## 2 Materials and Methods  
The Ti disks used in this study were made of pure Titanium medical grade 4 (TICp4), Signer Titanium AG, Freienbach, Swiss, having a diameter of 6 mm, 1 mm thickness, while Ti alloy disks were made of Ti6 Al4V, Dynamet USA, Signer Titanium AG Swiss (Ti max 90%, Al max 6%, V max 4%, Fe max 0.25%, O max 0.2%) with a diameter of 8 mm, 1 mm thickness. The disks were cut using a L20 8M CNC lathe, Citizen Cincom, Esslingen Germany, with 6 linear axes and two rotary axes. The slight difference in the diameter size is due to the fact that the original rods used to cut the disks were available for purchase only in the above-specified diameter dimensions. A comparison of the physical and mechanical properties of Ti and Ti6 Al4V is presented in Table 1.  
All disks intended for sandblasting with the same spraying material were placed on a support specifically constructed for this purpose as a series of triplicates for Ti and triplicates for Ti alloy with double-adhesive tape. The sandblasting equipment was loaded with the required spraying material, and by moving the sliding device through the sandblasting window, all sets of discs (3 Ti CP4 and 3 Ti6 Al4V) were sandblasted at the same time, at the same pressures, and for the same durations established in the protocol. Then, the disks and the spraying material were changed, and the procedure was repeated for all the spraying materials, pressures, and blasting durations. The sandblasting was carried out manually using a Geko SBC 110 booth produced by Gebo Tools SRL, Cluj-Napoca, Romania, provided with multiple nozzle blasting guns (4, 5, 6, 7 mm), using two different working pressures: 3 and 6 bar. For an easy understanding and codification of samples and working conditions, where it is not specified, normal working pressure means a working pressure of 6 bar, while half working pressure means a working pressure of 3 bar. The particles used for sandblasting are presented in Table 2.  
The digital microscope used to acquire the micrographs was an Optika SFX-91D, Opptika, Ponteranica, Italy. After preliminary degreasing of the samples in isopropyl alcohol for 5 min at 25 \({}^{\circ}\)C in an ultrasonic bath (40 kHz), the sandblasting was carried out manually, at a 90\({}^{\circ}\) angle, \begin{table}
\begin{tabular}{c c c} \hline \hline
**Property** & **Ti** & **Ti6 Al4V** \\ \hline Density, g/cm\({}^{3}\) & 4.51 & 4.43 \\ Melting point, \({}^{\circ}\)C & 1660 & 1660 \\ Tensile strength, MPa & 680 & 950 \\ Yield strength, MPa & 560 & 850 \\ Poisson’s ratio & 0.34–0.40 & 0.34–0.38 \\ Elastic modulus, GPa & 105–120 & 110–114 \\ Elongation at break, \% & 23 & 14 \\ Hardness (Vickers) & 250 & 349 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Physical and mechanical properties of Ti, Medical Grade 4 and Ti6 Al4V. at 30 mm distance from the abutments, using a 7 mm nozzle, at 3 and 6 bar pressure, the blasting times being 10, 20, and 60 s. Similar cleaning and blasting operating parameters are reported in the literature [7; 8; 15; 16]. In order to establish the influence of the sandblasting materials used as well as the influence of the working parameters, measuring the roughness is required [1; 2; 16]. The purpose of evaluating the roughness parameters on the surfaces of the samples is to observe possible changes in the surface of the material depending on the process to which they were subjected. In general, roughness is defined by the set of irregularities that form the relief of the real surface, whose steps are relatively small in relation to their depth.