## 4 Discussion  
In the current study, wettability decreased after titanium tip ultrasonic instrumentation and increased after PRF pre-treatment to a level superior to the untreated samples. [PERSON] et al. (2012) used a cold atmospheric pressure gas-discharge plasma to reduce water contact angles on titanium disks with different surface topography: machined, SLA(r), SLAActive(r), diamond bur-treated or Airflow(r)-treated. They found out that the contact angles of titanium disks (baseline values: 68\({}^{\circ}\)-117\({}^{\circ}\)) were significantly reduced close to 0\({}^{\circ}\) irrespective of surface topography after the application of argon plasma with 1.0% oxygen admixture for 60 s or 120 s. The device used emits a cold flame. Temperature measurement yielded 42\({}^{\circ}\) at the tip of the plasma jet [30] potentially permitting its use in the clinical environment. [PERSON] et al. 2019 applied blood, fetal bovine serum and phosphate-buffered saline (PBS) on (brand-new) commercial implants. Wettability increased from no coating control group (74.7\({}^{\circ}\)\(\pm\) 3.683\({}^{\circ}\)) to its highest level after blood coating (10.4\({}^{\circ}\)\(\pm\) 0.747\({}^{\circ}\)) [31]. Phosphoric acid (38%) etching resulted in an increased wettability with respect to PRF pre-treatment. The authors found out that this trend is the same on smooth machined and irregular roughness sandblasted surfaces; this aspect can be useful if applied to the clinical environment. If a patient comes to the hospital with peri-implantitis, the clinician might not be able to know what kind of surface he is dealing with, considering that many implant systems are present on the market. The current study suggests that ultrasonic instrumentation and then PRF or phosphoric acid etching are a valid strategy to be applied in all cases. In a parallel study of the authors, we performed energy-dispersive X-ray spectroscopy (EDX). We found out that particulate left by utilizing grade IV titanium ultrasonic tip on grade IV titanium specimens left a particulate mainly composed of titanium [32]. This fact could be interesting, considering the biocompatibility of titanium. In the literature, there are some in vivo studies in which smooth machined brand new fixtures undergo sandblasting and acid etching. After that, implants are placed on the animal bone (rats or rabbits) to study the primary osseointegration [33; 34; 35]. In vitro studies on the same topic are present, too [36; 37; 38; 39]. The current study differs because we etched a surface previously instrumented to simulate an implant already affected with peri-implantitis. In the current study, we chose  
Figure 3: (**a**) Histogram comparing the three implant surfaces. No significant difference was found between machined, laser-treated, and sandblasted surfaces within brand new, platelet-rich fibrin (PRF), and etched groups. A statistically significant difference was found within the instrumented group between sandblasted and machined and between sandblasted and laser-treated surfaces. (**b**) Histogram comparing the four experiment steps. No significant difference was found within the laser-treated surface. Significant differences were found within machined surfaces (between brand new and etched, instrumented and etched, instrumented and PRF groups) and sandblasted surfaces (between brand new and instrumented, brand new and etched, instrumented and PRF, instrumented and etched groups). Statistically significant differences between samples are reported with an asterisk (\({}^{\star}\), \(p<0.05\)); NS: Not significant.”to use phosphoric acid (38%) because it is also a frequently used chemical in the dental office, particularly in restorative dentistry. Surface roughness difference between brand new and instrumented surfaces is a topic of a parallel study [32]. We observed a roughness decrease in laser-treated and sandblasted surfaces and a non-significant increase in machined surfaces. SEM laser-treated surfaces maintained their original micropatterned aspect.