## 4 Discussion  
The recourse to non-surgical system for the treatment of periodontal/periimplant disease represents a trend topic in dental research nowadays [28]. The limitations of the conventional treatment scaling and root planing (SRP), required the necessity to test adjunctive protocols. Previous recent research was conducted to evaluate the efficacy  
Figure 2: Forest plot showing post therapy PPD (\(\geq\)5 mm) comparing the effect of adjunctive antimicrobial photodynamic therapy (aPDT) vs. scaling and root planing (SRP) divided into subgroups. of systems reporting an antimicrobial, antioxidant, and immunostimulant activity, such as ozone therapy [29; 30; 31], probiotics [32], paraprobiotics [33; 34; 35], posbiotics [36; 37], and photodynamic therapy [38]. The purpose of the current systematic review is to study the additional effects of aPDT application in nonsurgical periodontal therapy in patients with untreated periodontitis after a 3-month follow-up period. Additionally, based on the great heterogeneity observed among the studies selected, particularly in terms of laser type, tip diameter, wavelength, photosensizer, periodontal treatment modality, number of sites treated, population, and different possible combinations of these parameters, a careful attempt to conduct a meta-analysis was made only when the changes in PPD, BOP, and CAL between the baseline and 3-month follow-up were reported in the original articles using the same measurement indices and performing statistical searches by dividing them into subgroups according to the type of photosensizer. For the reduction in pocket depth (PPD), all 14 articles included in the review evaluated the probing depth at baseline and follow-up, and in five of these articles, we found a significant difference in PPD in the test group with respect to the control group [15; 21; 22; 23; 26]. All studies used indocyanine green as a photo activator; in the rest of the studies, an improvement was observed after treatment in both groups without a significant statistical difference, although we found a slightly greater improvement in favor of SRP+aPDT. Three studies [18; 20; 21] performed an additional follow-up at six months, and all agreed that a greater reduction in PPD, achieved by a combination of SRP/aPDT, was statistically significant after this period. The results of this systematic review agree with those found in studies by [PERSON] et al., 2018 [39], and [PERSON], 2018 [40], who stated that aPDT, in addition to SRP, provides a significant reduction in PPD at 3 and 6 months. The results of the present analysis partially agree with a previous review by [PERSON] [41], which found a significant reduction in PD at 3 months when PDT was also used, but no significant CAL gain after 3 months. According to the RCTs that performed microbiological evaluation, in two articles, we found an improvement in microbiological parameters in the test group compared to the control group [16; 25]. In three articles, there was an improvement in all microbiological parameters in both groups, but without a significant difference [19; 25; 26]. In the study by [PERSON] et al. [14], no differences were found between the two groups at baseline and follow-up. Thus, we conclude that, as reported by [PERSON] et al. [40], the bactericidal efficacy of aPDT in addition to SRP against periodontal pathogens in periodontal disease remains questionable. Reviewing the data obtained, the best results were obtained in the studies that used photosensitizing green indocyanine for BOP [23] for PPD [15; 21; 22; 23; 26], probably because of its efficacy in reducing bacterial load, as shown by [PERSON] et al., 2013 [42] and the study by [PERSON] et al., 2020 [43]. An analysis of studies suggests a short-term benefit of aPDT in addition to SRP, in terms of clinical parameters. However, evidence regarding its long-term efficacy is lacking and no significant effect was confirmed in regard to the CAL gain at 3 months.