Demineralized bone alters expression of Wnt network components during chondroinduction of post-natal fibroblasts

OBJECTIVE

The Wnt family of secreted proteins, their receptors (Fzd proteins) and antagonists (secreted Fzd-related proteins, or Sfrp) regulate chondrocyte differentiation and chrondrogenesis during embryonic development. Here, the hypothesis that the Wnt regulatory network contributes to chondrocyte differentiation of post-natal cells was tested in an in vitro model of chondroinduction by demineralized bone powder (DBP).

DESIGN

Human dermal fibroblasts (hDFs) were cultured in porous, three-dimensional (3D) collagen sponges with or without chondroinductive DBP. In some experiments, lithium chloride (LiCl), an agonist of the Wnt/beta-catenin signaling pathway, was added to the culture media. Sponges were cultured for intervals (0.5-21 days) before processing for molecular, histologic, and biochemical analyses. Expression of wnt, fzd, and sfrp genes was characterized by semi-quantitative RT-PCR. Fibroblasts' contacts with DBP were documented by histology. Accumulation of proteoglycan in extracellular matrix was evaluated by histology (metachromasia in toluidine blue-stained sections) and quantitative immunoassay (chondroitin 4-sulfate ELISA).

RESULTS

Expression of 15 wnt, fzd, and sfrp family members was detected in hDFs by RT-PCR. A subset of those genes (wnt2b, wnt5b, wnt10b, fzd6, fzd7) showed altered expression in hDFs exposed to DBP for 3 days. wnt and fzd gene expression was not altered before hDFs contacted the DBP within the collagen sponge. Human DFs cultured in plain collagen sponges and treated with LiCl accumulated significantly more metachromatic matrix than NaCl-treated controls on day 10, and showed a trend towards increased matrix chondroitin-4 sulfate content.

CONCLUSIONS

These data suggest that changes in Wnt signaling contribute to chondroinduction of post-natal fibroblasts by DBP. This is the first evidence that Wnt components, which are essential regulators of pre-natal chondrocyte differentiation, may also influence post-natal chondrocyte differentiation induced by DBP.

The effect of chicken, pigeon, and turkey demineralized bone matrix (DBM) implanted in ulnar defects fixed with the intramedullary-external skeletal fixator (IM-ESF) tie-in in pigeons (Columba livia): histological evaluations

Avian demineralized bone matrix (ADBM) powder prepared from chicken, pigeon, and turkey sources induced bone formation via endochondral and intramembranous processes, as in mammalian studies. There were no significant differences in percentage of new bone, percentage of cartilage, surface-forming osteoblast area, or osteoclast count between gaps treated with chicken, pigeon, and turkey DBM. However, there was a significantly (p<0.05) higher percentage of inflammatory area in gaps treated with chicken DBM than in gaps treated with pigeon DBM.

Mechanical stimulation promotes osteogenic differentiation of human bone marrow stromal cells on 3-D partially demineralized bone scaffolds in vitro

Bone is a dynamic tissue that is able to sense and adapt to mechanical stimuli by modulating its mass, geometry, and structure. Bone marrow stromal cells (BMSCs) are known to play an integral part in bone formation by providing an osteoprogenitor cell source capable of differentiating into mature osteoblasts in response to mechanical stresses. Characteristics of the in vivo bone environment including the three dimensional (3-D) lacunocanalicular structure and extracellular matrix composition have previously been shown to play major roles in influencing mechanotransduction processes within bone cells. To more accurately model this phenomenon in vitro, we cultured human BMSCs on 3-D, partially demineralized bone scaffolds in the presence of four-point bending loads within a novel bioreactor. The effect of mechanical loading and dexamethasone concentration on BMSC osteogenic differentiation and mineralized matrix production was studied for 8 and 16 days of culture. Mechanical stimulation after 16 days with 10 nM dexamethasone promoted osteogenic differentiation of BMSCs by significantly elevating alkaline phosphatase activity as well as alkaline phosphatase and osteopontin transcript levels over static controls. Mineralized matrix production also increased under these culture conditions. Dexamethasone concentration had a dramatic effect on the ability of mechanical stimulation to modulate these phenotypic and genotypic responses. These results provide increased insight into the role of mechanical stimulation on osteogenic differentiation of human BMSCs in vitro and may lead to improved strategies in bone tissue engineering.

The use of demineralized bone matrix for mastoid cavity obliteration

OBJECTIVE

To evaluate the use of demineralized bone matrix as a graft material for mastoid cavity obliteration in the treatment and prevention of problematic mastoid cavities.

STUDY DESIGN

The study is a retrospective review of patients identified using a computerized otology database.

SETTING

Tertiary care referral center.

PATIENTS

Patients were included in this study if they underwent mastoid obliteration using demineralized bone matrix.

INTERVENTION

Mastoid obliteration was performed for revision of a problematic mastoid cavity (n = 8) or primarily after canal wall down mastoidectomy for recurrent cholesteatoma (n = 3).

MAIN OUTCOME MEASURES

Data were collected to evaluate the ability to achieve a dry ear canal. Postoperative healing time and hearing results were also assessed.

RESULTS

A dry ear canal was achieved in all patients with a follow-up of 6 to 20 months (average, 14.5 mo). Eight patients (73%) had a well-healed, dry ear canal by their first postoperative visit (9 wk). One patient required 12.5 weeks to heal. Two patients (18%) had more prolonged granulation at the ear canal incision, which resolved in 17 and 28 weeks, respectively. The average preoperative pure-tone average air-bone gap was 47 +/- 14.9 dB (mean +/- SD), compared with postoperative values of 27.6 +/- 12.8 dB (p = 0.0033; paired t test). This represents an average pure-tone average air-bone gap closure of 20 dB.

CONCLUSION

The use of demineralized bone matrix as a graft extender in mastoid obliteration allowed creation of a dry, smooth-contoured canal in all patients studied. A significant improvement in hearing was also obtained. Demineralized bone matrix is an acceptable graft alternative for mastoid obliteration.

Evidence for a Serum Factor That Initiates the Re-calcification of Demineralized Bone

The present studies show for the first time that demineralized bone re-calcifies rapidly when incubated at 37 degrees C in rat serum: re-calcification can be demonstrated by Alizarin Red and von Kossa stains, by depletion of serum calcium, and by uptake of calcium and phosphate by bone matrix. Re-calcification is specific for the type I collagen matrix structures that were calcified in the original bone, with no evidence for calcification in periosteum or cartilage. Re-calcification ceases when the amount of calcium and phosphate introduced into the matrix is comparable to that present in the original bone prior to demineralization, and the re-calcified bone is palpably hard. Re-calcified bone mineral is comparable to the original bone mineral in calcium to phosphate ratio and in Fourier transform infrared and x-ray diffraction spectra. The serum activity responsible for re-calcification is sufficiently potent that the addition of only 1.5% serum to Dulbecco's modified Eagle's medium causes bone re-calcification. This putative serum calcification factor has an apparent molecular mass of 55-150 kDa and is inactivated by trypsin or chymotrypsin. The serum calcification factor must act on bone for 12 h before re-calcification can be detected by Alizarin Red or von Kossa staining and before the subsequent growth of calcification will occur in the absence of serum. The speed, matrix-type specificity, and extent of the serum-induced re-calcification of demineralized bone suggest that the serum calcification factor identified in these studies may participate in the normal calcification of bone.

New Chondrocyte Genes Discovered by Representational Difference Analysis of Chondroinduced Human Fibroblasts

This report includes a review of the potential for gene expression analyses to provide new information for solving problems in skeletal repair and regeneration. It focuses on two approaches: high-throughput gene array methods and representational difference analysis (RDA). The principles underlying these methods are presented with experimental tutorials and some applications. Second, this report includes a review of results from applying both approaches to an in vitro model of postnatal chondroinduction by demineralized bone powder (DBP). Human dermal fibroblasts (hDFs) cultured with DBP acquire a chondroblast phenotype and express cartilage-specific matrix proteins after 7 days. We used cDNA macroarrays and RDA to identify the genes that were altered prior to expression of the chondroblast phenotype, i.e., after only 3 days' culture with DBP. Using a strategy of data management and reduction based upon biological functions, we reported several functional families of genes (cytoskeletal elements, protein synthesis/trafficking, and matrix molecules and their modifiers) that are upregulated during chondroinduction of hDFs. Together with histological and biochemical evidence of the chondroblast phenotype, the gene expression patterns indicate that there are specific stages of induced chondrocyte differentiation in this experimental system. Third, this report includes a new study, in which DBP-regulated genes were used as a data base to derive new information on the cell biology of chondrocytes. The objective was to determine whether a set of genes expressed during induction of chondrocyte differentiation is also expressed by mature articular chondrocytes. Our search of the literature for 59 of the DBP-regulated genes disclosed that expression of 20 of them (33%) had been documented in mature cartilage or chondrocytes. Of the 39 genes not previously documented in cartilage, 11 were tested by RT-PCR and all were found to be expressed in freshly isolated adult human chondrocytes. This review and these new data show how the strategy of high-throughput methods and functional data reduction can expand our knowledge of chondrocyte cell biology.

Measurement of bone morphogenetic proteins and other growth factors in demineralized bone matrix

Osteoinductivity of demineralized bone matrix has been attributed to bone morphogenetic proteins (BMP). Other growth factors, including insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta1 (TGF-beta1), have also been detected in demineralized bone matrix. Success of bone graft substitutes containing demineralized bone matrix has been assumed to be closely associated with osteoinductivity of the demineralized bone matrix. Because of differences in bone characteristics between donors and tissue banks, confirmation and measurement of osteoinductivity may play a crucial role in predicting the success of the bone graft substitute. In the current studies, BMP-2, BMP-4, TGF-beta1, and IGF-1 were measured in demineralized bone matrix. A strong association was noted between BMP-2 and TGF-beta1 levels. A strong association was also found between BMP-2 and new bone formation in an ectopic nude rat model.

Alkali-urea extraction of demineralized bone matrix removes noggin, an inhibitor of bone morphogenetic proteins

Demineralized bone matrix (DBM) and native bone morphogenetic protein (nBMP) are complex mixtures of non-collagenous bone proteins. These mixtures contain many of the BMPs that are available as recombinant molecules. Information regarding the presence in these materials of molecules that may affect the availability and activity of the BMPs is very limited. We have devised a simple chemical extraction of DBM using alkali-urea that produces a water soluble extractate that inhibits the osteogenic activity of DBM. We have demonstrated the presence of noggin, an extracellular BMP ligand antagonist, in this material. We conclude that differential chemical extraction may be a useful means of removing inhibitory molecules from DBM and nBMP.

Quantitative and sensitive in vitro assay for osteoinductive activity of demineralized bone matrix

A sensitive, rapid, reliable and quantitative method to check the bone forming potential of demineralized bone matrix (DBM) has been developed. The osteoinductivity of the bone morphogenetic proteins (BMPs), present in DBM, can be measured in vitro using a pluripotent myoblast C2C12 cell line. Alkaline phosphatase activity induced by co-incubation of DBM with C2C12 cells was dose-responsive and corresponds to the amount of active BMPs in DBM. Bone forming potential was simultaneously tested in vivo by implanting DBM intra-muscularly in nude rats. ALP activity induced in C2C12 cells, correlated with bone formation in vivo (r=0.88), determined by alkaline phosphatase activity, mineralization density and histomorphology of the DBM explants. Results from DBM batches, originating from five established Bone Banks, showed good consistency between in vitro and in vivo assays. However, DBM activity varied widely from bank to bank as well as from batch to batch within the same bank.

The effect of bone graft extenders to enhance the performance of iliac crest bone grafts in instrumented lumbar spine fusion

Allograft bone extenders are commonly used in spinal surgery to increase the available graft volume, thereby promoting and achieving a solid fusion mass. We report a single surgeon's use and early results of autologous bone graft and allograft demineralized bone matrix in 65 patients undergoing lumbar spinal fusion. Of the patients included in this study, 59 (91%) patients underwent surgical intervention for lumbar spinal stenosis, three (5%) patients had lumbar spondylolisthesis, two (3%) patients had stenosis, and one (1%) patient had bilateral spondylolysis. Forty-three (64%) women and 22 (36%) men were included in the study. The average patient age was 56 years (20-85 years, SD= +/- 16). Independent radiographic evaluation was performed. Each subsequent radiographic follow-up revealed increased improvement in average Lenke score and was statistically significant between the early (1 month) and recent (12 month) follow-ups. There were statistically significant changes in Lenke score between 1 month and 3 months follow-up (P<.01), between 3 months and 6 months follow-up (P<.001), and between 6 months and 12 months follow-up (P<.01). The gradual and constant increment of improvement in radiographic measurements in this preliminary series may indicate a positive effect of the use of bone graft extenders that may decrease the required amount of autologous bone graft. Bone graft extenders also may minimize the risks and complications associated with the harvesting procedure.

In vitro evaluation of the mitogenic effect of platelet-derived growth factor-BB on human periodontal ligament cells cultured with various bone allografts

BACKGROUND

Several studies have documented the role of growth factors in periodontal regeneration. It has been shown that platelet-derived growth factor (PDGF) is a potent stimulator of human periodontal ligament (PDL) cells. A variety of bone graft materials are used to treat osseous defects caused by periodontal disease. We evaluated the mitogenic effect of PDGF on human PDL cells cultured with different allografts to determine which of the allografts with or without PDGF promoted periodontal regeneration.

METHODS

Two human demineralized freeze-dried allografts of cortical (DFDBA) and cancellous (DFBA) bone and a non-demineralized freeze-dried allograft (FBA) from cancellous bone were used alone or supplemented with PDGF-BB. Human PDL cultures were derived from the mid-root of 2 maxillary premolars extracted for orthodontic reasons. Cells were grown separately in 24-well dishes with or without 20 mg of each bone allograft. On day 2 of quiescence, new medium was added with 10 ng/ml of PDGF-BB. DNA synthesis was estimated by measuring [3H] thymidine incorporation to determine the effects of the test agents on cell proliferation. Cells were processed and subjected to scintillation counting after 48 hours of incubation. Counts per minute (cpm/well) were determined for each sample.

RESULTS

There was no statistically significant difference (P<0.05) on PDL cell proliferation when the allografts were used alone. PDL cells exhibited significantly greater proliferative responses to the 2 demineralized bone allografts, DFDBA and DFBA, when combined with PDGF-BB. A statistically significant difference on DNA synthesis was noticed when PDGF-BB was added to PDL cells cultured with FBA. PDL cells displayed no significant increase in mitogenic activity when cultured with PDGF-BB alone.

CONCLUSIONS

The findings of this study demonstrate the beneficial role of DFDBA, DFBA, and FBA as synergic agents with PDGF-BB to periodontal regeneration. The significant ability of the 2 decalcified bone allografts, DFDBA and DFBA, combined with PDGF to stimulate PDL cell proliferation might be a useful adjunct in the treatment of periodontal defects.

Efficacy of contained metaphyseal and periarticular defects treated with two different demineralized bone matrix allografts

The efficacies of two different allografts, Grafton (demineralized bone matrix [DBM] in a glycerol carrier) and Orthoblast (DBM in a reverse thermal poloxamer carrier) were examined from cases involving periarticular fractures. Demographic, perioperative, and outcome data for patients with periarticular fractures who underwent a prospectively designed protocol for bone grafting were compiled, with 15 cases using Orthoblast and 13 using Grafton. A successful graft was defined as healing on the first graft attempt without complications. Healing was determined by radiographic studies and clinical evaluation. The successful graft rates of Orthoblast and Grafton were 15/15 and 9/13, respectively.

In vitro release of vancomycin from vancomycin-loaded blood coated demineralised bone

In vitro and in vivo studies have demonstrated the possibility that cancellous bone could be used as a carrier of antibiotics for local delivery. However, the release of antibiotics from the loaded cancellous bone is too rapid and uncertain. We hypothesised that demineralisation of cancellous bone would increase the amount of antibiotic adsorbed, and coating of the freeze-dried antibiotic-impregnated cancellous bone with bio-compatible material would prolong antibiotic release. Bovine cancellous bone blocks of equal size were demineralised using a 0.5 N HCl solution and loaded with vancomycin solution under vacuum. The loaded bone blocks were then freeze-dried. To obtain a bio-compatible coating, the vancomycin-impregnated bone blocks were soaked in fresh human venous blood for 3 h. The release of impregnated antibiotic from the bone blocks was evaluated in phosphate-buffered saline and foetal bovine serum. It was found that significantly larger amounts of vancomycin were adsorbed into the demineralised bone blocks than into the un-demineralised blocks. The blood coating was found to increase the duration of vancomycin release from the blocks. With demineralisation and blood coating, the blocks eluted vancomycin higher than therapeutic concentration for a 5-week period.

[An experimental study of demineralized bone matrix to repair bone defects as a scaffold of tissue engineering]

OBJECTIVE

To evaluate application of the sponge of demineralized bone matrix (SDBM) in tissue engineering of bone.

METHODS

SDBM was prepared from long bone of rabbits. Bone marrow cells were flushed from the bone shaft of femurs of a two-month-old New Zealand white rabbit. After the cells were cultured for 9 days, the flasks were added into dexamethasone (10(-8) mol/L), beta-glycerophosphate sodium (10 mmol/L) and L-ascorbic acid (50 micrograms/ml). After 5 weeks, the cultured cells were collected and marked by 5-Bromo-2'-dexyouridine (BrdU). The grand sum of cells seeded on a piece of SDBM was about (4-6) x 10(6). The composites of cells and SDBM (tissue engineered chip, TEC) were implanted into muscles and bone defects of radius in rabbits. A standard procedure was applied to make a 10 mm long defect bilaterally in the radius of nine skeletally mature male New Zealand white rabbits. All of the 18 defects were randomly divided into three groups: group I, six defects were grafted by TEC; group II, six defects were grafted with SDBM alone; group III, six defects were empty.

RESULTS

The results of radiographic and histological evaluation showed that all of the defects were repaired in group I and group II at 6 weeks, none of the defects was repaired in group III. The results of BrdU staining showed that the staining was positive in group I, but negative in group II. Biomechanical test showed that the compressive ultimate strength (CUS) of new bone in TEC implanted group was comparable with normal radius (P = 0.623) and in SDBM implanted group was significant lower than normal radius (P = 0.038).

CONCLUSIONS

The TEC can form cartilage and bone tissue in muscles and repair segmental bone defects. SDBM is a kind of effective natural scaffold in tissue engineering of bone.

Dimensional changes in acid-demineralized dentin matrices following the use of HEMA-water versus HEMA-alcohol primers

Although dried acid-etched dentin can be reexpanded by hydroxyethyl methacrylate (HEMA)/water primers, the primed dentin collapses when the water is evaporated. Experimental HEMA/alcohol primers should stiffen the matrix and permit less shrinkage when the solvent is evaporated. The purpose of this study was to test the hypotheses that matrix shrinkage induced by solvent evaporation from HEMA primers is inversely related to solvent-induced matrix stiffness. Dentine discs were prepared from midcoronal dentine of unerupted human third molars. After demineralization in 37% phosphoric acid, the specimens were placed in the well of a linear variable differential transformer instrument, which measures changes in the matrix height and stiffness by load displacement after the application of weights. This was done in their hydrated state after water had been applied, after drying with dry nitrogen gas, and after the application of 35 vol % HEMA-water, HEMA-methanol, HEMA-ethanol, or HEMA-propanol primers. The degree of reexpansion after the application of the primers to the dentine in the dried state was found to be highest using the HEMA-water primer, followed by HEMA-methanol and HEMA-ethanol, with the HEMA-propanol primer producing no expansion. However, when the solvents were evaporated the HEMA-water-treated specimens shrank the most, the HEMA-ethanol-treated specimens shrank an intermediate amount, and the HEMA-methanol-treated specimens shrank the least. The net result of expansion minus shrinkage produced by evaporation determines how much HEMA remains in the hybrid layer just prior to polymerization.

The effect of demineralized intramembranous bone matrix and basic fibroblast growth factor on the healing of allogeneic intramembranous bone grafts in the rabbit

The aim here was to explore a new graft material that excludes the need to harvest autogenous bone from patients. Forty-two critical-size (10 x 15 mm) defects were created in rabbit mandibles bilaterally. Five groups of six defects each were grafted with autogenous endochondral (EC) bone, autogenous intramembranous (IM) bone, fresh-frozen allogeneic IM bone only, fresh-frozen allogeneic IM bone and demineralized bone matrix powder prepared from intramembranous bone (DBM(IM)) only, and fresh-frozen allogeneic IM bone and basic fibroblast growth factor (bFGF) mixed with DBM(IM) powder. The remaining defects were used as controls. Three weeks after surgery, the defects were retrieved for histological analysis. The amount of new bone formation was quantified by image analysis. No bone formed across the defect in the controls; 224% more new bone formed in defects grafted with composite allogeneic IM bone/DBM(IM) than in those grafted with allogeneic IM bone alone (p < 0.001); 550% more new bone was formed in defects grafted with composite allogeneic IM bone/DBM(IM)/bFGF than in those grafted with allogeneic IM bone alone (p < 0.001). The amount of new bone in the group receiving composite allogeneic IM bone/bFGF/DBM(IM) was more than that in autogenous EC bone group, and very close to that in autogenous IM group. The results show that a composite of fresh-frozen allogeneic IM bone and bFGF in DBM(IM) powder is a good graft material that warrants further clinical investigation.

Characterization of bone defect repair in young and aged rat femur induced by xenogenic demineralized bone matrix

BACKGROUND

The osteoinductive effect of some biomaterials could be affected by those systemic conditions typical of old age. The aim of the present paper was to assess the effects of age on the healing of bone defects treated with demineralized bone matrix (DBM).

METHODS

The study was conducted in young (3 month old) and aged (18 month old) rats to assess the efficacy of DBM in the treatment of osseous defects in bone with limited repair capacities. A standard bone defect was created in the distal femoral condyles of male Wistar rats: the left condyle was filled with rabbit DBM granules, while the right condyle was left empty (control). Histological and microhardness analyses were performed at 30 and 45 days after implant surgery.

RESULTS

After implantation of xenogenic DBM, bone healing areas of the aged and young groups showed a significant increase in the formation of newly mineralized bone relative to controls. Measurements of trabecular thickness on day 45 revealed no differences between newly formed and preexisting bone in the young group, while control values were lower. Microhardness measurements demonstrated that newly mineralized bone, either induced by DBM or not, and preexisting bone were comparable in terms of trabecular hardness after 45 days.

CONCLUSIONS

In conclusion, xenogenic DBM seems to be effective in bone defect healing, since it increases mineralized tissue volume. In both DBM-filled and empty sites, age seems to have a detrimental effect on the volume of new bone formation but no influence on bone maturation.

Identification of the molecular chaperone alpha B-crystallin in demineralized bone powder and osteoblast-like cells

Bone is subjected to a variety of physiological, as well as cell-deforming biomechanical stresses, including hydrostatic compression and fluid flow. However, little is known about the molecular mechanisms that protect bone cells from mechanical, ischemic, or oxidative damage. Crystallins are 20 kD heat shock proteins that function as molecular chaperones. We tested the hypothesis that alpha B-crystallin (alphaB-crystallin), the most widely expressed vertebrate crystallin, is present in bone and osteoblast-like cells. Noncollagenous proteins (NCPs) were extracted from human demineralized bone matrix with 4 M guanidine HCI containing 0.5 M CaCl2 and protease inhibitors, defatted, dialyzed against 0.2% (v/v) Triton X-100 in 100 mM Tris-HCI (pH 7.2) and water, centrifuged, and lyophilized. The NCPs were separated by 2D IEF/SDS-PAGE. The two most abundant 20 kD spots, with apparent pIs of 7.85 and 7.42 in urea gels, were excised, subjected to matrix-assisted laser desorption ionization/time-of-flight mass spectrometry, and identified as alphaB-crystallins. Indirect immunofluorescence localized alphaB-crystallin to the interphase nucleus, cytoskeleton and cytoplasm of proliferating MC3T3-E1 mouse osteoblast-like cells, as well as the cytoskeleton and cytoplasm of confluent cells. In conclusion, alphaB-crystallin is present in bone and osteoblast-like cells. We hypothesize that alphaB-crystallin may play a role in protecting the osteoblast cytoskeleton from mechanical stress and may be important in modulating nuclear or cellular functions, such as transcription or apoptosis, as observed in other tissues.

Bone induction in clinical orthodontics: a review

The major limitations of autogenous grafting are inadequate supply and surgical morbidity, including donor site pain, paresthesia, and infection. Graft resorption can also pose a severe problem. Bone induction is therefore needed to assist in fracture healing and to fill osseous defects. This article reviewed the current development of bone induction in relation to clinical orthodontics.

A comparative study of osseointegration of Avana implants in a demineralized freeze-dried bone alone or with platelet-rich plasma

PURPOSE

The purpose of this study was to assess the efficacy of demineralized bone powder (DBP) alone or combined in a mixture with platelet-rich plasma (PRP) used to enhance osseointegration of dental implants in a dog model.

MATERIALS AND METHODS

Tissue integration was assessed using standard histomorphometric methods at 6 and 12 weeks after surgery. A total of 30 Avana dental implants (SooMin Synthesis Dental Materials Co, Busan, Korea) were inserted in the animals. They were self-tapping screw implants, 10 mm in length and 4 mm in diameter, made of commercially pure titanium. A titanium implant was then placed centrally in each defect. In each dog, the defects were treated with 1 of the following 3 treatment modalities:1) no treatment (control), 2) grafting with DBP, or 3) grafting with DBP and PRP.

RESULTS

Histologic analysis showed that all of the bone defects surrounding the implants that were treated with DBP, with and without PRP, were filled with new bone. The defects that were not treated (control) showed new bone formation only in the inferior threaded portion of the implants. Histomorphometric results revealed a higher percentage of bone contact with DBP and PRP compared with control and DBP.

CONCLUSION

These results suggested that bone defects around titanium implants can be treated successfully with DBP and that PRP may improve bone formation.

Cranioplasty using allogeneic perforated demineralized bone matrix with autogenous bone paste

The efficacy of allogeneic perforated demineralized bone matrix with autogenous bone paste in the treatment of full-thickness cranial defects was evaluated in 10 consecutive patients between June 1998 and December 1998. The skull defects resulted from trauma in 9 patients and removal of a cranial tumor in 1 patient. The size of the skull defects ranged from 8 x 6 cm to 11 x 12.5 cm. Follow-up averaged 33 months for all patients. Postimplantation evaluations included serial photographs, repeated physical examination, and three-dimensional computed tomography for all patients. Visual inspection of the implanted biomaterial 6 months later was possible in 1 patient. The contour of the reconstructed skull was acceptable aesthetically without any secondary depression noted during the follow-up period. Three-dimensional computed tomographic scans taken 2 years after implantation indicated that the allogeneic perforated demineralized bone matrix provided a matrix for new bone formation with remarkable osteoinductive potential for new bone formation. The autogenous bone paste was able to caulk the demineralized bone matrix and fill the contour irregularities and gaps of the reconstructed cranium. The results from this clinical study indicated that allogeneic perforated demineralized bone matrix with autogenous bone paste is a promising alternative to an autogenous bone graft and or alloplastic material for cranioplasty.

Enhanced guided bone regeneration with a resorbable chamber containing demineralized bone matrix

BACKGROUND

The effectiveness of a nonporous poly-DL-lactide tubular chamber in guiding bone regeneration through a long bone defect had already been assessed in an experimental model using the rabbit radius. The injection of bone marrow stem cells into the chamber had proven to enhance bone regeneration.

METHODS

The present study reports on the development of the above research project in a subsequent stage. Demineralized bone matrix (DBM) obtained by milling New Zealand rabbit femoral and tibial diaphyses was placed into a tubular chamber. A 10-mm defect was bilaterally created in the radii of 10 rabbits. On the left side (chamber side) the defect was treated by means of a poly-DL-lactide chamber filled with DBM, whereas DBM alone was used on the right side (control).

RESULTS

Controls were performed at 3 and 6 months by radiographs and histomorphometry and demonstrated better bone growth on the chamber side versus the control side. A comparison with the results previously obtained by stem cell injection into the chamber revealed significant acceleration of bone regrowth in the first 3 months because of the addition of DBM to the chamber. However, no significant difference was found between the two sides after 6 months.

CONCLUSION

These results have confirmed the effectiveness of the chamber as a container for the factors promoting bone regeneration, probably because the osteogenetic activity is maintained in situ.

Histochemical demonstration of gamma-glutamyl transpeptidase activity in normal rat cartilage and bone

The feasibility of histochemical detection of GGT activity in decalcified bone tissue is proved and the activity distribution pattern of GGT in normal rat cartilage and bone is described. The results suggest the association, in this model, between GGT activity and differentiation mechanisms rather than proliferative processes. The fact that GGT activity in adult tissues which are normally GGT negative has been linked to premalignant transformation confers significance to the study of GGT activity in normal tissues. The results contribute to the knowledge of the biological mechanisms in which GGT activity is involved and to the understanding of the behaviour of tissues which can be used as controls in carcinogenesis models.

Biostructural augmentation for the treatment of osteonecrosis: rationale, technique, and case example

Avascular necrosis of the hip is a common disease that usually affects a young and active patient population. As the disease progresses, the undermined structural integrity of the subchondral bone leads to articular collapse and subsequent osteoarthrosis. The ideal treatment is one that hinders or arrests the progression of the disease, averting articular collapse and joint replacement surgery. A surgical strategy is described that attempts to address the multiple factors involved in the progression of the disease. This is accomplished through a modified core decompression procedure combined with the insertion of two interference screws into the subchondral plate to provide structural support and the use of osteoinductive material (i.e., demineralized bone matrix) in an effort to accelerate the bone healing process.

Anterior lumbar interbody fusion with titanium mesh cages, coralline hydroxyapatite, and demineralized bone matrix as part of a circumferential fusion

BACKGROUND CONTEXT

Anterior lumbar interbody fusion (ALIF) has become one of the primary choices for eliminating motion between vertebral segments in patients with severe discogenic pain and other lumbar pathologies. Autograft is the gold standard for spinal fusion. However, multiple authors have reported complication and morbidity rates associated with iliac crest harvesting to be as high as 25%. Drawbacks to the use of allograft in the anterior column include slower incorporation rates, the possibility for disease transmission, increasing cost resulting from stringent processing and unavailability on a worldwide basis resulting from religious and economic concerns.

PURPOSE

To determine the clinical and arthrodesis efficacy of coralline hydroxyapatite as an osteoconductive bone graft substitute in the anterior lumbar spine using a titanium mesh cage.

STUDY DESIGN

A series of 50 patients returning for long-term prospective follow-up, implanted with titanium mesh cages filled with coralline hydroxyapatite and demineralized bone matrix for ALIF as part of a circumferential fusion.

PATIENT SAMPLE

Long-term clinical and radiographic follow-up were examined for the first 50 patients undergoing this technique by one surgeon.

OUTCOME MEASURES

Pain was measured with a visual analog scale and function was measured with the Oswestry Disability Index.

METHODS

All 50 patients underwent successful ALIF with titanium mesh cages, coralline hydroxyapatite and demineralized bone matrix, as well as an autologous posterolateral fusion with rigid posterior instrumentation. Patients filled out follow-up questionnaires and appropriate radiographs were taken.

RESULTS

A solid fusion rate of 96% was achieved. Mean pain decrease was 60% overall. A total of 70% of all patients either returned to work or to full home activities at a mean of 8 months after surgery. Ninety percent felt the surgery was successful.

CONCLUSIONS

The combination of titanium mesh cages, coralline hydroxyapatite and demineralized bone matrix is effective for anterior interbody fusion of the lumbar spine when used as part of a rigidly instrumented circumferential fusion.

[Experimental study of periosteal osteoblasts coculture with freeze-dried demineralized bone matrix]

OBJECTIVE

To investigate the feasibility of freeze-dried demineralized bone matrix (FDBM) as scaffold material in bone tissue engineering.

METHODS

Osteoblasts which were isolated from cranial periosteum of New Zealand rabbits were cultured as the seeding cells, then the cells were cocultured with heterogenous FDBM in vitro. The cell-material complex was observed under phase microscope, light microscope and electronic scanning microscope in order to evaluate the interaction between cells and FDBM.

RESULTS

Eight hours after coculture, the osteoblasts adhered to FDBM scaffolds. Seven days later, the osteoblasts differentiated and proliferated in FDBM network. Extracellular matrix was secreted and calcium nodes were formed among osteoblasts.

CONCLUSION

FDBM is a good scaffold material for the bone tissue engineering.

Prefabrication of bone by use of a vascularized periosteal flap and bone morphogenetic protein

The purpose of this pilot study was to prefabricate a vascularized bone graft by using a vascularized periosteal flap containing osteoprogenitor cells, a structural matrix, and recombinant human bone morphogenetic protein-2 (rhBMP-2). In a rat model, a periosteal flap vascularized by the saphenous artery and vein was dissected off the medial surface of the tibia. This flap consisted of three layers-periosteum, muscle, and fascia-and was tubed on itself to form a watertight chamber that was then transferred on its vascular pedicle to the groin. A total of 78 vascularized periosteal chambers were constructed in 39 animals and divided into 10 groups. In group 1, the periosteal chamber was left empty. Groups 2, 3, and 4 consisted of the periosteal flap and rhBMP-2, but in group 3, the proximal vascular pedicle was ligated, and in group 4, the flap was harvested without the periosteal layer and turned inside out. Groups 5 through 10 consisted of the vascularized periosteal flap containing several different structural matrices (calcium alginate spheres, polylactic acid, or demineralized bone matrix) with or without rhBMP-2. Animals were killed at 2, 4, or 8 weeks in each group. The presence and density of any new bone formation was evaluated both radiologically and histologically. Significant bone formation was seen only in those periosteal flaps containing rhBMP-2 and either the calcium alginate or polylactic acid matrix. New bone formation increased both radiologically and histologically from 2 weeks to 8 weeks only in the periosteal flaps containing the polylactic acid matrix and rhBMP-2. This preliminary study therefore suggests that four factors-blood supply, osteoprogenitor cells in the periosteal layer, a biodegradable matrix, and rhBMP-2-are required for optimal prefabrication of a vascularized bone graft.

Tissue response and osteoinduction of human bone grafts in vivo

Freeze-dried human bone allograft is used clinically as an adjunct to autologous bone graft. When freeze-dried human bone allograft is demineralized, the allograft is osteoinductive, since it causes bone to form heterotopically. Both types of allograft are also used alone, such as in spinal fusions, critical size defects, and periodontal therapy. The purpose of this study was to determine the effect of demineralization on the osteoinductive potential of human bone grafts obtained from two different groups of patients. One group consisted of six patients younger than 42 years of age, while the other group consisted of six patients who were older than 70 years of age. The harvested material was lyophilized and divided into two portions, one of which was used directly while the other was demineralized. Osteoinductive ability was established using an in vivo assay for heterotopic bone formation. Activity in these bone grafts was compared with a batch of commercially prepared demineralized, freeze-dried human bone grafts that had been previously shown to be active and another batch that had been shown to display low ('inactive') osteoinductive ability. A bone induction score was determined for each group of grafts based on the number and size of any ossicles formed. In addition, the area of new bone formation and area of residual particles were determined histomorphometrically. Tissue response to the bone grafts varied with donor age and whether the samples had been demineralized or not. Only demineralized, freeze-dried bone graft from patients younger than 42 years of age was osteoinductive; all other batches displayed little or no osteoinductive activity. In the demineralized, freeze-dried bone from donors younger than 42 years of age, the bone induction score and new bone area were significantly higher than in the other batches of bone graft, and the area of residual particles was reduced. Both demineralized and nondemineralized bone graft from patients older than 70 years of age were encapsulated in dense, fibrous connective tissue. These results may help explain the observed differences in clinical outcome when demineralized, freeze-dried bone graft or nondemineralized, freeze-dried bone graft from different donors is used in bone regeneration applications.

A comparison of porous and non-porous teflon membranes plus demineralized freeze-dried bone allograft in the treatment of class II buccal/lingual furcation defects: a clinical reentry study

BACKGROUND

The aim of this 9-month reentry study was to compare the regenerative healing using porous (P) and non-porous (NP) teflon barrier membranes plus demineralized freeze dried bone allografts (DFDBA) in Class II buccal/lingual furcation defects.

METHODS

Twenty-four patients, 13 males and 11 females, ages 38 to 75 (mean 54 +/- 10), were included in this study. Each patient had adult periodontitis and one Class II furcation defect measuring > or = 3 mm open horizontal probing depth. Twelve patients were randomly selected to receive the NP treatment and 12 received the P membrane. All defects received a DFDBA graft. Measurements were performed by a masked examiner.

RESULTS

No statistically significant differences (P>0.05) were found between NP and P groups at any time with respect to any open or closed measure. Improvement in mean open horizontal probing depth was significant for both the NP (2.33 +/- 0.78 mm) and P (2.75 +/- 0.75 mm) groups. Mean clinical attachment level gains at 9 months were significant for both NP (1.50 +/- 1.62 mm) and P (2.50 +/- 2.11 mm) groups. Seventeen of 24 defects had an intrabony component and > or = 50% fill was obtained in 100% of these defects.

CONCLUSIONS

The results of this 9-month reentry study comparing the use of porous and non-porous barrier membranes with a DFDBA graft indicate that there were no statistically significant differences between groups. Both groups showed a statistically significant improvement following the treatment of Class II furcation defects in humans.

Demineralized bone matrix, bone morphogenetic proteins, and animal models of spine fusion: an overview

Preclinical investigations on the use of bone morphogenetic proteins (BMP) in the spine have yielded promising results. This has led to the preliminary introduction of these growth factors in controlled clinical trials. Initial data made available suggest that these differentiating factors will play a major role in the treatment of spinal disorders in the future. This article reviews key preclinical studies and their results that formed the basis for introduction into clinical trials. Non-primate and non-human primate models of spine fusion with BMP are reviewed objectively, and important issues regarding carrier, dose, and site of implantation are discussed. Finally, exciting new gene therapy research is discussed, with comments made on its applicability for the future.

Clinical applications of bone graft substitutes in spine surgery: consideration of mineralized and demineralized preparations and growth factor supplementation

Bone graft substitutes may be broadly classified as mineralized and demineralized preparations. This article reviews the basic science and biology underlying each preparation. A review of the clinical and experimental applications of each preparation follows. The text concludes with a review of growth factors as biological supplements.

Tissue reactions to particles of bone-substitute materials in intraosseous and heterotopic sites in rats: discrimination of osteoinduction, osteocompatibility, and inflammation

Two rat models were used to characterize tissue-specific reactions to particles of bone-substitute materials: one for osteocompatibility in a healing tibial wound and the other in a heterotopic, subcutaneous site. Small, unicortical tibial wounds in rats healed spontaneously, beginning with the rapid proliferation of intramedullary woven bone. That temporary bone was resorbed by osteoclasts and finally, the cortical wound was healed with lamellar bone and the medullary space was repopulated with marrow. When various particulate materials were implanted into fresh wounds, three types of reactions were observed. (1) Demineralized bone powder (DBP) and non-resorbable calcium phosphate (nrCP) were incorporated into the reactive medullary and cortical bone. (2) Polymethylmetlhacrylate (PMMA) particles were surrounded with a fibrous layer, but did not impair bone healing. (3) Polyethylene (PE) shards and resorbable calcium phosphates (rCPs) were inflammatory and inhibited osseous repair. Subcutaneous sites showed osteoinductive, fibrotic, or inflammatory responses to these materials. Only DBP induced endochondral osteogenesis subcutaneously. The nrCP evoked a fibrous reaction. In contrast, rCPs, PMMA, and PE shards generated inflammatory reactions with each particle being surrounded by fibrous tissue and large multinucleated giant cells. In conclusion, only DBP showed osteoinductive as well as osteocompatible properties. The nrCP was osteocompatible. The rCPs stimulated various degrees of inflammatory responses. PMMA was osteocompatible and did not interfere with the bone healing process. PE was not osteocompatible and generated foreign body reactions in both sites. Use of the two sites distinguishes osteoinductive, osteocompatible, and inflammatory properties of particles of bone-substitute materials.

The relationship between revascularisation and osteogenesis in fresh or demineralised bone grafts

Bone formation generally depends on adequate blood flow. Failure of bone grafts has been attributed to delayed revascularisation of the graft. We compared the relationship between revascularisation and osteogenesis, evaluated as entrapment of (141)Ce-labelled microspheres and uptake of (85)Sr, respectively, in fresh or demineralised syngeneic bone grafts 3 weeks after heterotopic implantation in rats. Whereas a moderately high linear correlation between (85)Sr and (141)Ce radioactivity was found both in the (intact) host iliac bone (r = 0.75, p = 0.0001) and implanted fresh syngeneic grafts (r = 0.50, p = 0.001), no correlation could be demonstrated in demineralised grafts (r = 0.09, p = 0.6). The results may indicate differences in the mechanisms of vascularisation and osteogenesis in the grafts used fresh or after demineralization but are, at present, difficult to fully explain.

Effect of gas-plasma sterilization on the osteoinductive capacity of demineralized bone matrix

The current study evaluated the effect of low-temperature hydrogen peroxide gas plasma sterilization on the osteoinductive capability of human demineralized bone matrix using a rat model. Twelve athymic rats received three separate implants consisting of steam-sterilized demineralized bone matrix (negative control), sterile-harvest demineralized bone matrix (positive control), and gas-plasma-sterilized demineralized bone matrix. A demineralized bone matrix pellet from each sterilization group was placed individually into one of three separate soft tissue pockets created in the epaxial musculature of each rat. All 12 rats were euthanized 9 weeks after implantation. Each implantation site was removed along with 0.5-cm normal tissue around the implant. Histologic examination was done on each implant site to determine the presence or absence of new bone, cartilage, or bone marrow elements. All 12 sterile harvest demineralized bone matrix sites histologically contained new bone elements, whereas none of the negative control or gas plasma sterilized demineralized bone matrix sites contained any of these same elements. The results of this study indicate that demineralized bone matrix sterilized with low-temperature, gas-plasma sterilization loses its osteoinductive capacity in a manner similar to that of steam-sterilized demineralized bone matrix, making low-temperature, gas- plasma sterilization unsuitable as a method of secondary sterilization of demineralized bone matrix.

Revascularisation of fresh compared with demineralised bone grafts in rats

Revascularisation of bone grafts is influenced by both the anatomical origin and the pre-implantation processing of the graft. We investigated the revascularisation by entrapment of 141Ce (cerium)-labelled microspheres in large, fresh and demineralised syngeneic grafts of predominantly cancellous (iliac bone) or cortical (tibial diaphysis) bone three weeks after heterotopic implantation in rats. The mean (SD) 141Ce deposition index (counts per minute (cpm) of mg recovered implant/cpm of mg host iliac bone) was higher in fresh iliac bone grafts, 0.98 (0.46) compared to that of demineralised iliac bone, 0.32 (0.20), p < 0.001, and fresh tibial bone grafts, 0.51 (0.27), p = 0.007. We found no significant difference in the mean 141Ce deposition index between fresh tibial bone grafts and demineralised tibial bone grafts, 0.35 (0.42), p = 0.4, or between demineralised tibial grafts and demineralised iliac bone grafts, p = 0.8. The results suggest that whereas fresh cancellous grafts are revascularised more completely than fresh cortical grafts, there is no difference in the revascularisation of demineralised cancellous and cortical grafts. In addition, fresh cancellous bone is revascularised more completely than demineralised cancellous bone, whereas there is no difference between fresh and demineralised cortical bone.

An evaluation of the capacity of differently prepared demineralised bone matrices (DBM) and toxic residuals of ethylene oxide (EtOx) to provoke an inflammatory response in vitro

Demineralised bone matrix (DBM) is a form of allogeneic tissue graft widely used in oral and maxillofacial procedures. There is a long history of controversy relating to the suitability of ethylene oxide gas (EtOx) as a terminal sterilisation agent for this graft, relating to its effects on the clinical performance of the grafts. Furthermore, the generation of a toxic residual chemical (ethylene chlorohydrin, ECl) during the ethylene oxide sterilisation of patellar tendon allografts has been implicated in the failure of these grafts owing to the induction of a localised inflammatory response. In this study we have investigated the capacity of a range of different DBM preparations, and ECl dilutions, to induce the production of three pro-inflammatory cytokines, interleukin-6 (IL-6), interleukin-1beta (IL-1beta), and tumour necrosis factor alpha (TNF-alpha) from human peripheral blood mononuclear cells (PBMNCs). The levels of EtOx and ECl in EtOx terminally sterilised DBM and mineralised bone grafts were measured by gas chromatography. It was found that the only factor capable of rendering DBM pro-inflammatory was the presence of small (<20 micrometre diameter) DBM particles. No other processing or sterilisation technique resulted in the DBM becoming pro-inflammatory. Although it was also found that DBM, when EtOx-sterilised, retained more ECI than mineralised bone grafts following a standard EtOx sterilisation protocol, ECl did not provoke an inflammatory response in vitro at levels up to and including those which are cytotoxic to PBMNCs.

Demineralized bone matrix as a biological scaffold for bone repair

Experimental models were created in rat fibula to represent impaired bone healing so that biological deficiencies that cause bone repair to fail or to be delayed may be investigated. These models consist of a 4-mm-long segmental defect, created in rat fibula by osteotomy, and fitted with a 7-mm-long tubular specimen of demineralized bone matrix (DBM) over the cut ends of the fibula. The experiments in this study involved various modifications of the DBM scaffold designed to reduce its osteoinductive activity: steam sterilization (sDBM), ethylene oxide sterilization (eoDBM), trypsin digestion (tDBM), and guanidine hydrochloride extraction (gDBM). Bone healing was evaluated by bending rigidity of the fibula and mineral content of the repair site at 7 weeks post-surgery. The sDBM scaffolds resorbed completely by 7 weeks and hence this model was a nonhealing negative control. Rigidities in the unmodified DBM and tDBM groups were comparable, whereas in the gDBM and eoDBM groups it was significantly reduced. Histologically, in the 4-mm defects repaired with unmodified DBM, direct and endochondral bone formation in the scaffold and the defect resulted in a neocortex consisting of woven and lamellar bone uniting the broken bone by 7 weeks post-surgery. We conclude that the eoDBM and gDBM groups represent failure or delay of the bone repair process when compared with the unmodified DBM group in which the process is analogous to normal bone healing.

Instrumented posterolateral lumbar fusion using coralline hydroxyapatite with or without demineralized bone matrix, as an adjunct to autologous bone

BACKGROUND CONTEXT

Autogenous posterolateral fusion with and without instrumentation has been reported with good results. However, difficult-to-fuse patients, such as smokers, elderly patients with poor bone quality and/or quantity, or patients with prior posterior surgeries, may have somewhat lower fusion rates.

PURPOSE

To determine the efficacy of coralline hydroxyapatite with or without demineralized bone matrix as a bone graft extender in a human clinical model with long-term follow-up.

STUDY DESIGN/SETTING

A retrospective series of 40 patients undergoing instrumented autogenous posterolateral lumbar fusion augmented with coralline hydroxyapatite with or without demineralized bone matrix.

PATIENT SAMPLE

Long-term clinical and radiographic follow-up were examined for 40 patients who underwent an instrumented posterolateral fusion only. Patients undergoing anterior lumbar interbody fusion (ALIF) procedures were not considered part of the sample.

METHODS

All patients underwent successful transpedicular fixation with autogenous posterolateral lumbar fusion. Fifteen cc of Pro Osteon 500 coralline hydroxyapatite (Interpore Cross International, Irvine, CA) was used at each level. An additional 10 cc of Grafton demineralized bone matrix gel (Osteotech, Eatontown, NJ) was used in 70% of these patients.

RESULTS

An overall fusion rate of 92.5% was achieved. Pain and function improvement were good but somewhat age dependent and correlated with the number of comorbidities. Patients with Grafton DBM gel had a lower fusion rate of 89.3%.

CONCLUSIONS

Based on this small retrospective review, coralline hydroxyapatite is an effective bone graft extender in difficult-to-fuse patients as an adjunct to autologous bone for posterolateral fusion of the lumbar spine when combined with rigid instrumentation.

Guided tissue regeneration with and without demineralized freeze-dried bone allografts for maxillary Class II furca invasions of rapidly progressive periodontitis

BACKGROUND

Guided tissue regeneration (GTR) using an expanded polytetrafluorethylene (ePTFE) membrane is an established treatment modality for periodontal disease. This study was designed to compare the effects of ePTFE membranes with and without demineralized, freeze-dried bone allografts (DFDBA) for treating maxillary class II buccal furca invasions of rapidly progressive periodonitis.

METHODS

Seven patients with pairs of maxillary class II buccal furca invasions comprised the study group. The clinical parameters investigated were probing depth, probing attachment level and marginal tissue recession. One defect from each pair of teeth was randomly selected for the ePTFE membrane and DFDBA group and the other tooth defect received ePTFE membrane treatment only. During the operation, horizontal probing depths at the buccal furcation areas were measured. The membrane was removed 6 weeks after insertion. All measurements were repeated 1 year later at surgical re-entry of the buccal furcation. The Wilcoxon ranked sum test was used to test the significance of the difference between the groups 1 year after treatment.

RESULTS

In the ePTFE membrane and DFDBA group, the mean probing depth reduction was 2.1 +/- 0.8 mm. The probing attachment gain was 2.6 +/- 1.0 mm and the bone fill was 3.1 +/- 1.7 mm. There was no statistically significant difference between the groups for these parameters. The marginal tissue recession was reduced 0.4 +/- 0.7 mm in ePTFE membrane and DFDBA group but increased 0.9 +/- 0.6 mm in ePTFE membrane only group. This difference was statistically significant (p = 0.016).

CONCLUSIONS

There was no difference in probing depth reduction, probing attachment gain or bone fill between the two treatment modalities for treating maxillary class II buccal furca invasion of rapidly progressive periodontitis. Marginal tissue recession can be significantly reduced with the treatment of combined ePTFE membrane and DFDBA.

Characterization of demineralized bone matrix-induced osteogenesis in rat calvarial bone defects: III. Gene and protein expression

Our previous studies of rat cranial defect repairs after the implantation of demineralized bone matrix (DBM) have demonstrated that healing occurs initially and principally by the direct induction and proliferation of osteoblasts derived principally from resident mesenchymal stem cells of the dura, and to a lesser extent by resident mesenchymal stem cells of the connective tissues beneath the skin flap. A small amount of cartilage is also synthesized after the direct process of ossification occurs. To further confirm the molecular phenotypes of the repair cells in rat cranial defects, the present study evaluated mRNA expression and synthesis of collagens I, II, and X and osteocalcin in the DBM-induced repair tissue by Northern blot analyses, autoradiography after in vivo (3)H-proline labeling of collagen, and immunohistochemistry. The results demonstrated that osteocalcin mRNA appeared in small amounts by day 4 and continued to increase over the experimental period. Much lesser quantities of collagen types II and X mRNAs appeared by day 6 and day 8, respectively. Collagen type I mRNA was present at all times examined but its expression significantly increased by day 5. Autoradiographic and immunohistochemical studies showed that type II collagen was not detected whereas type I collagen was synthesized on days 3-5. The data provide definitive molecular evidence confirming that the initial and by far the major pathway of cranial defects repair induced by implantation of DBM is by the direct induction of resident mesenchymal stem cells to osteoblasts and the direct formation of bone, which is spatially and temporarily distinct from the later formation of cartilage.

Composite autogenous bone and demineralized bone matrices used to repair defects in the parietal bone of rabbits

We compared the amount of new bone produced by endochondral and intramembranous autogenous bone grafts in the presence of demineralized bone matrices (DBMs) prepared from intramembranous bone (DBM(IM)) or endochondral bone (DBM(EC)). Thirty-five bone defects were created in the parietal bone of 20 New Zealand White rabbits. In the experimental groups, 5 defects were grafted with endochondral bone, 5 with endochondral bone mixed with DBM(IM)) (EC-DBM(IM)), 5 with intramembranous bone mixed with DBM(IM)(IM-DBM(IM)) and 6 with endochondral bone mixed with DBM(EC)(EC-DBM(EC)). In the control groups, 10 defects were left alone (passive control) and 4 were grafted with rabbit skin collagen (active control). They were all killed on day 14 and the defects were prepared for histological study. Serial sections were cut across the whole defect. Quantitative analyses were made on 202 sections of the experimental groups by image analysis. A total of 414%, 708%, and 85% more new bone was formed in defects grafted with composite EC-DBM(IM), IM-DBM(IM)and EC-DBM(EC), respectively, than those grafted with endochondral bone alone (P<0.001). No bone was formed in either passive or active controls. In conclusion, demineralized bone matrices, particularly those derived from intramembranous bone, have extremely high osteoinductive properties and greatly improve the integration of autogenous bone grafts in the skull.

Twisted plywood structure of an alternating lamellar pattern in cellular cementum of human teeth

Human cellular cementum was examined by scanning electron microscopy to elucidate the manner of the alternate lamellar pattern forming the cellular cementum. Specimens were demineralized, trimmed with a freezing microtome, and treated by NaOH-maceration. This procedure was chosen to avoid artifacts in the fibril arrangement, and to study the fibrous architecture in detail. For comparison, non-demineralized, polished and HCl-etched specimens were also prepared. In the NaOH-macerated specimens, the lamellar pattern of the cellular cementum conformed to the twisted plywood principle of bone lamellation with a periodic rotation of matrix fibrils resulting in an alternating lamellar pattern. In contrast, matrix fibrils were irregularly arranged without indication of rotation of matrix fibrils in the polished and etched specimens. Our results suggest that polishing and etching procedures cause damage to fibrils and fibril arrangement.

Clinical applications of composite intramembranous bone grafts

The aim of this article is to introduce the composite intramembranous bone graft mixed with demineralized bone matrix to the clinician and to demonstrate its various clinical applications in the field of clinical orthodontics in the form of case reports. Understanding the mechanism of healing of this composite bone graft provides sound experimental precedent that allows this graft material to become a predictable part of our future orthodontic management. The cases highlighted here took advantage of the several properties of the composite intramembranous demineralized bone matrix graft. An accidental loss of the buccal plate of bone occurred during extraction of a buccally placed premolar for orthodontic purposes. The defect was repaired using chin bone mixed with demineralized bone matrix, and the teeth were successfully moved into the grafted area. A 5-year follow-up showed a stable gingival condition at the grafted area. In this report, ridge augmentation with intramembranous demineralized bone matrix as an adjunct to orthodontic treatment allowed successful placement of endosseous implants. In conclusion, the same graft material was successfully used in the repair of a massive alveolar cleft. Long-term follow-up of these cases showed that this graft is a promising graft material that could be integrated into our orthodontic practice.

Characterization of matrix-induced osteogenesis in rat calvarial bone defects: II. Origins of bone-forming cells

Two experimental models that separated demineralized bone matrix (DBM) implants from the host bone were utilized to identify the origins of bone-forming cells in the repair of calvarial defects in rats. Rat DBM, Guanadine-HCl (Gdn-HCl) extracted insoluble residue of DBM, and Gdn-HCl extracted insoluble DBM to which the dialyzed Gdn-HCl extract was added back, were implanted in the two models which prevented cells of the adjacent host bone from participating in the repair. In addition, cells in the dura and in the subcutaneous tissue overlying the calvarial defect were locally labeled with (3)H-thymidine to identify the origins of those cells that were stimulated to divide and differentiate to osteoblasts. Histological studies of the temporal events that occurred during the healing process in these defect models, combined with (3)H-thymidine labeling demonstrated that the osteoblasts induced by DBM were initially derived from undifferentiated mesenchymal stem cells of the dura and later augmented by cells in the overlying connective tissue covering the defect, and not from cells in the cranial bone surrounding the circular defect. The cells of both dura and subcutaneous tissue were stimulated to proliferate and differentiate principally to osteoblasts and to a very much lesser extent to chondroblasts by DBM and by reconstituted components of DBM after Gdn-HCl extraction. Gdn-HCl-extracted insoluble DBM failed to induce bone or cartilage. These results indicate that the cytokines or other factors present in DBM are required to induce bone-forming cells derived from the dura and the overlying connective tissue for the repair of the calvarial defect.

Bioassayed demineralized bone matrix and calcium sulfate: use in bone-grafting procedures

BACKGROUND AND AIMS

A combination product of bioassayed, demineralized bone matrix (AlloGro, AlloSource, Denver CO) and calcium sulfate pellets (OsteoSet, Wright Medical Technology, Arlington TN) was utilized in a prospective clinical study in 50 patients in need of bone-grafting procedures. It was proposed that the osteoinductive activity of the demineralized bone matrix combined with the osteoconduction and rapid dissolution of the calcium sulfate pellets would complement each other in promoting bone formation.

MATERIALS AND METHODS

The patients were evaluated clinically and radiographically at regular intervals post-operatively by an independent clinician. A total 10-point healing score was used to determine healing characteristics and progress. Fifty patients (24 males and 26 females) were treated for benign bone lesions (35), nonunion (11), osteomyelitis (3), and acute fracture (1). The average age was 33 years (range, 3-64 years). Lesions were located in the femur (16), tibia (15), humerus (7), and other sites (12).

RESULTS

The average length of follow-up was 14 months (range, 6-32 months). Forty-nine of 50 patients healed their lesions (98%), requiring an average time to heal of 11.8 weeks (range, 3-48 weeks). There were no graft-related complications.

CONCLUSIONS

The results of this preliminary clinical study suggest that a combination of bioassayed demineralized bone matrix and calcium sulfate is very effective in treating benign lesions of bone, as well as nonhealing fractures, which is comparable to grafting with autograft. Future studies have been undertaken utilizing this combination in all acute operative settings and fracture management situations.

Xenogenic demineralized bone matrix: osteoinduction and influence of associated skeletal defects in heterotopic bone formation in rats

Demineralized bone matrix (DBM) was ectopically implanted in 36 male Wistar rats. In 18 of the animals a bone defect in the femoral condyles was also created: the left was filled with DBM and the right was left empty as a control. The animals were killed after 2, 4 and 6 weeks and new bone was histologically evaluated, comparing ectopic bone formation with or without distant bone injury. Results showed: (1) osteoinductivity of xenogenic DBM, and (2) earlier mineralization of ectopically implanted DBM in the group with associated skeletal injury. Our results show that xenogenic bone matrix acts as an osteoinductive material and that skeletal injury improves osteogenesis at distant sites.

Decalcification by ascorbic acid for immuno- and affinohistochemical techniques on the inner ear

An ascorbic acid decalcifying solution was applied to immuno- and affinohistochemical studies on the inner ear. Rat inner ears fixed in 4% paraformaldehyde in PBS or in 2% acetic acid in ethanol solutions were adequately decalcified in an ascorbic acid solution, at a temperature of 4 degrees C. The decalcifying solution was prepared with 1% ascorbic acid and 0.84% sodium chloride in distilled water (pH 2.5-2.6). The decalcification time was in a direct relationship to the specimen calcification. In this study, two neuroactive substances (gamma-aminobutyric acid and calcitonin gene-related peptide), neurofilaments, and the galectine endogenous lectin were successfully detected immunohistochemically.

Characterization of matrix-induced osteogenesis in rat calvarial bone defects: I. Differences in the cellular response to demineralized bone matrix implanted in calvarial defects and in subcutaneous sites

The cellular and biochemical sequences of osteogenesis induced by implanting demineralized bone matrix (DBM) in rat cranial defects and in subcutaneous sites have been studied by histological, histochemical, and biochemical techniques from days 2 to 28 after implantation. In subcutaneous sites, allogenic DBM induced cartilage cells and matrix for approximately the first 10 days which were subsequently resorbed and replaced by bone with little evidence for the classical endochondral sequence of ossification. In sharp contrast, the first cells that differentiated from the mesenchymal stem cells in the cranial defects were alkaline phosphatase (ALP) positively stained osteoblasts that appeared 3 days after implantation followed by synthesis of bone matrix which calcified shortly thereafter. A few clusters of cartilage cells were observed beginning at days 6-7 which were spatially distinct from the new bone and later resorbed. By day 28 the tissue induced in both the subcutaneous and cranial sites consisted almost solely of bone; however, the total amount of new bone in the subcutaneous implants was significantly less than the mass of bone formed in the calvarial defects. Bovine DBM induced bone formation in rat cranial defects to a very much lesser extent than allogenic DBM. A few cartilage cells were induced by bovine DBM in subcutaneous sites and rapidly resorbed and not replaced with bone. These results clearly indicate that the cellular sequence induced by allogenic and xenogenic DBM and the repair tissues synthesized are distinctly different in the cranial defects from those induced in the subcutaneous sites.