Papers by Keyword: Brushite

Abstract: The results of the studies aimed at increasing the water resistance of the pressed building materials based on gypsum and magnesia binders due to their modification with active dispersed fillers from secondary resources are presented. The gypsum binder modification was carried out by the joint introduction of carbonate-containing sludge from it into the chemical treatment of thermal power plants and monoammonium phosphate, and of magnesia cement - silica fume and finely ground burnt mines. Physical and mechanical characteristics of the materials’ control samples were determined according to the standards and generally accepted methods. The increase in water resistance of the pressed modified composites was evaluated by changing the softening coefficient. It is shown that when using gypsum binders, an increase in the water resistance of products based on them can be achieved by changing the structure formation of the pressed material and the formation on the elements’ surface of its fine-crystalline structure of the sparingly soluble calcium phosphates’ screening protective films. The increase in water resistance of pressed products made of modified magnesia binders is explained by the appearance of insoluble hydro silicates, hydro aluminates and hydro aluminosilicates of magnesium, in the structure of the hardened artificial stone as well as the formation of a complex combined structure containing coagulation, condensation and crystallization phases. The technical characteristics of the materials obtained are sufficient for their use, in particular, in the building envelope. The possibility of replacing a significant amount of binders with secondary resources has been identified. This allows not only to increase the water resistance of the pressed products on the basis of the proposed modified binders, but also to reduce their cost, as well as free up the land allocated for dumps.

Abstract: Brushite cement has advantages such as fast setting, high reactivity and good injectability over apatitic cements. To induce the bioactivity of brushite cements, the goal was to convert it into a bone-like low crystalline carbonate apatite. To achieve this induced transformation, potassium and magnesium were used as dopants which were claimed to be effective in the literature. The cements were immersed for 2 periods of time: 1 day and 6 weeks in Tas-Simulated-Body-Fluid (Tas-SBF) due to its excellent biomimetic properties with its adjusted HCO3- and Cl- ionic rates according to human-blood-plasma. 5% of potassium (to calcium sites) seemed to be more effective over magnesium modification. The aim of this study is to define an optimal composition in terms of transforming brushite into apatite.

Abstract: The incorporation of protein based polymeric materials with calcium phosphate (CaP) coatings can provide excellent biological characteristics and biocompatibility with its bone-like protein-CaP composition. Calcium chloride-ethanol catalysed hydrolysis reaction and wet precipitation method was used to prepare silk solution and to precipitate brushite respectively to produce the brushite/silk composite powder. FTIR analyses showed that brushite absorption bands were prominent, overlapping the less intense N-H bands in silk. The most distinct absorptions from the silk were N-H bands. 1g of silk additive to the 300 ml of solution media resulted in arbitrary particle attachment onto brushite crystal surface; most of the brushite particles were covered by the silk β-sheets phase.

Abstract: The injection behavior of β-tricalcium phosphate (Ca₃(PO₄)₂: β-TCP) based cement was improved through the granulation of β-TCP. Dense β-TCP granules were obtained by heat treatment after spray drying. The fraction of injected paste under loaded mass in the syringe was measured while varying the granular fraction of β-TCP and the heat treatment temperature. The increase in granular fraction and heating treatment temperature reduced the amount of setting agent required to wet the granules. As the surplus setting agent could be used in the powdery β-TCP to reduce the viscosity, improved injectability was achieved. Inappropriate setting by the excessive setting agent was not observed and the cements tested exhibited normal setting behavior by forming a brushite phase.

Abstract: The aim of this research is to identify the optimum conversion time of brushite to monetite. Obtaining optimum conversion time is important to reduce energy consumption and time for cost saving. The presence of distilled water in brushite powder with assistant of temperature and pressure for 45 min under hydrothermal treatment yielded to monetite. The constant temperature at 160 °C with 15, 30, 45 and 60 min for treatment times was used to execute the synthesis of monetite. The treatment times were extended until 2, 6 and 8 h to determine the transformation of phase. The XRD and SEM analysis were used for phase and morphology identifications. The XRD result at 45 min treatment time showed monetite peaks appeared greatly as compared to pure brushite. Whereas, the SEM results showed the existent of polygonal morphology that may referred to the monetite phase. The results obtained in this study conclude that at 45 min treatment time is the optimum conversion time from brushite to monetite

Abstract: The increasing interest in the use of brushite and monetite as resorbable calcium phosphate cements or graft materials is related to the fact of these phases being metastable under physiological environment, with higher solubility than hydroxyapatite phase. In this study, X-ray diffraction (XRD) and scanning electron microscopy with field emission gun (FEG-SEM) analyses were performed in order to assess the temperature influence on the production of calcium phosphate coatings by a chemical deposition method. Titanium substrates were successfully coated with brushite and monetite by a chemical deposition method and a brushite-monetite transformation was assessed with the increasing temperature. Brushite deposition was kinetically favored at low temperatures, whereas monetite was the major phase at higher temperatures.

Abstract: Nowadays, bioactive coatings or modifications on titanium surface have been tested in vitro and in vivo. In this study, two types of calcium phosphate coatings were produced by a chemical deposition method and their bioactivity assay in cell culture medium were investigated. The calcium phosphate coatings were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with field emission gun (FEG-SEM) analyses. Titanium substrate was successfully coated with brushite using chemical deposition method and, after a second step of conversion, the hydroxyapatite coating was obtained. The hydroxyapatite coating showed a bioactivity property after 14 days’ incubation in McCoy medium culture.

Abstract: The properties of brushite cement were manipulated by partially replacing β-tricalcium phosphate with dense granular hydroxyapatite (HA). The introduction of HA granules resulted in prolonged setting time as well as reduction of temperature rise during setting. The changes produced by addition of HA granule were useful for drug loading. HA granules, prepared by spray drying, could preserve a meaningful 4.5 wt% of gentamicin sulfate solution. However, HA granules with excessive setting agent resulted in formation of dicalcium phosphate instead of brushite.

Abstract: Brushite bone cement containing a drug was prepared using the dense granular β-tricalciump phospahte (β-TCP) as a starting material. The setting reaction was not significantly affected by loading antibiotics within the granules. Heat treatment of the granule at elevated temperature resulted in the suppression of temperature increase during setting, which provided benefits in drug loading. The amount of gentamicin sulfate infiltrated in the β-TCP granules was determined by thermogravimetric analysis and was found to be meaningful considering the MIC of microorganisms.

Abstract: The cause of the degradation was analyzed by applying the highly humid conditions during the storage of cement composed of β-tricalcium phosphate (β-TCP) and monocalcium phosphate monohydrate (MCPM). For the β-TCP and MCPM stored separately under the humid environment, the mild increase in the setting time was observed, and the product after the setting was entirely dicalcium phosphate dihydrate (CaHPO₄2H₂O: DCPD). However, for the β-TCP and MCPM stored mixed under the same condition, the setting time significantly increased with the period of storage, and the product contained dicalcium phosphate (CaHPO₄: DCP) as major phase, resulting in the loss of setting ability. The formation of DCP could be because of the weak driving force for setting, caused by a feeble supply of water from moisture. As the formation of DCPD requires stronger driving force to overcome the activation barrier, sufficient amount of water is essential. Humid environment during the storage decreased the driving force by the formation of DCP, and the driving force to produce DCPD was lost during the actual setting.