Radiographic, histological, and immunohistochemical comparison of allograft, xenograft, and combined graft in maxillary sinus augmentation: a prospective randomized clinical study

Abstract

This prospective randomized clinical trial aimed to compare the radiographic, histological, and immunohistochemical outcomes of allograft, xenograft, and combined graft use in maxillary sinus augmentation. Patients with a residual alveolar bone height ≤ 4 mm in the posterior maxilla were randomized into three sinus augmentation groups: allograft (G2), xenograft (G3), and 1:1 combined graft (G4). A control group (G1) underwent implant placement without sinus lifting. Cone-beam computed tomography (CBCT) images were obtained preoperatively, immediately postoperatively, and at 6 months. Residual bone height, initial graft height, and graft height reduction were measured. At 6 months, bone biopsies were harvested prior to implant placement and analyzed histologically and immunohistochemically for osteocalcin (OC), osteopontin (OP), and RUNX2 expression. Correlations between radiographic and immunohistochemical findings were evaluated. Significant vertical bone gain was achieved in all sinus augmentation groups. Although greater initial graft height was observed in the allograft and combined groups in the early postoperative period, no significant differences were detected among the groups at 6 months ( p > 0.05). Greater graft height reduction was observed in the allograft group, whereas the xenograft group demonstrated better preservation of graft height. Histological and immunohistochemical analyses revealed higher osteogenic activity in the allograft group. Moderate positive correlations were found between radiographic height gain and OC ( r = 0.62, p = 0.004) and RUNX2 ( r = 0.57, p = 0.011) expression. Allograft, xenograft, and combined grafting approaches provided comparable bone height at 6 months following maxillary sinus augmentation. However, graft height changes and biological activity differed according to graft type. Xenografts demonstrated greater graft height stability, whereas allografts exhibited higher osteogenic activity at six months. Graft selection should consider both radiographic graft height changes and biological healing characteristics. ClinicalTrials.gov Identifier: NCT07407361. Registration date: 2026-02-05. Retrospectively registered.