A quantitative assessment of osteoinductivity of human demineralized bone matrix

Characterization of an advanced bone graft material with a nanocrystalline hydroxycarbanoapatite surface and dual phase composition

The bone formation response of ceramic bone graft materials can be improved by modifying the material's surface and composition. A unique dual-phase ceramic bone graft material with a nanocrystalline, hydroxycarbanoapatite (HCA) surface and a calcium carbonate core (TrelCor®-Biogennix, Irvine, CA) was characterized through a variety of analytical methods. Scanning electron microscopy (SEM) of the TrelCor surface (magnification 100-100,000X) clearly demonstrated a nanosized crystalline structure covering the entire surface. The surface morphology showed a hierarchical structure that included micron-sized spherulites fully covered by plate-like nanocrystals (<60 nm in thickness). Chemical and physical characterization of the material using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy Energy Dispersive X-ray Spectroscopy (SEM-EDX) showed a surface composed of HCA. Analysis of fractured samples confirmed the dual-phase composition with the presence of a calcium carbonate core and HCA surface. An in vitro bioactivity study was conducted to evaluate whether TrelCor would form a bioactive layer when immersed in simulated body fluid. This response was compared to a known bioactive material (45S5 bioactive glass - Bioglass). Following 14-days of immersion, surface and cross-sectional analysis via SEM-EDX showed that the TrelCor material elicited a bioactive response with the formation of a bioactive layer that was qualitatively thicker than the layer that formed on Bioglass. An in vivo sheep muscle pouch model was also conducted to evaluate the ability of the material to stimulate an ectopic, cellular bone formation response. Results were compared against Bioglass and a first-generation calcium phosphate ceramic that lacked a nanocrystalline surface. Histology and histomorphometric analysis (HMA) confirmed that the TrelCor nanocrystalline HCA surface stimulated a bone formation response in muscle (avg. 11% bone area) that was significantly greater than Bioglass (3%) and the smooth surface calcium phosphate ceramic (0%).

Enhanced osteogenicity of the demineralized bone-dermal matrix composite by the optimal partial demineralization for sustained release of bioactive molecules

Allogenic demineralized bone matrix (DBM), processed to expose bioactive proteins imbedded by calcium salts, is widely used for bone repair and regeneration as an alternative to the autologous bone graft. However, demineralized bone matrices from tissue banks vary significantly in residual calcium content and osteogenicity for clinical bone regeneration. The present study produced DBM with various residual calcium contents by partial demineralization using ethylenediaminetetraacetic acid disodium (EDTA) and hydrochloric acid. Compositional analysis reveals that, as the percent weight loss of bone materials increases from 0% to 74.9% during demineralization, the residual calcium content of DBM decreases from 24.8% to 0.2% and collagen content increases from 29.7% to 92.6%. Calorimetrical analysis and Fourier transform infrared (FTIR) analysis demonstrated that demineralization to the residual calcium content of <4% enables the complete exposure and/or release of bone collagen fibers and other bioactive molecules. In order to evaluate the relationship between the extent of demineralization and the osteogenicity of DBM, DBM particles were fabricated with the aid of acellular dermal matrix (ADM) microfibers to form flexible foam-like DBM/ADM composites. Proteomic analysis identified various type collagens and bone formation-related bioactive molecules in both ADM and DBM. Using the rat bilateral Φ = 5 mm calvarium defect repair model, the study had shown that the DBM/ADM composite with ~20% DBM residual calcium (e.g., ~40% calcium being removed) maximized the osteogenicity for bone defect repair after 4 and 8 weeks. DBM with ~40% calcium removal had the maximal osteogenicity presumably through the sustained release of bioactive molecules during the process of bone regeneration.

Comparative Efficacy of Commonly Available Human Bone Graft Substitutes as Tested for Posterolateral Fusion in an Athymic Rat Model

Background

Insufficient data exist on bone graft substitute materials efficacy; two thirds lack any clinical data.1,2 This prospective animal study identified efficacy differences among commercially available materials of several classes.

Methods

Historically validated muscle pouch osteoinduction study (OIS) and posterolateral fusion (PLF) were performed in an athymic rat model. Grafting material products implanted were demineralized bone matrix (DBM)-based allografts (Accell EVO3, DBX Mix, DBX Strip, Grafton Crunch, Grafton Flex, Grafton Matrix, Grafton Putty, Magnifuse, and Progenix Plus), allografts (OsteoSponge, MinerOss), cellular allograft (Osteocel Plus), ceramics (Mozaik Strip), or activated ceramics (Actifuse ABX Putty, Vitoss BA). After 4 weeks, OIS specimens were evaluated ex vivo by histologic osteoinductivity. After 8 weeks, PLF ex vivo specimens were evaluated for fusion by manual palpation (F_MP), radiography (F_XR), and histology (F_HISTO).

Results

OIS: No materials exhibited a rejection reaction on histology. All DBM-based materials exhibited osteoinductive potential as new bone formation at > 88% of implanted sites. One plain allograft (OsteoSponge) formed bone at 25% of sites. No bone formed for one ceramic (Mozaik Strip), three activated ceramics (Actifuse ABX Putty), or one cellular allograft, regardless of human bone marrow aspirate (hBMA) when added. PLF: Among the 10 DBMs, 6 had F_MP of 100% (Accell EVO3, DBX Mix, DBX Strip, Grafton Flex, Grafton Putty, Magnifuse), 2 had F_MP of 94% (Grafton Crunch, Grafton Matrix), and 2 conditions had F_MP of 0% (Progenix Plus, Progenix Plus + athymic rat iliac crest bone graft [arICBG]). Ceramics (Mozaik Strip), activated ceramics (Actifuse ABX Putty, Vitoss BA), plain allograft (OsteoSponge, MinerOss (PLF study), and cellular allograft (Osteocel Plus) demonstrated 0% F_MP. ArICBG demonstrated 13% F_MP.

Conclusions

Eight DBM-based materials (Accell EVO3, DBX Mix, DBX Strip, Grafton Crunch, Grafton Flex, Grafton Matrix, Grafton Putty, Magnifuse) demonstrated excellent (> 90% F_MP) efficacy in promoting fusion via bone healing. Two DBM conditions (Progenix Plus, Progenix Plus + arICBG) showed no manual palpation fusion (F_MP). Systematically, over the 2 studies (OIS and PLF), cellular (Osteocel Plus), plain allografts (OsteoSponge, MinerOss; PLF study), ceramic (Mozaik Strip), and activated ceramics (Actifuse ABX Putty, Vitoss BA) demonstrated poor F_MP efficacy (< 10%).

Clinical Relevance

When selecting DBMs, clinicians must be cognizant of variability in DBM efficacy by product and lot. While theoretically osteoinductive, cellular allograft and activated ceramics yielded poor in vivo efficacy. Whole allograft and ceramics may provide osteoconductive scaffolding for mixed-material grafting; however, surgeons should be cautious in using them alone. Direct clinical data are needed to establish efficacy for any bone graft substitute.

Enhanced osteoinductive capacity and decreased variability by enrichment of demineralized bone matrix with a bone protein extract

Osteoinductive capacity of demineralized bone matrix (DBM) is sometimes insufficient or shows high variability between different batches of DBM. Here, we tried to improve its osteoinductive activity by alkali-urea or trypsin treatment but this strategy was unsuccessful. Then, we tested the enrichment of DBM with a bone protein extract (BPE) containing osteogenic growth factors comparing two sources: cortical bone powder and DBM. The osteoinductive capacity (alkaline phosphatase activity) of the obtained BPEs was evaluated in vitro in C2C12 cells. Specific protein levels present in the different BPE was determined by enzyme-linked immunosorbent assay or by a multiplex assay. BPE from cortical bone powder showed a lack of osteoinductive effect, in agreement with the low content on osteoinductive factors. In contrast, BPE from DBM showed osteoinductive activity but also high variability among donors. Thus, we decided to enrich DBM with BPE obtained from a pool of DBM from different donors. Following this strategy, we achieved increased osteoinductive activity and lower variability among donors. In conclusion, the use of a BPE obtained from a pool of demineralized bone to enrich DBM could be used to increase its osteoinductive effect and normalize the differences between donors.

The Poor Osteoinductive Capability of Human Acellular Bone Matrix

Demineralized bone matrix (DBM) has extensive clinical use for bone regeneration because of its osteoinductive and osteoconductive aptitude. It is suggested that the demineralization process in bone matrix preparation is influential in maintaining osteoinductivity; however, relevant investigations, especially into the osteoinductivity of acellular bone matrix, are not often performed. This study addressed the osteoinductive capability of human acellular cancellous bone matrix (ACBM) after subcutaneous implantation in a rat model. The growth and osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBM-MSCs) seeded in this material were also studied. Without the demineralization process, the ACBM we obtained had an interconnected porous network and the micropores in the surface were clearly exposed. After the ACBM was subcutaneously implanted for 4 months, new osteoid formation was noted but not typical mature bone formation. rBM-MSCs grew well in the ACBM and kept a steady morphology after continuous culture for 28 days. However, no mineralized nodule formation was detected and the expression levels of genes encoding osteogenic markers were significantly decreased. These results demonstrated that human ACBM possess the structural features of native bone and poor osteoinductivity; nonetheless this material helped to preserve the undifferentiated phenotype of rBM-MSCs. Such insights may further broaden our understanding of the application of ACBM for bone regeneration and the creation of stem cell niches.

An Approach to In Vitro Manufacturing of Hypertrophic Cartilage Matrix for Bone Repair

Devitalized hypertrophic cartilage matrix (DCM) is an attractive concept for an off-the-shelf bone graft substitute. Upon implantation, DCM can trigger the natural endochondral ossification process, but only when the hypertrophic cartilage matrix has been reconstituted correctly. In vivo hypertrophic differentiation has been reported for multiple cell types but up-scaling and in vivo devitalization remain a big challenge. To this end, we developed a micro tissue-engineered cartilage (MiTEC) model using the chondrogenic cell line ATDC5. Micro-aggregates of ATDC5 cells (approximately 1000 cells per aggregate) were cultured on a 3% agarose mold consisting of 1585 microwells, each measuring 400 µm in diameter. Chondrogenic differentiation was strongly enhanced using media supplemented with combinations of growth factors e.g., insulin, transforming growth factor beta and dexamethasone. Next, mineralization was induced by supplying the culture medium with beta-glycerophosphate, and finally we boosted the secretion of proangiogenic growth factors using the hypoxia mimetic phenanthroline in the final stage of in vivo culture. Then, ATDC5 aggregates were devitalized by freeze/thawing or sodium dodecyl sulfate treatment before co-culturing with human mesenchymal stromal cells (hMSCs). We observed a strong effect on chondrogenic differentiation of hMSCs. Using this MiTEC model, we were able to not only upscale the production of cartilage to a clinically relevant amount but were also able to vary the cartilage matrix composition in different ways, making MiTEC an ideal model to develop DCM as a bone graft substitute.

Human tooth-derived biomaterial as a graft substitute for hard tissue regeneration

Aim: The present study was conducted to evaluate the efficacy of human dentine grafts for new bone augmentation. Materials & methods: Dentine grafts (demineralized dentine matrix [DDM] and mineralized dentine matrix [MDM]) were prepared and implanted in rats. Tetracycline was administered twice. Paraffin and resin sections were prepared from the harvested grafts and stained respectively with hematoxylin and eosin (in addition to tartrate acid phosphatase for osteoclasts) and Villanueva. The new bone formation (bone thickness, mineral apposition rate and the bone formation rate) was analyzed in tetracycline-labeled resin sections. Results & conclusion: DDM grafts implanted in bone were better able to augment the bone compared to MDM grafts. However, both MDM and DDM failed to induce new bone in ectopic site, they could be considered as alternative autograft substitutes after protocol optimization.

Guided "sandwich" technique: a novel surgical approach for safe osteotomies in the treatment of vertical bone defects in the posterior atrophic mandible: a case report

PURPOSE

A novel technique to perform safe osteotomies during inlay block regenerative procedures in the posterior atrophic mandible is described.

MATERIAL AND METHODS

A 52-year-old male patient with vertical atrophy of the left posterior mandible was treated adopting an inlay block "sandwich" technique using an allogenic cancelous block and a mixture of mineralized and demineralized human bone allograft in putty form as graft. The horizontal osteotomy for the lifting of the osteotomized bone segment was performed using a template prepared from a virtual anatomical replica of the patient's mandible obtained from cone beam computed tomography data. In the second surgical phase, 3 months after the augmentation, 2 implants were easily placed.

RESULTS

The horizontal osteotomy was carried out, with no risk, very close to the nerve structures after the precise osteotomy line established preoperatively on the three-dimensional computed tomography (3D-CT) virtual reconstruction. No neurological complications were observed in the first days after the procedure, and no subsequent problems were recorded during the 3-month healing period.

CONCLUSION

Radiographic evaluations and complication-free clinical healing demonstrate the effectiveness of this technique to obtain safe and precise osteotomies.

The effect of carrier type on bone regeneration of demineralized bone matrix in vivo

Demineralized bone matrix (DBM) is a bone substitute biomaterial used as an excellent grafting material. Some factors such as carrier type might affect the healing potential of this material. The background data discuss the present status of the field: Albumin as a main protein in blood and carboxymethyl cellulose (CMC) were applied frequently in the DBM gels. We investigated the bone-repairing properties of 2 DBMs with different carriers. Bone regeneration in 3 groups of rat calvaria treated with DBM from the Iranian Tissue Bank Research and Preparation Center, DBM from Hans Biomed Corporation, and an empty cavity was studied. Albumin and CMC as carriers were used. The results of bone regeneration in the samples after 1, 4, and 8 weeks of implantation were compared. The block of the histologic samples was stained with hematoxylin and eosin, and the percentage area of bone formation was calculated using the histomorphometry method. The results of in vivo tests showed a significantly stronger new regenerated bone occupation in the DBM with albumin carrier compared with the one with CMC 8 weeks after the implantation. The 2 types of DBM had a significant difference in bone regeneration. This difference is attributed to the type of carriers. Albumin could improve mineralization and bioactivity compared with CMC.

Comparison of the osteogenic potential of OsteoSelect demineralized bone matrix putty to NovaBone calcium-phosphosilicate synthetic putty in a cranial defect model

The purpose of this study was to compare the osteogenic potential of a synthetic and a demineralized bone matrix (DBM) putty using a cranial defect model in New Zealand white rabbits. Paired, bilateral critical-size defects (10 mm) were prepared in the frontal bones of 12 rabbits and filled with either OsteoSelect DBM Putty or NovaBone calcium-phosphosilicate putty. At days 43 and 91, 6 rabbits were killed and examined via semiquantitative histology and quantitative histomorphometry. Defects filled with the DBM putty were histologically associated with less inflammation and fibrous tissue in the defect and more new bone than the synthetic counterpart at both time points. Histomorphometric analysis revealed that the defects filled with DBM putty were associated with significantly more bone formation at day 43 (70.7% vs 40.7%, P = 0.043) and at day 91 (70.4% vs 39.9%, P = 0.0044). The amount of residual implant was similar for both test groups at each time point.

Decellularized tissue and cell-derived extracellular matrices as scaffolds for orthopaedic tissue engineering

The reconstruction of musculoskeletal defects is a constant challenge for orthopaedic surgeons. Musculoskeletal injuries such as fractures, chondral lesions, infections and tumor debulking can often lead to large tissue voids requiring reconstruction with tissue grafts. Autografts are currently the gold standard in orthopaedic tissue reconstruction; however, there is a limit to the amount of tissue that can be harvested before compromising the donor site. Tissue engineering strategies using allogeneic or xenogeneic decellularized bone, cartilage, skeletal muscle, tendon and ligament have emerged as promising potential alternative treatment. The extracellular matrix provides a natural scaffold for cell attachment, proliferation and differentiation. Decellularization of in vitro cell-derived matrices can also enable the generation of autologous constructs from tissue specific cells or progenitor cells. Although decellularized bone tissue is widely used clinically in orthopaedic applications, the exciting potential of decellularized cartilage, skeletal muscle, tendon and ligament cell-derived matrices has only recently begun to be explored for ultimate translation to the orthopaedic clinic.

Guided bone regeneration using demineralized allogenic bone matrix with calcium sulfate: case series

PURPOSE

The purpose of this case series was to evaluate the effect of guided bone regeneration using demineralized allogenic bone matrix with calcium sulfate.

MATERIALS AND METHODS

Guided bone regeneration using Demineralized Allogenic Bone Matrix with Calcium Sulfate (AlloMatrix™, Wright. USA) was performed at the time of implant placement from February 2010 to April 2010. At the time of the second surgery, clinical evaluation of bone healing and histologic evaluation were performed. The study included 10 patients, and 23 implants were placed. The extent of bony defects around implants was determined by measuring the horizontal and vertical bone defects using a periodontal probe from the mesial, distal, buccal, and lingual sides and calculating the mean and standard deviation of these measurements. Wedge-shaped tissue samples were obtained from 3 patients and histologic examination was performed.

RESULTS

In clinical evaluation, it was observed that horizontal bone defects were completely healed with new bones, and in the vertical bone defect area, 15.1% of the original defect area remained. In 3 patients, histological tests were performed, and 16.7-41.7% new bone formation was confirmed. Bone graft materials slowly underwent resorption over time.

CONCLUSION

AlloMatrix™ is an allograft material that can be readily manipulated. It does not require the use of barrier membranes, and good bone regeneration can be achieved with time.

In vitro assay for osteoinductive activity of different demineralized freeze-dried bone allograft

PURPOSE

Various bone graft materials have been used for periodontal tissue regeneration. Demineralized freeze-dried bone allograft (DFDBA) is a widely used bone substitute. The current widespread use of DFDBA is based on its potential osteoinductive ability. Due to the lack of verifiable data, the purpose of this study was to assess the osteoinductive activity of different DFDBAs in vitro.

METHODS

Sarcoma osteogenic (SaOS-2) cells (human osteoblast-like cells) were exposed to 8 mg/mL and 16 mg/mL concentrations of three commercial types of DFDBA: Osseo+, AlloOss, and Cenobone. The effect of these materials on cell proliferation was determined using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. The osteoinductive ability was evaluated using alizarin red staining, and the results were confirmed by evaluating osteogenic gene expression using reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

In the SaOS-2 cells, an 8 mg/mL concentration of Osseo+ and Cenobone significantly increased cell proliferation in 48 hours after exposure (P<0.001); however, in these two bone materials, the proliferation of cells was significantly decreased after 48 hours of exposure with a 16 mg/mL concentration (P<0.001). The alizarin red staining results demonstrated that the 16 mg/mL concentration of all three tested DFDBA induced complete morphologic differentiation and mineralized nodule production of the SaOS-2 cells. The RT-PCR results revealed osteopontin gene expression at a 16 mg/mL concentration of all three test groups, but not at an 8 mg/mL concentration.

CONCLUSIONS

These commercial types of DFDBA are capable of decreasing proliferation and increasing osteogenic differentiation of the SaOS-2 cell line and have osteoinductive activity in vitro.

Demineralized bone matrix in bone repair: history and use

Demineralized bone matrix (DBM) is an osteoconductive and osteoinductive commercial biomaterial and approved medical device used in bone defects with a long track record of clinical use in diverse forms. True to its name and as an acid-extracted organic matrix from human bone sources, DBM retains much of the proteinaceous components native to bone, with small amounts of calcium-based solids, inorganic phosphates and some trace cell debris. Many of DBM's proteinaceous components (e.g., growth factors) are known to be potent osteogenic agents. Commercially sourced as putty, paste, sheets and flexible pieces, DBM provides a degradable matrix facilitating endogenous release of these compounds to the bone wound sites where it is surgically placed to fill bone defects, inducing new bone formation and accelerating healing. Given DBM's long clinical track record and commercial accessibility in standard forms and sources, opportunities to further develop and validate DBM as a versatile bone biomaterial in orthopedic repair and regenerative medicine contexts are attractive.

Demineralized bone matrix as a vehicle for delivering endogenous and exogenous therapeutics in bone repair

As a unique human bone extract approved for implant use, demineralized bone matrix (DBM) retains substantial amounts of endogenous osteoconductive and osteoinductive proteins. Commercial preparations of DBM represent a clinically accessible, familiar, widely used and degradable bone-filling device, available in composite solid, strip/piece, and semi-solid paste forms. Surgically placed and/or injected, DBM releases its constituent compounds to bone sites with some evidence for inducing new bone formation and accelerating healing. Significantly, DBM also has preclinical history as a drug carrier by direct loading and delivery of several important classes of therapeutics. Exogenous bioactive agents, including small molecule drugs, protein and peptide drugs, nucleic acid drugs and transgenes and therapeutic cells have been formulated within DBM and released to bone sites to enhance DBM's intrinsic biological activity. Local release of these agents from DBM directly to surgical sites in bone provides improved control of dosing and targeting of both endogenous and exogenous bioactivity in the context of bone healing using a clinically familiar product. Given DBM's long clinical track record and commercial accessibility in standard forms and sources, opportunities to formulate DBM as a versatile matrix to deliver therapeutic agents locally to bone sites in orthopedic repair and regenerative medicine contexts are attractive.

Feasibility of demineralized bone matrix for craniomaxillofacial contour restoration

Demineralized bone matrix (DBM) could be a good alternative for craniomaxillofacial contour restoration, especially in perialar, malar, temporal, and frontal regions. In this study, the histologic behavior of DBM was investigated in different tissue planes to determine its proper application plane for restoration of craniomaxillofacial contour deformities and defects.Forty Wistar rats were divided into 6 groups: (1) 0.3 mL of 0.9% saline was injected into the subperiosteal plane of the cranium, (2) 0.3 mL of DBM was implanted into the subperiosteal plane of the cranium, (3) 0.3 mL of 0.9% saline was injected into the subdermal plane on the left inguinal region, (4) 0.3 mL of DBM was implanted into the subdermal plane on the right inguinal region, (5) 0.3 mL of 0.9% saline was injected between the left external and internal oblique muscles, and (6) 0.3 mL of DBM was implanted between the right external and internal oblique muscles. At the 8th week half of the rats and at 16th week the remaining rats were killed in each group, and tissue samples were harvested. Histological and immunohistochemical evaluation revealed new bone tissue and bone marrow formation in all planes that DBM was given.Demineralized bone matrix can provide satisfactory results in craniomaxillofacial contour deformities including forehead, temporal, and malar augmentations, as well as mental and perialar augmentations and saddle nose corrections, with supraperiosteal or deep subcutaneous applications. However, superficial applications must be avoided because of the possibility of palpation, because it induces hard bone tissue formation in all tissue planes.

Osteoinductivity of demineralized bone matrix is independent of donor bisphosphonate use

BACKGROUND

Demineralized bone matrix is commonly used as a bone graft substitute, either alone or to supplement an osteoconductive material, because of its osteoinductive properties. The aging of the population has led to an increase in the number of prospective donors of demineralized bone matrix who have taken bisphosphonates to prevent osteoclast-mediated bone resorption. The aim of this study was to determine whether oral bisphosphonate usage affects the osteoinductivity of demineralized bone matrix from donors.

METHODS

Sex-matched and age-matched pairs of samples were provided by four tissue banks (three or four pairs per bank). Demineralized bone matrix donors without bisphosphonate treatment had a mean age (and standard deviation) of 69.1 ± 2.5 years, and donors with bisphosphonate treatment had a mean age of 68.9 ± 2.0 years. Each pair included one donor known to have taken bisphosphonates and one who had not taken bisphosphonates. Demineralized bone matrix previously confirmed as osteoinductive was the positive control, and heat-inactivated demineralized bone matrix was the negative control. Demineralized bone matrix incubated with 1 mL of phosphate-buffered saline solution containing 0, 0.002, 2.0, or 2000 ng/mL of alendronate was also tested. Gelatin capsules containing 15 mg of demineralized bone matrix were implanted bilaterally in the gastrocnemius muscle of male nude mice (eight implants per group). The mice were killed thirty-five days after implantation, and hind limbs were recovered and processed for histological analysis. Osteoinductivity was measured with use of a qualitative score and by histomorphometry.

RESULTS

Nine of fifteen samples from donors who had had bisphosphonate treatment and ten of fifteen samples from patients who had not had bisphosphonate treatment were osteoinductive. Qualitative mean scores were comparable (1.7 ± 0.4 for those without bisphosphonates and 1.9 ± 0.7 for those with bisphosphonates). Osteoinductive demineralized bone matrix samples produced ossicles of comparable size, regardless of bisphosphonate usage. Histomorphometric measurements of the area of new bone formation and residual demineralized bone matrix were also comparable. The addition of alendronate to control demineralized bone matrix did not affect its osteoinductivity.

CONCLUSIONS

Demineralized bone matrix samples from donors treated with bisphosphonates and donors not treated with bisphosphonates have the same ability to induce bone formation. However, it is not known if the quality of the new bone is affected, with subsequent consequences affecting bone remodeling.

Osteogenic activity of β-tricalcium phosphate in a hydroxyl sulphate matrix and demineralized bone matrix: a histological study in rabbit mandible

Currently, in oral and maxillofacial surgery, there is a clinical need for efficient bone grafting materials, and various efforts are being made to improve materials used as bone substitutes to facilitate faster and denser bone regeneration. The purpose of this study was to evaluate in vivo the osteogenic potential of synthetic β-tricalcium phosphate in a hydroxyl sulphate matrix (β-TCP/HS) and human demineralized bone matrix (DBM) putty. Sixteen New Zealand White rabbits were used. In each animal, two bone defects (8 mm length × 3 mm width × 3 mm depth) were created in the left and right regions of the mandible, respectively. The defect on one side, chosen randomly, was filled with β-TCP/HS (group A) or DBM putty (group B), while the defect on the opposite side was left unfilled in order to serve as a control site. Two animals in each group were sacrificed at the end of the 1st, 3rd, 5th and 6th week after surgery, respectively, and the osteotomy sites were processed for histological evaluation. Our findings confirmed that β-TCP/HS and human DBM putty possess osteogenic activity and can support new bone formation, although at a slower rate than the spontaneous healing response, in rabbit mandibular osseous defects.

Repair of long bone defects with demineralized bone matrix and autogenous bone composite

BACKGROUND

Repair of diaphyseal bone defects is a challenging problem for orthopedic surgeons. In large bone defects the quantity of harvested autogenous bone may not be sufficient to fill the gap and then the use of synthetic or allogenic grafts along with autogenous bone becomes mandatory to achieve compact filling. Finding the optimal graft mixture for treatment of large diaphyseal defects is an important goal in contemporary orthopedics and this was the main focus of this study. The aim of this study is to investigate the efficacy of demineralized bone matrix (DBM) and autogenous cancellous bone (ACB) graft composite in a rabbit bilateral ulna segmental defect model.

MATERIALS AND METHODS

Twenty-seven adult female rabbits were divided into five groups. A two-centimeter piece of long bone on the midshaft of the ulna was osteotomized and removed from the rabbits' forearms. In group 1 (n=7) the defects were treated with ACB, in group 2 (n=7) with DBM, and in group 3 (n=7) with ACB and DBM in the ratio of 1:1. Groups 4 and 5, with three rabbits in each group, were the negative and positive controls, respectively. Twelve weeks after implantation the rabbits were sacrificed and union was evaluated with radiograph (Faxitron), dual-energy x-ray absorptiometry (DEXA), and histological methods (decalcified sectioning).

RESULTS

UNION RATES AND THE VOLUME OF NEW BONE IN THE DIFFERENT GROUPS WERE AS FOLLOWS: group 1 - 92.8% union and 78.6% new bone; group 2 - 72.2% union and 63.6% new bone; and group 3 - 100% union and 100% new bone. DEXA results (bone mineral density [BMD]) were as follows: group 1 - 0.164 g/cm(2), group 2 - 0.138 g/cm(2), and group 3 - 0.194 g/cm(2).

CONCLUSIONS

DBM serves as a graft extender or enhancer for autogenous graft and decreases the need of autogenous bone graft in the treatment of bone defects. In this study, the DBM and ACB composite facilitated the healing process. The union rate was better with the combination than with the use of any one of these grafts alone.

Demineralized bone matrix for fracture healing: fact or fiction?

Demineralized bone matrix (DBM) has been touted as an excellent grafting material; however, there are no Level I studies that use DBM alone in humans to back up this claim. DBM functions best in a healthy tissue bed but should be expected to have little impact in an anoxic or avascular tissue bed, a situation often encountered in traumatic orthopaedic pathologies. Moreover, there is some evidence of differential potencies of DBM preparations based on donor variability and the manufacturing process. DBM efficacy may also be related to its formulation and the various carriers used. The fact that DBM is an allogeneic material opens up the potential for disease transmission. In addition, DBM activity may be altered by the hormonal status or nicotine use of a patient. In summary, although DBM has proven effective for bone induction in lower form animals, the translation to human clinical use for fracture healing, and the burden of proof, remains.

Biomechanical and Radiographic Comparison of Demineralized Bone Matrix, and a Coralline Hydroxyapatite in a Rabbit Spinal Fusion Model

The use of bone grafts is an essential component in spinal fusion. Autologous bone has been shown to result in long-term stable arthrodesis between spinal motion segments. However, autograft can be associated with significant morbidity and a limited supply. Alternatives, such as allogeneic demineralized bone matrix (DBM), are a potential source and supplement to autograft bone. The current study compares the ability of a DBM product (BioSet® RT) and a coralline hydroxyapatite (Pro Osteon® 500R), for inducing spinal fusion in a rabbit model. BioSet® RT, alone or in combination with autograft, and Pro Osteon® 500R were implanted in the posterior lateral inter-transverse process region of the rabbit spine. The spines were evaluated at 18 weeks for fusion of the L4—L5 transverse processes using a total of 33 skeletally mature male rabbits; 4 naïve animals were also included in the study. Samples were evaluated radiographically, histologically, by palpation, and through mechanical strength testing. Radiographical, histological, and palpation measurements demonstrated the ability of BioSet® RT to induce new bone formation and bridging fusion comparable to autograft. This material performed well alone or in combination with autograft material. Despite significantly higher biomechanical testing results, minimal bone formation and fusion was recorded for the Pro Osteon® 500R-treated group. This in vivo study demonstrates the ability of BioSet®RT to induce new bone formation, and there was a clear relationship between bridging bone and mechanical strength.

Histological and radiographic evaluations of demineralized bone matrix and coralline hydroxyapatite in the rabbit tibia

Complex fractures resulting in bone loss or impaired fracture healing remain problematic in trauma and orthopedic surgeries. Many bone graft substitutes have been developed and are commercially available. These products differ in their osteoconductive and osteoinductive properties. Differential enhancement of these properties may optimize the performance of these products for various orthopedic and craniofacial applications. The use of bone graft substitutes offers the ability to lessen the possible morbidity of the harvest site in autografts. The objective of the present study was to compare the ability of two bone graft substitutes, BioSet RT, an allograft demineralized bone matrix formulation, and ProOsteon 500R, a coralline hydroxyapatite, in a rabbit critical tibial defect model. BioSet RT and ProOsteon 500R were implanted into a unicortical proximal metaphyseal tibial defect and evaluated for new bone formation. Samples were analyzed radiographically and histologically at 1 day, 6 weeks, 12 weeks, and 24 weeks post surgery. Both materials were biocompatible and demonstrated significant bone growth and remodeling. At 12 weeks, the BioSet RT implanted sites demonstrated significantly more defect closure and bone remodeling as determined by radiographic analyses with 10 out of 14 defects being completely healed versus 1 out of 14 being completely healed in the ProOsteon 500R implanted sites. At 24 weeks, both materials demonstrated complete closure of the defect as determined histologically. There were no statistical differences in radiographic scores between the two implanted materials. However, there was an observable trend that the BioSet RT material generated higher histological and radiographic scores, although not statistically significant. This study provides evidence that both BioSet RT and ProOsteon 500R are biocompatible and able to induce new bone formation as measured in this rabbit model. In addition, this in vivo study demonstrates the ability of BioSet RT to induce new bone formation in a shorter timeframe than ProOsteon 500R.

Evaluation of demineralised, freeze-dried, irradiated bone allografts in the treatment of osseous defects in the oral cavity

Demineralised, freeze-dried bone allografts (DFDBA) have been used extensively by dentists in the treatment of periodontal and periapical osseous defects resulting from inflammatory diseases. Their use in India however, is limited by the availability of quality allografts and the high cost of imported alternatives. A study was conducted to assess the osteogenic potential of DFDBA prepared for the first time in India by the Tata Memorial Hospital (TMH) Tissue Bank. The DFDBA was used in the treatment of osseous defects after removal of periapical lesions associated with devitalised teeth in 10 healthy patients. At the 6-month recall visit all the patients showed a remarkable decrease in the grades of mobility, and 9 out of the 10 patients showed radiographic evidence of complete healing of the osseous defects with evidence of normal bony trabaeculae. These findings indicate that the indigenously prepared DFDBA is a cost effective, biocompatible material with osteogenic potential that can be used effectively in treating osseous defects of periapical lesions associated with non vital teeth.

C-Graft in regeneration of periodontal tissue in intrabony periodontal defect in dog

The aim of this study was to investigate the effect of C-Graft particles on formation of new cementum and bone in periodontal bone defects in dog. Healing and tissue change were histologically determined at 2, 4, 8, and 16 weeks. Little bone or cementum formation was observed in the control group. A statistically significant increase in bone and cementum formation was seen in the C-Graft group compared to the control group (75.4% vs. 44.9%, p < 50.01, 80.4% vs. 46.7%, p < 50.05, respectively). These findings suggest that C-Graft particles provide a scaffold for the regeneration of new bone and cementum.

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.

Review: Mineralization of Synthetic Polymer Scaffolds for Bone Tissue Engineering

It has repeatedly been shown that demineralization improves the ability of bone auto- and allografts to regenerate natural bone tissue. Conversely, much work in the field of bone tissue engineering has used composite materials consisting of a mineralized phase or materials designed to mineralize rapidly in situ. In this review, we seek to examine these disparate roles of mineralization and the underlying factors that cause this discordance and to examine methods and principles of the mineralization of synthetic polymer scaffolds. Biomimetic approaches to mineralization and phosphorus-containing materials are highlighted, and a brief section focusing on drug-delivery strategies using mineralized scaffolds is included.

Safety and efficacy of use of demineralised bone matrix in orthopaedic and trauma surgery

Demineralised bone matrix (DBM) acts as an osteoconductive, and possibly as an osteoinductive, material. It is widely used in orthopaedic, neurosurgical, plastic and dental areas. More than 500,000 bone grafting procedures with DBM are performed annually in the US. It does not offer structural support, but it is well suited for filling bone defects and cavities. The osteoinductive nature of DBM is presumably attributed to the presence of matrix-associated bone morphogenetic proteins (BMPs) and growth factors, which are made available to the host environment by the demineralisation process. Clinical results have not been uniformly favourable; however, a variable clinical response is attributed partly to nonuniform processing methods found among numerous bone banks and commercial suppliers. DBMs remain reasonably safe and effective products. The ultimate safe bone-graft substitute, one that is osteoconductive, osteoinductive, osteogenic and mechanically strong, remains elusive.

Calcium sulfate–carboxymethylcellulose bone graft binder: Histologic and morphometric evaluation in a critical size defect

Calcium sulfate (CS) is widely used as a bone graft binder and expander. Recent reports indicate that carboxymethylcellulose (CMC) can improve the clinical properties of CS when used as binder for particulate bone grafts; however, limited information is available on the effects of CMC on bone regeneration. The purpose of this study was to evaluate the histologic and morphometric characteristics of bone formation in calvarial defects grafted with a CS-based putty containing 10% CMC in combination with allogeneic demineralized bone matrix (DBM). Bone formation and graft/binder resorption were compared with a surgical grade CS and DBM in paired critical-sized calvarial defects in 25 Wistar rats (350-450 g). Six animals each provided paired defects at 7, 14, 21, and 28 days postsurgery for nondecalcified processing and microscopic analysis. Defects grafted with CS or CS-CMC putty as the DBM binder exhibited similar patterns and proportions of bone formation, fibrous tissue/marrow, and residual DBM particles. Comparable mean +/- SD proportions of new bone formation (31.7 +/- 9.5 and 33.7 +/- 12.9), fibrous tissue/marrow (54.2 +/- 8.3 and 53.0 +/- 10.8), residual DBM particles (8.3 +/- 6.8 and 10.1 +/- 6.3), and residual binder material (5.5 +/- 4.6 and 3.7 +/- 3.5) were found at 28 days for defects grafted with CS and CS-CMC putty, respectively. Thus, CMC was found to improve the handling characteristics of CS and, when used in conjunction with DBM, supported comparable levels bone formation and patterns of binder/scaffold resorption as CS and DBM in a calvarial defect model.

Osteoinductivity of demineralized bone matrix in immunocompromised mice and rats is decreased by ovariectomy and restored by estrogen replacement

The osteoinduction potential of human demineralized bone matrix (DBM) in females with low estrogen (E2) is unknown. Moreover, the osteoinductivity of commercial human DBM is tested in male athymic rats and mice, but DBM performance in these animals may not reflect performance in female animals or provide information on E2's role in the process. To gain insight, human DBM was implanted bilaterally in the gastrocnemius of twenty-four athymic female mice (10 mg/implant) and twenty-four athymic female rats (15 mg/implant). Eight animals in each group were sham-operated (SHAM), ovariectomized (OVX), or ovariectomized with E2-replacement (OVX+E2) via subcutaneous slow release capsules of 17beta-estradiol. OVX and OVX+E2 animals were pair-fed to SHAM animals. Four animals from each group were euthanized at 35 days and four at 56 days. Animal weight, uterine weight, and blood estrogen levels confirmed that pair feeding, ovariectomy, and E2 replacement were successful. Histological sections of implanted tissues were evaluated qualitatively for absence or presence of DBM, ossicle formation, and new bone or cartilage using a previously developed qualitative scoring system (QS) and by histomorphometry to obtain a quantitative assessment of osteoinduction. OVX mice had a small but significant QS decrease at 35 days compared to SHAM mice, confirmed by quantitative measurement of ossicle, marrow space, and new bone areas. The QS in rats was not affected by OVX but histomorphometry showed decreased new bone in OVX rats, which was restored by E2. The QS indicated that the number of new bone sites was not reduced by OVX in rats or mice at 56 days, but the relative amount of new bone v. marrow space was affected and differed with animal species. Residual DBM was less in OVX animals, indicating that DBM resorption was affected. Cartilage was present in rats but not in mice, suggesting that endochondral ossification was slower and indicating that bone graft studies in these species are not necessarily comparable. These results show the importance of E2 in human DBM-induced bone formation and suggest that E2 may be needed for clinical effectiveness in post-menopausal women.

The effect of demineralized bone matrix-calcium sulfate with vancomycin on calcaneal fracture healing and infection rates: a prospective study

BACKGROUND

Displaced intra-articular calcaneal fractures may have a central cancellous bone defect area. We hypothesized that human demineralized bone matrix (DBM) calcium sulfate (CaSO(4)) might act as a reasonable alternative to autograft in calcaneal fractures. When combined with antibiotic powder, this bone graft substitute also may act as a local antibiotic delivery device. This is the first clinical study evaluating bone healing and complications associated with DBM-calcium sulfate bone graft substitute in the treatment of displaced intra-articular calcaneal fractures with a central cancellous bone defect.

METHODS

Over a 29-month period, 33 displaced intra-articular calcaneal fractures with central cancellous defects were treated with open reduction and internal fixation (ORIF) and grafting with vancomycin/DBM-calcium sulfate bone graft substitute. Eleven fractures without bone defects were treated with ORIF only. Patient demographics, medical history, and CT fracture classification were recorded. Postoperatively, fractures were monitored every 2 weeks for healing and complications.

RESULTS

The mean time to union was 8.2 weeks in the grafted, while the control group mean time to union was 10.4 weeks (p = 0.0117). Wound problems occurred in five (15%) of the 33 patients with grafting, all in type III fractures with severe soft-tissue swelling, and included two minor wound healing delays, and three serious wound problems. At a mean followup time of 22.4 months, no DBM-calcium sulfate grafted calcaneus demonstrated evidence of osteomyelitis.

CONCLUSIONS

This is the first study examining human DBM-calcium sulfate bone graft substitute to treat displaced intra-articular calcaneal fractures. Based on these initial data, human DBM-calcium sulfate acted as an acceptable and safe autograft alternative in displaced intra-articular calcaneal fractures with moderate (5 cc to 10 cc) central cancellous bone defects.

Use of growth factors to modify osteoinductivity of demineralized bone allografts: lessons for tissue engineering of bone

Biologically active bone graft substitute materials are needed for repair and regeneration of skeletal tissues. Current approaches are focused on the use of osteoinductive agents, including bone morphogenetic proteins (BMP) in combination with biodegradable carriers. Demineralized freeze-dried bone allograft (DFDBA) can provide an osteoconductive surface and, at the same time, function as a time-release carrier for BMP. Donor variability, however, limits the predictability of DFDBA as an osteoinductive material. This article examines the use of growth factors, including platelet-rich plasma, platelet-derived growth factor, enamel matrix derivatives, and BMP-2, to enhance the osteoinductive properties of human DFDBA.

Intervariability and intravariability of bone morphogenetic proteins in commercially available demineralized bone matrix products

STUDY DESIGN

Enzyme-linked immunosorbent assay was used to detect bone morphogenetic proteins (BMPs) 2, 4, and 7 in 9 commercially available ("off the shelf") demineralized bone matrix (DBM) product formulations using 3 different manufacturer's production lots of each DBM formulation.

OBJECTIVES

To evaluate and compare the quantity of BMPs among several different DBM formulations (inter-product variability), as well as examine the variability of these proteins in different production lots within the same DBM formulation (intra-product variability).

SUMMARY OF BACKGROUND DATA

DBMs are commonly used to augment available bone graft in spinal fusion procedures. Surgeons are presented with an ever-increasing variety of commercially available human DBMs from which to choose. Yet, there is limited information on a specific DBM product's osteoinductive efficacy, potency, and constancy.

METHODS

There were protein extracts from each DBM sample separately dialyzed 4 times against distilled water at 4 degrees C for 48 hours. The amount of BMP-2, BMP-4, and BMP-7 was determined using enzyme-linked immunosorbent assay. RESULTS.: The concentrations of detected BMP-2 and BMP-7 were low for all DBM formulations, only nanograms of BMP were extracted from each gram of DBM (20.2-120.6 ng BMP-2/g DBM product; 54.2-226.8 ng BMP-7/g DBM). The variability of BMP concentrations among different lots of the same DBM formulation, intra-product variability, was higher than the variability of concentrations among different DBM formulations, inter-product variability (coefficient of variation range BMP-2 [16.34% to 76.01%], P < 0.01; BMP-7 [3.71% to 82.08%], P < 0.001). BMP-4 was undetectable.

CONCLUSIONS

The relative quantities of BMPs in DBMs are low, in the order of 1 x 10(-9) g of BMP/g of DBM. There is higher variability in concentration of BMPs among 3 different lots of the same DBM formulation than among different DBM formulations. This variability questions DBM products' reliability and, possibly, efficacy in providing consistent osteoinduction.

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

Bone healing is a complex and multifactorial process. As such, there are numerous steps in the process to which intervention can be directed. This has given rise to many bone graft technologies that have been used to regenerate bone, creating, perhaps, a bewildering array of options. The options that surgeons have the most familiarity with are the ones that have been available the longest (i.e., autograft and allograft). Although useful for the widest spectrum of clinical applications, limitations of these grafts has prompted the development of new materials. Demineralized bone matrix formulations and synthetic ceramic materials are now being used with greater frequency. These biomaterials have demonstrated their usefulness in facial plastic and reconstructive surgery with their ability to augment and replace portions of the craniofacial skeleton. The purpose of this article is to describe and discuss the allograft and alloplastic bone grafting technologies so that the reader can consider each in the context of the others and gain a better appreciation for how each fits into the universe of existing and emerging treatments for bone regeneration.

Effect of a hydroxyapatite tricalcium phosphate alloplast on osseous repair in the rat calvarium

BACKGROUND

Bony defects caused by periodontitis are often treated by regenerative therapy using autografts and/or allografts. Alloplasts, such as hydroxyapatite or ceramics, are also used as osteoconductive materials that serve as a scaffold for new bony ingrowth. The purpose of this study was to determine the effect of hydroxyapatite tricalcium phosphate (HA-TCP) on osseous repair in the rat calvarium.

METHODS

Forty-four adult male Harlan Sprague-Dawley rats were assigned to one of four treatment groups: HA-TCP macroporous disk, HA-TCP microporous disk, HA-TCP granules, and demineralized freeze-dried bone (DFDB). The materials were placed into 8-mm calvarial critical-size defects (CSD). Calvariae were harvested at 10 weeks post-surgery and evaluated histomorphometrically.

RESULTS

The DFDB group had significantly (P <0.05) more new bone formation (47%) than any other group. The HA-TCP macroporous disk group had significantly (P <0.05) more new bone formation (19.7%) than the HA-TCP microporous disk (8.5%) or HA-TCP granule (6.9%) groups.

CONCLUSIONS

The HA-TCP macroporous disk may elicit significant new bone formation due to its rigid space-maintaining scaffold and pore size for vascular ingrowth. It is well tolerated by host tissues and may be a suitable carrier for growth factors.

The Effect of Residual Calcium in Decalcified Freeze-dried Bone Allograft in a Critical-sized Defect in the Rattus norvegicus Calvarium

Demineralized freeze-dried bone allograft (DFDBA), a widely used graft material in periodontal regenerative procedures, is processed with hydrochloric acid in the attempt to expose proteins located within the bone matrixes that are capable of inducing new bone formation. However, the degree of DFDBA demineralization varies between tissue banks, which may have an effect on clinical regeneration. This study uses the critical-sized defect (CSD) model to evaluate the wound-healing response to the residual calcium of donor bone. If the percentage of residual calcium in a graft were demonstrated to significantly enhance wound healing, then periodontal patients may benefit from further standardization of human-allograft processing. Sixty adult, male, Harlan Sprague-Dawley rats (Rattus norvegicus) were randomly and equally divided into 4 test groups (ie, DFDBA at 1%, 2%, and 3% to 6% residual calcium levels and FDBA at 23% residual calcium) and a control group (no allograft). An 8-mm-diameter craniotomy was made in the rat calvarium, and polytetrafluoroethylene membranes with pore sizes of 0.50 μm were placed intracranially and ectocranially. Treatment materials were carefully placed into the CSD with a new sterilized dental amalgam carrier. Tetracycline hydrochloride was injected intraperitoneally for labeling new bone growth, and animals were euthanized 12 weeks postsurgery. As a result, histomorphometric bone fill at 12 weeks showed a statistically significant increase in the 2% DFDBA group as compared to all other groups. The authors conclude that a 2% residual calcium level in human DFDBA appears to significantly (P ≤ .05) enhance osseous wound healing in the rat calvarium.

An assay for the determination of biologically active bone morphogenetic proteins using cells transfected with an inhibitor of differentiation promoter-luciferase construct

Bone morphogenetic proteins (BMPs) control cell fate by regulating gene expression, especially inhibitor of differentiation (Id) genes. This property has been exploited to create a highly sensitive assay for quantification of active BMP. Embryonic mouse cells (C3H10T1/2) were stably transfected with an expression construct (BRE-Luc) containing a BMP-responsive element fused to the firefly luciferase reporter gene. BRE results from a multimerization of distinct sequences elements from a mouse Id1 promoter [15]. The addition of BMP-2 (0.5-100ng/ml) to the transfectants resulted in a dose-dependent increase in luciferase activity in the cell lysates. This new assay was 100-fold more sensitive than the classical alkaline phosphatase (ALP) activity assay (0.5-1 vs. 50-100ng/ml, respectively) as well as much more rapid (24h vs. 3-6 days, respectively, of BMP treatment). This new assay is specific to BMPs (BMP-2, BMP-4, and BMP7) as evidenced by its relative insensitivity to TGFbeta1, bFGF, and VEGF. Because of its BMP specificity, this rapid, sensitive, nonradioactive, and easily performed assay could be used in monitoring the biological activity of BMP and, eventually, as a cell-based screening assay to identify and evaluate molecules that modulate BMP signaling in cells.

Demineralized bone matrix graft: a scientific and clinical case study assessment

Osteoinductive demineralized bone matrix results from bone demineralization and is attributed to matrix-associated bone morphogenetic proteins. The osteoinductive potential can vary with donor. Many bioassay methods are available to screen donors, each with its own interpretation, so performance of more than one may be of value. Furthermore, little is known about the relationship between bioassay results and clinical outcomes. A study designed to meaningfully explore these issues would require assay of a large number of donors as well as clinical utilization in a large patient population. A preliminary study was undertaken to gain initial perspective. Using demineralized bone matrix derived from one 33-year-old female donor, 2 methods of bioassay and a clinical case study were performed. The levels of bone morphogenetic proteins 2, 4, and 7 in lyophilized demineralized bone matrix powder were measured (19.65 +/- 0.30 ng/g, 2.49 +/- 0.19 ng/g, and 82.03 +/- 6.89 ng/g, respectively). Also, putty (Osteostim DBM Putty), prepared from powder, was intramuscularly implanted in athymic rats and de novo bone formation quantified (6.7% +/- 3.5% new bone formation with 49% +/- 17% of the implant area associated with new bone formation). The putty, in conjunction with internal fixation, was used in the revision of a medial malleolar nonunion of an obese, 76-year-old woman. Radiographic union with excellent graft incorporation was achieved by 12 weeks postoperatively, with maintenance of an acceptable clinical result during the 14-month follow-up period. These results are interpreted in the broader context of demineralized bone grafting, in general, and an outline for further study is presented.

Extractable bone morphogenetic protein and correlation with induced new bone formation in an in vivo assay in the athymic mouse model

A correlation between extractable bone morphogenetic proteins (BMPs) in demineralized bone matrix (DBM) and osteoinduction has been suggested. Extractable BMP-4 and osteoinductivity of DBM from 40 donors were assessed using enzyme-linked immunosorbent assay (ELISA) and in vivo athymic mouse assay, respectively. Extractable BMP-4 level averaged 3.7 +/- 0.21 ng/g of DBM and correlated with osteoinductivity of the DBM in an in vivo assessment of induced newbone formation.

A review of osteoinductive testing methods and sterilization processes for demineralized bone

Allogeneic demineralized bone has been used extensively as a clinical graft material because it has osteoinductive and osteoconductive properties. Concerns over processing and terminal sterilization procedures that may reduce performance have led clinicians to call for assurances of product potency. There is extensive experience on effects of demineralized bone in animal and cell culture models with the possibility for future evidence-based standards for release of products. Evaluation of the current state of knowledge leads to the fact that we cannot conclude that performance of different lots of demineralized bone allografts in in vivo or in vitro test systems can be used as a measure of clinical performance. It may be possible to adopt an osteoinductivity standard for release-to-market, but it should be followed by clinical monitoring and further research.

Androgen metabolic response to indomethacin and the alkaline phosphatase inhibitor levamisole in fibroblasts

OBJECTIVES

The aim of this investigation is to study the effects of indomethacin (I) and the alkaline phosphatase (ALP) inhibitor levamisole (L) on androgen 5alpha-reductase expression in gingival and periosteal fibroblasts, in the context of repair in the periodontium. Chronically inflamed human gingival fibroblasts (HGF) were used to demonstrate the comparative effects of L on HGF and human oral periosteal fibroblasts (HPF).

MATERIAL AND METHODS

Monolayer cultures of six cell lines of HPF of the fifth to ninth passage were incubated in duplicate with 14C-testosterone/14C-4-androstenedione as substrates in Eagle's MEM; I was added at concentrations of 1 and 3 microg/ml in the presence or absence of the established inhibitory concentration of 30 microg/ml L and incubated for 24 h. The medium was solvent extracted for radioactive metabolites, separated by thin layer chromatography and quantified.

RESULTS

L caused 50% inhibition of 5alpha-reductase and 17beta-hydroxysteroid dehydrogenase activity in HGF. In HPF, 5alpha-reductase expression was enhanced by I with both substrates, by 65-76% (n = 6; p<0.01), inhibited by 30-50% (n = 6; p<0.01) with L and restored to control values in combination.

CONCLUSION

Yields of androgen metabolites may be linked to ALP activity, with implications on healing, during adjunctive treatment of inflammatory periodontal disease with I.

Clinical Evaluation of Calcium Sulfate in Combination With Demineralized Freeze-Dried Bone Allograft for the Treatment of Human Intraosseous Defects

BACKGROUND

Medical-grade calcium sulfate (CS) is a biocompatible, bioabsorbable, and clinically versatile ceramic for use in bone repair. This study compared the clinical efficacy of a combination of calcium sulfate dihydrate, as a binder and barrier, and demineralized freeze-dried bone allograft (DFDBA) to polytetrafluoroethylene (ePTFE) and DFDBA for the treatment of human periodontal defects.

METHODS

Two intrabony defects were compared in each of 19 patients with chronic periodontitis. After initial preparation, full-thickness mucoperiosteal flaps were elevated, osseous defects debrided, and the roots prepared (ultrasonic, hand curets, and tetracycline conditioning). Defects were randomly treated with either a combination graft of DFDBA with CS (4:1) covered by a CS barrier or with DFDBA and fitted with an ePTFE barrier. Flaps were coronally positioned to obtain primary closure. Clinical soft tissue measurements were recorded at 6 months, and all study sites were surgically reentered for evaluation.

RESULTS

The mean presurgical measurements for defects randomized to the CS and ePTFE treatments, respectively, were similar for attachment level (AL; 6.2 +/- 1.8 mm and 6.1 +/- 1.7 mm), probing depth (PD; 6.3 +/- 1.1 mm and 6.2 +/- 1.1 mm), and gingival recession (0.1 +/- 1.9 mm and 0.2 +/- 1.4 mm). Defects treated with CS or ePTFE demonstrated statistically significant (P < or = 0.0001) reductions in mean PD (2.7 +/- 1.4 mm and 3.4 +/- 1.3 mm, respectively) and gains in mean AL (1.8 +/- 1.5 mm and 1.7 +/- 1.4 mm, respectively). Recession increased by 0.8 +/- 1.4 mm at CS sites and 1.6 +/- 1.7 mm at ePTFE-treated sites (P < or = 0.05). Pretreatment mean defect depths were 4.1 +/- 1.0 mm and 3.7 +/- 1.0 mm for CS and ePTFE sites, respectively. Reentry evaluations revealed a mean defect fill of 2.7 +/- 1.5 mm and 2.5 +/- 0.9 mm for the CS and ePTFE sites, respectively, with a corresponding mean defect resolution of 80.3 +/- 18.7% and 76.7 +/- 18.5%. The CS and ePTFE sites did not differ significantly in mean defect fill or defect resolution.

CONCLUSIONS

The results of this study indicate that calcium sulfate, when used as a binder and barrier in combination with DFDBA, supports significant clinical improvement in intrabony defects, as evidenced by reductions in probing depth, gains in clinical attachment level, and defect fill and resolution. Calcium sulfate represents an important alternative to non-resorbable ePTFE barriers in combination with DFDBA for the treatment of intrabony defects.