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PubMed2001

Osteogenic evaluation of glutaraldehyde crosslinked gelatin composite with fetal rat calvarial culture model.

The cytotoxicity of the synthetic bone substitute composed of tricalcium phosphate and glutaraldehyde crosslinked gelatin (GTG) were evaluated by osteoblast cell culture. In a previous study, the GTG composites were soaked in distilled water for 1, 2, 4, 7, 14, 28, and 42 days, and then the solutions (or extracts) were cocultured with osteoblasts to evaluate the cytotoxicity of GTG composites by alive cell counting. In this study, the extracts were cocultured with the osteoblasts; thereafter, the concentration of transforming growth factor-beta (TGF-beta1) and prostaglandin E2 (PGE2) in the medium was analyzed to strictly reflect the biological effects of GTG composites on the growth of osteoblasts. In order to investigate the osteoconductive potential of the GTG composites on new bone formation in a relative short term, a model of neonatal rat calvarial organ culture was designed prior to animal experiments. Three experimental materials of 4, 8, and 12% GTG composites were evaluated by fetal rat calvarial organ culture for their ability for bone regeneration. Deproteinized bovine and porcine cancellous bone matrixes were used as the controlled materials. All the organ culture units were maintained in cultured medium for 5 weeks. Following the culture period, the morphology of tissue was observed under an optical microscope, and the quantitative evaluation of the new generation bone was determined by using a semiautomatic histomorphometeric method. Except in the initial 4 days, the concentration of TGF-beta1 of 4% and 8% GTG composites was higher than that of the blank group for all the other experimental time periods. The PGE2 concentration for 4% and 8% GTG composites was lower than that of the blank group. It revealed that the 4% and 8% GTG composites would not lead to inflammation and would promote osteoblast growth. The morphology and activity of the osteoblasts were not transformed or changed by the 2 GTG composites. For the 12% GTG composite, the performance of the in vitro condition was inferior to the blank group and the other 2 GTG composites. Although the concentration of TGF-beta1 and PGE2 was gradually back to normal after 14 days, the morphology of the osteoblasts was abnormal with features such as contracted cytoplast structures. The osteoblast was damaged perhaps in the initial stage. We suggested that the 4% and 8% GTG composites should be soaked in distilled water at least for 4 days before medical applications. The 12% GTG composite and the composites with a concentration of glutaraldehyde solution higher than 12% were not recommended as a medical prostheses in any condition. The fetal rat calvaria culture also showed the same results with the analysis of TGF-beta1 and PGE2. From the study, we could predict the results of animal experiments in the future.

Animals↗
PubMed2004

The in vivo performance of a sol-gel glass and a glass-ceramic in the treatment of limited bone defects.

The in vivo evaluation, in New Zealand rabbits, of a SiO(2)-P(2)O(5)-CaO sol-gel glass and a SiO(2)-P(2)O(5)-CaO-MgO glass-ceramic, both bioactive in Kokubo's simulated body fluid (SBF), is presented. Bone defects, performed in the lateral aspect of distal right femoral epiphysis, 5mm in diameter and 4mm in depth, were filled with (i) sol-gel glass disks, (ii) glass-ceramic disks, or (iii) no material (control group). Each group included 8 mature and 8 immature rabbits. A 4-month radiographic study showed good implant stability without axial deviation of extremities in immature animals and periosteal growth and remodelling around and over the bone defect. After sacrifice, the macroscopic study showed healing of bone defects, with bone coating over the implants. The morphometric study showed a more generous bone formation in animals receiving sol-gel glass or glass-ceramic disks than in control group. Histomorphometric study showed an intimate union of the new-formed bone to the implants. This study allows considering both materials as eligible for bone substitution or repair. Their indications could include cavities filling and the coating of implant surfaces. The minimum degradation of glass-ceramic disks suggests its application in locations of load or transmission forces. As specific indication in growth plate surgery, both materials could be used as material of interposition after bony bridges resection.

Animals↗
PubMed2005

Nucleation of biomimetic apatite in synthetic body fluids: dense and porous scaffold development.

The effectiveness of synthetic body fluids (SBF) as biomimetic sources to synthesize carbonated hydroxyapatite (CHA) powder similar to the biological inorganic phase, in terms of composition and microstructure, was investigated. CHA apatite powders were prepared following two widely experimented routes: (1) calcium nitrate tetrahydrate and diammonium hydrogen phosphate and (2) calcium hydroxide and ortophosphoric acid, but using SBF as synthesis medium instead of pure water. The characteristics of the as-prepared powders were compared, also with the features of apatite powders synthesized via pure water-based classical methods. The powder thermal resistance and behaviour during densification were studied together with the mechanical properties of the dense samples. The sponge impregnation process was used to prepare porous samples having morphological and mechanical characteristics suitable for bone substitution. Using this novel synthesis was it possible to prepare nanosized (approximately equal to 20 nm), pure, carbonate apatite powder containing Mg, Na, K ions, with morphological and compositional features mimicking natural apatite and with improved thermal properties. After sintering at 1250 degrees C the carbonate-free apatite porous samples showed a surprising, high compressive strength together with a biomimetic morphology.

Apatites↗
PubMed2000

The radicular groove: its potential clinical significance.

This report examines three clinical cases of root-filled teeth with primary endodontic lesions. During endodontic surgery, an area of incomplete root bifurcation beginning in the coronal or middle third of the root surface and terminating at or near the apical foramen were observed. The radicular grooves of two teeth were eliminated using a round bur ("saucerization"), and the resulting defect was filled with a bone substitute or calcium sulfate and covered by an absorbable collagen membrane. The other tooth was extracted, the groove was eliminated with a similar technique, and the tooth was replanted. Bacteria have been reported in chronic apical lesions. Our observations suggest that after conventional endodontic therapy, the etiology of a nonresolving primary endodontic lesion may be bacteria of endodontic origin sequestered within the protective confines of an apical-radicular groove.

Absorbable Implants↗
PubMedDate not supplied

Ten-year experience with craniofacial implants: clinical and experimental results.

The choice of bone substitute to be used in the cranio-maxillofacial districts raises several problems relating to the biocompatibility and mechanical resistance of the material. Over the past 10 years a total of 245 cranio-maxillofacial skeletal implants have been performed by the Department of Plastic Surgery at Niguarda Ca' Granda Hospital in Milan. The choice of material varied depending on the market availability of products and the experience acquired of both positive results and the onset of short-term and long-term complications. All patients were monitored with a minimum follow-up of 2 years and a maximum of 10 (mean 36 months). The following parameters were taken into account: complications linked to graft contamination, graft extrusion and decubitus, resorption times, degradable materials, resorption of underlying bone tissue and reactivity of the surrounding tissues. Studies on the cell cytohistotoxicity of materials used were performed in parallel by the cell culture laboratory at the Department of Plastic Surgery of Niguarda Hospital, using human keratinocyte and fibroblast cultures.

Biocompatible Materials↗
PubMed1998

[Tricalcium phosphate, an antibiotic carrier: a study focused on experimental osteomyelitis in rabbits].

PURPOSE OF THE STUDY: Macroporous beta tricalcium phosphate ceramic beads were elaborated to be a resorbable bone substitute and a drug delivery system carrying gentamicin or vancomycin. The aim of this study was to evaluate this implant into a rabbit experimental osteomyelitis. MATERIAL AND METHOD: Experimentation included 24 rabbits and was performed in three stages, according to Norden's description. Induction of osteomyelitis was obtained by injection of a sclerosing agent and of Staphylococcus aureus through the lateral side of the metaphysis of the proximal tibia. Three weeks after inoculation, animals were randomly dispatched to one of the three treatment groups. After surgical debridment (to collect cinetics data), the first group received no further treatment and was considered as a control; the second group received a ceramic implant; the third group received a gentamicin-loaded ceramic implant. Euthanasia occurred between 2 days and 21 days after the debridment. Bone samples were obtained to quantify the bacterial and gentamicin bone concentrations. Gentamicin level was also measured inside the ceramic implant. Antibiotic concentration was assessed by a immunoenzymatic method. RESULTS: Osteomyelitis was obtained in 21 of the 24 animals (87.5%). Antibiotic release was early and complete (before the third day) but gentamicin still remained in the bone for 10 days. Bacterial concentration suggested an antimicrobial activity of the implant, but not a full sterilisation of the osteomyelitis. CONCLUSION: Norden's experimental osteomyelitis model with rabbit was proposed to assess the therapeutic activity of systemic antibiotics, but not to evaluate biomaterials. Therefore we have shifted for experimental evaluation of biomaterials to a metaphyseal osteomyelitis in the sheep, the patterns of which are close from those of the human disease.

Animals↗
PubMed1996

Spectroscopic studies of a multiphasic polymer-ceramic mixture material.

We report the results obtained by infrared (IR) and X-ray photoelectron spectroscopy (XPS) on the multiphasic composite material formed by the mixture of biphasic calcium phosphate (BCP) and hydroxypropylmethylcellulose (HPMC). This synthetic material, intended for bone substitution, is injectable and allows percutaneous surgery. Core level spectra of carbon, oxygen, calcium, and phosphorus were recorded on separate components before mixing and then compared to those obtained in the final product. Analysis of the spectra shows that formation of calcium carbonate has occurred upon mixing the components in agreement with IR results. An attempt to explain the formation mechanism of the composite is given involving the nature of the constituents on one hand and the possible reactions between the different components on the other.

Bone Substitutes↗
PubMed2001

Delayed surgery does not reduce the interface strength between the surface of a bone fracture and a self-curing injectable hydroxyapatite (Norian SRS).

The shear strength of the interface between bone and an injectable calcium phosphate bone substitute that cures to form a carbonated apatite (Norian SRS) was measured and related to the time that elapsed between injury and surgery. Eleven rabbits had a 3 mm drill hole made in the retropatellar aspect of the distal femur. After one week, the rabbits were reoperated on and the hole filled with Norian SRS after it had been cleaned gently with a sponge. During the same procedure a similar hole was burred in the opposite femur and filled with Norian SRS after a few minutes ("immediate injection"). Four other rabbits had only one side operated on with immediate injection of Norian SRS to compare with the opposite untreated side. The rabbits were killed four days after the injection of Norian SRS. The femurs were prepared and sawed perpendicularly to the burr channels to produce discs 3.5 mm thick. A push out test of the Norian SRS plug within the bone disc was done to measure the force at failure. In the immediately injected specimens the failure occurred at a mean of 28 N (range 5-57) compared with 42 N (range 25-65) in the specimens injected after a one week delay. There was no significant difference between delayed and immediate treatment (95% confidence interval -5 to 133). The histological examination showed that 9 of the 12 specimens had Norian SRS still adherent to half or more of the circumference of the hole. This indicates that the failure occurred in the Norian SRS rather than in the bone or at the interface.

Animals↗
PubMed2004

Treatment of periapical inflammatory lesion with the combination of platelet-rich plasma and tricalcium phosphate: a case report.

Periapical surgery is an important treatment alternative in the presence of a periapical inflammatory lesion. To achieve optimal healing and regeneration of the bone, different bone substitutes or barrier membranes can be used after degranulation of the lesion. Tricalcium phosphate (TCP) graft material is one of these substitutes. Platelet Rich Plasma (PRP) preparation is a new biotechnology and can be used in many different surgical procedures. It consists of thrombocyte concentrates and high amounts of growth factors (GFs), especially platelet derived growth factor (PDGF), insulin-like growth factor (IGF-I) and transforming growth factor (TGF-beta), which are important in wound healing and regeneration. In this case report, use of platelet gel in conjunction with TCP in the treatment of periapical inflammatory lesion and the results of 12 months has been reported.

Alveolar Bone Loss↗
PubMed2003

New biomorphic SiC ceramics coated with bioactive glass for biomedical applications.

A new generation of light, tough and high-strength material for medical implants for bone substitutions with a good biological response is presented. The innovative product that fulfills all these requirements is based on biomorphic silicon carbide ceramics coated with a bioactive glass layer. The combination of the excellent mechanical properties and low density of the biomorphic SiC ceramics, used as a base material for implants, with the osteoconducting properties of the bioactive glass materials opens new possibilities for the development of alternative dental and orthopedic implants with enhanced mechanical and biochemical properties that ensures optimum fixation to living tissue. Biomorphic SiC is fabricated by molten-Si infiltration of carbon templates obtained by controlled pyrolysis of wood. Through this process, the microstructure of the final SiC product mimics that of the starting wood, which has been perfected by natural evolution. The basic features of such microstructure are its porosity (ranging from 30% to 70%) and its anisotropy, which resembles the cellular microstructure and the mechanical characteristics of the bone. The SiC ceramics have been successfully coated with a uniform and adherent bioactive glass film by pulsed laser ablation using an excimer ArF laser. The excellent coverage of the SiC rough surface without film spallation or detachment is demonstrated. In order to assess the coating bioactivity, in vitro tests by soaking the samples in simulated body fluid have been carried out. After 72 h, the formation of a dense apatite layer has been observed even in interconnecting pores by SEM and energy dispersive X-ray spectroscopy analysis demonstrating the bioactive response of this product.

Biomedical Engineering↗
PubMed2006

Carbonate release from carbonated hydroxyapatite in the wide temperature rage.

Synthetic carbonated apatite ceramics are considered as promising alternative to auto- and allograft materials for bone substitute. The aim of this study was to investigate the thermal stability of an AB-type carbonated apatite in the wide temperature range. The data on the thermal stability have to allow the conditions of the sintering of the ceramics to be controlled. Initial carbonated apatite powders were prepared by interaction between calcium oxide and ammonium hydrogen phosphate with addition of ammonium carbonate. Decomposition process was monitored by infra red spectroscopy, weight loss and X-ray diffraction of solid, and by infra red analysis of condensed gas phase resulted from the thermal decomposition of the sample in equilibrium conditions. Features of carbon monoxide and carbon dioxide release were revealed. The synthesized AB-type carbonated apatite is started to decompose at about 400 degrees Celsius releasing mainly carbon dioxide, but retained some carbonate groups and apatite structure at the temperature 1100 degrees Celsius useful to prepare porous carbonate-apatite ceramics intended for bone tissue engineering scaffolds.

Apatites↗
PubMed2007

A poly(lactide-co-glycolide)/hydroxyapatite composite scaffold with enhanced osteoconductivity.

Biodegradable polymer/ceramic scaffolds can overcome the limitations of conventional ceramic bone substitutes. However, the conventional methods of polymer/ceramic scaffold fabrication often use organic solvents, which might be harmful to cells or tissues. Moreover, scaffolds fabricated with the conventional methods have limited ceramic exposure on the scaffold surface since the polymer solution envelopes the ceramic particles during the fabrication process. In this study, we developed a novel fabrication method for the efficient exposure of ceramic onto the scaffold surface, which would enhance the osteoconductivity and wettability of the scaffold. Poly(D,L-lactide-co-glycolide)/nanohydroxyapatite (PLGA/HA) scaffolds were fabricated by the gas foaming and particulate leaching (GF/PL) method without the use of organic solvents. Selective staining of ceramic particles indicated that HA nanoparticles exposed to the scaffold surface were observed more abundantly in the GF/PL scaffold than in the conventional solvent casting and particulate leaching (SC/PL) scaffold. Both types of scaffolds were implanted to critical size defects in rat skulls for 8 weeks. The GF/PL scaffolds exhibited significantly enhanced bone regeneration when compared with the SC/PL scaffolds. Histological analyses and microcomputed tomography of the regenerated tissues showed that bone formation was more extensive on the GF/PL scaffolds than on the SC/PL scaffolds. Compared with the SC/PL scaffolds, the enhanced bone formation on the GF/PL scaffolds may result from the higher exposure of HA nanoparticles to the scaffold surface. These results show that the biodegradable polymer/ceramic composite scaffolds fabricated with the novel GF/PL method can enhance bone regeneration compared with those fabricated with the conventional SC/PL method.

Absorbable Implants↗
PubMedDate not supplied

Modulation of in vitro angiogenesis in a three-dimensional spheroidal coculture model for bone tissue engineering.

One of the major challenges in tissue engineering of bone substitutes remains vascularization of the transplant. We have developed a three-dimensional collagen-based coculture system to assess interactions between human endothelial cells (hECs) and human osteoblasts (hOBs) in vitro. Human umbilical vein endothelial cells (HUVECs) were grown as three-dimensional multicellular spheroids and seeded in a collagen matrix to assess sprouting of the spheroids, that is, formation of tubelike structures resembling early capillaries. Direct cell contact between hOBs and HUVECs was established by incorporating hOBs into the EC spheroids, thus forming heterogeneous cospheroids. Spatial organization of cospheroids and sprout configuration were assessed by immunohistochemical wholemount staining techniques and confocal laser microscopy. Cumulative sprout length of spheroids was quantitatively analyzed by digital imaging planimetry. In this model HUVECs and hOBs formed heterogeneous cospheroids with distinct spatial organization. The ability of HUVEC spheroids to form tubelike structures on angiogenic stimulation with vascular endothelial growth factor and basic fibroblast growth factor was suppressed in heterogeneous HUVEC/hOB cospheroids. The model system introduced in this study may be useful to assess the mechanisms involved in regulating angiogenesis during bone formation and to further investigate the mechanisms by which heterotypic cell-cell interactions inhibit endothelial tube formation for applications in bone tissue engineering.

Bone Substitutes↗
PubMed2006

Combining particle size distribution and isothermal calorimetry data to determine the reaction kinetics of alpha-tricalcium phosphate-water mixtures.

Many calcium phosphate bone substitutes are based on the use of alpha-tricalcium phosphate (alpha-TCP) powder. This compound has been intensively studied, but some aspects of alpha-TCP reactivity are still controversial. The goal of this study was to determine the setting kinetics of alpha-TCP based on a new approach that compared particle size distribution data to isothermal calorimetry data. Results indicated that alpha-TCP conversion is mostly controlled by surface reactions, with at later stages a diffusion-controlled mechanism. The presence of an X-ray amorphous alpha-TCP fraction in the crystalline alpha-TCP powder increased the dissolution rate threefold, without modifying the reaction mechanism.

Biocompatible Materials↗
PubMed2000

[Intra-individual comparison of alpha- and beta-TCP ceramics in an animal experiment].

In the quest for bioinert adaptable alloplastic materials, TCP ceramics have gained a new application in craniofacial bone substitutes. Therefore, a histomorphological, intraindividual, comparative study was conducted on seven adult Goettingen miniature pigs (GMP) to analyze the difference of the degradation and remodelling processes of alpha-TCP and beta-TCP in critical size defects of the proximal tibiae. In addition, primary insertion of dental implants followed to study osseous integration. The critical size defects, which were created in the proximal tibiae in GMPs, were filled on the left side with beta-TCP and on the right side with alpha-TCP. Two GMPs were used as control group. After 4-68 weeks of investigation, the GMPs were sacrificed by narcosis. The histological investigation showed that these ceramics have an osteoconductive effect. It was noted that ossification proceeds centripetally. It could be demonstrated that the degradation of the materials follows a hydrolytical process and that the intratrabecular integrated ceramic remnants follow a dynamic remodelling process. Within 68 weeks after implantation, 90% of the TCP granulae were degraded. Macrophages were found in the marrow space, containing microparticles of TCP, especially after alpha-TCP implantation. In conclusion, defined degradation of these ceramics allows early functional bone regeneration with an additional undisturbed biofunctional unisotrop orientation of new trabeculae. Furthermore, dental implants should be inserted 5-6 months after TCP implantation.

Animals↗
PubMed2000

In vitro bioactive behavior of hydroxylapatite-coated porous Al(2)O(3).

To produce bioactive materials for bone substitutes, two major deposition methods, suspension method and thermal deposition method, were employed to develop bioactive, mechanically strong, and porous ceramics. Hydroxylapatite (HA) has been uniformly coated onto inner pore surfaces of reticulated alumina substrates. It has been found that the in vitro bioactivity of HA coatings was affected by both structural crystallinity and specific surface area. Well-crystallized HA heat-treated at high temperatures has resulted in reduced bioactivity. The bio-reaction rate was found to increase with the surface area of HA. We have found that the stability of the well-crystallized HA is associated with the high driving force required for the formation of hydroxy-carbonate apatite (HCA) phase.

Aluminum Oxide↗
PubMed2002

[Quality assurance of powders for bioceramic applications with image analysis].

Bone substitute materials are very demanding with respect to their quality, in particular, a high toughness and durability are required. In case of producing the composites by sintering of mechanically generated powder mixtures, a high efficiency of mixture is demanded, too. The characterisation of such particle systems is difficult. An effective method is the image analysis supported by statistical evaluation of both the size and the shape distributions of particles and agglomerates. As it is proved by first results, powder mixtures of hydroxyapatite can be described by the geometry of voids in the agglomerate structure using the shape factor weighted by area of the respective image object. As a measure of the efficiency of mixture, the degree of reproducibility was introduced.

Bone Substitutes↗
PubMed1994

Use of enhanced chemiluminescence to quantify protein adsorption to calcium phosphate materials and microcarrier beads.

The adsorption of serum proteins to calcium phosphate bone substitute materials, positively-charged dextrose and negatively-charged polystyrene microcarrier beads was compared by SDS-PAGE (sodium dodecyl sulphate-polyacrylamide gel electrophoresis). Protein adsorption to hydroxyapatite (HA)-based materials was influenced by chemical composition. Surface charge sign, distribution and/or functional group affected protein adsorption to microcarrier beads. Enhanced chemiluminescence was used to quantify adsorption of fibronectin and vitronectin following Western blotting, and to monitor the kinetics of adsorption of these two proteins to HA and Biosilon. Relative to total protein, fluctuating levels of fibronectin were detected on both materials. In contrast, vitronectin adsorption increased over the course of the incubation period with maximal relative adsorption detected after 30 min on Biosilon and 60 min on HA.

Adsorption↗