909 resultados para GRAFT SUBSTITUTES


Relevância:

60.00% 60.00%

Publicador:

Resumo:

A bioactive and bioresorbable scaffold fabricated from medical grade poly (epsilon-caprolactone) and incorporating 20% beta-tricalcium phosphate (mPCL–TCP) was recently developed for bone regeneration at load bearing sites. In the present study, we aimed to evaluate bone ingrowth into mPCL–TCP in a large animal model of lumbar interbody fusion. Six pigs underwent a 2-level (L3/4; L5/6) anterior lumbar interbody fusion (ALIF) implanted with mPCL–TCP þ 0.6 mg rhBMP-2 as treatment group while four other pigs implanted with autogenous bone graft served as control. Computed tomographic scanning and histology revealed complete defect bridging in all (100%) specimen from the treatment group as early as 3 months. Histological evidence of continuing bone remodeling and maturation was observed at 6 months. In the control group, only partial bridging was observed at 3 months and only 50% of segments in this group showed complete defect bridging at 6 months. Furthermore, 25% of segments in the control group showed evidence of graft fracture, resorption and pseudoarthrosis. In contrast, no evidence of graft fractures, pseudoarthrosis or foreign body reaction was observed in the treatment group. These results reveal that mPCL–TCP scaffolds could act as bone graft substitutes by providing a suitable environment for bone regeneration in a dynamic load bearing setting such as in a porcine model of interbody spine fusion.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Adolescent idiopathic scoliosis is a complex three dimensional deformity affecting 2-3% of the general population. Resulting spine deformities include progressive coronal curvature, hypokyphosis, or frank lordosis in the thoracic spine and vertebral rotation in the axial plane with posterior elements turned into the curve concavity. The potential for curve progression is heightened during the adolescent growth spurt. Success of scoliosis deformity correction depends on solid bony fusion between adjacent vertebrae after the intervertebral discs have been surgically cleared and the disc spaces filled with graft material. Problems with bone graft harvest site morbidity as well as limited bone availability have led to the search for bone graft substitutes. Recently, a bioactive and resorbable scaffold fabricated from medical grade polycaprolactone (PCL) has been developed for bone regeneration at load bearing sites. Combined with recombinant human bone morphogenic protein–2 (rhBMP-2), this has been shown to be successful in acting as a bone graft substitute in acting as a bone graft substitute in a porcine lumbar interbody fusion model when compared to autologous bone graft. This in vivo sheep study intends to evaluate the suitability of a custom designed medical grade PCL scaffold in combination with rhBMP-2 as a bone graft substitute in the setting of mini–thoracotomy surgery as a platform for ongoing research to benefit patients with adolescent idiopathic scoliosis.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Bioceramics play an important role in repairing and regenerating bone defects. Annually, more than 500,000 bone graft procedures are performed in the United states and approximately 2.2 million are conducted worldwide. The estimated cost of these procedures approaches $2.5billion per year. Around 60% of the bone graft substitutes available on the market involve bioceramics. It is reported that bioceramics in the world market increase by 9% per year. For this reason, the research of bioceramics has been one of the most active areas during, the past several years. Considering the significant importance of bioceramics, our goal was to compile this book to review the latest research advances in the field of bioceramics. The text also summarizes our work during the past 10 years in an effort to share innovative concepts, design of bioceramisc, and methods for material synthesis and drug delivery. We anticipate that this text will provide some useful information and guidance in the bioceramics field for biomedical engineering researchers and material scientists. Information on novel mesoporous bioactive glasses and silicate-based ceramics for bone regeneration and drug delivery are presented. Mesoporous bioactive glasses have shown multifunctional characteristics of bone regeneration and drug delivery due to their special mesopore structures,whereas silicated-based bioceramics, as typical third-generation biomaterials,possess significant osteostimulation properties. Silica nanospheres with a core-shell structure and specific properties for controllable drug delivery have been carefully reviewed-a variety of advanced synthetic strategies have been developed to construct functional mesoporous silica nanoparticles with a core-shell structure, including hollow, magnetic, or luminescent, and other multifunctional core-shell mesoporous silica nanoparticles. In addition, multifunctional drug delivery systems based on these nanoparticles have been designed and optimized to deliver the drugs into the targeted organs or cells,with a controllable release fashioned by virtue of various internal and external triggers. The novel 3D-printing technique to prepare advanced bioceramic scaffolds for bone tissue engineering applications has been highlighted, including the preparation, mechanical strength, and biological properties of 3D-printed porous scaffolds of calcium phosphate cement and silicate bioceramics. Three-dimensional printing techniques offer improved large-pore structure and mechanical strength. In addition , biomimetic preparation and controllable crystal growth as well as biomineralization of bioceramics are summarized, showing the latest research progress in this area. Finally, inorganic and organic composite materials are reviewed for bone regeneration and gene delivery. Bioactive inorganic and organic composite materials offer unique biological, electrical, and mechanical properties for designing excellent bone regeneration or gene delivery systems. It is our sincere hope that this book will updated the reader as to the research progress of bioceramics and their applications in bone repair and regeneration. It will be the best reward to all the contributors of this book if their efforts herein in some way help reader in any part of their study, research, and career development.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Polycaprolactone (PCL) is a resorbable polymer used extensively in bone tissue engineering owing to good structural properties and processability. Strontium substituted bioactive glass (SrBG) has the ability to promote osteogenesis and may be incorporated into scaffolds intended for bone repair. Here we describe for the first time, the development of a PCL-SrBG composite scaffold incorporating 10% (weight) of SrBG particles into PCL bulk, produced by the technique of melt-electrospinning. We show that we are able to reproducibly manufacture composite scaffolds with an interconnected porous structure and, furthermore, these scaffolds were demonstrated to be non-cytotoxic in vitro. Ions present in the SrBG component were shown to dissolve into cell culture media and promoted precipitation of a calcium phosphate layer on the scaffold surface which in turn led to noticeably enhanced alkaline phosphatase activity in MC3T3-E1 cells compared to PLC-only scaffolds. These results suggest that melt-electrospun PCL-SrBG composite scaffolds show potential to become effective bone graft substitutes.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Injured bone initiates the healing process by forming a blood clot at the damaged site. However, in severe damage, synthetic bone implants are used to provide structural integrity and restore the healing process. The implant unavoidably comes into direct contact with whole blood, leading to a blood clot formation on its surface. Despite this, most research in bone tissue engineering virtually ignores the important role of a blood clot in supporting healing. Surface chemistry of a biomaterial is a crucial property in mediating blood-biomaterials interactions, and hence the formation of the resultant blood clot. Surfaces presenting mixtures of functional groups carboxyl (–COOH) and methyl (–CH3) have been shown to enhance platelet response and coagulation activation, leading to the formation of fibrin fibres. In addition, it has been shown that varying the compositions of these functional groups and the length of alkyl groups further modulate the immune complement response. In this study, we hypothesised that a biomaterial surface with mixture of –COOH/–CH3(methyl), –CH2CH3 (ethyl) or –(CH2)3CH3 (butyl) groups at different ratios would modulate blood coagulation and complement activation, and eventually tailor the structural and functional properties of the blood clot formed on the surface, which subsequently impacts new bone formation. Firstly, we synthesised a series of materials composed of acrylic acid (AA), and methyl (MMA), ethyl (EMA) or butyl methacrylates (BMA) at different ratios and coated on the inner surfaces of incubation vials. Our surface analysis showed that the amount of –COOH groups on the surface coatings was lower than the ratios of AA prepared in the materials even though the surface content of –COOH groups increased with increasing in AA ratios. It was indicated that the surface hydrophobicity increased with increasing alkyl chain length: –CH 3 > –CH2CH3 > –(CH2)3CH3, and decreased with increasing –COOH groups. No significant differences in surface hydrophobicity was found on surfaces with –CH3 and –CH2CH3 groups in the presence of –COOH groups. The material coating was as smooth as uncoated glass and without any major flaws. The average roughness of material-coated surface (3.99 ± 0.54 nm) was slightly higher than that of uncoated glass surface (2.22 ± 0.29 nm). However, no significant differences in surface average roughness was found among surfaces with the same functionalities at different –COOH ratios nor among surfaces with different alkyl groups but the same –COOH ratios. These suggested that the surface functional groups and their compositions had a combined effect on modulating surface hydrophobicity but not surface roughness. The second part of our study was to investigate the effect of surface functional groups and their compositions on blood cascade activation and structural properties of the formed clots. It was found that surfaces with –COOH/–(CH2)3CH3 induced a faster coagulation activation than those with –COOH/–CH3 and –CH2CH3, regardless of the –COOH ratios. An increase in –COOH ratios on –COOH/–CH3 and –CH2CH3 surfaces decreased the rate of activation. Moreover, all material-coated surfaces markedly reduced the complement activation compared to uncoated glass surfaces, and the pattern of complement activation was entirely similar to that of surface-induced coagulation, suggesting there is an interaction between two cascades. The clots formed on material-coated surfaces had thicker fibrin with a tighter network at the exterior when compared to uncoated glass surfaces. Compared to the clot exteriors, thicker fibrins with a loose network were found in clot interiors. Coated surfaces resulted in more rigid clots with a significantly slower fibrinolysis after 1 h of lysis when compared to uncoated glass surfaces. Significant differences in fibrinolysis after 1 h of lysis among clots on material-coated surfaces correlated well with the differences in fibrin thickness and density at clot exterior. In addition, more growth factors were released during clot formation than during clot lysis. From an intact clot, there was a correlation between the amount of PDGF-AB release and fibrin density. Highest amount of PDGF-AB was released from clots formed on surfaces with 40% –COOH/60% –CH 3 (i.e. 65MMA). During clot lysis, the release of PDGF-AB also correlated with the fibrinolytic rate while the release of TGF-â1 was influenced by the fibrin thickness. This suggested that different clot structures led to different release profiles of growth factors in clot intact and degrading stages. We further validated whether the clots formed on material-coatings provide the microenvironment for improved bone healing by using a rabbit femoral defect model. In this pilot study, the implantation of clots formed on 65MMA coatings significantly increased new bone formation with enhanced chondrogenesis, osteoblasts activity and vascularisation, but decreased inflammatory macrophage number at the defects after 4 weeks when compared to commercial bone grafts ChronOSTM â-TCP granules. Empty defects were observed when blood clot formation was inhibited. In summary, our study demonstrated that surface functional groups and their relative ratios on material coatings synergistically modulate activation of blood cascades, resultant fibrin architecture, rigidity, susceptibility to fibrinolysis as well as growth factor release of the formed clots, which ultimately alter the healing microenvironment of injured bones.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

The transplantation of autologous bone graft as a treatment for large bone defects has the limitation of harvesting co-morbidity and limited availability. This drives the orthopaedic research community to develop bone graft substitutes. Routinely, supra-physiological doses of bone morphogenetic proteins (BMPs) are applied perpetuating concerns over undesired side effects and cost of BMPs. We therefore aimed to design a composite scaffold that allows maintenance of protein bioactivity and enhances growth factor retention at the implantation site. Critical-sized defects in sheep tibiae were treated with the autograft and with two dosages of rhBMP-7, 3.5 mg and 1.75 mg, embedded in a slowly degradable medical grade poly(ε-caprolactone) (PCL) scaffold with β-tricalcium phosphate microparticles (mPCL-TCP). Specimens were characterised by biomechanical testing, microcomputed tomography and histology. Bridging was observed within 3 months for the autograft and both rhBMP-7 treatments. No significant difference was observed between the low and high rhBMP-7 dosages or between any of the rhBMP-7 groups and autograft implantation. Scaffolds alone did not induce comparable levels of bone formation compared to the autograft and rhBMP-7 groups. In summary, the mPCL-TCP scaffold with the lower rhBMP-7 dose led to equivalent results to autograft transplantation or the high BMP dosage. Our data suggest a promising clinical future for BMP application in scaffold-based bone tissue engineering, lowering and optimising the amount of required BMP.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

The increasing interest in coral culture for biotechnological applications, to supply the marine aquarium trade, or for reef restoration programs, has prompted researchers to optimize coral culture protocols, with emphasis to ex situ production. When cultured ex situ, the growth performance of corals can be influenced by several physical, chemical and biological parameters. For corals harbouring zooxanthellae, light is one of such key factors, as it can influence the photosynthetic performance of these endosymbionts, as well as coral physiology, survival and growth. The economic feasibility of ex situ coral aquaculture is strongly dependent on production costs, namely those associated with the energetic needs directly resulting from the use of artificial lighting systems. In the present study we developed a versatile modular culture system for experimental coral production ex situ, assembled solely using materials and equipment readily available from suppliers all over the world; this approach allows researchers from different institutions to perform truly replicated experimental set-ups, with the possibility to directly compare experimental results. Afterwards, we aimed to evaluate the effect of contrasting Photosynthetically Active Radiation (PAR) levels, and light spectra emission on zooxanthellae photochemical performance, through the evaluation of the maximum quantum yield of PSII (Fv/Fm) (monitored non-invasively and non-destructively through Pulse Amplitude Modulation fluorometry, PAM), chlorophyll a content (also determined non-destructively by using the spectral reflectance index Normalized Difference Vegetation Index, NDVI), photosynthetic and accessory pigments, number of zooxanthellae, coral survival and growth. We studied two soft coral species, Sarcophyton cf. glaucum and Sinularia flexibilis, as they are good representatives of two of the most specious genera in family Alcyoniidae, which include several species with interest for biotechnological applications, as well as for the marine aquarium trade; we also studied two commercially important scleractinian corals: Acropora formosa and Stylophora pistillata. We used different light sources: hydrargyrum quartz iodide (HQI) lamps with different light color temperatures, T5 fluorescent lamps, Light Emitting Plasma (LEP) and Light Emitting Diode (LED). The results achieved revealed that keeping S. flexibilis fragments under the same light conditions as their mother colonies seems to be photobiologically acceptable for a short-term husbandry, notwithstanding the fact that they can be successfully stocked at lower PAR intensities. We also proved that low PAR intensities are suitable to support the ex situ culture S. cf. glaucum in captivity at lower production costs, since the survival recorded during the experiment was 100%, the physiological wellness of coral fragments was evidenced, and we did not detect significant differences in coral growth. Finally, we concluded that blue light sources, such as LED lighting, allow a higher growth for A. formosa and S. pistillata, and promote significant differences on microstructure organization and macrostructure morphometry in coral skeletons; these findings may have potential applications as bone graft substitutes for veterinary and/or other medical uses. Thus, LED technology seems to be a promising option for scleractinian corals aquaculture ex situ.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Autogenous bone grafts are considered to be the gold standard in bone regeneration because of their osteogenic activity; however, due to limited availability of intraoral donor sites and the need to resolve the demands of patients requires an alternative to these. Two male patients were submitted to implant surgery in two stages with 6 months intervals between each of them: the first was exodontia and placement of DBM graft into the socket; the second stage was the drill with a 2 mm internal diameter trephine in center of the alveolar ridge previously grafted with DBM and subsequent implant placement. The samples were analyzed under histological techniques. A very mature bone was observed at 6 months after DBM graft placement in the sockets, showing it to be a good alternative as bone graft.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

The use of scaffolds for Tissue Engineering (TE) is increasing due to their efficacy in helping the body rebuild damaged or diseased tissue. Hydroxyapatite (HA) is the most suitable bioactive ceramic to be used in orthopaedic reconstruction since it replicates the mineral component of the hard tissues, and it has therefore excellent biocompatibility properties. The temporal and spatial control of the tissue regeneration process is the limit to be overcome in order to treat large bone and osteochondral defects. In this thesis we describe the realization of a magnetic scaffolds able to attract and take up growth factors or other bio-agents in vivo via a driving magnetic force. This concept involves the use of magnetic nanoparticles (MNP) functionalized with selected growth factors or stem cells. These functionalized MNP act as shuttles transporting the bio-agents towards and inside the scaffold under the effect of the magnetic field, enhancing the control of tissue regeneration processes. This scaffold can be imagined as a fixed “station” that provides a unique possibility to adjust the scaffold activity to the specific needs of the healing tissue. Synthetic bone graft substitutes, made of collagen or biomineralized collagen (i.e. biomimetic Hydroxyapatite/collagen composites) were used as starting materials for the fabrication of magnetic scaffolds. These materials are routinely used clinically to replace damaged or diseased cartilaginous or bone tissue. Our magnetization technique is based on a dip-coating process consisting in the infilling of biologically inspired porous scaffolds with aqueous biocompatible ferrofluids’ suspensions. In this technique, the specific interconnected porosity of the scaffolds allows the ferrofluids to be drawn inside the structure by capillarity. A subsequent freeze-drying process allows the solvent elimination while keeping very nearly the original shape and porosity of the scaffolds. The remaining magnetic nanoparticles, which are trapped in the structure, lead to the magnetization of the HA/Collagen scaffold. We demonstrate here the possibility to magnetize commercially available scaffolds up to magnetization values that are used in drug delivery processes. The preliminary biocompatibility test showed that the investigated scaffolds provide a suitable micro-environment for cells. The biocompatibility of scaffold facilitates the growth and proliferation of osteogenic cells.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Objectives: The aim of the present investigation was to histologically analyze the effect of using lyophilized bovine bone (GenOx (R) organic matrix) with (or without) guided tissue regeneration (using a decalcified cortical osseous membrane [GenDerm (R)]) on bone healing in surgically created critical-size defects created in rat tibia.Material and methods: Surgical critical-size bone defects were created in 64 animals that were randomly divided into four groups: group I (control); group II (defect filled with GenOx (R)); group III (defect covered by GenDerm (R)); group IV (defect filled with GenOx (R) and covered by GenDerm (R)). Animals were killed at 30 or 90 days post-surgery. The specimens were embedded in paraffin, serially cut, and stained with hematoxylin and eosin for analysis under light microscopy. The formation of new bone in the cortical area of the defect was histomorphometrically evaluated.Results: All experimental groups demonstrated superior bone healing compared with the control group. However, group IV samples showed evidence of more advanced healing at both 30 and 90 days post-surgery as compared with the other experimental groups.Conclusions: The bovine organic bone graft GenOx (R) associated with GenDerm (R) this produced the best treatment results in the case of critical-size defects in rat tibia.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The aim of this paper was report the clinical, radiographic, and histological case of adenomatoid odontogenic tumour (AOT) in adolescent woman as well as present the reconstructive treatment of AOT using fresh-frozen human bone graft with guided bone regeneration. AOT is a benign, noninvasive lesion with slow but progressive growth. Biopsy and microscopic examination confirmed the presence of an AOT. Treatment was conservative and the prognosis was excellent. The patient has been followed-up for without recurrence. The use of fresh-frozen human bone graft can be a safe choice for reconstruction of the bone defects to treat AOT.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Placement of implants in fresh sockets is an alternative to try to reduce physiological resorption of alveolar ridge after tooth extraction. This surgery can be used to preserve the bone architecture and also accelerate the restorative procedure. However, the diastasis observed between bone and implant may influence osseointegration. So, autogenous bone graft and/or biomaterials have been used to fill this gap. Considering the importance of bone repair for treatment with implants placed immediately after tooth extraction, this study aimed to present a literature review about biomaterials surrounding immediate dental implants. The search included 56 articles published from 1969 to 2012. The results were based on data analysis and discussion. It was observed that implant fixation immediately after extraction is a reliable alternative to reduce the treatment length of prosthetic restoration. In general, the biomaterial should be used to increase bone/implant contact and enhance osseointegration.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

OBJECTIVE: The purpose was to qualitatively and quantitatively compare the bone formation and graft resorption of two different bone substitutes used in both orthopedic and oral surgery, with autogenous bone as a positive control. MATERIALS AND METHODS: Three standardized bone defects were prepared in both mandibular angles of 12 adult minipigs. The defects were grafted with either autograft, anorganic bovine bone (ABB), or synthetic beta-tricalcium phosphate (beta-TCP). Sacrifice was performed after 1, 2, 4, and 8 weeks for histologic and histomorphometric analysis. RESULTS: At 2 weeks, more new bone formation was seen in defects filled with autograft than with ABB (P approximately 0.0005) and beta-TCP (P approximately 0.002). After 4 weeks, there was no significant difference between beta-TCP and the two other materials. Defects grafted with ABB still exhibited less bone formation as compared with autograft (P approximately 0.004). At 8 weeks, more bone formation was observed in defects grafted with autograft (P approximately 0.003) and beta-TCP (P approximately 0.00004) than with ABB. No difference could be demonstrated between beta-TCP and autograft. beta-TCP resorbed almost completely over 8 weeks, whereas ABB remained stable. CONCLUSION: Both bone substitutes seemed to decelerate bone regeneration in the early healing phase as compared with autograft. All defects ultimately regenerated with newly formed bone and a developing bone marrow. The grafting materials showed complete osseous integration. Both bone substitutes may have a place in reconstructive surgery where different clinical indications require differences in biodegradability.