# Micro-Raman Spectroscopy of Dental Implants Subjected to Different Surface Treatments
## 3 Results  
We analyzed a series of implants, from untreated Ti-alloy to the finished implant. For each step, the effect of plasma treatment was verified. In Figure 1b the Raman representative spectra from sample N1-N5 are reported in the energy range between 100-800 cm\({}^{-1}\), i.e., the region where the Raman modes of titania should be active. N1 samples present a machined surface. No Raman signals are evident in their spectra. Only weak and narrow lines are visible at low energy due to the laser plasma straight lines clearly visible for  
Figure 2: (**a**) Raman spectrum at room temperature for N5 sample (open circle) and the result from the best-fitting procedure (solid line). The single components used to obtain the best-fitting curve are also reported [see text]. (**b**) The values of the linewidth for the Eg mode at around 150 cm-1, derived from the results of the best-fitting analyses from ten Raman spectra (point 2–point 11). The first and the latter are the typical values obtained from a single crystal anatase crystal and nanosized (10 nm) powders. the high reflectivity of the starting material. A clear sign of TiO\({}_{2}\) is not evident. Nevertheless, since the TiO\({}_{2}\) layer in machined implants is below 10 nm, a non-typical spectrum is usually obtained, possibly resembling structures arising from a thin discontinuous TiO\({}_{2}\) layer formed at the metal/oxide interface [36,49]. In such cases, Raman analysis may fail to identify the type of the oxides due to bulk interference [36,50]. Although a previous study [36] observed traces indicating the presences of anatase and amorphous TiO\({}_{2}\), the intensity of the Raman signal is too low in both our observation and, in our opinion, in theirs, to attribute to the spectra a unique interpretation. N2 samples present a machined and Al\({}_{2}\)O\({}_{3}\)-blasted surface. The related spectrum displays unresolved frequency Raman activities in the spectral region from 100 to 400 cm\({}^{-1}\) together with a weak but well-structured Raman signal at about 416 cm\({}^{-1}\). The unresolved frequency Raman activity observed in the N2 sample spectrum could be ascribed to an oxide amorphous phase, and it is impossible to rule out the presence of Ti-O bonds in this phase. The Raman signal at about 416 cm\({}^{-1}\) is consistent with the presence of corundum residuals [see database [[http://rruff.info/Corundum](http://rruff.info/Corundum)]([http://rruff.info/Corundum](http://rruff.info/Corundum))]. All the Al\({}_{2}\)O\({}_{3}\)-blasted samples presented RS features of corundum. N3 is a machined and acid-etched surface. The Raman spectrum is very similar to the N1 ones and the same considerations allowed to exclude any formation of TiO\({}_{2}\) layer, even highly disordered. The etching treatment tested in the present study does not appear to affect the solid state of implant surfaces. The N4 surface was blasted with Al\({}_{2}\)O\({}_{3}\) and subsequently etched with HNO\({}_{3}\)/HF. The Raman spectrum displays a sizable band centered close to 140 cm\({}^{-1}\) accompanied by broadened Raman activity extending to 400 cm\({}^{-1}\). These features can be considered a direct indication of the formation of TiO\({}_{2}\) amorphous phase [36], characterized by a much less intense Raman signal than the one of anatase or rutile phases, but with the clear presence of the Raman signal reminiscent of the E\({}_{\text{g}}\) mode of anatase structure. Therefore, it seems appropriate to state that the synergistic effect of sandblasting with Al\({}_{2}\)O\({}_{3}\) and etching with HNO\({}_{3}\)/HF further increases the thickness of the amorphous TiO\({}_{2}\) layer. The N5 surfaces were subjected to the blasting and acid etching treatment and were also subjected to anodization with direct current at 60 V for 10 s. The Raman spectrum in the first region between 100 and 300 cm\({}^{-1}\) is quite similar to the N4 spectra but with a net increase in the total scattered yield.