Allograft and alloplastic bone substitutes: a review of science and technology for the craniomaxillofacial surgeon

Rehabilitation of atrophic maxilla using the combination of autogenous and allogeneic bone grafts followed by protocol-type prosthesis

Currently, there are several techniques for the rehabilitation of atrophic maxillary ridges in literature. The grafting procedure using autogenous bone is considered ideal by many researchers, as it shows osteogenic capability and causes no antigenic reaction. However, this type of bone graft has some shortcomings, mainly the restricted availability of donor sites. In recent years, several alternatives have been investigated to supply the disadvantages of autogenous bone grafts. In such studies, allogeneic bone grafts, which are obtained from individuals with different genetic load, but from the same species, have been extensively used. They can be indicated in cases of arthroplasty, surgical knee reconstruction, large bone defects, and in oral and maxillofacial reconstruction. Besides showing great applicability and biocompatibility, this type of bone is available in unlimited quantities. On the other hand, allogeneic bone may have the disadvantage of transmitting infectious diseases. Atrophic maxillae can be treated with bone grafts followed by osseointegrated implants to obtain aesthetic and functional oral rehabilitation. This study aimed to show the viability of allogeneic bone grafting in an atrophic maxilla, followed by oral rehabilitation with dental implant and protocol-type prosthesis within a 3-year follow-up period by means of a clinical case report.

Fresh-Frozen Bone Allografts in Maxillary Ridge Augmentation: Histologic Analysis

Bone allograft has become an alternative to autogenous bone due to its decreased operative trauma and the almost unlimited supply of reconstructive material. The aim of the present study was to histologically evaluate the suitability of fresh-frozen bone graft (test group) used in maxillary ridge augmentation, comparing it to autogenous bone (native maxilla: control group). During the re-entry procedures, 9 months after the fresh-frozen allogeneic bone blocks were placed in the atrophic maxillary ridges, bone cores were removed with a trephine bur from test and control treatments in the same patient. Routine histologic processing using hematoxylin and eosin and Picrosirius staining was performed. Mature and immature collagen area and density analysis were carried out for both groups under polarization. The results of Student’s t test for paired samples (P > .05) showed no statistically significant difference in mature and immature collagen area or density percentage between test and control groups. Histologically similar bone formation patterns were observed in both groups. We concluded that fresh-frozen bone allograft is a biologically acceptable alternative for augmentation of the deficient alveolar ridge, showing a similar collagen pattern to that of autogenous bone.

Biomaterials for craniofacial reconstruction

Biomaterials for reconstruction of bony defects of the skull comprise of osteosynthetic materials applied after osteotomies or traumatic fractures and materials to fill bony defects which result from malformation, trauma or tumor resections. Other applications concern functional augmentations for dental implants or aesthetic augmentations in the facial region. For ostheosynthesis, mini- and microplates made from titanium alloys provide major advantages concerning biocompatibility, stability and individual fitting to the implant bed. The necessity of removing asymptomatic plates and screws after fracture healing is still a controversial issue. Risks and costs of secondary surgery for removal face a low rate of complications (due to corrosion products) when the material remains in situ. Resorbable osteosynthesis systems have similar mechanical stability and are especially useful in the growing skull. The huge variety of biomaterials for the reconstruction of bony defects makes it difficult to decide which material is adequate for which indication and for which site. The optimal biomaterial that meets every requirement (e.g. biocompatibility, stability, intraoperative fitting, product safety, low costs etc.) does not exist. The different material types are (autogenic) bone and many alloplastics such as metals (mainly titanium), ceramics, plastics and composites. Future developments aim to improve physical and biological properties, especially regarding surface interactions. To date, tissue engineered bone is far from routine clinical application.

Comparison of a synthetic bone substitute composed of carbonated apatite with an anorganic bovine xenograft in particulate forms in a canine maxillary augmentation model

OBJECTIVE

To evaluate the effect of a porous geometry in particulate bone on new bone formation by comparison of anorganic bovine carbonate apatite (ABCA) with synthetic carbonated apatite (SCA), which have similar properties but different micro-structures.

MATERIAL AND METHODS

Porous structures and anorganic components of ABCA and SCA were evaluated using scanning electron microscope and Fourier transform infrared. They were implanted in maxillary augmentation models with the mouth split design in a total of 15 Beagle dogs. The animals were sacrificed 4, 8 and 16 weeks after surgery, and the histomorphometrical results were statistically analyzed for the material's geometrical relationship and new bone formation in relation to the available space and contact surface for osteoconduction.

RESULTS

Both materials showed a typical infrared pattern of CO(3)(2-) -substituted hydroxyapatite (HA). Porous structures and a bridging effect of osteoconductive bone material were relatively better observed in SCA. The ratio of the material area to the total area was higher (P<0.01) for ABCA (28.03±6.09) than for SCA (20.26±4.23). The ratio of the number of particles possessing a pore structure to the total number and the interparticular space was greater (P<0.001 and 0.01) for SCA (18.12±9.44 and 79.74±4.23) compared with ABCA (1.45±1.74 and 71.63±5.85). The new bone areas and the bone-material contact lengths were greater in SCA than in ABCA (P<0.05).

CONCLUSIONS

The present study showed that porous structures may have an influence on new bone formation in osteoconductive bone substitutes.

Response of Bone and Periodontal Ligament Cells to Biodegradable Polymer Scaffolds In Vitro

In this in vitro study, the initial response of human periodontal ligament (PDL) cells and alveolar osteoblast-like cells (HOB) to three biodegradable polymers with varying pore size and different mechanical properties were evaluated. Scaffolds were synthesized from poly(L-lactide), [poly(LLA)], poly(L-lactide-co-1,5-dioxepan-2-one), [poly(LLA-co-DXO)], poly(L-lactide-co-ε-caprolactone), and [poly(LLA-co-CL)] with pore sizes greater or less than 90 µm by salt leaching. Cells were obtained from patients undergoing routine oral surgery. After 2—4 passages, the cells were grown on scaffolds and in culture plates (control) for 3 h (PDL cells), 3 days (PDL cells and HOB), 10 and 14 days (HOB), respectively. The cellular morphology and spreading were determined by scanning electron microscopy (SEM) and the attachment and proliferation were evaluated by MTT assays. The SEM images revealed heterogeneous cellular morphology and good spreading. Cellular attachment and proliferation were significantly higher on poly(LLA-co-DXO) and poly(LLA-co-CL) than on poly(LLA) scaffolds (p = 0.003) and highest for poly(LLA-co-DXO). Expression of bone formation markers, collagen-I (COL-I), transforming growth factor-β 1 (TGF-β1), and osteocalcin (OCN), was determined by ELISA. The expression of COL-1 was similar for HOB and PDL cells, but significantly higher for pore size >90 µm while the HOB expression of TGFβ 1 and OCN was greater on poly(LLA-co-CL) and poly(LLA-co-DXO) than on poly(LLA) scaffolds.

Proliferation and differentiation of mesenchymal stem cell on collagen sponge reinforced with polypropylene/polyethylene terephthalate blend fibers

Although tissue-engineered scaffolds made from collagen sponge are suitable for cell infiltrating, easily supplying oxygen and nutrients to cells, and removing the waste products, their mechanical properties are not satisfactory to be used as scaffold materials for tissue engineering applications. To improve mechanical properties of collagen, a novel porous scaffold for bone tissue engineering was prepared with collagen sponge reinforced by polypropylene/polyethylene terephthalate (PP/PET) fibers. Collagen solution (6.33 mg/mL) with PP/PET fibers (collagen/fiber ratio [w/w]: 1.27, 0.63, 0.42, 0.25) was freeze-dried, followed by cross-linking of combined dehydrothermal and glutaraldehyde. A scanning electron microscopy-based analysis of surface of the sponges demonstrated that the sponge with collagen/fiber <0.25 exhibited homogenous and interconnected pore structure with an average pore size of 200 μm. Incorporation of PP/PET fibers significantly enhanced the compressive strength of the collagen sponge. Proliferation and osteogenic differentiation of mesenchymal stem cell in collagen sponges reinforced with PP/PET fibers incorporation were significantly enhanced compared with collagen sponge without PP/PET incorporation. We conclude that incorporation of PP/PET fibers not only improves the mechanical properties of collagen sponge, but also enables mesenchymal stem cells to positively improve their proliferation and differentiation.

Effects of platelet-rich plasma and chitosan combination on bone regeneration in experimental rabbit cranial defects

This study aimed to investigate and compare the effect of chitosan sponge and platelet-rich plasma (PRP) gel alone as well as their combination on bone regeneration in rabbit cranial defects. Four cranial defects with a 4.5-mm diameter were created in rabbit cranium and grafted with PRP, chitosan sponge alone, and chitosan sponge incorporated with PRP. The rabbits were killed by the fourth and eighth weeks, and the defects were analyzed histologically. Higher bone formation was observed in the PRP group when compared with the other groups at weeks 4 and 8. All parts of the defects were filled with thick trabecular new bone in the PRP group. The amount of new bone formation in the control groups was found to be less when compared with the PRP group and the least in the chitosan group. The defects that were filled with chitosan sponge showed a limited amount of new bone formation and an obvious fibrous demarcation line between chitosan particles and bone. Application of PRP showed a histological tendency toward increased bone formation. Other forms or derivatives of chitosan may have beneficial effects to achieve new bone regeneration.

Bone morphogenetic proteins in critical-size bone defects: what are the options?

The recent development of new orthopaedic devices and advanced techniques for soft-tissue reconstruction have clearly improved the outcome in trauma and orthopaedic surgery. Nevertheless, large bone defects are still difficult to treat and require a careful analysis of the situation. Individual planning of the reconstructive strategy is desirable. Bone morphogenetic proteins (BMPs) have successfully been applied in the clinical setting for the treatment of spinal fusion, fracture healing and delayed and non-unions. Following the 'diamond concept', surgeons have begun using BMPs for treatment of critical-size defects also--in most cases, 'off label'; different treatment strategies are currently being evaluated. BMPs are often used in combination with autogenic, allogenic, xenogenic or synthetic grafting materials and even with mesenchymal stem cells. In addition, gene therapy approaches present an attractive option. Experimental studies and first clinical results are promising in the use of BMPs for treatment of critical-size defects; however, there is obvious need for further controlled studies to define strategies.

In vitro proliferation of human osteogenic cells in presence of different commercial bone substitute materials combined with enamel matrix derivatives

BACKGROUND

Cellular reactions to alloplastic bone substitute materials (BSM) are a subject of interest in basic research. In regenerative dentistry, these bone grafting materials are routinely combined with enamel matrix derivatives (EMD) in order to additionally enhance tissue regeneration.

MATERIALS AND METHODS

The aim of this study was to evaluate the proliferative activity of human osteogenic cells after incubation over a period of seven days with commercial BSM of various origin and chemical composition. Special focus was placed on the potential additional benefit of EMD on cellular proliferation.

RESULTS

Except for PerioGlas, osteogenic cell proliferation was significantly promoted by the investigated BSM. The application of EMD alone also resulted in significantly increased cellular proliferation. However, a combination of BSM and EMD resulted in only a moderate additional enhancement of osteogenic cell proliferation.

CONCLUSION

The application of most BSM, as well as the exclusive application of EMD demonstrated a positive impact on the proliferation of human osteogenic cells in vitro. In order to increase the benefit from substrate combination (BSM + EMD), further studies on the interactions between BSM and EMD are needed.

Maxillofacial reconstruction using custom-made artificial bones fabricated by inkjet printing technology

Ideally, artificial bones should be dimensionally compatible with deformities, and be biodegradable and osteoconductive; however, there are no artificial bones developed to date that satisfy these requirements. We fabricated novel custom-made artificial bones from alpha-tricalcium phosphate powder using an inkjet printer and implanted them in ten patients with maxillofacial deformities. The artificial bones had dimensional compatibility in all the patients. The operation time was reduced due to minimal need for size adjustment and fixing manipulation. The postsurgical computed tomography analysis detected partial union between the artificial bones and host bone tissues. There were no serious adverse reactions. These findings provide support for further clinical studies of the inkjet-printed custom-made artificial bones.

Leporine-derived adipose precursor cells exhibit in vitro osteogenic potential

Adipose-derived stem cells (ASCs) possess osteogenic potential and have been shown to undergo in vitro osteoblastic differentiation and promote bone regeneration in vivo. In this study, we describe the isolation and osteoblastic differentiation of rabbit ASCs and their behavior on a gelatin foam scaffold. These studies will form the basis of future in vivo studies of the osteogenic potential of rabbit ASCs for calvarial defect repair.Adipose-derived stem cells were isolated from New Zealand White rabbits and cultured in osteogenic medium +/- bone morphogenetic protein 2. Osteoblastic differentiation was assessed via histochemical stains for alkaline phosphatase (AP) and extracellular matrix (ECM) calcification. Reverse transcriptase polymerase chain reaction was performed to evaluate the expression of AP and the osteogenic transcription factor Runx2. Adipose-derived stem cells were seeded onto gelatin foam scaffolds at various densities, and cell proliferation was measured fluorometrically. Cells isolated from rabbit adipose tissue exhibited classic ASC morphology. Adipose-derived stem cells cultured in osteogenic medium exhibited more robust staining for AP and ECM calcification compared with ASCs in control medium. Furthermore, this staining was more marked in male ASCs versus female ASCs and also enhanced by bone morphogenetic protein 2. mRNA for AP and Runx2 were also increased in the osteoinduced cells. Theoptimal seeding density was 1 x 10 ASCs on an 8-mm gelatin foam scaffold. We have shown that rabbit ASCs have in vitro osteogenic potential and are compatible with a gelatin foam scaffold. Characteristic features of osteoblasts, such as ECM mineralization and expression of osteogenic genes, were demonstrated in this cell population. In vitro osteoblastic differentiation and scaffold studies are necessary before in vivo trials. The mechanism underlying the sex-based variation in osteoblastic differentiation is unknown but may involve signaling via factors such as estrogen.

Tissue engineering craniofacial defects with adult stem cells? Are we ready yet?

Over three-quarters of all craniofacial defects observed in the US per year are cleft palates. Usually involving significant bony defects in both the hard palate and alveolar process of the maxilla, repair of these defects is typically performed surgically using autologous bone grafts taken from appropriate sites (i.e., iliac crest). However, surgical intervention is not without its complications. As such, the reconstructive surgeon has turned to the scientist and engineer for help. In this review, the application of the field of tissue engineering to craniofacial defects (e.g., cleft palates) is discussed. Specifically the use of adult stem cells, such as mesenchymal stem cells from bone marrow and Adipose-derived Stem Cells (ASCs) in combination with currently available biomaterials is presented in the context of healing craniofacial defects like the cleft palate. Finally, future directions with regards to the use of ASCs in craniofacial repair are discussed, including possible scaffold-driven and gene-driven approaches.

Effect of BMP-2 and BMP-7 homodimers and a mixture of BMP-2/BMP-7 homodimers on osteoblast adhesion and growth following culture on a collagen scaffold

In the present study, we studied the involvement of BMP-2 and BMP-7 as homodimers and as a mixture of homodimers in bone regeneration using an engineered bone model. The engineered bone model consisted of a collagen scaffold populated with osteoblasts that acted as a carrier for the BMPs. BMP-2, BMP-7 and a mixture of BMP-2/BMP-7 were used at final concentrations of 10 and 100 ng ml(-1). Osteoblasts seeded onto a collagen scaffold were cultured for 24 h before being stimulated with the BMPs. Four days later, osteoblast adhesion to and growth on the scaffold were assessed. Osteocalcin, IL-6, metalloproteinase (MMP-2 and MMP-9) and protease inhibitor (TIMP-1 and TIMP-2) mRNA and protein levels were measured. Our results showed that the BMP-2, BMP-7 and a mixture of BMP-2/BMP-7 all promoted osteoblast growth on the collagen scaffold, with the mixture of BMP-2/BMP-7 enhancing the most growth. BMP-2 and the mixture of BMP-2/BMP-7 enhanced osteocalcin (an osteoblast differentiation marker) mRNA expression and protein secretion, likely via the IL-6 pathway given that IL-6 secretion was upregulated by BMP-7 and a mixture of BMP-2/BMP-7. BMPs promote extracellular matrix production by inhibiting MMP-2 mRNA and increasing TIMP-1 and TIMP-2 mRNA expressions and protein secretions. BMP-2, BMP-7 and the mixture of BMP-2/BMP-7 could promote bone regeneration via different mechanisms involving IL-6 and MMP inhibitors.

Reconstruction of critical size calvarial bone defects in rabbits with glass–fiber-reinforced composite with bioactive glass granule coating

The aim of this study was to evaluate glass-fiber-reinforced composite as a bone reconstruction material in the critical size defects in rabbit calvarial bones. The bone defect healing process and inflammatory reactions were evaluated histologically at 4 and 12 weeks postoperatively. Possible neuropathological effects on brain tissue were evaluated. The release of residual monomers from the fiber-reinforced composite (FRC) was analyzed by high performance liquid chromatograph (HPLC).

RESULTS

At 4 weeks postoperatively, fibrous connective tissue ingrowth to implant structures was seen. Healing had started as new bone formation from defect margins, as well as woven bone islets in the middle of the defect. Woven bone was also seen inside the implant. Inflammation reaction was slight. At 12 weeks, part of the new bone had matured to lamellar-type, and inflammation reaction was slight to moderate. Control defects had healed by fibrous connective tissue. Histological examinations of the brain revealed no obvious damage to brain morphology. In HPLC analysis, the release of residual 1,4-butanedioldimethacrylate and methylmethacrylate from polymerized FRC was low.

CONCLUSIONS

This FRC-implant was shown to promote the healing process of critical size calvarial bone defect in rabbits. After some modifications to the material properties, this type of implant has the potential to become an alternative for the reconstruction of bone defects in the head and neck area in the future.

Regenerative approaches in the craniofacial region: manipulating cellular progenitors for oro-facial repair

This review aims to highlight the potential for regeneration that resides within the bony tissues of the craniofacial region. We examine the five main cues which determine osteogenic differentiation: heritage of the cell, mechanical cues, the influence of the matrix, growth factor stimulation and cell-to-cell contact. We review how successful clinical procedures, such as guided tissue regeneration and distraction osteogenesis exploit this resident ability. We explore the developmental origins of the flat bones of the skull to see how such programmes of differentiation may inform new therapies or regenerative techniques. Finally we compare and contrast existing approaches of hard tissue reconstruction with future approaches inspired by the regenerative medicine philosophy, with particular emphasis on the potential for using chondrocyte-inspired factors and replaceable scaffolds.

Use of bone morphogenetic proteins for treatment of non-unions and future perspectives

Still a major problem in orthopedic and trauma surgery is the delayed healing or the non-union of long bone fractures. Demographic data reveal that due to the steadily rising age of the population, complications with the musculoskeletal system will increase during the next years. Bone morphogenetic proteins (BMPs) have successfully been applied in clinic for the treatment of delayed healing and non-unions. The broad difference concerning the indication, timing of treatment, dosage and application technique of BMPs calls for the need to perform further prospective studies in order to standardize the treatment and furthermore optimize the procedures or even develop new therapeutic strategies. For example, the application technique may be improved and in some cases injectable BMP preparations could be of use. Also the coating of implants with growth factors might be valuable in order to stimulate bone healing and to prevent delayed healing or non-union. This article tries to discuss some of the open questions, however can and will not reflect the absolute standard of care. To make the BMP treatment a standard of care, more clinical data and long time experiences are necessary. The intramedullary application of BMP in combination with autologous or allogenic bone grafts or bone substitutes after debridement and stabilization with implants seems to be an adequate procedure for treatment of atrophic non-unions. However, the total number of patients is too small to draw final conclusions. Further clinical studies need to be performed in the future.

Quantification of various growth factors in different demineralized bone matrix preparations

Besides autografts, allografts, and synthetic materials, demineralized bone matrix (DBM) is used for bone defect filling and treatment of non-unions. Different DBM formulations are introduced in clinic since years. However, little is known about the presents and quantities of growth factors in DBM. Aim of the present study was the quantification of eight growth factors important for bone healing in three different "off the shelf" DBM formulations, which are already in human use: DBX putty, Grafton DBM putty, and AlloMatrix putty. All three DBM formulations are produced from human donor tissue but they differ in the substitutes added. From each of the three products 10 different lots were analyzed. Protein was extracted from the samples with Guanidine HCL/EDTA method and human ELISA kits were used for growth factor quantification. Differences between the three different products were seen in total protein contend and the absolute growth factor values but also a large variability between the different lots was found. The order of the growth factors, however, is almost comparable between the materials. In the three investigated materials FGF basic and BMP-4 were not detectable in any analyzed sample. BMP-2 revealed the highest concentration extractable from the samples with approximately 3.6 microg/g tissue without a significant difference between the three DBM formulations. In DBX putty significantly more TGF-beta1 and FGFa were measurable compared to the two other DBMs. IGF-I revealed the significantly highest value in the AlloMatrix and PDGF in Grafton. No differences were accessed for VEGF. Due to the differences in the growth factor concentration between the individual samples, independently from the product formulation, further analyzes are required to optimize the clinical outcome of the used demineralized bone matrix.

Tailor-made tricalcium phosphate bone implant directly fabricated by a three-dimensional ink-jet printer

Rapid prototyping (RP) is a molding technique that builds a three-dimensional (3D) model from computer-aided design (CAD) data. We fabricated new tailor-made bone implants (TIs) from alpha-tricalcium phosphate powder using an RP ink-jet printer based on computed tomography (CT) data, and evaluated their safety and efficacy. CT data of the skulls of seven beagle dogs were obtained and converted to CAD data, and bone defects were virtually made in the skull bilaterally. TIs were designed to fit the defects and were fabricated using the 3D ink-jet printer with six horizontal cylindrical holes running through the implants, designed for possible facilitation of vascular invasion and bone regeneration. As a control, hydroxyapatite implants (HIs) were cut manually from porous hydroxyapatite blocks. Then, craniectomy was performed to create real skull defects, and TIs and HIs were implanted. After implantation, CT was performed regularly, and the animals were euthanized at 24 weeks. No major side effects were observed. CT analysis showed narrowing of the cylindrical holes; bony bridging between the implants and the temporal bone was observed only for TIs. Histological analysis revealed substantial new bone formation inside the cylindrical holes in the TIs, while mainly connective tissues invaded the porous structures in HIs. Bone marrow was observed only in TIs. Osteoclasts were seen to resorb regenerated bone from inside the cylindrical holes and to invade and probably resorb the TIs. These data suggest that TIs are a safe and effective bone substitute, possessing osteoconductivity comparable with that of HIs.

The osteogenic potential of adipose-derived stem cells for the repair of rabbit calvarial defects

INTRODUCTION

Bone replacement is often necessary during reconstruction of craniofacial anomalies or trauma. Adipose-derived stem cells (ASCs) possess osteogenic potential and are a promising cell source for bone tissue engineering. The present study was designed to assess the osteogenic potential and utility of using ASCs to regenerate bone in a rabbit calvarial defect model.

METHODS

Rabbit ASCs were seeded on gelatin foam (GF) scaffolds and induced in osteogenic medium containing bone morphogenetic protein (BMP)-2. Thirty-four 8-mm calvarial defects were randomly treated with autograft, no treatment, GF scaffold, GF + ASCs, or GF + osteoinduced ASCs. After 6 weeks, calvaria were harvested and underwent histologic and radiologic analyses to compare healing between the treatment groups.

RESULTS

Defects treated with autograft underwent complete healing. Radiologically, there were no significant (P > 0.05) differences in healing among empty defects, and those treated with GF alone or GF plus osteoinduced ASCs. Osteoinduced ASCs exhibited significantly (P < 0.05) greater healing than noninduced ASCs.

CONCLUSION

Preimplantation osteoinduction of ASCs enhances their osteogenic capacity. Lack of a significant osteogenic effect of ASCs on calvarial healing at 6 weeks may be secondary to use of noncritical-sized defects. Larger defects would likely demonstrate the osteogenic potential of ASCs more definitively.

Bioabsorbable scaffold for in situ bone regeneration

A non-porous poly-DL-lactide tubular chamber filled by demineralised bone matrix (DBM) and bone marrow stromal cells (BMSC) in combination, was evaluated as a scaffold for guided bone regeneration (GBR) in an experimental model using the rabbit radius. The tubular chamber had an internal diameter of 4.7 mm, a wall thickness of 0.4 mm and a length of 18 mm. Autologous BMSC were obtained, under general anaesthesia from rabbit iliac crest and isolated by centrifugation technique. Allogenic DBM was obtained from cortico-cancellous bone of rabbits. In general anaesthesia, a 10-mm defect was bilaterally created in the radii of 10 rabbits. On the right side (experimental side) the defect was bridged with the chamber filled with both BMSC and DBM. On the left side (control side) the defect was treated by positioning DBM and BMSC between the two stumps. At an experimental time of 4 months histology and histomorphometry demonstrated that the presence of a tubular chamber significantly improved bone regrowth in the defect The mean thickness of newly-formed bone inside the chamber was about 56.7+/-3.74% of the normal radial cortex, in comparison with 46.7+/-10.7% when DBM and BMSC without the chamber were placed in the defect, P<0.05). These results confirmed the effectiveness of the chamber as a container for factors promoting bone regeneration.