The aim of the present study was to investigate an inorganic bovine-derived hydroxyapatite bone substitute (Osteograph ® ) mixed with the same biomaterial coated with a synthetic peptide (P-15) analogue of collagen ). This blend of bone replacement materials was used for sinus floor augmentation. Assessments were carried out by using histology methods, transmission electron microscopy (TEM) and microanalysis (EDX). Ultrastructural and analytical features of the interfaces between the graft material and the peri-biomaterial tissues were evaluated six months after implantation. Our findings clearly show that newly-formed crystallites first develop at the surface of implanted crystals. Histological investigations revealed new bone tissue linking biomaterial particles together. TEM assessments pointed out that lamellar bone was generally separated from the graft material by a layer of woven bone measuring between 1 and 1.5 µm in thickness. Although calcified bone tissue was observed in direct contact with bone filling particles, the presence of mineralized granular material around implanted particles was also noticed. No characteristic periodic striation of mineralized collagen was evident within that mineralized structure. Chemical analyses (TEM-EDX) realized at different locations of newly formed mineralized granular substance along the interface revealed average Ca/P ratios ranging between 1.02 and 1.63. The different, concomitantly occurring, aforementioned structural features of the interfaces strongly suggested that the host responses to the used biomaterial blend resulted from dynamic osseointegration phenomena related to various interfacial mechanisms. Nevertheless, the biological response to the bone graft material appeared clinically and histologically satisfactory.