This study was conducted in two phases. In Phase 1, lateral window sinus floor augmentation was performed using a mixture of hydroxyapatite (30%) and β-tricalcium phosphate (70%) combined with autologous platelet-rich fibrin (PRF). Standard surgical protocols were followed, including prophylactic antibiotics, local anesthesia, and careful elevation of the Schneiderian membrane prior to graft placement.

In Phase 2, after six months of healing, core bone biopsies were harvested with a trephine drill at the planned implant site for histological analysis. Specimens were processed using standardized laboratory protocols and evaluated with light microscopy and digital imaging. Quantitative histomorphometric analysis was performed using ImageJ software to determine the area fractions of newly formed bone and residual graft material. Following biopsy retrieval, dental implants were placed and primary stability was measured with the Implant Stability Quotient (ISQ).

Phase 1: Lateral window sinus floor augmentation, bone graft The patient was prescribed a prophylactic antibiotic regimen consisting of Amoxicillin with Clavulanic Acid (1 g Augmentin tablet), taken one hour before the procedure. Local anesthesia was administered using 2% Lidocaine with Epinephrine (1:100,000). A crestal incision was made along the maxillary alveolar ridge, and a full-thickness mucoperiosteal flap was elevated to expose the surgical site. A lateral window was then prepared in the lateral maxillary wall using a piezotome. The Schneiderian membrane was carefully elevated using the sinus lift augmentation technique. For the grafting procedure, the material was prepared by mixing 30% HA with 70% β-TCP (Osteon II, Dentium, Korea), in a 1:1 ratio, combined with autologous Platelet-Rich Fibrin (PRF) obtained from the patient's blood.

Phase 2: The histological analysis of the bone grafts and implant placement After a healing period of six months, a second-stage surgery was carried out to remove bone tissue and place the implant. At the designated implant site, a trephine drill with a 3 mm outer diameter was used to obtain a core bone biopsy specimen for histological analysis. The biopsy samples were encoded, fixed in 10% formalin, and submitted to the Embryology Department at the University of Medicine and Pharmacy at Ho Chi Minh City, where a standardized protocol was followed for specimen preparation. Histological evaluation was performed using an Olympus BX51 optical microscope connected to an Olympus DP72 12.5 MP digital camera, with captured images transmitted to a computer for assessment of histological parameters. Following biopsy retrieval, the implant osteotomy was completed, and the implant was inserted. Primary stability was assessed using the Implant Stability Quotient (ISQ) index.

Histological sections were analyzed using ImageJ software to quantify the area fractions of newly formed bone and residual graft particles, following established protocols. For each biopsy, three stained sections were evaluated, and the mean value was calculated. The regions corresponding to newly formed bone and residual graft material were delineated using the polygon selection tool, and the software computed their surface areas. The area fraction percentage (AA%) was then expressed as a proportion of the total image surface.

Inclusion Criteria:

• Patients with a residual bone height ≤4 mm
• minimum prosthetic space of 5 mm

Exclusion Criteria:

• Patients with acute or chronic maxillary sinusitis, bleeding disorders, diabetes mellitus, bone metabolic diseases, periodontal disease, or malignancies were excluded.
• taking medications that could affect bone metabolism or hemostasis
• Smokers and pregnant women were also excluded from the study.