scispace - formally typeset
Search or ask a question

Showing papers in "Journal of Biomedical Materials Research Part B in 2005"


Journal ArticleDOI
TL;DR: The results suggest the potential of using composite gelatin/PCL fibrous scaffolds for engineering three-dimensional tissues as a promising scaffold for bone-marrow stromal cell culture.
Abstract: In this article, ultrafine gelatin (Gt) fibers were successfully produced with the use of the electrical spinning or electrospinning technique. A fluorinated alcohol of 2,2,2-trifluoroethanol (TFE) was used as the dissolving solvent. The morphology of the electrospun gelatin fibers was found to be dependent on the alteration of gelatin concentration ranging from 2.5% w/v to 12.5% w/v at 2.5% increment intervals. Based on the electrospun gelatin fibers obtained, 10% w/v gelatin/TFE solution was selected and mixed with 10% w/v poly(epsilon-caprolactone) (PCL) in TFE at a ratio of 50:50 and co-electrospun to produce gelatin/PCL composite membranes. Contact-angle measurement and tensile tests indicated that the gelatin/PCL complex fibrous membrane exhibited improved mechanical properties as well as more favorable wettability than that obtained from either gelatin or PCL alone. The gelatin/PCL fibrous membranes were further investigated as a promising scaffold for bone-marrow stromal cell (BMSC) culture. Scanning electron microscopy (SEM) and laser confocal microscopy observations showed that the cells could not only favorably attach and grow well on the surface of these scaffolds, but were also able to migrate inside the scaffold up to 114 microm within 1 week of culture. These results suggest the potential of using composite gelatin/PCL fibrous scaffolds for engineering three-dimensional tissues.

1,017 citations


Journal ArticleDOI
TL;DR: A new process chain for custom-made three-dimensional (3D) porous ceramic scaffolds for bone replacement with fully interconnected channel network for the repair of osseous defects from trauma or disease is reported.
Abstract: This article reports a new process chain for custom-made three-dimensional (3D) porous ceramic scaffolds for bone replacement with fully interconnected channel network for the repair of osseous defects from trauma or disease. Rapid prototyping and especially 3D printing is well suited to generate complex-shaped porous ceramic matrices directly from powder materials. Anatomical information obtained from a patient can be used to design the implant for a target defect. In the 3D printing technique, a box filled with ceramic powder is printed with a polymer-based binder solution layer by layer. Powder is bonded in wetted regions. Unglued powder can be removed and a ceramic green body remains. We use a modified hydroxyapatite (HA) powder for the fabrication of 3D printed scaffolds due to the safety of HA as biocompatible implantable material and efficacy for bone regeneration. The printed ceramic green bodies are consolidated at a temperature of 1250 degrees C in a high temperature furnace in ambient air. The polymeric binder is pyrolysed during sintering. The resulting scaffolds can be used in tissue engineering of bone implants using patient-derived cells that are seeded onto the scaffolds. This article describes the process chain, beginning from data preparation to 3D printing tests and finally sintering of the scaffold. Prototypes were successfully manufactured and characterized. It was demonstrated that it is possible to manufacture parts with inner channels with a dimension down to 450 microm and wall structures with a thickness down to 330 microm. The mechanical strength of dense test parts is up to 22 MPa.

683 citations


Journal ArticleDOI
TL;DR: A broad overview of the current state of prosthetic bypass grafts can be found in this article, where the authors present a broad review of the state-of-the-art.
Abstract: Polymers such as Dacron((R)) and polytetrafluoroethylene (PTFE) have been used in high flow states with relative success but with limited application at lower flow states. Newer polymers with greater compliance, biomimicry, and ability to evolve into hybrid prostheses, suitable as smaller vessels, are now being introduced. In view of the advances in tissue engineering, this makes possible the creation of an ideal off-the-shelf bypass graft. We present a broad overview of the current state of prosthetic bypass grafts. (c) 2005 Wiley Periodicals. Inc.

528 citations


Journal ArticleDOI
TL;DR: The results contradict the current view that Restore SIS is a cell-free biomaterial, and that no inflammatory response is elicited by its implantation, and suggest that further studies should be conducted to evaluate the clinical safety and efficacy of SIS implant biomaterials.
Abstract: Porcine small intestinal submucosa (SIS) has been recommended as a cell-free, biocompatible biomaterial for the repair of rotator cuff tendon tear. However, we have observed noninfectious edema and severe pain in patients who have undergone SIS implantation for tendon repair. The aim of this study was to conduct an independent assessment of the safety and efficacy of Restore SIS membrane. The Restore orthobiologic implant was examined by histology and the nested PCR technique using porcine immunoreceptor DAP12 gene to examine if SIS membrane contained porcine cells or DNA, respectively. The material was also implanted into mice and rabbits for the evaluation of biological reaction and inflammatory response. Restore SIS was found to contain multiple layers of porcine cells. Chloroacetate esterase staining showed that some of these cells were mast cells. Nested PCR of the DAP12 gene demonstrated that Restore SIS contained porcine DNA material. Subcutaneous implantation of Restore SIS membrane in mice, and in rabbits for rotator cuff tendon repair, showed that the membrane caused an inflammatory reaction characterized by massive lymphocyte infiltration. In conclusion, Restore SIS is not an acellular collagenous matrix, and contains porcine DNA. Our results contradict the current view that Restore SIS is a cell-free biomaterial, and that no inflammatory response is elicited by its implantation. We suggest that further studies should be conducted to evaluate the clinical safety and efficacy of SIS implant biomaterials.

384 citations


Journal ArticleDOI
TL;DR: Woven fabrics, consisting of porous filaments via electrospinning, may be suitable candidates as tissue engineering scaffolds, according to the feasibility of three-dimensional fabric as scaffold matrices evaluated.
Abstract: Electric field-driven fiber formation (electrospinning) is developing into a practical means for preparing novel porous filament with unusual structures and affordable mechanical properties. Polycaprolactone (PCL) was dissolved in solvent mixtures of methylene chloride/N,N-dimethyl formamide with ratios of 100/0, 75/25, and 50/50 (v/v) for electrospinning. The filament was formed by coagulation of the spinning solution following the well-known principle of phase separation in polymer solutions valid in other wet shaping processes. A strand of electrospun porous filament consisted of fibers ranging from 0.5 to 12 microm in diameter. To evaluate the feasibility of three-dimensional fabric as scaffold matrices, the plain weave, which is the simplest of the weaves and the most common, was prepared with porous PCL filament. The growth characteristics of MCF-7 mammary carcinoma cells in the woven fabrics showed the important role of matrix microstructure in proliferation. This study has shown that woven fabrics, consisting of porous filaments via electrospinning, may be suitable candidates as tissue engineering scaffolds.

279 citations


Journal ArticleDOI
TL;DR: Highly purified beta-TCP appears to be advantageous relative to HA for surgical intervention in bone tumors consequent to the nature of remodeling and superior osteoconductivity.
Abstract: Long-term results are reported in 23 patients and short-term results in 30 patients presenting with bone tumors treated by curettage or resection followed by implantation of hydroxyapatite (HA) or highly purified beta-tricalcium phosphate (beta-TCP), respectively. Mean follow-up was 97 and 26 months in cases involving HA implantation and beta-TCP implantation, respectively. Radiographs revealed HA incorporation into host bone in all but two cases; moreover, no obvious evidence of HA biodegradation was observed. A single patient exhibited late deformity following implantation of HA. All grafted beta-TCP was, at least partially, absorbed and replaced by newly formed bone. The mean period required for the disappearance of radiolucent zones between the ceramics and host bone was 17 weeks in HA and 9.7 weeks in beta-TCP. Highly purified beta-TCP appears to be advantageous relative to HA for surgical intervention in bone tumors consequent to the nature of remodeling and superior osteoconductivity.

246 citations


Journal ArticleDOI
TL;DR: In this article, the elution of residual monomers from light-cured dental resins and resin composites into a 75% ethanol:water solution was studied using High-Performance Liquid Chromatography (HPLC).
Abstract: In the present work the elution of residual monomers from light-cured dental resins and resin composites into a 75% ethanol:water solution was studied using High-Performance Liquid Chromatography (HPLC). The resins studied were made by light-curing of bisphenol A glycol dimethacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), ethoxylated bisphenol A glycol dimethacrylate [Bis-EMA(4)] and mixtures of these monomers. The resin composites were made from two commercial light-cured restorative materials (Z100 MP and Filtek Z250), the resin matrix of which is based on copolymers of these monomers. The effect of the curing time on the amount of monomers eluted was investigated. The concentration of the extractable monomers was determined at several immersion periods from 3 h to 30 days. For all the materials studied, it was observed that the chemical structure of the monomers used for the preparation of the resins, which defines the chemical and physical structure of the corresponding resin, directly affects the amount of eluted monomers, as well as the time needed for the elution of this amount. In the case of composites, it seems that the elution process it is not influenced by the presence of filler.

235 citations


Journal ArticleDOI
TL;DR: A simple, layer-by-layer stereolithography method that can precisely pattern ligands, extracellular-matrix components, and growth factors, as well as controlled release particles inside a single scaffold has been developed and demonstrated.
Abstract: Understanding cell behavior inside complex, three-dimensional (3D) microenvironments with controlled spatiotemporal patterning of physical and biochemical factors would provide significant insights into the basic biology of organ development and tissue functions. One of the fundamental limitations in studying such behavior has been the inability to create patterned microenvironments within 3D scaffold structures. Here a simple, layer-by-layer stereolithography (SL) method that can precisely pattern ligands, extracellular-matrix (ECM) components, and growth factors, as well as controlled release particles inside a single scaffold, has been developed. The process also allows fabrication of predesigned internal architectures and porosities. Photocrosslinkable poly(ethylene glycol) dimethacrylate (PEGDMA) was used as the basic structural component of these microfabricated scaffolds. PEG acrylates, covalently modified with the cell adhesive peptide arginine-glycine-aspartic acid (RGD) or the ECM component heparan sulfate, was incorporated within the scaffolds to facilitate cell attachment and to allow spatial sequestration of heparan-binding growth factors. Fluorescently labeled polymer microparticles and basic fibroblast growth factor (FGF-2) were chosen to illustrate the capability of SL to spatiotemporally pattern scaffolds. The results demonstrate that a precise, predesigned distribution of single or multiple factors within a single 3D structure can be created, and specific internal architectures can be fabricated. Functionalization of these scaffolds with RGD is demonstrated, and heparan sulfate allows efficient cell attachment and spatial localization of growth factors. Such patterned scaffolds might provide effective systems to study cell behavior in complex microenvironments and could eventually lead to engineering of complex, hybrid tissue structures through predesigned, multilineage differentiation of a single stem-cell population.

194 citations


Journal ArticleDOI
TL;DR: Understanding structure-function relationships will help complete the basic physical characterization of this new material and will aid in the development of realistic mathematical models, ultimately enhancing future implant designs utilizing this material.
Abstract: In many cases of traumatic bone injury, bone grafting is required. The primary source of graft material is either autograft or allograft. The use of both material sources are well established, however, both suffer limitations. In response, many grafting alternatives are being explored. This article specifically focuses on a porous tantalum metal grafting material (Trabecular Metaltrade mark) marketed by Zimmer. Twenty-one cylindrical scaffolds were manufactured (66% to 88% porous) and tested for porosity, intrinsic permeability, tangent elastic modulus, and for yield stress and strain behavior. Scaffold microstructural geometries were also measured. Tantalum scaffold intrinsic permeability ranged from 2.1 x 10(-10) to 4.8 x 10(-10) m(2) and tangent elastic modulus ranged from 373 MPa to 2.2 GPa. Both intrinsic permeability and tangent elastic modulus closely matched porosity-matched cancellous bone specimens from a variety of species and anatomic locations. Scaffold yield stress ranged from 4 to 12.7 MPa and was comparable to bovine and human cancellous bone. Yield strain was unaffected by scaffold porosity (average = 0.010 mm/mm). Understanding these structure-function relationships will help complete the basic physical characterization of this new material and will aid in the development of realistic mathematical models, ultimately enhancing future implant designs utilizing this material.

192 citations


Journal ArticleDOI
TL;DR: The efficiency of various silver-based antimicrobial fillers in polyamide (PA) toward their silver ion (Ag+) release characteristics in an aqueous medium was investigated and discussed and could be helpful in the design of industrially relevant biomaterials.
Abstract: The efficiency of various silver-based antimicrobial fillers (elementary silver and silver substituted materials) in polyamide (PA) toward their silver ion (Ag�) release characteristics in an aqueous medium was investigated and discussed. Anode stripping voltammetry (ASV) was used for the quantitative estimation of Ag� release from these composites. The biocidal (Ag�) release from the composites was found to be dependent on the time of soaking in water and the nature of the filler. The long-term Ag� release capability of the elementary silver-based PA/Ag composite is promising compared with the commercial counterparts. The silver ion release potential of polyamide composites where the silver filling was performed by using supercritical carbon dioxide (scCO2) is also discussed. The composites release Ag� at a concentration level capable of rendering antimicrobial efficacy and proved to be active against the microbes. A good agreement exists between the Ag� release experiments and antimicrobial test results. The observed results on the influence of the nature of the filler and crystallinity on the biocidal release and the varying long-term release properties could be helpful in the design of industrially relevant biomaterials. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 75B: 311–319, 2005

185 citations


Journal ArticleDOI
TL;DR: In this article, various techniques relevant to assess the hydrothermal degradation sensitivity of biomedical grade yttria-stabilized zirconia are discussed and compared, including X-ray diffraction and scanning electron microscopy.
Abstract: Since the recent failure events of two particular series of zirconia femoral heads for total hip replacement prosthesis, a large decrease in the use of zirconia ceramics for orthopaedic implants has been observed. In spite of the biomedical success of this material during the last 10 years, this decrease in use was required for safety reasons, until the cause of the failures is known. It has been shown that these failures were related to the low temperature hydrothermal degradation (also known as aging). Thus, it is crucial to better understand the aging behavior, in order to be able to assess its importance and then control it if required. In this study, various techniques relevant to assess the hydrothermal degradation sensitivity of biomedical grade yttria-stabilized zirconia are discussed and compared. The expected outputs of conventional methods, that is, X-ray diffraction and scanning electron microscopy are examined. More recent methods like optical interferometry and atomic force microscopy are presented, with their respective benefits and drawbacks. An up-to-date comparison of these different techniques is provided, and their use for ensuring the long-term reliability of a particular batch of zirconia in terms of aging degradation is demonstrated.

Journal ArticleDOI
TL;DR: Results indicate that the higher power density QTH sources caused greater increases in tooth temperatures than the LED source and that thermocouples may underestimate the heat applied to the tooth.
Abstract: The aim of this study was to test the ability of an infrared (IR) camera to assess temperature changes and distributions in teeth below restorations when quartz-tungsten-halogen (QTH) and light-emitting diode (LED) curing lights were used to photopolymerize the restorative material. Our hypothesis was that the higher power density and broader spectral distribution of the QTH source would cause greater increases in tooth temperature than the LED source, and that these differences would be best demonstrated with the IR camera. Cavities were prepared on human third molars and restored with a resin composite restorative material. The material was light-cured using three light-curing sources using several exposure times. The external (outside the tooth) and internal (inside the pulp chamber) temperature changes during polymerization of the composite material were recorded over 360 s with thermocouples and an IR camera. Using thermocouples the maximum increase in external temperature (+17.7 degrees C) was reported for the Swiss Master light after 20 s of curing time while the minimum temperature rise (+7.8 degrees C) was reported for the Freelight 2. Whereas a 2.6 degrees C increase in internal temperature was observed after curing 20 s with the Freelight 2, 7.1 degrees C was reported after 60 s of light exposure to Astralis 10. Infrared images showed similar trends in external-internal rises in temperature as the thermocouples, although temperatures measured by the IR were generally higher. These results indicate that the higher power density QTH sources caused greater increases in tooth temperatures than the LED source and that thermocouples may underestimate the heat applied to the tooth.

Journal ArticleDOI
TL;DR: In this paper, a novel polymer network consisting of crosslinked gelatin/chitosan was prepared by a solution casting technique and the crosslinked networks were stable in the aqueous state, and had improved mechanical properties and thermal stability when compared with nonlinked gelatin (G) and chitosans/gelatin (C/G) films.
Abstract: Novel polymer networks consisting of crosslinked gelatin/chitosan were prepared by a solution casting technique. Methods for bulk crosslinking were developed to modify the gelatin/chitosan blends with the use of a nontoxic crosslinking reagent, proanthocyanidin (PA). FTIR spectral analyses of the preparations showed network formations of crosslinked gelatin, chitosan, and PA by amide and ester linkages. The crosslinked networks were stable in the aqueous state, and had improved mechanical properties and thermal stability when compared with nonlinked gelatin (G) and chitosan/gelatin (C/G) films. In vitro protease digestion and cell-culture studies showed that the PA-crosslinked C/G films are nontoxic and exhibited decreased biodegradation rate and a better ability to support cell adhesion and proliferation than noncrosslinked gelatin or chitosan alone. These results suggest that such a nontoxic crosslinked gelatin/chitosan scaffold can become a promising matrix for tissue-engineering applications.

Journal ArticleDOI
TL;DR: Based on the findings of the well-developed morphological feature and controlled drug-release profile, the gelatin-HA nanocomposite porous scaffolds are suggested to be potentially useful for hard-tissue regeneration.
Abstract: Gelatin-hydroxyapatite (HA) nanocomposite porous scaffolds were fabricated biomimetically, and their feasibility as a drug-delivery carrier for tissue-regeneration and wound-healing treatments was addressed. The composite sols were prepared by the precipitation of HA up to 30 wt % within a gelatin solution with the use of calcium and phosphate precursors, and the porous scaffold was obtained by casting the sols and further freeze drying. The obtained bodies were crosslinked with carbodiimide derivatives to retain chemical and thermal integrity. The apatite precipitates were observed to be a poorly crystallized carbonate-substituted HA. The nanocomposite scaffolds had porosities of approximately 89-92% and exhibited a bimodal pore distribution, that is, the macropores (approximately 300-500 microm) of the framework structure, and micropores (approximately 0.5-1 microm) formed on the framework surface. Transmission electron microscopy (TEM) observation revealed the precipitation of highly elongated HA nanocrystals on the gelatin network. The well-developed porous structure and organized nanocomposite configurations were in marked contrast to the directly mixed gelatin-HA powder conventional composites. For drug-release tests, tetracycline, an antibiotic drug, was entrapped within the scaffold, and the drug-release profile was examined with processing parameters, such as HA amount in gelatin, crosslinking degree, and initial drug addition. The drug entrapment decreased with increasing HA amount, but increased with increasing crosslinking degree and initial drug addition. The crosslinking of the gelatin was the prerequisite to sustaining and controlling the drug releases. Compared to pure gelatin, the gelatin-HA nanocomposites had lower drug releases, because of their lower water uptake and degradation. All the nanocomposite scaffolds released drugs in proportion to the initial drug addition, suggesting their capacity to deliver drugs in a controlled manner. Based on the findings of the well-developed morphological feature and controlled drug-release profile, the gelatin-HA nanocomposite porous scaffolds are suggested to be potentially useful for hard-tissue regeneration.

Journal ArticleDOI
TL;DR: Recent studies suggest that adherent endotoxin on orthopedic implants may also inhibit initial osseointegration of the implants, and suggest that bacterial endotoxin may have a significant role in induction of aseptic loosening.
Abstract: Aseptic loosening of orthopedic implants caused by wear particles is a major clinical problem. This review examines the hypothesis that bacterial endotoxin contributes to aseptic loosening. Clinical findings support this hypothesis: bacterial biofilms exist on many implants from patients with aseptic loosening and antibiotics in bone cement reduce the rate of aseptic loosening. Three approaches were used to demonstrate that adherent endotoxin increases bioactivity of titanium particles. These experiments measured cytokine production and osteoclast differentiation in vitro and murine calvarial osteolysis in vivo. First, removal of >99.9% of the adherent endotoxin from titanium particles significantly ablates their biological activity. Second, adding lipopolysaccharide back to these "endotoxin-free" particles restores their biological activity. Third, cells or mice that are genetically hyporesponsive to endotoxin are significantly less responsive to titanium particles than are wild-type controls. Other investigators have confirmed and extended these results to include virtually all orthopedically relevant types of particles, including authentic titanium alloy particles retrieved from patients with loosening. Our recent studies suggest that adherent endotoxin on orthopedic implants may also inhibit initial osseointegration of the implants. Taken together, these studies suggest that bacterial endotoxin may have a significant role in induction of aseptic loosening.

Journal ArticleDOI
TL;DR: It was concluded that organic coating of machined screw implant surfaces providing binding sites for integrin receptors can enhance bone implant contact and periimplant bone formation.
Abstract: The aim of the present study was to test the hypothesis that organic coating of titanium screw implants that provides binding sites for integrin receptors can enhance periimplant bone formation. Ten adult female foxhounds received experimental titanium screw implants in the mandible 3 months after removal of all premolar teeth. Four types of implants were evaluated in each animal: (1) implants with machined titanium surface, (2) implants coated with collagen I, (3) implants with collagen I and cyclic RGD peptide coating (Arg-Gly-Asp) with low RGD concentrations (100 μmol/mL), and (4) implants with collagen I and RGD coating with high RGD concentrations (1000 μmol/mL). Periimplant bone regeneration was assessed histomorphometrically after 1 and 3 months in five dogs each by measuring bone implant contact (BIC) and the volume density of the newly formed periimplant bone (BVD). After 1 month, BIC was significantly enhanced only in the group of implants coated with the higher concentration of RGD peptides (p = 0.026). Volume density of the newly formed periimplant bone was significantly higher in all implants with organic coating. No significant difference was found between collagen coating and RGD coatings. After 3 months, BIC was significantly higher in all implants with organic coating than in implants with machined surfaces. Periimplant BVD was significantly increased in all coated implants in comparison to machined surfaces also. It was concluded that organic coating of machined screw implant surfaces providing binding sites for integrin receptors can enhance bone implant contact and periimplant bone formation. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 73B: 88–96, 2005

Journal ArticleDOI
TL;DR: In this article, the effect of degradation on the tensile mechanical properties and morphology of poly(L-lactide) and polydioxanone (PDS) fibers was examined.
Abstract: Bioresorbable polymeric support devices (stents) are being developed in order to improve the biocompatibility and drug reservoir capacity of metal stents, as well as to offer a temporary alternative to permanent metallic stents. These temporary devices may be utilized for coronary, urethral, tracheal, and other applications. The present study focuses on the mechanical properties of bioresorbable fibers as well as stents developed from these fibers. Fibers made of poly(L-lactide) (PLLA), polydioxanone (PDS), and poly(glycolide-co--capro- lactone) (PGACL) were studied in vitro. These fibers combine a relatively high initial strength and modulus together with sufficient ductility and flexibility, and were therefore chosen for use in stents. The effect of degradation on the tensile mechanical properties and morphology of these fibers was examined. The expandable stents developed from these fibers demonstrated excellent initial radial compression strength. The PLLA stents exhibited excellent in vitro degradation resistance and can therefore support body conduits such as blood vessels for prolonged periods of time. PDS and PGACL stents can afford good support for 5 and 2 weeks, respectively, and can therefore be utilized for short-term applications. The degradation resistance of the stents correlates with the profile of mechanical property deterioration of the corresponding bioresorbable fibers. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 74B: 792-799, 2005

Journal ArticleDOI
TL;DR: The assumption that HA/TCP compounding was suitable to improve bone formation and scaffold resorption in the investigated biomaterials and at the same time maintain the osteoconductive properties of the scaffolds was confirmed.
Abstract: In the present study, two biphasic calcium phosphate biomaterials (BCP) with HA/TCP ratios of 50/50 and 30/70 were obtained from a pure HA biomaterial. The bioma- terials which showed the same three-dimensional geometry were implanted into corticocan- cellous costal defects of sheep. In the specimens of all three biomaterials, abundant bone formation, mineral dissolution from the biomaterial scaffolds, and active cellular resorption of the scaffolds was present after 6 and 12 months. Backscattered electron microscopy showed bone invasion into the pores of the scaffolds and micromechanical interlocking at the bone/ biomaterial interface without intervening soft tissue. The pattern of bone formation and scaffold resorption was different for cortical and cancellous bone. No time-based effect, however, was observed. Overall, the BCP biomaterials had formed significantly more bone than the HA biomaterial. Also, scaffold resorption, which was followed by a replacement with newly formed bone, was significantly higher in the BCP biomaterials. Although no significant differences were observed between both BCP biomaterials, the present study had confirmed the assumption that HA/TCP compounding was suitable to improve bone formation and scaffold resorption in the investigated biomaterials and at the same time maintain the osteoconductive properties of the scaffolds. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 74B: 458 - 467, 2005

Journal ArticleDOI
TL;DR: In this article, the root portions of 80 extracted intact human maxillary central incisors were sectioned with a carborundum disk approximately 2 mm below the cementoenamel junction perpendicular to the long axis of the teeth.
Abstract: The purpose of this study was to measure intrapulpal temperature rise induced by two kinds of bleaching gels when the tooth was exposed to a variety of light-curing units and a diode laser in vitro. The root portions of 80 extracted intact human maxillary central incisors were sectioned with a carborundum disk approximately 2 mm below the cementoenamel junction perpendicular to the long axis of the teeth. Two bleaching agents containing heat-enhancing colorant was applied to the labial surface. Light-curing units used were a conventional halogen (40 s), a high-intensity halogen (30 s), a light-emitting diode unit (40 s), and a diode laser (15 s). The temperature rise was measured in the pulpal chamber with a J-type thermocouple wire that was connected to a data logger. Ten specimens were used for each system and bleaching-agent combination. Differences between the starting temperature and highest temperature reading were taken and the calculated temperature changes were averaged to determine the mean value in temperature rise. Temperature rise values were compared using two-way analysis of variance (ANOVA) at a preset alpha of 0.05. Temperature rise varied significantly depending on curing unit and diode laser used. The diode laser induced significantly higher temperature increases than any other curing unit (11.7 degrees C). The light-emitting diode unit produced the lowest temperature changes (6.0 degrees C); however, there were no statistically significant differences among the curing units and there were no statistically significant differences between bleaching agents. Light activation of bleaching materials with diode laser caused higher temperature changes as compared to other curing units and the temperature rise detected was viewed as critical for pulpal health.

Journal ArticleDOI
TL;DR: It is suggested that the dominating mechanism of particle generation for metal-on-metal joints is surface fatigue within a nanocrystalline surface layer.
Abstract: To control and minimize wear of metal-on-metal hip joints it is essential to understand the mechanisms of debris generation. In vivo, mainly nanosize globular and needle-shaped particles are found. These can neither stem from the action of abrasion nor from tribochemical reactions. In this study the acting wear mechanisms have been first identified on the surface by means of scanning electron microscopy (SEM). Afterwards, the microstructures of the subsurface regions of explants have been investigated using a transmission electron microscope (TEM). Observation of the subsurface gave additional insight about the microstructural changes of cobalt-base alloys subjected to wear. At some distance from the surface, a network of stacking faults and hexagonal ϵ-martensite was found strengthening the bulk material. This microstructure changed into a nanocrystalline type moving closer towards the surface. A comparison of in vivo debris size and grain size of the surface suggests that the globular wear particles result from torn off nanocrystals, while the needle shaped particles are generated by fractured ϵ-martensite. Identified cracks, propagating through the nanocrystalline layer, further support these findings. Thus, it is suggested that the dominating mechanism of particle generation for metal-on-metal joints is surface fatigue within a nanocrystalline surface layer. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 72B: 206–214, 2005

Journal ArticleDOI
TL;DR: The mechanical improvement and cytocompatibility of m TGase cross-linked gelatin suggests mTGase has potential for use in stabilizing gelatin gels for tissue-engineering applications.
Abstract: The definitive goal of this research is to develop protein-based scaffolds for use in soft tissue regeneration, particularly in the field of dermal healing. The premise of this investigation was to characterize the mechanical properties of gelatin cross-linked with microbial transglutaminase (mTGase) and to investigate the cytocompatibility of mTGase cross-linked gelatin. Dynamic rheological analysis revealed a significant increase in the storage modulus and thermal stability of gelatin after cross-linking with mTGase. Static, unconfined compression tests showed an increase in Young's modulus of gelatin gels after mTGase cross-linking. A comparable increase in gel strength was observed with 0.03% mTGase and 0.25% glutaraldehyde cross-linked gelatin gels. In vitro studies using 3T3 fibroblasts indicated cytotoxicity at a concentration of 0.05% mTGase after 72 h. However, no significant inhibition of cell proliferation was seen with cells grown on lower concentrations of mTGase cross-linked gelatin substrates. The mechanical improvement and cytocompatibility of mTGase cross-linked gelatin suggests mTGase has potential for use in stabilizing gelatin gels for tissue-engineering applications.

Journal ArticleDOI
TL;DR: The data overall suggest that no significant effect can be ascribed to the ionic products of 58S bioactive gel-glass dissolution tested here and their ability to stimulate osteoblastic marker gene expression.
Abstract: Bioactive glasses dissolve upon immersion in culture medium, and release their constitutive ions into solution. There has been some evidence suggesting that these ionic-dissolution products influence osteoblast-specific processes. Here, the effect of 58S sol–gel-derived bioactive glass (60% SiO2, 36% CaO, 4% P2O5, in molar percentage) on primary osteoblasts derived from human fetal long bone explant cultures is investigated, and it is hypothesized that critical concentrations of sol–gel-dissolution products (consisting of a combination of simple inorganic ions) can enhance osteoblast phenotype in vitro by affecting the expression of a number of genes associated with the differentiation and extracellular matrix deposition processes. Cells were exposed to a range of 58S dosages continuously for a period of 4–14 days in monolayer cultures. Quantitative real-time RT-PCR analysis of a panel of osteoblast-specific markers showed a varied gene expression pattern in response to the material. The highest concentration of Ca and Si tested (96 and 50 ppm, respectively) promoted upregulation of gene expression for most markers (including alkaline phosphatase, osteocalcin, and osteopontin) at the latest time point, compared to non-58S-treated control, although this observation was not statistically significant. The same 58S concentration produced higher ALP activity levels and increased proliferation throughout the culture period, compared to lower dosages tested; however, the results generated were again not statistically significant. The data overall suggest that no significant effect can be ascribed to the ionic products of 58S bioactive gel-glass dissolution tested here and their ability to stimulate osteoblastic marker gene expression. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005

Journal ArticleDOI
TL;DR: A comparative light, scanning, and electron microscopy evaluation of the interface between Bio-Oss and bone in specimens retrieved after sinus augmentation procedures showed that Bio- Oss particles do not interfere with the normal osseous healing process aftersinus lift procedures and promote new bone formation.
Abstract: Biological interactions occurring at the bone-biomaterial interface are critical for long-term clinical success. Bio-Oss is a deproteinized, sterilized bovine bone that has been extensively used in bone regeneration procedures. The aim of the present study was a comparative light, scanning, and electron microscopy evaluation of the interface between Bio-Oss and bone in specimens retrieved after sinus augmentation procedures. Under light microscopy, most of the particles were surrounded by newly formed bone, while in a few cases, at the interface of some particles it was possible to observe marrow spaces and biological fluids. Under scanning electron microscopy, in most cases, the particle perimeter appeared lined by bone that was tightly adherent to the biomaterial surface. Transmission electron microscopy showed that the bone tissue around the biomaterial showed all the phases of the bone healing process. In some areas, randomly organized collagen fibers were present, while in other areas, newly formed compact bone was present. In the first bone lamella collagen fibers contacting the Bio-Oss surface were oriented at 243.73 +/- 7.12 degrees (mean +/- SD), while in the rest of the lamella they were oriented at 288.05 +/- 4.86 degrees (mean +/- SD) with a statistically significant difference of 44.32 degrees (p < 0.001). In the same areas the intensity of gray value was 172.56 +/- 18.15 (mean +/- SD) near the biomaterial surface and 158.71 +/- 21.95 (mean +/- SD) in the other part of the lamella with an unstatistically significant difference of 13.79 (p = 0.071). At the bone-biomaterial interface there was also an electron-dense layer similar to cement lines. This layer had a variable morphology being, in some areas, a thin line, and in other areas, a thick irregular band. The analyses showed that Bio-Oss particles do not interfere with the normal osseous healing process after sinus lift procedures and promote new bone formation. In conclusion, this study serves as a better understanding of the morphologic characteristics of Bio-Oss and its interaction with the surrounding tissues.

Journal ArticleDOI
TL;DR: Data show that TEGDMA and CQ released into an aqueous environment from resinous materials might interact, thus generating significant cytotoxic effects even at low concentrations, and may cause cell damage due to various mechanisms, GSH decrease and/or ROS increase.
Abstract: Glutathione (GSH) is important for the self-protection of cells against oxidative stress and toxic xenobiotics, whereas reactive oxygen species (ROS) at elevated concentrations may cause detrimental alterations of cell membranes, DNA, and other cellular structures. The present investigation addressed the effects of triethylene-glycoldimethacrylate (TEGDMA) and camphorquinone (CQ) on glutathione metabolism and the formation of ROS in oral cells. Primary human pulp fibroblasts were exposed to various concentrations of TEGDMA and CQ (0.1-5 mM). Subsequently, GSH concentration and ROS formation were analyzed with the use of the monobromobimane assay (GSH) and 2',7'-dichlorofluorescein diacetate (DCFH-DA) (ROS). The endogenous ROS hydrogen peroxide (H2O2) was used as a positive control (0.02-2 mM). TEGDMA significantly decreased GSH at concentrations between 0.5 and 5 mM (p or=1 mM, but had only a moderate effect on GSH at the highest test concentration. Hydrogen peroxide increased ROS and simultaneously decreased GSH at concentrations of >or=0.2 mM. These data show that the investigated substances may cause cell damage due to various mechanisms, GSH decrease and/or ROS increase. As a consequence, TEGDMA and CQ released into an aqueous environment from resinous materials might interact, thus generating significant cytotoxic effects even at low concentrations.

Journal ArticleDOI
TL;DR: The coatings appeared effective against Staphylococcus epidermidis adhesion for 24, 48, and 0.5 h in PBS, urine, and saliva, respectively, and the variations in effectiveness could be attributed to conditioning film formation.
Abstract: Poly(ethylene oxide) (PEO) coatings have been shown to reduce the adhesion of different microbial strains and species and thus are promising as coatings to prevent biomaterial-centered infection of medical implants. Clinically, however, PEO coatings are not yet applied, as little is known about their stability and effectiveness in biological fluids. In this study, PEO coatings coupled to a glass substratum through silyl ether bonds were exposed for different time intervals to saliva, urine, or phosphate-buffered saline (PBS) as a reference at 37°C. After exposure, the effectiveness of the coatings against bacterial adhesion was assessed in a parallel plate flow chamber. The coatings appeared effective against Staphylococcus epidermidis adhesion for 24, 48, and 0.5 h in PBS, urine, and saliva, respectively. Using XPS and contact-angle measurements, the variations in effectiveness could be attributed to conditioning film formation. The overall short stability results from hydrolysis of the coupling of the PEO chains to the substratum.

Journal ArticleDOI
TL;DR: Three-dimensional apatite-promoted osteoblastic differentiation can be observed in a 3D model system that is relevant to tissue engineering, and its utilization in the investigation of apatites' promotion in vitro is reported in this paper.
Abstract: Biomimetic apatites have been reported to promote osteogenic activities in numerous in vivo and in vitro models, but the precise mechanism by which the apatite microenvironment promotes such activities is not well understood. Such mechanistic studies require reproducible model systems that are relevant to tissue engineering practices. Although two-dimensional (2D) apatite-coated polystyrene culture dishes provide practicality and reproducibility, they do not simulate the effects of the three-dimensional (3D) microenvironment and degrading polymeric substrates. A simple 3D model system to address these relevant effects, and its utilization in the investigation of apatite-promoted osteoblastic differentiation in vitro is reported in this paper. Apatite coating was achieved by sequentially immersing poly(lactide-co-glycolide) (PLGA) scaffolds into different simulated body fluids (SBF). SEM, EDX, FTIR, TEM electron diffraction confirmed the apatite coating to comprise of calcium-deficient carbonated hydroxyapatite crystals. While both apatite-coated and noncoated PLGA scaffolds supported MC3T3-E1 attachment, spreading, and proliferation, significant differences in osteoblastic differentiation were observed. Relative to noncoated controls, quantitative real-time PCR revealed significant apatite-associated suppression of alkaline phosphatase (ALP), early upregulation of osteopontin (OPN) at 3 days, and upregulation of osteocalcin (OCN) and bone sialoprotein (BSP) at 4 weeks. In summary, apatite-promoted osteoblastic differentiation can be observed in a 3D model system that is relevant to tissue engineering. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005

Journal ArticleDOI
TL;DR: This study evaluated the hypothesis that if hydrophilic nanofillers were dispersed evenly within the adhesive layer under moist conditions, adding them to a one-bottle dentin adhesive might improve the mechanical properties of the adhesivelayer, and accordingly increase the bond strength.
Abstract: This study evaluated the hypothesis that if hydrophilic nanofillers were dispersed evenly within the adhesive layer under moist conditions, adding them to a one-bottle dentin adhesive might improve the mechanical properties of the adhesive layer, and accordingly increase the bond strength. The flexural strength (FS), the degree of conversion (DC), and the microtensile bond strength (MTBS) to the dentin of four experimental ethanol-based one-bottle dentin adhesives containing 0, 0.5, 1.0, and 3.0 wt % of 12-nm hydrophilic fumed silica were evaluated, and the distribution of the nanofillers were compared using transmission electron microscopy (TEM). Although the nanofiller content did not affect the DC, the FS tended to increase with increasing nanofiller content. The MTBS appeared to increase when up to 1.0 wt % of the nanofillers were added, but they were statistically not significant. However, when 3.0 wt % of the nanofillers were added, the MTBS decreased significantly comparing to the adhesive containing 0.5 wt % nanofillers (p < 0.05). The TEM image suggested that if the nanofillers within the adhesive were 3.0 wt % and applied to a wet dentin surface, they aggregated easily into large clusters and would decrease the MTBS.

Journal ArticleDOI
TL;DR: The combination of properties indicates that the novel β-Ca2SiO4 cement might be suitable for potential applications in the biomedical field, preferentially as materials for bone/dental repair and controlled drug-delivery systems.
Abstract: This study sought to investigate the physical and chemical properties of beta-dicalcium silicate (beta-Ca(2)SiO(4)) in order to evaluate its use as an injectable bioactive cement filler. Workable beta-Ca(2)SiO(4) pastes with a liquid-to-powder (L/P) ratio of 1.0-1.2 could be injected for 10-30 min (nozzle diameter 2.0 mm) and enabled initial setting times of 60-180 min. The setting process yielded cellular structures with compressive strengths of 4.8-28.8 MPa after 2-28 days. The paste was soaked in simulated body fluid (SBF), and the results demonstrated that it exhibited a moderate degradation and could induce carbonated hydroxyapatite formation. The ionic products of the paste dissolution enhanced a proliferative response of fibroblasts compared with the cells cultured alone, and this cement could also support adhesion and spreading of the mesenchymal stem cells. Finally, with the use of gentamicin as a model drug, it was found that a high dose of drug release from the paste was maintained for 14 days, and there was a sustained release over 4 weeks. This combination of properties indicates that the novel beta-Ca(2)SiO(4) cement might be suitable for potential applications in the biomedical field, preferentially as materials for bone/dental repair and controlled drug-delivery systems.

Journal ArticleDOI
TL;DR: A dually modified polyurethaneurea by incorporating endothelial cell adhesive YIGSR peptide sequences as chain extenders and nonthrombogenic PEG as a soft segment (PUUYIGSR-PEG) in the polymer backbone showed superior mechanical properties compared to the control PEG-modified polyurenurea (PUUPPD-P EG).
Abstract: Improved endothelialization without platelet adhesion is essential to enhance the long-term patency of synthetic vascular grafts and other blood-contacting devices. We have developed a dually modified polyurethaneurea by incorporating endothelial cell adhesive YIGSR peptide sequences as chain extenders and nonthrombogenic PEG as a soft segment (PUUYIGSR-PEG) in the polymer backbone. PUUYIGSR-PEG was successfully synthesized and characterized by proton NMR, FTIR, GPC, DSC, ESCA, and contact angle measurement. Despite having similar molecular weight, the peptide/PEG-modified polyurethaneurea (PUUYIGSR-PEG) showed superior mechanical properties compared to the control PEG-modified polyurethaneurea (PUUPPD-PEG). Virtually no platelet adhesion was observed on PUUYIGSR-PEG, while endothelial cell adhesion, spreading, and migration were significantly greater on PUUYIGSR-PEG compared to PUUPPD-PEG. Thus, this bioactive polymer may be an appropriate biomaterial for small diameter vascular grafts.

Journal ArticleDOI
TL;DR: In this paper, the influence of implant/abutment joint designs on abutment screw loosening in a dental implant system, using nonlinear dynamic analysis of the finite element method (FEM).
Abstract: The objective of this study was to investigate the influence of implant/abutment joint designs on abutment screw loosening in a dental implant system, using nonlinear dynamic analysis of the finite element method (FEM). This finite element simulation study used two dental implant systems: the Ankylos implant system (Degusa Dental, Hanau, German) with a taper joint (taper joint-type model), and the Branemark implant system (Nobel Biocare, Gothenburg, Sweden) with an external hex joint (external hex joint-type model). The nonlinear dynamic analysis was performed using three-dimensional finite element analysis. In comparing the movement of the taper type-joint model and external hex type-joint model, it was found that the external hex type-joint model had greater movement than the taper type-joint model. The external hex joint-type model showed rotation movement, whereas the movement of the taper joint-type model showed no rotation. It was concluded that the nonlinear dynamic analysis used in this study clearly demonstrated the differences in rotation of components in dental implant systems with taper or external hex joints.