## 4 Discussion  
The purpose of the present study was to assess the effects of L-PRF on the healing process of the lower third molars extraction socket and its relationship with the local concentration of growth factors and cytokines. For this, a randomization unit was employed consisting of the participant's extraction socket and not that of a different participant. Such a study design, besides reducing inter-individual and demographic variables such as age and gender, usually provides relevant data without the necessary use of larger samples [13; 14]. Another important fact about the present study design was the double blinding at the levels of both participants and data evaluation (clinical and laboratory parameters). These are essential steps to reduce the risk of bias and improve the quality of data from clinical trials. Blinding was a topic of particular concern in the study design in order to ensure that both participants and researchers who assessed the outcomes remained unaware of the treatment on each surgical site. Special care was taken in the dental socket's primary closure, and the local anesthesia by regional block was performed so the participants would not feel the introduction of the L-PRF membranes. Furthermore, the membranes' compressing and natural shrinkage contributed to reducing differences between sites, as shown in Figure 4. With such a model, the present findings indicate that the use of L-PRF impacts the local surface concentration of growth factors, with repercussions on clinical parameters of recovery, such as the perception of pain and the quality of soft tissue repair. Regarding the local concentration of cytokines and growth factors, the present study employed a method of extraction based on previous reports for epithelial surfaces [23; 24]. The current findings show that the use of surface swabs may provide an alternative approach to compare the local release of growth factors by L-PRF. However, the data should also be considered with care, as the method may also be subjected to diverse sources of bias, since some methodological steps may interfere with the final amount of collected analytes, including the time of pressing, area of collection, and previous removal of saliva, which represents another well-known source of cytokines [25]. Besides, the examiner's experience was essential to avoid contamination, e.g., saliva and food debris in the suture region. Therefore, careful steps were taken in this study during sample collection, and the examiner guided the oral hygiene of all study participants to reduce the risk of bias during the evaluations performed. The description of this care may help to increase reproducibility and minimize the risk of bias on this kind of clinical/molecular assessment. The results show that the method of collection was adequate to detect significant differences between grafted and control sites for at least nine molecules, including all four growth factors investigated. FGF-2 or basic FGF (FGFb) is a potent mitogen, promoting angiogenesis and inducing connective tissue remodeling by the production of the extracellular matrix (ECM) by fibroblasts [26]. VEGF, besides its well-known angiogenic properties, also induces collagen deposition and epithelization through mitogenic and chemotactic actions [27]. PDGF is another GF that promotes mitogenesis, angiogenesis, cellular differentiation, and even the upregulation of other growth factors that promote fibroblatic function [28]. TGF-\(\beta 1\) is a multifunctional mediator that acts mainly by chemotaxis and mitogenesis of fibroblasts and macrophages, as well as stimulation of collagen deposition for connective tissue wound healing [29]. Through these mechanisms, these growth factors are expected to be directly associated with the regenerative properties of L-PRF [12; 30].