Pilot Study of Bone Augmentation in Rat Calvaria Using Silicone Molds with Recombinant Human Bone Morphogenetic Protein-2-containing Atelocollagen Sponge

Bone augmentation is required for cases of highly absorbed alveolar ridge in the placement of dental implants. Various biomaterials and/or growth factors have been used to induce new bone formation; however, it remains difficult to obtain the required bone shape. In this study, we used cylindrical silicone molds coupled with recombinant human bone morphogenetic protein (rhBMP) to induce a specifically shaped bone. The cylindrical mold was made of silicone rubber impression material with a 10mm outer diameter, 5mm inner diameter, and 5mm height. RhBMP-2 was applied using an atelocollagen sponge placed into the silicone mold; it was then implanted into the parietal subperiosteal region of 8-week-old male Wistar rats. Histological and micro-computed tomography (micro-CT) analyses were performed to detect new bone formation at 2, 4, and 8 weeks after the surgery. Micro-CT analysis indicated a disc-shaped bone formation adjacent to the periosteum at 2 weeks after surgery. Newly formed bone was also detected near the parietal bone at 4 weeks. At 8 weeks, an almost cylindrical bone was formed in the silicone mold, and histological observation confirmed that the newly formed bone completely adhered to the host parietal bone. Hematopoietic bone marrow was also detected in the newly formed bone. A specifically made silicone mold might provide the scaffold required to induce a specific shape of newly formed bone under the combined induction of rhBMP