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Takashi Nakamura - One of the best experts on this subject based on the ideXlab platform.

  • Formation of a bioactive calcium titanate layer on gum metal by chemical treatment
    Journal of Materials Science: Materials in Medicine, 2012
    Co-Authors: Seiji Yamaguchi, Takashi Nakamura, Hiroaki Takadama, Takashi Kizuki, Tomiharu Matsushita, Tadashi Kokubo
    Abstract:

    The so-called gum metal with the composition Ti–36Nb–2Ta–3Zr–0.3O is free from cytotoxic elements and exhibits a low elastic modulus as well as high mechanical strength. In the present study, it was shown that this alloy exhibited a high capacity for Apatite Formation in a simulated body fluid when subjected to 1 M NaOH treatment, 100 mM CaCl2 treatment, heat treatment at 700°C, and then hot water treatment. The high Apatite Formation was attributed to the CaTi2O5 which was precipitated on its surface, and found to be maintained even in a humid environment over a long period. The treated surface exhibited high scratch resistance, which is likely to be useful in clinical applications. The surface treatment had little effect on the unique mechanical properties described above. These results show that gum metal subjected to the present surface treatments exhibits a high potential for bone-bonding, which will be useful in orthopedic and dental implants.

  • Apatite Formation on anodized ti 6al 4v alloy in simulated body fluid
    Metals and Materials International, 2010
    Co-Authors: Xinyu Cui, Tadashi Kokubo, Hyunmin Kim, Masakazu Kawashita, Longbao Wang, Tianying Xiong, Takashi Nakamura
    Abstract:

    Titania layers were successfully prepared on the surfaces of Ti-6Al-4V alloy via anodic oxidation in H(2)SO(4) or Na(2)SO(4) solutions at room temperature. The titania layers consisted of pure rutile or a mixture of anatase and rutile structures after the Ti-6Al-4V alloy had been anodized in 1.0 M H(2)SO(4) solution at 150 V or 0.5M Na(2)SO(4) solution at 100 or 130 V. Good Apatite-forming ability was demonstrated in simulated body fluid. However, surface layers with mainly titanium metallic phase or a pure anatase structure did not possess the ability to induce Apatite Formation. Anodic oxidation is an effective method to prepare bioactive Ti-6Al-4V alloy that can be used as an artificial bone substitute under load-bearing applications.

  • bonelike Apatite Formation induced on zirconia gel in a simulated body fluid and its modified solutions
    Journal of the American Ceramic Society, 2004
    Co-Authors: Masaki Uchida, Tadashi Kokubo, Hyunmin Kim, Fumiaki Miyaji, Takashi Nakamura
    Abstract:

    Formation of bonelike Apatite on zirconia gel in a simulated body fluid (SBF) with ion concentrations almost equal to those in human blood plasma, in modified SBF solutions to have increased pH values, and modified SBF solutions to have increased concentrations of calcium and phosphate ions has been investigated. The zirconia gel forms Apatite on its surface in SBF, indicating that Zr-OH groups, abundant on the gel, act as effective Apatite nucleation centers. Apatite Formation is accelerated by increases in pH and in the concentration of calcium and phosphate ions, which is explained by an increase in the ionic activity product of the Apatite in the SBF. These results suggest that zirconia ceramics may exhibit a bone-bonding ability by forming an Apatite layer on their surfaces in the living body when they are modified to have many Zr-OH groups on their surfaces.

  • Apatite Formation on non woven fabric of carboxymethylated chitin in sbf
    Biomaterials, 2004
    Co-Authors: Tadashi Kokubo, Masakazu Kawashita, Masayuki Hanakawa, Masahiko Minoda, Toshiyuki Beppu, Takeaki Miyamoto, Takashi Nakamura
    Abstract:

    Abstract Chitin fibres constituting a non-woven fabric were carboxymethylated in monochloro acetic acid and treated with saturated Ca(OH) 2 aqueous solution. Within 3 days in a simulated body fluid with pH value and ion concentrations nearly equal to those of human blood plasma, a bonelike Apatite layer formed on the surface of fibres of the treated fabric. The Apatite–chitin fibre composite thus prepared is expected to be useful as a flexible bioactive bone-repairing material.

  • surface potential change in bioactive titanium metal during the process of Apatite Formation in simulated body fluid
    Journal of Biomedical Materials Research Part A, 2003
    Co-Authors: Teruyuki Himeno, Tadashi Kokubo, Masakazu Kawashita, Takashi Nakamura
    Abstract:

    Bioactive titanium metal can be prepared by NaOH and heat treatments that present the metal with a graded bioactive surface layer of amorphous sodium titanate. This study used laser electrophoresis together with transmission electron microscopy (TEM) and energy-dispersive X-ray microanalysis (EDX) to relate the surface potential change of the bioactive titanium metal with its surface structural change in simulated body fluid (SBF). The surface potential of the metal was highly negative immediately after immersion in SBF. With increasing soaking time, the surface potential increased, revealing a maximum positive value, and then decreased to a constant negative value. TEM-EDX showed that immediately after immersion in SBF, the metal surface formed Ti-OH groups by exchanging Na+ ions in the surface sodium titanate with H3O+ ions in the fluid. Thereafter, with increasing soaking time the metal surface formed an amorphous calcium titanate, then an amorphous calcium phosphate, and, finally, Apatite with bone-like composition and structure. These results indicate that the process of Apatite Formation on bioactive titanium metal is initiated by the Formation of Ti-OH groups with negative charges that interact with calcium ions with positive charges to form calcium titanate. The calcium titanate gains a positive charge and later interacts with phosphate ions with negative charges, forming amorphous calcium phosphate. The amorphous calcium phosphate eventually transforms and stabilizes into bone-like crystalline Apatite with a negative charge. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 1305–1309, 2003

Tadashi Kokubo - One of the best experts on this subject based on the ideXlab platform.

  • Formation of a bioactive calcium titanate layer on gum metal by chemical treatment
    Journal of Materials Science: Materials in Medicine, 2012
    Co-Authors: Seiji Yamaguchi, Takashi Nakamura, Hiroaki Takadama, Takashi Kizuki, Tomiharu Matsushita, Tadashi Kokubo
    Abstract:

    The so-called gum metal with the composition Ti–36Nb–2Ta–3Zr–0.3O is free from cytotoxic elements and exhibits a low elastic modulus as well as high mechanical strength. In the present study, it was shown that this alloy exhibited a high capacity for Apatite Formation in a simulated body fluid when subjected to 1 M NaOH treatment, 100 mM CaCl2 treatment, heat treatment at 700°C, and then hot water treatment. The high Apatite Formation was attributed to the CaTi2O5 which was precipitated on its surface, and found to be maintained even in a humid environment over a long period. The treated surface exhibited high scratch resistance, which is likely to be useful in clinical applications. The surface treatment had little effect on the unique mechanical properties described above. These results show that gum metal subjected to the present surface treatments exhibits a high potential for bone-bonding, which will be useful in orthopedic and dental implants.

  • Apatite Formation on anodized ti 6al 4v alloy in simulated body fluid
    Metals and Materials International, 2010
    Co-Authors: Xinyu Cui, Tadashi Kokubo, Hyunmin Kim, Masakazu Kawashita, Longbao Wang, Tianying Xiong, Takashi Nakamura
    Abstract:

    Titania layers were successfully prepared on the surfaces of Ti-6Al-4V alloy via anodic oxidation in H(2)SO(4) or Na(2)SO(4) solutions at room temperature. The titania layers consisted of pure rutile or a mixture of anatase and rutile structures after the Ti-6Al-4V alloy had been anodized in 1.0 M H(2)SO(4) solution at 150 V or 0.5M Na(2)SO(4) solution at 100 or 130 V. Good Apatite-forming ability was demonstrated in simulated body fluid. However, surface layers with mainly titanium metallic phase or a pure anatase structure did not possess the ability to induce Apatite Formation. Anodic oxidation is an effective method to prepare bioactive Ti-6Al-4V alloy that can be used as an artificial bone substitute under load-bearing applications.

  • how useful is sbf in predicting in vivo bone bioactivity
    Biomaterials, 2006
    Co-Authors: Tadashi Kokubo, Hiroaki Takadama
    Abstract:

    The bone-bonding ability of a material is often evaluated by examining the ability of Apatite to form on its surface in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. However, the validity of this method for evaluating bone-bonding ability has not been assessed systematically. Here, the history of SBF, correlation of the ability of Apatite to form on various materials in SBF with their in vivo bone bioactivities, and some examples of the development of novel bioactive materials based on Apatite Formation in SBF are reviewed. It was concluded that examination of Apatite Formation on a material in SBF is useful for predicting the in vivo bone bioactivity of a material, and the number of animals used in and the duration of animal experiments can be reduced remarkably by using this method.

  • bonelike Apatite Formation induced on zirconia gel in a simulated body fluid and its modified solutions
    Journal of the American Ceramic Society, 2004
    Co-Authors: Masaki Uchida, Tadashi Kokubo, Hyunmin Kim, Fumiaki Miyaji, Takashi Nakamura
    Abstract:

    Formation of bonelike Apatite on zirconia gel in a simulated body fluid (SBF) with ion concentrations almost equal to those in human blood plasma, in modified SBF solutions to have increased pH values, and modified SBF solutions to have increased concentrations of calcium and phosphate ions has been investigated. The zirconia gel forms Apatite on its surface in SBF, indicating that Zr-OH groups, abundant on the gel, act as effective Apatite nucleation centers. Apatite Formation is accelerated by increases in pH and in the concentration of calcium and phosphate ions, which is explained by an increase in the ionic activity product of the Apatite in the SBF. These results suggest that zirconia ceramics may exhibit a bone-bonding ability by forming an Apatite layer on their surfaces in the living body when they are modified to have many Zr-OH groups on their surfaces.

  • Apatite Formation on non woven fabric of carboxymethylated chitin in sbf
    Biomaterials, 2004
    Co-Authors: Tadashi Kokubo, Masakazu Kawashita, Masayuki Hanakawa, Masahiko Minoda, Toshiyuki Beppu, Takeaki Miyamoto, Takashi Nakamura
    Abstract:

    Abstract Chitin fibres constituting a non-woven fabric were carboxymethylated in monochloro acetic acid and treated with saturated Ca(OH) 2 aqueous solution. Within 3 days in a simulated body fluid with pH value and ion concentrations nearly equal to those of human blood plasma, a bonelike Apatite layer formed on the surface of fibres of the treated fabric. The Apatite–chitin fibre composite thus prepared is expected to be useful as a flexible bioactive bone-repairing material.

Hyunmin Kim - One of the best experts on this subject based on the ideXlab platform.

  • Apatite Formation on anodized ti 6al 4v alloy in simulated body fluid
    Metals and Materials International, 2010
    Co-Authors: Xinyu Cui, Tadashi Kokubo, Hyunmin Kim, Masakazu Kawashita, Longbao Wang, Tianying Xiong, Takashi Nakamura
    Abstract:

    Titania layers were successfully prepared on the surfaces of Ti-6Al-4V alloy via anodic oxidation in H(2)SO(4) or Na(2)SO(4) solutions at room temperature. The titania layers consisted of pure rutile or a mixture of anatase and rutile structures after the Ti-6Al-4V alloy had been anodized in 1.0 M H(2)SO(4) solution at 150 V or 0.5M Na(2)SO(4) solution at 100 or 130 V. Good Apatite-forming ability was demonstrated in simulated body fluid. However, surface layers with mainly titanium metallic phase or a pure anatase structure did not possess the ability to induce Apatite Formation. Anodic oxidation is an effective method to prepare bioactive Ti-6Al-4V alloy that can be used as an artificial bone substitute under load-bearing applications.

  • bonelike Apatite Formation induced on zirconia gel in a simulated body fluid and its modified solutions
    Journal of the American Ceramic Society, 2004
    Co-Authors: Masaki Uchida, Tadashi Kokubo, Hyunmin Kim, Fumiaki Miyaji, Takashi Nakamura
    Abstract:

    Formation of bonelike Apatite on zirconia gel in a simulated body fluid (SBF) with ion concentrations almost equal to those in human blood plasma, in modified SBF solutions to have increased pH values, and modified SBF solutions to have increased concentrations of calcium and phosphate ions has been investigated. The zirconia gel forms Apatite on its surface in SBF, indicating that Zr-OH groups, abundant on the gel, act as effective Apatite nucleation centers. Apatite Formation is accelerated by increases in pH and in the concentration of calcium and phosphate ions, which is explained by an increase in the ionic activity product of the Apatite in the SBF. These results suggest that zirconia ceramics may exhibit a bone-bonding ability by forming an Apatite layer on their surfaces in the living body when they are modified to have many Zr-OH groups on their surfaces.

  • preparation of bioactive titanium metal via anodic oxidation treatment
    Biomaterials, 2004
    Co-Authors: Bangcheng Yang, Hyunmin Kim, Xingdong Zhang, Masaiki Uchida, Tadashi Kokubo
    Abstract:

    Titania with specific structures of anatase and rutile was found to induce Apatite Formation in vitro. In this study, anodic oxidation in H(2)SO(4) solution, which could form anatase and rutile on titanium metal surface by conditioning the process, was employed to modify the structure and bioactivity of biomedical titanium. After the titanium metal was subjected to anodic oxidation treatment, thin film X-ray diffraction and scanning electron microscopy results showed the titanium metals surfaces were covered by porous titania of anatase and/or rutile. In simulated body fluid (SBF), the titanium anodically oxidized under the conditions with spark-discharge could induce Apatite Formation on its surface. The induction period of Apatite Formation was decreased with increasing amount of either anatase or rutile by conditioning the anodic oxidation. After the titanium metal, anodically oxidized under the conditions without spark-discharge, was subjected to heat treatment at 600 degrees C for 1 h, it could also induce Apatite Formation in SBF because the amount of anatase and/or rutile was increased by the heat treatment. Our results showed that induction of Apatite-forming ability on titanium metal could be attained by anodic oxidation conjoined with heat treatment. So it was believed that anodic oxidation in H(2)SO(4) solution was an effective way to prepare bioactive titanium.

  • a comparative study between in vivo bone ingrowth and in vitro Apatite Formation on na2o cao sio2 glasses
    Biomaterials, 2003
    Co-Authors: Shunsuke Fujibayashi, Tadashi Kokubo, Masashi Neo, Hyunmin Kim, Takashi Nakamura
    Abstract:

    This study compared in vivo bioactivity with the in vitro Apatite-forming ability of biomaterials. Granules of five kinds of P(2)O(5)-free Na(2)O-CaO-SiO(2) glasses, showing different Apatite-forming ability in simulated body fluid (SBF), were implanted into a defect on the femoral condyle of rabbits. Bone ingrowth was evaluated using scanning electron microscopy among five kinds of glasses at 1, 2, 3, 6, and 12 weeks. Quantitative analysis was performed measuring the depth of new bone ingrowth from the periphery. In addition, the total areas of newly formed bone among glass particles were examined at 3 and 6 weeks using confocal laser scanning microscopy (CLSM) after weekly administration of fluorescent calcein. The depth of bone ingrowth among glass particles increased in proportion to their Apatite-forming ability in vitro. The CLSM study showed a correlation between the quantities of labeled newly formed bone and in vitro Apatite-forming ability. In the P(2)O(5)-free Na(2)O-CaO-SiO(2) glasses, the periods within 3-6 days for inducing Apatite in SBF considered a necessary condition to convey bioactivity in vivo, and in vivo evaluations at 2-3 weeks is important to determine this. The in vivo bioactivity was precisely reproduced by Apatite-forming ability in SBF. Therefore, evaluating Apatite Formation in SBF is a good screening test for the in vivo bioactivity of materials, resulting in reduction of the need for animal sacrifices and savings in experimental time.

  • structural dependence of Apatite Formation on titania gels in a simulated body fluid
    Journal of Biomedical Materials Research Part A, 2003
    Co-Authors: Masaki Uchida, Tadashi Kokubo, Hyunmin Kim, Shunsuke Fujibayashi, Takashi Nakamura
    Abstract:

    The Apatite-forming ability of titania gels with different structures has been investigated in a simulated body fluid with ion concentrations nearly equal to those of human blood plasma. Titania gels with an amorphous structure or with an anatase or rutile structure were prepared by the sol-gel process with a subsequent heat treatment at various temperatures. The titania gels with an amorphous structure did not induce Apatite Formation on their surfaces in the simulated body fluid, whereas gels with an anatase or rutile structure induced Apatite Formation on their surfaces. The deposition of Apatite was more pronounced on the anatase gels than on the rutile gels. This indicates that a specific structure of titania is effective in inducing Apatite Formation in a body environment. Such a specific structure was assumed in this study to be the crystalline planar arrangement in the anatase structure, which facilitates epitaxy of the Apatite crystal.

Hiroaki Takadama - One of the best experts on this subject based on the ideXlab platform.

  • Formation of a bioactive calcium titanate layer on gum metal by chemical treatment
    Journal of Materials Science: Materials in Medicine, 2012
    Co-Authors: Seiji Yamaguchi, Takashi Nakamura, Hiroaki Takadama, Takashi Kizuki, Tomiharu Matsushita, Tadashi Kokubo
    Abstract:

    The so-called gum metal with the composition Ti–36Nb–2Ta–3Zr–0.3O is free from cytotoxic elements and exhibits a low elastic modulus as well as high mechanical strength. In the present study, it was shown that this alloy exhibited a high capacity for Apatite Formation in a simulated body fluid when subjected to 1 M NaOH treatment, 100 mM CaCl2 treatment, heat treatment at 700°C, and then hot water treatment. The high Apatite Formation was attributed to the CaTi2O5 which was precipitated on its surface, and found to be maintained even in a humid environment over a long period. The treated surface exhibited high scratch resistance, which is likely to be useful in clinical applications. The surface treatment had little effect on the unique mechanical properties described above. These results show that gum metal subjected to the present surface treatments exhibits a high potential for bone-bonding, which will be useful in orthopedic and dental implants.

  • how useful is sbf in predicting in vivo bone bioactivity
    Biomaterials, 2006
    Co-Authors: Tadashi Kokubo, Hiroaki Takadama
    Abstract:

    The bone-bonding ability of a material is often evaluated by examining the ability of Apatite to form on its surface in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. However, the validity of this method for evaluating bone-bonding ability has not been assessed systematically. Here, the history of SBF, correlation of the ability of Apatite to form on various materials in SBF with their in vivo bone bioactivities, and some examples of the development of novel bioactive materials based on Apatite Formation in SBF are reviewed. It was concluded that examination of Apatite Formation on a material in SBF is useful for predicting the in vivo bone bioactivity of a material, and the number of animals used in and the duration of animal experiments can be reduced remarkably by using this method.

  • x ray photoelectron spectroscopy study on the process of Apatite Formation on a sodium silicate glass in simulated body fluid
    Journal of the American Ceramic Society, 2002
    Co-Authors: Hiroaki Takadama, Tadashi Kokubo, Hyunmin Kim, Takashi Nakamura
    Abstract:

    The process of Apatite Formation on the surface of Na2O–SiO2 glass in a body environment was investigated, mainly by X-ray photoelectron spectroscopy, as a function of soaking time in a simulated body fluid (SBF). The glass was found to release Na+ ions via exchange with H3O+ ions in the SBF to form Si—OH groups on its surface. These Si—OH groups induced Apatite Formation indirectly, by forming calcium silicate and amorphous calcium phosphate. The Formation of the calcium silicate and amorphous calcium phosphate is attributed to electrostatic interactions between the Si—OH groups on the glass surface and the calcium and phosphate ions in the SBF.

  • tem edx study of mechanism of bonelike Apatite Formation on bioactive titanium metal in simulated body fluid
    Journal of Biomedical Materials Research, 2001
    Co-Authors: Hiroaki Takadama, Tadashi Kokubo, Hyunmin Kim, Takashi Nakamura
    Abstract:

    Bioactive titanium metal, which forms a bonelike Apatite layer on its surface in the body and bonds to the bone through the Apatite layer, can be prepared by NaOH and heat treatments to form an amorphous sodium titanate layer on the metal. In the present study, the mechanism of Apatite Formation on the bioactive titanium metal has been investigated in vitro. The metal surface was examined using transmission electron microscopy and energy dispersive X-ray spectrometry as a function of the soaking time in a simulated body fluid (SBF) and complemented with atomic emission spectroscopy analysis of the fluid. It was found that, immediately after immersion in the SBF, the metal exchanged Na+ ions from the surface sodium titanate with H3O+ ions in the fluid to form Ti-OH groups on its surface. The Ti-OH groups, immediately after they were formed, incorporated the calcium ions in the fluid to form an amorphous calcium titanate. After a long soaking time, the amorphous calcium titanate incorporated the phosphate ions in the fluid to form an amorphous calcium phosphate with a low Ca/P atomic ratio of 1.40. The amorphous calcium phosphate thereafter converted into bonelike crystalline Apatite with a Ca/P ratio of 1.65, which is equal to the value of bone mineral. The initial Formation of the amorphous calcium titanate is proposed to be a consequence of the electrostatic interaction of negatively charged units of titania, which are dissociated from the Ti-OH groups, with the positively charged calcium ions in the fluid. The amorphous calcium titanate is speculated to gain a positive charge and to interact with the negatively charged phosphate ions in the fluid to form the amorphous calcium phosphate, which eventually stabilizes into bonelike crystalline Apatite. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res 57: 441–448, 2001

  • xps study of the process of Apatite Formation on bioactive ti 6al 4v alloy in simulated body fluid
    Science and Technology of Advanced Materials, 2001
    Co-Authors: Hiroaki Takadama, Tadashi Kokubo, Hyunmin Kim, Takashi Nakamura
    Abstract:

    Bioactive Ti–6Al–4V alloy, which spontaneously forms a bonelike Apatite layer on its surface in the body and bonds to living bone through this Apatite layer, can be prepared by producing an amorphous sodium titanate on its surface by NaOH and heat treatments. In this study, the process of Apatite Formation on the bioactive Ti–6Al–4V alloy was investigated in vitro, by analyzing its surface with X-ray photoelectron spectroscopy as a function of soaking time in a simulated body fluid (SBF). Thin-film X-ray diffractometry of the alloy surface and atomic emission spectroscopy of the fluid were also performed complementarily. It was found that immediately after immersion in the SBF, the alloy exchanged Na+ ions from the surface sodium titanate with H3O+ ions in the fluid to form Ti-OH groups on its surface. The Ti-OH groups, immediately after their Formation, incorporated the calcium ions in the fluid to form calcium titanate. The calcium titanate thereafter incorporated the phosphate ions in the fluid to form an amorphous calcium phosphate, which was later crystallized into bonelike Apatite. This process of Apatite Formation on the alloy was the same as on the pure titanium metal, because the alloy formed the sodium titanate free of Al and V by the NaOH and heat treatments. The initial Formation of the calcium titanate is proposed to be a consequence of the electrostatic interaction of negatively charged units of titania dissociated from the Ti-OH groups with the positively charged calcium ions in the fluid. The calcium titanate is postulated to gain a positive charge and interact with the negatively charged phosphate ions in the fluid to form amorphous calcium phosphate, which eventually stabilizes into crystalline Apatite.

Delia S Brauer - One of the best experts on this subject based on the ideXlab platform.

  • Apatite Formation of bioactive glasses is enhanced by low additions of fluoride but delayed in the presence of serum proteins
    Materials Letters, 2015
    Co-Authors: Furqan A Shah, Robert G Hill, Delia S Brauer, Karin A Hing
    Abstract:

    Abstract Five bioactive glass compositions in the SiO 2 –P 2 O 5 –CaO–Na 2 O–CaF 2 system (0–32 mol% CaF 2 ) and Bioglass ® 45S5 were evaluated for their Apatite forming ability in serum-free and serum-containing cell culture media for up to seven days. While F − ions in low concentrations were found to enhance Apatite Formation, higher fluoride content caused Formation of fluorite and calcite. The presence of serum proteins delayed Apatite precipitation for all compositions, while Bioglass ® 45S5, despite considerably higher phosphate content (2.6 vs. ≤1.1 mol% P 2 O 5 ) and high concentrations of Ca 2+ and PO 4 3− in solution, formed only amorphous calcium phosphate.

  • influence of dissolution medium ph on ion release and Apatite Formation of bioglass 45s5
    Materials Letters, 2015
    Co-Authors: Liane Bingel, Daniel Groh, Natalia Karpukhina, Delia S Brauer
    Abstract:

    Abstract Bioactive glasses, particularly Bioglass® 45S5, have been used to clinically regenerate human bone since the mid-1980׳s, owing to their ability to degrade in physiological solutions, release ions and form an Apatite surface layer, which cells adhere to and proliferate on. Although low pH conditions do occur in the human body, e.g. during bacterial infections, in vitro dissolution experiments are usually performed at a physiological pH of 7.3 exclusively. Here, we investigated the dissolution behaviour of 45S5 at low pH (5) and high pH (9) in addition to pH 7.3. The results show that ion release occurs significantly faster at low pH, resulting in significantly faster Apatite Formation (3 h vs. 6 h at pH 7.3). By contrast, at pH 9 low ion exchange rates were observed, resulting in no significant Apatite Formation during the time period studied. Results suggest that low pH caused by bacterial infection is unlikely to inhibit Apatite Formation and, thus, bioactive glass clinical performance.

  • bioactivity of sodium free fluoride containing glasses and glass ceramics
    Materials, 2014
    Co-Authors: Xiaojing Chen, Robert G Hill, Delia S Brauer, Xiaohui Chen, Rory M Wilson, Natalia Karpukhina
    Abstract:

    The bioactivity of a series of fluoride-containing sodium-free calcium and strontium phosphosilicate glasses has been tested in vitro. Glasses with high fluoride content were partially crystallised to Apatite and other fluoride-containing phases. The bioactivity study was carried out in Tris and SBF buffers, and Apatite Formation was monitored by XRD, FTIR and solid state NMR. Ion release in solutions has been measured using ICP-OES and fluoride-ion selective electrode. The results show that glasses with low amounts of fluoride that were initially amorphous degraded rapidly in Tris buffer and formed Apatite as early as 3 h after immersion. The Apatite was identified as fluorApatite by 19F MAS-NMR after 6 h of immersion. Glass degradation and Apatite Formation was significantly slower in SBF solution compared to Tris. On immersion of the partially crystallised glasses, the fraction of Apatite increased at 3 h compared to the amount of Apatite prior to the treatment. Thus, partial crystallisation of the glasses has not affected bioactivity significantly. Fast dissolution of the amorphous phase was also indicated. There was no difference in kinetics between Tris and SBF studies when the glass was partially crystallised to Apatite before immersion. Two different mechanisms of Apatite Formation for amorphous or partially crystallised glasses are discussed.

  • influence of strontium for calcium substitution in bioactive glasses on degradation ion release and Apatite Formation
    Journal of the Royal Society Interface, 2012
    Co-Authors: Yann C Fredholm, Delia S Brauer, Natalia Karpukhina, Julian R Jones, Robert V Law, Robert G Hill
    Abstract:

    Bioactive glasses are able to bond to bone through the Formation of hydroxy-carbonate Apatite in body fluids while strontium (Sr)-releasing bioactive glasses are of interest for patients suffering from osteoporosis, as Sr was shown to increase bone Formation both in vitro and in vivo. A melt-derived glass series (SiO(2)-P(2)O(5)-CaO-Na(2)O) with 0-100% of calcium (Ca) replaced by Sr on a molar base was prepared. pH change, ion release and Apatite Formation during immersion of glass powder in simulated body fluid and Tris buffer at 37°C over up to 8 h were investigated and showed that substituting Sr for Ca increased glass dissolution and ion release, an effect owing to an expansion of the glass network caused by the larger ionic radius of Sr ions compared with Ca. Sr release increased linearly with Sr substitution, and Apatite Formation was enhanced significantly in the fully Sr-substituted glass, which allowed for enhanced osteoblast attachment as well as proliferation and control of osteoblast and osteoclast activity as shown previously. Studying the composition-structure-property relationship in bioactive glasses enables us to successfully design next-generation biomaterials that combine the bone regenerative properties of bioactive glasses with the release of therapeutically active Sr ions.

  • high phosphate content significantly increases Apatite Formation of fluoride containing bioactive glasses
    Acta Biomaterialia, 2011
    Co-Authors: Mohammed Mneimne, Robert G Hill, A J Bushby, Delia S Brauer
    Abstract:

    Bioactive glass-containing toothpastes for treating dentine hypersensitivity work by precipitating hydroxycarbonate Apatite (HCA) onto the tooth surface, but concerns exist over the long-term durability of HCA in the mouth. Fluoride-containing bioactive glasses form fluorApatite (FAp) in physiological solutions, which is more chemically stable against acid attack. The influence of phosphate content on Apatite Formation was investigated by producing a low-phosphate (about 1 mol% P(2)O(5)) and a high-phosphate (about 6 mol%) series of melt-derived bioactive glasses in the system SiO(2)P(2)O(5)CaONa(2)O; increasing amounts of CaF(2) were added by keeping the ratio of all other components constant. pH change, ion release and Apatite Formation during immersion in Tris buffer at 37°C over up to 7 days were investigated. Crystal phases formed in Tris buffer were characterized using infrared spectroscopy, X-ray diffraction and solid-state nuclear magnetic resonance (NMR) spectroscopy. An increase in phosphate or fluoride content allowed for Apatite Formation at lower pH; fluoride enhanced Apatite Formation due to lower solubility of FAp compared to hydroxyApatite or HCA. High phosphate content glasses formed Apatite significantly faster (within 6h) than low phosphate content glasses (within 3 days). In addition, an increase in phosphate content favoured Apatite Formation rather than fluorite (CaF(2)). (19)F magic angle spinning NMR showed the Apatite formed by fluoride-containing glasses to be FAp, which makes these glasses of particular interest for dental applications. This study shows that by varying the phosphate content, the reactivity and Apatite Formation of bioactive glasses can be controlled successfully.