Hydroxyapatite Calcium Phosphate Research Articles

Osteogenic enhancement of modular ceramic nanocomposites impregnated with human dental pulp stem cells: an approach for bone repair and regenerative medicine

Background/aimHuman dental pulp-derived mesenchymal stem cells (hDP-MSCs) are a promising source of progenitor cells for bone tissue engineering. Nanocomposites made of calcium phosphate especially hydroxyapatite (HA) offer an impressive solution for orthopedic and dental implants. The combination of hDP-MSCs and ceramic nanocomposites has a promising therapeutic potential in regenerative medicine. Despite the calcium phosphate hydroxyapatite (HA)-based nanocomposites offer a good solution for orthopedic and dental implants, the heavy load-bearing clinical applications require higher mechanical strength, which is not of the HA’ properties that have low mechanical strength. Herein, the outcomes of using fabricated ceramic nanocomposites of hydroxyapatite/titania/calcium silicate mixed at different ratios (C1, C2, and C3) and impregnated with hDP-MSCs both in in vitro cultures and rabbit model of induced tibial bone defect were investigated. Our aim is to find out a new approach that would largely enhance the osteogenic differentiation of hDP-MSCs and has a therapeutic potential in bone regeneration. Subjects and methodsHuman DP-MSCs were isolated from the dental pulp of the third molar and cultured in vitro. Alizarin Red staining was performed at different time points to assess the osteogenic differentiation. Flow cytometer was used to quantify the expression of hDP-MSCs unique surface markers. Rabbits were used as animal models to evaluate the therapeutic potential of osteogenically differentiated hDP-MSCs impregnated with ceramic nanocomposites of hydroxyapatite/tatiana/calcium silicate (C1, C2, and C3). Histopathological examination and scanning electron microscopy (SEM) were performed to evaluate bone healing potential in the rabbit induced tibial defects three weeks post-transplantation. ResultsThe hDP-MSCs showed high proliferative and osteogenic potential in vitro culture. Their osteogenic differentiation was accelerated by the ceramic nanocomposites’ scaffold and revealed bone defect’s healing in transplanted rabbit groups compared to control groups. Histopathological and SEM analysis of the transplanted hDP-MSCs/ceramic nanocomposites showed the formation of new bone filling in the defect area 3 weeks post-implantation. Accelerate osseointegration and enhancement of the bone-bonding ability of the prepared nanocomposites were also confirmed by SEM. ConclusionsThe results strongly suggested that ceramic nanocomposites of hydroxyapatite/ titania /calcium silicate (C1, C2, and C3) associated with hDP-MSCs have a therapeutic potential in bone healing in a rabbit model. Hence, the combined osteogenic system presented here is recommended for application in bone tissue engineering and regenerative medicine.

Apexification of an infected untreated immature tooth with calplus (Calcium hydroxide paste with Iodoform)

Apexification is a method to induce a calcific barrier across an open apex or the sustained apical development of an incomplete root in teeth with necrotic pulp. Apical closure occurs approximately three years after eruption. Apexification is a treatment option that is done with the aim of apical repair by formation of hard tissue barrier through apex. Conventionally, a calcified barrier is inducted using a calcium hydroxide mixture. Various materials that can be used for apexification include Calcium hydroxide, MTA, Tricalcium phosphate, Dentin chips, Calcium phosphate ceramics and hydroxyapatite and bone morphogenetic proteins. Calcium hydroxide is the most common and traditional material employed for inducing apexification. Multi visit technique requiring 6-24 months to complete by using calcium hydroxide paste with Iodoform.

Pediatric Cranioplasty Using Hydroxyapatite Cement: A Retrospective Review and Preliminary Computational Model

Introduction: Cranioplasty is a standard technique for skull defect repair. Restoration of cranial defects is imperative for brain protection and allowing for homeostasis of cerebral spinal fluid within the cranial vault. Calcium phosphate hydroxyapatite (HA) is a synthetic-organic material that is commonly used in cranioplasty. We evaluate a patient series undergoing HA cement cranioplasty with underlying bioresorbable mesh for various cranial defects and propose a preliminary computational model for understanding skull osteointegration. Methods: A retrospective review was performed at the institution for all pediatric patients who underwent HA cement cranioplasty. Seventeen patients were identified, and success of cranioplasty was determined based on clinical and radiographic follow-up. A preliminary computational model was developed using bone growth and scaffold decay equations from previously published literature. The model was dependent on defect size and shape. Patient data were used to optimize the computational model. Results: Seventeen patients were identified with an average age of 6 ± 5.6 years. Average defect size was 11.7 ± 16.8 cm². Average time to last follow-up computer tomography scan was 10 ± 6 months. Three patients had failure of cranioplasty, all with a defect size above 15 cm². The computational model developed shows a constant decay rate of the scaffold, regardless of size or shape. The bone growth rate was dependent on the shape and number of edges within the defect. Thus, a star-shaped defect obtained a higher rate of growth than a circular defect because of faster growth rates at the edges. The computational simulations suggest that shape and size of defects may alter success of osteointegration. Conclusion: Pediatric cranioplasty is a necessary procedure for cranial defects with a relatively higher rate of failure than adults. Here, we use HA cement to perform the procedure while creating a preliminary computational model to understand osteointegration. Based on the findings, cranioplasty shape may alter the rate of integration and lead to higher success rates.

Tumor extracellular hydroxyapatite: a potential biomarker for imaging ovarian cancer

<h3>Objectives:</h3> In ovarian cancer, the criteria to determine whether a patient should undergo primary surgery or be treated with neoadjuvant chemotherapy remain controversial. Furthermore, development of resistance to treatment is common. This is because there are limited biomarkers to predict response to treatment, making the choice of therapy, especially in the recurrent setting, often a matter of trial and error. This may lead to patients being treated with ineffective and toxic therapies. There is clearly a need for more suitable biomarkers that can help predict disease prognosis and which patients may benefit from neoadjuvant chemotherapy versus primary debulking surgery. While tumor calcification has been widely observed in ovarian cancer settings, the origins and significance of these calcifications has never been investigated before. This abstract reports on the discovery of the presence of hydroxyapatite (HAP); Ca10(PO4)6OH2 in the extracellular space of many types of ovarian tumors. We tested 69 annotated tissue microarrays (TMAs) of epithelial ovarian cancer cases patients with ovarian cancer cases originally diagnosed as high-grade serous/papillary ovarian cancer (HGSOC) for HAP. The aim of this investigation was to identify any correlations between tumor extracellular HAP and tumor characteristics, surgical and chemotherapeutic outcome, recurrence and patient survival rate. <h3>Methods:</h3> The TMAs were stained with alizarin red S for calcium, von Kossa for calcium phosphates, and underwent Raman spectroscopy for calcium phosphate hydroxyapatite. <h3>Results:</h3> Preliminary analysis of the TMAs showed that 24 cases tested positive for extracellular HAP (see figure 1 for example). Within these 28 HAP positive cases, 83% were HGSOC, the overall survival was 2.63 ± 1.97 years (mean ± STD) post diagnosis and 38% of cases had recurrence post treatment. On the other hand, of those cases that were negative for extracellular HAP, only 41% were HGSOC, the overall survival was 3.80 ± 3.69 years, and only 20% of those cases had tumor recurrence. <h3>Conclusions:</h3> Those the sample size tested was small and no statistical significance could be established, the results demonstrate the potential importance for testing patients with ovarian tumors for extracellular HAP. Additionally, the lower overall survival and higher recurrence rates of the cases with HAP compared to those without may suggest that not only should patients with ovarian tumors that contain extracellular HAP be monitored more frequently post treatment, but also a different treatment approach altogether may be merited.

The Impact of Ambient Atmospheric Mineral-Dust Particles on the Calcification of Lungs

For the first time, it is shown that inhaled ambient air-dust particles settled in the human lower respiratory tract induce lung calcification. Chemical and mineral compositions of pulmonary calcium precipitates in the lung right lower-lobe (RLL) tissues of 12 individuals who lived in the Upper Silesia conurbation in Poland and who had died from causes not related to a lung disorder were determined by transmission and scanning electron microscopy. Whereas calcium salts in lungs are usually reported as phosphates, calcium salts precipitated in the studied RLL tissue were almost exclusively carbonates, specifically Mg-calcite and calcite. These constituted 37% of the 1652 mineral particles examined. Mg-calcite predominated in the submicrometer size range, with a MgCO3 content up to 50 mol %. Magnesium plays a significant role in lung mineralization, a fact so far overlooked. The calcium phosphate (hydroxyapatite) content in the studied RLL tissue was negligible. The predominance of carbonates is explained by the increased CO2 fugacity in the RLL. Carbonates enveloped inhaled mineral-dust particles, including uranium-bearing oxides, quartz, aluminosilicates, and metal sulfides. Three possible pathways for the carbonates precipitation on the dust particles are postulated: (1) precipitation of amorphous calcium carbonate (ACC), followed by its transformation to calcite; (2) precipitation of Mg-ACC, followed by its transformation to Mg-calcite; (3) precipitation of Mg-free ACC, causing a localized relative enrichment in Mg ions and subsequent heterogeneous nucleation and crystal growth of Mg-calcite. The actual number of inhaled dust particles may be significantly greater than was observed because of the masking effect of the carbonate coatings. There is no simple correlation between smoking habit and lung calcification.

Effect of Bioactivity of Surface Topography and Coating Forming by Infrared Light-Induced on Titanium for Bone Repair

Calcium ions and phosphate ions are usually present in biological organisms and human bodies. Different ratios of calcium to phosphorus result in different types of calcium-to-phosphorus crystals. Hydroxyapatite (HA) is the main component of human hard bony tissues. It has good biocompatibility and is often used in bone repair. With the addition of cobalt ions, it can act as a hypoxia-inducing factor to accelerate the regeneration of hard bony tissues. At present, the laser-assisted biomimetic (LAB) method can very quickly deposit calcium phosphate coatings, which can be used on polymer and titanium surfaces. In this study, we first used anodization treatment (with TiO2 nanotubes (TNTs)), alkali treatment (with NaOH), and acid treatment (with HCl) to form nanopore structures on titanium surfaces in the laboratory. Subsequently, LAB treatment was used to deposit calcium phosphate and cobalt-substituted hydroxyapatite onto titanium pieces with different surface treatments. The results showed that smaller holes resulted in better deposition (TNTs), and controlling the pH value in the solution changed the crystal morphology. LAB treatment imbued the titanium surface with super-hydrophilic properties and improved biocompatibility. A human osteoblast cell line (MG-63) used for the cell viability test showed that LAB treatment can improve cell growth. In particular, TNT-CoHA (cobalt-substituted hydroxyapatite) cells grew the best. Immersion in simulated bodily fluid confirmed that LAB treatment with a CoHA solution improved the hydrophilicity, biocompatibility, and bioactivity of titanium surfaces. It is hoped that this study provides useful information for surface coating of biomedical materials in the future.

Thermal Transformations in Hardening Compositions Based on Hydroxyapatite, Monocalcium Phosphate Monohydrate, and Polymeric Binders

Hardening composite materials based on calcium phosphates (hydroxyapatite, monocalcium phosphate monohydrate) and polymer binders (polyvinyl alcohol, polyvinylpyrrolidone) were obtained. It was found that the amount of brushite and tricalcium phosphate grows with increasing calcium acid phosphate content in the composition. The introduction of polymeric binders into the composition of hardening composite materials promotes growth of their mechanical strength and inhibition of structural-phase transformations of calcium phosphates at 800°C. Compositions based on 5% solutions of polymers and powders of hydroxyapatite or its mixtures with weight content 10 – 40% monocalcium phosphate monohydrate can be used as a consumable for 3D printing of calcium phosphate biomaterials and ceramic.

Homogeneous Nucleation of Hydroxyapatite, Ca5OH(PO4)3, at 37 °C

Precipitation of the calcium phosphate hydroxyapatite, Ca5OH(PO4)3, is studied by simple mixing of reagent solutions and measurement of light scattering (turbidimetry) at six different wavelengths from 300 to 800 nm. Measured turbidities are analyzed using Mie’s theory of light scattering from small particles. Results are interpreted in terms of classical theory of homogeneous nucleation, and from this the surface free energy of crystals is determined. The low value thus found is explained as the effect of protonation of the strongly basic anions hydroxide and phosphate at the crystal surface. Relatively large particles registered by turbidimetry are shown to be not monocrystals, but aggregates of nanocrystals.

EP08 Acute calcific epicondylitis associated with primary hypoparathyroidism: a paradox effect or an adverse event

Abstract Background Calcific tendonitis is characterised by the accumulation of basic calcium phosphate hydroxyapatite crystals within the tendon. It is mainly affects supraspinatus tendon and it is usually idiopathic, but can be associated with other diseases. We are describing a previously unreported case of calcific epicondylitis in a patient with primary hypoparathyroidism on a high dose of calcium supplement with a highlight on its pathogenesis. Methods We describe a previously unreported case of calcific epicondylitis in a patient with primary hypoparathyroidism on a high dose of calcium supplement with literature review highlighting the possible mechanism and pathogenesis. Results A 33-year-old male presented with acute left elbow pain and swelling. A several months earlier, presented to the Emergency Department with similar attack. The elbow x-ray showed two hyper-dense calcifications at the lateral epicondyle. His Ultrasound revealed hyperechoic deposits over the lateral epicondyle with increased Doppler activity confirming the diagnosis of lateral calcific epicondylitis. Previously, he was seen a few times because of nonspecific symptoms of irritability, generalised weakness and numbness, found to have hypocalcemia of &amp;lt; 1.5 mmol/l and low PTH 3 pg/ml, and diagnosed with primary hypoparathyroidism. His serum calcium was maintained by a high intake of daily calcium carbonate 1250 mg three tablets three times daily and calcitriol one mcg/day. Just prior to his presentation, he developed a foreign body sensation on swallowing, and the CT neck revealed a tiny hyper-density calcification along the posterior surface of the soft palate. We gave him Celecoxib 200 mg daily for five days with good response. All his previous calcium levels were on the low normal range, 24-hour urine calcium was elevated at 11.8 mmol/24 hours. We referred him to Endocrinologist for consideration for PTH replacement therapy. Two fundamentally different processes for calcific tendonitis have been proposed: degenerative and reactive calcification. Degenerative theory proposes that dystrophic calcification follows a necrotic phase, usually attributed to a wear-and-tear and aging. This theory is supported by an observation that calcific tendonitis seldom affects young people. While the Reactive calcification theory was described to involves four phases: pre-calcific, formative, resorptive and healing. Reactive calcification theory is supported by a variety of imaging studies demonstrating a complete resolution of the calcium deposits. Calcific tendonitis is largely idiopathic or traumatic. Metabolic causes proposed to play a role, but nothing mentioned with regards to the hypoparathyroidism. It is not clear in our case whether the cause of calcific tendonitis is primarily due to hypoparathyroidism or secondary to the high calcium replacement Conclusion In young patients with hypoparathyroidism on high dose of calcium replacement therapy, a high index of suspicion is needed to diagnose calcific tendonitis. Better understanding of the pathogenesis may help to prevent the soft tissue calcification in general Disclosures B. Awadh None. A. Al-Allaf None.

1H-NMR -based metabolic analysis on biocompatibility of dental biomaterials

Researches on the biocompatibility of dental biomaterials has become a hotspot. As a new subject, metabolomics has unique advantages in research of material compatibility. This paper aims to utilize 1H-NMR method to analyze and evaluate the biocompatibility of 3 common dental biomaterials (Titanium, Hydroxyapatite-calcium phosphate bioceramics and Poly-methyl-methacrylate). We utilize 1H-NMR method to analyze extracellular small molecular metabolites of MC3T3-E1 osteoblasts cultivated on 3 dental biomaterials above. Metabolite path is visualized using metPA network software to identify different characteristic metabolites, with the same software biocompatibility of these materials is also evaluated. The metabolic profiles of the 3 experimental groups are clearly distinguished from the control group. 25 characteristic metabolites are identified that could distinguish the metabolic profiles from experimental groups, many of which are mapped to pathway processes. Amino acid metabolism, glucose metabolism, and Lipid metabolism are correlated with the biocompatibility of these materials. Conclusions: 1H-NMR method is a method to analyze and evaluate the biocompatibility of dental biomaterials.

Functional evaluation and testing of a newly developed Teleost\u2019s Fish Otolith derived biocomposite coating for healthcare

Polymers such as polycaprolactone (PCL) possess biodegradability, biocompatibility and affinity with other organic media that makes them suitable for biomedical applications. In this work, a novel biocomposite coating was synthesised by mixing PCL with layers of calcium phosphate (hydroxyapatite, brushite and monetite) from a biomineral called otolith extracted from Teleost fish (Plagioscion Squamosissimus) and multiwalled carbon nanotubes in different concentrations (0.5, 1.0 and 1.5 g/L). The biocomposite coating was deposited on an osteosynthesis material Ti6Al4V by spin coating and various tests such as Fourier transformation infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), scratch tests, MTT reduction cytotoxicity, HOS cell bioactivity (human osteosarcoma) by alkaline phosphatase (ALP) and fluorescence microscopy were performed to comprehensively evaluate the newly developed biocoating. It was found that an increase in the concentration of carbon nanotube induced microstructural phase changes of calcium phosphate (CP) leading to the formation of brushite, monetite and hydroxyapatite. While we discovered that an increase in the concentration of carbon nanotube generally improves the adhesion of the coating with the substrate, a certain threshold exists such that the best deposition surfaces were obtained as PCL/CP/CNT 0.0 g/L and PCL/CP/CNT 0.5 g/L.

Early Degeneration of Aortic Bioprosthetic Valves Chemical interactions, prevention and treatment

Bioprosthetic heart valves ensure a better quality of life compared to mechanical valves but are prone to degeneration with leaflet calcification and tearing. Valvular leaflets mineralization process is initiated within interstitial cells devitalized by glutaraldehyde with formation of calcium phosphate hydroxyapatite crystals. The aim of the current paper is to analyse early bioprosthetic valve degeneration occurring in three patients that needed bioprosthetic valve explantation and reimplantation of a mechanical valve. The three patients, aged 29, 64 and 78 years presented early degeneration of the implanted valve at 30, 36 and 52 months after the intervention in the context of unavoidable risk factors like young age, chronic kidney disease and small stented valve. Computed tomography examination demonstrated calcifications of the bioprosthetic valve and histological examination confirmed the findings by identifying tissue degeneration with calcification in all cases. Early bioprosthetic valve degeneration is a serious issue in cardiovascular surgery and a major cause of valve failure requiring reintervention. Several methods could be used to delay degeneration like systemic therapy with general anti-calcification agents, the use of locally delivered drugs or tissue pretreatment with special substances (ethanol, nonionic detergents, tridecyl alcohol ethoxylate). No optimal decellularization method for all types of tissues has been yet discovered. In conclusion, early bioprosthetic valve degeneration is a reality that should be taken into account in high risk patients. Current tissue pretreatment with glutaraldehyde is not perfect as it accelerates degeneration with formation of hydroxyapatite calcifications. New methods are needed to achieve efficient decellularization while preserving the functional characteristics of the transplanted tissue.

Scanning electron microscopy for blood micro-crystals in aortic stenosis patients.

BackgroundMicro-crystals of calcium phosphate have been detected on the aortic valve of patients with aortic stenosis using scanning electron microscopy. It is not known whether crystalisation is specific to heart valve tissue or a general blood-derived process.MethodsTo this end we modified the method to determine whether calcium phosphate micro-crystals were present in the blood of patients with aortic stenosis. The method was first validated by adding synthetic calcium phosphate hydroxyapatite micro-crystals to healthy volunteer blood samples and determining the lower limit of detection. Then the method was used to examine the blood of 63 patients with echocardiographically confirmed aortic stenosis and 69 unaffected controls undergoing echocardiography for other reasons. Serum calcium and phosphate were measured and the calcium phosphate product compared in cases and controls.ResultsIn the validation study, synthetic hydroxyapatite micro-crystals were identified down to a lower concentration limit of 0.008mg/mL. In the experimental study no particles were identified in any patient, with or without aortic stenosis, even though serum calcium phosphate was higher in cases compared with controls 2.6mmol/L (2.58–2.77) versus 2.47mmol/L (2.36–2.57), p = 0.005 for the difference.ConclusionThe results of our study confirm a positive association between serum calcium phosphate and aortic stenosis, but indicate that the calcium phosphate particles found in valve tissue do not precipitate freely in the blood.

Powder X-ray diffraction studies of hydroxyapatite and β-TCP mixtures processed by high energy dry milling

Samples of sintered biphasic calcium phosphates hydroxyapatite – Ca10(PO4)6(OH)2 and β-tricalcium phosphate – Ca3(PO4)2 subjected to high energy dry milling for different durations are studied by powder X-ray diffraction analysis. The Rietveld method as implemented in the FullProf program was applied in order to determine the quantities of the resulting crystalline phases and amorphous substance at each stage of the mechanical treatment. Microstructural analysis using appropriate size and strain models was performed in order to handle the distinct anisotropy observed in certain crystallographic directions for the hydroxyapatite and the results are presented in terms of crystallite size and strain evolution of the involved compounds. An interesting phenomenon of crystalline domains size enlargement of the hydroxyapatite phase upon prolonged milling duration was registered and discussed in the light of the up-to-date views and theories on crystal growth of nanocrystalline materials.

Chitosan and its composites: Properties for use in bone substitution.

For many years, research has been carried out on finding an ideal bone substitute. Chitosan (CTS) is a naturally occurring polysaccharide, obtained mainly from, inter alia, the shells of crustaceans. It is characterized by its high level of biocompatibility, biodegradability and antimicrobial properties as well as its support in the healing of wounds. Chitosan, due to its ability to form porous structures, can be used in the production of scaffolds used in the treatment of bone defects. There are numerous studies on the use of CTS in combination with other substances which aim to improve its biological and mechanical properties. The combination of chitosan with the calcium phosphate hydroxyapatite (HAp) has been extensively tested. The objective of the current studies is to verify the properties of scaffolds consisting of chitosan and other substances like polybutylene succinate, human bone marrow mesenchymal stem cells (hBMSCs), collagen, alginate, transforming growth factor - β (TGF-β), insulin-like growth factor (IGF), platelet-derived growth factor (PDGF) or bone morphogenetic proteins (BMP). The aim of the current research is to develop a scaffold with sufficiently good mechanical properties. Trials are underway with many of the biological and synthetic components affecting the biological properties of chitosan. This will allow for the creation of a substitute that fully meets the conditions for an ideal artificial bone.

MWCNT reinforced bone like calcium phosphate—Hydroxyapatite composite coating developed through pulsed electrodeposition with varying amount of apatite phase and crystallinity to promote superior osteoconduction, cytocompatibility and corrosion protection performance compared to bare metallic implant surface

Inconsistent growth of tissues and poor osteoconduction performance on the metallic implant surfaces due to variation of surface energy are major contributing factors for failure of most metallic implant on account of lack of stronger attachment with surrounding bone or tissues. In this study, composite coating of hydroxyapatite, calcium hydrogen phosphate and MWCNT was developed on SS316 surface with varying amount of calcium phosphate-hydroxyapatite phase and crystallinity by pulsed electrodeposition. TEM study revealed that the MWCNTs were bonded strongly with the in situ deposition phases and thus act as reinforcement in the deposited coating similar to the collagen fiber in natural bone structure. Presence of MWCNT reinforcement increased the overall coating modulus of elasticity in the range of 6–10GPa similar to that of natural bone. Different coating surfaces with varied amount of phase and crystallinity exhibits altogether different phenomena and growth geometry of apatite formation during osteoconduction period under contact with SBF. Coatings with highest amount of hydroxyapatite phase exhibit formation of porous spherical (~1μm) and rod like (~600nm) scaffold structure along with presence of nanopores (~100nm) all along the contact surfaces. Cell proliferation study indicated uniform and fast spreading of cells over the coating surfaces as compared to bare metallic implant. EIS study illustrated five times high corrosion resistance capability along with formation of passivation layer under contact with SBF for coating comes with 66% of hydroxyapatite phase.

S53P4 Bioactive Glass - an Alternative Treatment of Bone Defects

A challenging problem in orthopedic practice is represented by bone defects may they occur from trauma, malignancy, infection or congenital disease. Bioactive Glasses have a widely recognized ability to foster the growth of bone cells, and to bond strongly with both hard and soft tissues. Upon implantation, Bioactive Glasses undergoes specific reactions, leading to the formation of an amorphous calcium phosphate or crystalline hydroxyapatite phase on the surface of the glass, which is responsible for its strong bonding with the surrounding tissue. This phenomenon sustains a more rapid healing of bone defects and presents great antibacterial properties. In this paper we report on a clinical study that uses S53P4 Bioactive Glass to successfully treat bone defects and testify of the good compatibility of this material with human tissues.

Morphology and Phase Identification of Bioactive Freeze-Dried β-CaSiO&lt;sub&gt;3&lt;/sub&gt;

Freeze-dried β-wollastonite (β-CaSiO3) powders were synthesized via sol-gel, combined with autoclaved, sintered and finally freeze-dried at -50 °C for 12 h using rice straw ash and calcined limestone as the starting materials. To prepare β-CaSiO3, the precursor ratio of SiO2:CaO was set at 45:55. Pure β-CaSiO3 was obtained after sintering at 950 °C for 3 h. The bioactivity of freeze-dried β-CaSiO3 was investigated by soaking the cylinderical shape samples in simulated body fluid (SBF) up to 21 days. The surface compositional, morphological and structural changes of the samples before and after soaking were analyzed via X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) coupled with EDS. Sintered freeze-dried β-CaSiO3 has a porous structure and changed to cauliflower-like after soaking in simulated body fluid solution. After 21 days of soaking process, an amorphous calcium phosphate (ACP) and calcium deficient hydroxyapatite (CDHA) were formed with the molar ratio of Ca/P between 1.76 to 1.63.

One-step synthesized calcium phosphate-based material for the removal of alizarin S dye from aqueous solutions: isothermal, kinetics, and thermodynamics studies

Calcium phosphate hydroxyapatite (Ca-Hap) synthesized from CaCO3 and H3PO5, it was characterized by scanning electron microscopy, Fourier transform infrared, and X-ray diffraction. The Ca-Hap was used for the removal of Alizarin Red S dye from its aqueous solution. The kinetics, equilibrium, and thermodynamic of the adsorption of the dye onto the Ca-Hap were investigated. The effects of contact time, initial dye concentration, pH as well as temperature on adsorption capacity of Ca-Hap were studied. Experimental data were analyzed using six model equations: Langmuir, Freudlinch, Redlich–Peterson, Temkin, Dubinin–Radushkevich, and Sips isotherms and it was found that the data fitted well with Sips and Dubinin–Radushkevich isotherm models. Pseudo-first-order, pseudo-second-order, Elovic, and Avrami kinetic models were used to test the experimental data in order to elucidate the kinetic adsorption process and it was found that pseudo-second-order model best fit the data. The calculated thermodynamics parameters (∆G°, ∆H° and ∆S°) indicated that the process is spontaneous and endothermic in nature.

Physicochemical Properties of Calcium Phosphate Based Coating on Gutta-Percha Root Canal Filling

Dental Gutta-percha (GP) is a polymer based standard root canal filling material that has been widely used in dentistry. However, it has an inadequate sealing ability and adhesion to root dentin. The aim of this study is to coat GP with a bioactive material to enhance its sealing ability and adhesion to the root sealer and subsequently to the root dentin. The choice of coating method is limited by the nature of GP as it requires a technique that is not governed by high temperatures or uses organic solvents. In this study, biomimetic coating technique using 1.5 Tas-simulated body fluids (SBF) was employed to coat the treated GP cones. The coated samples were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), and field emission scanning electron microscope (FESEM). The presence of hydroxyl, carbonate, and phosphate groups was detected by FTIR while the formation of hydroxyapatite (HA)/calcium phosphate was confirmed with XRD. FESEM revealed uniform, thin, and crystalline HA calcium phosphate coating. The adhesion of the coating to the GP substrate was assessed with microscratch technique. It was viable with cohesive failure mode. In conclusion, Tas-SBF is able to coat pretreated GP cones with a crystalline apatitic calcium phosphate layer.