## 4 Discussion  
The aim of this review was to assess the efficacy of ultrasonic and/or hand instrumentation in nonsurgical periodontal therapy in terms of improving clinical conditions; in addition, another focus of this review was to understand whether adjunctive therapies such as laser, ozone and glycine/erythitol could provide better clinical outcomes. According to the studies included in the review [19; 20; 21; 22; 23; 24; 25; 26; 27], there was no statistically significant differences between the treatments proposed, demonstrating the achievement of clinical outcomes with the use of ultrasonic scalers and hand instruments. These results are consistent with previous research [64; 65; 66; 67]. A number of RCTs included in the review have shown that both treatment modalities are effective in terms of probing pocket depth, loss of clinical attack and bleeding on probing; these results are in agreement with the scientific literature, because other authors did not find any significant differences between the two modalities [65; 67]. It is well known that the goal of typical nonsurgical periodontal treatment is to remove biofilm to create the ideal environment for efficient bacterial plaque management [5; 68; 69]. Historically, scaling and root planing with manual instrumentation has been the most commonly used method of root surface debridement, with both clinical and microbiological benefits [70; 71; 72], as demonstrated by the studies included in this review [19; 20; 21; 22; 23; 24; 25; 26; 27]. Manual instrumentation also appears to be more effective in reducing the probing depth in moderate and severe periodontal pockets, according to [PERSON] et al., although no particular statistically significant differences were found with ultrasonic instrumentation [64]. However, even the most skilled operators do not always achieve the desired result of a biologically acceptable, clean and smooth root surface, largely due to the rather complicated anatomy and the skill of the operators [73; 74]. In addition, manual instrumentation can result in a loss of root substance due to excessive instrumentation [73; 75]. Following the cavitation effect, ultrasonic devices have been shown to be effective in reducing the probing pocket depth (PPD) and improving the overall effect of therapy [73; 76; 77]. This finding is consistent with an analysis of the literature by [PERSON] et al., who found that while the use of ultrasonic scalers improved the probing pocket depth, the use of manual instruments did not result in a statistically significant difference [67]. With the use of recently developed micro-ultrasonic tips, these can more effectively reach challenging areas, such as deep defects, root grooves and truncations, and progressively penetrate further into the pocket [78]. As can be seen from the results, numerous RCTs have shown that the results achieved with ultrasonic instruments are comparable to those achieved with manual instruments. In addition, the use of ultrasound devices appears to reduce pain and increase patient comfort: a study by [PERSON] et al. in 2021 suggests using a visual analogue scale (VAS) to assess the patient's experience after ultrasound therapy, with the experience of pain and discomfort related to the therapy rated in the lower range of the scale [79]. Patients are even more likely to accept this therapy if the water temperature of the instruments used can be adjusted [80]. They also cause less damage to the root surface because there is less tissue loss, although the statistics do not show a significant difference [81; 82]. There are conflicting opinions on the roughness of the surface: there are those who argue that you get a rougher surface with the hand tools (they would leave damage compatible with their blades) [83; 84] and who have shown the same effect with ultrasound (depending on the type of power chosen by the operator) [85; 86]. Despite these controversies, it can be concluded that the surface roughness produced is the same and biologically compatible [6; 87].