Bioactive Filler Research Articles

Enhanced osteointegration of poly(methylmethacrylate) bone cements by incorporating strontium-containing borate bioactive glass.

Although poly(methylmethacrylate) (PMMA) cements are widely used in orthopaedics, they have numerous drawbacks. This study aimed to improve their bioactivity and osseointegration by incorporating strontium-containing borate bioactive glass (SrBG) as the reinforcement phase and bioactive filler of PMMA cement. The prepared SrBG/PMMA composite cements showed significantly decreased polymerization temperature when compared with PMMA and retained properties of appropriate setting time and high mechanical strength. The bioactivity of SrBG/PMMA composite cements was confirmed in vitro, evidenced by ion release (Ca, P, B and Sr) from SrBG particles. The cellular responses of MC3T3-E1 cells in vitro demonstrated that SrBG incorporation could promote adhesion, migration, proliferation and collagen secretion of cells. Furthermore, our in vivo investigation revealed that SrBG/PMMA composite cements presented better osseointegration than PMMA bone cement. SrBG in the composite cement could stimulate new-bone formation around the interface between the composite cement and host bone at eight and 12 weeks post-implantation, whereas PMMA bone cement only stimulated development of an intervening connective tissue layer. Consequently, the SrBG/PMMA composite cement may be a better alternative to PMMA cement in clinical applications and has promising orthopaedic applications by minimal invasive surgery.

Bacterial adhesion not inhibited by ion-releasing bioactive glass filler

ObjectiveBioactive glasses and surface pre-reacted glass-ionomer (sPRG) filler possess cariostatic properties owing to ion release. Many studies investigated potential cariostatic effects; few studies evaluated the surface stability and the structural changes their surfaces undergo in acidic conditions. MethodsThe surface resistance against acid attack and the surface receptiveness for bacterial adhesion and biofilm formation of a sPRG-filled (Beautifil ll, Shofu) and conventional glass-filled (Herculite XRV Ultra, Kerr) resin-based composite (RBC), and a conventional glass-ionomer cement (GIC; Fuji IX GP Extra, GC) were examined. Specimens (n=3) were immersed in distilled water or lactic acid (pH 4.0) for 3 days. Bacterial growth and biofilm formation were recorded using optical density and SEM. ResultsUpon 3-day immersion in lactic acid, the surface of the sPRG-filled RBC revealed multiple holes, while virtually no change in surface integrity was observed for the conventional RBC and GIC. Bacterial growth measurements revealed that none of the materials inhibited Streptococcus mutans (p<0.05). Remarkably, cross-sectional SEM revealed that S. mutans had penetrated the etch pits induced by lactic acid in/around the sPRG filler. Ion-release measurements revealed that sPRG-filled RBC released boron and fluoride, while GIC only released fluoride. However, the concentration of ions released by both materials appeared not sufficient to inhibit bacterial growth. Moreover, the structural surface change and resultant increased surface roughness appeared to have promoted biofilm formation. SignificanceWhile having bioactive potential through ion release, the stability of surface integrity of bioactive materials is a key-parameter to be assessed with regard to their cariostatic potential.

Silica-based bioactive solids obtained from modified diatomaceous earth to be used as antimicrobial filler material

It is well known that microbiological spoilage in indoor surfaces has a negative impact on human health. Antimicrobial functionalized materials are intensely studied. The present work seeks the synthesis of eco-friendly and cheap bioactive hybrid filler from diatomaceous earth (DE). The activation method used proved to be efficient to enhance the amount of quaternary ammonium groups supported by DE which was corroborated by spectroscopic methods and the thermogravimetry analysis. Zeta potential measurements reviled a bilayer arrangement of the ammonium groups on the functionalized solids and the bioassays showed their antimicrobial activity.

Antimicrobial activity of ethylene-vinyl acetate containing bioactive filler against oral bacteria.

We developed an ethylene vinyl acetate (EVA) containing surface pre-reacted glass-ionomer (S-PRG) filler, as a new mouthguard material for preventing intraoral bacterial infection. We examined its physical properties, antimicrobial activity against a major cariogenic bacterium Streptococcus mutans and a periodontopathogen Porphyromonas gingivalis, and its cytotoxicity toward human gingival epithelial cells. S-PRG filler was added to EVA copolymer at 5, 10, 20, or 40 wt% and was processed into disc-shaped test specimens. Only minor differences between the Shore hardness and rebound resilience properties of EVA materials with and without the S-PRG filler were observed. The specimens with S-PRG filler showed bacteriostatic activity toward S. mutans and P. gingivalis and inhibited S. mutans biofilm formation. No cytotoxicity against the gingival epithelial cells was observed. Our findings show that EVA containing S-PRG filler has antimicrobial activity toward pathogenic oral bacteria and may be an effective material for maintaining the oral health of athletes.

Yolk shell nanocomposite particles as bioactive bone fillers and growth factor carriers.

The efficient delivery of bioactive molecules via rationally designed nanoparticles is an important focus in regenerative medicine. The yolk shell nanocomposite particles described herein are composed of silk fibroin movable cores formed within voided calcium carbonate shells to load and control the release of labile cytokines. These particles are excellent carrier vehicles of potent molecules as they sustained the release of bioactive Bone Morphogenetic Protein 2 (BMP-2) for more than 28 days in vitro. Implantation into bone defects in rabbits corroborates the in vitro results and also reveals that upon contact with phosphate containing body fluids, implanted yolk shell particles agglomerate and transform into a filler that adapts to defect contour to further act as an absorbable hemostatic agent. Taken together, the fabrication of these yolk shell particle-based "bone fillers" could expand the horizon for the development of newer generations of advanced bioactive materials in tissue regeneration applications.

Synthesis and characterization of novel in-situ grafted bioactive dental fillers

Synthesis and characterization of novel in-situ grafted bioactive dental fillers

Mechanical properties and in vivo study of modified-hydroxyapatite/polyetheretherketone biocomposites

Polyether ether ketone (PEEK) has received much attention for its excellent mechanical properties and biocompatibility. Here, the silane coupling agent KH560 [γ-(2,3-epoxypropoxy)propyltrimethoxysilane] is used for graft modification of bioactive HA (hydroxyapatite) particles and for preparing HA/PEEK composites via a hot-press molding method. The prepared HA/PEEK composites were tested for their mechanical properties with SEM (scanning electron microscopy), infrared spectroscopy, and thermo-analysis. The results show that silane coupling KH-560 modifies HA successfully and that the tensile strengths of HA/PEEK and m-HA/PEEK composites indicate an increasing and then a decreasing tendency with increasing HA contents. The non-modified HA/PEEK composites display the same trend as the modified specimens with lower tensile strength and consist of sharp points. When the HA content is 5wt.%, the tensile strength of m-HA/PEEK composite reaches its maximum, which is 23% higher than that of pure PEEK specimens. The in vivo experiments of m-HA/PEEK used a biomechanical push-out test, SEM, optical microscopy, and an Image-Pro Express C image analysis system. The growth of the bone tissues around the m-HA/PEEK composites with an HA content of 5wt.% is better than that of specimens with different HA contents. This finding shows the nano-scale effect of the bioactive filler HA in PEEK substrates, which obviously contributes to the growth of the surrounding bone issues in vivo. This study could provide theoretical support for the further promotion and application of high-performance engineering plastics such as PEEK in biomedical fields.

Influence of bioactive particles on the chemical-mechanical properties of experimental enamel resin infiltrants.

This study aimed at evaluating the chemophysical properties of experimental resin infiltrants (ERIs) doped with different bioactive particles. A control resin infiltrant (CR) was formulated using triethylene glycol dimethacrylate (TEGDMA) and ethoxylated bisphenol A dimethacrylate (BisEMA). Moreover, five experimental ERIs were also created by incorporating the following bioactive fillers (10wt%) into the CR: hydroxyapatite (Hap), amorphous calcium phosphate (ACP), zinc-polycarboxylated bioactive glass (BAG-Zn), bioactive glass 45S5 (BAG 45S5), and calcium silicate modified with beta tricalcium phosphate (β-TCP). ICON® resin infiltrant was also used as control. All the ERIs used in this study were assessed for degree of conversion (DC), Knoop microhardness (KHN), softening ratio (SR), tensile cohesive strength (TCS), modulus of elasticity (E-modulus), water sorption (WS), and solubility (SL). Data were subjected to ANOVA and Tukey's test (α=5%). ICON® presented the lowest DC, KHN, TCS, E-modulus, and SR. Incorporation of bioactive fillers into CR caused significant increase in the KHN. Conversely, no significant effect was observed on DC, TCS, and E-modulus. The resin infiltrant containing Hap showed a significant increase in softening ratio, while, ICON® presented the highest WS and SL. The WS of ACP-doped resin infiltrant was significantly higher than that of the Hap-doped infiltrant. The SL of the ACP-doped infiltrant was higher than CR BAG-Zn or BAG 45S5. The incorporation of bioactive particles into experimental resin infiltrants can improve the chemomechanical properties and reduce water sorption and solubility. Resin infiltrants doped with bioactive particles may improve the long-term performance of the treatment of white-spot lesions.

Effect of Mg content on the thermal stability and mechanical behaviour of PLLA/Mg composites processed by hot extrusion

In the field of bioabsorbable composites for biomedical applications, extrusion has been employed as a method to prepare homogeneous blends of polymeric matrices with bioactive ceramic fillers. In this work, the suitability of processing poly-l-lactic acid/Magnesium (PLLA/Mg) composites by hot extrusion has been assessed by a systematic characterization of PLLA/Mg composites containing different amounts of Mg particles up to 7wt%. The results show that extrusion causes a reduction of almost 20% in the viscosity average molecular weight of PLLA, which further decreases with increasing Mg content. Extrusion gave always rise to a homogeneous distribution of Mg particles within the PLLA matrix. This composite processing was not compromised by the degradation of the polymeric matrix because the processing temperature was always below the onset degradation temperature. In the processing conditions employed in the present work, degradation of the composite slightly increases as more Mg is added up to 5wt%, but is very high at 7wt%. This was also evident from the mechanical behaviour, so that Mg particles improved the stiffness and compression strength of neat PLLA until 5wt% of Mg content, which dropped drastically when the material had 7wt% of Mg. The filler strengthening factor decreases with the increment in Mg content. In order to obtain an optimised contribution of Mg particles, a balance between thermal degradation and mechanical resistance of PLLA must be achieved.

Improving the degradation behavior and in vitro biological property of nano-hydroxyapatite surface- grafted with the assist of citric acid

To obtain ideal nano-hydroxyapatite(n-HA) filler for poly(lactide-co-glycolide) (PLGA), a new surface-grafting with the assist of citric acid for nano-hydroxyapatite (n-HA) was designed, and the effect of n-HA surface-grafted with or without citric acid on in vitro degradation behavior and cells viability was studied by the experiments of soaking in simulated body fluid (SBF) and incubating with human osteoblast-like cells (MG-63). The change of pH value, tensile strength reduction, the surface deposits, cells attachment and proliferation of samples during the soaking and incubation were investigated by means of pH meter, electromechanical universal tester, scanning electron microscope (SEM) coupled with energy-dispersive spectro-scopy (EDS), fluorescence microscope and MTT method. The results showed that the introduction of citric acid not only delayed the strength reduction during the degradation by inhibiting the detachment of n-HA from PLGA, but also endowed it better cell attachment and proliferation, suggesting that the n-HA surface-grafted with the assist of citric acid was an important bioactive ceramic fillers for PLGA used as bone materials.

A review on electrospun polymer nanostructures as advanced bioactive platforms

This review article deals with latest literature studies on the potential use of polymer ultrathin and nanosized structures obtained by electrospinning to design novel engineered materials with bioactive properties. The electrofluidodynamic process offers the option to form high-performance bioactive systems based on polymer yarns of nanofibers or coatings of nanobeads with high surface-to-volume ratios. The electrospun and electrosprayed nanostructures can be further functionalized by encapsulation with bioactive fillers and substances. For both scenarios, the resultant polymer nanostructures present unique bioactive properties capable of providing a beneficial impact over human's health and with improved and advanced performance for biomedicine, pharmaceutics, nutrition, bioengineering, and healthcare applications. These novel functional materials attained by the electrospinning technology can be of interest for many bioactive applications such as functional food design, food packaging, functional coatings, controlled delivery of drug solutions and, mainly, tissue engineering. This article is purposely designed to gather, for the first time, most recent and promising multi- and inter-disciplinary developments based on electrospun systems for bioactive applications, which are either bioactive material concepts or can be advantageously applied to become such. POLYM. ENG. SCI., 56:500–527, 2016. © 2016 Society of Plastics Engineers

Hydroxyapatite formation on bioglass-containing bone void filler

Event Abstract Back to Event Hydroxyapatite formation on bioglass-containing bone void filler Chloë Goldbach1, Meryem Demir1, Kyle Glassman1 and Greg Pomrink1 1 NovaBone Products, Research & Development, United States Purpose: A study was conducted in order to determine whether or not hydroxyapatite would form on a bone void filler containing bioactive glass. Hydroxyapatite (HAp) forms the predominant mineral component of vertebrate bone and tooth enamel[1]. Bioactive glass interacts with ions in the body to form HAp layers on the surface of the glass; the similarity of this surface to naturally occurring hydroxyapatite provides optimal conditions for new bone formation[2]. In this study, a bone void filler containing bioactive glass was immersed in simulated body fluid (SBF)[3][4][5] for a period of 24 hours to initiate hydroxyapatite formation. Vioxx and Mo-Sci bioactive glass were used as positive controls since various Vioxx size distributions are present in the bone void filler and Mo-Sci is competitor material. Stainless steel and borosilicate spheres (McMaster Carr) were used as negative controls since these samples had spherical morphology similar to the bioactive glasses with the exception of having smooth surfaces and borosilicate is similar to bioatcive glass in terms of material composition. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) micrographs were used to detect HAp presence; characteristic FTIR bands for HAp are seen between 560 and 610 cm-1[1] and SEM micrographs allowed for qualitative assessment of crystalline morphology. FTIR spectra and SEM micrographs indicated HAp formation for the bioactive glass-containing bone void filler. Methods: Each sample was immersed in SBF at 37⁰C at 175 RPM for 24 hours to propagate HAp formation. Following immersion, samples were dried with acetone to halt surface reactions and prevent additional HAp formation. FTIR spectra were obtained using the Nicolet iS10 FTIR with Smart Orbit ATR and diffuse reflectance stage; spectra were collected from 400cm-1 to 2000cm-1 with 64 scans and automatic background subtraction. The SEM Hitachi SU5000 (University of Florida, Gainesville, FL) was implemented for obtaining SEM micrographs at magnifications ranging from 3 to 500µm. Results: A sample size of n=3 was assessed for FTIR. A sample size of n=1 or 2 was assessed for SEM; multiple micrographs were taken at various magnifications and negative controls were only assessed following immersion. Figure 1 displays the FTIR for one positive control (Vioxx, 90-710µm particle size), one negative control (borosilicate spheres, 0.094 in diameter), and the bone void filler test sample; both bone putty samples displayed were immersed in SBF while the two control materials are compared before and after immersion. The FTIR spectra show HAp formation for the Vioxx glass and the bone void fillers following immersion, as indicated by spectral peaks around 600 cm-1. Figure 2 displays the SEM micrographs for the Vioxx glass (90-710µm particle size) before and after immersion and the stainless steel, borosilicate, and two bone void filler samples following immersion; micrographs for negative controls prior to immersion were not captured. The SEM micrographs display HAp formation for the Vioxx glass and bone void filler samples following SBF immersion; HAp is not present on Vioxx prior to SBF immersion or on the borosilicate and stainless steel samples following immersion. Figure 1: From top to bottom: Plots 1 and 2 are Vioxx glass prior to and following immersion, 3 and 4 are borosilicate prior to and following immersion, and 5 and 6 are two bone void fillers following immersion Figure 2: The top two SEM micrographs represent Vioxx prior to (left) and following immersion (right); the middle images represent stainless steel (left) and borosilicate following immersion; the bottom images represent the two bone void filler samples following immersion Conclusions: Immersing a bone void filler containing bioactive glass in SBF resulted in HAp formation as detected using FTIR and SEM; the positive control materials exhibited HAp formation and the negative controls did not express HAp, as expected. The formation of HAp indicates that the bone void filler is a bioactive device. A next step in the study will be to further investigate HAp presence using qualitative X-ray Powder Diffraction (XRD).

Biocomposites for Orthopedic and Dental Application

The development of polymer and inorganic filler lead to new biocomposite materials with a wide range of applications in orthopedic and dental application. Biomposites possess an excellent biocompatibility, biodegradability and superior mechanical properties. The inclusion of bioactive filler of hydroxyapatite, wollastonite glass-ceramics and bioactive glass could provide bioactivity of biocomposites. This review summarizes the recent work on the development of biocomposites containing biopolymers with different bioactive particles suitable for use in bone defects/bone regeneration and dental application.

Bioactive glass fillers reduce bacterial penetration into marginal gaps for composite restorations

ObjectiveBioactive glass (BAG) is known to possess antimicrobial and remineralizing properties; however, the use of BAG as a filler for resin based composite restorations to slow recurrent caries has not been studied. Accordingly, the objective of this study was to investigate the effect of adding 15wt% BAG to a resin composite on bacterial biofilms penetrating into marginal gaps of simulated tooth fillings in vitro during cyclic mechanical loading. MethodsHuman molars were machined into approximately 3mm thick disks of dentin and 1.5–2mm deep composite restorations were placed. A narrow 15–20 micrometer wide dentin-composite gap was allowed to form along half of the margin by not applying dental adhesive to that region. Two different 72wt% filled composites were used, one with 15wt% BAG filler (15BAG) and the balance silanated strontium glass and one filled with aerosol silica and silanated strontium glass without BAG (0BAG—control). Samples of both groups had Streptococcus mutans biofilms grown on the surface and were tested inside a bioreactor for two weeks while subjected to periods of cyclic mechanical loading. After post-test biofilm viability was confirmed, each specimen was fixed in glutaraldehyde, gram positive stained, mounted in resin and cross-sectioned to reveal the gap profile. Depth of biofilm penetration for 0BAG and 15BAG was quantified as the fraction of gap depth. The data were compared using a Student's t-test. ResultsThe average depth of bacterial penetration into the marginal gap for the 15BAG samples was significantly smaller (∼61%) in comparison to 0BAG, where 100% penetration was observed for all samples with the biofilm penetrating underneath of the restoration in some cases. SignificanceBAG containing resin dental composites reduce biofilm penetration into marginal gaps of simulated tooth restorations. This suggests BAG containing composites may have the potential to slow the development and propagation of secondary tooth decay at restoration margins.

A comparative study of the effects of different bioactive fillers in PLGA matrix composites and their suitability as bone substitute materials: A thermo-mechanical and in vitro investigation

Bone substitute composite materials with poly(L-lactide-co-glycolide) (PLGA) matrices and four different bioactive fillers: CaCO3, hydroxyapatite (HA), 45S5 Bioglass® (45S5 BG), and ICIE4 bioactive glass (a lower sodium glass than 45S5 BG) were produced via melt blending, extrusion and moulding. The viscoelastic, mechanical and thermal properties, and the molecular weight of the matrix were measured. Thermogravimetric analysis evaluated the effect of filler composition on the thermal degradation of the matrix. Bioactive glasses caused premature degradation of the matrix during processing, whereas CaCO3 or HA did not. All composites, except those with 45S5 BG, had similar mechanical strength and were stiffer than PLGA alone in compression, whilst all had a lower tensile strength. Dynamic mechanical analysis demonstrated an increased storage modulus (E′) in the composites (other than the 45S5 BG filled PLGA). The effect of water uptake and early degradation was investigated by short-term in vitro aging in simulated body fluid, which indicated enhanced water uptake over the neat polymer; bioactive glass had the greatest water uptake, causing matrix plasticization. These results enable a direct comparison between bioactive filler type in poly(α-hydroxyester) composites, and have implications when selecting a composite material for eventual application in bone substitution.

Preparation and characterization of a novel multi-component composite biological filler

A novel multi-component biological filler, consisting of residual activated sludge, clay, humus, silicon compounds, fly ash, and humic acid organic fertilizer, is described here. The aim of the study was to enhance and improve the activity of activated sludge in a biological wastewater treatment process. Following the addition of the filler to a sequencing batch reactor, significant effects on sludge settling properties, sludge yield, sludge dewatering performance, and sludge odor were observed. To further optimize the components of the novel multi-component composite bioactive filler and to improve the activity of the sludge, its composition and microstructure were studied. The biological filler was characterized by different techniques, i.e. field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS), and Fourier transform infrared spectroscopy (FTIR). Through measurements of the composition of organic matter and humus, it was found that the content of each component remained unchanged over a six-month period. The FESEM results showed that the surface of the filler was rough and porous, while the EDS results revealed that the main elements in the filler were O, Si, and C, and the FTIR results indicated that the main functional groups of the absorption peak were –COOH, CO32-, SiO2, and –C=O. The elements contained within these functional groups (O, Si, and C) were the same as those identified by the EDS.

Natural‐Based Nanocomposites for Bone Tissue Engineering and Regenerative Medicine: A Review

Tissue engineering and regenerative medicine has been providing exciting technologies for the development of functional substitutes aimed to repair and regenerate damaged tissues and organs. Inspired by the hierarchical nature of bone, nanostructured biomaterials are gaining a singular attention for tissue engineering, owing their ability to promote cell adhesion and proliferation, and hence new bone growth, compared with conventional microsized materials. Of particular interest are nanocomposites involving biopolymeric matrices and bioactive nanosized fillers. Biodegradability, high mechanical strength, and osteointegration and formation of ligamentous tissue are properties required for such materials. Biopolymers are advantageous due to their similarities with extracellular matrices, specific degradation rates, and good biological performance. By its turn, calcium phosphates possess favorable osteoconductivity, resorbability, and biocompatibility. Herein, an overview on the available natural polymer/calcium phosphate nanocomposite materials, their design, and properties is presented. Scaffolds, hydrogels, and fibers as biomimetic strategies for tissue engineering, and processing methodologies are described. The specific biological properties of the nanocomposites, as well as their interaction with cells, including the use of bioactive molecules, are highlighted. Nanocomposites in vivo studies using animal models are also reviewed and discussed.

Cytotoxicity of resin composites containing bioactive glass fillers

ObjectiveTo determine the in vitro cytotoxicity of dental composites containing bioactive glass fillers. MethodsDental composites (50:50 Bis-GMA/TEGDMA resin: 72.5wt% filler, 67.5%Sr–glass and 5% OX50) containing different concentrations (0, 5, 10 and 15wt%) of two sol–gel bioactive glasses, BAG65 (65mole% SiO2, 31mole% CaO, 4mole% P2O5) and BAG61 (3mole% F added) were evaluated for cytotoxicity using Alamar Blue assay. First, composite extracts were obtained from 7 day incubations of composites in cell culture medium at 37°C. Undifferentiated pulp cells (OD-21) were exposed to dilutions of the original extracts for 3, 5, and 7 days. Then freshly cured composite disks were incubated with OD-21 cells (n=5) for 2 days. Subsequently, fresh composite disks were incubated in culture medium at 37°C for 7 days, and then the extracted disks were incubated with OD-21 cells for 2 days. Finally, fresh composites disks were light cured for 3, 5, and 20s and incubated with OD-21 cells (n=5) for 1, 3, 5, and 7 days. To verify that the three different curing modes produced different levels of degree of conversion (DC), the DC of each composite was determined by FTIR. Groups (n=5) were compared with ANOVA/Tukey's (α≤0.05). ResultsExtracts from all composites significantly reduced cell viability until a dilution of 1:8 or lower, where the extract became equal to the control. All freshly-cured composites showed significantly reduced cell viability at two days. However, no reduction in cell viability was observed for any composite that had been previously soaked in media before exposure to the cells. Composites with reduced DC (3s vs. 20s cure), as verified by FTIR, showed significantly reduced cell viability. SignificanceThe results show that the composites, independent of composition, had equivalent potency in terms of reducing the viability of the cells in culture. Soaking the composites for 7 days before exposing them to the cells suggested that the “toxic” components had been extracted and the materials were no longer cytotoxic. The results demonstrate that the cytotoxicity of composites with and without BAG must predominantly be attributed to the release of residual monomers, and not to the presence of the BAG.

Development of an injectable bioactive bone filler cement with hydrogen orthophosphate incorporated calcium sulfate.

Calcium sulfate cement (CSC) has emerged as a potential bone filler material mainly because of the possibility of incorporating therapeutic agents. Delivery of the cement through a needle or cannula will make it more useful in clinical applications. However, it was not possible to make CSC injectable because of the inherent lack of viscosity. The present work demonstrates the design development of a viscous and fully-injectable CSC by incorporating hydrogen orthophosphate ions, which does not hamper the biocompatibility of the material. The effect of addition of hydrogen orthophosphate on the rheological properties of the CSC paste was studied using a custom made capillary rheometer. The physicochemical changes associated with cement setting process were examined using X-ray diffraction and Fourier transform infrared spectroscopy and the thermal changes were measured through isothermal differential scanning calorimetry. Micromorphological features of different compositions were observed in environmental scanning electron microscopy and the presence of phosphate ions was identified with energy dispersive X-ray spectroscopic analysis and inductively coupled plasma-optical emission spectroscopy. The results indicated that HPO4 (2-) ions have profound effects on the rheological properties and setting of the CSC paste. Significant finding is that the HPO4 (2-) ions are getting substituted in the calcium sulfate dihydrate crystals during setting. The variations of setting time and compressive strength of the cement with the additive concentration were investigated. An optimum concentration of 2.5 % w/w gave a fully-injectable cement with clinically relevant setting time (below 20 min) and compressive strength (12 MPa). It was possible to inject the optimised cement paste from a syringe through an 18-gauge needle with thumb pressure. This cement will be useful both as bone filler and as a local drug delivery medium and it allows minimally invasive bone defect management.

Bioactive Hybrid Organogels Based on Miniemulsion Synthesis of Morphologically Complex Polymer/Surfactant/Calcium Phosphate Nanostructures

Morphologically complex amorphous calcium phosphate nanostructures are synthesized within supersaturated water-in-oil miniemulsions stabilized by a mixture of a calcium bis(2-ethylhexyl)phosphate (Ca(DEHP)2) surfactant and poly(ethylene oxide)19-poly(propylene oxide)69-poly(ethylene oxide)19 (P123) triblock copolymer. Solvent evaporation at room temperature results in self-supporting viscous organogels comprising an interconnected network of calcium phosphate nanofilaments embedded within a continuous polymer/surfactant matrix. The P123/DEHP/calcium phosphate organogels are employed as a bioactive filler for the occlusion of exposed dentine tubules using a standard bovine tooth model.