Should bone grafts in the upper jaw be allowed to heal for 3 or 6 months before inserting dental implants?

INTERVENTION: The surgical procedure and the applied grafts for sinus augmentation from lateral approach are the same for both study arms. Grafting materials are advanced platelet rich fibrin (A‐PRF) in combination with serum albumin‐coated allograft (BoneAlbumin) in both treatment groups. The test and control group differ only in the graft healing period (3 vs 6 months) . The surgical sites will randomly divide the participants into two groups by tossing a coin after the first surgical intervention is completed (sinus augmentation). Dental implants are placed 3 months (test) or 6 months (control) after bone augmentation. At the time of implant placement, bone core biopsy samples are collected directly from the implant sites with the use of a trephin bur for histological, histomorphometrical and micro‐computerized tomography analysis. Histomorphometric and micro‐computerized tomography analysis are performed by two investigators blinded to the treatment group. ISQ values are recorded by an Osstell device at the time of implant placement and at appointments 6, 8, 10, 12 weeks postoperatively. Prosthetic rehabilitation begins 3 months after implant placement. For follow‐up, 6‐month periods after final prosthesis delivery will be applied. CONDITION: Bone allografting to support dental implants ; Oral Health PRIMARY OUTCOME: ; Percentage of newly formed bone calculated from bone biopsy samples collected from the site of dental implant placement by micro‐CT and histomorphometry at 3 months (test group) and 6 months (control group) after surgery; ; SECONDARY OUTCOME: ; 1. Percentage of residual graft calculated from bone biopsies collected from the site of dental implant placement by micro‐CT and histomorphometry at 3 months (test group) and 6 months (control group) after surgery; 2. Percentage of connective tissue calculated from bone biopsies collected from the site of dental implant placement by micro‐CT and histomorphometry at 3 months (test group) and 6 months (control group) after surgery; 3. Implant stability quotient (ISQ) measured with Osstell ISQ device at implant placement and 6, 8, 10, 12 weeks after surgical intervention; ; ; INCLUSION CRITERIA: 1. Systemically healthy patients aged over 18 years 2. Requiring implant prostheses and oral rehabilitation 3. Insufficient residual height in posterior maxilla requiring a sinus augmentation from lateral approach to insert the implants (residual crest height =5 mm)