2B,E) had a very irregular surface, characterized by a high porosity with holes of different shapes and sizes. The 3D discs (Figure 2C,F) appeared in about the 50% of the image, as a uniform rough surface, that in the other 50% was characterized by the presence of a high crater, containing semi-molded metallic powders. The average values \(\pm\) standard deviation of the microroughness parameters calculated are shown on Table 1. The DAE samples were characterized by the higher micro-roughness, with statistically significant differences with respect to the machined one but not with respect to the 3D one (Table 1). The surfaces showed statistically significant differences between all groups, with DAE characterized by the highest values, followed by the machined and 3D ones. The EDX analysis (Figure 3), performed at 5 kV, showed that the upper layer of the 3D samples was characterized by the presence of Al and Al\({}_{2}\)O\({}_{3}\). Consequently, a significantly lower concentration of TiO\({}_{2}\) was found with respect to the machined and DAE samples (\(p\) < 0.001). The weight Ti concentration (%) was significantly lower on the 3D samples with respect to the machined (\(p\) = 0.007) and DAE (\(p\) = 0.014) discs. Figure 1: Photograph of the novel 3D surface, upper (**A**) and lateral (**B**) views. (**C**) SEM image at 480\(\times\) magnification of the novel 3D surface and (**D**) the respective 3D reconstruction. The observation at AFM demonstrated that the 3D showed a significant higher nano-roughness with respect to the other groups for all height parameters analyzed (Figure 4). The DAE and machined discs showed no significant differences, with the exception of the Sdq and Sdr values (\(p\) = 0.020). The analysis of the wetting properties of the samples showed that the DAE samples' WCA was significantly lower with respect to the other two groups, \(p\) < 0.001 (Figure 5). On the contrary, the WCA of the machined (87.713\({}^{\circ}\)\(\pm\) 1.732) and 3D discs (86.094\({}^{\circ}\)\(\pm\) 1.535) showed no significant differences. The microbiological analysis showed that _S. oralis_ colonization was significantly lower on 3D discs, concerning the colony forming units from the biofilm biomass measurement (Figure 6). Regarding the CFUs, no significant differences were described for DAE and 3D discs, but for the biofilm biomass, it was significantly higher on double etched surfaces. The machined surface showed the higher levels of _S. oralis_ CFUs. The Pearson correlation between the parameters studied showed that CFUs were inversely correlated with the nano-roughness of the samples and with the chemical composition of the upper layers of the discs, in particular with the Oxygen and Aluminum percentages (Table 1). A direct correlation was found between the bacterial count and the Ti percentage. The biofilm biomass was directly correlated with the percentage of Ti and aluminum in the upper layer of the samples and with the Surface Area (MSa) and inversely correlated with the nano-roughness. The live/dead analysis (Figure 7) confirmed the _S. oralis_ bacterial reduction on DAE and 3D surfaces with respect to machined and positive controls C+, which showed a higher percentage of live cells with respect to the other groups.