Phosphate Cement Research Articles

Microdistribution and Mode of Rare Earth Element Occurrence in the Zhijin Rare Earth Element-Bearing Phosphate Deposit, Guizhou, China

Rare-earth elements (REEs) are often highly concentrated in sedimentary phosphate deposits, and the microdistribution characteristics and occurrence state of rare earth in these deposits play a crucial role in the overall development and utilization of mineral resources. This study aims to analyze the microdistribution of REEs in REE-bearing phosphate deposits in the Zhijin region of Guizhou at the microstructural level and investigate their occurrence modes. Specifically, rock and mineral identification, X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS), and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) were utilized to analyze the samples. The correlation between the distribution of REEs and phosphorus was examined. In addition, the microdistribution of REEs in specific mineral phases and the locations of their occurrence were investigated. The analysis revealed that no REEs existed independently in the deposit. Instead, the distribution of REEs was highly consistent and significantly positively correlated with that of phosphorus. In the microarea structure, REEs were predominantly found both in particles, such as bioclasts, sand debris, and agglomerates, and in phosphate cement, where the main mineral components were collophane and apatite. Conversely, the content of REEs in dolomitized sand debris edges, sparry dolomitic cement, and siliceous cement was considerably lower. Based on these findings, it is speculated that REEs primarily occur within the lattice defects of apatite or on the surface of collophanite. There is a notable contrast in the REE content between the unaltered sand debris at the periphery and the dolomitized sand debris, indicating that the dolomitization in the diagenetic stage resulted in a depletion of REE abundance in the ore. Obviously, the dominant gangue mineral, dolomite, does not serve as the primary host for REEs. Furthermore, the highest concentration of REEs was inside organisms. This finding suggests that the high content of REEs in biological soft tissue may remain under the influence of waves and tides, and REE-bearing apatite may be preferentially separated and fill the cavities of deceased organisms. The second highest content of REEs was found in the shells of organisms, indicating that small shelly organisms absorb phosphorus materials through their life activities to construct their shells, resulting in REE enrichment. Quantitative analysis through sequential extraction procedures displayed that most REEs were present in the residual state, with a smaller portion combined with organic matter. These results confirm that REEs in the Zhijin phosphate deposits primarily exist as isomorphic substitutions in the lattice defects of apatite, with a secondary occurrence as organic matter-bound REEs.

Sulfur geochemistry of the Salitre Formation phosphorites: Implications for the role of microbial ecology and sulfur cycling in phosphogenesis on an Ediacaran carbonate platform

The distribution and activity of polyphosphate-accumulating sulfide oxidizing bacteria within marine sediments control the spatial distribution of sedimentary phosphorite formation in the modern ocean. In modern phosphogenetic settings, the concerted effect of microbial sulfide oxidation and microbial sulfate reduction in sediment pore waters is preserved in the sulfur isotope composition of trace sulfate in authigenic and early-stage diagenetic carbonate cements and phosphatic cements, as well as that of authigenic pyrite. If such variations in microbial sulfur metabolism controlled the spatial distribution of early phosphate mineralization in the geologic past, then one would expect to find differences between the sulfur isotope composition of cement-forming minerals in phosphatic and non-phosphatic facies of ancient sedimentary phosphate deposits. Here, we present paired measurements of the sulfur isotope composition of structural sulfate and structural sulfide in pore cements from co-occurring phosphatic and non-phosphatic facies of the Ediacaran Salitre Formation (Northeastern Brazil). The difference between δ34S of trace structural sulfate in carbonate cements (CAS) or phosphate cements (PAS) and δ34S of structural sulfide in pyrite or chromium-reducible sulfur (CRS), defined as Δ34S, provides a constraint on sulfur cycling within the pore waters from which the cements precipitated. In carbonate-cemented textures of the Salitre Formation, Δ34S = 12 to 31 ‰. In phosphate-cemented textures, however, PAS and pyrite crystals had more similar sulfur isotope compositions: Δ34S = −5–12 ‰. These values support the hypothesis that microbial sulfide oxidation was more prevalent in pore waters where phosphate mineralization occurred compared to pore waters where carbonate mineralization occurred – suggesting that microbial sulfide oxidation may have enabled the formation of sedimentary phosphorite on an Ediacaran carbonate platform, just as in modern phosphogenetic sites.

Bonding Strength of Various Luting Agents between Zirconium Dioxide Crowns and Titanium Bonding Bases after Long-Term Artificial Chewing

The use of hybrid abutment crowns bonded extraorally to a titanium bonding base has aesthetic and biological benefits for the prosthetic rehabilitation of oral implants. The objective of this study was to evaluate the effects of luting agents between a zirconium dioxide crown and the titanium bonding base on crown/abutment retention and the subsequent durability of the prosthetic superstructure. Fifty-six implant abutment samples, all restored with a lower first premolar zirconium dioxide crown, were used and divided into seven groups (n = 8/group) according to the type of luting agent used: group 1, SpeedCEM Plus; group 2, Panavia SA Cement Universal; group 3, Panavia V5; group 4, RelyX Unicem 2 Automix; group 5, VITA ADIVA IA-Cem; group 6, Ketac CEM; and group 7, Hoffmann’s Phosphate Cement. All specimens were subjected to thermomechanical loading (load of 49 N, 5 million chewing cycles and 54.825 thermocycles in water with temperatures of 5 °C and 55 °C). The surviving samples were exposed to a pull-off force until crown debonding from the bonding base. Overall, 55 samples survived the thermomechanical load. Group 2 showed the highest mean pull-off force value (762 N), whereas group 6 showed the lowest mean value (55 N). The differences between the seven groups were statistically significant (ANOVA, p < 0.001). The debonding failure pattern was mainly adhesive and was noticed predominantly at the zirconium dioxide–luting agent interface. Within the scope of the present investigation, it was shown that most of the luting agents are suitable for “cementation” of a zirconium dioxide crown onto a titanium base since the debonding forces are above a recommended value (159 N).

Effects of Zinc and Strontium Doping on In Vitro Osteogenesis and Angiogenesis of Calcium Silicate/Calcium Phosphate Cement.

Based on multiple biological functions (mainly osteogenesis and angiogenesis) of bioactive ions, Zn/Sr-doped calcium silicate/calcium phosphate cements (Zn/Sr-CS/CPCs, including 10Zn-CS/CPC, 20Sr-CS/CPC, and 10Zn/20Sr-CS/CPC) were prepared by the addition of Zn and Sr dual active ions into CS/CPC to further accelerate its bone regeneration in this study. The physicochemical and biological properties of the Zn/Sr-CS/CPCs were systematically investigated. The results showed that the setting time was slightly prolonged, the compressive strength and porosity did not change much, and all groups maintained good injectability after the doping of Zn and Sr. Besides, the doping of Zn and Sr had little effect on the phase and microstructure of hydrated products of CS/CPC. The degradation rate of Zn/Sr-CS/CPCs decreased after doping with Zn and Sr. In mouse bone marrow mesenchymal stem cells (mBMSC) experiments, all Zn/Sr-CS/CPCs stimulated the viability, adhesion, proliferation, and alkaline phosphatase (ALP) activity together with osteogenesis-related genes (ALP, Runx2, Col-I, OCN, and OPN). The further addition of Zn and Sr played better and synergistic roles in in vitro osteogenesis. Thereinto, 10Zn/20Sr-CS/CPC manifested the optimum in vitro osteogenic performance. As for human umbilical vein endothelial cell (HUVEC) experiments, the incorporation of CS doped with Zn and Sr into CPC possessed good vascularization properties of proliferation, NO secretion, tube formation, and the expression of angiogenesis-related genes (VEGF, bFGF, and eNOS). In conclusion, the doping of Zn and Sr into CS/CPC could exhibit excellent osteogenesis and good angiogenesis potentials and 10Zn/20Sr-CS/CPC could be considered as a promising candidate in bone repair.

A tough injectable self‐setting cement‐based hydrogel for noninvasive bone augmentation

AbstractComposite hydrogels with excellent properties can open new opportunities to terminate the need for auto/allografts in bone augmentations. However, their clinical application has been limited by their insufficient mechanical strength and lack of osteoinductivity. Here we report a new strategy to design an injectable bioactive double network hydrogel reinforced by inorganic calcium/magnesium phosphate cement (CMPC) hydrates to meet the mechanical performance requirements for bone regeneration. The engineered CMPC hydration endows the composite hydrogel with an appropriate gelation time and temperature for injection, which shows no harm in the defect site. CMPC hydrates could also provide a lower swelling ratio and higher biodegradation rate fitting the in vivo bone regeneration needs. In vitro and in vivo experiments prove that the ions released from inorganic particles endow biocompatibility, cell migration, adhesion, differentiation, and significantly higher bone regeneration capacity. Taken together, the simple addition of CMPC particles imparts in‐demand features that bring us closer to the clinical utilization of hydrogel‐based materials for bone regeneration.

"Tricalcium Phosphate (Ca3(Po4)2) With Dual Heterovalent Substitution for Obtaining Calcium- Phosphate Cements"

"Tricalcium Phosphate (Ca3(Po4)2) With Dual Heterovalent Substitution for Obtaining Calcium- Phosphate Cements"

Primary human osteoblast and mesenchymal stem cell responses to apatite/tricalcium phosphate bone cement modified with polyacrylic acid and bioactive glass.

In this work, three different modified cements, control apatite/beta-tricalcium phosphate cement (CPC), polymeric CPC (p-CPC), and bioactive glass added polymeric cement (p-CPC/BG) were evaluated regarding their physical properties and the responses of primary human osteoblast cells (HObs) and mesenchymal stem cells (MSCs). Although polyacrylic acid (PAA) increased compressive strength and Young's modulus of the cement, it could cause poor apatite phase formation, a prolonged setting time, and a lower degradation rate. Consequently, bioactive glass (BG) was added to PAA/cement to improve its physical properties, such as compressive strength, Young's modulus, setting time, and degradation. For in vitro testing, HObs viability was assessed under two culture systems with cement-preconditioned medium (indirect) and with cement (direct). HObs viability was examined in direct contact with cements treated by different prewashing conditions. HObs presented a more well spread morphology on cement soaked in medium overnight, as compared to other cements with no treatment and washing in PBS. In addition, the proliferation, differentiation, and total collagen production of both HObs and MSCs adhered to the cement were detected. Cells showed excellent proliferation on PAA/cement and PAA/BG/cement. Furthermore, the higher released Si ion and lower acidosis of PAA/BG/cement-conditioned medium resulted in an increase in osteogenic differentiation (HObs and MSCs) and enhanced collagen production (HObs in osteogenic medium and MSCs in control medium). Therefore, our findings suggest that BG incorporated PAA/apatite/β-TCP cement could be a promising formula for bone repair applications.

Кальцийфосфатные брушитные цементы из замещенного трикальцийфосфата Ca3(PO4)2, армированные силикатным стекловолокном

The reinforcement of reaction hardening phosphate materials (phosphate cements) for bone implants, based on isomorphically cation- (Na+, K+) and anion- (SiO44-, SO42-) substituted tricalcium phosphate (β and α-TCP, Ca3(PO4)2), that are reinforced with silicate (basalt-based) fiberglass, is considered. The obtained materials were characterized by the XRD and SEM methods, mechanical compression tests were carried out, the setting times of cements were determined, changes in the pH of the aqueous medium in contact with the cements under study were measured. Microstructure analysis has been shown that the surface of the reinforcing fiber in contact with the matrix of hardening cement is partially corroded with the formation of phosphate microparticles on it. By pH-metry it was found that the samples during prolonged contact with water do not significantly change the pH value of the aquatic environment, which remains in the nearly neutral range from 5 to 7.5, favorable for further biological tests.

Study on modification of hydroxyapatite/magnesium phosphate bone cement by N-acetyl-l-cysteine

Magnesium phosphate cement has good biological activity and degradation performance. However, it still has the defects of poor strength and water resistance. N-acetyl-l-cysteine has good osteogenic properties. The nano-hydroxyapatite/magnesium phosphate cement was modified by N-acetyl-l-cysteine, and the effects of N-acetyl-l-cysteine on the strength, degradation and biological activity of nano-hydroxyapatite/magnesium phosphate cement were studied. The results showed that the compressive strength of 0.5 wt% N-acetyl-l-cysteine modified nano-hydroxyapatite/magnesium phosphate cement could reach 76.1 ± 1.4 MPa after soaking in simulated body fluid for 28 days, which was 6.3% higher than that of the control group (the content of N-acetyl-l-cysteine was 0 wt%), and the softening coefficient of each age was higher than that of the control group. Cell experiments proved that N-acetyl-l-cysteine could effectively promote cell proliferation and improve the expression of osteogenic related genes and proteins. After implanting the composite bone cement into rats’ femurs for 12 weeks, the materials were gradually wrapped and absorbed, and the new bone tissue grew from outside to inside, indicating that N-acetyl-l-cysteine bone cement had an good ability to promote bone formation. Therefore, the composite bone cement of this study has potential application prospects in clinical bone repair.

Synergistic effects of 3D chitosan-based hybrid scaffolds and mesenchymal stem cells in orthopaedic tissue engineering.

Restoration of damaged bone and cartilage tissue with biomaterial scaffolds is an area of interest in orthopaedics. Chitosan is among the low-cost biomaterials used as scaffolds with considerable biocompability to almost every human tissue. Considerable osteoconductivity, porosity, and appropriate pore size distribution have made chitosan an appropriate scaffold for loading of stem cells and a good homing place for differentiation of stem cells to bone tissue. Moreover, the similarity of chitosan to glycosaminoglycans and its potential to be used as soft gels, which could be lasting more than 1week in mobile chondral defects, has made chitosan a polymer of interest in repairing bone and cartilage defects. Different types of scaffolds using chitosan in combination with mesenchymal stem cells (MSCs) are discussed. MSCs are widely used in regenerative medicine because of their regenerative ability, and recent line evidence reviewed demonstrated that the combination of MSCs with a combination of chitosan with different materials, including collagen type 1, hyaluronic acid, Poly(L-lacticacid)/gelatin/β-tricalcium phosphate, gamma-poly[glutamic acid] polyelectrolyte/titanium alloy, modified Poly(L-Lactide-co-Epsilon-Caprolactone), calcium phosphate, β-glycerophosphate hydrogel/calcium phosphate cement (CPC), and CPC-Chitosan-RGD, can increase the efficacy of using MSCs, and chitosan-based stem cell delivery can be a promising method in restoration of damaged bone and cartilage tissue.

In-situ polymerized polyacrylamide/magnesium phosphate cement electrolyte for structural supercapacitor

Organic/inorganic composite electrolytes can effectively avoid contradictory relationship between ionic conductivity and mechanical properties as well as poor interfacial contact of electrode/solid electrolyte. However, direct mixing of organic/inorganic materials leads to low dosage and poor dispersion of polymers owing to macromolecular chains. Herein, we firstly prepare polyacrylamide/magnesium phosphate cement (PAM/MPC) electrolytes via in-situ polymerization during cement hydration. The weight average molecular weight of polymerized PAM in MPC paste is around 1500 with high concentrated degree of molecular weight distribution. As the dosage of acrylamide (AM) increases to 40 %, polymerized PAM completely interpenetrates into MPC matrix. The composite electrolyte possesses the optimum multifunctionality with ionic conductivity of 54 mS cm−1 and compressive strength of 30.2 MPa, corresponding structural supercapacitor (SSC) can obtain high specific capacitance of 32.0 F g−1 and energy density of 4.4 Wh kg−1. With the lowest equivalent series resistance, the resulted SSC with 10 % AM exhibits the best energy storage properties with energy density of 5.4 Wh kg−1 and power density of 1600 W kg−1. Hopefully, SSC via in-suit polymerization in MPC paste can be integrated with solar panels to generate and store energy in building structures.

Phosphate dental cements aged in vivo up to 25 years

ABSTRACT Phosphates particularly zinc phosphates is a family of conventional dental cements that was developed a century ago and has been in use until today despite the fact that a number of new resin composite cements have been introduced in the market through the years. A close inspection of the in vivo aged samples provides insides to the margins and to the micro-leakage thus would sharpen the understanding and inspire the future development of the cements and cementation interfaces between the dental restorations and the natural tooth or implant abutment. This study highlights the cementation interface and its structural change during in vivo aging. Besides the focused studies on phosphate cements, limited investigation has also been performed on resin composite cements as references.

Cantilever creep method for testing ceramic composites and a case study for chemically bonded phosphate ceramic composites reinforced with glass, carbon and basalt fibers, including both experiments and simulations

This paper presented the cantilever beam experiments and the method for creep in chemically bonded ceramics reinforced with glass, carbon, and basalt unidirectional fibers. The ceramic composite samples were fabricated by mixing wollastonite powder and phosphoric acid, through the resonant acoustic mixing technique. The reinforced fibers were added via pultrusion process. The manufactured materials were exposed to high temperature creep tests at 600, 800 and 1000℃, with an annealing time of 1 h, all in air environment. Some examples of real large-scale structures made manually by a company were also included. In order to understand the microstructure, X-ray diffraction and scanning electron microscopy analysis were included. The presented method is simple and can be used in any inorganic ceramic slurry types, such as geopolymers, phosphate cements, clay-based materials, or Portland cement composites. The sample response in high temperature creep experiments was analyzed with a new but very simple technique, and modeled using finite element analysis over all compositions. Results revealed that fibers have a significant effect on the composite creep when compared to the ceramic without reinforcement, and particularly carbon fibers showed a quite interested effect in reducing the creep effects. Results show the limit of the materials under conditions typically found in fires and other extreme environments.

Influence of heat curing and aggregates on the properties of phosphate-bonded biocomposites

There is renewed effort in reducing the carbon footprint of conventional building materials by employing novel phosphate cements. This study investigates the influence of industrial aggregates, namely fly ash, silica fume and calcium carbonate on biocomposite properties. The biomaterials used included pine, bagasse and wattle. The density of the boards produced ranged from 0.82 to 1.16 g/cm3, and the MOE ranged from 410.57 to 1737.87 MPa. The study concluded that biomass type, curing temperature and aggregates have significant effects on the biocomposite properties. The boards produced met the physical property requirements for use as non-load-bearing structures in humid and external conditions.

Resin Luting Materials

Luting materials are a central component of indirect dentistry, with the most recently introduced types being resin-based materials. These may be classified into conventional resin luting materials, self-adhesive resin luting materials and ‘smart’ resin luting materials. Their physical properties have been found to be good, with no risk of dissolution in the dilute organic acids found in plaque, such as occurs with phosphate and glass ionomer cements. Uses of resin luting materials include the luting of any indirect restoration, but these materials have facilitated the development of the resin-retained bridge and aesthetic ceramic or composite restorations, notwithstanding the fact that they may provide, for the first time, truly adhesive luting of crowns and inlays. CPD/Clinical Relevance: Resin luting materials are appropriate for placement of all indirect restorations: the self-adhesive variants have simplified the use of such materials.

Mechanical Characteristics of Composites Based on β-Ca3(PO4)2/Poly(D,L-Lactide) and β-Ca3(PO4)2/Poly(ε-Caprolactone)

The mechanical characteristics are studied for macroporous composite implants on the basis of β‑Ca/PO4)2/polylactide and β-Ca/PO4)2/polycaprolactone obtained by means of thermal-extrusion 3D printing. The effect of the degree of filling exerted on the strength, Young’s modulus, and the characteristics of the material destruction is described for the polymer, as well as for the three-dimensional structure filled with phosphate cement.

Natural radioactivity of some Egyptian materials used in glasses manufacturing and glass ceramics

Background: The new glasses from harmful environmental waste such as cement dust; limestone phosphate, sand and borax (Genkare) were manufactured. Investigation of the radioactivity present in these materials (Phosphate rock, cement dust, limestone, sand and borax) enables one to assess any possible radiological hazard to humankind by such materials. Materials and Methods: Fifteen samples were collected from five locations. Activity measurements have been performed by gamma-ray spectrometer, employing a high-resolution scintillation detector NaI (Tl) crystal 3 ×3 inch. In addition, the radiological hazards were calculated for the investigated samples. Results: The average values of activity ranged from 28±2 to 163±12, 2.8±0.7 to 40±3 and from 49±4 to 1337±74 Bq kg-1 for 226R, 232Th and 40K, respectively. The values of absorbed dose rates, radium equivalent activities and annual effective dose due to 226Ra, 232Th and 40K respectively, are ranged from 22.05 to 101.59 nGy h-1, 45.90 to 224.22 Bq kg-1 and 27.04 to 124.59 µSv y-1. In addition, the values of external hazard index, internal hazard index and gamma index have been calculated. Conclusion: According to the obtained results, all materials would not present a significant radiological hazard except phosphate. The results of the study could serve as important baseline radiometric data for future epidemiological studies and monitoring initiatives.

Review on Cement Stabilization/Solidification of Municipal Solid Waste Incineration Fly Ash

Municipal solid waste incineration (MSWI) fly ash must be treated properly prior to being disposed in the security landfill due to its serious pollution toxicity. Nowadays, lots of studies have demonstrated that cement‐based stabilization/solidification could reduce the toxicity pollution effectively by encapsulating the heavy metals into cement matrix, which leads to greater capacity and weight. This paper compares and discusses the MSWI fly ash treatment with the mostly used matrix materials such as Portland cement, phosphate cement, aluminate cement, and alkaline activated cement. Moreover, immobilization mechanism introduced by the interaction between the MSWI fly ash and hydrated cement matrix materials, such as the physical cementing effect, adsorption, isomorphous replacement, and complex precipitation, was explored in depth. The paper also pointed out some reasonable development directions for cement‐based stabilization/solidification technology to improve the effectiveness and application of cement‐based stabilization/solidification technology.

Preparation and Characterization of β-Tricalcium Phosphate Powders with High Solubility for Chelate-Setting Calcium-Phosphate Cements

We have previously developed a novel chelate-setting β-tricalcium phosphate (β-TCP) cement with non-fragmentation property in vivo. This novel cement has been set on the basis of chelate-setting mechanism of inositol phosphate (IP6). In this study, β-TCP powders were synthesized by mechanochemical method, and the as-prepared powders were heated at 600-1300°C for 1 h. Some properties of the resulting powders were examined. The crystalline phase of the resulting powders in the range of 600-1100°C was of β-TCP single phase. In the cases at 1200°C and 1300°C, the resulting powders were composed of β-TCP and α-TCP. Median particle sizes of the resulting powders increased with heating temperature from 5.35 μm up to 47.7 μm. Dissolution rate of Ca2+ ions from the β-TCP powders was measured by Japanese Industrial Standard T 0330-3. When the heating temperature was at 700°C, the Ca2+ ions solubility was highest among examined ones. The β-TCP powder heated at 700°C for 1 h will be expected as the starting powder for paste-like artificial bone filler with excellent bioresorbability.

Nano‑calcium phosphate bone cement based on Si-stabilized α-tricalcium phosphate with improved mechanical properties

This study aimed to develop nano‑calcium phosphate cement (nCPC) and evaluate the effect of nanosized precursors on mechanical, physical and handling properties (injectability and setting time) as well as conversion rate of nano-reactants into nano-hydroxyapatite (nHA). In this study, while alpha tricalcium phosphate (α-TCP, 98wt%) and HA (2wt%) were applied as the powder phase, 2.5wt% NaH2PO4 solution was used as liquid phase of cement. Before nano-CPC preparation, Si-stabilized α-TCP nanopowder with particle size of 10±3.6nm was firstly synthesized in a two-step process of sol-gel followed by mechanical alloying. Moreover, HA nanopowder with particle size of 32±3.6nm was synthesized using sol-gel process. Our results revealed that after 3days of immersion in ringer's solution, reactants almost completely converted to nHA. Moreover, the initial and final setting time of nano-CPC was obtained 6.3±2.1min and 14.3±4.0min, respectively. Furthermore, injectability of this formulation was reached 87.90±2.60%. In addition, our results confirmed that the compressive strength and modulus of nano-CPC enhanced with increasing immersion time in ringer's solution from 9.50±1.27MPa and 0.38±0.07GPa (at 1day) to 18.70±2.23MPa and 0.57±0.15GPa (at 5days), respectively. Finally, in order to evaluate cellular responses to nano-CPC, MG63 cells were cultured on it and cell morphology and cytotoxicity were evaluated. Results revealed that nano-CPC enhanced proliferation and spreading of osteoblast like cells compared to control (tissue culture plate) which could be due to both appropriate physical and chemical properties of nano-CPC which stimulate cell proliferation. Our findings suggest the formation of an injectable nano-CPC with appropriate mechanical, physical and degradation rate which can potentially utilized for filling bone defects.