Plane radiographs. H: A composite of the β-TCP microspheres and the hyaluronic acid powder gel was injected and a dental implant fixture was inserted (hydrogel group); B: A composite of the rhBMP-2 loaded porous β-TCP microspheres and the hyaluronic acid powder gel was injected and then a dental implant fixture was inserted (BMP-2 group). I: Only a dental implant fixture was inserted (implant group)