Preparation, physical–chemical characterisation and cytocompatibility of calcium carbonate cements

Controlled Multi-Dimensional Assembly of Calcium Carbonate Particles with Industrial By-Product Carbide Slag and CO2

The utilization of carbide slag, an industrial by-product, as a resource to prepare value-added products has a profound impact not only for sustainable synthesis and the circular economy but also for CO2 reduction. Herein, we report the very first example of the controlled multi-dimensional assembly of calcium carbonate particles at the micrometer scale with industrial by-product carbide slag and CO2. Calcium carbonate particles of distinctly different sizes, shapes, and morphologies are obtained by finely tuning the assembly conditions. This strategy yields diverse assembled structures, including simple cubic, mulberry-like assembled unit, stacked cubic polycrystalline, and rotated polycrystalline structures, using the same starting materials. This innovative approach not only highlights the adaptability and efficiency of utilizing industrial by-products via multi-dimensional assembly but also provides new insights into the potential applications of the resulting calcium carbonate.

Engineered biomimetic micro/nano-materials for tissue regeneration

The incidence of tissue and organ damage caused by various diseases is increasing worldwide. Tissue engineering is a promising strategy of tackling this problem because of its potential to regenerate or replace damaged tissues and organs. The biochemical and biophysical cues of biomaterials can stimulate and induce biological activities such as cell adhesion, proliferation and differentiation, and ultimately achieve tissue repair and regeneration. Micro/nano materials are a special type of biomaterial that can mimic the microstructure of tissues on a microscopic scale due to its precise construction, further providing scaffolds with specific three-dimensional structures to guide the activities of cells. The study and application of biomimetic micro/nano-materials have greatly promoted the development of tissue engineering. This review aims to provide an overview of the different types of micro/nanomaterials, their preparation methods and their application in tissue regeneration.

Preparation and evaluation of stingray skin collagen/oyster osteoinductive composite scaffolds

The regeneration of bone defects is a major challenge for clinical orthopaedics. Herein, we designed and prepared a new type of bioactive material, using stingray skin collagen and oyster shell powder (OSP) as raw materials. A stingray skin collagen/oyster osteoinductive composite scaffold (Col-OSP) was prepared for the first time by genipin cross-linking, pore-forming and freeze-drying methods. These scaffolds were characterized by ATR-FTIR, SEM, compression, swelling, cell proliferation, cell adhesion, alkaline phosphatase activity, alizarin red staining and RT-PCR etc. The Col-OSP scaffold had an interconnected three-dimensional porous structure, and the mechanical properties of the Col-OSP composite scaffold were enhanced compared with Col, combining with the appropriate swelling rate and degradation rate, the scaffold was more in line with the requirements of bone tissue engineering scaffolds. The Col-OSP scaffold was non-toxic, promoted the proliferation, adhesion, and differentiation of MC3T3-E1 cells, and stimulated the osteogenesis-related genes expressions of osteocalcin (OCN), collagen type I (COL-I) and RUNX2 of MC3T3-E1 cells.

On the physicochemical properties, setting chemical reaction, and in vitro bioactivity of aragonite–chitosan composite cement as a bone substitute

A chitosan gel additive modulates the initial vaterite dissolution–recrystallisation in injectable aragonite-based composite cement and promotes its in vitro bioactivity.

Calcium carbonate: controlled synthesis, surface functionalization, and nanostructured materials

Calcium carbonate (CaCO₃) is an important inorganic mineral in biological and geological systems. Traditionally, it is widely used in plastics, papermaking, ink, building materials, textiles, cosmetics, and food. Over the last decade, there has been rapid development in the controlled synthesis and surface modification of CaCO₃, the stabilization of amorphous CaCO₃ (ACC), and CaCO₃-based nanostructured materials. In this review, the controlled synthesis of CaCO₃ is first examined, including Ca²⁺-CO₃^2- systems, solid-liquid-gas carbonation, water-in-oil reverse emulsions, and biomineralization. Advancing insights into the nucleation and crystallization of CaCO₃ have led to the development of efficient routes towards the controlled synthesis of CaCO₃ with specific sizes, morphologies, and polymorphs. Recently-developed surface modification methods of CaCO₃ include organic and inorganic modifications, as well as intensified surface reactions. The resultant CaCO₃ can then be further engineered via template-induced biomineralization and layer-by-layer assembly into porous, hollow, or core-shell organic-inorganic nanocomposites. The introduction of CaCO₃ into nanostructured materials has led to a significant improvement in the mechanical, optical, magnetic, and catalytic properties of such materials, with the resultant CaCO₃-based nanostructured materials showing great potential for use in biomaterials and biomedicine, environmental remediation, and energy production and storage. The influences that the preparation conditions and additives have on ACC preparation and stabilization are also discussed. Studies indicate that ACC can be used to construct environmentally-friendly hybrid films, supramolecular hydrogels, and drug vehicles. Finally, the existing challenges and future directions of the controlled synthesis and functionalization of CaCO₃ and its expanding applications are highlighted.

Pyrophosphate-stabilised amorphous calcium carbonate for bone substitution: toward a doping-dependent cluster-based model

Multiscale and multitool advanced characterisation of pyrophosphate-stabilised amorphous calcium carbonates allowed building a cluster-based model paving the way for tunable biomaterials.

Calcium carbonate nano- and microparticles: synthesis methods and biological applications

Calcium carbonate micro- and nanoparticles are considered as chemically inert materials. Therefore, they are widely considered in the field of biosensing, drug delivery, and as filler material in plastic, paper, paint, sealant, and adhesive industries. The unusual properties of calcium carbonate-based nanomaterials, such as biocompatibility, high surface-to-volume ratio, robust nature, easy synthesis, and surface functionalization, and ability to exist in a variety of morphologies and polymorphs, make them an ideal candidate for both industrial and biomedical applications. Significant research efforts have been devoted for developing novel synthesis methods of calcium carbonate particles in micrometer and nanometer dimensions. This review highlights different approaches of the synthesis of calcium carbonate micro- and nanoparticles, such as precipitation, slow carbonation, emulsion, polymer-mediated method, including in-situ polymerization, mechano-chemical, microwave-assisted method, and biological methods. The applications of these versatile calcium carbonate micro- and nanoparticles in the biomedical field (such as in drug delivery, therapeutics, tissue engineering, antimicrobial activity, biosensing applications), in industries, and environmental sector has also been comprehensively covered.

The Calcium Phosphate Modified Titanium Implant Combined With Platelet-Rich Plasma Treatment Promotes Implant Stabilization in an Osteoporotic Model

ABSTRACT

Osteoporosis as a kind of systemic bone metabolic disease has become one of the most prevalent diseases among the middle- and old-age, characterized with low bone mass and disruptive osseous microenvironment. The poor bone condition both in quantity and quality makes it daunting for osteoporotic patients who are submitted to dental implantation, joint replacement therapy, or orthopedic surgery. Since calcium phosphate (CaP) and platelet-rich plasma (PRP) treatment, all have improving the effect on bone regeneration. Inspired by this fact, the authors introduced a kind of novel implant with CaP modified surface by HPT (hydrothermal & pressure) treatment in this study. After producing, the authors tested its physicochemical properties through scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS) and contact-angle measurement. Then the authors desired to investigate the effect of this CaP-modified implant on bone regeneration and stabilization maintenance combined with PRP treatment by establishing an osteoporotic rat model. After 3 months of surgery, the authors collected all the specimens and evaluated new bone formation by micro-computed tomography (micro-CT) analysis, biomechanical test, and histologic assessment. All the results in vivo experiment showed the CaP modified implant combined with PRP treatment could improve the osteoinductive effect under osteoporotic condition, leading to better maintenance for stabilization between bone and implant interface, which might be rendered as a promising clinical method for osteoporotic patients when they receive orthopedic surgeries.

Calcium Carbonate Cement: A Carbon Capture, Utilization, and Storage (CCUS) Technique

A novel calcium carbonate cement system that mimics the naturally occurring mineralization process of carbon dioxide to biogenic or geologic calcium carbonate deposits was developed utilizing carbon dioxide-containing flue gas and high-calcium industrial solid waste as raw materials. The calcium carbonate cement reaction is based on the polymorphic transformation from metastable vaterite to aragonite and can achieve >40 MPa compressive strength. Due to its unique properties, the calcium carbonate cement is well suited for building materials applications with controlled factory manufacturing processes that can take advantage of its rapid curing at elevated temperatures and lower density for competitive advantages. Examples of suitable applications are lightweight fiber cement board and aerated concrete. The new cement system described is an environmentally sustainable alternative cement that can be carbon negative, meaning more carbon dioxide is captured during its manufacture than is emitted.

Mechanisms of Phase Transformation and Creating Mechanical Strength in a Sustainable Calcium Carbonate Cement

Calcium carbonate cements have been synthesized by mixing amorphous calcium carbonate and vaterite powders with water to form a cement paste and study how mechanical strength is created during the setting reaction. In-situ X-ray diffraction (XRD) was used to monitor the transformation of amorphous calcium carbonate (ACC) and vaterite phases into calcite and a rotational rheometer was used to monitor the strength evolution. There are two characteristic timescales of the strengthening of the cement paste. The short timescale of the order 1 h is controlled by smoothening of the vaterite grains, allowing closer and therefore adhesive contacts between the grains. The long timescale of the order 10-50 h is controlled by the phase transformation of vaterite into calcite. This transformation is, unlike in previous studies using stirred reactors, found to be mainly controlled by diffusion in the liquid phase. The evolution of shear strength with solid volume fraction is best explained by a fractal model of the paste structure.

Highly Porous Amorphous Calcium Phosphate for Drug Delivery and Bio-Medical Applications

Amorphous calcium phosphate (ACP) has shown significant effects on the biomineralization and promising applications in bio-medicine. However, the limited stability and porosity of ACP material restrict its practical applications. A storage stable highly porous ACP with Brunauer-Emmett-Teller surface area of over 400 m2/g was synthesized by introducing phosphoric acid to a methanol suspension containing amorphous calcium carbonate nanoparticles. Electron microscopy revealed that the porous ACP was constructed with aggregated ACP nanoparticles with dimensions of several nanometers. Large angle X-ray scattering revealed a short-range atomic order of <20 Å in the ACP nanoparticles. The synthesized ACP demonstrated long-term stability and did not crystallize even after storage for over 14 months in air. The stability of the ACP in water and an α-MEM cell culture medium were also examined. The stability of ACP could be tuned by adjusting its chemical composition. The ACP synthesized in this work was cytocompatible and acted as drug carriers for the bisphosphonate drug alendronate (AL) in vitro. AL-loaded ACP released ~25% of the loaded AL in the first 22 days. These properties make ACP a promising candidate material for potential application in biomedical fields such as drug delivery and bone healing.

Mechanical improvement of calcium carbonate cements by in situ HEMA polymerization during hardening

The brittleness of calcium carbonate-based cements, which currently impedes their exploitation, can be overcome by a straightforward polymer-reinforcement strategy.

Bioceramics for Clinical Application in Regenerative Dentistry

Bioceramics represent functional ceramics with significant interest in regenerative medicine area. In orthopedics as well as in oral and maxillofacial surgery, bioceramics have been widely used as bone reconstructive materials. The most common one is hydroxyapatite which have been in the market and clinical applications since the mid of 1970s. Nowadays, a lot of works have been being in the pipeline to develop bioceramics for various clinical applications in regenerative medicine area, including dentistry. Bioceramics have been used and considered promising candidate for periodontal treatment, prevention of relapse, nerve regeneration, vaccine adjuvant, drug delivery technology, even for esthetic medicine and cosmetics. In this chapter, the advantages of bioceramics for regenerative therapy especially in dentistry is discussed. The overview of bioceramics classification is also explained. The future perspective and challenges on the use of bioceramics for next generation regenerative therapy is also discussed.

Safety assessments of subcutaneous doses of aragonite calcium carbonate nanocrystals in rats

Calcium carbonate nanoparticles have shown promising potentials in the delivery of drugs and metabolites. There is however, a paucity of information on the safety of their intentional or accidental over exposures to biological systems and general health safety. To this end, this study aims at documenting information on the safety of subcutaneous doses of biogenic nanocrystals of aragonite polymorph of calcium carbonate derived from cockle shells (ANC) in Sprague-Dawley (SD) rats. ANC was synthesized using the top-down method, characterized using the transmission electron microscopy and field emission scanning electron microscope and its acute and repeated dose 28-day trial toxicities were evaluated in SD rats. The results showed that the homogenous 30 ± 5 nm-sized spherical pure aragonite nanocrystals were not associated with mortality in the rats. Severe clinical signs and gross and histopathological lesions, indicating organ toxicities, were recorded in the acute toxicity (29,500 mg/m²) group and the high dose (5900 mg/m²) group of the repeated dose 28-day trial. However, the medium- (590 mg/m² body weight) and low (59 mg/m²)-dose groups showed moderate to mild lesions. The relatively mild lesions observed in the low toxicity dosage group marked the safety margin of ANC in SD rats. It was concluded from this study that the toxicity of CaCO₃ was dependent on the particulate size (30 ± 5 nm) and concentration and the route of administration used.

Alteration of Masquelet's induced membrane characteristics by different kinds of antibiotic enriched bone cement in a critical size defect model in the rat's femur

The Masquelet technique for the treatment of large bone defects consists of a 2-stage procedure. In the first stage, a polymethylmethacrylate (PMMA) cement spacer is inserted into the bony defect of a rat's femur and over a period of 2-4 weeks a membrane forms that encapsulates the defect/spacer. In a second operation the membrane is opened, the PMMA spacer is removed and the resulting cavity is filled with autologous bone. Different kinds of bone cements are available, with or without supplemental antibiotics. Both might influence the development and the characteristics of the induced membrane which might affect the bone healing response. Hence, this comparative study was performed to elucidate the effect of different bone cements with or without supplemental antibiotics on the development of an induced membrane in a critical size femur defect model in rats. A total of 72 male SD rats received a 10mm critical size defect of the femur which was stabilised by a plate osteosynthesis and filled with either Palacos+Gentamycin, Copal Gentamycin+Vancomycin, Copal+Gentamycin+Clindamycin or Copal Spacem. The induced membranes were analysed after two, four and six weeks (wks) after insertion of the cement spacers (n=6/group). Paraffin embedded histological sections of the membrane were microscopically analysed for membrane thickness, elastic fibres, vascularisation and proliferation by an independent observer blinded to the group setup. The thickness of the induced membrane increased significantly from 2 wks (553 μm) to 6 wks (774 μm) in group Palacos+Gentamycin whereas membrane thickness decreased significantly in groups Copal+Gentamycin+Clindamycin (682-329 μm) and Copal Spacem (916 μm to 371 μm). The comparison between the groups revealed significantly increased membrane thickness in group Palacos+Gentamycin and Copal Gentamycin+Vancomycin in comparison to group Copal+Gentamycin+Clindamycin six weeks after induction. However, the fraction of elastic fibres was significantly increased in groups Copal+Gentamycin+Clindamycin (71%, 80%) and Copal Spacem (82%, 81%) after 2 and 4 weeks in comparison to the groups Palacos+Gentamycin (56%, 57%) and Copal Gentamycin+Vancomycin (63%, 69%). Those differences however were partly diminished after 6 wks. The ratio of immature (vWF+) to more mature (CD31+) blood vessels increased significantly in groups Palacos+Gentamycin and Copal Gentamycin+Vancomycin whereas no significant alterations were noted in groups Copal+Gentamycin+Clindamycin and Copal Spacem. For the first time we demonstrated that thickness and proportion of elastic fibres in induced membranes were influenced by the type of cement and the kind of supplemental antibiotics being used. Whether these alterations of the induced membrane have an effect on bone healing remains to be proven in future studies.

Calcium Silicate and Calcium Hydroxide Materials for Pulp Capping: Biointeractivity, Porosity, Solubility and Bioactivity of Current Formulations

Aim

The chemical-physical properties of novel and long-standing calcium silicate cements versus conventional pulp capping calcium hydroxide biomaterials were compared.

Methods

Calcium hydroxide–based (Calxyl, Dycal, Life, Lime-Lite) and calcium silicate–based (ProRoot MTA, MTA Angelus, MTA Plus, Biodentine, Tech Biosealer capping, TheraCal) biomaterials were examined. Calcium and hydroxyl ion release, water sorption, interconnected open pores, apparent porosity, solubility and apatite-forming ability in simulated body fluid were evaluated.

Results

All calcium silicate materials released more calcium. Tech Biosealer capping, MTA Plus gel and Biodentine showed the highest values of calcium release, while Lime-Lite the lowest. All the materials showed alkalizing activity except for Life and Lime-Lite. Calcium silicate materials showed high porosity values: Tech Biosealer capping, MTA Plus gel and MTA Angelus showed the highest values of porosity, water sorption and solubility, while TheraCal the lowest. The solubility of water-containing materials was higher and correlated with the liquid-to-powder ratio. Calcium phosphate (CaP) deposits were noted on materials surfaces after short aging times. Scant deposits were detected on Lime-Lite. A CaP coating composed of spherulites was detected on all calcium silicate materials and Dycal after 28 days. The thickness, continuity and Ca/P ratio differed markedly among the materials. MTA Plus showed the thickest coating, ProRoot MTA showed large spherulitic deposits, while TheraCal presented very small dense spherulites.

Conclusions

calcium silicate-based cements are biointeractive (ion-releasing) bioactive (apatite-forming) functional biomaterials. The high rate of calcium release and the fast formation of apatite may well explain the role of calcium silicate biomaterials as scaffold to induce new dentin bridge formation and clinical healing.

Nanostructured platforms for the sustained and local delivery of antibiotics in the treatment of osteomyelitis

This article provides a critical view of the current state of the development of nanoparticulate and other solid-state carriers for the local delivery of antibiotics in the treatment of osteomyelitis. Mentioned are the downsides of traditional means for treating bone infection, which involve systemic administration of antibiotics and surgical debridement, along with the rather imperfect local delivery options currently available in the clinic. Envisaged are more sophisticated carriers for the local and sustained delivery of antimicrobials, including bioresorbable polymeric, collagenous, liquid crystalline, and bioglass- and nanotube-based carriers, as well as those composed of calcium phosphate, the mineral component of bone and teeth. A special emphasis is placed on composite multifunctional antibiotic carriers of a nanoparticulate nature and on their ability to induce osteogenesis of hard tissues demineralized due to disease. An ideal carrier of this type would prevent the long-term, repetitive, and systemic administration of antibiotics and either minimize or completely eliminate the need for surgical debridement of necrotic tissue. Potential problems faced by even hypothetically "perfect" antibiotic delivery vehicles are mentioned too, including (i) intracellular bacterial colonies involved in recurrent, chronic osteomyelitis; (ii) the need for mechanical and release properties to be adjusted to the area of surgical placement; (iii) different environments in which in vitro and in vivo testings are carried out; (iv) unpredictable synergies between drug delivery system components; and (v) experimental sensitivity issues entailing the increasing subtlety of the design of nanoplatforms for the controlled delivery of therapeutics.

Electrical stimulation of human mesenchymal stem cells on biomineralized conducting polymers enhances their differentiation towards osteogenic outcomes

Tissue scaffolds allowing the behaviour of the cells that reside on them to be controlled are of particular interest for tissue engineering.

Engineering scaffolds integrated with calcium sulfate and oyster shell for enhanced bone tissue regeneration

Engineering scaffolds combinging natural biomineral and artificially synthesized material hold promising potential for bone tissue regeneration. In this study, novel bioactive calcium sulfate/oyster shell (CS/OS) composites were prepared. Comparing to CS scaffold, the CS/OS composites with a controllable degradation rate displayed enhanced mineral nodule formation, higher alkaline phosphate (ALP) activity and increased proliferation rate while treated osteocytes. In CS/OS composites group, elevated mRNA levels of key osteogenic genes including bone morphogenetic protein-2 (BMP-2), runt-related transcription factor 2 (Runx2), osterix (Osx), and osteocalcin (OCN) were observed. Furthermore, The up-regulation of BMP-2 and type I collagen (COL-I) was observed for CS/OS composites relative to a CS group. Scaffolds were implanted into critical-sized femur cavity defects in rabbits to investigate the osteogenic capacity of the composites in vivo. The CS/OS scaffolds with proper suitable times and mechanical strength strongly promoted osteogenic tissue regeneration relative to the regeneration capacity of CS scaffolds, as indicated by the results of histological staining. These results suggest that the OS-modified CS engineering scaffolds with improved mechanical properties and bioactivity would facilitate the development of a new strategy for clinic bone defect regeneration.

Do novel cement-type biomaterials reveal ion reactivity that affects cell viability in vitro?

Calcium phosphate bioceramics have been studied as bone filler materials for years and have become a component of many commercial products. It is widely known that surface-reactive biomaterials may cause changes in the concentration of crucial ions in the surrounding environment, thereby affecting cell metabolism and viability. The aim of this study was to produce five cement-type biomaterials and characterize their phase composition using X-ray diffraction method, and porosity and pore size distribution using mercury intrusion porosimeter. We then evaluated ion interactions of the novel biomaterials with the surrounding environment (culture medium). A commercially available bone substitute, HydroSet™ (Stryker®), was used as a reference. MTT and NRU cytotoxicity tests were performed to assess the effect of changes in the concentration of crucial ions (calcium, magnesium, phosphate) on osteoblast metabolism and viability in vitro. Our study clearly indicated that various biomaterials demonstrated different ion reactivity and consequently may cause changes in ion concentration in the local environment. Critically low or high values of calcium, magnesium, and phosphate concentrations in the medium exerted cytotoxic effects on the cultured cells. Moreover, we discovered that the chemical composition of the culture medium had a substantial influence on ion interactions with biomaterials.

Silicon-stabilized α-tricalcium phosphate and its use in a calcium phosphate cement: characterization and cell response

α-Tricalcium phosphate (α-TCP) is widely used as a reactant in calcium phosphate cements. This work aims at doping α-TCP with silicon with a twofold objective. On the one hand, to study the effect of Si addition on the stability and reactivity of this polymorph. On the other, to develop Si-doped cements and to evaluate the effect of Si on their in vitro cell response. For this purpose a calcium-deficient hydroxyapatite was sintered at 1250°C with different amounts of silicon oxide. The high temperature polymorph α-TCP was stabilized by the presence of silicon, which inhibited reversion of the β→α transformation, whereas in the Si-free sample α-TCP completely reverted to the β-polymorph. However, the β-α transformation temperature was not affected by the presence of Si. Si-α-TCP and its Si-free counterpart were used as reactants for a calcium phosphate cement. While Si-α-TCP showed faster hydrolysis to calcium-deficient hydroxyapatite, upon complete reaction the crystalline phases, morphology and mechanical properties of both cements were similar. An in vitro cell culture study, in which osteoblast-like cells were exposed to the ions released by both materials, showed a delay in cell proliferation in both cases and stimulation of cell differentiation, more marked for the Si-containing cement. These results can be attributed to strong modification of the ionic concentrations in the culture medium by both materials. Ca-depletion from the medium was observed for both cements, whereas continuous Si release was detected for the Si-containing cement.

Influence of the pore generator on the evolution of the mechanical properties and the porosity and interconnectivity of a calcium phosphate cement

Porosity and interconnectivity are important properties of calcium phosphate cements (CPCs) and bone-replacement materials. Porosity of CPCs can be achieved by adding polymeric biodegradable pore-generating particles (porogens), which can add porosity to the CPC and can also be used as a drug-delivery system. Porosity affects the mechanical properties of CPCs, and hence is of relevance for clinical application of these cements. The current study focused on the effect of combinations of polymeric mesoporous porogens on the properties of a CPC, such as specific surface area, porosity and interconnectivity and the development of mechanical properties. CPC powder was mixed with different amounts of PLGA porogens of various molecular weights and porogen sizes. The major factors affecting the properties of the CPC were related to the amount of porogen loaded and the porogen size; the molecular weight did not show a significant effect per se. A minimal porogen size of 40 μm in 30 wt.% seems to produce a CPC with mechanical properties, porosity and interconnectivity suitable for clinical applications. The properties studied here, and induced by the porogen and CPC, can be used as a guide to evoke a specific host-response to maintain CPC integrity and to generate an explicit bone ingrowth.

Rheological properties of calcium carbonate self-setting injectable paste

With the development of minimally invasive surgical techniques, there is growing interest in the research and development of injectable biomaterials with controlled rheological properties. In this context, the rheological properties and injectability characteristics of an original CaCO(3) self-setting paste have been investigated. Two complementary rheometrical procedures have been established using a controlled stress rheometer to follow the structure build-up at rest or during gentle mixing and/or handling on the one hand, and the likely shear-induced breakdown of this structure at 25 or 35 degrees Celsius on the other. The data obtained clearly show the influence of temperature on the development of a cement microstructure during setting, in all cases leading to a microporous cement made of an entangled network of aragonite-CaCO(3) needle-like crystals. Linear viscoelastic measurements arriving from an oscillatory shear at low deformation showed a progressive increase in the viscous modulus (G'') during paste setting, which is enhanced by an increase in temperature. In addition, steady shear measurements revealed the shear-thinning behaviour of this self-setting paste over an extended period after paste preparation and its ability to re-build through progressive paste setting at rest. The shear-thinning behaviour of this self-setting system was confirmed using the injectability system and a procedure we designed. The force needed to extrude a homogeneous and continuous column of paste decreases strongly upon injection and reaches a weight level to apply on the syringe piston around 2.5 kg, revealing the ease of injection of this CaCO(3) self-setting paste.

In vitro study investigating the mechanical properties of acrylic bone cement containing calcium carbonate nanoparticles

A successful total hip replacement has an expected service life of 10-20 years with over 75% of failures due to aseptic loosening which is directly related to cement mantle failure. The aim of the present study was to investigate the addition of nanoparticles of calcium carbonate to acrylic bone cement. It was anticipated that an improvement in mechanical performance of the resultant nanocomposite bone cement would be achieved. A design of experiment approach was adopted to maximise the mechanical properties of the bone cement containing nanoparticles of calcium carbonate and to determine the constituents and preparation methods for which these occur. The selected conditions provided improvements of 21% in energy to maximum load, 10% in elastic modulus, 7% in bending strength and 8% in bending modulus when compared with bone cement without nanoparticles. Although cement containing nanoCaCO(3) coated in sodium citrate also enhanced the energy to maximum load by 28% and the elastic modulus by 14% when compared with control cement, it is not recommended as a factor in the production of nanocomposite bone cement due to reduction in the bending properties of the final bone cement.

Study on physicochemical properties and in vitro bioactivity of tricalcium silicate-calcium carbonate composite bone cement

In this article, a novel bone cement composed of tricalcium silicate (Ca(3)SiO(5); C(3)S) and calcium carbonate (CaCO(3)) was prepared with the weight percent of CaCO(3) in the range of 0, 10, 20, 30, and 40%. The initial setting time was dramatically reduced from 90 to 45 min as the content of CaCO(3) increased from 0 to 40%, and the workable paste with a liquid/powder (L/P) ratio of 0.8 ml/g could be injected between 2 and 20 min (nozzle diameter 2.0 mm). The composite cement showed higher mechanical strength (24-27 MPa) than that of the pure Ca(3)SiO(5) paste (14-16 MPa). Furthermore, the composite cement could induce apatite formation and degrade in the phosphate buffered saline. The results indicated that the Ca(3)SiO(5)-CaCO(3) paste had better hydraulic properties than pure Ca(3)SiO(5) paste, and also the composite cement was bioactive and degradable. The novel bone cement could be a potential candidate as a bone substitute.

Effect of Sodium Carbonate Solution on Self-setting Properties of Tricalcium Silicate Bone Cement

In this study, the effects of sodium carbonate (Na2CO3 ) solution with different concentrations (10, 15, 20, and 25 wt%) as liquid phase on the setting time and compressive strength of tricalcium silicate bone cements are investigated. The in vitro bioactivity and degradability of the resultant Ca3SiO5-Na2CO3 solution paste was also studied. The results indicate that as the concentration of Na2CO3 solution varies from 0 to 25 wt%, the initial and final setting time of the cement decrease significantly from 90 to 20 min and from 180 to 45min, respectively. After setting for 24 h, the compressive strength of Ca3SiO5-Na2CO3 solution paste reaches 5.1MPa, which is significantly higher than that of Ca 3SiO5-water cement system. The in vitro bioactivity of the cements is investigated by soaking in simulated body fluid (SBF) for 7 days. The results show that the Ca3SiO5-Na2CO 3 solution bone cement has a good bioactivity and can degrade in Ringer's solution. The results indicate that Na2CO3 solution as a liquid phase significantly improves the self-setting properties of Ca 3SiO5 cement as compared to water. The Ca3SiO 5 cement paste prepared using Na2CO3 solution shows good bioactivity and moderate degradability, and the Ca3SiO 5-Na2CO3 solution system may be used as degradable and bioactive bone defect filling materials.

Inorganic materials for bone repair or replacement applications

In recent years, excipient systems have been used increasingly in biomedicine in reconstructive and replacement surgery, as bone cements, drug-delivery vehicles and contrast agents. Particularly, interest has been growing in the development and application of controlled pore inorganic ceramic materials for use in bone-replacement and bone-repair roles and, in this context, attention has been focused on calcium-phosphate, bioactive glasses and SiO2- and TiO2-based materials. It has been shown that inorganic materials that most closely mimic bone structure and surface chemistry most closely function best in bone replacement/repair and, in particular, if a substance possesses a macroporous structure (pores and interconnections >100µm diameter), then cell infiltration, bone growth and vascularization can all be promoted. The surface roughness and micro/mesoporosity of a material have also been observed to significantly influence its ability to promote apatite nucleation and cell attachment significantly. Pores (where present) can also be packed with pharmaceuticals and biomolecules (e.g., bone morphogenetic proteins [BMPs], which can stimulate bone formation). Finally, the most bio-efficient – in terms of collagen formation and apatite nucleation – materials are those that are able to provide soluble mineralizing species (Si, Ca, PO4) at their implant sites and/or are doped or have been surface-activated with specific functional groups. This article presents the context and latest advances in the field of bone-repair materials, especially with respect to the development of bioactive glasses and micro/mesoporous and macroporous inorganic scaffolds. It deals with the possible methods of preparing porous pure/doped or functionalized silicas or their composites, the studies that have been undertaken to evaluate their abilities to act as bone repair scaffolds and also presents future directions for work in that context.

Biodegradable magnesium–hydroxyapatite metal matrix composites

Recent studies indicate that there is a high demand to design magnesium alloys with adjustable corrosion rates and suitable mechanical properties. An approach to this challenge might be the application of metal matrix composite (MMC) based on magnesium alloys. In this study, a MMC made of magnesium alloy AZ91D as a matrix and hydroxyapatite (HA) particles as reinforcements have been investigated in vitro for mechanical, corrosive and cytocompatible properties. The mechanical properties of the MMC-HA were adjustable by the choice of HA particle size and distribution. Corrosion tests revealed that HA particles stabilised the corrosion rate and exhibited more uniform corrosion attack in artificial sea water and cell solutions. The phase identification showed that all samples contained hcp-Mg, Mg(17)Al(12), and HA before and after immersion. After immersion in artificial sea water CaCO3 was found on MMC-HA surfaces, while no formation of CaCO3 was found after immersion in cell solutions with and without proteins. Co-cultivation of MMC-HA with human bone derived cells (HBDC), cells of an osteoblasts lineage (MG-63) and cells of a macrophage lineage (RAW264.7) revealed that RAW264.7, MG-63 and HBDC adhere, proliferate and survive on the corroding surfaces of MMC-HA. In summary, biodegradable MMC-HA are cytocompatible biomaterials with adjustable mechanical and corrosive properties.

Calcium carbonate–calcium phosphate mixed cement compositions for bone reconstruction

The feasibility of making calcium carbonate-calcium phosphate (CaCO(3)-CaP) mixed cements, comprising at least 40% (w/w) CaCO(3) in the dry powder ingredients, has been demonstrated. Several original cement compositions were obtained by mixing metastable crystalline CaCO(3) phases with metastable amorphous or crystalline CaP powders in aqueous medium. The cements set within at most 1 h at 37 degrees C in atmosphere saturated with water. The hardened cement is microporous and exhibits weak compressive strength. The setting reaction appeared to be essentially related to the formation of a highly carbonated nanocrystalline apatite phase by reaction of the metastable CaP phase with part or almost all of the metastable CaCO(3) phase. The recrystallization of metastable CaP varieties led to a final cement consisting of a highly carbonated poorly crystalline apatite analogous to bone mineral associated with various amounts of vaterite and/or aragonite. The presence of controlled amounts of CaCO(3) with a higher solubility than that of the apatite formed in the well-developed CaP cements might be of interest to increase resorption rates in biomedical cement and favors its replacement by bone tissue. Cytotoxicity testing revealed excellent cytocompatibility of CaCO(3)-CaP mixed cement compositions.