Use of demineralized bone implants in orbital and craniofacial reconstruction and a review of the literature

A retrospective study and review of the literature was performed on the use of demineralized bone implants for the correction of orbital and craniofacial defects. Demineralized bone implants heal by endochondral osteogenesis, inducing a transformation of local cells, as well as by osteoconduction, similar to autogenous grafts. They induce the chemotaxis and transformation of mesenchymal cells into chondroblasts, followed by ossification. They also act as a scaffold, with bone resorption taking place simultaneous with bone formation. This study reviewed 21 patients and 31 orbits, in which demineralized bone was used for orbitocranial reconstruction for congenital deformities (nine patients), after surgery for orbital fractures (seven patients: four floor, three roof), and orbital tumors (five patients). The surgical technique is described, and the results are discussed. The follow-up period averaged 15 months (6 months to 33 months). The overall resorption rate of the demineralized bone implants was estimated based on follow-up radiologic studies (facial films, computed tomography scans, and magnetic resonance imaging scans), as well as clinical examinations. All patients had a satisfactory to excellent result. The demineralized bone and Grafton (Osteotech, Shrewsbury, NJ, U.S.A.) was obtained from the Musculoskeletal Transplant Foundation of Holmdel, New Jersey, and it was all processed and reconstituted in a standard manner with Alloprep System. Surgical complications were cerebrospinal fluid leaks (one patient) with infection, transient chemosis, enophthalmos, and hypophthalmos. There were no complications related to demineralized bone alone. Properly prepared demineralized bone is a safe material for orbital reconstruction that eliminates the need for a second operative site to harvest a bone graft.

Comparison of bone regeneration with the use of mineralized and demineralized freeze-dried bone allografts: a histological and histochemical study in man

Mineralized (FDBA) and demineralized freeze-dried bone allografts (DFDBA) have been proposed as substitutes for autologous bone in oral surgery. The demineralization process has been shown, in rodents, to determine osteoinduction in tissues other than bone. Other investigators have reported poor clinical results, in man, with the use of DFDBA. The aim of the present study was a comparative light microscopical and histochemical analysis of bone regeneration processes, in man, with the use of FDBA and DFDBA. Our histological results showed that in DFDBA only the particles near the host bone were involved in the mineralization processes, while in FDBA even the particles that were farthest from the host bone were lined by osteoblasts, actively secreting osteoid matrix and newly formed bone. These results probably point to a more osteoconductive effect of FDBA. No osteoinduction was observed with FDBA or DFDBA.

Morphological changes of autoclaved autogenic bone implantation and autoclaved autogenic bone supplemented with allogenic demineralized bone matrix in rat parietal bone

The healing process of resected, autoclaved (121 degrees C, 20 minutes) and re-implanted bone in the rat parietal bone was compared with that of autoclaved bone that was supplemented with allogenic bone matrix (AAA-bone), using a scanning electron microscope and a light microscope. In the implant without AAA-bone, bone union and replacement of the autoclaved bone was seen at 2 weeks after implantation. There was no evidence of any inflammatory reaction around the autoclaved bone. The implant was gradually replaced by the new bone. In the implant with AAA-bone, the new bone formation around the implanted bone was more abundant than that of the implant without AAA-bone. An inflammatory reaction was also observed after 1 week. The replacement of the implant with AAA-bone was inferior to the nonsupplemented group. The reason for the poor replacement was the disturbance of the blood supply in the implant by abundant new bone formation. In these results, the autoclaved bone re-implantation was an excellent bone substitute with osteoconductive ability and biocompatibility. The implantation with AAA-bone was good for the new bone formation, but the position and the technique of supplement with AAA-bone have to be more deeply investigated.

The effect of demineralized bone matrix on the healing of intramembranous bone grafts in rabbit skull defects

A clinical dilemma exists regarding the type of bone that should be used to replace diseased or traumatized osseous tissue. Oral, plastic, and orthopedic surgeons normally implant viable mineralized endochondral (EC) autografts or demineralized EC allografts. A few clinicians have recognized the disadvantages of using EC bone in craniofacial surgery and advocated the replacement of intramembranous (IM) bone with healthy IM bone. However, controversy and uncertainty surround our understanding of these matrices to induce bone formation. Recent studies have advocated the use of other materials with osteoinductive properties, such as demineralized bone matrix (DBM). The proposed delivery system used in this study included IM bone grafts, DBM, and fixation of the IM bone graft. The purpose of this work was to gain further insights into the mechanism of healing of IM bone, in both the presence and the absence of DBM, and to compare the healing of IM bone grafts with that of DBM alone. Critical-sized (10 x 5 mm), full-thickness bony defects in rabbit parietal bone, devoid of periosteum, were filled with IM bone graft (mandible) alone, demineralized cortical bone matrix (DBM) alone, or combined DBM-IM bone graft, or were left unfilled. Histologic changes were examined 14 days later. The IM bone graft healed through IM ossification with no intermediate cartilage stage. DBM and composite DBM-IM healed through an EC ossification with an intermediate cartilage stage. It is hypothesized that the role of the IM graft is to induce neovascularization into the defect site, and that the undifferentiated mesenchymal cells in the perivascular region of the new blood vessels are induced by the bone morphogenetic protein(s) in the DBM into bone-forming cells.

Transforming growth factor-beta 1 in a guanidine-extracted demineralized bone matrix carrier rapidly closes a rabbit critical calvarial defect

Transforming growth factor beta 1 (TGF-beta 1) is a polyfunctional regulatory cytokine that has been shown to have roles in extracellular matrix interactions, soft tissue healing, and osteogenesis. Twenty-five microL of recombinant human TGF-beta 1 was added to guanidine-extracted demineralized bone matrix carrier and the implants were used to fill a 14-mm osteoperiosteal critical calvarial defect in New Zealand white rabbit model. The defects were allowed to heal over 4 weeks and the degree of new bone formation was assess by radiodensitometry and undecalcified bone histomorphometry techniques. Implants with TGF-beta 1 showed complete bridging of the gap with new bone in all cases, while the controls showed fibrous tissue repair of the gap with little or no new bone formation. These results demonstrate the ability of TGF-beta 1 to induce new bone in a brief time period in an inactive carrier.

Transitional structures in lamellar bone

Scanning electron micrographs of fractured surfaces of mineralized bone show a lamellar structure with alternating smooth and rough regions. These have been interpreted as corresponding to two distinct collagen fibril and mineral crystal orientations in a rotated plywood structure. However, in various bones, there are clear indications of transition zones between lamellae in which the fibrils, as well as the plate-like crystals, have intermediate orientations. Strong evidence for intermediate collagen fibril orientations comes from vitrified cryo-sections of demineralized bone. These show zones of fibril segments graded in length between more homogenous regions of fibrils roughly parallel to the specimen section. Evidence for intermediate crystal orientations comes from transmission electron micrographs and electron diffraction patterns of crushed bone fragments. A tentative scheme is presented for an interlamellar transition zone, involving rotation about the collagen fibril axis as well as tilting of this axis parallel to the plane of the interlamellar boundary. Although it may be convenient to think of the structure of lamellar bone as being composed of alternating thick and thin lamellae, it is probably more correct and biologically more relevant to consider one pair of lamellae as the product of a single depositional cycle of varyingly oriented collagen fibrils that subsequently mineralize.

Induction of bone by a demineralized bone matrix gel: a study in a rat femoral defect model

Demineralized bone matrix contains osteoinductive factors and stimulates filling of gaps and defects with bone; however, it is difficult to handle by itself and various preparations have been tested. Demineralized bone matrix with a gel consistency now is available for clinical use. We studied, in a femoral segment defect in the rat, the effects of rat demineralized bone matrix gel with and without a ceramic substratum. This preparation is analogous to the human demineralized bone matrix in the same carrier, used clinically for humans. One hundred adult male Fischer rats were divided into 10 experimental groups. Independent variables included the presence or absence of hydroxyapatite ceramic cylinders, the presence of demineralized bone matrix in carrier or carrier alone (glycerol), and the duration of observation (1, 2, and 4 months). Defects filled with the gel alone had significantly higher radiographic scores for host-graft union at 4 months compared with ceramic with the gel, ceramic alone, or carrier alone. Demineralized bone matrix gel significantly increased the total histologic score for host-graft union, whether ceramic was present or not, and a three-way interaction occurred among ceramic, the gel, and time. Demineralized bone matrix gel was an effective inducer of bone formation in this model. An additional substratum was not required; in fact, significantly more bone was formed in the absence of the ceramic cylinder. Neither the gel nor the ceramic were impediments to revascularization of the defect. Host-graft union was enhanced by demineralized bone matrix gel but not by the ceramic cylinder.

Delivery of demineralized bone powder by fibrin sealant

The main purpose of this study was to determine whether the use of fibrin sealant as a delivery vehicle for demineralized bone powder would result in bone induction in heterotopic and orthotopic sites. Rat demineralized bone powder alone or in different concentrations of fibrin sealant matrix (4, 8, 15, and 45 mg/ml) was bioassayed for bone induction by implantation in intramuscular sites. Distribution of treatment groups was as follows: demineralized bone powder alone (n = 12), demineralized bone powder plus 4 mg/ml fibrin sealant (n = 11), demineralized bone powder plus 8 mg/ml fibrin sealant (n = 11), demineralized bone powder plus 15 mg/ml fibrin sealant (n = 11), demineralized bone powder plus 45 mg/ml fibrin sealant (n = 10), 4 mg/ml fibrin sealant (n = 13), and 45 mg/ml fibrin sealant (n = 11). In a second group of rats, 8-mm critical-sized calvarial defects were created and treated with demineralized bone powder plus 30 mg/ml fibrin sealant. Intramuscular implants were retrieved after 28 days, while calvarial implants were retrieved at 28 days (n = 8), 3 months (n = 8), or 4 months (n = 5). Implants were then x-rayed and submitted for histology. Results showed bone formation as evidenced by radiopacity and histology. Radiopacity measurements of demineralized bone powder implants alone or in a fibrin sealant matrix were associated with immature woven bone at the implantation site. Fibrin sealant allowed bone formation by demineralized bone powder to occur, improved the handling of demineralized bone powder, and facilitated the shaping of implants.

Structural evaluation of human and sheep bone and comparison with synthetic hydroxyapatite by FT-Raman spectroscopy

The composition of whole human and sheep cortical bone tissue, and of a synthetic hydroxyapatite (P120), were compared using Fourier transform Raman (FT-Raman) spectroscopy. Deproteination procedures to remove the bulk of the collagen present in bone tissue allowed isolation of the mineral phase. A comparison of the spectra obtained from both whole and deproteinated bone with those of synthetic hydroxyapatite showed direct correlation only in the region of 952 cm-1 (symmetric P-O mode). In contrast, human and sheep bone were very closely matched in both, the organic and inorganic structures. The results demonstrate that deproteination of bone is not a necessary precursor to obtain spectral information.

The anatomy of bone sialoprotein immunoreactive sites in bone as revealed by combined ultrastructural histochemistry and immunohistochemistry

Bone sialoprotein was immunolocalized at the EM level in thin Lowicryl K4M sections of rat bone. Because of the unconventional EM morphology of the bone matrix seen in thin demineralized acrylate sections, the pattern of immunolabeling was compared with detailed structural images of demineralized bone obtained using an en bloc treatment of tissue samples with the cationic electron 'dye,' Malachite Green (MG), which provides stabilization and retention of anionic material throughout specimen processing. A system of structures corresponding to the sites of bone sialoprotein (BSP) immunoreactivity, as seen in Lowicryl K4M this sections, could be readily identified in the MG-treated, epoxy thing sections. This system includes the cement lines, and aggregates of similar material within mineralized bone and mineralizing osteoid. The virtual identity of BSP distribution with the arrangement of the MG-visualized material indicates that a BSP-enriched, noncollagenous phase can be demonstrated using different, unrelated tissue preparation and imaging protocols for EM. Besides improving our understanding of the distribution of bone sialoprotein in bone, these data assign a previously unrecognized structural dimension to noncollagenous material in the bone matrix.

Cranioplasty in the growing canine skull using demineralized perforated bone

This study was designed to test the hypothesis that demineralized perforated bone matrix implant from canine skull and tibia induces new bone formation within the calvarial defect comparable with the bone induced by autogenous graft. We also were interested in determining whether demineralized perforated bone matrix implants from membranous bone have greater osseoinductive capacity in the calvarial area than demineralized perforated bone matrix implants from endochondral bone. Forty 12-week-old purebred beagles were used. Group I consisted of animals with unrepaired surgically created calvarial defects healed by secondary intention (n = 10). Group II consisted of animals with surgically created calvarial defects in which the bone was removed and replaced with an autograft (n = 10). Group III consisted of animals with surgically created calvarial defects in which the bony defect was closed with a demineralized perforated bone matrix implant obtained from beagle calvaria (n = 10). Group IV consisted of animals with surgically created calvarial defects in which the bony defect was closed with a demineralized perforated bone matrix implant obtained from beagle tibia (n = 10). The two control groups (I and II) allowed us to isolate the inductive capacity of demineralized perforated bone matrix implants and compare it with the healing of the bone defects left unrepaired or repaired with calvarial autografts. Animals were sacrificed after 8 and 12 weeks. In the present study we were able to verify that demineralized perforated bone matrix implants are well accepted in the calvarial defects with little tissue reaction and remarkably little osteoclastic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Flexural rigidity in partially demineralized diaphyseal bone grafts

Control of biomechanical properties of demineralized diaphyseal bone allografts is required for their clinical application. Therefore, the changes in flexural rigidity in human fibulae were investigated as a function of the demineralization depth using a nondestructive bending test. Starting at the facies medialis, the flexural rigidity was determined in 24 planes at 15 degrees sequential angular increments, which allowed data collection around the circumference of the bone. Test bones included 4 pairs of left and right human fibulae and 15 single fibulae. The elliptical distribution of the flexural rigidity of left and right fibulae and single fibulae before and after demineralization was compared. The stiffness index and the area ratio were defined as parameters to describe the mechanical status of the test bones. Results show that the rigidity of diaphyseal bones is strongly dependent on the reduction of their cortical thickness by demineralization. A mathematical model allowing prediction of the reduction of the rigidity of diaphyseal bone grafts as a function of the demineralization depth is presented.

Ethylene oxide gas sterilization does not reduce the osteoinductive potential of demineralized bone in rats

It has been shown that different sterilization procedures of demineralized bone may influence its osteoinductive properties. The aim of this study was to evaluate the effect of ethylene oxide sterilization for 1, 3, and 6 hours on the osteoinductive potential of allogeneic demineralized bone implanted heterotopically in rats. Sixty male Wistar rats were randomly assigned to one of four groups, A through D, and four demineralized bone chips (2.8 mg) were implanted in a pouch created between the right oblique abdominal muscles in each animal. In Group A, the demineralized bone was implanted without prior sterilization of the material, whereas the demineralized bone implanted in Groups B, C, and D had been sterilized in ethylene oxide gas for 1, 3, or 6 hours, respectively, and aerated for 48 hours. At 4 weeks postoperatively, bone formation was evaluated quantitatively by strontium 85 uptake and qualitatively by light microscopy of histological sections. One-way analyses of variance at the 0.05 level revealed no significant difference in strontium 85 uptake of the different groups, and no qualitative differences in osteoinduction could be detected by light microscopy. Ossicles consisting of bone and bone marrow were seen in the recovered implants of all groups.

Response to demineralized bone matrix implantation in foals and adult horses

Equine demineralized bone matrix, particle size 2 to 4 mm, was implanted SC and IM in 4 foals and 4 adult horses. The implants were removed between 5 and 8 weeks after implantation. Bone formation was induced by SC and IM implantations in all animals. The implantation site had a marked effect on the amount of bone that developed, bone being formed earlier and in greater amounts when the matrix was implanted IM. The amount of bone formed increased with increasing time after matrix implantation at both sites. Demineralized bone matrix implantation also led to formation of small amounts of chondroid tissue; this tissue was more common in IM than SC matrix implants, and increased in amount with increasing time after implantation. Formation of this chondroid tissue did not precede the formation of bone, and there was no evidence that implantation of demineralized bone matrix in horses induced endochondral ossification. Age of the host did not appear to affect the response.

In vivo evaluation of demineralized bone matrix as a bone graft substitute for posterior spinal fusion

STUDY DESIGN

Posterior lumbar spinal fusion segments were evaluated in 9 adult mongrel dogs 6, 12, and 26 weeks after implantation. Four sites on each animal received implants consisting of demineralized bone matrix alone, demineralized bone matrix with allograft bone, allograft bone alone, and autograft bone. Each unilateral fusion spanned one motion segment with one intervening vertebral level left undisturbed using T13-L7. The fusions were evaluated radiographically, mechanically, and histologically.

OBJECTIVE

The purpose of this study was to determine the efficacy of demineralized bone matrix as a bone graft substitute for stable posterior spinal fusion.

SUMMARY OF BACKGROUND DATA

Posterior spinal fusion is a procedure commonly performed for spinal stabilization. Increasing the incidence and speed of stable spinal fusion is a primary goal in spinal surgery. Concerns have developed regarding the graft material used to induce bone healing at the fusion site. The advent of osteoinductive materials, such as demineralized bone matrix, may eliminate the need to harvest autograft bone and may circumvent the immunologic response and lower osteogenic potential associated with allograft bone.

METHODS

The quality of fusion and new bone formation was evaluated radiographically using plain films, computed tomography, and magnetic resonance imaging. After the dogs were killed, each fusion segment was evaluated mechanically in torsion to determine stiffness and histologically to determine qualitative parameters of new bone formation and remodeling.

RESULTS

Radiographic studies showed that autograft bone sites achieved stable fusion by 26 weeks after surgery. Conversely, the demineralized bone matrix alone and with allograft bone demonstrated some new bone formation at 6 and 12 weeks, but did not achieve fusion by 26 weeks. The fusion sites of allograft bone alone showed minimal new bone formation at all time periods. Mechanically, the autograft fusion sites demonstrated torsional stability that was significantly greater than that of all other fusion sites at all time periods. The remaining fusion sites showed equivalent torsional stiffness at all time periods. Histologic analysis confirmed the radiographic and mechanical findings.

CONCLUSIONS

The results indicate that demineralized bone matrix alone or with allograft bone is ineffective in achieving stable posterior spinal fusions.

Endogenous lipids in matrix-induced bone morphogenesis

Demineralized matrix was delipidized with chloroform methanol before and after demineralization and implanted in muscle of allogeneic rats. Because lipids are difficult to separate completely from bone collagen, another preparation was gelatinized and delipidized with either chloroform methanol or acetone or both. Bone matrix demineralized without delipidization induced formation of a spherical-shaped deposit of new bone, which was remodeled to form a shell of cortical bone and central pool of normal hematopoietic bone marrow. When the bone was delipidized, only 20% to 25% was resorbed and replaced by new bone; unresorbed matrix failed to recalcify. Gelatinized bone matrix delipidized before implantation was even less well resorbed or replaced by new bone, but 12% to 44% of the matrix residue recalcified. The new deposits of bone were colonized by blood-borne bone marrow-derived stem cells and developed central pools of normal hematopoietic bone marrow. Recalcified residual matrix did not develop bone marrow. Additional investigations are required to determine whether the host bed adipocytes provide the phospholipids for recalcification of bone matrix. There was no preliminary recalcification in matrix-induced bone development, even though the 2 processes may occur simultaneously under specified experimental and pathologic conditions. Additional investigations are in progress to determine whether certain acetone soluble lipids may form the endogenous delivery system for bone morphogenetic protein and induced bone development.

Injectable bone marrow preparations to stimulate osteogenic repair

The great versatility of bone marrow transplants based on stem cell activity has been demonstrated successfully for a variety of previously untreatable hemopoietic conditions. Autologous bone marrow delivered by percutaneous injection or by direct transplant as a composite graft also has proven effective for osteogenic stimulation in a series of 100 skeletal healing problems, including delayed unions and nonunions of fractures, arthrodeses, and bone defects. The efficiency of marrow to form bone can be increased by a number of methods, including differential centrifugation and composite grafts of marrow with demineralized bone matrix and other carriers or stimulatory factors.

Effect of demineralized bone matrix on bone growth within a porous HA material: a histologic and histometric study

Coralline hydroxyapatite (cHA) is an osteoconductive material currently being used as a bone graft substitute. Created by the hydrothermal conversion of the calcium carbonate skeleton of coral to hydroxyapatite, this material has a porous structure similar to cancellous bone. Addition of demineralized bone matrix (DBM) would conceivably create a composite with both osteoconductive and osteoinductive properties. This pilot study evaluated the healing of rabbit cranial defects that had been filled with cHA or cHA augmented with a DBM gel formed by adding glycerol to the DBM particulate. Data from these were then compared to unfilled defects from a previous study. Results indicated enhancement of new bone formation and an increase in the rate of healing in the defects filled with the cHA-DBM gel composite. Further studies are warranted.

Titanium implant insertion into dog alveolar ridges augmented by allogenic material

The purpose of this investigation was to evaluate whether titanium endosseous implants would osseointegrate in dog alveolar ridges augmented by allogenic material. In 8 dogs en bloc resection, including 2 pre-molars, was performed bilaterally in the maxilla and the mandible. After a healing period of 6 weeks allogenic, demineralized and lyophilized dentin or bone was implanted subperiosteally. Titanium implants were installed 5.5 months later in some of the regions. Light and fluorescence microscopic evaluation revealed fibrous encapsulation of the implanted allogenic material, no osteoinduction and only minimal osteoconduction, few multinuclear giant cells and a sparse inflammatory reaction. The titanium implants healed mainly by fibrous encapsulation.

Effect of storage on osteoinductive properties of demineralized bone in rats

A requirement for the clinical use of demineralized bone is the possibility of storing the material without loss of its osteoinductive properties. Seventy-five 8-week-old male Wistar rats were randomly assigned to one of five groups of 15 rats each. Lyophilized demineralized allogeneic bone was prepared and implanted in the abdominal muscle either without prior storage (control group) or after storage for 9 or 14 months at -70 degrees C or 4 degrees C (four experimental groups). Bone formation in the implants was evaluated quantitatively 4 weeks postoperatively by measuring the strontium 85 uptake of the recovered implants. Storage for 9 months at both temperatures did not affect the osteoinduction, whereas storage for 14 months at both temperatures led to a statistically significant decrease in osteoinduction.

Banked bone

Many forms of banked bone allograft are available to the surgeon. Among the grafts available are fresh, fresh-frozen, freeze-dried, and demineralized bone. Each one of these grafts carries risks and has unique limitations and handling properties. In order to use these materials appropriately, the surgeon must be familiar with the properties of each and must feel confident that the bone bank providing the graft is supplying a safe and sterile graft. In the future, allograft bone will become obsolete. In place of banked bone, surgeons will use synthetically produced bone morphogenic protein that has been incorporated into an absorbable matrix. These materials will exist in a time-release form that will allow the graft material to grow and mature with the patient. Until this goal is achieved and is available clinically, surgeons must be familiar with the capabilities and limitations of banked bone graft.

[The use of demineralized bone brephomatrix in the plastic repair of different postoperative defects in the jaws]

The aim of this research was assessment of the results of bone brephoplasty of the jaws. Bone tissue defects after cystectomy, granulectomy, and tooth removal were filled with fragmented transplant, demineralized osseous brephomatrix. Low-frequency ultrasound was used for antibacterial treatment of the recipient osseous bed. A total of 103 patients were operated on, brephoplasty was carried out in 60. Demineralized osseous brephomatrix is characterized by excellent plastic and osteoinductive properties, due to which bone regeneration processes are completed 1.5-2 times sooner in comparison with the control.

[The stimulation of reparative regeneration with demineralized bone matrix in puncture osteoplasty operations for bone cysts in children]

The authors present the data on positive influence of demineralized osteomatrix (DOM) on the osteogenesis in the experimental conditions. On the basis of data received the method of puncture osteoplastic operation with DOM application was developed. Puncture method was applied in 38 children. In 6 months 31 children cyst were liquidated, osteoarchitectonics was reduced, in 7 children rough trabecular picture remains.

Preparation of unfixed and undecalcified frozen sections of adult rat periodontal ligament during experimental tooth movement

The upper first molars of adult male rats were moved for 7 days and unfixed, undecalcified frozen sections of the molar periodontal ligament were prepared and observed. The upper jaws of the rats were immersed rapidly in liquid nitrogen and sectioned with a cryostat using a super hard knife. Five micrometer serial sections were cut, collected, freeze-dried and observed with both light and scanning electron microscopy. Electron probe microanalysis (EPMA) was also performed on the sections. On the tension side of the periodontal ligament, periodontal fibers were stretched and the osteoblasts were aligned on the osteoid, which showed metamasia with the toluidine blue stain. On the pressure side where the periodontal ligament was extremely compressed, tissue degeneration was caused by tooth movement and the osteoclasts were observed on the bone surface adjacent to the degenerating tissues. Scanning electron microscopy revealed a network arrangement of the collagen fiber bundles on the tension side, but not on the pressure side of the periodontal ligament. The spectrum obtained from EPMA of the osteoid demonstrated X-ray (Ka) peaks of Na, P, S, K and Ca.

Biochemistry of bone induction and dystrophic calcification

The propensity of crosslinked collagen matrices to calcify when implanted in animals and human beings is well documented. This article demonstrates that the covalent binding of the biphosphonate, 3-amino-1-hydroxy-propane-1-1-diphosphonic acid, to active bone matrix inhibits bone formation as well as dystrophic calcification. The inhibitory effects on calcium accumulation and alkaline phosphatase activity are greater than those achieved by inactivation of the matrix by protease digestion of the bone morphogenetic factors present in demineralized bone. Whereas bone formation is a cell-mediated effect, artificially crosslinked collagen matrices calcify extensively inside diffusion chambers, reflecting a non-cell-mediated nucleation process. The fundamental differences described should shed light on new modalities to modulate these processes in living systems.

Effect of polylactic acid on osteoinduction of demineralized bone: preliminary study of the usefulness of polylactic acid as a carrier of bone morphogenetic protein

To evaluate the usefulness of polylactic acid (PLA), a bioabsorbable and plastic polymer, as a carrier of bone morphogenetic protein (BMP), a preliminary study has been carried out to investigate any negative effect of PLA on osteoinduction of demineralized bone (DB). PLA (10,600 mol. wt) was mixed with DB particles (1-1.5 mm square) prepared from rat femurs and laid subcutaneously on the intercostal muscle of 4-week-old Wistar rats. The PLA/DB pellets were harvested at 2, 4, 8 and 24 weeks after the operation, and prepared for light microscopic examination. Histological examination revealed cartilage formation at 2 weeks and new bone formation at 4 weeks. Extensive bone and marrow formation were observed at 24 weeks. PLA was gradually absorbed and completely disappeared at 24 weeks to be replaced by connective tissue. These results demonstrate that PLA does not have a negative influence on the osteoinductive activity and that PLA could well be a promising bioabsorbable carrier of BMP.

Effect of 1-hydroxyethane-1,1-diphosphonic acid (HEDP) on new bone formation induced by bone matrix gelatin (BMG)

The effect of the biphosphonate 1-hdroxyethane-1,1 diphosphonic acid (HEDP) on induced ectopic osteoneogenesis was studied by light and electron microscopy. Demineralized bone matrix gelatin (BMG) was implanted into the rectus abdominis muscle of 8-week-old Sprague-Dawley rats, HEDP was administered subcutaneously with a mini-osmotic pump, and histological changes were examined 4 days, 1, 2 and 3 weeks later. Four days after implantation, "acellular mineral deposition" in the control group was suppressed in the HEDP group. Two weeks after BMG implantation, cartilage formation was more intensive in the HEDP-treated group than in the control group. Three weeks after implantation, new lamellar bone with bone marrow was observed in the control group, while immature osteoid tissue detected by type II collagen in the central area was prominent in the HEDP-treated group. HEDP-treatment also suppressed the appearance and activity of osteoclast-like cell.