## 4 Discussion  
Several evidence-based studies and systematic reviews in the last years investigated the efficacy of autologous platelet concentrates used for enhancing alveolar socket healing and reducing postoperative discomfort [6; 8; 27]. Such reviews demonstrated that different types of platelet concentrates, when compared to spontaneous healing, may produce several beneficial effects. Acceleration and improvement of soft tissue healing (better epithelization, more vascularization, and faster socket closure with respect to control) is the most frequently observed effect. Additionally, better hard tissue healing, evaluated through different techniques (histology and histomorphometry, intraoral radiographs, cone-beam computed tomography, micro-TC, scintigraphy, clinical measurement of ridge width and height changes) was often reported [6; 8; 27]. In addition, reduced postoperative pain and symptoms, lower incidence of alveolitis and other adverse events respect to control was a common finding in studies that investigated such effects. Nevertheless, almost all clinical studies evaluated a single type of platelet concentrate, used alone or in combination with osteoconductive scaffolds. Therefore, even if most studies emphasize the beneficial effects of the product under investigation, in the absence of direct comparisons it is difficult to know if some platelet concentrate works better than others do, or if all of them produce similar clinical benefits. As highlighted by systematic reviews, there is a lack of clinical studies comparing two or more types of platelet concentrates. In the present study, the effect of two autologous platelet concentrates, on the early healing of post-extraction sites, were compared, with the hypothesis that both products were equally effective. The choice of a split-mouth study allowed eliminating the inter-group variability due to differences in the response to treatment, and in blood characteristics, of different patients. On the other hand, a limitation of the present study is the absence of a control group with sockets left to heal spontaneously. Indeed, there were two reasons for that. Firstly, as said, most of the previous studies used spontaneous healing as the control group, so it seemed useless to repeat once again the same observations made by others. Secondly, the choice of a split-mouth design makes it difficult to add a third group, as the chance of finding a sufficient number of patients in need of at least three comparable tooth extractions, in a reasonable amount of time, is rather low. Our results confirmed the hypothesis of similarity, though a faster closure at 7 days in the vestibulo-palatal/lingual dimension, and a lower reported pain 1 day postsurgery was recorded in the sites treated with CGF. The results of the present study, in terms of both healing index and pain control in the first week postoperative, are in line with previous reports on L-PRF for postextraction socket healing. [PERSON] et al. in 2015, in a study on L-PRF obtained with Intra-Lock device, used the same modified healing index as in this study, reporting a 7-day healing index of 4.8 \(\pm\) 0.6, close to excellent healing score and very similar to our findings [28]. Other studies used the original Landry healing index and found scores in the range of excellent [29; 30; 31]. Regarding pain reduction, other studies using L-PRF reported VAS score and pattern very analogue to that observed in the present study [28; 29; 30; 32; 33]. Fewer studies evaluated the effect of CGF on socket healing, due to its more recent introduction in the field of platelet concentrates. [PERSON] et al. in 2019 reported significant benefits of CGF as compared to spontaneous healing in soft tissue healing, postoperative pain, swelling, and trismus after third molar surgery [34]. [PERSON] et al. in 2020 reported that CGF is effective in relieving pain and expedite wound healing as compared to conventional treatment alone, represented by socket curettage and saline irrigation, in alveolar osteitis [35].