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It is well known that minerals of bone or tooth are essentially of CaO-P2O5 system. Glass and the crystallized product, i.e., so-called "glass-ceramics" of which chemical composition is 55 CaO . 45 P2O5 (in mole %) and have been developed for biomaterials were subjected to chemical durability test. Human enamel was also tested for the comparison of the data with them. All the specimens were ground to powders in size from 74 to 140 micrometer. A hundred milligram of the powders were immersed into 100 ml. of N/10 acetate buffer (1 mol acetic acid) solution (pH 4.1) at a constant temperature of 37 degrees C. Amount of Ca2+ and P5+ dissolved were determined by an atomic absorption method and Fiske-Subbarow method, respectively. The order of dissolution is human enamel greater than glass greater than glass-ceramics: the amount of Ca2+ (SCa) and P5+ (Sp) with soaking time (t) was expressed by the following equations, :formula: (see book). The glass and the glass-ceramics show good resistance against a weak acid.
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PMID:[Studies of calcium phosphate glass-ceramics--development of dental materials. (Part 2) Acid resistance--(author's transl)]. 28 65

Crystallization kinetics studies for six experimental glass formulations in the system Na2O-CaO-SiO2-P2O5 synthesized by wet chemistry were conducted by means of differential thermal analysis. These glasses had CaO/P2O5 and SiO2/ (CaO + Na2O) ratios ranging from 8.74-3.38 and 0.92-3.03, respectively. Samples of each glass (n = 30 were heated from 23 to 1250 degrees C under N2 atmosphere at heating rates ranging from 10 to 50 degrees C/min. Glass-ceramics were obtained after heat treating the initial glasses at temperatures determined from their DTA exotherms. The activation energy of crystallization for each glass composition was calculated from an expression-relating log-heating rate and the reciprocal of the exothermic peak temperature. The compositions of the six glasses were significantly different (p = 0.05). The activation energy of crystallization (Q) values ranged from 196 to 782 kJ/mole. A correlation was obtained between Q and CaO/P2O5 and between Q and the Young's modulus (P < 0.001). Two of the six glasses exhibited bulk crystallization. X-ray diffraction studies showed that four of the six glasses exhibited different proportions of crystalline phases following heat treatment. These phases were wollastonite (CaSiO3), Na2CaSi3O9, combeite [Na4Ca3SI6O16(OH)2], and some unidentifiable phases. Two of the six bioceramic materials had a mixture of unknown crystalline phases.
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PMID:Crystallization of experimental bioactive glass compositions. 886 80

A glass with a composition (in mole %) of: SiO2 (70), CaO (26), and P2O5 (4) was obtained using a sol-gel method. The in vitro bioactivity of the glass was assessed by determining the changes in surface morphology and composition after soaking in simulated body fluid (SBF) for periods of up to 14 days at 37 degrees C. X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, and FTIR analyses of the glass surface after different soaking periods in SBF demonstrated the growth of an apatite-like layer on the glass surface. In the first stage, an amorphous calcium phosphate layer was formed; after 7 days this surface consisted of spheres, with diameters ranging between 2 and 15 microm, composed of needle-like apatite crystallites (250 x 100 nm) with a crystallinity similar to that of a biological apatite.
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PMID:XRD, SEM-EDS, and FTIR studies of in vitro growth of an apatite-like layer on sol-gel glasses. 1039 45

Hydroxyapatite (HA) and other calcium phosphates were synthesized on titanium plates by a solid-gas state reaction of sputtered CaO and vaporized P(2)O(5). The calcium phosphates formed were HA, beta-tricalcium phosphate (beta-TCP; Ca(3)(PO(4))(2)), beta-calcium pyrophosphate (beta-PYR; Ca(2)P(2)O(7)), and beta-calcium metaphosphate (beta-MET; Ca(2)(PO(3))(2)). Their formation depended on the ratio of the sputtered CaO and the reacting P(2)O(5). For a mole ratio of CaO/P(2)O(5)=4 (Ca/P=2), an HA film was synthesized. The surface roughness increased by over seven times after the solid-gas state reaction from Ra = 0.16+/-0.02 microm (for the CaO film) to Ra = 1.15+/-0.25 microm (for the reacted film). The synthesized HA film-coated titanium plates and control non-coated titanium plates were implanted in the femora of two dogs for a period of two, four and 12 weeks, and observed using a soft X-ray radiograph and histological sections. New bone formation was observed without any connective tissue at four weeks around the HA film, whereas over the 12 week experimental period, there was no new bone formation around the control and connective tissue was observed over all periods, reaching a thickness of more than 200 microm at 12 weeks.
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PMID:Preparation and osteocompatibility of hydroxyapatite coated on titanium from the reaction of sputtered CaO and vaporized P2O5. 1265 25

The in vitro biocompatibility of a group of ionomeric cements (ICs) was evaluated with respect to their ion release properties. These ICs were made from a defined series of glasses with the general formula 1.5SiO2.0.5P2O5.Al2O3.(1.0-Z)CaO.0.75CaF2 where Z was the mole fraction (ranging from 0-0.1) of an alkali metal oxide, either sodium or potassium or a mixture of both. For these alkali metal ICs, the amount of sodium released was directly related to the sodium content of the constituent glass. Similarly, the amount of potassium released was directly related to the potassium content. There was no correlation between the aluminum content of the glass and the aluminum ion release. Increasing the monovalent cation concentration, however, produced ICs with increased fluoride release. The biocompatibility of the ICs, as assessed by in vitro cell growth and viability measurements, was inversely proportional to aluminum ion release. Fluoride ion release, although important in terms of in vitro biocompatibility, would appear to be less important than aluminum ion release in determining the overall biocompatibility of the ICs studied.
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PMID:Dependence of in vitro biocompatibility of ionomeric cements on ion release. 1534 32

Bioactive materials are routinely used in dental and orthopaedic applications. The concept was first introduced in 1971, with the discovery of 45S5 Bioglass, which is known to develop an interfacial bond between the implant and the host tissue. This glass is composed of SiO(2), CaO, P(2)O(5) and Na(2)O. Since then numerous glasses and glass ceramics with similar compositions have been extensively studied for clinical applications. Until 1990 it was accepted that P(2)O(5) and Na(2)O were necessary components for the glass composition to be bioactive. However, calcium silicate glasses with high SiO(2) content are impossible to produce using the traditional melt-quench method. This is due to the liquid-liquid immiscibility region that is present between 0.02 and 0.3 mole fraction of CaO and in terms of bioactivity, high CaO compositions were inferior to those quaternary bioactive glass compositions already in existence. In the last few years several studies have been reported regarding the production of CaO-SiO(2) glasses via the sol-gel processing technique. This report summarises the findings of the past and the present and also outlines potential of these calcium silicate gel-glasses in the field of biomaterials.
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PMID:Binary CaO-SiO(2) gel-glasses for biomedical applications. 1547 95

In this study, 80% SiO(2)-20% CaO (mole fraction) three-dimensionally ordered macroporous sol-gel bioactive glass (3DOM-BG, average pore size: 345 nm) particles were prepared and characterized. Since the 3DOM-BGs have a novel microstructure and ion-releasing profile, the cytotoxicity of 3DOM-BG particles was tested. The cytotoxicity tests were performed using MC3T3-E1 osteoblast-like cells: (1) Wst-1 assay for cell viability after culture in extracts from 3DOM-BG particles; (2) phase contrast microscopy for cell morphology after culture with 3DOM-BG particles; and (3) fluorescence microscopy for imaging cells cultured directly on 3DOM-BG particles. The results showed that 3DOM-BG particles were not cytotoxic, and that cells attached, spread and proliferated on and around 3DOM-BG particles.
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PMID:Cytotoxicity of three-dimensionally ordered macroporous sol-gel bioactive glass (3DOM-BG). 1572 22

Seven nominally identical samples of Na-free carbonate apatite (CO(3)Ap) were prepared by reaction of CaHPO(4) with ammonium carbonate solution at 70 degrees C over 3 days. They were studied by chemical analysis, Rietveld analysis of powder X-ray diffraction (XRD) data, Ca/P ratio determinations (quantitative phase analysis of CaO, Ca(OH)(2) and hydroxyapatite formed after heating to 900 degrees C from Rietveld analysis of XRD data), He pycknometry, (1)H, (13)C and (31)P MAS NMR spectrometry and Fourier transform infrared and Raman spectroscopy. Spectroscopy showed the apatite products were B-type CO(3)Aps (CO(3)(2-) replacing PO(4)(3-)) and XRD that one sample contained 1.6 wt% calcite with a trace in another. Mean results of the six essentially calcite-free samples were: a=9.405(5)A, c=6.896(2)A; 11.2 wt% CO(3); unit cell contents, Ca(8.241)(PO(4))(4.344)(CO(3))(1.656)(OH)(0.139) x 2.29H(2)O; mole Ca/P ratio from chemical analyses, 1.897(22) and from powder XRD phase analysis of samples decarbonated at 900 degrees C, 1.892(25). Density determinations indicated that the 2.29mol of H(2)O were in the unit cell. Rietveld refinements were undertaken without and with explicit modelling of the CO(3)(2-) ion. The latter used constraints to maintain the CO(3)(2-) ion in its known geometry and the total of PO(4)(3-) and CO(3)(2-) ions per unit cell at six. Without the CO(3)(2-) ion in the model, PO(4) volume, P-O bond lengths and P occupancy were apparently reduced, consistent with CO(3)(2-) replacing PO(4)(3-) ions. With the CO(3)(2-) ion modelled, the reductions were less and the CO(3)(2-) ion occupied the "sloping" face of the replaced PO(4)(3-) ion in two-fold disorder about the mirror plane. The angle between the normal to the plane of the ion and the c-axis was 34 degrees , close to 35.3 degrees , the equivalent angle for the PO(4)(3-) ion. When modelled, the CO(3)(2-) ion occupancy was 1.81 ions per unit cell, in reasonable agreement with unit cell contents determined chemically (1.66). The OH(-) ion occupancy was elevated (2.33 ions per unit cell versus 0.14 inferred from the charge balance), which we ascribe to H(2)O molecules occupying sites in c-axis channels. The Ca/P ratio from occupancies (2.31) was also elevated over that determined chemically (1.90). We attribute this to loss of Ca from Ca sites increasing the apparent anisotropic displacement parameters of remaining Ca atoms, leading to an apparently increased occupancy.
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PMID:Rietveld refinements and spectroscopic structural studies of a Na-free carbonate apatite made by hydrolysis of monetite. 1675 Aug 50

Poly(tetramethylene oxide) (PTMO)-CaO-Ta2O5 hybrids were prepared by hydrolysis and polycondensation of triethoxysilane-functionalized PTMO (Si-PTMO), tantalum ethoxide (Ta(OEt)5) and CaCl2. In the system CaO-free PTMO-Ta2O5, Si-PTMO/Ta(OEt)5 weight ratios were 30/70, 40/60 and 50/50 (hybrids PT30Ca0, PT40Ca0 and PT50Ca0, respectively). In the system PTMO-CaO-Ta2O5, the Si-PTMO/Ta(OEt)5 weight ratio was 40/60 and CaCl2/Ta(OEt)5 mole ratios were 0.05, 0.10 and 0.15 (hybrids PT40Ca5, PT40Ca10 and PT40Ca15, respectively). Crack-free transparent monolithic hybrids were obtained for all the examined compositions except for PT30Ca0. Even CaO-free hybrids PT40Ca0 and PT50Ca0 formed apatite on their surfaces in a simulated body fluid (SBF) within 14 days. Hybrid PT40Ca0 showed higher mechanical strength, which was increased by soaking in SBF, and larger strain to failure than human cancellous bone. The CaO-containing hybrids showed higher apatite-forming ability than the CaO-free hybrids, and its apatite-forming ability increased with increasing CaO content. Hybrids PT40Ca10 and PT40Ca15 formed apatite within 3 days. The mechanical strength of PT40Ca15 was, however, lower than PT40Ca0 and was decreased by soaking in SBF. Thus obtained flexible bioactive CaO-free PTMO-Ta2O5 hybrids are expected to be useful as bone substitutes.
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PMID:Preparation of bioactive flexible poly(tetramethylene oxide) (PTMO)-CaO-Ta2O5 hybrids. 1726 65

Primary deep infection following joint replacement surgery accounts for 7% of all revisions. Glass polyalkenoate cements (GPCs) have previously been shown to exhibit antibacterial properties. The present study had two objectives. The first was to determine if addition of tri-sodium citrate (TSC) to the powder phase of an Al-free GPC (0.04 SrO-0.12 CaO-0.36 ZnO-0.48 SiO2, by mole fraction) enhanced the resultant cement's antibacterial properties against three strains of bacteria that are commonly found in periprosthetic sites following total joint replacements (TJRs); namely, E. coli, B. fragilis, and S. epidermidis. Four cement sets were prepared, which contained 0 wt% TSC (control), 5 wt% TSC, 10 wt% TSC, and 15 wt% TSC. All the TSC-modified cements were found to exhibit large inhibition zones against all the bacterial strains, especially the cement containing 15 wt% TSC against E. coli. The antibacterial properties of the TSC containing GPCs are attributed to the release of Zn and Na ions from the cements and the presence of the TSC. The second objective was to investigate if, when a modified GPC is embedded in a bovine bone model, ionic transfer occurs. It was found that Zn ions migrated from the cement to the surrounding bone, particularly at the cement-bone interface. This is a desirable outcome as Zn ions are known to play a vital role in both bone metabolism and the regeneration of healthy bone. The present results point to the potential clinical benefits of using TSC-modified GPCs in TJRs.
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PMID:Antibacterial properties of a tri-sodium citrate modified glass polyalkenoate cement. 1921 53


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