Calcium Phosphate Glass Ceramics Research Articles

Dissolution of Nb-doped hydroxyapatite prepared via low-temperature mechanochemical method: Spectroscopy studies

Calcium phosphate glass ceramics with nominal hydroxyapatite stoichiometry doped with niobium were synthesized using simple as well as low-temperature mechanochemical method and then in the form of compressed pellet were submitted to the static dissolution process in distilled water for one month. The results of structural analysis, performed mainly on the base of spectroscopic methods such as: infrared absorption spectroscopy, energy-dispersive X-ray spectroscopy, photoelectron spectroscopy as well as soft and tender X-ray absorption spectroscopies, indicate that during the dissolution process the presence of niobium reduced the dynamics of the calcium phosphate new layer formation, without a significant impact on the morphology and stoichiometry of this layer. Moreover, the Nb addition favored the formation of hydroxyapatite and Ca-deficient hydroxyapatite, both during the synthesis and dissolution processes, and facilitated the incorporation of the CO3-2 groups into the ceramic matrix, leading to the formation of B-type carbonated apatite.

Early clinical and radiographic outcomes of trabecular metal total ankle using transfibular approach

Musculoskeletal conditions are the most commonly occurring medical conditions, and they have a considerable influence on the quality of health and living standard of the millions of people across the world. Annually, around the globe, approximately 2.3 million bone-tissue graft transplants are performed. The bone fracture, osteoporosis, osteoarthritis, and various neoplastic disorders are the common clinical problems related with bone and skeletal system. The common approaches to these bone problems are autografts or allografts. These protocols have certain limitations such as resorption, donor site morbidity, compromised supply, rejection rate up to 50% at some sites, and the risk of inducing transmissible diseases. Consequently, considerable attention has been directed toward the use of bioactive materials as synthetic grafts for bone regeneration. These include hydroxyapatite (HAP), tricalcium phosphate, bioactive glass, and glass ceramics. More significantly, calcium phosphates are the major constituent of bone mineral. The most extensively used synthetic calcium phosphate ceramic for bone replacement is HAP with a chemical formula of Ca10(PO4)6(OH)2. It has Ca:P molar ratio of 1.667 and is regarded as the most stable composition compared to other calcium phosphate ceramic within a pH range of 4.2–8.0. Calcium phosphate cement is one of the most important types of bioceramic material. In combination with various calcium phosphates, an injectable paste can be formed, which is cured over a period of time, in which resultant product is a carbonate apatite. The cements cure in situ and are gradually resorbed and replaced by a newly formed bone. The concept of a bioactive glass was pioneered by Hench and colleagues. The composition of Bioglass is a series of special designed glasses, consisting of a Na2O–CaO–SiO2 glass with the addition of P2O5, B2O3, and CaF2. A biologically active hydroxycarbonate apatite layer is formed on the surface of bioactive glasses in vitro and in vivo. The chemical properties could be controlled in bioactive glasses and eventually its bonding to tissue. Certain specialized compositions of Bioglass (e.g., 45S5) can bond to soft tissue as well as bone, in either bulk or particulate form. Moreover, apatite-wollastonite glass-ceramic, with an assembly of small apatite particles effectively reinforced by β-wollastonite exhibit not only bioactivity, but also a fairly high mechanical strength. Mechanical properties like the bending strength, toughness against fracture, and Young’s modulus of A-W glass-ceramic are the highest among bioactive glasses and glass-ceramics enabling it to be used in some compression load-bearing applications. Overall, the advantages of bioactive glasses are the magnitude of their surface reactivity and the ability to change the chemical composition, thus facilitating bonding with variety of tissues. Mechanical properties are the drawback as these materials have relatively low bending strength in comparison to other ceramic materials. The bioactive calcium phosphate ceramics, bioglasses, and glass-ceramics form a mechanically strong interfacial bond with bone. The strength of the bond is normally equivalent to or greater than the strength of the host bone, depending on test conditions. Therefore, all of these materials have excellent bioactivity. Nevertheless, bioactive ceramics have a flexural strength, strain-to-failure, and fracture toughness, which is less than the bone and the elastic modulus is greater than the bone. In other words, most bioactive materials have a less-than-optimal biomechanical compatibility when used in load-bearing applications. An approach to mitigate this problem involves designing and structural tailoring of bioactive composites. The concept of matching the mechanical behavior of an implant, with the tissue to be replaced in order to solve the problem of stress shielding of conventional biomaterials, was proposed by Bonfield et al. Thus, the composite approach can significantly meet the challenge of a long life, as a demand for the new-generation implant materials. Calcium phosphate ceramics, bioglasses, and glass ceramics are generally considered to be bone bioactive ceramics. These materials generally get bonded to the surrounding osseous tissue and enhance further bone-tissue formation. The direct bone bonding to bioactive glasses was first observed and reported by Hench et al., since then considerable progress has been made in understanding the basic mechanism of the formation of bone and biomaterial bond and its effect on bone formation.

The biological properties of the silver- and copper-doped ceramic biomaterial

The biological properties of nanostructured bioactive ceramic composite (BCC) granules doped with 0.1–10 at.% silver and 0.05–5 at.% copper have been investigated both in vitro and in vivo to develop effective alloplastic material for infected bone defect substitute. It is assumed that the granules consisting of biphasic calcium phosphate and bioactive glass ceramics due to their nanoscale (15–40 nm) and multiphase structure, bioelement placement in different ceramic phases as well as antimicrobial effect should improve osteogenic properties and biocompatibility. Tests in vitro have been conducted with multipotent mesenchymal stromal cells (MSCs) and test strains of microorganisms. The same biocomposite has been used in vivo to study the repair of bone defects in animal model. The findings indicate that doped BCC leads to antimicrobial activity. Inhibition of MSCs growth has been observed for granules doped with ions of more than 1 at.% silver and 0.5 at.% copper. The results of the in vivo study reveal that BCC implantation significantly improves bone reparation. Differences between bone repair with undoped and doped, with 1 at.% silver and 0.5 at.% copper, ceramic samples were not observed. The BCC doped within 0.5–1 at.% silver and 0.25–0.5 at.% copper stimulates bone tissue repair and has satisfactory biocompatibility and antimicrobial properties.

KrF excimer laser precision machining of hard and brittle ceramic biomaterials

KrF excimer laser precision machining of porous hard–brittle ceramic biomaterials was studied to find a suitable way of machining the materials into various desired shapes and sizes without distorting their intrinsic structure and porosity. Calcium phosphate glass ceramics (CPGs) and hydroxyapatite (HA) were chosen for the study. It was found that KrF excimer laser can cut both CPGs and HA with high efficiency and precision. The ablation rates of CPGs and HA are respectively 0.081 µm/(pulse ⋅ J cm−2) and 0.048 µm/(pulse ⋅ J cm−2), while their threshold fluences are individually 0.72 and 1.5 J cm−2. The cutting quality (smoothness of the cut surface) is a function of laser repetition rate and cutting speed. The higher the repetition rate and lower the cutting speed, the better the cutting quality. A comparison between the cross sections of CPGs and HA cut using the excimer laser and using a conventional diamond cutting blade indicates that those cut by the excimer laser could retain their intrinsic porosity and geometry without distortion. In contrast, those cut by conventional machining had distorted geometry and most of their surface porosities were lost. Therefore, when cutting hard–brittle ceramic biomaterials to prepare scaffold and implant or when sectioning them for porosity evaluation, it is better to choose KrF excimer laser machining.

Porous hydroxyapatite scaffolds containing calcium phosphate glass-ceramics processed using a freeze/gel-casting technique

A freeze/gel-casting technique has been applied to produce porous ceramic composite scaffolds with tailored pore structures and improved compressive strength for tissue engineering applications. Tertiary-butyl alcohol (TBA)-based hydroxyapatite/calcium phosphate glass-ceramic suspensions with 5–15 vol.% solid loading were used in this study. Following sintering at 1050–1250 °C, the composite scaffolds were characterized in terms of microstructure, and physical and mechanical properties. The resulting scaffolds consisted of unidirectional pore channels (macro-sized) aligned in the solidification direction of the TBA solvent used in the freeze casting step and a few inter/intra-granular pores with small diameter (micron sized) remained in the wall structures of the pore channels by gel casting. With the addition of glass-ceramics (≤10 wt%), a liquid phase was formed mainly by the melting of calcium phosphate glasses at a given sintering temperature. The wall structures became more densified (less porous) aided by liquid phase sintering, possibly lending enhanced compressive strength.

In vitro solubility and bioactivity of Sr and Mg co-doped calcium phosphate glass-ceramics derived from different heat-treatment temperatures

CaO–P 2O 5–Na 2O–SrO–MgO glass–ceramic system was prepared by controlled heat treatment process. Solubility and bioactivity of glass-ceramics were measured and evaluated in simulated body fluid (SBF) and cell culture medium respectively. The dissolution behavior of these glass-ceramics strongly depends on the amount and microstructure of the crystals precipitated by sintering treatment. Concerning the bioactivity, the onset of the apatite formation on the glass–ceramic system was directly dependent on the amount of bioactive glass amount which can be controlled using different temperatures of heat treatment. After immersing glass–ceramic in SBF, Mg ion as one of system composition can be released from residual glass and provides a high impact on the Ca/P ratio and chemical stability of the deposited apatite layer that directly affects cell attachment and proliferation in in vitro cell culture system. The glass ceramics heat-treated at 760 °C and 780 °C show less glass amount, and their degradation rates are both compatible with cell growth and differentiation.

Effect of ZrO<sub>2</sub> on Mechanical and Biological Properties of Calcium Phosphate-Based Glass-Ceramics for Biomedical Applications

The effect of ZrO2 addition on mechanical and biological properties of bioactive glass-ceramics with chemical compositions of 60CaO-30P2O5-3TiO2-xZrO2-(7-x)Na2O (x=0,1,3) was investigated. It was found that ZrO2 addition up to 3 mol% contributes to monotonical increase of the glass transition temperature. The micro-hardness increases slightly by 1 mol% ZrO2 addition and keeps constant with further addition whereas 1 mol% ZrO2 addition results in ~20% increase of three-point bending strength. When the specimens were soaked in simulated body fluid, complete apatite layers were formed on the specimens regardless of the ZrO2 addition. It is therefore concluded that the toughening contribution of 1 mol% ZrO2 addition has no adverse effect on the bioactivity of calcium phosphate glass-ceramics.

Preparation of Apatite-Containing Calcium Phosphate Glass-Ceramics

A new type of glass-ceramic for novel dental fillers, which require excellent chemical durability, was investigated. A 40CaO-5CaF2-25TiO2-30P2O5 (in mol%) glass-ceramic was newly suggested. The glass-ceramic was prepared by a conventional two-step heating method. The resulting glass-ceramic included Nasicontype-CaTi4(PO4)6, titanium phosphates, such as (TiO)2P2O7 and Ti(PO3)3, and TiO2 (anatase) with apatite crystal, which was induced by incorporation of fluorine. In the glass-ceramic, dissolution by acid-treatment was strictly controlled. The excellent chemical durability of the glass-ceramic was suggested to originate from increase in the amount of the crystalline phases and a high content of titanium constituent in the residual glassy phase.

The effects on the devitrification mechanism for a certain composition of CaO/P2O5 glasswith additives of HAp, TCP and β-CaP2O6 whisker

In previous works, the effects on the devitrification mechanism of a certain composition calcium phosphate with additives of TiO2, SiO2, Al2O3, CeO2 have been studied. It was found that some metal oxide additives played a key role as the nucleation agent in calcium phosphate glass-ceramics, and the devitrification mechanism of calcium phosphate glass system was changed drastically by addition such as metal oxide. Hydroxyapatite (HAp), tricalcium phosphate (TCP) and β-calcium phosphate (β-CaP2O6) whisker are the three most biologically compatible materials to human bone in bio-ceramics field. In this work, the effect on devitrification mechanism and the physical properties of certain composition calcium phosphate glass with three above additives were investigated, and the result shown that although no fine crystalline was induced in the certain composition of calcium phosphate glass when a large amount of additive was added, but such additives play a catalyst role by lowering the activation energies of devitrification. It would supplement the mechanical properties and the biocompatibility for the calcium phosphate glasses.

On the feasibility of phosphate glass and hydroxyapatite engineered coating on titanium

In this report, bioactive calcium phosphate (CaP) coatings were produced on titanium (Ti) by using phosphate-based glass (P-glass) and hydroxyapatite (HA), and their feasibility for hard tissue applications was addressed in vitro. P-glass and HA composite slurries were coated on Ti under mild heat treatment conditions to form a porous thick layer, and then the micropores were filled in with an HA sol-gel precursor to produce a dense layer. The resultant coating product was composed of HA and calcium phosphate glass ceramics, such as tricalcium phosphate (TCP) and calcium pyrophosphate (CPP). The coating layer had a thickness of approximately 30-40 microm and adhered to the Ti substrate tightly. The adhesion strength of the coating layer on Ti was as high as 30-33 MPa. The human osteoblastic cells cultured on the coatings produced by the combined method attached and proliferated favorably. Moreover, the cells on the coatings expressed significantly higher alkaline phosphatase activity than those on pure Ti, suggesting the stimulation of the osteoblastic activity on the coatings. On the basis of these observations, the engineered CaP coating layer is considered to be potentially applicable as a hard tissue-coating system on Ti-based implants.

In vitro studies of calcium phosphate glass ceramics with different solubility with the use of human bone marrow cells

Two glass ceramics in the CaO--P2O5--MgO system with the incorporation of K2O or TiO2 oxides were prepared with the goal of using them as potential bone graft substitutes. The incorporation of TiO2 and K2O led to the preparation of specific crystalline phases in the structure of the glass ceramics, which show different degrees of biodegradation. In fact, the 45CaO--45P2O5--5MgO--5K2O has been previously demonstrated to be much more soluble in aqueous solutions than the 45CaO--37P2O5--5MgO--13TiO2 glass ceramic. The in vitro biological activity of the two calcium phosphate glass ceramics was studied with the use of human bone marrow osteoblast cell cultures maintained for 28 days, and seeded materials were assessed for cell proliferation and function. The Ti-containing glass ceramic showed a stable surface throughout the culture time, on macroscopic and SEM observation. Osteoblast cells proliferated gradually, especially during the third week, with a high alkaline phosphatase activity and formation of a mineralized matrix. On SEM observation, attached cells appeared with a spread-polygonal morphology typical of the osteoblast cells, with extensive cell-to-cell contact. Cell behavior on the seeded material was similar to that found on cultures performed on tissue-culture-grade polystyrene; except for the presence of lower cell numbers during the first 2 weeks. By contrast, the K-containing glass ceramic showed a highly instable surface with dissolution/precipitation processes occurring throughout the culture time. Few cells adhered to the material surface, and subsequent proliferation was also hindered, especially from the first week onwards. Cell numbers were significantly lower than those observed in the Ti-containing glass ceramic during most of the incubation time. Results suggest that the different in vitro biological behavior of these two glass ceramics is mainly due to the significant differences in the surface degradation rate, which is directly correlated to the chemical composition of the mother glass.

Bone Formation of Intrabony Defects in Beagle Dogs Using Calcium Phosphate Glass and Glass-Ceramics

The purpose of this study was to compare the bone regenerative effect of calcium phosphate glass and glass-ceramics in the system of CaO-CaF2-P2O5-MgO-ZnO, which is already reported that promoted the bone-like tissue formation in vitro and formed new bone in Sprague-Dawley rats. We prepared calcium phosphate glass and glass-ceramics with Ca/P ratio of 0.6 using the system CaO-CaF2-P2O5-MgO-ZnO and subsequently milled to 400 µm. 4×4 mm 1-wall intrabony defects of six beagle dogs were surgically created and used in this study. 8 weeks after transplantation of the prepared calcium phosphate glass and glass-ceramics in the experimental group 1 and 2, respectively, the animals were sacrificed. No root resorption or ankylosis were observed in all groups. It can be examined that the prepared glass-ceramics were more effective in alveolar bone regeneration with statistical signigicant difference. In cementum regeneration, both the prepared glass and glass-ceramics showed significantly different effect. However, there were no statistical significant difference neither in glass nor glass-ceramics in the amounts of junctional epithelium migration and connective tissue adhesion. Further study is required to control the flowability as well as reduce the absorption rate in vivo.

In situ thermal and structural characterization of bioactive calcium phosphate glass ceramics containing TiO 2 and MgO oxides: High temperature – XRD studies

This study aims to develop glass ceramics in the calcium phosphate system that exhibit suitable properties to be used for biomedical applications. Calcium phosphate glasses with the incorporation of small additions of MgO and TiO 2 oxides were prepared in the pyro-and orthophosphate regions. The glass ceramics were prepared by a controlled powder sintering process through heat-treatment at different temperatures, as defined by results from differential thermal analysis (DTA). The composition of the crystalline phases precipitated in the glassy matrix as a result of heat treatments at different temperatures, ranging from 681 to 725 °C, was determined from X-ray diffraction data. The sequence of phase crystallization in the mother glass was also studied in situ using high temperature X-ray diffraction (HT-XRD) analysis. Results showed that the first phases that precipitated in the glass matrix were α- and β-Ca 2P 2O 7 at 620 °C. A small amount of CaTi 4(PO 4) 6 appeared at 630 °C. At 650 °C the three phases α-Ca 2P 2O 7, β-Ca 2P 2O 7 and CaTi 4(PO 4) 6 were clearly presented with a small amount of TiP 2O 7 and finally at 660 °C all four phases were observed. Glass ceramics were also characterized using Raman and X-ray photoelectron spectroscopy. This study demonstrates that, by altering the heat treatment cycle, it is possible to prepare glass ceramics in the calcium phosphate system that contains different bioactive and biocompatible phases.

Preparation of macroporous calcium phosphate glass-ceramics

Preparation of macroporous calcium phosphate glass-ceramics

Preparation of Apatite-Containing Calcium Phosphate Glass-Ceramics

Preparation of Apatite-Containing Calcium Phosphate Glass-Ceramics

Apatite-Forming Ability of Calcium Phosphate Glass-Ceramics Improved by Autoclaving

Apatite-Forming Ability of Calcium Phosphate Glass-Ceramics Improved by Autoclaving

In vitro degradation studies of calcium phosphate glass ceramics prepared by controlled crystallization

Calcium phosphate glass ceramics with incorporation of small additions of two nucleating agents, MgO and K 2O were prepared in the metaphosphate and pyrophosphate region, using an appropriate two-step heat treatment of controlled crystallization defined by differential thermal analysis results. Identification and quantification of crystalline phases precipitated from the calcium phosphate glass were performed using X-ray diffraction and Rietveld analysis. The β-Ca 2P 2O 7 (β-DCP), KCa(PO 3) 3, β-Ca(PO 3) 2 and Ca 4P 6O 19 phases were detected in the glass ceramics. In order to evaluate the degradation of the glass ceramics prepared, degradation studies were carried out during 42 days in Tris-HCl solution at 37 °C, pH 7.4, using granules in the range of 355–415 μm. The materials presented a weight loss ranging up to 12%. The ions leached during the immersion mainly originated from the KCa(PO 3) 3 phase, probably due to the presence of K + ion in the calcium metaphosphate, and the residual glassy phase. The structural changes at the surface of materials during degradation have been analyzed by Fourier transform infrared spectroscopy and X-ray diffraction. Results showed that significant surface changes occurred with immersion time, with the decrease of KCa(PO 3) 3, β-Ca 2P 2O 7 and β-Ca(PO 3) 2 phases occurring at different periods of immersion. This study has demonstrated an easy way to prepared calcium phosphate materials with specific calcium phosphate phases and crystallization, and therefore specific degradation rates.

Calcium Phosphate Glass‐Ceramics for Bioactive Coating on a β‐Titanium Alloy

The formation of a porous coating is the decisive feature for the bio‐compatibility of silica‐free calcium phosphate glass ceramics on alloy surfaces like the β‐Ti structured Ti‐29Nb‐13Ta‐4.6Zr used in this work. The ceramic composition is highly important: 50 CaO‐40 P2O5‐7 Na2O‐3 TiO2 glass powder produces a pore‐free coating unable to bind hydroxyapatite, whereas 60 CaO‐30 P2O5‐7 Na2O‐3 TiO2 glass incorporates pores from which a crystalline hydroxyapatite phase can grow over the surface from simulated body fluid (see Figure).

Surface dissolution of calcium phosphate glass ceramics in dilute acid conditions

Abstract Calcium phosphate glass–ceramic materials in the P2O5–CaO–SiO2–K2O system were prepared from mineral and industrial waste raw materials. They were characterized by chemical analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Tricalcium phosphate (α and β-Ca3(PO4)2), tetracalcium phosphate (Ca4P2O9) and glassy phases were identified in various proportions. The materials were treated in water, ammonium citrate, ammonium acetate and citric acid solutions. The mechanism of attack of the different phosphate phases in dilute acid conditions was established mainly following the P, Si, Ca, K concentrations versus time by inductively coupled plasma optical emission spectroscopy (ICP–OES). The results show that these glass–ceramic materials can be used as controlled released fertilisers.

Machinable calcium pyrophosphate glass-ceramics

Glass-ceramics containing a large amount of calcium pyrophosphate (β–Ca2P2O7) crystal were prepared via crystallization and sintering; compacts of a calcium phosphate glass powders with a composition of 60CaO · 30P2O5 · 5TiO2 · 5Na2O (in mol%) were heated for 3–6 h at 850 °C in air. The compacts were densified by the viscous flow of the glassy phases during heating. The calcium phosphate glass-ceramics were found to show a bending strength of approximately 100 MPa, and they were easy to machine, as confirmed by a drilling test using a conventional carbide tool. The machinability is thought to arise from the microstructure consisting predominantly of the interlocking and platelike β–Ca2P2O7 precipitated in the glass.