In therapeutic bone repairs, autologous bone grafts, conventional or vascularized allografts, and biocompatible artificial bone substitutes all have their shortcomings. Tissue engineering may be an alternative for cranial bone repair. Titanium (Ti) and its alloys are widely used in many clinical devices because of perfect biocompatibility, highly corrosion resistance and ideal physical properties. An important progress in treating bone defects has been the introduction of bone morphogenetic proteins (BMPs), specifically BMP-2. The proteins induce osteogenic cell differentiation in vitro, as well as bone defect healing in vivo. In this study, we fabricated the titanium plate with dioxide creating by microarc oxidation (MAO) and then electronic deposition of Ca.P that can carrier recombinant human bone morphogenetic protein-2 (rhBMP-2) to enhance osteogenesis in vitro and bone formation in vivo. The rhBMP-2 was controlled released from MAO-Ca.P-rhBMP2 implant was maintain within 35days longer than Ti without MAO modification group and without CaP electronic deposition group. In addition, the in vitro results revealed that the bioactivity of rhBMP-2 released from MAO-Ca.P-rhBMP2 implant with an ideal therapeutic dose was well maintained. In vivo, the critical-sized defect (20-mm diameter) of New Zealand White rabbits was used to experiment. We concluded that sustained controlled-release of rhBMP-2 above a therapeutic dose could induce osseointegration between the implant and surrounding bone the rate of bone formation into the implant and produce neovascularization. Our study combined the concept of osteoconductive and osteoinductive to do the bone tissue regeneration

The feasibility of bone transport with bone substitute and the factors which are essential for a successful bone transport are unknown. We studied six groups of 12 Japanese white rabbits. Groups A to D received cylindrical autologous bone segments and groups E and F hydroxyapatite prostheses. The periosteum was preserved in group A so that its segments had a blood supply, cells, proteins and scaffold. Group B had no blood supply. Group C had proteins and scaffold and group D had only scaffold. Group E received hydroxyapatite loaded with recombinant human bone morphogenetic protein-2 and group F had hydroxyapatite alone.

Distraction osteogenesis occurred in groups A to C and E which had osteo-conductive transport segments loaded with osteo-inductive proteins. We conclude that scaffold and proteins are essential for successful bone transport, and that bone substitute can be used to regenerate bone.

In a rabbit model we investigated the efficacy of a silk fibroin/hydroxyapatite (SF/HA) composite on the repair of a segmental bone defect. Four types of porous SF/HA composites (SF/HA-1, SF/HA-2, SF/HA-3, SF/HA-4) with different material ratios, pore sizes, porosity and additives were implanted subcutaneously into Sprague-Dawley rats to observe biodegradation. SF/HA-3, which had characteristics more suitable for a bone substitite based on strength and resorption was selected as a scaffold and co-cultured with rabbit bone-marrow stromal cells (BMSCs). A segmental bone defect was created in the rabbit radius. The animals were randomised into group 1 (SF/HA-3 combined with BMSCs implanted into the bone defect), group 2 (SF/HA implanted alone) and group 3 (nothing implanted). They were killed at four, eight and 12 weeks for visual, radiological and histological study.

The bone defects had complete union for group 1 and partial union in group 2, 12 weeks after operation. There was no formation of new bone in group 3. We conclude that SF/HA-3 combined with BMSCs supports bone healing and offers potential as a bone-graft substitute.