The objective of study is to evaluate the influence of the use of Platelet Rich Fibrin (PRF) from the patient's produced by a new horizontal centrifugation protocol associated with particulate xenogenous bone graft in the rehabilitation of atrophic maxillary sinus for early osseointegrated implants plancement. In a split-mouth model, twelve patients in need of rehabilitation with at least two bilateral implants in the regions of atrophic maxillary sinus will simultaneously undergo bone reconstruction using deproteinized particulate xenogenous bone (Bio-Oss Small®; Geistlich AG, Wolhusen , Switzerland). Randomly, one of the surgical sites of each patient will be reconstructed using the associated technique of solid PRF + Liquid PRF with the xenogen material, where at the end of the grafting procedure, both sites will be protected by a collagen membrane (Bio-Gide® Compressed; Geistlich AG, Wolhusen, Switzerland) positioned over the surgical access of the maxillary sinus. During the research, cone-beam computed tomography scans will be performed preoperatively, immediately after surgical procedure, 3 months after maxillary sinus reconstruction, after immediate implants placement and 12 months after functional load of the implants for comparative volume measurement of tissue gain and the maintenance of the grafted tissue. During the implant surgery, bilateral biopsies will be collected after 4 months of the regenerative surgical procedure during the early dental implants surgery by virtually guided surgery. The stability of the implants will be measured by means of resonance frequency analysis (ISQ) after the immediate postoperative period and 6 postoperative months as the clinical success rates of the implants after 12 months with functional load. The tissue samples will be used for histological, histomorphometric, immunohistochemistry and microtomographic analysis. All data obtained will be statistically analyzed.

Inclusion Criteria:

• need of at least one dental implant in atrophic maxillary sinus region;
• insufficient amount of vertical bone remnant for the dental implants surgery (maximum of 4mm);
• sufficient horizontal bone thickness for dental implants rehabilitation;
• present edentulism in the area to be treated for at least 6 months;
• similar pattern of pneumatization of the maxillary sinuses.

Exclusion Criteria:

• any contraindication for the installation of dental implants;
• need of horizontal bone augmentation;
• pacientes with inflammatory or autoimmune disease in the oral cavity;
• use of immunosuppressants, corticosteroids or bisphosphonates for medical needs;
• pacientes with history of malignancy in the last 5 years;
• smoking patients or patients reporting excessive alcohol consumption;
• decompensated systemic condition, uncontrolled periodontal disease, insulin-dependent diabetic patients, patients with blood-related diseases and patients who need oral rehabilitation in the lower arch;
• It is also noteworthy that patients with a history of reconstructive bone therapies in the maxillary sinus region or with a history of oroantral communication will be excluded from this research.

The researchers responsible for the tomographic and histometric analysis will not be aware of the type of group in which the sample is located.