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PubMed1997

Quantitative rates of in vivo bone generation for Bioglass and hydroxyapatite particles as bone graft substitute.

Rates of in vivo bone generation were characterized by point-counting analysis of particulate Bioglass and synthetic hydroxyapatite (HA) in rabbit femora. New bony tissue was observed in approximately 20% of the image area around Bioglass particles at 1 wk, and the degree of trabecular bone growth increased with time. The interparticle space of Bioglass was filled by 80% bonding bone between 6 and 12 wk. The rate constants of trabecular bone growth in the presence of Bioglass were approximately 10.9x10(-3) d(-1) at the periphery of the implantation site. HA particles led to smaller rate constants of approximately 4.6x10(-3) d(-1) at the periphery, and the HA particles developed very small amounts of bridging bone. The quantitative rate of bone growth matched well with previously measured bioactive indices of the materials.

Journal Article↗
PubMed2006

[Repair of mandibular central fissures in rabbits with hBMP-2 gene modified tissue engineered bone].

PURPOSE: To evaluate the effectiveness of the tissue engineered bone substitute loaded with periosteal-derived osteoblasts (POBs) transfected by adenovirus mediated human bone morphogenetic protein-2 gene (Ad-hBMP-2) in the repair of rabbit mandibular central fissures. METHODS: 45 rabbits with the soft tissue in the mandibular central fissures removed were randomly divided into 5 groups, group I: Ad-hBMP-2 transfected POBs/bioglass group (n=10); group II: adenovirus mediated enhanced green fluorescent protein (Ad-EGFP) gene transfected POBs/bioglass group (n=10); group III: untransfected POBs/bioglass group (n=10); group IV: single bioglass group (n=10); group V: control group (n=5). The above bone substitutes were implanted in the rabbit mandibular central fissures respectively except group V. The samples were studied by gross, X-ray, histomorphology, histomorphometrical analysis and biomechanics after 2, 4, 8, 12 weeks respectively. One-way ANOVA was used for statistical analysis. RESULTS: In gross view, the rabbit mandibular central fissures in group I were replaced by new bone including cortical bone from the 4th week. X-ray examination showed that the higher bone density was found in the rabbit mandibular central fissures of group I 4 to 8 weeks after implantation. Histomorphometrical analysis showed much more new bony callus in group I than in other groups (P<0.01). The maximal anti-bending load and bending rigidity of the implanted bone substitute of group I were significantly higher than those of group II, III and IV (P<0.01). CONCLUSION: The tissue engineered bone substitute loaded with POBs transfected by human BMP-2 gene could get the best result in the repair of rabbit mandibular central fissures, therefore, it is likely to be used in the repair of alveolar clefts.

Adenoviridae↗
PubMed2002

[Autogenous bone versus beta-tricalcium phosphate graft alone for bilateral sinus elevations (2-3D CT, histologic and histomorphometric evaluations)].

INTRODUCTION: When the maxilla is edentulous and the alveolar process is extensively absorbed, a dental root can be implanted only after the implantation of bone or a bone-substitute. Only in this way can the subjective and objective negative features associated with a removable prosthesis be avoided. Many forms of bone-substitutes are known. Freely taken bone from the patient generally serves as the gold standard for the classification of bone-substitutes. AIMS: The aim of our work was to compare two materials (the patient's own bone and beta-tricalcium phosphate) in the same patient. METHODS: Ten patients were selected who for some reason did not want or could not wear a removable prosthesis. The maxilla was so atrophied that bone or bone-substitute implantation was necessary before the dental root could be implanted. The maxilla had to be elevated from inside (sinus elevation) and thickened from outside (onlay-plasty). Bone was taken in the usual manner from the hipbone. For the internal elevation, such autogenous bone was utilized on one side, and beta-tricalcium phosphate granulate on the other. The formation of new bone and the rate of bone formation were followed by clinical methods and by radiological, histological, and histomorphometric examinations. RESULTS: The implantation succeeded clinically in all ten patients: one year later they all received a fixed bridge. The radiological and histological examinations demonstrated good bone formation on both sides. As concerns the rate of formation of new bone, there was practically no difference after the implantation of autogenous bone or beta-tricalcium phosphate. CONCLUSIONS: This study has therefore provided further evidence that, when certain bone deficiencies are to be eliminated, the unpleasant phenomena accompanying the removal of the patient's own bone can be avoided through the use of new synthetic materials. Accordingly, when comparing the present results with the findings of other authors, beta-tricalcium phosphate may be considered a good graft material even without autogenous bone.

Biocompatible Materials↗
PubMedDate not supplied

The culture of human osteoblasts upon bone graft substitutes.

In order to assess the ability of six potential bone graft substitutes to support the growth of human osteoblasts, these cells were grown in culture and then plated onto fragments of the six materials and cultured for a further period of 15 days. Tests to confirm the osteoblastic phenotype of the cells included spectrophotometric alkaline phosphatase assay; Western blotting of secreted osteocalcin, osteonectin, bone sialoprotein, and collagen type I; and mineralization within the cultures provided with a supplemented medium. Cells were seeded onto the materials in 24-well plates (Nunc, Naperville, IL) at density levels 12,500 cells/cm2 and 25,000 cells/cm2. Specimens were examined after the 15-day culture period by scanning electron microscopy. At a seeding density of 12,500 cells/cm2 results showed that the human osteoblasts had greatest affinities for demineralized rat bone and demineralized Surgibone, whilst few osteoblasts were found attached to Pyrost, Surgibone, or coral. The collagen matrix of Callopat hydrated in the culture media exposing the hydroxyapatite crystals within it, and these became the foci for cell attachment and growth. At a seeding density of 25,000 cells/cm2 the osteoblasts had attached to and proliferated upon the surfaces of all the materials, forming multilayers, with the exception of Surgibone. These experiments demonstrated that all the materials, with the exception of nondemineralized Surgibone, were biocompatible for human osteoblasts.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed2001

Comparison of anorganic bovine mineral with and without synthetic peptide in a sinus elevation: a case study.

A new tissue-engineered bone substitute that reportedly has the capability to enhance bone regeneration over the more classical bone substitutes, such as decalcified freeze-dried bone allograft and xenograft, was evaluated in bilateral sinus procedures. Anorganic bone mineral with and without a synthetic peptide (P-15) were grafted separately in bilateral sinuses. At the time of implant placement and at four months, trephine cores were obtained and the quality of the grafts deciphered by histomorphometry. The P-15 grafted sinus yielded 45% vital bone compared with 13% for the anorganic bovine material alone. The P-15 dramatically increased the quality and quantity of grafted bone in the sinus.

Adult↗
PubMed2005

Microporosity enhances bioactivity of synthetic bone graft substitutes.

This paper describes an investigation into the influence of microporosity on early osseointegration and final bone volume within porous hydroxyapatite (HA) bone graft substitutes (BGS). Four paired grades of BGS were studied, two (HA70-1 and HA70-2) with a nominal total porosity of 70% and two (HA80-1 and HA80-2) with a total-porosity of 80%. Within each of the total-porosity paired grades the nominal volume fraction of microporosity within the HA struts was varied such that the strut porosity of HA70-1 and HA80-1 was 10% while the strut-porosity of HA70-2 and HA80-2 was 20%. Cylindrical specimens, 4.5 mm diameter x 6.5 mm length, were implanted in the femoral condyle of 6 month New Zealand White rabbits and retrieved for histological, histomorphometric, and mechanical analysis at 1, 3, 12 and 24 weeks. Histological observations demonstrated variation in the degree of capillary penetration at 1 week and bone morphology within scaffolds 3-24 weeks. Moreover, histomorphometry demonstrated a significant increase in bone volume within 20% strut-porosity scaffolds at 3 weeks and that the mineral apposition rate within these scaffolds over the 1-2 week period was significantly higher. However, an elevated level of bone volume was only maintained at 24 weeks in HA80-2 and there was no significant difference in bone volume at either 12 or 24 weeks for 70% total-porosity scaffolds. The results of mechanical testing suggested that this disparity in behaviour between 70 and 80% total-porosity scaffolds may have reflected variations in scaffold mechanics and the degree of reinforcement conferred to the bone-BGS composite once fully integrated. Together these results indicate that manipulation of the levels of microporosity within a BGS can be used to accelerate osseointegration and elevate the equilibrium volume of bone.

Animals↗
PubMed1988

Porous hydroxyapatite as a bone graft substitute in cranial reconstruction: a histometric study.

To assess the potential of a porous hydroxyapatite matrix to serve as a bone graft substitute, bilateral 15 X 20 mm craniectomy defects were reconstructed in 17 dogs with blocks of implant and split-rib autografts. Specimens were retrieved at 3, 6, 12, 24, and 48 months, and undecalcified sections were prepared for microscopy and histometry. The implant and graft cross-sectional areas did not change with time, documenting their equivalent ability to maintain cranial contour. Bone ingrowth extended across the implant from one cranial shelf to the other in 15 specimens. Little apparent bone ingrowth was seen in most graft specimens. Two implants and three grafts were nonunited, possibly due to lack of fixation or the orientation of the histology sections. The implant specimens were composed of 39.3 percent hydroxyapatite matrix, 17.2 percent bone ingrowth, and 43.5 percent soft-tissue ingrowth. The graft specimens were composed of 43.7 percent bone and 56.3 percent soft tissue. This study supported the thesis that a porous hydroxyapatite matrix may function in part as a bone graft substitute. The brittle hydroxyapatite matrix undoubtedly became stronger with bone ingrowth, but the degree of cranial protection achieved was not measured in this study. The size of the cranial defect used in this study did not permit estimation of the distance over which bone ingrowth may be reliably expected. There remains a need for greater understanding of the causes of nonunion, the extent of predictable ingrowth depth, and the strength of the resultant implant-bone composite.

Animals↗
PubMed2005

Local and systemic levels of tobramycin delivered from calcium sulfate bone graft substitute pellets.

We asked if tobramycin-loaded calcium sulfate pellets could be used to maintain high local site antibiotic concentrations for an extended period with minimal systemic levels and without adverse effects on vital organs. Calcium sulfate pellets loaded with 10% tobramycin were implanted in contained medullary defects in the proximal humeri of canines. The number of pellets implanted was calculated to yield an equivalent human maximum prescribed dose, and 1.8-fold this dose. These doses converted to approximately 20 mg/kg, and 36 mg/kg, respectively, for the canine. Local and systemic tobramycin levels, pellet resorption, bone response, clinical pathology parameters, and histopathologic responses of potential target organs were analyzed to determine if there was any adverse response for a 28-day period. Serum tobramycin was elevated for less than one day while local levels remained elevated for at least 14 days, and in some animals, 28 days. Tobramycin delivered locally from calcium sulfate pellets had no apparent adverse effect on clinical pathology parameters or on any of the organs that were analyzed. In addition, bone formation and pellet resorption followed patterns typically seen with calcium sulfate materials.

Animals↗
PubMed2002

A concept for the treatment of various dental bone defects.

Untreated dental bone defects usually lead to resorption of alveolar bone. Filling these defects with bone substitute material prevents resorption of bone, preserves the alveolar ridge, and provides sufficient bone for immediate or subsequent implant placement. A variety of bone substitutes is available. They differ in origin, consistency, particle size, porosity, and resorption characteristics. We have treated almost 1000 bony defect sites in 267 patients with the bone regeneration material Cerasorb. Being resorbed simultaneously with the formation of new bone, it is completely replaced by the patient's own vital bone within 6 to 12 months. The representative cases described in this paper demonstrate the successful use of the pure-phase beta-tricalcium phosphate ceramic in the treatment of all dental bone defects.

Absorbable Implants↗
PubMed1989

A study of the mechanical strength of long bone defects treated with various bone autograft substitutes: an experimental investigation in the rabbit.

This study was designed to determine which of several bone grafting materials would be the most efficacious substitute for autogenous bone graft in the treatment of segmental long bone defects. The experimental model was a 1-cm defect in the rabbit ulna. The control group had nothing implanted in the defect. The six grafts tested were: (a) autogenous iliac crest bone, (b) autogenous cortical bone (ulna), (c) hydroxylapatite, (d) hydroxylapatite-demineralized bone matrix (allograft) composite graft, (e) freeze-dried bone (allograft), and (f) demineralized bone matrix (allograft). At 6 weeks postoperatively, the ulnas were harvested, examined radiographically, and tested mechanically in torsion. The radiographic examination proved to be of little value because some materials were radiodense at the time of implantation. The rates (percentage) of union, torques at failure, and energy to failure values were statistically significantly higher than control for all groups except hydroxylapatite. We concluded that demineralized bone matrix and hydroxylapatite-demineralized bone matrix composite graft compare favorably with cortical replacement (autograft) in mechanical strength and rate of union and therefore may be satisfactory substitutes for bone grafting. Freeze-dried bone did not appear to be as satisfactory because of its low mean energy to failure, but statistical analysis failed to confirm this opinion. Hydroxylapatite graft, when used alone, does not appear to be a suitable material for grafting segmental bone defects.

Animals↗
PubMed2005

The compatibility of ceramic bone graft substitutes as allograft extenders for use in impaction grafting of the femur.

This study investigates the use of porous biphasic ceramics as graft extenders in impaction grafting of the femur during revision hip surgery. Impaction grafting of the femur was performed in four groups of sheep. Group one received pure allograft, group two 50% allograft and 50% BoneSave, group three 50% allograft and 50% BoneSave type 2 and group four 10% allograft and 90% BoneSave as the graft material. Function was assessed using an index of pre- and post-operative peak vertical ground reaction force ratios. Changes in bone mineral density were measured by dual energy X ray absorptiometry (DEXA) scanning. Loosening and subsidence were assessed radiographically and by histological examination of the explanted specimens. There was no statistically significant difference between the four groups after 18 months of unrestricted functional loading for all outcome measures.

Absorptiometry, Photon↗
PubMed2003

Resorbable and nonresorbable hydroxyapatite granules as bone graft substitutes in rabbit cortical defects.

BACKGROUND: The use of various synthetic calcium phosphate compositions for the promotion of bone in bone defects is of potential interest because such materials may be tailor made and may bond to bone. There is yet an inadequate knowledge of the role of calcium phosphate composition and resorbability for the bone response. PURPOSE: The aim of the present study was to compare the ability of resorbable versus nonresorbable hydroxyapatite (HA) granules to promote new bone formation in cortical bone defects. Resorbable and nonresorbable HA granules, used as bone graft substitutes, were evaluated after 6 weeks and 3 months in the rabbit tibia. Circular defects (diameter 5.0 mm) were made in both tibias of 18 New Zealand white rabbits. The 36 defects were divided into three groups (six observations per group and time, respectively). The first group was augmented with resorbable HA granules, the second group was augmented with ceramic nonresorbable HA granules, and the third group was left without augmentation (control). The animals were killed after 6 weeks and 3 months, and the tissue was evaluated with light microscopic (LM) morphology and morphometry, scanning electron microscopy (SEM), and energy dispersive x-ray analysis (EDX). RESULTS: After 3 months LM morphometry revealed significantly more newly formed bone in the two HA augmented groups compared with that in the control. A close contact was found between both kinds of HA granules and new bone as viewed with light microscopy and SEM. A relatively slow degradation process was indicated by the small reduction of the total granule area in the cortical defects. However, LM observations showed a change of granule form. Pilot experiments using SEM-EDX indicate that Ca and P contents had decreased in the resorbable HA granules between 6 weeks and 3 months. Further, a higher content of Ca and P was found in the newly formed bone close to granules, in comparison with more distant newly formed bone. CONCLUSIONS: Our results suggest that both resorbable and nonresorbable HA granules promote new bone formation in rabbit cortical defects, which does not occur in control defects.

Absorbable Implants↗
PubMed1996

Use of arthroscopy and interporous hydroxyapatite as a bone graft substitute in tibial plateau fractures.

Tibial plateau fractures in 17 patients were managed arthroscopically, using interporous hydroxypatite (HA) as a bone graft substitute. Soft-tissue repair and intra-articular lavages were carried out arthroscopically, and depression of the articular surface was done by elevation of the subchondral plate by the bone compactor through a small window under image intensification and filling with HA through the tibial outer rim. Follow-up periods averaged 2 years and 6 months. According to roentgenograms and computed tomograms no development of arthrosis could be found. All of the patients have been followed to fracture union and have returned to their previous activity levels.

Adult↗
PubMed2006

Changes of mineralization of free autogenous bone grafts used for sinus floor elevation.

For augmentations before implant placement in areas of minor bone quantity, autogenous bone is considered the reference to all bone substitutes used alternatively. Autogenous bone transplants originate from various donor areas and can be prepared in different ways before augmentation. They may either be used as block grafts or may be milled to granules that can be used solitarily or in combination with a bone substitute. In a prospective study, 61 patients of the Maxillofacial Surgery Department of our University receiving two-stage sinus floor elevation because of insufficient bone supply were randomly selected. At first-stage surgery, the local augmentation procedure, monocortical probes were obtained on the site of bone harvesting. At second-stage surgery, the implant insertion 6 months after the elevation procedure, bone cores were harvested in the areas of implant placement. Donor regions were the following three areas: the posterior (N=28) and anterior pelvic region (N=15) and the chin region (N=18). The implanted bone in all three groups was particulated to granules of 2-3 mm(2) using a bone mill. All biopsies were analyzed by means of microradiography. The anterior pelvic bone grafts showed a mineralized tissue grade of 35.1+/-7.6% before milling and augmentation. The posterior pelvic bone grafts exhibited a mineralization of 30.7+/-9.5% and the chin bone grafts 74.6+/-8.6%. At second-stage surgery after 6 months, the mineralization was 36.1+/-7.59% in the areas where bone grafts from the anterior pelvic crest were used. Probes harvested from sites with posterior pelvic bone augmentations showed a mineralization rate of 34.5+/-6.5%, and sites were chin bone grafts were applied expressed a mineralization of 54+/-8.6% (P=0.003 compared with the pre-operative value). The comparison of the microradiographical results demonstrated significant differences in the mineralization grades depending on the origin of the graft. The origin of the grafts and their remodeling influenced the mineralization rates found at 6 months. How these data may influence the long-term clinical outcome considering implant survival and bone resorption has to be examined in further long-term studies.

Bone Density↗
PubMed2006

In vitro evaluation of alginate encapsulated adipose-tissue stromal cells for use as injectable bone graft substitute.

This study aims to investigate the survival and osteogenic behavior of murine-derived adipose-tissue stromal cells (ATSCs) encapsulated in alginate microcapsules thereby instigating further studies in this cell delivery strategy for in vivo osteogenesis. Cell viability was quantified using a tetrazolium-based assay and osteogenic differentiation was evaluated by both alkaline-phosphatase (ALP) histochemistry and osteocalcin mRNA analysis. Following microencapsulation, cell numbers increased from 3.9 x 10(3) on day 1 to 7.8 x 10(3) on day 7 and maintained excellent viability in the course of 21-day culture. ALP was 6.9, 5.5, and 3.2 times higher than monolayer cultures on days 7, 14, and 21, respectively. In addition, osteocalcin mRNA was detectable in encapsulated cultures earlier (day 14) than monolayer cultures. We conclude that alginate microcapsules can act as three-dimensional matrix for ATSC proliferation and has potential for use as injectable, biodegradable scaffold in bone tissue engineering.

Adipocytes↗
PubMedDate not supplied

Bone graft substitutes: a comparative qualitative histologic review of current osteoconductive grafting materials.

This paper investigated the osteogenic potential of 6 osteoconductive grafting materials derived from human, bovine, and synthetic sources: HTR, BOP, Biogran, Laddec, Dembone, and Osteograf. Twenty-eight New Zealand rabbits were used in this study. The active group consisted of 24 animals and the control group consisted of 4 animals. The median condyle of each tibia was drilled with a 5-mm-diameter bur to form 8 mm-deep cavities. A control group included 8 osseous cavities, with 1 hole in each tibia. These cavities were washed and left unfilled. In the active group, each grafting material filled 8 osseous cavities in 8 tibiae of different animals. Half of the active and control osseous cavities were investigated with decalcified hematoxylin and eosin-stained sections. The other half were studied with scanning electron microscopy. It was concluded that Laddec bovine bone granules possessed the best potential for an osteoconductive grafting material, followed by the bioglass crystals of Biogran and the hydroxyapatite particles of Osteograf, respectively. The least potential for rapid bone formation was demonstrated by the copolymers of HTR and BOP, and Dembone allograft bone particles did not reveal active bone healing.

Animals↗