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Calcium phosphate biomaterials can be classified as polycrystalline ceramics. Hydroxyapatite is one kind of calcium phosphate biomaterials which is also a mineral component in hard tissue, especially dental and bones. Hydroxyapatite has low chemical stability at high temperatures and low durability in an acidic environment. On the other hand, fluorhydroxyapatite has good chemical stability at high temperatures as well as the nature of its bioactivity. Fluorhydroxyapatite is made by adding F to replace some OH functional groups in hydroxyapatite. In this research, fluorhydroxyapatite was synthesized through precipitation method and microwave assistant with sintering temperatures of 600°C, 800°C, and 1000°C. Based on the characterization using an x-ray diffractometer, the results showed that at 1000°C sintering temperature, the samples have a higher intensity of fluorapatite and fewer impurities than other samples sintered at 800°C and 600°C. Fourier Transform Infra-Red (FTIR) analysis shows that similar functional groups appeared in the samples with all sintering temperatures. Conductivity evaluation shows that the conductivity values of the samples were inversely proportional to the sintering temperatures. The morphology of the samples not so clearly seen due to agglomeration, but it can be observed that fluorhydroxyapatite is flat-shaped needle-like or rod-shaped. [ABSTRACT FROM AUTHOR]

The objective of this research was to study the degradation and biological characteristics of the three-dimensional porous composite scaffold made of poly(lactic-co-glycolic acid)/nano-fluorhydroxyapatite microsphere using sintering method for potential bone tissue engineering. Our previous experimental results demonstrated that poly(lactic-co-glycolic acid)/nano-fluorhydroxyapatite composite scaffold with a ratio of 4:1 sintered at 90ºC for 2 h has the greatest mechanical properties and a proper pore structure for bone repair applications. The weight loss percentage of both poly(lactic-co-glycolic acid)/nano-fluorhydroxyapatite and poly(lactic-co-glycolic acid) scaffolds demonstrated a monotonic trend with increasing degradation time, that is, the incorporation of nano-fluorhydroxyapatite into polymeric scaffold could lead to weight loss in comparison with that of pure poly(lactic-co-glycolic acid). The pH change for composite scaffolds showed that there was a slight decrease until 2 weeks after immersion in simulated body fluid, followed by a significant increase in the pH of simulated body fluid without a scaffold at the end of immersion time. The mechanical properties of composite scaffold were higher than that of poly(lactic-co-glycolic acid) scaffold at total time of incubation in simulated body fluid; however, it should be noted that the incorporation of nano-fluorhydroxyapatite into composite scaffold leads to decline in the relatively significant mechanical strength and modulus during hydrolytic degradation. In addition, MTT assay and alkaline phosphatase activity results defined that a general trend of increasing cell viability was seen for poly(lactic-co-glycolic acid)/nano-fluorhydroxyapatite scaffold sintered by time when compared to control group. Eventually, experimental results exhibited poly(lactic-co-glycolic acid)/nano-fluorhydroxyapatite microsphere-sintered scaffold is a promising scaffold for bone repair. [ABSTRACT FROM AUTHOR]

A novel graphene oxide-based fluorhydroxyapatite (GO/FHA) composite is prepared using an in situ chemical synthesis method. The mechanical properties, chemical stability, in vitro bioactivity, and antibacterial properties of the as-synthesized GO/FHA composites with different GO amounts are reported. The result shows that the mechanical properties of the composites are strongly dependent on the adding amount of GO. The result of chemical stability indicates that the substitution of fluorine (F) into the hydroxyapatite (HA) crystal has a positive effect on the dissolution resistance. The in vitro bioactivity assessment shows that the osteoblast proliferation and differentiation ability on GO/FHA composites are improved. [ABSTRACT FROM AUTHOR]

Objectives: Dentin hypersensitivity (DH) is a prevalent problem. This study aimed to formulate a paste using fluorhydroxyapatite (FA) crystals dispersed in different carriers to treat DH. The ability to occlude patent dentinal tubules and to release ions was investigated. Materials and methods: Twenty percent FA/sodium alginate, 40 % FA/poly(hydroxyethyl methacylate(HEMA)), and 40 % FA/poly(DMA-co-MEA) were applied to etched dentin samples and examined with scanning electron microscopy (SEM) to determine the degree of tubule occlusion. Fluoride electrode was used to measure F release and spectroscopy to evaluate Ca and PO release. The cytotoxicity of the synthesized poly(DMA-co-MEA) gel was tested. Kruskall-Wallis test was used to test the differences in ion release between the groups. Results: FA/poly(DMA-co-MEA) paste obstructed up to 80 % of the dentinal tubules, while the coverage was up to 70 % for FA/poly(HEMA) and less than 50 % for FA/sodium alginate. Fluoride and Ca release was the highest for FA/P(HEMA), 7.2 ± 0.7 and 139.8 ± 32.5 ppm, respectively. The highest concentration of PO was 46.2 ± 16.4 ppm for FA/Sodium alginate. No statistical significance was found. Conclusions: FA/Poly(DMA-co-MEA) and FA/poly(HEMA) pastes may offer immediate short-term relief of DH because of their ability to occlude the tubules and adhere to wet dentin surfaces. The release of the F, Ca, and PO ions may offer long-term relief by forming a mineral barrier both within the dentinal tubules and on the dentin surface. Clinical significance: The tested materials may offer a long-term treatment for DH. [ABSTRACT FROM AUTHOR]

Introduction: Bone tissue engineering proposes a suitable way to regenerate lost bones. Different materials have been considered for use in bone tissue engineering. Hydroxyapatite (HA) is a significant success of bioceramics as a bone tissue repairing biomaterial. Among different bioceramic materials, recent interest has been risen on fluorinated hydroxyapatites, (FHA, Ca10(PO4)6Fx(OH)2-x). Fluorine ions can promote apatite formation and improve the stability of HA in the biological environments. Therefore, they have been developed for bone tissue engineering. The aim of this study was to synthesize and characterize the FHA nanopowder via mechanochemical (MC) methods. Materials and Methods: Natural hydroxyapatite (NHA) 95.7 wt.% and calcium fluoride (CaF2) powder 4.3 wt.% were used for synthesis of FHA. MC reaction was performed in the planetary milling balls using a porcelain cup and alumina balls. Ratio of balls to reactant materials was 15:1 at 400 rpm rotation speed. The structures of the powdered particles formed at different milling times were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results: Fabrication of FHA from natural sources like bovine bone achieved after 8 h ball milling with pure nanopowder. Conclusion: F- ion enhances the crystallization and mechanical properties of HA in formation of bone. The produced FHA was in nano-scale, and its crystal size was about 80-90 nm with sphere distribution in shape and size. FHA powder is a suitable biomaterial for bone tissue engineering. [ABSTRACT FROM AUTHOR]

Fluorhydroxyapatite/strontium-substituted hydroxyapatite (FHA/SrHA) biphasic coatings with F and Sr elements incorporated simultaneously into one coating layer were prepared on titanium substrate via colloidal sol-gel method. The bioactivity of the as-prepared FHA/SrHA biphasic coatings was evaluated in vitro by immersion in simulated body fluid (SBF). All the biphasic coatings exhibited great ability to induce apatite precipitation on their surfaces. In vitro cell responses were evaluated using osteoblast-like MG63 cells in terms of cell proliferation and differentiation (alkaline phosphatase activity and osteocalcin level). The biphasic coatings show significantly positive effects on the viability and functional activity of osteoblastic cells with clear evidence that an optimum SrHA amount dose exists, indicating that the coexistence of FHA and SrHA had a synergistic stimulatory effect. This finding suggests the potential use of this colloidal sol-gel derived FHA/SrHA biphasic coatings for hard tissue applications. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 621-627, 2014. [ABSTRACT FROM AUTHOR]

This study is aimed at the development of a method to fabricate porous spherical hydroxyapatite (HA)—fluorapatite (FA) granules. The method to produce porous granules is based on liquid immiscibility effect. A suspension of HA–FA powder mixtures in aqueous solution of gelatin and oil as a dispersion media were used. By stirring the mixtures of these immiscible liquids, granules of 50–200 μm diameter can easily be produced. The granules were characterized with respect to their microstructure, phase composition and specific area. In vitro testing of human plasma protein adsorption onto the granules of HA and fluorhydroxyapatite were performed. No kind of difference in the dynamic protein adsorption between pure HA and the HA up to 10 wt% FA materials has been revealed. [Copyright &y& Elsevier]

The kinetics of seeded crystal growth of calcium apatites were studied in dilute supersaturated solutions at various levels of fluoride concentrations. Initial precipitation rates were enhanced by fluoride concentrations higher than 0.05 ppm. The analytical results are consistent with the precipitation of fluoridated hydroxyapatites, CaF-(OH)(PO), FHA. The degree of fluoridation, X, appears to be determined by the activity of HF in solution, which varies for the various initial fluoride levels but remains fairly constant during precipitation. Thus the composition of the precipitating phase was the same for a given solution whether 25 or 10 mg of hydroxyapatite was added as seeds. All the experimental results are consistent with the BCF theory, which relates the mean linear rate of growth, R, to the supersaturation, DS, by the expression R=CT(DS-1)1n(DS)tanh(C/T 1n DS), in which DS is the supersaturation defined by mean molar activities with respect to the precipitating FHA, T the absolute temperature, and C and C are constants calculated from the experimental results. Consequently, the crystal growth appears to take place in surface kinks and to be controlled by surface diffusion. Since crystal growth in most biological systems takes place at fluoride concentrations within the experimental range used, it seems probable that it occurs along the model advanced in the present investigation. [ABSTRACT FROM AUTHOR]

The effect of fluoride derived from fluorhydroxyapatite (FHAp) minerals on bacterial glycolysis under aerobic and strictly anaerobic conditions was studied to validate the claims that this mineral could be used as a reservoir of fluoride in plaque. To isolate the direct effect of fluoride on bacterial glycolysis from that of an indirect pH-buffering effect of hydroxyl or phosphate ions which are also dissolved from the mineral, we equalized the pH-fall time course of reactions by manually adding KOH or HCI. This ensured that pH effects on glycolysis were minimized. Under controlled pH-fall and strictly anaerobic conditions, fluoride derived from the dissolution of FHAp containing more than 30,100 ppm fluoride (i.e., when the substitution of OH by F in the mineral was greater than 80%) had a direct inhibitory effect on lactic acid production in Streptococcus mutans. Under free pH-fall and strictly anaerobic conditions, increasing amounts of fluoride in FHAp (starting as low as 2000 ppm fluoride), appeared to have a pronounced indirect inhibitory effect on lactic acid production. This was probably mediated through a reducing pH buffer effect of the mineral. Even in the presence of high-fluoride FHAp, only 0.01 to 0.025 mmol/L fluoride was found in the reaction mixtures, a probable result of non-stoichiometric dissolution of FHAp. In spite of such low levels of fluoride, marked inhibitory effects on bacterial glycolysis were demonstrated. The results of this study suggest that high- fluoride FHAp may serve as a reservoir of fluoride for the inhibition of anaerobic acid production by S. mutans. [ABSTRACT FROM AUTHOR]