Beta-tricalcium phosphate ceramic as a bone substitute in orthopaedic surgery.
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Synthetic beta-tricalcium phosphate ceramic (Biosorb, S.B.M., Lourdes, France) was used as a bone substitute in 110 patients whose mean age was 48 (14-83) years. There was a wide spectrum of indications, and the material was used alone in 86, combined with a corticocancellous bone autograft in 22, and combined with a corticocancellous allograft in two. The patients were assessed clinically and radiographically. Incorporation of the ceramic was excellent in 30, good in 51, and fair in 26. There were no poor results. In three patients the implanted material was removed because of infection. Incorporation was good or excellent in about 75% of all 110 patients. We consider beta-tricalcium phosphate ceramic to be the substitute of choice for medium-sized bone defects. (+info)
The effect of seed crystals of hydroxyapatite and brushite on the crystallization of calcium oxalate in undiluted human urine in vitro: implications for urinary stone pathogenesis.
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BACKGROUND: The aim of this study was to determine whether crystals of hydroxyapatite (HA) or brushite (BR) formed in urine promote the epitaxial deposition of calcium oxalate (CaOx) from undiluted human urine in vitro and thereby explain the occurrence of phosphate in the core of urinary stones consisting predominantly of CaOx. MATERIALS AND METHODS: Crystals of HA, BR, and CaOx were generated from human urine and their identity confirmed by X-ray analysis. Standard quantities of each crystal were then added to separate aliquots of pooled undiluted human urine and CaOx crystallization was induced by the addition of identical loads of sodium oxalate. Crystallization was monitored by Coulter Counter and (14) C-oxalate analysis and the precipitated crystals were examined by scanning electron microscopy. RESULTS: In comparison with the control to which no seeds were added, addition of CaOx crystals increased the deposition of (14) C-oxalate by 23%. On the other hand, seeds of HA and BR had no effect. These findings were supported by Coulter Counter analysis, which showed that the average modal sizes of crystal particles precipitated in the presence of HA and BR seeds were indistinguishable from those in the control, whereas those deposited in the presence of CaOx were significantly larger. Scanning electron microscopy confirmed these results, demonstrating that large aggregates of CaOx dihydrates were formed in the presence of CaOx seeds, whereas BR and to a lesser extent HA seeds were scattered free on the filtration membrane and attached like barnacles on the surface of the freshly precipitated CaOx crystals. CONCLUSION: Seed crystals of HA or BR do not promote CaOx deposition in urine in vitro and are therefore unlikely to influence CaOx crystal formation under physiologic conditions. However, binding of HA and BR crystals to, and their subsequent enclosure within, actively growing CaOx crystals might occur in vivo, thereby explaining the occurrence of mixed oxalate/phosphate stones. (+info)
Calcium phosphate nanoparticles induce mucosal immunity and protection against herpes simplex virus type 2.
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Previously we reported that calcium phosphate nanoparticles (CAP) represented a superior alternative to alum adjuvants in mice immunized with viral protein. Additionally, we showed that CAP was safe and elicited no detectable immunoglobulin E (IgE) response. In this study, we demonstrated that following mucosal delivery of herpes simplex virus type 2 (HSV-2) antigen with CAP, CAP adjuvant enhanced protective systemic and mucosal immunity versus live virus. Mice were immunized intravaginally and intranasally with HSV-2 protein plus CAP adjuvant (HSV-2+CAP), CAP alone, phosphate-buffered saline, or HSV-2 alone. HSV-2+CAP induced HSV-specific mucosal IgA and IgG and concurrently enhanced systemic IgG responses. Our results demonstrate the potency of CAP as a mucosal adjuvant. Furthermore, we show that systemic immunity could be induced via the mucosal route following inoculation with CAP-based vaccine. Moreover, neutralizing antibodies were found in the sera of mice immunized intranasally or intravaginally with HSV-2+CAP. Also, the results of our in vivo experiments indicated that mice vaccinated with HSV-2+CAP were protected against live HSV-2 infection. In conclusion, these preclinical data support the hypothesis that CAP may be an effective mucosal adjuvant that protects against viral infection. (+info)
Surface-layer modification of hydroxyapatite ceramic with acid and heat treatments.
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The purpose of this study was to examine or characterize the surface layer of a calcium phosphate ceramic with a gradual compositional change from alpha-tricalcium phosphate (alpha-TCP) on the surface to hydroxyapatite (HAP) on the inside. The surface of a dense HAP ceramic was acid-treated for 1 hour with orthophosphoric acid (H3PO4) solutions of several concentrations (0.5, 1.0 and 5.0 mol/L) or a buffered solution (pH 4.0) consisting of phosphate solutions. After acid treatment, specimens were heat-treated at 1,250 degrees C for 1 hour. X-ray photoelectron spectroscopy revealed that the compositional gradient layer could be modified on the surface of the HAP ceramic with all acid and heat treatments, and that 5.0 mol/L H3PO4 solution and heat treatments had a maximal thickness of approximately 2 microm for the surface-modified layer. It was confirmed that the outermost layer of HAP ceramics modified with the treatments, except 5.0 mol/L H3PO4 solution, showed a compound such alpha-TCP. (+info)
Supragingival calculus: formation and control.
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Dental calculus is composed of inorganic components and organic matrix. Brushite, dicalcium phosphate dihydrate, octacalcium phosphate, hydroxyapatite, and whitlockite form the mineral part of dental calculus. Salivary proteins selectively adsorb on the tooth surface to form an acquired pellicle. It is followed by the adherence of various oral micro-organisms. Fimbriae, flagella, and some other surface proteins are essential for microbial adherence. Microbial co-aggregation and co-adhesion enable some micro-organisms, which are incapable of adhering, to adhere to the pellicle-coated tooth surface. Once organisms attach to the tooth surface, new genes could be expressed so that mature dental plaque can form and biofilm bacteria assume increased resistance to antimicrobial agents. Supersaturation of saliva and plaque fluid with respect to calcium phosphates is the driving force for plaque mineralization. Both salivary flow rate and plaque pH appear to influence the saturation degree of calcium phosphates. Acidic phospholipids and specific proteolipids present in cell membranes play a key role in microbial mineralization. The roles of crystal growth inhibitors, promoters, and organic acids in calculus formation are discussed. Application of biofilm culture systems in plaque mineralization is concisely reviewed. Anti-calculus agents used--centering on triclosan plus polyvinyl methyl ether/maleic acid copolymer, pyrophosphate plus polyvinyl methyl ether/maleic acid copolymer, and zinc ion-in commercial dentifrices are also discussed in this paper. (+info)
Production of amines in equine cecal contents in an in vitro model of carbohydrate overload.
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Acute laminitis can be induced experimentally in horses by the administration of carbohydrate, resulting in fermentation within the cecum and ischemia-reperfusion of the digits. The products of fermentation that trigger acute laminitis are as yet unknown; however, compounds such as amines might play a role due to their potential vasoactive properties. The objectives of this study were to quantify the amines present in equine cecal contents and to use a model of carbohydrate overload in vitro to test the hypothesis that carbohydrate fermentation is associated with increased amine production. Cecal contents from each horse were divided into aliquots and incubated anaerobically with either cornstarch or inulin (a form of fructan carbohydrate; both 1 g/100 mL). The pH was measured and samples were taken at the same time for amine measurement by HPLC at 2-h intervals over a 24-h period. In a second set of experiments, the effects of the antibiotic virginiamycin (1 mg/100 mL), calcium (CaPO4; 0.3 g/100 mL), and plant steroidal saponin (Yucca schidigera extract; 0.1 g/100 mL) were examined on pH and amine concentrations in cecal contents incubated with starch or inulin. Both starch and inulin caused significant time-dependent falls in pH, from 6.7 +/- 0.1 at 0 h to 5.2 +/- 0.1 (starch) and 5.0 +/- 0.1 (inulin) at 24 h. Fermentation of carbohydrate was also associated with increased production of phenylethylamine and isoamylamine (two- to threefold increases) as well as putrescine and cadaverine (1.5- to twofold increases). Virginiamycin inhibited the fall in pH and increases in production of phenylethylamine and isoamylamine, while calcium phosphate moderated the changes in pH only. Yucca schidigera extract was without effect. These data show that fermentation of carbohydrate by equine cecal microbiota may lead to increased production of amines. (+info)
Minimal internal fixation and calcium-phosphate cement in the treatment of fractures of the tibial plateau. A pilot study.
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We used calcium-phosphate cement combined with minimal internal fixation to treat 49 fractures of the lateral tibial plateau. There were 25 split depression fractures, 22 pure depression fractures and two bicondylar fractures. Anatomical reduction was obtained in 38 fractures, satisfactory reduction in nine and imperfect reduction in two. Of 44 patients reviewed at one year, 33 were rated as having an excellent reduction. Functional outcome as measured by the Rasmussen score was good or excellent at six months in 92% (44/48) of patients and in 95% (42/44) at one year. Eight (16%) showed some loss of reduction of the plateau. In seven of these the loss of reduction was slight (<3 mm) and no action was taken. One patient with a deep infection had gross loss of reduction and a poor functional outcome. Calcium-phosphate cement is a useful alternative to bone grafting for the treatment of fractures of the tibial plateau. (+info)
Calcified nanostructured silicon wafer surfaces for biosensing: effects of surface modification on bioactivity.
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The growth of known biologically-relevant mineral phases on semiconducting surfaces is one strategy to explicitly induce bioactivity in such materials, either for sensing or drug delivery applications. In this work, we describe the use of a spark ablation process to fabricate deliberate patterns of Ca(10)(PO4)6(OH)2 on crystalline Si (calcified nanoporous silicon). These patterns have been principally characterized by scanning electron microscopy in conjunction with elemental characterization by energy dispersive x-ray analysis. This is followed by a detailed comparison of the effects of fibroblast adhesion and proliferation onto calcified nanoporous Si, calcified nanoporous Si derivatized with alendronate, as well as control samples of an identical surface area containing porous SiO2. Fibroblast adhesion and proliferation assays demonstrate that a higher density of cells grow on the Ca3(PO4)2/porous Si/SiO2 structures relative to the alendronate-modified surfaces and porous Si/SiO2 samples. (+info)