In vitro bioactivity of novel cured ionomer cement based on iron oxide

The effect of adding Fe₂O₃ on the bioactivity of cured ionomer cement was examined in simulated body fluid (SBF). Although the polyacrylic acid and Fe₂O₃ are known as inhibitors for apatite formation, results clearly show that exposure of the cement to the SBF lead to the formation of rough layers of carbonated-apatite (Volmer–Weber growth). Interestingly, the addition of Fe₂O₃ to the cement structure decreases the possibility of acid–base reaction in ionomer cements due to the improved chemical durability of the glass. Therefore, more calcium ions were released from the cement at the initial stage of soaking which plays an important role in forming the surface apatite layer by heterogeneous nucleation via the OH⁻ groups on the cement surface.     

In vitro apatite formation of calcium phosphate composite synthesized from fish bone

Calcium phosphate-based composite (CPC) is the main biomaterial substitute used for bone repair. Properties affecting bioactivity of this composite vary depending on the types of calcium phosphate crystalline phases. Hence, in this study, bioactivity behavior of novel CPC cement by the incorporation of calcium phosphate (CP), which was obtained from fish bones, dicalcium phosphate dehydrate, and chitosan solution, was monitored in simulated body fluid (SBF). In advance, the microstructure of CP produced by heat treatment (annealing) of fish bone was evaluated at two different temperatures 600 and 900°C. The X-ray diffraction (XRD) results showed that there was no secondary phase formation aside from natural hydroxyapatite (HA) in bones annealed; and the annealing process enhanced the crystallinity of CP phase in the bone matrix particularly when annealed at 900°C. After incubation of CPC cement in SBF, bone bonding ability and producing of biomimetic HA coat on the CPC cement surface were confirmed using XRD, fourier-transform infrared spectroscopy, and scanning electron microscopy. The analysis results show that needle-like and cauliflower apatite layer with the crystallite size about 100 nm was grown on the surface of CPC cement after 28 days incubation in SBF. Regardless of above findings, we conclude that varying the annealing temperature has tremendous effect on the production of natural HA from fish bone with required properties and the ultimate morphology of obtained CPC cements after soaking is directly depended on the degree of crystallinity of the prepared natural HA.     

Impact of chloride on the mineralogy of hydrated Portland cement systems

Chloride ion is in part bound into ordinary Portland cement paste and modifies its mineralogy. To understand this a literature review of its impacts has been made and new experimental data were obtained. Phase pure preparations of Friedel's salt, Ca₄Al₂(Cl)_1.95(OH)_12.05·4H₂O, and Kuzel's salt, Ca₄Al₂(Cl)(SO₄)_0.5(OH)₁₂·6H₂O, were synthesized and their solubilities were measured at 5, 25, 55 and 85 °C. After equilibration, solid phases were analysed by X-ray diffraction while the aqueous solutions were analysed by atomic absorption spectroscopy and ion chromatography. The solid solutions and interactions of Friedel's salt with other AFm phases were determined at 25 °C experimentally and by calculations. In hydrated cements, anion sites in AFm are potentially occupied by OH, SO₄ and CO₃ ions whereas Cl may be introduced under service conditions. Chloride readily displaces hydroxide, sulfate and carbonate in the AFm structures. A comprehensive picture of phase relations of AFm phases and their binding capacity for chloride is provided for pH ∼ 12 and 25 °C. The role of chloride in AFt formation and its relevance to corrosion of embedded steel are discussed in terms of calculated aqueous [Cl⁻]/[OH⁻] molar ratios.     

Study of alinite cement hydration by impedance spectroscopy

Two types of alinite cements, Mg-alinite and Zn-alinite, were synthesized using the reagent grade chemicals. Their hydration behavior was compared with ordinary Portland cement (OPC) using impedance spectroscopy (IS) and ²⁹Si nuclear magnetic resonance (NMR) spectroscopy. The bulk resistance in the IS spectra and the intensity ratio of the hydrous (Q₁ and Q₂) to anhydrous (Q₀) phases in the NMR spectra were estimated as the extent of hydration. The results obtained from both techniques were consistent each other. Mg-alinite had a comparable hydration rate to OPC and Zn-alinite exhibited faster hydration kinetics than Mg-alinite.     

Compressive strength and preliminary in vitro evaluation of gypsum and gypsum–polymer composites in protein-free SBF at 37 °C

Gypsum is a bioresorbable material that has been used in many applications such as tissue regeneration. Mechanical properties of gypsum have limited its applications to non-load bearing sites. The current study aimed at studying the compressive strength and behaviour of gypsum–polymer composites in protein-free simulated body fluids (SBF). Polymers studied were poly(vinyl alcohol) (PVA) and its copolymers with vinyl acetate and itaconic acid in addition to vinyl acetate and vinyl chloride. Composites with the highest compressive strength results were chosen for the preliminary in vitro evaluation in protein-free SBF solutions. Changes in the concentrations of Ca²⁺ and PO₄³⁻ ions, weight loss and morphology of the solid samples were monitored after soaking them in SBF and 1.5 SBF solutions. Results showed resorption of gypsum, concurrently with deposition of apatite in all composites, including polymer-free gypsum. Mechanical integrities of all samples were maintained, suggesting their stabilities when used as bone cements.     

Rheology of foamed cement

Foams are being used in a number of petroleum industry applications that exploit their high viscosity and low density. Foamed cement slurries can have superior displacement properties relative to non-foamed cement slurries. This article presents results of an experimental study of foamed cement rheology. Viscosity curves of foamed cements were obtained using a flow-through rotational viscometer. Foamed cements with different foam qualities were generated under different pressures using a foam generator/viscometer apparatus. The foam qualities during the tests ranged from 0% to 30%, and the shear rate varied between 5 s^− 1 and 600 s^− 1. Experimental results indicate that: i) unlike conventional aqueous foams, low-quality cement foams have a lower viscosity than the base fluid; ii) as the cement foam quality (gas volumetric fraction) increases from 10% to 30%, the viscosity also increases; and iii) the viscosity of low-quality cement foam slightly increases after depressurization or expansion.     

Investigation of biocompatible nanosized materials for development of strong calcium phosphate bone cement: Comparison of nano-titania,nano-silicon carbide and amorphous nano-silica

The present paper deals with the effect of adding SiC, TiO₂ and SiO₂ nanoparticles on setting time, mechanical strength and hydraulic reactions of calcium phosphate cements (CPCs). The initial and final setting times of CPC increased by adding both nano-SiC and nano-TiO₂ additives but decreased by using nano-silica. Nano-titania and nano-silica had great effect on compressive strength of as-set CPC whereas slight changes were found by using nano-SiC. Although a sharp increase in compressive strength of all cements was observed by soaking them in physiological solution, the soaked additive-free cements and nano-SiO₂-added ones exhibited the greatest strength values. The results showed that adding these nano-additives did not influence on conversion rate of cement reactants to apatite phase during soaking in physiological solution period but the morphology of the formed phase was almost different. Overall, the results determined that nano-SiO₂ and nano-TiO₂ particles were appropriate additives to improve short-term mechanical strength of CPCs a(s-set CPCs), though nano-SiO₂ was found more effective because it improves the long-term mechanical strength of CPC (after soaking) too.     

Aluminum-rich belite sulfoaluminate cements: Clinkering and early age hydration

Belite sulfoaluminate (BSA) cements have been proposed as environmentally friendly building materials, as their production may release up to 35% less CO₂ into the atmosphere when compared to ordinary Portland cements. Here, we discuss the laboratory production of three aluminum-rich BSA clinkers with nominal mineralogical compositions in the range C₂S (50-60%), C₄A₃$ (20-30%), CA (10%) and C₁₂A₇ (10%). Using thermogravimetry, differential thermal analysis, high temperature microscopy, and X-ray powder diffraction with Rietveld quantitative phase analysis, we found that burning for 15 min at 1350 ºC was the optimal procedure, in these experimental conditions, for obtaining the highest amount of C₄A₃$, i.e. a value as close as possible to the nominal composition. Under these experimental conditions, three different BSA clinkers, nominally with 20, 30 and 30 wt.% of C₄A₃$, had 19.6, 27.1 and 27.7 wt.%, C₄A₃$ respectively, as determined by Rietveld analysis. We also studied the complex hydration process of BSA cements prepared by mixing BSA clinkers and gypsum. We present a methodology to establish the phase assemblage evolution of BSA cement pastes with time, including amorphous phases and free water. The methodology is based on Rietveld quantitative phase analysis of synchrotron and laboratory X-ray powder diffraction data coupled with chemical constraints. A parallel calorimetric study is also reported. It is shown that the β-C₂S phase is more reactive in aluminum-rich BSA cements than in standard belite cements. On the other hand, C₄A₃$ reacts faster than the belite phases. The gypsum ratio in the cement is also shown to be an important factor in the phase evolution.     

Bone substitute of poly(amino acid)/β‐Ca2SiO4 biocomposite: Degradability and bioactivity

A poly(amino acid)/β‐Ca₂SiO₄(PAA/β‐Ca₂SiO₄) bioactive composite was prepared by in situ melting polymerization. The composition, structure, and morphology were characterized by infrared spectrometry, X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, and differential scanning calorimeter. The results indicated that the β‐Ca₂SiO₄ particles were uniformly distributed in the PAA matrix and some interaction was found at the interface between PAA and β‐Ca₂SiO₄. The crystallinity of PAA in the composite was found decreasing with the increase of β‐Ca₂SiO₄ content. The bioactivity of the composite was evaluated by soaking the composite in simulated body fluid (SBF) and results showed that the PAA/β‐Ca₂SiO₄ composite (PSC) could induce a dense and continuous layer of apatite after soaking for 1 week. In addition, the PSC was soaked SBF for 2 months, and the weight loss reached 8.77%, showing the composite could be degradable. Collectively, these results suggested that the incorporation of β‐Ca₂SiO₄ produced a biocomposite with enhanced bioactivity and might have potential applications as a bone tissue substitute. POLYM. COMPOS., 37:1335–1341, 2016. © 2014 Society of Plastics Engineers     

Evaluation of ascorbic acid-loaded calcium phosphate bone cements: Physical properties and in vitro release behavior

In this study, different concentrations of ascorbic acid (50, 100 and 200 µg/mL) were added to the liquid phase of a calcium phosphate cement (CPC). The cements were immersed in simulated body fluid (SBF) for different intervals and physical, physicochemical and mechanical properties of them were evaluated. The release of added ascorbic acid from CPCs into the SBF solution was also studied. From the results, both setting time and injectability of CPC decreased by adding ascorbic acid, however the compressive strength was sharply increased before soaking in SBF solution. But, the compressive strength values of all cements (with or without ascorbic acid) soaked in SBF solution for more than 7 d duration were comparable. The X-ray diffractometry results showed that in vitro apatite formation ability of cement reactants did not change by adding ascorbic acid. The scanning electron microscopy images indicated that morphology of the formed apatite crystals was nano-needlelike and needle diameter was less than 100 nm. The loaded ascorbic acid was slowly released from CPC into the SBF solution so that about 10% and 20% of the loaded drug was released after 504 h for the cements containing 100 and 200 µg/mL ascorbic acid, respectively. The release rate was increased when the amount of added ascorbic acid decreased by 50 µg/mL.     

Preparation and characterisation of calcium phosphate cement made by poly(acrylic/itaconic) acid

Abstract

In this study, the compressive strength and bioactivity of strong polymeric calcium phosphate cement (PCPC), made by mixing a calcium phosphate powder (a mixture of tetracalcium phosphate and dicalcium phosphate dihydrate) and an aqueous solution of poly(acrylic/itaconic) acid, were investigated. The characteristics of the cement such as phase composition, setting reaction products and microstructure were analysed and compared to those of a control sample made by the same solid phase and water as a liquid. The hard tissue healing capability of PCPC was tested in a rabbit model by radiographical observations of the healing process as well as the cement condition. The results showed that the compressive strength of the set PCPC was ~35 MPa before soaking in a simulated body fluid (SBF), which was much higher than that of the control specimen. However, it sharply decreased when the cement was immersed in the SBF. X-ray diffraction analysis revealed that tricalcium phosphate was formed in the set PCPC and only a small amount of hydroxyapatite was produced after seven days soaking. In contrast, hydroxyapatite was almost the only phase of the control specimen after the soaking period. Radiography tests showed a cement (PCPC) with an irregular macrostructure after three months implantation, with a decreased radiopacity, and without any periosteal or intercortical callus formation.     

Structure and mechanical properties of aluminosilicate geopolymer composites with Portland cement and its constituent minerals

The compressive strengths and structures of composites of aluminosilicate geopolymer with the synthetic cement minerals C₃S, β-C₂S, C₃A and commercial OPC were investigated. All the composites showed lower strengths than the geopolymer and OPC paste alone. X-ray diffraction, ²⁹Si and ²⁷Al MAS NMR and SEM/EDS observations indicate that hydration of the cement minerals and OPC is hindered in the presence of geopolymer, even though sufficient water was present in the mix for hydration to occur. In the absence of SEM evidence for the formation of an impervious layer around the cement mineral grains, the poor strength development is suggested to be due to the retarded development of C-S-H because of the preferential removal from the system of available Si because geopolymer formation is more rapid than the hydration of the cement minerals. This possibility is supported by experiments in which the rate of geopolymer formation is retarded by the substitution of potassium for sodium, by the reduction of the alkali content of the geopolymer paste or by the addition of borate. In all these cases the strength of the OPC-geopolymer composite was increased, particularly by the combination of the borate additive with the potassium geopolymer, producing an OPC-geopolymer composite stronger than hydrated OPC paste alone.     

Alumino-silicate polyacrylic acid and related cements

The composition and setting reaction of cements formed from aluminosilicates and poly(acrylic acid), the ASPA cements, are described. Setting and hardening results from interactions between specially-formulated, complex, fluorine-containing calcium aluminosilicate glasses and aqueous solution of poly(acrylic acid) or similar poly(alkenyl carboxylic acids). Protons from the polyacid penetrate the surface of the glass decomposing the negatively charged aluminosilicate network to a siliceous hydrogel and releasing Al³⁺, Ca²⁺ and F- ions. These ions migrate, probably as complexes, such as AlF₂₊, AlF²⁺ and CaF⁺, into the polyelectrolyte phase where they cross-link polyanionic chains, by ionic and possibly chelate binding, causing the cement to gel and set. Overall the reaction may be seen as one where flexible hydrogen bonds, in the liquid, are progressively replaced by more rigid ionic ones, leading to gelation. The set cement is a composite of glass particles sheathed by a silica gel bound by a metal poly anionic matrix. ASPA cements can attain a compressive strength of 200 N/mm² in 24 h and are adhesive under oral conditions to tooth materials. They find a number of applications in conservative and preventive dentistry. Certain naturally-occurring aluminosilicate minerals react with poly(acrylic acid) to form cement but these are much weaker (not exceeding a compressive strength of 30 N/mm²) and are weakened by water.     

Characterization by solid-state NMR and selective dissolution techniques of anhydrous and hydrated CEM V cement pastes

The long term behaviour of cement based materials is strongly dependent on the paste microstructure and also on the internal chemistry. A CEM V blended cement containing pulverised fly ash (PFA) and blastfurnace slag (BFS) has been studied in order to understand hydration processes which influence the paste microstructure. Solid-state NMR spectroscopy with complementary X-ray diffraction analysis and selective dissolution techniques have been used for the characterization of the various phases (C₃S, C₂S, C₃A and C₄AF) of the clinker and additives and then for estimation of the degree of hydration of these same phases. Their quantification after simulation of experimental ²⁹Si and ²⁷Al MAS NMR spectra has allowed us to follow the hydration of recent (28 days) and old (10 years) samples that constitutes a basis of experimental data for the prediction of hydration model.     

Microscopic and spectroscopic evidences for multiple ion-exchange reactions controlling biomineralization of CaO.MgO.2SiO2 nanoceramics

This study is focused on the mechanism of in vitro biomineralization on the surface of CaO.MgO.2SiO₂ (diopside) nanostructured coatings by scanning electron microscopy, energy-dispersive X-ray spectroscopy and inductively coupled plasma spectroscopy assessments. A homogeneous diopside coating of almost 2 µm in thickness was deposited on a medical-grade stainless steel by coprecipitation, dipping and sintering sequences. After soaking the sample in a simulated body fluid (SBF) for 14 days, a layer with the thickness of 8 µm is recognized to be substituted for the primary diopside deposit, suggesting the mineralization of apatite on the surface. Investigations revealed that the newly-formed layer is predominantly composed of Ca, P and Si, albeit with a biased accumulations of P and Si towards the surface and substrate, respectively. The variations in the ionic composition and pH of the SBF due to the incubation of the sample were also correlated with the above-interpreted biomineralization. In conclusion, the multiple ion-exchange reactions related to Ca, Mg, Si and P were found to be responsible for the in vitro bioactivity of nanodiopside.     

Physical and physicochemical evaluation of calcium phosphate cement made using human derived blood plasma

Abstract

In the present work, calcium phosphate cement was made by mixing a solid phase and blood plasma as liquid phase. The basic properties of the cement (called BPC) were compared with those of conventional calcium phosphate cement (c-CPC) where distilled water was used as liquid. BPC had better consistency and injectability than c-CPC but longer setting time. In both cements, the reactants were converted into apatite phase after immersing in simulated body fluid but the phase formed in BPC had lower crystallinity than the phase formed in c-CPC. The set BPC was stronger than c-CPC, having a compressive strength (CS) of about 2–6 MPa after 24 h incubation at 37°C. The CS reduced during soaking at early stage but was relatively improved at the end of soaking period (day 7). In contrast, an increase in CS was observed in c-CPC during soaking period.     

Preparation and in vitro degradation of novel bioactive polylactide/wollastonite scaffolds

Composite scaffolds for applications in bone engineering from poly(D,L ‐lactide) (PDLLA) incorporated with different proportional bioactive wollastonite powders were prepared through a salt‐leaching method, using NH₄HCO₃ as porogen. The pore structures and morphology of the scaffolds were determined by scanning electron microscopy (SEM). The bioactivity of composite materials was evaluated by examining its ability to initiate the formation of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂)(HAp) on its surface when immersed in simulated body fluids (SBF). The in vitro degradation behaviors of these scaffolds were systematically monitored at varying time periods of 1, 2, 4, 6, 8, 11, 14, 17, 20, 24, and 28 weeks postimmersion in SBF at 37°C. FT‐IR, XPS, XRD, and SEM measurements revealed that hydroxyapatite commenced to form on the surface of the scaffolds after 7 days of immersion in SBF. The measurements of weight loss, pH, and molecular weight of the samples indicated that PDLLA/wollastonite composite scaffolds degraded slower than the pure PDLLA scaffolds do. Addition of wollastonite enhanced the mechanical property of the composite scaffolds. The in vitro osteoblast culture experiment confirmed the biocompatibility of the scaffold for the growth of osteo‐blasts. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009.     

Temperature dependence, 0 to 40 °C, of the mineralogy of Portland cement paste in the presence of calcium carbonate

Thermodynamic calculations disclose that significant changes of the AFm and AFt phases and amount of Ca(OH)₂ occur between 0 and 40 °C; the changes are affected by added calcite. Hydrogarnet, C₃AH₆, is destabilised at low carbonate contents and/or low temperatures < 8 °C and is unlikely to form in calcite-saturated Portland cement compositions cured at < 40 °C. The AFm phase actually consists of several structurally-related compositions which form incomplete solid solutions. The AFt phase is close to its ideal stoichiometry at 25 °C but at low temperatures, < 20 °C, extensive solid solutions occur with CO₃-ettringite. A nomenclature scheme is proposed and AFm-AFt phase relations are presented in isothermal sections at 5, 25 and 40 °C. The AFt and AFm phase relations are depicted in terms of competition between OH, CO₃ and SO₄ for anion sites. Diagrams are presented showing how changing temperatures affect the volume of the solid phases with implications for space filling by the paste. Specimen calculations are related to regimes likely to occur in commercial cements and suggestions are made for testing thermal impacts on cement properties by defining four regimes. It is concluded that calculation provides a rapid and effective tool for exploring the response of cement systems to changing composition and temperature and to optimise cement performance.     

Structural role of titanium on slag properties

The presence of titanium in ground granulated blast-furnace slags (GGBS) has been suspected to modify cement properties. This study provides the first evidence of a relation between the TiO₂ content of slags and the mechanical properties of mortars based on slag cements. It is observed that only the slags containing less than 1%TiO₂ show a compressive strength at 28 days that remains within the 52.5 MPa norm with CEM III cements complying with the European Standard NF EN 197-1. The structural origin of this chemical dependence of the performance of cements is investigated by determining directly the titanium speciation in various European slags by spectroscopic methods. Electron paramagnetic resonance indicates that about 76% of Ti in slag occurs as Ti⁴⁺. The atomic structure around Ti was determined by Ti K-edge X-ray absorption near edge structure, which shows that Ti is mainly five-fold coordinated in square-based pyramid geometry. Five coordinated Ti acts as network-stabilizer of the silicate network as it increases the polymerization. Requiring Ca²⁺ for charge-compensation of the titanyl bond, it reduces the availability of Ca²⁺ during glass alteration in a modified random model of glass structure, where Ca²⁺ atoms are clustered in percolating cationic domains. As a consequence, the presence of five-coordinated Ti results in a slower dissolution of the slag. These peculiar structural properties of titanium may explain the detrimental role of Ti above a 1% concentration, for many physical and chemical slag properties. This work provides a scientific ground for the technological acceptability of the upper limit of the Ti-content of GGBS.     

Magnetic and bioactive properties of MnO2/Fe2O3 modified Na2O-CaO-P2O5-SiO2 glasses and nanocrystalline glass-ceramics

Glass and in-situ nanocrystalline glass-ceramics of compositions 45SiO₂-25CaO-10Na₂O-5P₂O₅-xFe₂O₃-(15-x) MnO₂ are investigated for their magnetic and in-vitro bioactive properties. The ferrimagnetic character is observed in the high Fe₂O₃ containing in-situ nanocrystalline glass-ceramics. Saturation magnetization and coercivity increases with Fe₂O₃. After soaking in the simulated body fluid (SBF), the powdered as well as the bulk glasses and glass-ceramics are investigated using various characterization techniques. The presence of MnO₂ increases the leaching of Na⁺ ions from the glasses and also attracts the Ca²⁺ cations from the SBF as compared to Fe₂O₃ containing nano-crystalline glass-ceramics. It also increases the tendency to form hydroxyl apatite (HAp) layer. Microwave Plasma Atomic Emission Spectroscopy (MP-AES), Fourier Transform Infrared (FTIR) spectra, X-ray diffraction and Scanning electron micrographs (SEM) after soaking in the SBF confirm the HAp formation on the surface of all the glasses and glass-ceramics. Urbach energy also indicates the structural modifications on the surfaces of the glass and glass-ceramics after soaking in the SBF.