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Replacement Materials (replacement + material)
Kinds of Replacement Materials Selected AbstractsDevelopment of a 95/5 poly(L -lactide- co -glycolide)/hydroxylapatite and ,-tricalcium phosphate scaffold as bone replacement material via selective laser sinteringJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008Rebecca Louise Simpson Abstract 95/5 Poly(L -lactide- co -glycolide) was investigated for the role of a porous scaffold, using the selective laser sintering (SLS) fabrication process, with powder sizes of 50,125 and 125,250 ,m. SLS parameters of laser power, laser scan speed, and part bed temperature were altered and the degree of sintering was assessed by scanning electron microscope. Composites of the 125,250 ,-tricalcium phosphate (CAMCERAM® II) were sintered, and SLS settings using 40 wt % CAMCERAM® II were optimized for further tests. Polymer thermal degradation during processing led to a reduction in number and weight averaged molecular weight of 9% and 12%, respectively. Compression tests using the optimized composite sintering parameters gave a Young's modulus, yield strength, and strain at 1% strain offset of 0.13 ± 0.03 GPa, 12.06 ± 2.53 MPa, and 11.39 ± 2.60%, respectively. Porosity was found to be 46.5 ± 1.39%. CT data was used to create an SLS model of a human fourth middle phalanx and a block with designed porosity was fabricated to illustrate the process capabilities. The results have shown that this composite and fabrication method has potential in the fabrication of porous scaffolds for bone tissue engineering. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] Clinical outcomes following treatment of human intrabony defects with GTR/bone replacement material or access flap aloneJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 9 2004A multicenter randomized controlled clinical trial Abstract Aim: This prospective multicenter randomized controlled clinical trial was designed to compare the clinical outcomes of papilla preservation flap surgery with or without the application of a guided tissue regeneration (GTR)/bone replacement material. Materials and Methods: One hundred and twenty-four patients with advanced chronic periodontitis were recruited in 10 centers in seven countries. All patients had at least one intrabony defect of 3 mm. The surgical procedures included access for root instrumentation using either the simplified or the modified papilla preservation flap in order to obtain optimal tissue adaptation and primary closure. After debridement, the regenerative material was applied in the test subjects, and omitted in the controls. At baseline and 1 year following the interventions, clinical attachment levels (CALs), probing pocket depths (PPDs), recession, full-mouth plaque scores and full-mouth bleeding scores (FMBS) were assessed. Results: One year after treatment, the test defects gained 3.3±1.7 mm of CAL, while the control defects yielded a significantly lower CAL gain of 2.5±1.5 mm. Pocket reduction was also significantly higher in the test group (3.7±1.8 mm) when compared with the controls (3.2±1.5 mm). A multivariate analysis indicated that the treatment, the clinical centers, baseline PPD and baseline FMBS significantly influenced CAL gains. Odds ratios (ORs) of achieving above-median CAL gains were significantly improved by the test procedure (OR=2.6, 95% CI 1.2,5.4) and by starting with deeper PPD (OR=1.7, 1.3,2.2) but were decreased by receiving treatment at the worst-performing clinical center (OR=0.9, 0.76,0.99). Conclusions: The results of this trial indicated that regenerative periodontal surgery with a GTR/bone replacement material offers an additional benefit in terms of CAL gains, PPD reductions and predictability of outcomes with respect to papilla preservation flaps alone. [source] Adopting Lead-Free Electronics: Policy Differences and Knowledge GapsJOURNAL OF INDUSTRIAL ECOLOGY, Issue 4 2004Julie M. Schoenung For more than a decade, the use of lead (Pb) in electronics has been controversial: Indeed, its toxic effects are well documented, whereas relatively little is known about proposed alternative materials. As the quantity of electronic and electrical waste (e-waste) increases, legislative initiatives and corporate marketing strategies are driving a reduction in the use of some toxic substances in electronics. This article argues that the primacy of legislation over engineering and economics may result in selecting undesirable replacement materials for Pb because of overlooked knowledge gaps. These gaps include the need for: assessments of the effects of changes in policy on the flow of e-waste across state and national boundaries; further reliability testing of alternative solder alloys; further toxicology and environmental impact studies for high environmental loading of the alternative solders (and their metal components); improved risk assessment methodologies that can capture complexities such as changes in waste management practices, in electronic product design, and in rate of product obsolescence; carefully executed allocation methods when evaluating the impact of raw material extraction; and in-depth risk assessment of alternative end-of-life (EOL) options. The resulting environmental and human health consequences may be exacerbated by policy differences across political boundaries. To address this conundrum, legislation and policies dealing with Pb in electronics are first reviewed. A discussion of the current state of knowledge on alternative solder materials relative to product design, environmental performance, and risk assessment follows. Previous studies are reviewed, and consistent with their results, this analysis finds that there is great uncertainty in the trade-offs between Pb-based solders and proposed replacements. Bridging policy and knowledge gaps will require increased international cooperation on materials use, product market coverage, and e-waste EOL management. [source] Gelatin-based photopolymers for bone replacement materialsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2009Monika Schuster Abstract Gelatin-based monomers were considered as suitable base component for the 3D structuring of potential bone replacement materials by stereolithographic techniques. Different methacrylate-based gelatin derivatives were prepared, whereas a polyethylene glycol modified derivative GP4M turned out to have the highest tolerance toward other monomers. These are essential as they allow the tuning of the photoreactivity and the mechanical properties. Cell culture experiments with osteoblast- and endothelial-like cells confirmed negligible cytotoxicity of these monomers. Finally, we were able to show the possibility of producing arbitrary cellular structures with these gelatin-containing formulations using stereolithography. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009 [source] Evaluating the In Vitro and In Vivo Efficacy of Nano-Structured Polymers for Bladder Tissue Replacement ApplicationsMACROMOLECULAR BIOSCIENCE, Issue 5 2007Megan Pattison Abstract Bladder cancers requiring radical cystectomy, along with congenital and acquired disorders which result in obstruction of the bladder, necessitate surgical measures (including augmentation); such diagnoses bring a clinical need for effective bladder replacement implant designs. Many recent approaches for the design of soft tissue replacement materials have relied on the use of synthetic polymeric substances; unfortunately, the optimal soft tissue implant material is yet to be found. This may, in part, be because current polymeric formulations fail to sufficiently biomimic the neighboring bladder tissue. This study took a brand new approach in designing the next generation of tissue-engineered bladder constructs through the use of nanotechnology, or materials with nanometer (less than 100 nm) surface features. Results provided evidence that nano-structured polymeric scaffolds (specifically, PLGA and PU) created using chemical etching techniques are capable of enhancing the human bladder smooth muscle cell adhesion, proliferation, and the production of extracellular matrix (ECM) proteins. Preliminary in vivo results also speak to the usefulness of such nano-structured materials. In combination, these findings suggest that nano-dimensional PLGA and PU scaffolds are promising replacement materials for the human bladder wall. [source] Novel ceramic bone replacement material CeraBall® seeded with human mesenchymal stem cellsCLINICAL ORAL IMPLANTS RESEARCH, Issue 3 2010Timothy Douglas Abstract Objectives: Hydroxyapatite (HA) and tricalcium phosphate (TCP) are two very common ceramic materials for bone replacement. A recently developed material for bone replacement is CeraBall®, which is a mixed HA,TCP scaffold available as porous spherical scaffolds of diameter 4 and 6 mm. Before their use as bone replacement materials in vivo, in vitro testing of these scaffolds is necessary. The goal of this study was to characterise 4 and 6 mm CeraBall® scaffolds in vitro with a view to their future use as bone replacement materials. Materials and methods: The proliferation of human mesenchymal stromal cells (hMSCs) seeded on CeraBall® scaffolds was evaluated quantitatively using the WST [Water soluble tetrazolium ((4-[3-(4- Iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1, 3-benzene disulfonate)] test and qualitatively by scanning electron microscopy (SEM). In addition, the standard MTT [(3-(4, 5-Dimenthylthiazol-2-Y1)-2, 5-Diphenyltetrazolium bromide)] biocompatibility test and cell vitality staining were performed using hMSCs. CeraBall® scaffolds were also tested for their mechanical properties. Results: SEM and WST test results showed that hMSCs proliferated on CeraBall® scaffolds over the course of 9 days. Proliferation was similar to that seen on tissue culture polystyrene (control). Cells showed a well-spread morphology and formed ,sheets' on the surface of scaffolds. Invasion of pores was observed. Good biocompatibility was demonstrated by MTT test results and cell vitality staining. Scaffolds of both 4 and 6 mm were able to withstand compressive loads of 5 N. Conclusions: CeraBall® scaffolds show good biocompatibility in vitro for hMSCs. This opens the way for in vivo applications. To cite this article: Douglas T, Liu Q, Humpe A, Wiltfang J, Sivananthan S, Warnke PH. Novel ceramic bone replacement material CeraBall® seeded with human mesenchymal stem cells. Clin. Oral Impl. Res. 21, 2010; 262,267. doi: 10.1111/j.1600-0501.2009.01818.x [source] Time- and dose-dependent mitogenic effect of basic fibroblast growth factor combined with different bone graft materials: an in vitro studyCLINICAL ORAL IMPLANTS RESEARCH, Issue 5 2006Xanthippi E. Dereka Abstract Objectives: In periodontal regeneration, the growth factor concentrations and the delivery system used are of great importance. In an attempt to assess the mitogenic effect of basic fibroblast growth factor (bFGF) on periodontal ligament (PDL) cells combined with different bone replacement materials, two allografts of cortical (DFDBA) and cancellous (DFBA) bone and an anorganic bovine material with a synthetic peptide (ABM P-15) were used. The purpose of this study was to evaluate the in vitro mitogenic effect of different doses of bFGF alone or in combination with DFDBA, DFBA and ABM P-15 on human PDL cells in a time-dependent mode. Material and methods: PDL cell cultures were derived from the mid-root of four maxillary premolars. Cells were grown and reached confluence. On day 2 of quiescence, new medium was added along with (1) 1, 5, 10 and 25 ng/ml of bFGF alone, (2) 10 mg of DFDBA, DFBA and ABM P-15 alone and (3) their combination. The mitogenic effect was determined at 24 and 48 h of culture by using a hemocytometer chamber. The cells were counted under a phase contrast microscope. Results: The results revealed that bFGF at the highest concentrations and after 48 h exerted a significant mitogenic effect on PDL cells, and also DFDBA and DFBA supported cell proliferation. Furthermore, DFDBA and DFBA enriched with bFGF had a significant mitogenic effect after 48 h of culture. ABM P-15 with 10 and 25 ng/ml of bFGF up-regulated PDL cell proliferation after 48 h of incubation. Conclusions: The findings of this study demonstrate the beneficial role of bFGF combined with DFDBA and DFBA as carriers in periodontal repair. [source] | |||||||||||||