## 4 Discussion  
The main aim of this work was to test the effects of the 1064-nm Q-switch Nd:YAG nanosecond pulse on titanium surfaces, compared to the 1064-nm Nd:YAG and 980-nm diode lasers routinely employed for peri-implant infection management. Given the great growth in the use of different laser wavelengths for the treatment of periodontal and peri-implant disease [21], it was important to carry out an investigation. The focus of our study was to highlight possible harmful behaviours dictated by the interaction of these devices with the materials used for the dental implant. From the data collected from our experiments, significant differences can be seen based on the type of laser interacting with the grade 4 titanium sample. Observation of the sample under the scanning electron microscope showed us a damaged surface when it interacted with 1064-nm Nd:YAG, where the conspicuous morphological changes comparable to craters [29] constituted sections that are colonisable by bacterial species that are capable of worsening the peri-implant health conditions of the host [21,30]. On the other hand, the images relating to the sample interacting with a 980 nm diode laser and 1064-nm Q-switch Nd:YAG nanosecond pulse laser showed no signs of damage to the morphology of the grade 4 titanium surface, but only a slight modification of the surface. This is due to the removal of the more external coating and as a consequence of the exposure to the micro-crystallites of titanium and of some micropores that induce a very slight increase in roughness, as confirmed by the AFM results. From the roughness parameter evaluation, the results showed a small increase in Sa values for 1064-nm Q-switch Nd:YAG nanosecond pulse and 980-nm diode-treated parts, with respect to control values, but this is quite negligible when compared to the 1064-nm Nd:YAG treated one. This can indicate that the average absolute deviations of the roughness irregularities are comparable for these considered surfaces, while the treatment with 1064-nm Nd:YAG generated greater defects on the titanium surface. These considerations can be confirmed by the values of the Sq parameter, which is even more sensitive to surface deviations, and can be considered a reliable complementary parameter. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & \multicolumn{4}{c}{**Roughness Parameters**} \\ \hline  & **Sa [\(\mu\)m]** & **Sq [\(\mu\)m]** & **Sz [\(\mu\)m]** & **_n_** \\ \hline Control Ti & 0.109 \(\pm\) 0.007 & 0.147 \(\pm\) 0.013 & 2.470 \(\pm\) 0.538 & 4 \\
980 nm diode & 0.140 \(\pm\) 0.036 & 0.174 \(\pm\) 0.041 & 1.824 \(\pm\) 0.300 & 5 \\
1064 nm Q-switch Nd-YAG nano & 0.150 \(\pm\) 0.002 & 0.157 \(\pm\) 0.006 & 4.842 \(\pm\) 0.605 & 6 \\
1064 nm Nd-YAG & 0.868 \(\pm\) 0.550 & 1.189 \(\pm\) 0.651 & 9.278 \(\pm\) 3.010 & 3 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Roughness parameters from the surface analysis of AFM topography images. Average and standard error values were calculated over n images. Figure 6: Roughness parameter values were calculated from the surface analysis of AFM topography images. \(\star\) and \(\star\)\(p\)\(\leq\) 0.01 indicate statistically significant differences. The height distribution histograms also showed a greater height difference for the 1064-nm Nd:YAG-treated surface when compared to the other regions, as specified in Figure 6. The height axis of the histograms highlighted the higher and more spread surface irregularities for the 1064-nm Nd:YAG-treated surface, with histograms showing the presence of different peaks within the considered region c1-c2. For a deeper evaluation, the Sz parameter was calculated since it is more sensitive to randomly distributed peaks or valleys. Both Nd:Yag-treated regions showed higher Sz values when compared to the region treated with the 980-nm diode and the control; nevertheless, if one compares 1064-nm Nd:YAG-treated areas with 1064-nm Q-switch Nd:YAG nanosecond pulse-treated ones, the former would always show significantly higher Sz values.