Anhydrous Phosphate Research Articles

A two-step reaction to prepare a fast-hardening strontium-calcium phosphate scaffold in room temperature

Objective To evaluate a fast-hardening strontium-calcium phosphate scaffold using a two-step reaction in room temperature. Methods The original powder phase consisted of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and strontium hydrogen phosphate (DSPA). The liquid phase consisted of 20wt% citric acid and 12wt% polyvinylpyrrolidone K-30. Groups were designed as Sr-0, Sr-5, Sr-10, and Sr-20, according to the molar ratios of Sr/(Sr+Ca) being 0, 5%, 10%, and 20% in the powder phase, respectively. The ratio 0.5 mL/g in the liquid to solid phase was used for mixing. After the scaffold was prepared, its setting time, compression strength, phase composition and structural morphology, ions release and pH value of the substrates were analyzed. Results Addition of citric acid accelerated the setting reaction. Acceptable setting time was achieved by optimizing composition of the original powder and liquid phases. On the other hand, the compression strength, phase composition and structural morphology were not affected by addition of strontium. In addition, calcium and strontium ions were detected in the substrates, without any significant change in the pH value. Conclusion This two-step reaction can be used to prepare a fast hardening strontium-calcium phosphate scaffold in room temperature. Key words: Strontium; Calcium phosphates; Hydroxyapatites; Setting time

Anhydrous Europium Phosphates: A Comprehensive Report on Syntheses, Crystal Structures, and Phase Relations

In the ternary system Eu/P/O the anhydrous phosphates EuII3(PO4)2, EuII3EuIII(PO4)3, EuIII3O3(PO4), EuIIIPO4, EuIII(PO3)3, and EuIIIP5O14 exist at equilibrium conditions (ϑ ≈ 1000 °C). A superstructure model for EuII3EuIII(PO4)3 [Eulytite structure family, Fdd2, Z = 24, a = 14.298(1) Å, b = 42.123(3) Å, c = 10.3887(9) Å] is proposed. The results of single‐crystal X‐ray diffraction (SXRD) studies on EuII10–xEuIIIx(PO4)6O1+x/2 (x ≈ 1.5), EuIII3O3(PO4) and ht‐EuIII(PO3)3 are reported. The crystal structures of the thermodynamically metastable phases EuIII2P4O13 (isotypic to YIII2P4O13) and lt‐EuIII(PO3)3 (isotypic to GdIII(PO3)3) were refined from X‐ray powder diffraction data (XRPD). According to our investigation for the oxide phosphide “EuII4OP2” an europium deficiency has to be assumed according to EuII4–xEuIII2x/3OP2 (x ≈ 1.5).

Setting time evaluation of injectable carbonate apatite cement using various sodium carboxymethylcellulose (Na CMC) concentration

Introduction: The injectable calcium phosphate cement has the advantage to be used in the bone defect with the limited access which supports a minimally invasive surgical technique. These Injectability properties of calcium phosphate cement can be modified by adding a sodium carboxymethylcellulose (Na CMC). The aim of this present study is to investigate the setting time of injectable bone cement based on CO3Ap using various Na CMC concentration. Methods: Vaterite (a polymorph of CaCO3) and Dicalcium Phosphate Anhydrous (DCPA) as powder phase mixed with 0.2 mol/L Na2HPO4 solution containing 1% polyethylene glycol (PEG) and various concentration of Na CMC as followed 0.5%, 1%, 1.5%, and 2%, respectively. Each concentration groups was consisting of 5 samples from total 20 samples. Powder and liquid phase was mixed with a spatula at a liquid to powder (L/P) ratio of 0.4. The setting time of CO3Ap cement was evaluated according to the modification method standardized by ISO 1566 for dental zinc phosphate cement using a custom fabricated Vicat needle apparatus. The cement was maintained at 37ºC and 100% relative humidity as a standard requirement. Results: The mean value of setting time cement was as followed 0.5% Na CMC 35:06 minutes, 1% Na CMC 38:48 minutes, 1.5% Na CMC 40:06 minutes, and 2% Na CMC 41:30 minutes. The result is statistically significant (p<0.05) with the group of 0.5% Na CMC compared to others group. Conclusion: Increasing the concentration of Na CMC could prolong the setting time of CO3Ap cement.

Characterization of hybrid light-cured resin composites reinforced by microspherical silanized DCPA/nanorod HA via thermal fatigue

The mechanical and self-mineralized properties of nanohybrid composite resins used for the dental restoration of class V caries are investigated. The nanorod hydroxyapatite (Nr-HA) hybrid and the microspherical granular dicalcium phosphate anhydrate (DCPA) after silanization were mixed and used as fillers in different kinds of composite resins (abbreviated as DCPA, DCPA+5Nr-HA, and DCPA+10Nr-HA). Their composite strengths were measured via 3-point flexure. Their properties were characterized from environmental samples after water immersion for 24 h and exposure to thermal fatigue between 5 and 55 °C for 600 and 2400 cycles. The resin reinforced with high amounts of Nr-HA (DCPA+10Nr-HA) showed a significant increase in mineralization of the sample surfaces, which consequently enhanced microhardness. The presence of Nr-HA also increased the residual energy of samples during preparation and enhanced their capacity to reprecipitate after immersion and through thermal fatigue. However, the presence of Nr-HA also resulted in high ductility and early failure of the sample, especially in the reinforced group with the highest amount of Nr-HA (DCPA+10Nr-HA). The appropriate additive Nr-HA (DCPA+5Nr-HA) balanced the properties with less difference of strength and residual energy compared with the DCPA group. The additive showed superior capability in enhancing the release of ions and initiating mineralization after immersion with thermal fatigue in vitro. This newly developed composite resin may provide an excellent combination of stress bearing, improved residual energy before the sample fracture, enhanced mineralization capacity, and improved caries-inhibiting capabilities.

Effect of Calcium and Phosphate on Compositional Conversion from Dicalcium Hydrogen Phosphate Dihydrate Blocks to Octacalcium Phosphate Blocks

Octacalcium phosphate (OCP) has attracted much attention as an artificial bone substitute because of its excellent osteoconductive and bone replacement properties. Although numerous studies have investigated OCP powder fabrication, there are only a few studies on OCP block fabrication. Therefore, in this study, the feasibility of optimizing dicalcium hydrogen phosphate dihydrate (DCPD) blocks, as a precursor for OCP block fabrication, under a pH 6 adjusted acetate buffer solution at 70 °C for 2 days was investigated. When a DCPD block was immersed in acetate buffer, the block was partially converted to OCP, with a large amount of dicalcium hydrogen phosphate anhydrate (DCPA), and its macroscopic structure was maintained. When the DCPD block was immersed in a Ca-containing solution, it was converted to mainly hydroxyapatite (HAp) with DCPA. On the other hand, when the DCPD block was immersed in a PO4-containing solution, the block was converted to OCP, and its macroscopic structure was maintained. In other words, the PO4-induced calcium phosphate with a Ca/P molar ratio lower than 1.0 may represent an intermediate phase during the compositional transformation from a DCPD block to an OCP block through the dissolution–precipitation reaction.

Novel treatment of in-office tooth bleaching sensitivity: A randomized, placebo-controlled clinical study.

Aim of this clinical trial was to investigate the effect of a calcium phosphate based desensitizer paste applied prior to in-office tooth whitening on bleaching sensitivity (BS). This crossover study was designed as randomized double-blinded, placebo-controlled trial. The desensitizer paste Teethmate AP (TAP) contains tetracalcium phosphate and dicalcium phosphate anhydrous in glycerol and polyethylene glycol, whereas placebo (PLA) is a calcium phosphate free analog. Fifty patients with sound maxillary incisors and canines were enrolled. Tooth shades were determined with a Vitapan Classic Shade guide. Randomly, TAP and PLA were applied to the left or to the right anterior teeth. After rinsing and air-drying the bleaching gel (Opalescence Boost PF 40%) was applied and left on the labial surfaces for 15 minutes. Sensitivity was recorded using a 10 cm visual analog scale (VAS) before, at 5, 10, and 15 minutes during, and at 1 hour, 1, 2, and 7 days after bleaching. Tooth whitening was determined with the shade guide after 1 day and 1 week. Prebleaching desensitization with TAP reduced BS significantly when compared with PLA. Between 1 and 7 days the average sensitivity scores were close to zero, whereas the average scores for PLA were significantly higher during this time interval. Independent from the desensitizing treatment after 1 and 7 days the medians of the shades were between 5 and 3.5 units brighter. Prebleaching desensitization with TAP was effective in reducing BS during and after tooth whitening treatment and had no adverse effect on the bleaching result. Prebleaching topical application of a calcium phosphate containing compound reduced significantly bleaching sensitivity during a single 15 minutes treatment and up to one week with a 40% hydrogen peroxide containing gel without compromising tooth whitening.

The relationship among tensile strength, Young's modulus, and indentation hardness of pharmaceutical compacts

Mechanical properties of pharmaceutical materials, e.g., Young's modulus (E), indentation hardness (H), and tensile strength (σt), play an important role in powder compaction process. However, few studies investigated the relationship among these parameters and consequence for tablet compression. Using microcrystalline cellulose, a plastic material, and dibasic calcium phosphate anhydrate, a brittle material, as well as their binary mixtures, we systematically examined the relationship among the three properties. It was found that Young's modulus was proportional to indentation hardness (H/E≈0.036) regardless of the composition and compaction pressure. For a given material, tensile strength was also proportional to E and H but the relationship varied with materials. Higher E and H were required to attain the same σt for a more brittle material.

Roll Compaction/Dry Granulation of Dibasic Calcium Phosphate Anhydrous—Does the Morphology of the Raw Material Influence the Tabletability of Dry Granules?

The influence of raw material particle morphology on the tabletabilty of dry granules was investigated. Therefore, dibasic calcium phosphate anhydrous was used as a model material. One milled grade, 2 agglomerated grades with different porosities, and a functionalized structure, that is, an agglomerate formed by very small primary particles, were included. Particle size, density, and specific surface area of raw materials were measured. The starting materials and 2 fractions of dry granules were compressed to tablets. The tabletability of granules was compared to that of the powders and the influence of specific compaction force, granule size, and lubrication on tablet tensile strength was evaluated. All materials showed a loss in tabletability induced by a previous compaction step but to a varying extent. Only in case of the functionalized calcium phosphate morphology, this effect depended on the specific compaction force. In contrast to the other materials, the tabletability of functionalized calcium phosphate was influenced by the granule size. This effect was not related to an overlubrication as internal and external lubrication resulted in similar tensile strengths. A clear influence of the particle morphology on tablet strength was demonstrated by the study. The functionalized structure showed aspects of a more plastic deformation behavior. The functionalized dibasic calcium phosphate and the more porous agglomerate performed as potential filler/binder in the field of roll compaction/dry granulation.

Investigation of physical and chemical properties and structure of tripolyphosphate coatings on zinc plated steel

The results of complex studies on the influence of the concentration of aqueous sodium tripolyphosphate solution on the physicochemical properties and structure of the coats on zinc-plated steel are presented. The coats were chemically deposited from 2–14 % aqueous sodium tripolyphosphate (STPP) solutions, heated to 70 oС. It has been established that increasing concentration of aqueous STPP solution leads to an increase of the specific mass and crystallinity of the coats and decrease of protective properties. Metallographic studies have shown that the amorphous structure of the coats deposited from 2 % aqueous STPP solution changes to a structure with large sizes of crystallites for the coats prepared from aqueous STPP solutions with higher concentrations. The results of the X-ray diffraction (XRD) analysis have revealed that the coats with low protective properties, in addition to anhydrous zinc phosphates, also contain hydrated species. By means of raster electron microscopy, it has been established that the coats with the lowest protective properties, prepared from 12–14 % aqueous STPP solutions, are formed as thick, spongy layers with the presence of microcracks. Such structure leads to the accumulation and containment of moisture, which promotes corrosion under atmospheric conditions.

Experimental determination of residence time distribution in continuous dry granulation

With increasing importance of continuous manufacturing, the interest in integrating dry granulation into a continuous manufacturing line is growing. Residence time distribution measurements are of importance as they provide information about duration of materials within the process. These data enable traceability and are highly beneficial for developing control strategies. A digital image analysis system was used to determine the residence time distribution of two materials with different deformation behavior (brittle, plastic) in the milling unit of dry granulation systems. A colorant was added to the material (20%w/w iron oxide), which did not affect the material properties excessively, so the milling process could be mimicked well. Experimental designs were conducted to figure out which parameters effect the mean residence time strongly. Moreover, two types of dry granulation systems were contrasted. Longer mean residence times were obtained for the oscillating mill (OM) compared to the conical mill (CM). For co-processed microcrystalline cellulose residence times of 19.8–44.4s (OM) and 11.6–29.1s (CM) were measured, mainly influenced by the specific compaction force, the mill speed and roll speed. For dibasic calcium phosphate anhydrate residence times from 17.7–46.4 (OM) and 5.4–10.2s (CM) were measured, while here the specific compaction force, the mill speed and their interactions with the roll speed had an influence on the mean residence time.

On the influence of Mg/P ratio on the properties and durability of magnesium potassium phosphate cement pastes

This paper investigates the influence of magnesium to phosphate molar ratio (Mg/P) on the properties of magnesium phosphate cement pastes (MPPC). The aim of the present study is to investigate the durability of these materials. The results show that excess potassium dihydrogen phosphate (KH2PO4) has a negative impact on overall properties. High quantities of KH2PO4 lead to poor water resistance, as the anhydrous phosphate remained unreacted in the microstructure is highly soluble and generates important values of open porosity when samples are immersed in water. Another drawback to excess KH2PO4 is the appearance of an efflorescence phenomenon, confirmed by XRD analysis. Finally, samples having a high Mg/P molar ratio show important swelling, especially when water is present in the system (autogenous conditions).

Peculiarities in thermal evolution of precipitated amorphous calcium phosphates with an initial Ca/P ratio of 1:1.

Thermal evolution of amorphous calcium phosphate (ACP) powder from a fast nitrate synthesis with a Ca/P ratio of 1:1 were studied in the range of 20-980 °C. The powder consisted of amorphous dicalcium phosphate anhydrate (CaHPO4) after heating to 200 °C. CaHPO4 gradually condensed to amorphous calcium pyrophosphate Ca2P2O7 (CPP) between 200 to 620 °C. Amorphous CPP crystallized at 620-740 °C to a metastable polymorph α'-CPP of the high-temperature phase α-CPP and β-CPP. The α'-CPP/ β-CPP phase ratio reached a maximum at 800 °C (60 wt% α'-CPP/40 wt% β-CPP), and α'-CPP gradually transformed to β-CPP at a higher temperature. Some β-TCP occurred at 900 °C, so that a three-phasic mixture was obtained in the powder heated to 980 °C. The occurrence of metastable α'-CPP is attributed to Ostwald's step rule, and a mechanism for β-TCP formation is proposed. The advantages of prospective biomaterials from these powders are discussed.

Preparation of Dicalcium Phosphate Anhydrous (Monetite) Biological Coating on Titanium by Spray-Drying Method

Titanium and its alloys have been widely used in the manufacture of endosseous implants due to excellent biocompatibility, low elastic modulus, and good chemical stability. However, the titanium based metals are essentially bioinert materials. In order to improve their bioactivity, biological coatings are usually applied. Recent studies found that, compared with hydroxyapatite coating, dicalcium phosphate anhydrous (DCPA, Monetite) coating maybe more bioactive due to higher solubility and release of Ca and P ions. In this work, DCPA coating was prepared through a novel and simple method. Briefly, high concentration DCPA solution was sprayed onto superhydrophilic titanium and the specimens were dried fast in an air-circulating oven. After repeating the process over 100 times, a compact coating was fabricated. The microstructure, chemical composition, wettability, and in vitro bioactivity of the coating were analyzed and evaluated. Results showed that the coating fully covered the substrate and consisted of a large number of uniformly sized DCPA granules that packed together closely. The coating showed good wettability and could keep the property for a long time. After immersion in simulated body fluid for 2 weeks, a large amount of bone-like apatite with low crystallinity was induced implying a good bioactivity.

Lubrication with magnesium stearate increases tablet brittleness

Tablet brittleness index (TBI) quantifies tablet fracture behavior, which strongly correlates with tablet porosity and tensile strength. The goal of this work was to quantify the influence of lubrication on tablet brittleness. Magnesium stearate was used as a lubricant. Several common tablet excipients, i.e., starch, lactose, microcrystalline cellulose (MCC), and dibasic calcium phosphate anhydrate (DCPA), and a binary mixture between lactose and MCC were studied. Tablet tensile strength (σ) and TBI at zero porosity (σ0 and TBI0) were obtained from nonlinear regression of data of all powders to evaluate the relationship between brittleness and bonding strength of pore-free tablets. The results show that lubrication by magnesium stearate led to decrease in σ0 and increase in TBI0. The effect was more profound for both a longer blending time and a higher amount of magnesium stearate. In addition, the TBI of the binary mixture was successfully predicted from the fitted parameters of lactose and MCC using the power mixing rule. Such effects of lubrication on tablet brittleness should be considered during formulation development to avoid unexpected quality issues.

Multiple Fluorine-Substituted Phosphate Germanium Fluorides and Their Thermal Stabilities.

Anhydrous compounds are crucially important for many technological applications, such as achieving high performance in lithium/sodium cells, but are often challenging to synthesize under hydrothermal conditions. Herein we report that a modified solvo-/hydro-fluorothermal method with fluoride-rich and water-deficient condition is highly effective for synthesizing anhydrous compounds by the replacement of hydroxyl groups and water molecules with fluorine. Two anhydrous phosphate germanium fluorides, namely, Na3[GeF4(PO4)] and K4[Ge2F9(PO4)], with chainlike structures involving multiple fluorine substitutions, were synthesized using the modified solvo-/hydro-fluorothermal method. The crystal structure of Na3[GeF4(PO4)] is constructed by the common single chains ∞1{[GeF4(PO4)]3-} built from alternating GeO2F4 octahedra and PO4 tetrahedra. For K4[Ge2F9(PO4)], it takes the same single chain in Na3[GeF4(PO4)] as the backbone but has additional flanking GeOF5 octahedra via an O-corner of the PO4 groups, resulting in a dendrite zigzag single chain ∞1{[Ge2F9(PO4)]4-}. The multiple fluorine substitutions in these compounds not only force them to adopt the low-dimensional structures because of the "tailor effect" but also improve their thermal stabilities. The thermal behavior of Na3[GeF4(PO4)] was investigated by an in situ powder X-ray diffraction experiment from room temperature to 700 °C. The modified solvo-/hydro-fluorothermal method is also shown to be effective in producing the most germanium-rich compounds in the germanophosphate system.

Heterogeneous crystallization of calcium hydrogen phosphate anhydrous (monetite)

The crystal growth of monetite (CaHPO4, DCPA), the least stable calcium phosphate has been investigated by the seeded growth method from solutions supersaturated exclusively with respect to this phase alone. The kinetics of crystal growth was measured at constant supersaturation at 37°C, pH 6.0. The measurements of the rates of crystal growth of DCPA showed a second order dependence on the relative supersaturation of the solutions with respect to DCPA, suggesting that the rate determining step is surface diffusion of the growth units to the active growth sites of the crystals. The heterogeneous crystallization of brushite (CaHPO4·2H2O, DCPD) on DCPA seed crystals in solutions supersaturated with respect to both DCPD and DCPA showed that DCPD nucleation and growth took place selectively by heterogeneous nucleation on the DCPA seed crystals. The same parabolic dependence of the rates on the relative supersaturation of the solutions with respect to DCPD was found, showing that the mechanism was the same as in the case of growth of DCPA on DCPA seed crystals. Seeding of solutions supersaturated with respect to both DCPA and DCPD at pH 6.0, 37°C with collagen type II in powdered form, resulted to the formation of an apatitic solid. The morphology of the crystals formed on the collagenous matrix suggested that the identified mineral was probably the result of rapid hydrolysis of metastable calcium phosphatephases. The formation of the mineral phase on collagen took place past long induction time periods inversely proportional to the relative supersaturation with respect to DCPD and showed that the collagen substrate did not stabilize calcium phosphate at the same conditions at which DCPA did.

Characteristics of multi-layer coatings synthesized on Ti6Al4V alloy by micro-arc oxidation in silver nitrate added electrolytes

Abstract Multi-layer coatings (composed of outer hydroxyapatite and inner titania layers) have been synthesized on Ti6Al4V alloy for biomedical applications by employing micro-arc oxidation at positive and negative voltages of 400 and 80, respectively. Addition of silver nitrate (at concentrations of 0.1 g/L and 0.4 g/L) into the calcium acetate hydrate and disodium hydrogen phosphate anhydrous containing base electrolyte provided an enhancement in bio- and antibacterial activities of the synthesized coating, while imposing precipitation of silver nanoparticles on the hydroxyapatite layer. It is finally concluded that addition of 0.1 g/L AgNO 3 into the base electrolyte is promising for MAO process of titanium-based implants, when the structural characteristics and risk of cytotoxicity are of concern for the synthesized multi-layer coatings.

Size Control in Porosity of Hydroxyapatite Using a Mold of Polyurethane Foam

The optimum sized polyurethane foam (PUF) was used as a mold for the formation of porous hydroxyapatite, HAp (calcium phosphate cement-base). Four PUFs of different formulations were selected based on their cell size and the percentage of open cell structure. In the preparation of porous HAp, tetracalcium phosphate and dicalcium phosphate anhydrous were mixed at a molar ratio of 1:1 in the presence of a cement setting solution namely, sodium phosphate. The effects of the morphology and the cell size of PUF on the HAp morphology were analyzed with a scanning electron microscope. Based on the analysis, it was observed that only PUFs with an average cell size of approximately 600 μm and a 95 % open cell structure could optimally generate porous HAp. This result showed 35 % enhancement in porosity compared to the reported values. This porous HAp fulfiled the two criteria for an ideal porous implant which include a cell size of more than 100 μm and a high percentage of open cell content (>50 %).

Investigation of hydroxyapatite dicalcium phosphate scaffold properties using a Lamarckian immune neural network

In this paper, a hybrid predictive tool is developed to model the main properties of Hydroxyapatite Dicalcium Phosphate Anhydrous (HA/DCPA) scaffold. Since this biodegradable scaffold is widely used as a bone substitute material, it is mandatory to develop an identification model which can give some useful information about its pivotal characteristics. To this aim, two main steps are made. Firstly, the effect of HA/DCPA weight ratio on its compression strength, elastic modulus, calcium dilution, density, porosity and weight change are investigated through experiments. Thereafter, the proposed tool which integrates an Aggregated Neural Network (ANN) and a well-known optimisation method called Multi-objective Lamarckian Immune Algorithm (MLIA) is used to find a robust model. To elaborate on the effectiveness of the proposed approach, some well-known identification systems such as Back Propagation Neural Network (BPNN), Adaptive Neuro-Fuzzy Inference System (ANFIS) and Composite Neuro Particle Swarm Algorithm (CNPSA) are used. The results indicate that the method is strongly capable of modelling all the properties of HA/DCPA simultaneously.

Aluminum Determination for Tri-calcium Phosphate (TCP) Anhydrous Powder by Flame Atomic Absorption Spectrophotometer

Tricalcium Phosphate Anhydrous Powder typically contains 300 to 400 mg/Kg (w/w) of aluminum. This level can be determined utilizing AAS and standard based on known standards. In this study, we have determined the amount of aluminum metal present in sample of Tricalcium Phosphate Anhydrous Powder using Atomic Absorption Spectrophotometer (AAS). The method has high precision and accuracy. The results of aluminum determinations obtained by employment of N2O-C2H2 flame AAS methods. Great care is necessary for preparation of the blank. The need to subtract blank with standard calibration curve this was done automatically. The accuracy was checked with recovery test of aluminum added to the sample before analysis. With employment of AAS method 98.5% and 99.0% of added aluminum was recovered. The detection limit for the determination of Al was 0.5 mg/Kg and results meet the requirements.