## 1 Introduction  
In dentistry, there has been increasing interest in products that promote wound healing. In this respect, in the last few years, the use of platelet preparations, alone or in combination with other biomaterials, has proven to be a valuable regenerative option [1; 2; 3]. In fact, platelets not only play a critical role in haemostasis, but are also essential in the healing process as they are a source of growth factors [4]. Furthermore, in the last decade, it was shown that the use of autologous non-transfusional blood components in oral surgery allows for better and accelerated epithelialization and more vascularized connective tissue at wound healing sites, in addition to pain reduction [5; 6; 7; 8; 9; 10]. Among platelet concentrates, the leukocyte and platelet-rich fibrin (L-PRF) has become popular among clinicians, due to the easiness of preparation, the excellent regenerative properties, and its advantageous cost-effectiveness ratio [11; 12]. The efficacy of PRF in several oral surgery procedures has been documented in a number of clinical studies and systematic reviews [13; 14; 15].  
Concentrated Growth Factor (CGF) is a more recently developed autologous platelet concentrate containing growth factors together with blood cells [16], which was reported to promote bone regeneration [17; 18; 19]. Like other platelet concentrates, CGF is isolated from whole blood samples through a simple and standardized protocol by means of a specific centrifuge, without the addition of exogenous substances. The main characteristic of CGF is its mechanical consistency: it is an organic matrix rich in fibrin and, therefore, is denser than other platelet concentrates like platelet-rich plasma (PRP) or plasma rich in growth factors (PRGF), and very similar to L-PRF [20; 21]. These characteristics make CGF suitable for different uses, alone or in combination with other materials, as filler or as a scaffold for synthetic and biological membranes [22]. Furthermore, modified protocols in obtaining the blood sample, and in the centrifuging procedure are used for CGF preparation, as compared with PRF. The centrifugation protocol for preparing CGF consists of variable revolutions per minute (rpm), from 2400 to 2700 rpm, to separate cells in the venous blood, resulting in fibrin rich blocks that are much larger, denser and richer in growth factors than common PRF [21]. Essentially, the CGF can be considered an upgraded version of PRF, with a strengthened fibrin matrix and boosted growth factors and cytokines [23].  
The rationale of using platelet concentrates stands on the assumption that the presence of growth factors can represent an additional stimulation for tissue healing in patients undergoing oral surgery procedures, in order to improve bone and soft tissue healing [24]. Platelet-rich preparations seem to offer many advantages: they allow for the simultaneous action of multiple growth factors, increase tissue vascularization, and may also work as antimicrobial substances, potentially controlling the incidence of postoperative infection [25]. Given the above premises, a comparative study was designed with the aim of evaluating the performance of CGF for the treatment of postextraction socket, as compared to a more consolidated method such as L-PRF.