Within the limitations of this observational retrospective study, it could be concluded that the development of inflammatory changes mediated by the presence of remnant bacteria surrounding hard tissues adjacent to implants might induce late failures of implants, and potentially trigger pathological features of apical peri-implantitis.

Throughout life, bone tissue undergoes a continuous process of resorption and formation. Melatonin, with its antioxidant properties and its ability to detoxify free radicals, as suggested by Conconi et al. (2000) may interfere in the osteoclast function and thereby inhibit bone resorption, as suggested by Schroeder et al. (1981). Inhibition of bone resorption may be enhanced by a reaction of indoleamine in osteoclastogenesis. That it has been observed melatonin, at pharmacological doses, decrease bone mass resorption by suppressing through down regulation of the RANK-L, as suggested by Penarrocha Diago et al. (2005) and Steflik et al. (1994). These data point an osteogenic effect towards that may be of melatonin of clinical importance, as it could be used as a therapeutic agent in situations in which would be advantageous bone formation, such as in the treatment of fractures or osteoporosis or their use as, a bioactive surface on implant as suggested by Lissoni et al. (1991).

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Introduction: Autologous platelet concentrates, have recently emerged as a possible tool to improve regenerative procedures in the medical field. Objective: To analyze the literature on autologous platelet concentrates in regenerative endodontics, such as: Platelet Rich Plasma, Platelet Rich Fibrin, PRP/PRF Vs Blood Clot as a scaffold in regenerative endodontics. Methodology: Using the keywords Regenerative Endodontic Treatment, Autologous Platelet Concentrates, Immature Teeth, Platelet-rich Fibrin, Platelet-rich Plasma, Revitalization Endodontics, the MEDLINE/PubMed and ScienceDirect databases were searched, with emphasis on the last 5 years. It was evaluated with the PRISMA and AMSTAR-2 guidelines.Results: Platelet-rich plasma releases growth factors during the first hours after placement and induction of mesenchymal stem cells. Platelet Rich Fibrin is a second-generation platelet concentrate that releases growth factors more slowly, forming a network that traps leukocytes and platelets, liquid platelet rich fibrin has a higher concentration of leukocytes, which enhances immune defense in LPS-induced inflammation. Compared to blood clot, PRP and PRF show improved healing results, reducing infection and inflammation. Conclusion:The use of autologous platelet concentrates presents a more controlled scaffold in regenerative endodontics, with successful results, such as periapical healing, root thickening and apical closure.