Α-tricalcium Phosphate Powder Research Articles

The reactivity of α-tricalcium phosphate powders is affected by minute amounts of β-calcium pyrophosphate and by the synthesis temperature

α-tricalcium phosphate (α-TCP) is the most widespread raw material for hydraulic calcium phosphate cements (CPCs). CPCs are widely used in bone repair due to their injectability, setting ability, and osteoconductivity. This study investigated the reactivity of α-TCP powders, focusing on the impact of minor phase impurities, β-calcium pyrophosphate and hydroxyapatite, and the synthesis temperature. The α-TCP powders were synthesized via a solid-state reaction of calcium carbonate and anhydrous dicalcium phosphate, with varying Ca/P molar ratios (1.4850-1.5075) and synthesis temperatures (1175°C-1350°C). Powders produced with a Ca/P molar ratio below 1.50 and synthesized at a temperature above the melting point of β-CPP (1296°C) had a broader size distribution and a two to fourfold lower hydraulic reactivity. Conversely, a higher Ca/P molar ratio improved reactivity. The study underscores the importance of precise control over synthesis parameters to enhance the performance of α-TCP-based CPCs, offering insights for optimizing material design in biomedical applications.

Novel Double Hybrid-Type Bone Cements Based on Calcium Phosphates, Chitosan and Citrus Pectin.

In this work, the influence of the liquid phase composition on the physicochemical properties of double hybrid-type bone substitutes was investigated. The solid phase of obtained biomicroconcretes was composed of highly reactive α-tricalcium phosphate powder (α-TCP) and hybrid hydroxyapatite/chitosan granules (HA/CTS). Various combinations of disodium phosphate (Na2HPO4) solution and citrus pectin gel were used as liquid phases. The novelty of this study is the development of double-hybrid materials with a dual setting system. The double hybrid phenomenon is due to the interactions between polycationic polymer (chitosan in hybrid granules) and polyanionic polymer (citrus pectin). The chemical and phase composition (FTIR, XRD), setting times (Gillmore needles), injectability, mechanical strength, microstructure (SEM) and chemical stability in vitro were studied. The setting times of obtained materials ranged from 4.5 to 30.5 min for initial and from 7.5 to 55.5 min for final setting times. The compressive strength varied from 5.75 to 13.24 MPa. By incorporating citrus pectin into the liquid phase of the materials, not only did it enhance their physicochemical properties, but it also resulted in the development of fully injectable materials featuring a dual setting system. It has been shown that the properties of materials can be controlled by using the appropriate ratio of citrus pectin in the liquid phase.

Pyrophosphate ions inhibit calcium phosphate cement reaction and enable storage of premixed pastes with a controlled activation by orthophosphate addition

The standard preparation routine of a calcium phosphate cement includes mixing a solid and a liquid component (reactive cement powder and mixing liquid) in an open bowl at the operating theatre. This poses the risk of preparation-related deviations of the resulting properties when the cements are mixed by different persons. Hence, facilitating this mixing procedure is highly desirable. It can be achieved by application of premixed cement pastes: The mixing liquid and a stable suspension of the cement powder are assembled and mixed in a special syringe, minimizing the impact of these preparation-related effects.In this study, a suspension of reactive α-tricalcium phosphate powder in water was stabilized by sodium pyrophosphate decahydrate (PP). Controlled activation of these premixed pastes was then accomplished by adding a concentrated Na2HPO4/NaH2PO4 (Na2/Na) solution. Systematic assessment of the activation mechanism, including the effect of the PP concentration and the amount of Na2/Na added, was performed by isothermal calorimetry, quantitative in-situ X-ray diffraction, rheological characterization and automated Gillmore needle measurements at 37 °C.Premixed pastes with addition of at least 0.05 wt% PP were successfully stabilized for up to 2 weeks at 25 °C, and even 4 weeks at 4 °C. This pre-storage had no significant impact on the setting performance of the pastes. Increasing the PP concentration at constant Na2/Na amount systematically retarded the setting reaction, while an elevated quantity of Na2/Na addition at constant PP concentration resulted in an acceleration.Based on these results, a composition stabilized with 0.05 wt% PP and activated with 20.8 vol% Na2/Na related to the amount of liquid in the premixed pastes appears ideal with respect to the desired setting performance.

In vivo behavior of biomicroconcretes based on α-tricalcium phosphate and hybrid hydroxyapatite/chitosan granules and sodium alginate.

The current studies provide insights into how predictions based on results of physicochemical and in vitro tests are consistent with the results of in vivo studies. The new biomicroconcrete type materials were obtained by mixing the solid phase, composed of hybrid hydroxyapatite/chitosan granules and highly reactive α-tricalcium phosphate powder, used as the setting agent. This approach guaranteed a good adhesion of the continuous cement phase to the surface of granules. It has been demonstrated that developed biomicroconcretes are surgically handy, possessed favorable physicochemical and biological properties and can be considered as effective bone implant material. The hierarchical porosity and compressive strength (2-6 MPa) similar to cancellous bone made them suitable for low-load bearing applications. Despite the fact that final setting times of biomicroconcretes were longer than recommended in the literature (i.e., exceeded 15 min), their short cohesion time allows for a successful implantation in a rabbit femoral defect model. Histological analysis and Raman studies revealed newly formed bone tissues around the sides of implanted materials. Furthermore, the process of neovascularization and reconstruction of the bone tissue, as well as a reverse scaffolding process, was visible. No signs of inflammation or adverse tissue reactions were observed during the experiment.

Clinical experience of full custom-made artificial bones for the maxillofacial region.

IntroductionAutologous, allogeneic, and artificial bones are clinically applied as graft materials for bone reconstruction, with each having their own advantages and disadvantages. Although artificial bones with various shapes are currently available, a product with a morphology that may be freely modified by operators has not yet been developed. In the present study, we developed a full custom-made artificial bone, and applied it to form the maxillofacial region. We herein report treatment outcomes.MethodsAn artificial bone was prepared on a 3-dimensional solid model, and data of its shape was collected on CT. A full custom-made artificial bone was prepared by laminating α-tricalcium phosphate powder using an aqueous polysaccharide curing solution and the ink-jet powder-laminating device, Z406 3D Printer (DICO, USA). Subjects comprised patients who underwent maxillofacial plasty using this artificial bone between March 2006 and September 2009.ResultsMaxillofacial plasty using the full custom-made artificial bone was applied to 23 regions in 20 patients (14 females and 6 males). The recipient region was the maxilla in 3, mandibular ramus in 13, mental region in 7, and frontal bone in 1. Postoperative courses were favorable in 18 out of the 23 regions; however, the fit was insufficient in 2 regions and the recipient regions were exposed within 1 year after surgery. Three regions were exposed 1 year or more after surgery.ConclusionWe developed a novel reconstruction method using a full custom-made artificial bone. Its fit with the recipient bone was considered to be important, since an ill fit between the recipient and artificial bones potentially resulting in the artificial bone being detached. Therefore, fixation is important in order to prevent the detachment, and careful course observations are required when an ill fit is concerned during the follow-up period.

Preparation of α-Tricalcium Phosphate Powders Surface-modified with Inositol Phosphate for Cement Fabrication

We have previously developed biodegradable β-tricalcium phosphate (β-TCP) cement based on the chelate-setting mechanism of inositol phosphate (IP6). The β-TCP cement powder for the cement fabrication was prepared via a novel powder preparation process, in which the starting β-TCP powders were prepared by simultaneous ball-milling and surface-modification in the IP6 solution. In the present study, the novel powder preparation process was applied to an α-TCP powder, and effect of milling time and beads size for ball-milling on the material properties of the α-TCP powders was investigated. The α-TCP powder ball-milled in 1000 ppm IP6 solution for 4 h with 2 mm-diameter beads was composed of single phase α-TCP with the smallest particle size of 2.2 µm. Dissolution of 4 h-milled α-TCP powder was approximately twice higher than that of starting α-TCP powder before ball-milling. The α-TCP powder with high dissolution property prepared via the novel powder preparation process is potential candidate for fabrication of the chelate-setting cement.

Preparation of α-Tricalcium Phosphate Powders Surface-Modified with Inositol Phosphate for Cement Fabrication

We have previously developed biodegradable β-tricalcium phosphate (β-TCP) cement based on the chelate-setting mechanism of inositol phosphate (IP6). The β-TCP cement powder for the cement fabrication was prepared via a novel powder preparation process, in which the starting β-TCP powders were prepared by simultaneous ball-milling and surface-modification in the IP6 solution. In the present study, the novel powder preparation process was applied to an α-TCP powder, and effect of milling time and beads size for ball-milling on the material properties of the α-TCP powders was investigated. The α-TCP powder ball-milled in 1000 ppm IP6 solution for 4 h with 2 mm-diameter beads was composed of single phase α-TCP with the smallest particle size of 2.2 µm. Dissolution of 4 h-milled α-TCP powder was approximately twice higher than that of starting α-TCP powder before ball-milling. The α-TCP powder with high dissolution property prepared via the novel powder preparation process is potential candidate for fabrication of the chelate-setting cement.

The Effect of α-Tricalcium Phosphate Powder Preparation Methods on Cement Properties

The properties of calcium phosphate cements are influenced both by presence of setting aids in cement paste and also by surface properties and particle size distribution of solid phase. In this study the influence of α-tricalcium phosphate powder preparation methods on properties of cement are examined: milling, thermal treatment at temperatures up to 600°C and treatment with deionized water. The properties of cements based on prepared powders evaluated are: setting time, injectability and cohesion. The compressive strength of selected cement samples was determined. Thermal treatment improves injectability, but significantly prolongs setting time and reduces cohesiveness. Treatment of powder particles with deionized water increases setting time, but also significantly reduces injectability. It was not possible to significantly increase powder liquid ratio (from 1.75 to 2.00), if thermally treated powders were used. It was found that reduction of particle size, under certain conditions, can increase the injectability of cements. Powder preparation methods do not significantly affect the compression strength of cement, but fast setting upon the contact water based fluids is necessary to obtain cohesive cements.

Novel method for the obtainment of nanostructured calcium phosphate cements: Synthesis, mechanical strength and cytotoxicity

The calcium phosphate cements have a large number of advantages regarding its use in orthopedics and traumatology, being the most prominent its biocompatibility and bioactivity, which allows the osteoconductive of bone tissue and in situ hardening, allowing greater ease of handling. However, the use of conventional synthesis methods, e.g. solid state reactions, brings great difficulty to the obtainment of highly pure α-tricalcium phosphate phase. In this work, the use of the solution combustion synthesis method allowed to synthesize nanostructured α-tricalcium phosphate with high purity. Further studies on pH influence, fuel nature (urea or glycine) and fuel ratio (0.75, 1.0, 1.5 and 2.0) allowed to define the best synthesis parameters (pH 1.5 and urea fuel content in two times higher than the stoichiometric). After choosing the best parameters to the obtainment of highly pure α-tricalcium phosphate, we studied the feasibility of their use as calcium phosphate cement (CFC) by studying the influence of particle size by increasing the milling time from 30 to 180 min. The better results were found for the milling time of 180 min. Compressive strengths up to 30.4 MPa were obtained for this formulation. However, after soaking the calcium phosphate cements in simulated blood plasma (SBF), in growing times up to 28 days, a decrease in compressive strength was noticed, which is an indicative of the high solubility of the α-tricalcium phosphate powders obtained by solution combustion synthesis. The synthesized powder did not show any cytotoxicity to the tested cells.

Effect of Calcium Phosphate Cements on Growth and Odontoblastic Differentiation in Human Dental Pulp Cells

Objective Calcium phosphate cements (CPCs) are an interesting class of bone substitute materials. However, the biological effects of CPCs have not been well studied in human dental pulp cells (HDPCs). The purpose of this study was to investigate the effects of CPCs on the mechanical properties, growth, and odontoblastic differentiation in HDPCs compared with Portland cement (PC) and mineral trioxide aggregate (MTA). Methods Experimental CPCs either containing chitosan (Ch-CPC) or without chitosan (CPC) were composed from the α-tricalcium phosphate powder. Setting time, compressive strength measurements, cell growth, alkaline phosphatase (ALP) activity, the levels of messenger RNA for differentiation-related genes, and mineralization of the HDPCs on various cements were assessed. Results The setting time for CPC-Ch was 7.5 minutes, which was significantly less than the 8.6 minutes for the CPC. On the seventh day of immersion, the compressive strength of CPC-CH reached 13.1 MPa, which was higher than 10.8 MPa of CPC. CPC and Ch-CPC-treated cells showed decreased cell proliferation but increased the levels of ALP activity, enhanced mineralized nodule formation, and upregulated odontoblastic markers messenger RNA including osteonectin, osteopontin, bone sialoprotein, dentin matrix protein-1, matrix extracellular phosphoglycoprotein, and dentin sialophosphoprotein (DSPP), compared with untreated control. The response of CPC and CP-CPC were similar to that of PC and MTA. However, the adhesion, growth, and differentiation in Ch-CPC–treated cells were similar to that in the CPC. Conclusion CPC may be useful for pulp-capping applications based on its abilities to promote HDPC differentiation.

A physical approach to modify the hydraulic reactivity of α-tricalcium phosphate powder

A microsized α-tricalcium phosphate (α-TCP) powder was calcined at various temperatures (350 °C < T < 800 °C) for various durations (1–24 h) and the resulting physico-chemical and reactivity changes were measured. Without calcination, the α-TCP powder started reacting within minutes after contacting a 0.2 M Na 2HPO 4 solution as measured by isothermal calorimetry. The overall reaction was finished within a few days. After calcination at 350 °C ⩽ T ⩽ 550 °C for 24 h, no significant changes in the crystalline composition, crystallite size, particle size or specific surface area were noticed. However, the powder reactivity was progressively changed. More specifically, the hydraulic reaction of the powders calcined at 500 and 550 °C only started after 2–3 h whereas the overall hydraulic reaction was only slightly postponed, suggesting that physical or chemical changes had occurred at the particle surface. As mainly physical changes were detected at the particle surface during calcination at 500 °C, it was speculated that the appearance of this reaction delay (= induction time) was due to the disappearance of surface defects during the calcination step, i.e. to the need to create surface defects to induce dissolution and hence reaction.

Synthesis of chitosan/brushite powders for bone cement composites

Recently, calcium phosphate cements have been considered in medicine and dentistry because of their excellent biocompatibility and advantages in situ handling and shaping abilities. Nevertheless, low mechanical strength of these cements limits wider the clinical applications. The aim of this work was the synthesis of chitosan/brushite powders for preparing the calcium phosphate cements. The synthesis of brushite was carried out in the chitosan matrix from calcium chloride and sodium phosphate at moderate pH of 4 and then dried from 60 to 100°C. The obtained powders were characterized by XRD and FT-IR technique. With increasing the drying temperature, phase of dicalcium phosphate anhydrous increased. Moreover, FTIR indicate the bands attributable to chitosan and brushite. The brushite synthesized using this route was used to be a starting powder for calcium phosphate cement (CPC). To prepare CPC, the mixture of chitisan/brushite and α-tricalcium phosphate powders was mixed with various liquid phases and then cured at 100% humidity for 7 d The compressive strength of the cements was determined to evaluate the potential use for the bone cement. Cements formed with chitosan/brushite dried at 100°C had the greatest compressive strength of all cement tests. The improvement of compressive strength seemed to depend on the affinity of chitosan incorporated in the cements.

Hydrolysis and cytocompatibility of zinc-containing α-tricalcium phosphate powder

Zinc is an essential trace element with stimulatory effects on bone formation in vitro and in vivo. In order to apply zinc-containing α-tricalcium phosphate (αZnTCP) to αTCP-based calcium phosphate cement, αZnTCP powders containing various amounts of zinc were prepared and the optimum zinc content was examined from the viewpoints of hydrolysis property and cytocompatibility. Single-phase αZnTCP containing zinc from 0.00 to 1.26 wt.% was obtained by heating zinc-containing β-tricalcium phosphate at 1450 °C. At a zinc content of 0.11 wt.%, there was no significant difference in the amount of calcium-deficient low-crystalline apatite formed by hydrolysis between pure αTCP and αZnTCP. The hydrolysis of αZnTCP was significantly retarded by incorporating zinc at or more than 0.26 wt.% due to the inhibitory effect of zinc on the crystal growth of apatite. The MC3T3-E1 cell densities cultured with pure αTCP and 0.11 Zn wt.% αZnTCP powders showed no significant difference in the range of powder dose from 10 to 1000 μg mL −1. The result indicated that the cytocompatibility of pure αTCP powder was comparable to that of αZnTCP at the zinc content of 0.11 wt.%. Therefore, the optimum zinc content of αZnTCP powder is less than 0.26 wt.%, and preferably at or less than 0.11 wt.% to apply to an αTCP-based calcium phosphate cement.