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PubMed2000

Natural coral as bone-defect-filling material.

Natural coral (NC) has been studied experimentally and clinically as a bone substitute, but its resorption rate and possible replacement by bone still need to be defined in humans. In this study bicortical bone was harvested from the iliac crest of 10 patients. The defect was filled with a NC block, and changes were monitored by X-rays and quantitative CT scans for a mean of 2.1 years. A biopsy was taken at 1 year. The purpose of the study was to investigate the resorption rate and pattern of NC (Porites) implants and the replacement, if any, of the implant by new bone. The blocks underwent centripetal resorption, but all the blocks still could be detected by X-rays and CT scans at the end of the follow-up period. The density of the remaining block did not change. Seven of the 10 implants were smaller than 50% of their original size at the end of the study. Bone ingrowth could be observed only in two of seven biopsies. One implant had to be removed after 1.7 years due to infection. The study shows that resorption of natural coral proceeds centripetally and apparently more rapidly when accompanied by tissue ingrowth. None of the blocks resorbed completely, and the defect at the iliac crest had not been restored by the end of the study.

Adolescent↗
PubMed2005

Formation of bone-like apatite on organic polymers treated with a silane-coupling agent and a titania solution.

Polyethylene terephthalate (PET), ethylene-vinyl alcohol copolymer (EVOH) and Nylon 6 in plate form were treated with silane-coupling agents, a titanium alkoxide-alcohol solution and a hot HCl solution to form a thin crystalline titanium oxide layer. When placed in a simulated body fluid with ion concentrations nearly equal to those of the human blood plasma, nanosized bone-like apatite formed uniformly on the surfaces of these treated polymers: within 2 days for PET and Nylon 6, and 7 days for EVOH. This indicates that such titania-modified polymers might form bone-like apatite in the living body, and bond to living bone through this apatite layer. Three-dimensional fabrics of these polymer fibers, with open spaces in various sizes, are expected to be useful as bone substitutes, as they will be integrated with the natural bone.

Apatites↗
PubMed2005

Mathematical modelling of the distribution of newly formed bone in bone tissue engineering.

New bone formation in bone substitutes is usually investigated by histomorphometric global analysis. This study provides a novel mathematical modelling approach of new bone formation in the use of osteoinductive and functionalized biomaterials for bone tissue engineering. We discuss here the repartition and the probability to get new bone formation inside Biphasic Calcium Phosphate (BCP) loaded with autologous osteogenic cells, functionalized with a cyclo RGD peptide, after implantation in rabbits for 2 and 4 weeks. This local analysis allowed us to complement classical global findings and to demonstrate that after 2 weeks of implantation, the probability of new bone formation was significantly higher in RGD-grafted BCP and that new formed bone was largely distributed from the edge to the centre of the implant. While no significant differences were obtained after 4 weeks of implantation between RGD-grafted and non-grafted materials, distribution of new bone formation inside RGD-grafted materials was significantly more homogeneous as demonstrated by our mathematical modelling approach. In conclusion, local analysis of new bone formation inside macroporous substitutes coupled with mathematical modelling constitutes a potential quantitative approach for the evaluation of the osteoconductive and osteoinductive characteristics of such biomaterials.

Algorithms↗
PubMedDate not supplied

Maxillary sinus augmentation with the xenograft Bio-Oss and autogenous intraoral bone for qualitative improvement of the implant site: a histologic and histomorphometric clinical study in humans.

The aim of the present clinical study was to determine, through histologic and histomorphometric investigations of human bone specimens, whether the addition of autogenous bone to the bone substitute material Bio-Oss can produce a high-quality implant site. To improve vertical bone height, 13 sinus floor elevations were carried out in a total of 12 patients. Augmentation of the maxillary sinus floor was completed using a mixture of Bio-Oss and bone harvested intraorally from the mandibular symphysis, the retromolar space, or the tuberosity region. Following an average of 7.1 months of healing, 36 Brånemark System implants were placed. During this surgical intervention, 23 cylinder-shaped bone biopsies were taken from the augmented maxillary region using trephine burs. Histologic analysis of the bone biopsies revealed that the Bio-Oss granulate was well-integrated into the newly formed bone; 33.1% (+/- 12.4%) of the substitute material surface was in direct contact with bone. Histomorphometric analysis of the samples revealed an average percentage proportion of bone of 18.9% (+/- 6.4%). The bovine substitute material and soft tissue occupied, respectively, 29.6% (+/- 8.9%) and 51.5% (+/- 9.4%) of the measured surface. When the implants were uncovered after an average healing phase of 6 months, all 36 implants had become osseointegrated. The combination of osteoconductive Bio-Oss and osteoinductive autogenous bone thus proved to be a material suitable for application in sinus floor augmentation.

Adult↗
PubMed1997

Application of the low vacuum scanning electron microscope to the study of biomaterials and mammalian cells.

The use of the scanning electron microscope (SEM) in 'low' (reduced) vacuum (lvac) mode permits observation of specimens which have not been coated with a conductive material such as gold or carbon. We have evaluated the use of this mode of observation to the study of biomaterials using the bone-substitute material Interpore as an example. On this material, rat bone cells were visible in lvac mode only in cells traversing pores, when they were readily identified by their cell nuclei. Rat calvarial bone examined uncoated in lvac mode showed the bone structure clearly through the overlying layer of osteoblast cells, which were subsequently revealed by gold coating. Immunogold labelling of alkaline phosphatase was imaged in lvac mode, following silver enhancement and carbon coating. These studies demonstrate the complementary use of the lvac and high vacuum (hvac) SEM to study material composition, the behaviour of mammalian cells on biomaterials and the potential use of lvac SEM to study mineralized tissues without removal of overlying soft tissue.

Alkaline Phosphatase↗
PubMed2005

Bone reconstruction: from bioceramics to tissue engineering.

Over the past 30 years, an enormous array of biomaterials proposed as ideal scaffolds for cell growth have emerged, yet few have demonstrated clinical efficacy. Biomaterials, regardless of whether they are permanent or biodegradable, naturally occurring or synthetic, need to be biocompatible, ideally osteoinductive, osteoconductive, integrative, porous and mechanically compatible with native bone to fulfill their desired role in bone tissue engineering. These materials provide cell anchorage sites, mechanical stability and structural guidance and in vivo, provide the interface to respond to physiologic and biologic changes as well as to remodel the extracellular matrix in order to integrate with the surrounding native tissue. Calcium phosphate ceramics and bioactive glasses were introduced more than 30 years ago as bone substitutes. These materials are considered bioactive as they bond to bone and enhance bone tissue formation. The bioactivity property has been attributed to the similarity between the surface composition and structure of bioactive materials, and the mineral phase of bone. The drawback in using bioactive glasses and calcium phosphate ceramics is that close proximity to the host bone is necessary to achieve osteoconduction. Even when this is achieved, new bone growth is often strictly limited because these materials are not osteoinductive in nature. Bone has a vast capacity for regeneration from cells with stem cell characteristics. Moreover, a number of different growth factors including bone morphogenetic proteins, have been demonstrated to stimulate bone growth, collagen synthesis and fracture repair both in vitro and in vivo. Attempts to develop a tissue-engineering scaffold with both osteoconductivity and osteoinductivity have included loading osteoinductive proteins and/or osteogenic cells on the traditional bioactive materials. Yet issues that must be considered for the effective application of bioceramics in the field of tissue engineering are the degree of bioresorption and the poor mechanical strength. The synthesis of a new generation of biomaterials that can specifically serve as tissue engineering scaffolds for drug and cell delivery is needed. Nanotechnology can provide an alternative way of processing porous bioceramics with high mechanical strength and enhanced bioactivity and resorbability.

Bone Diseases↗
PubMed2006

[Research development and prospect of calcium phosphate biomaterials with intrinsic osteoinductivity].

Calcium phosphates ceramics are frequently used as bone substitute materials in clinics because they are similar to the bone in mineral phase, they are of no antigenicity, and they have good biocompatibility as well as excellent osteoconductivity. The question as to whether calcium phosphate biomaterials possess osteoinductivity has been debated for a long time. Up to now, extensive fundamental studies and clinical application have demonstrated that calcium phosphate ceramics with special structure may induce bone formation in soft tissue. In this paper are reviewed the discovery and confirmation of calcium phosphates ceramics with intrinsic osteoinductivity, the process and mechanism of osteoinduction, and the relationship between osteoinductivity of calcium phosphate materials and animal species, the mesenchymal stem cells related to osteoinduction, the application of osteoinductive biomaterials. The researches directed toward to the osteoinduction of calcium phosphate are prospected.

Biocompatible Materials↗
PubMed2000

Adsorption and release of insulin-like growth factor-I on porous tricalcium phosphate implant.

In order to develop bone substitutes, the design of biomaterials like calcium phosphate ceramic loaded with bone growth factor are of great interest. However, it is necessary to control the amount of growth factor adsorbed onto ceramics and the kinetics of its release. Radiolabeling of insulin-like growth factor-I (IGF-I) with 125-iodine ([(125)I]-IGF-I) and its adsorption onto porous tricalcium phosphate (TCP) cylinders enabled us to establish the time-adsorption and time-release curves using various concentrations of IGF-I. The adsorption curve increased rapidly and then flattened out at 72 h; 90% of the maximum was already reached at 24 h; and 20% of the adsorbed IGF-I was released in water within 4 days. In human serum the release was faster at 82% within 4 days. In vivo evaluation on an animal model was then performed. Rabbits' bilateral femoral cylindrical bone defects were filled with the TCP cylinders, which were either carrying IGF-I or implanted alone as a control in each rabbit. Bone turnover and ceramic resorption were stimulated by IGF-I loaded TCP according to standard radiography, dual-energy X-ray absorptiometry, histology, and histomorphometry.

Adsorption↗
PubMed2001

Transforming growth factor-beta1 incorporated in calcium phosphate cement stimulates osteotransductivity in rat calvarial bone defects.

Bone regeneration of the alveolar crest around dental implants is an important factor in the success of implant use. Calcium phosphate cement can be used as a bone substitute and applied clinically as a paste to fill micro- and macroscopic bone defects. We have shown earlier that the intermixing of the recombinant human transforming growth factor-beta1 (rhTGF-beta1) in hardening calcium phosphate cement stimulated osteoblastic differentiation of rat primary bone cells in vitro. The aim of the present study was to examine whether the similar enrichment with rhTGF-beta1 affects the replacement of calcium phosphate cement by bone (osteotransduction) in calvarial critical size defects (csd) of adult rats. Two bone defects of 5 mm diameter were created bilaterally in each skull of 10 adult male rats. Both defects were filled with 53 mg of calcium phosphate cement without rhTGF-beta1 (control) at one side, and with 10 or 20 ng rhTGF-beta1 at the other side. After 8 weeks, defects with surrounding skull were analysed histologically and histomorphometrically. The addition of rhTGF-beta1 in the cement increased the amount of bone in rat skull defects. This finding coincidences with our in vitro observations, that intermixing of rhTGF-beta1 in calcium phosphate cement stimulates bone cell differentiation. Addition of rhTGF-beta1 stimulated bone formation as indicated by an increased bone volume of 50% and an increased bone/cement contact of 65%, in comparison to control defects with cement without rhTGF-beta1. In addition, rhTGF-beta1 reduced the remaining volume of cement, by 11% at 10 ng rhTGF-beta1, and by 20% at 20 ng rhTGF-beta1 in the cement. Defect closure was not affected. We conclude that the intermixing of rhTGF-beta1 in a fast-setting calcium phosphate cement stimulates bone growth and the osteotransduction of the cement. For bone regeneration procedures around endosseous implants, calcium phosphate cement with rhTGF-beta1 might be an appropriate combination for early osseointegration and implant use.

Animals↗
PubMedDate not supplied

Biodegradable ceramic-collagen composite implanted in rabbit tibiae.

To develop an artificial bone substitute that would be gradually degraded and replaced by the regenerating natural bone, a carbonate apatite type I atelocollagen (82/12 in v/v%) composite was designed. The carbonate apatite synthesized at 58 degrees C demonstrated a crystallinity similar to that of natural bone. Type I atelocollagen was purified from human umbilical cords. Carbonate apatite-atelocollagen composite rods (diameter 6 mm x height 10 mm) were irradiated by ultraviolet ray (wave length 254 nm) for 4 hr to increase the collagen fibrillar cross links. Rabbit tibiae were dissected to prepare an artificial total bone defect (length 10 mm). The composites and porous hydroxyapatite rods, sintered at 1200 degrees C, were implanted into the defects and the tibiae were fixed by external osseofixators. The implanted composites were gradually degraded in the lesions, and the regenerated bone totally replaced the defects within 6 weeks, while the hydroxyapatite rod implanted lesions were not replaced by bone. No specific histologic abnormalities appeared in either the hydroxyapatite or composite rod implanted lesions.

Animals↗
PubMed2005

Bone graft extenders, substitutes, and osteogenic proteins.

A number of products that serve as a bone graft substitutes or graft extenders are currently available. Osteoconductive products provide a porous 3-dimensional structure that encourages bone ingrowth. These materials are readily resorbed by osteoclasts leading to turnover into host bone at variable rates. Some calcium phosphate products act as cements in that they are liquid upon preparation and harden at body temperature. These cements resist compressive forces but are not effective in resisting shear or torsion. Calcium sulfate resorbs more quickly than calcium phosphate and has the potential to serve as a carrier for drugs or growth factors. Preclinical studies have shown that the osteoinductive capacity of autograft and allograft bone can be improved substantially with the addition of osteogenic proteins. Although no detailed clinical studies have been reported to date, anecdotal reports of their use with and without bone graft indicate results consistent with those obtained in preclinical studies.

Bone Cements↗
PubMed2000

Neo-osseous flaps using demineralized allogeneic bone in a rat model.

Surgical reconstruction with revascularized bone grafts can be compromised by donor tissue limitations and may be refined by prefabrication of compound neoflaps using bone substitutes. The principal suitability of demineralized allogeneic bone (DALB) slabs in fabricating neo-osseous flaps based on the inferior epigastric vascular system was studied and compared with neoflaps with autologous bone (AUB). In 45 rats, the histological pattern of bone formation in response to angiogenesis induced by vessel implantation was assessed, and characteristics of vascularization of the neoflap were studied microangiographically at 2, 4, 6, and 8 weeks. Histological techniques included decalcified and nondecalcified sections, as well as intravital polyfluorochrome labeling. Blood flow of the neoflap was also assessed quantitatively using 15-microm microspheres labeled with technetium 99-methylene diphosphate (99-MDP) 8 weeks after flap fabrication. Although the DALB neoflaps showed consistent bone formation and neovascularization, the bone regeneration process was delayed distinctly in comparison with AUB. Microangiographically, however, no differences between the two types of grafts became apparent during all time periods tested. Furthermore, the radioactivity of the DALB neoflap, which means bone blood flow per dry weight, was significantly higher than in AUB grafts and even more than that of intact iliac bone (p = 0.001). The exact meaning of elevated blood flow in DALB and similar degrees of vascularization corresponding to native AUB grafts remains to be determined, but may be a sign of ongoing bone formation resulting in a suitable DALB-containing neo-osseous flap in the long term. The authors findings support that allogeneic bone could be a potential substitute for AUB in creating a prefabricated neo-osseous flap.

Angiography↗
PubMed2002

An X-ray diffraction study of the effects of heat treatment on bone mineral microstructure.

A series of human cortical bone specimens has been heated to temperatures up to 1200 degrees C and the mineral content examined in detail by X-ray diffraction. Line profile analysis of the diffraction data has been undertaken to characterise the microstructural (crystallite size and microstrain) features of the mineral at each temperature. Individual profile fitting of several maxima from each diffractogram has also provided precise lattice parameters of the apatite at each temperature. The apatite did not show any significant decomposition over the temperature range although CaO was increasingly formed at temperatures above 600 degrees C. Both finite crystallite size and microstrain contributed significantly to the diffraction peak broadening below 600 degrees C. When heated to > 800 degrees C, the small, rod-like mineral crystallites changed from a highly anisotropically strained state to one with significantly larger equidimensional crystals possessing little microstrain. The findings are discussed in the context of graft bone substitutes and surgical heating of bone.

Adult↗
PubMed2000

Histologic and mechanical evaluation of impacted morcellized cancellous allografts in rabbits: comparison with hydroxyapatite granules.

The bioactivity and mechanical properties of morcellized allografts and hydroxyapatite (HA) granules were evaluated in a rabbit model. Allografts were replaced by viable trabecular structures within 8 weeks. The yield strength and stiffness of allografts were within normal cancellous bone levels by 3 weeks and were maintained afterward. The amount of newly formed bone around HA granules was comparable to that around allografts. The yield strength and stiffness of HA granules were significantly higher than those of allografts at 3 and 12 weeks. Allografts offer the advantage of being replaced by host-bone without significant deterioration in mechanical properties over the course of remodeling. HA granules can also be used for a bone substitute given their bioactivity in bone conduction and superiority in mechanical properties to allografts.

Animals↗
PubMed2001

Overview: animal models of osteopenia and osteoporosis.

Prior to initiating a clinical trial in a post-menopausal osteoporosis study, it is reasonable to recommence the evaluation of treatment in the 9-month-old ovariectomized female rat. A female rat of this age has reached peak bone mass and can be manipulated to simulate clinical findings of post-menopausal osteoporosis. Ample time exists for experimental protocols that either prevent estrogen depletion osteopenia or restore bone loss after estrogen depletion. More time can be saved by acceleration of the development of the osteopenia by combining ovariectomized (OVX) plus immobilization (IM) models. Methods like serum biochemistry, histomorphometry and densitometry used in humans are applicable in rats. Like most animal models of osteopenia, the rat develops no fragility fractures, but mechanical testing of rat bones substitutes as a predictor of bone fragility. Recent studies have shown that the prevailing activity in cancellous and cortical bone of the sampling sites in rats is remodeling. The problems of dealing with a growing skeleton, the site specificity of the OVX and IM models, the lack of trabecular and Haversian remodeling and the slow developing cortical bone loss have been and can be overcome by adding beginning and pre-treatment controls and muscle mass measurements in all experimental designs, selecting cancellous bone sampling sites that are remodeling, concentrating the analysis of cortical bone loss to the peri-medullary bone and combining OVX and IM in a model to accelerate the development of both cancellous and cortical bone osteopenia. Not to be forgotten is the distal tibia site, an adult bone site with growth plate closure at 3 months and low trabecular bone turnover and architecture similar to human spongiosa. This site would be most challenging to the action of bone anabolic agents. Data about estrogen-deplete mice are encouraging, but the ovariectomized rat model suggests that developing an ovariectomized mouse model as an alternative is not urgent. Nevertheless, the mouse model has a place in drug development and skeletal research. In dealing with drug development, it could be a useful model because it is a much smaller animal requiring fewer drugs for screening. In skeletal research mice are useful in revealing genetic markers for peak bone mass and gene manipulations that affect bone mass, structure and strength. When the exciting mouse glucocorticoid-induced bone loss model of Weinstein and Manolagas is confirmed by others, it could be a significant breakthrough for that area of research. Lastly, we find that the information generated from skeletal studies of nonhuman primates has been most disappointing and recommend that these expensive skeletal studies be curtailed unless it is required by a regulatory agency for safety studies.

Journal Article↗
PubMed1997

[Experimental study on porous hydroxyapatite ceramics in repair of skull bone defect of rabbit].

In order to investigate the possibility of porous hydroxyapatite ceramics (HAC) in the repair of skull bone defect, twenty-four rabbits were used. The bone defect model was created by operation to obtain a defect in parietal bone in a size of 1 cm x 1 cm. Filled the defect with HAC and methyl-methacrylate-syrene copolymer (MMAS) to fill the defect as control. At 1st, 2nd and 3rd months after operation, behavior of the rabbits was observed and then these animals were sacrificed and specimens were examined under microscope. Results showed as follows: after operation, behavior of all animals were normal. By histological examination, it was found that in HAC group, there were granulation tissue, fibrous tissue and newly formed vessels grew into the pores and the osteoblasts formed osseous trabeculae. There was no inflammatory cell infiltration. In the MMAS grafted asea, there was formation of fibrous membrane. It suggested that HAC might be a good material for bone substitute in repair of skull bone defect.

Animals↗
PubMed2006

Osteopromotion by a beta-tricalcium phosphate/bone marrow hybrid implant for use in spine surgery.

STUDY DESIGN: Experimental animal study. OBJECTIVE.: Evaluate osteopromotive properties of a beta-tricalcium phosphate (TCP) implant with different osteogenic substances in an animal study. SUMMARY OF BACKGROUND DATA: Current research in spine surgery is focusing on resorbable bone implants because of the high morbidity after iliac crest graft harvesting. Therefore, several osteoconductive scaffolds are combined with osteoinductive substances. METHODS: In 14 sheep, a critical size defect was performed on both tibiae. The sheep were randomized into 3 groups (4 sheep each) and a control group (2 sheep). In the treatment groups, the defects were filled with the beta-TCP scaffold impregnated with either venous blood, bone marrow from sternal aspiration, or a concentrated mononuclear cell suspension derived from sternal bone marrow aspiration. The sheep in each group were euthanized 6 and 12 weeks after the operation; the investigation included quantitative computerized tomography and histology. RESULTS: The best bone formation occurred in the bone marrow group after 6 and 12 weeks, whereas no difference was found between the cell and venous blood groups. Only the bone marrow group showed bone formation inside the scaffold after 6 weeks. We conclude that a beta-TCP scaffold filled with bone marrow aspiration creates a biologic resorbable bone substitute with high osteopromoting capacity. Surprisingly, no better bone formation occurred in the concentrated cells group, which may be a result of technical reasons and needs to be further evaluated. CONCLUSIONS: The combination of beta-TCP and bone marrow has superior osteopromotive properties to venous blood or concentrated mononuclear cells and can be used effectively as a substitute to iliac crest graft.

Animals↗
PubMed1997

[Experimental study of artificial bone composite with high biological induction in repairing bone defect].

On the basis of the animal model of segmental ultra defects in rabbits, two different composite artificial bones (HA-bBMP-Co and HA-Co) were first used to repair the segmental bone defect respectively in 12 rabbits. The results of X-ray, gross, stereomicroscopic and histological examination were found that HA-bBMP-Co was much faster and much better than HA-Co, involving induction of new bone formation in quality and quantity. It is suggested that there is a widespread prospect in use of HA-bBMP-Co as a bone substitute material.

Animals↗