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Microstructural Characterization of Hydroxyapatite Coating on Titanium
Abstract
The microstructure of hydroxyapatite plasma sprayed onto titanium alloy has been studied by using transmission electron microscopy. It has been shown that while substantial portions of the coating are crystalline hydroxyapatite, regions of amorphous calcium phosphate with Ca/P ratios of 0.6–1.0 are also present, both in the coatings and at the metal-ceramic interface. The microstructures observed have also been found to be consistent with devitrification of the amorphous calcium phosphates producing regions of very fine grained hydroxyapatite. A calcium titanate phase has also been detected at the metal-ceramic interface produced by the chemical reaction of hydroxyapatite to titanium.
... This is a very promising material for biomedical utilization due to its resemblance to human hard tissue [26][27][28]. However, CDH exhibits a low mechanical strength, which limits its use mainly to low load-bearing applications, such as osteoconductive coatings on metallic or other ceramics prosthesis [29][30][31]. Phosphate ceramics exhibit considerably improved biological affinity and activity, but they contain poor crack growth resistance and poor mechanical properties (in terms of their strength and fracture toughness) in comparison to alumina and zirconia ceramics [29][30][31]. The chemical similarity of HAp to the inorganic components of human bones and teeth has led to extensive research in the field of hard tissue engineering [30]. ...
... However, CDH exhibits a low mechanical strength, which limits its use mainly to low load-bearing applications, such as osteoconductive coatings on metallic or other ceramics prosthesis [29][30][31]. Phosphate ceramics exhibit considerably improved biological affinity and activity, but they contain poor crack growth resistance and poor mechanical properties (in terms of their strength and fracture toughness) in comparison to alumina and zirconia ceramics [29][30][31]. The chemical similarity of HAp to the inorganic components of human bones and teeth has led to extensive research in the field of hard tissue engineering [30]. ...
... Phosphate ceramics exhibit considerably improved biological affinity and activity, but they contain poor crack growth resistance and poor mechanical properties (in terms of their strength and fracture toughness) in comparison to alumina and zirconia ceramics [29][30][31]. The chemical similarity of HAp to the inorganic components of human bones and teeth has led to extensive research in the field of hard tissue engineering [30]. According to earlier works, the use of CDH and HAp as cover layers on oxide ceramics can positively influence the osseointegration of biomaterials with bone and, thus, improve implant survival [31][32][33]. ...
The alumina and zirconia surfaces were pretreated with chemical etching using alkaline mixtures of ammonia, hydrogen peroxide and sodium hydroxide, and followed with application of the powder layer of Ca-deficient hydroxyapatite (CDH). The influence of etching bath conditions time and concentration on surface development, chemical composition and morphology of medicinal ceramic powders were studied. The following analyses were performed: morphology (scanning electron microscopy), phase composition (X-ray diffraction analysis), changes in binding interactions and chemical composition (FT-Infrared and Energy dispersive spectroscopies). Both types of etchants did not expose the original phase composition changes or newly created phases for both types of ceramics. Subsequent decoration of the surface with hydroxyapatite revealed differences in the morphological appearance of the layer on both ceramic surfaces. The treated zirconia surface accepted CDH as a flowing layer on the surface, while the alumina was decorated with individual CDH aggregates. The goal of this study was to focus further on the ceramic fillers for polymer-ceramic composites used as a biomaterial in dental prosthetics.
... This is a very promising material for biomedical utilization due to its resemblance to human hard tissue [26][27][28]. However, CDH exhibits a low mechanical strength, which limits its use mainly to low load-bearing applications, such as osteoconductive coatings on metallic or other ceramics prosthesis [29][30][31]. Phosphate ceramics exhibit considerably improved biological affinity and activity, but they contain poor crack growth resistance and poor mechanical properties (in terms of their strength and fracture toughness) in comparison to alumina and zirconia ceramics [29][30][31]. The chemical similarity of HAp to the inorganic components of human bones and teeth has led to extensive research in the field of hard tissue engineering [30]. ...
... However, CDH exhibits a low mechanical strength, which limits its use mainly to low load-bearing applications, such as osteoconductive coatings on metallic or other ceramics prosthesis [29][30][31]. Phosphate ceramics exhibit considerably improved biological affinity and activity, but they contain poor crack growth resistance and poor mechanical properties (in terms of their strength and fracture toughness) in comparison to alumina and zirconia ceramics [29][30][31]. The chemical similarity of HAp to the inorganic components of human bones and teeth has led to extensive research in the field of hard tissue engineering [30]. ...
... Phosphate ceramics exhibit considerably improved biological affinity and activity, but they contain poor crack growth resistance and poor mechanical properties (in terms of their strength and fracture toughness) in comparison to alumina and zirconia ceramics [29][30][31]. The chemical similarity of HAp to the inorganic components of human bones and teeth has led to extensive research in the field of hard tissue engineering [30]. According to earlier works, the use of CDH and HAp as cover layers on oxide ceramics can positively influence the osseointegration of biomaterials with bone and, thus, improve implant survival [31,32]. ...
The alumina and zirconia surfaces were pretreated with chemical etching using alkaline mixtures of ammonia, hydrogen peroxide and sodium hydroxide, and followed with application of the powder layer of Ca-deficient hydroxyapatite (CDH). The influence of etching bath conditions time and concentration on surface development, chemical composition and morphology of medicinal ceramic powders were studied. The following analyses were performed: morphology (scanning electron microscopy), phase composition (X-ray diffraction analysis), changes in binding interactions and chemical composition (FT-Infrared and Energy dispersive spectroscopies). Both types of etchants did not expose the original phase composition changes or newly created phases for both types of ceramics. Subsequent decoration of the surface with hydroxyapatite revealed differences in the morphological appearance of the layer on both ceramic surfaces. The treated zirconia surface accepted CDH as a flowing layer on the surface, while the alumina was decorated with individual CDH aggregates. The goal of this study was to focus further on the ceramic fillers for polymer-ceramic composites used as a biomaterial in dental prosthetics.
... High Velocity Oxygen Fuel (HVOF) sprayed coatings are attractive for corrosion resistance, because they are dense and exhibit low oxidation of raw materials compared to coatings obtained by other thermal spray processes (plasma or wire arc spray) 8 . In addition to the good adhesion, these coatings presented positive results for bone growing either in vitro or in vivo testing [9][10][11][12] . ...
... The employed scan rate for the entire test has been 5 mV/s. Previous studies of coated and uncoated TiAlV alloys used scan rates from ~0.1 to 10 mV/s to evaluate the corrosion behavior of this system 12,13,18,19 , and in many studies high anodic potentials were employed. For all systems, the results are given based on the geometric area, but it is important to mention that the real area can be much higher since as-sprayed samples were used without surface polishing, and therefore, with a relatively high surface roughness. ...
... The anodic current increased with increasing potential, but without a sharp and steady increase in the anodic current typical in pitting attack, and in the reverse scan the current density was always lower than in the direct one, which is characteristic of a more passivated system. Kwok et al. 12 found similar results by polarizing the HA-coated TiAlV electrodes fabricated by electrophoretic deposition up to 4 V/SCE and also Sousa and Barbosa 25 who polarized the coating up to 3 V/SCE. The results shown in Fig. 3 agree with our hypothesis. ...
The electrochemical behavior of HVOF produced hydroxyapatite (HA) and 80HA-20TiO2 coatings were investigated using electrochemical techniques in natural aerated Hanks' solution in the presence and absence of bovine serum albumin (BSA) for 30 days. All samples presented open circuit potential oscillations, which were associated to the porous nature of the coating that allows the electrolyte reaches the substrate causing activation - passivation at the bottom of the pores. The polarization studies indicated that the 80HA-20TiO2 coating was the only one that showed a narrow potential passive region from around -0.4 V to 0 V in the presence and absence of BSA, indicating the beneficial influence of the addition of TiO2 to the HA coating stability. Our results indicated that BSA in Hanks' solution diminishes the stability of the metallic oxide layer present on the Ti-based alloy accelerating the degrading of hydroxyapatites coatings / substrate interface due to its chelating ability.
... bonding ability and increases fixation stability. HA coating of titanium implants thus combines the mechanical and bioinert properties of a well-established implant metal with the osteoconductive properties of HA [7], and as been associated with improved long-term prostheses performance [8]. Available HA coating techniques include plasma spraying, electrophoretic deposition, sputtering and sol?gel synthesis. ...
... Usual drawbacks to these techniques include full or partial HA melting and/or decomposition, difficulty to assure high crystallinity, generation of intermediate calcium phosphate salts other than HA (most often CaO, ?-tricalcium phosphate or ?-tricalcium phosphate) and contamination with reagents. However, the microstructure, range and purity of the calcium phosphate phases produced during the coating process are determinant to the long-term stability, bioactivity and biocompatibility of the coatings [2,5,7,9]. Contamination of HA or formation of deficient HA results in significant changes in its morphological and crystallographic features, affecting the quality of the final product. In as much, development of reliable, scalable and fast coating techniques are of great significance to the biomedical community. ...
... Peaks corresponding to TiO 2 were identified, corresponding to the formation of a thermally grown thin layer of titanium oxide over the metal surface. The TiO 2 layer has been shown to be able to subtract Ca 2+ ions from the HA film to form an intermediate layer of calcium titanate [7, 16]. Accordingly diffraction peaks were detected in the diffractogram in figure 7b corresponding to CaTiO 3 . ...
Ti orthopaedic implants are commonly coated with hydroxyapatite (HA) to achieve increased biocompatibility and osseointegration with natural bone. In this work the dip-coating technique was used to apply HA films on Ti foil. A gel was used as the support vehicle for commercial HA particles. The experimental parameters like surface roughness of the metallic substrate and immersion time were studied. All coated substrates were heat treated and sintered under vacuum atmosphere. The produced coatings were characterized by field-emission gun scanning electron microscopy coupled with energy-dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, microhardness, scratch test and profilometry. Additionally, the apatite-forming ability of the produced material was tested by exposure to a simulated body fluid. Higher substrate surface roughness and longer immersion time produce thicker, denser films, with higher surface roughness. Lower film porosity is accompanied by higher hardness values. However, thicker coating promotes differential shrinkage and crack formation during sintering. Both coating thickness and coating roughness increase with coating time. HA films∼30–40 μm thick with 45–50% HA theoretical density produced on Ti substrates with surface roughness of R
z∼1.0–1.7 μm, display an attractive combination of high hardness and resistance to spallation. Attained results are encouraging regarding the possibility of straightforward production of biocompatible and bioactive prosthetic coatings for orthopaedic applications using commercial HA.
... Many different coating methods are available to fabricate HA coatings, including plasma spraying [17][18][19][20], sputtering [21,22], polymer-assisted methods [23], dipping [24], sol-gel processing [25], electrophoretic deposition [26,27], and hot isostatic pressing [9]. ...
... Commercial orthopedic implants are often plasma-sprayed with HA to accelerate bone attachment [17,18]. However, it has some shortcomings, such as poor coating-metal adhesion strength, non-uniformity in coating thickness, alteration in structural and chemical properties during the coating process, and non-uniformity in coating density [19,20]. Electrostatic spray deposition (ESD) is a process to produce very fine droplets from a liquid by using a DC electric field to break the liquid into fine droplets [28][29][30]. ...
Bacterial infection of implanted materials is a significant complication that might require additional surgical operations for implant retrieval. As an antibacterial biomaterial, Ag-containing hydroxyapatite (HA) may be a solution to reduce the incidences of implant associated infections. In this study, pure, 0.2 mol% and 0.3 mol% Ag incorporated HA powders were synthesized via a precipitation method. Colloidal precursor dispersions prepared from these powders were used to deposit porous coatings onto titanium and stainless steel substrates via electrostatic spraying. The porous coating layers obtained with various deposition times and heat treatment conditions were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Scratch tests were conducted to assess the adhesion strength of the coating. Antibacterial activity of Ag-incorporated HA was tested towards Escherichia coli (E. coli) at various incubation times. Osteoblast adhesion on Ag-incorporated HA was evaluated to assess biocompatibility. Improvement in adhesion strength of the coating layer was observed after the heat treatment process due to mutual ionic diffusion at the interface. The Ag-incorporated HA killed all viable E. coli after 24 h of incubation, whereas no antibacterial activity was detected with pure HA. In addition, in vitro cell culture tests demonstrated osteoblast adhesion similar to pure HA, which indicated good cytocompatibility. In summary, results of this study provided significant promise for the future study of Ag-incorporated HA for numerous medical applications.
... Attempts to coat these fixation plates with bioactive hydroxyapatite (HA) or silica based Bioglass ™ (45S5) did not improve bone regeneration rates. Coating structural quality suffered from high temperature processing (enameling, plasmaspraying) that induced metal-coating thermal expansion mismatch and interfacial cracking (Thomas et al., 1987;Hayashi et al., 1989;Soballe et al., 1990;Dhert et al., 1991;Klein et al., 1991;Wang et al., 1993;Yang et al., 1996;Bloyer et al., 1999;Foppiano et al., 2007), reduced quality and bioactivity owed to glass crystallization and mixing of soluble and insoluble phases (Koeneman et al., 1990;Ji et al., 1992;Weinlaender et al., 1992;Filiaggi et al., 1993;Frayssinet et al., 1993;Zyman et al., 1994;Mcpherson et al., 1995;Gross et al., 1997;Gomez-Vega et al., 2000;Gomez-Vega et al., 2001;Oku et al., 2001). As a result of these factors, immature bone healing and fibrous tissue attachment were ...
In this review, we explore the application of novel biomaterial-based therapies specifically targeted towards craniofacial bone defects. The repair and regeneration of critical sized bone defects in the craniofacial region requires the use of bioactive materials to stabilize and expedite the healing process. However, the existing clinical approaches face challenges in effectively treating complex craniofacial bone defects, including issues such as oxidative stress, inflammation, and soft tissue loss. Given that a significant portion of individuals affected by traumatic bone defects in the craniofacial area belong to the aging population, there is an urgent need for innovative biomaterials to address the declining rate of new bone formation associated with age-related changes in the skeletal system. This article emphasizes the importance of semiconductor industry-derived materials as a potential solution to combat oxidative stress and address the challenges associated with aging bone. Furthermore, we discuss various material and autologous treatment approaches, as well as in vitro and in vivo models used to investigate new therapeutic strategies in the context of craniofacial bone repair. By focusing on these aspects, we aim to shed light on the potential of advanced biomaterials to overcome the limitations of current treatments and pave the way for more effective and efficient therapeutic interventions for craniofacial bone defects.
... Interfacial chemical reactions between hydroxyapatite and titanium are enhanced if the surface of the titanium particles are rich in oxide [46]. This then facilitates the diffusion of hydroxyapatite ions into the titanium to form titanium phosphide and calcium titanate interfaces [47,48]. Additionally, it appears that the matrix experienced dehydration, hence inducing volume and structural changes. ...
Owing to the increasing demand for bone repair strategies, several biomaterials have been developed. Among the materials available for this purpose, hydroxyapatite stands out for its osteoinduction capacity, since it possesses a chemical composition similar to that of inorganic bone constituents. In comparison to bones, the mechanical properties of substitute structures incorporating hydroxyapatite still remain a great challenge for scientists. This study thus presents the synthesis of hydroxyapatite incorporated with a natural bioceramic and a metallic phase of excellent biocompatibility to obtain dense biomaterials with improved mechanical strength. The mechanical responses of the synthesized biomaterials are presented and discussed. The results obtained indicate that the hydroxyapatite-natural ceramic systems fulfils the general mechanical property requirements for some bone repair applications. Separately, the synthesis of titanium-based systems was shown to be much more challenging, but promising. Therefore, recommendations for suppressing the issues with the metal-ceramic interfacial bonding strength were provided.
... In HA ocular implantation, in treatment of herniation, in fusing and repairing of vertebrae, for bone repair, for covering cavity caused by bone loss, in dentistry. In screws and bone plates, for treating periodontal damage, in curing dental defects, for the replacement of subperiosteal teeth, for metal coating which is specifically used for implants Boutin (1981), Dorlot et al. (1988), Zimmerman et al. (1991), Chignier et al. (1987), Grote (1987) Bajpai and Graves (1980), Ricci et al. (1986), Freeman et al. (1981), Khavari and Bajpai (1993), Morris and Bajpai (1987) Grote (1987), Ji et al. (1992), Whitehead et al. (1993), Hulbert (1992), Reck et al. (1988) 2. BioComposites Bone cement, dental implants, cardiovascular valves and stents, joint replacements, cranial bones repair, bone grafts, also used in tendon implants and intervertebral disks, as fillers ...
A significant progress has been made in the field of biomaterial science over the years. Inorganic biomaterials are thought to be a special class of materials, which are used by doctors, surgeons, and scientists as numerous tissues in the human body such as bones, teeth, tendons, ligaments, and other weight-bearing implants, and their replacements are carried out with the help of these biomaterials. This chapter provides an overview of various inorganic biomaterials and their classification into different groups viz. metals and alloys, ceramics, composites, and polymers along with their basic properties. Moreover, the specific requirements for each group like biocompatibility, physical and mechanical properties, chemical stability, load-bearing capacity, and wear and corrosion resistance have been analyzed. Furthermore, important biomedical applications of the different biomaterials used in drug delivery devices, orthopedic and dental implants, cardiovascular valves and stents, hip and joint replacements, surgical instruments, and implants coatings, etc., have also been explained.KeywordsInorganic biomaterialsMetallic and nonmetallic biomaterialsBiomedical applications
... HA coating level of significance has increased due to showing an improved osteoconductive properties (Surmenev et al., 2014). This material was introduced to combine the high metal strength and the bioactivity of calcium phosphate (Ca 3 (PO 4 ) 2 ) (Ji et al., 1992). Upon investigating the coating morphology, structure and composition, the coating material was found to be thicker in the apical portion of dental implants (Civantos et al., 2017). ...
Dental implants have been commonly used to replace missing teeth using titanium and other materials with various advancements in their composition and design. Recent studies have been focusing on the surface modification of dental implants, as it is crucial to enhance its biocompatibility and osteoconductive properties. Bioactive glass (BAG) can be used as a coating since it is a promising biomaterial for bone repair and regeneration, and it can be made through two main procedures: the fusion process and the sol–gel method. Different coating techniques are available yet only the plasma spraying technique has been used in biomaterials. BAG coating onto dental implants can form a strong bond with the bone within a short span of time and provide a surface for cells to attach to in order to proliferate, and deposit matrix added to its high bioactivity index. The procedure will achieve better implant osseointegration and reduce prosthetic corrosion. Therefore, it will increase the success and survival rate of dental implants.
... Although studies show encouraging results for plasma-sprayed HAp coatings [25], some of the intrinsic features of this method remain concerning for tissue engineering applications. These include the presence of amorphous phases resulting from the extremely high process temperatures [26] and the difficulty of coating implants with complex geometrical features due to the line-of-sight nature of the process [27]. Alternative methods include: Sol-gel processing [28,29], biomimetic deposition [30][31][32], hydrothermal processing [33], electrophoresis [34], gas detonation deposition [35][36][37], and electrodeposition [38][39][40]. ...
In this study, we demonstrate that a uniform coating of hydroxyapatite (HAp, Ca10(PO4)6(OH)2) can be electrochemically deposited onto metallic 3D-woven bone scaffolds to enhance their bioactivity. The HAp coatings were deposited onto metallic scaffolds using an electrolyte containing Ca(NO3)2·4H2O, NH4H2PO4, and NaNO3. The deposition potential was varied to maximize the uniformity and adhesion of the coating. Using X-ray diffraction (XRD), Raman spectroscopy, and energy-dispersive spectroscopy (EDS), we found crystallized HAp on the 3D-woven lattice under all deposition potentials, while the −1.5 V mercury sulfate reference electrode potential provided the best local uniformity with a satisfactory deposition rate. The coatings generated under this optimized condition were approximately 5 µm thick and uniform throughout the internal and external sections of the woven lattice. We seeded and cultured both coated and uncoated scaffolds with human adipose-derived stromal/stem cells (ASCs) for 12 h and 4 days. We observed that the HAp coating increased the initial cell seeding efficiency by approximately 20%. Furthermore, after 4 days of culture, ASCs cultured on HAp-coated stainless-steel scaffolds increased by 32% compared to only 17% on the uncoated scaffold. Together, these results suggest that the HAp coating improves cellular adhesion.
... Adhesion is overwhelmingly provided by mechanical clamping of coating particles to asperities of the roughened surface of the metallic substrate. Despite claims that a thin reaction layer of calcium dititanate (CaTi 2 O 5 ) or calcium titanate (perovskite, CaTiO 3 ) exists that will mediate adhesion [35][36][37], experimental evidence of such a reaction layer in as-sprayed coatings is scant or absent. Owing to its thinness, visualization by transmission electron microscopy even at high magnification [20] is hampered by its exiguity owing to the very short diffusion paths of Ca 2+ and Ti 4+ ions, respectively, that render any potential reaction zone extremely thin. ...
During the last several decades, research into bioceramic coatings for medical implants has emerged as a hot topic among materials scientists and clinical practitioners alike. In particular, today, calcium phosphate-based bioceramic materials are ubiquitously used in clinical applications to coat the stems of metallic endoprosthetic hips as well as the surfaces of dental root implants. Such implants frequently consist of titanium alloys, CoCrMo alloy, or austenitic surgical stainless steels, and aim at replacing lost body parts or restoring functions to diseased or damaged tissues of the human body. In addition, besides such inherently corrosion-resistant metals, increasingly, biodegradable metals such as magnesium alloys are being researched for osseosynthetic devices and coronary stents both of which are intended to remain in the human body for only a short time. Biocompatible coatings provide not only vital biological functions by supporting osseoconductivity but may serve also to protect the metallic parts of implants from corrosion in the aggressive metabolic environment. Moreover, the essential properties of hydroxylapatite-based bioceramic coatings including their in vitro alteration in contact with simulated body fluids will be addressed in this current review paper. In addition, a paradigmatic shift is suggested towards the development of transition metal-substituted calcium hexa-orthophosphates with the NaSiCON (Na superionic conductor) structure to be used for implant coatings with superior degradation resistance in the corrosive body environment and with pronounced ionic conductivity that might be utilized in novel devices for electrical bone growth stimulation.
... Titanium was oxidized to be Ti 6 O (850 and 900°C), Ti 3 O (950 and 1000°C) and Ti 2 O (1100°C) in turn until the appearance of TiO 2 , which could decelerate the diffusion rate of oxygen [27]. The formation of Ti 4 P 3 was ascribed to the diffusion of P ions from α-TCP into Ti particles, which were favorably formed under non-oxidizing vacuum atmosphere [28]. Furthermore, P ion had a small radius, and a low diffusive activation energy, thus was more active [26]. ...
A titanium mesh scaffold composite filled with Ti/α-TCP particles was prepared by spark plasma sintering (SPS). The microstructures and interfacial reactions of the composites were investigated by scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray diffraction analyses (XRD). The compressive strength and elastic modulus were also measured. In vitro bioactivity and biocompatibility was evaluated by using simulated body fluid and cells culture, respectively. After high temperature sintering, Ti oxides, TixPy and CaTiO3 were formed. The formation of Ti oxides and TixPy were resulted from the diffusion of O and P elements from α-TCP to Ti. CaTiO3 was the reaction product of Ti and α-TCP. The composite of 70Ti/α-TCP incorporated with Ti mesh showed a high compressive strength of 589 MPa and a low compressive modulus of 30 GPa. The bioactivity test showed the formation of a thick apatite layer on the composite and well-spread cells attachment. A good combination of mechanical properties and bioactivity indicated a high potential application of Ti/α-TCP/Ti-mesh composite for orthopedic implants.
... The mineral layer that results was highly soluble (22-62% amorphous calcium phosphate) and incorporated multiple calcium phosphate phases (in addition to the HA overlay). [16][17][18][19][20][21][22][23] Hench and colleagues 24 developed a glass material that releases calcium and phosphate ions to cells (as raw materials for osteoblast mineralization) while forming a bone-like HA surface for mineralized tissue attachment. However, coatings involving Bioglass resulted in delamination at the metal-glass/ceramic interface. ...
Bioactive glasses release ions, those enhance osteoblast collagen matrix synthesis and osteogenic marker expression during bone healing. Collagen matrix density and osteogenic marker expression depend on osteogenic transcription factors, (e.g., Osterix (OSX)). We hypothesize that enhanced expression and formation of collagen by Si(4+) depends on enhanced expression of OSX transcription. Experimental bioactive glass (6P53-b) and commercial Bioglass(TM) (45S5) were dissolved in basal medium to make glass conditioned medium (GCM). ICP-MS analysis was used to measure bioactive glass ion release rates. MC3T3-E1 cells were cultured for 20 days, and gene expression and extracellular matrix collagen formation was analyzed. In a separate study, siRNA was used to determine the effect of OSX knockdown on impacting the effect of Si(4+) on osteogenic markers and matrix collagen formation. Each bioactive glass exhibited similar ion release rates for all ions, except Mg(2+) released by 6P53-b. Gene expression results showed that GCM markedly enhanced many osteogenic markers, and 45S5 GCM showed higher levels of expression and collagen matrix fiber bundle density than 6P53-b GCM. Upon knockdown of OSX transcription, collagen type 5, alkaline phosphatase, and matrix density were not enhanced as compared to wild type cells. This study illustrates that the enhancement of elongated collagen fiber matrix formation by Si(4) (±) depends on OSX transcription. This article is protected by copyright. All rights reserved.
... 12 Several studies have involved ex situ high resolution transmission electron microscopy (HRTEM) and/or atomic force microscopy (AFM) of calcium phosphates produced under different conditions. [13][14][15][16] Manso et al. used both AFM and HRTEM to study the structure of thin (<0.3 mm) sodium-and carbonate-containing HAP that was grown from a basic solution (pH 9.1) on Si (100) and Ti/Si (100) surfaces, either spontaneously or by þ2 V activation. 13 Surface enrichment with hydroxyl ions, (OH) ads À , due to the application of a positive potential resulted in numerous nucleation sites and finer grains of HAP compared to the non-activated condition. ...
... There have been some attempts to understand the interface between HA and metallic substrates, especially titanium. One study documented CaTi 2 O 5 and tricalcium phosphate formation at the HA/Ti interface as a reaction product in samples prepared with plasma spraying (Ji et al., 1992). Other studies, however, showed CaTiO 3 and tricalcium phosphate formation (Geesink et al., 1988; Ji et al., 1992; Ergun et al., 2003). ...
The aim of the current study is to investigate the reaction of hydroxylapatite with both metallic titanium
and titanium oxide, and to examine the e�ect of atmosphere on these reactions. For this purpose, hydroxylapatite
composites with both metallic titanium powder and titanium oxide were prepared and sintered at
1100
�
C for 2 h under 2 di�erent conditions: in air and in evacuated glass tubes with hot isostatic pressing at
120MPa. The reaction was monitored with XRD and thermal analysis. No signi�cant reaction was identi�ed
between hydroxylapatite and metallic titanium in the vacuum environment. However, a reaction occurred
between hydroxylapatite and titanium oxide, which formed CaTiO3 with a perovskite structure, Ca3(PO4)2
(whitlockite) and water. The presence of air in the sintering environment promoted this reaction.
... Der Grund dafür liegt vermutlich darin, dass sich an der Grenzfläche Titanoxid-HVS und HAp-Schicht eine sehr dünne Reaktionschicht von Calciumtitanat (Perowskit) bzw. Calciumdititanat [16] oder Ti-substituiertem Hydroxylapatit (Ca 10n Ti n/2 [(PO 4 ) 6 (OH) 2 ]) [17] bildet. Da beim APS-Spritzen von TiO 2 reaktive unterstöchiometrische Oxidphasen vom Magnéli-Typ Ti n O 2n-1 entstehen, werden die Grenzflächenreaktionen mit HAp kinetisch begünstigt. ...
... 14,15 Although, Si substitution in CaP bioceramics has received extensive studies, there are not many efforts towards understanding effects of SiO 2 addition in different amounts on the wetting and in vitro bioactivity of these composite ceramic coatings. In the meanwhile, although, most of the techniques, including plasma spray deposition, 16 magnetron sputtering, 17 sol-gel based coatings 18 and electrophoretic deposition, 19 have been applied to obtain CaP coatings, they suffer from certain drawbacks such as poor adherence of the coating to the substrate material, lack of uniformity, absence of appropriate topographical cues at the surface and absence of desirable chemistry. ...
Calcium phosphate bioceramic and SiO2-CaP bioceramic composite coatings were prepared on Ti-6Al-4V substrates by laser cladding method. Surface energy components were calculated and the wettability of the coatings in simulated body fluid (SBF) was investigated. In vitro bioactivity of the coatings were performed by immersing in SBF and analysed for the precipitation of hydroxyapatite (HA). The effects of SiO2 content on the wettability and in vitro bioactivity of the bioceramic composite coatings were investigated. The surface energy values increased as the percentage of SiO2 in the coating precursor increased, resulting in decrease in contact angle with SBF for improved wettability. X-ray diffraction results indicated that after immersion in SBF for more than three days, 17 wt-%SiO2-CaP and 25 wt-%SiO2-CaP samples possessed highly intense peaks of HA than 100 wt-% CaP sample. Furthermore, in vitro bioactivity assays show that the SiO2-CaP bioceramic composite coatings possess a higher HA precipitation rate than CaP coating and Ti-6Al-4V control.
... The specimen thickness generally should be less than 50 nm for EELS analysis [19]. However, during STEM observations, the concentrated electrons in a narrow specimen could cause specimen distortion or fracture, so too thin specimens can be a problem [20]. Furthermore, biological specimens like the bone specimen used in this study are weaker than inorganic materials like minerals and metals, so thicker slices have usually been used. ...
Until now, the chemical bonding between titanium and bone has been examined only through a few mechanical detachment tests. Therefore, in this study, a sandblasted and acid-etched titanium mini-implant was removed from a human patient after 2 months of placement in order to identify the chemical integration mechanism for nanoscale osseointegration of titanium implants. To prepare a transmission electron microscopy (TEM) specimen, the natural state was preserved as much as possible by cryofixation and scanning electron microscope/focused ion beam (SEM-FIB) milling without any chemical treatment. High-resolution TEM (HRTEM), energy dispersive X-ray spectroscopy (EDS), and scanning TEM (STEM)/electron energy loss spectroscopic analysis (EELS) were used to investigate the chemical composition and structure at the interface between the titanium and bone tissue. HRTEM and EDS data showed evidence of crystalline hydroxyapatite and intermixing of bone with the oxide layer of the implant. The STEM/EELS experiment provided particularly interesting results: carbon existed in polysaccharides, calcium and phosphorus existed as tricalcium phosphate (TCP), and titanium existed as oxidized titanium. In addition, the oxygen energy loss near edge structures (ELNESs) showed a possibility of the presence of CaTiO3. These STEM/EELS results can be explained by structures either with or without a chemical reaction layer. The possible existence of the osseohybridization area and the form of the carbon suggest that reconsideration of the standard definition of osseointegration is necessary.
... However, HAp it is brittle; therefore, HAp is coated on the surface of biomedical titanium alloys to impart them hard-tissue compatibility and bioactivity. Many studies on HAp coatings prepared by plasma spray, sol-gel, and sputtering techniques have been reported [7][8][9][10][11]. Chemical vapor deposition (CVD) is allows the fabrication of coatings at a high deposition rate with excellent microstructure controllability and step coverage [12]. ...
Recently, low-modulus β-type titanium alloys have been the focus of considerable attention because of their high biocompatibility and their low moduli that make them effective for inhibiting bone atrophy and for enhancing bone remodeling. However, the biofunctinalities of titanium alloys, such as bone conductivity, blood compatibility, and soft tissue compatibility, are poor. Therefore, surface modification techniques such as bioactive ceramic surface modification and blood-and soft-tissue-compatible polymer surface modification are applied to titanium alloys. Hydroxyapatite (HAp) surface modification via metal organic chemical vapor deposition (MOCVD) and segmented polyurethane (SPU) surface modification via silane coupling treatment are effective techniques to add biofunctionalites to titanium alloys. HAp surface modification via MOCVD and SPU surface modification using three kinds of silane coupling agents on a low modulus beta-type titanium alloy, namely, TNTZ, are discussed. Moreover, the bonding strengths of HAp and SPU on the surface of TNTZ, which are important parameters, are also discussed.
... These ceramics have found use in applications that require high strength and wear resistance and have been applied as femoral heads in total hip replacement surgery [49]. Calcium phosphates such as hydroxyapatite (HA) and tricalcium phosphate have also been the object of rigorous study for use as biomaterials and have been employed frequently as metal coatings [50][51][52][53][54][55][56], in bone cements [57][58][59][60][61][62] and in non-load bearing bone replacement products [63][64][65][66][67]. Bioglasses and glass ceramics also have been studied for their applicability in bone repair and regeneration [68][69][70][71][72]. It is reported that A-W glass ceramic (a glass-ceramic comprised of two mineral components, wollastonite (CaO·SiO 2 ) and oxyfluorapatite Ca 10 (PO 4 ) 6 (OH,F) 2 in a glassy ...
... Crystal size of the initial layers is very small as rapid cooling and rapid solidification at substrate restrict crystal growth. The size of the crystal increases from interface towards coating surface due to smaller cooling rates [13][14]. The solidified splat is affected by the heat content of incoming molten splat. ...
Plasma spraying is most used thermal spray process for coating of bioceramic and bioinert materials. It is line of sight technique, easy to use and inexpensive as compared to other processes used for coatings. The main disadvantage of this technique for coating hydroxyapatite (HA) is that due to high temperature of plasma (of the order of 16000°C) HA tends to degrade into amorphous calcium phosphates. These amorphous phases are not desirable and have a tendency to dissolve in body environment. In this article an attempt has been made to understand the plasma spraying process for coating of hydroxyapatite.
Two implant types of hydroxyapatite (HA) currently are available for dental implants: dense HA-cemented titanium (Ti) and HA-coated. It has been shown in previous reports that there are differences in the chemical and mechanical stabilities between the dense HA and HA coated. The differences are thought to be due to structural differences between the two ceramic types. The aim of this study was to investigate the differences in microstructural characteristics of currently available dense HA and HA coated implants before implantation and at periods of 3 weeks and 10 months after implantation in canine bone. X-ray diffractometry, infrared analysis, transmission electron microscopy, and energy dispersive X-ray analysis were used. The dense HA is composed of crystal grains, with a well crystallized structure of HA, closely bound to each other and approximately 0.4∼0.6 μm in size. Implantation did not change the original sintered structure of the dense HA. The HA coating was composed of an amorphous phase with a Ca/P ratio of 1.46 and a crystal phase consisting of oxyhydroxyapatite, tricalcium phosphate, tetracalcium phosphate, and CaO, with a Ca/P ratio of 1.57. In the amorphous phase, compared to other portions in the amorphous phase, there were some layers with lower atomic density and with no significant difference in Ca/P ratio. After implantation, the crystallization of super fine crystals of approximately 4∼5 nm in thickness occurred in the amorphous phase, and with time it progressed and spread from the surface to the deeper portion of the HA coating. A Ca/P ratio of 1.58 in the crystallized portion was close to the ratio (1.60) in the dense HA, suggesting that the super fine crystals were HA. This crystallization cannot significantly decrease the solubility of the amorphous phase portion and poses risks of stress accumulation within the coating and a decrease of binding strength between the HA coating and the substrate. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 296–303, 1998.
Hydroxyapatite (HA) extracted from bovine bones (called as natural HA) was used to coat a relatively new developed titanium alloy, Ti-12Cr, by using the electrophoretic deposition (EPD) method. This is to improve biocompatibility and bioactivity properties of the material to achieve optimal osseointegration in orthopaedic implant applications. There are three particle sizes of the natural HA used in this study (25 μm, 63 μm, and 125 μm) which aims to determine their effect on morphology, structure, and the strength of the resulting coating adhesion. The coating process was carried out at a voltage of 5 Volt for 5 minutes. The resulting layer morphologies and surface coverage were observed using an optical microscope. The increase in sample mass was measured using digital scales to determine the amount of the particles deposition. The coating thickness was measured using coating thickness gauges, and adhesion strength the coating layer was measured by using the cross-cut tape test method. The results of this study indicate that the HA particle size influences significantly on the quality of the coating produced after the EPD process. It is found that the coated Ti-12Cr with a small particle size has better surface properties as compared to the coarse one. Therefore, small size natural HA particles seemmore suitablefor implant applications.
Aim: The study aimed to understand the interfacial bonding and diffusion of elements between substrate metal and HA-coated titanium implants in different plasma gas atmosphere. Materials and methods: Commercially pure titanium and Ti-6Al-4V substrate metals were coated with hydroxyapatite by plasma spray in plasma gas atmospheres of argon, argon/ hydrogen, nitrogen, and nitrogen/hydrogen. The microstructure and interfacial bonding between the metal substrate and HA coating were studied by scanning electron microscopy, energy dispensive X-ray analysis (EDAX), and X-ray diffraction. Results: The analyses of the coatings obtained showed a different microstructural pattern of HA and diffusion of elements across the interface of metal and HA coating and chemical bonding for all plasma gas atmospheres. Conclusion: The plasma-coating atmosphere influences the microstructure and crystallization of HA. Diffusion of elements from metal substrate to HA coating and coating to metal surface indicate chemical bonding between the metal and coating in addition to usual mechanical bonding. Clinical significance: Bonding between the metal substrate and HA coating play a significant role in the stability of the dental implant. In addition to mechanical bonding, the plasma coated implants show some amount of chemical bonding at the interface. © 2018, Jaypee Brothers Medical Publishers (P) Ltd. All rights reserved.
This study represents the first report of the physical and chemical changes occurring in coatings of failed hydroxyapatite (HA)-coated titanium implants obtained from a comprehensive, multicenter human dental implant study. A total of 53 retrieved samples were obtained and compared with unimplanted controls with the same manufacturer and similar manufacture dates. Forty-five retrieved implants were examined for surface characteristics and bulk composition. Implants were staged based on implantation history: stage 1 (implants retrieved between surgical placement and surgical uncovering), stage 2 (implants retrieved at surgical uncovering and evaluation), stage 3 (implants retrieved between surgical uncovering evaluation and occlusal loading), and stage 4 (implants retrieved after occlusal loading). Scanning electron microscopy showed progressive coating thinning with implantation time. At later stages, bare Ti metal was detected by energy-dispersive X-ray analysis and electron spectroscopy for chemical analysis. Increases in Ti and A1 (2–7.5 atm % each) were detected at the apical ends of all stage 4 samples. In unimplanted coatings, X-ray diffraction analysis demonstrated the presence of amorphous calcium phosphate, β-tricalcium phosphate, tetracalcium phosphate, and calcium oxide in addition to large hydroxyapatite crystals (c axis size, D002 = 429 ± 13 Å; a axis size, D300 = 402 ± 11 Å, a/c aspect ratio 0.92). The nonapatitic phases disappeared with increased implantation time, although there was a persistence of amorphous calcium phosphate. Bulk coating chemical analysis showed that Ca/P ratios for implant controls (1.81 ± 0.01) were greater than stoichiometric HA (1.67) and decreased for implant stages 3 and 4 (1.69 ± 0.09 and 1.67 ± 0.09, respectively), explained by the dissolution of the non apatitic phases. Crystal sizes also changed with implantation times, being smaller than the control at all but stage 4. Fourier transform infrared analyses agreed with these results, and also indicated the accumulation of bone (protein and carbonate-apatite) in the retrieved coatings. The accumulation of bone was not stage dependent. These findings indicate that there was some biointegration with the surrounding bone, but the greatest changes occurred with the HA coating materials, their loss, and chemical change. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res 54: 480–490, 2001
Considerable progress has been made over the last decades in thermal spray technologies, practices and applications. However, like other technologies, they have to continuously evolve to meet new problems and market requirements. This article aims to identify the current challenges limiting the evolution of these technologies and to propose research directions and priorities to meet these challenges. It was prepared on the basis of a collection of short articles written by experts in thermal spray who were asked to present a snapshot of the current state of their specific field, give their views on current challenges faced by the field and provide some guidance as to the R&D required to meet these challenges. The article is divided in three sections that deal with the emerging thermal spray processes, coating properties and function, and biomedical, electronic, aerospace and energy generation applications.
The electrocrystallization - hydrothermal synthesis process was used for fabricating hydroxyapatite biocoatings on metallic substrates at low temperatures with aqueous electrolytes containing Ca - and P - bearing ions. Scanning electron microscopy (SEM), X -ray diffraction (XRD) and infrared spectroscopy (IR) were used to analyze the morphology, structure and chemical composition of the coatings. Bonding strength and biocompatibility of the coatings were measured. The results show that the coatings prepared by this process are wholly composed of needle - like hydroxyapatite, and hvae a good uniformity and high purity. The bonding strength is about 15 MPa. Though the mass of the coating decreases as the coating is immersed in the Ringer's solution for 12 months, no changes in the phase composition and morphology were observed.
It is widely recognized that the rapid and continuing change in emphasis in materials science away from traditional engineering materials has been largely instituted by the requirements of emerging technologies for advanced and structurally sophisticated new materials. Medical engineering, often included in the list of advanced technologies, requires the underpinning of high-tech materials. The word which is used to categorize materials for biomedical applications is “biomaterial”.
In this work, a novel electrodeposition has been developed to prepare a hybrid coating of calcium phosphate/chitosan on the surface of Ti alloy. The surface morphologies, chemical compositions and crystalline structures of the hybrid coatings are characterized by using various spectroscopic techniques, such as SEM, XPS, FTIR and XRD etc.. The results indicate that a hybrid coating of calcium phosphate/chitosan is formed on the metal surface when adding minor of chitosan to the electrolyte of calcium phosphate under the electrodeposition condition. The morphology of the hybrid coating is significantly different with that of the pure calcium phosphate. It is also shown that the bonding strength of the hybrid coating to the metal substrate has been increased as high as 2.6 MPa because of the incorporation of chitosan in the coating. Meanwhile, the chitosan is a natural polymer compound with good biological-properties, it is proposed to be of a high biocompatibility and an excellent biocompatibility when forming a hybrid coating of calcium phosphate/chitosan on a metal substrate. It means that the electrodeposited hybrid coating of calcium phosphate/chitosan developed in our lab may become a new promising implant biological material.
During the past decades, many attempts have been made to optimise the essential properties of osseoconductive bioceramic coatings deposited by conventional atmospheric plasma spraying. These properties include, but are not limited to, coating cohesion and adhesion, phase composition, homogeneous phase distribution, crystallinity, porosity and surface roughness, nano-structured surface morphology, residual coating stresses and coating thickness (Fazan and Marquis, 2000; Heimann, 2006a). In this chapter, salient structural features of plasma-sprayed bioceramic coatings will be discussed, their performance profiles and biological functions explained, and some testing procedures outlined. An account on more detailed characterisation and test methods can be found in Chapter 7. Plasma spraying of hydroxyapatite is still the most commonly used technique to coat the stems of hip endoprostheses. Details on the thermal alteration of hydroxyapatite in response to the extremely hot plasma jet will be given, and the in vitro interaction of deposited coatings with simulated body fluid discussed. In addition, the role of bond coats that are designed to mechanically strengthen the osseoconductive top coat, to improve coating adhesion to the metallic substrate and to control the crystallisation kinetics and phase content of the plasma-sprayed calcium phosphate coatings will be elucidated. Composite hydroxyapatite/titania and hydroxyapatite/zirconia coatings as well as novel bioceramic coatings based on transition metal-substituted calcium orthophosphates will also be discussed.
Ceramics are defined as the art and science of making and using solid articles that have as their essential component inorganic nonmetallic materials [Kingery et al., 1976]. Ceramics are refractory, polycrystalline compounds, usually inorganic, including silicates, metallic oxides, carbides and various refractory hydrides, sulfides, and selenides. Oxides such as Al2O3, MgO, SiO2, and ZrO2 contain metallic and nonmetallic elements and ionic salts, such as NaCl, CsCl, and ZnS [Park and Lakes, 1992]. Exceptions to the preceding include covalently bonded ceramics such as diamond and carbonaceous structures such as graphite and pyrolized carbons [Park and Lakes, 1992].
This study was aimed at comparing the osseointegration of titanium (Ti)-based Küntscher nails (K-nails) and plates with modified nanostructured and hydroxyapatite-coated surfaces in a rat femur model. Material surfaces were first modified via a simple anodization protocol in which the materials were treated in hydrogen fluoride (1% w/w) at 20 V. This modification resulted in tubular titanium oxide nanostructures of 40–65 nm in diameter. Then, hydroxyapatite-deposited layers, formed of particles (1–5) μm, were produced via incubation in a simulated body fluid, followed by annealing at 500°C. Both surface modifications significantly improved cell proliferation and alkaline phosphatase (ALP) activity as compared to the control (non-modified Ti implants). The controls and modified nails and plates were implanted in the femur of 21 male Sprague-Dawley rats.
The implants, with surrounding tissues, were removed after 10 weeks, and then mechanical tests (torque and pull-out) were performed, which showed that the modified K-nails exhibited significantly better osseointegration than the controls. Histologic examinations of the explants containing plates showed similar results, and the modified plates exhibited significantly better osseointegration than the controls. Surface nanostructuring of commercially available titanium-based implants by a very simple method – anodization – seems to be a viable method for increasing osseointegration without the use of bioactive surface coatings such as hydroxyapatite.
Additive Manufacturing (AM) - is a technology that fabricates the parts directly from 3D CAD model without the need of any process planning. The convergence of AM and life science has evolved into a new paradigm called Bio-Additive Manufacturing (BAM). In this paper, Hydroxyapatite (HA) powder was coated over the customized implant, which will serve as a good candidate for bone substitutes due to its chemical and structural similarity to bone. Computer Tomography (CT) scan data of human tibia bone was collected and stacked in MIMICS image processing software, which converts it into 3D data, then implant was fabricated using Selective Laser Sintering (SLS), an AM technique with polyamide powder. Hydroxyapatite powder was synthesized by wet chemical process and coated over implant using plasma spray coating machine. This coating will produce an intermediate region between the bone and the implant, which will stimulate the tissue growth and bone contact. Micrograph of coated and uncoated implant was analyzed using SEM and EDX. For In-Vitro study human mesenchymal cell was cultured over the coated implant. The viability and proliferation of the cells was studied by examining the morphology of the cell. Thus the implant was fabricated using SLS technique and coated with hydroxyapatite powder which exhibits a favorable and good response to enhance tissue growth.
The structural and functional contact of implant surface with the surrounding bone is an important and crucial aspect to determine the long-term success of the device. Current trends have achieved a drastic enhancement in osseointegration at the bone-implant interface after modifying the surface topography of implant surface particularly at the nanoscale level. This review discusses an overview of the most common manufacture techniques and the related cells-surface interactions. It also describes the available data on nanoscale modifications mentioning their risks and benefits. Nanotechnology has opened new opportunities for tissue engineers and biologists to interact and understand relevant biological processes and cell specific functions. Nanoscale modification of titanium endosseous implant surfaces can alter cell behavior and their responses that may significantly benefit dental implant therapy. KEYWORDS: Nanotopography; Dental implant; Stem cells; Surface treatment; Osseointegration; Differentiation.
The structural and functional contact of implant surface with the surrounding bone is an important and crucial aspect to determine the long-term success of the device. Current trends have achieved a drastic enhancement in osseointegration at the bone-implant interface after modifying the surface topography of implant surface particularly at the nanoscale level. This review discusses an overview of the most common manufacture techniques and the related cells-surface interactions. It also describes the available data on nanoscale modifications mentioning their risks and benefits. Nanotechnology has opened new opportunities for tissue engineers and biologists to interact and understand relevant biological processes and cell specific functions. Nanoscale modification of titanium endosseous implant surfaces can alter cell behavior and their responses that may significantly benefit dental implant therapy.
Electrolytic calcium phosphate depositions on stainless steel were carried out by electrolyzing 0.21 mol/dm3 Ca (H2PO4)2. H2O solutions added with and without NaNO3 at a cathode current of mainly 6mA/cm2 at 20-90°C. CaHPO4 2H2 O formed below 30±5°C and CaHPO4 above the temperature. Both plate-like crystals were deposited nearly parallel to the stainless steel cathode face, and changed to fine grains with increasing current. By further increasing current or decreasing calcium phosphate concentration the formation of apatite became possible.
Hydroxyapatite (HAp: Ca10(PO4)6(OH)2 thin films having porous structure were prepared by sol-gel process with dip-coating using calcium acetate (Ca(CH3COO)2·H2O) and triethylene phosphate.
In the present study, the surface of titanium metal was coated with a sodium-titanium oxide layer by sol-gel process treatment with alkali hydroxide solutions. HAp thin film prepared on modified titanium substrate was then obtained at 800°C (under transformation point of titanium metal) so at lower temperature than previous process. Peeling of HAp thin film was prevent by the formation of sodium-titanium oxide layer. Calcium oxide free HAp films were synthesized with acetate as a raw materials of calcium and rapid heating at 800°C for 1 hr. The films were chemically bonded to the substrate and had a porous structure which was expected to show a good bioactivity.
The purpose of the present work was to investigate synthetic condition of viscous coating sol by sol-gel technique in reaction of Ca(NO3)2-(C2H5O)3PO-C2H5OH system, burning temperature after dip-coating the viscous sol onto alumina substrate and thick control of porous hydroxyapatite (HAp, Ca10(PO4)6(OH)2) coating on the substrate as bone substitute. The products on the substrate were characterized by using X-ray diffraction, scanning electron microscopy, infrared spectroscopy and chemical analysis. The formation of viscous sol as precursor of amorphous calcium phosphate (ACP) was remarkably affected by synthetic conditions such as aging time, Ca/P atomic ratio and pH in an initial mixed solution. In order to stabilize porous HAp coating onto alumina substrate, it was more effective to burn at 1000 °C after dip-coating onto the substrate with viscous sol which formed by aging for 8 days under conditions of Ca/P atomic ratio 1.5 and pH 8 in an initial mixed solution. Also the thickness of HAp layer on the substrate was continuously increased by repeating dip-coating processes 2 to 3 times and developed to about 20μm after repeating 3 times. Consequently, the production of the new artificial biomaterials which joined strongly to the thin layer of HAp on surface of alumina substrate was expected.
The formation of the gel structure during the solgel processing of hydroxyapatite is characterized in this study. The FTIR spectra of the sols and gels at various time periods are examined to identify the structural species present. After characterization of the dried gel, the development of the different phases is examined during heat treatment of the gel to form hydroxyapatite. Results from X-ray diffraction, FTIR spectroscopy and thermal analyses are correlated to identify the various reactions taking place during heat treatment of the gel and to identify the temperatures at which these changes are occurring.
A hydroxyapatite(HAp)film was fabricated on the surface of Ti-29Nb-13Ta-4.6Zr(TNTZ)using a metal-organic chemical vapor deposition(MOCVD)technique, and the mechanical biocompatibility and HAp formability of HApcoated TNTZ were evaluated and discussed in this study. HAp film is fabricated on the surface of TNTZ by controlling the heating temperature of the source bis-dipivaloylmethanatocalcium((Ca(dpm)2)and(C 6H5O)3PO). An α-phase precipitates in the TNTZ matrix after heating the substrate, and the mechanical properties and Young's modulus of HApcoated TNTZ are improved. HAp-coated TNTZ maintains excellent mechanical biocompatibility. The formability of HAp on HAp-coated TNTZ in Hank's balanced salt solution is better than that of HAp on non-coated TNTZ.
(HAp/SiO2)/Ti biocomposites were prepared by the powder metallurgy method. The phase compositions and the in vitro bioactivity of such biocomposites were systematically characterized. The XRD result shows that the phase compositions of (HAp/SiO2)/Ti composites are mainly composed of Ca4O(PO4)2 (TTCP), Ti, TiO2 and CaO. The synthesized (HAp/SiO2)/Ti biocomposites exhibit a good bioactivity, for example, after the samples are immersed in SBF solution only for 24 hours, the bone-like layer consisting of spherical apatite crystal clusters has deposited on the surface of the samples. The density and thickness of the apatite layer increases with increasing immersion time. The formation process and mechanisms of bone-like apatite layer are also discussed.
A hydroxyapatite (HAp) film was fabricated on the surface of Ti-29Nb-13Ta-4.6Zr (TNTZ) using a metal-organic chemical vapor deposition (MOCVD) technique, and the mechanical biocompatibility and HAp formability of HAp-coated TNTZ were evaluated and discussed in this study. HAp film is fabricated on the surface of TNTZ by controlling the heating temperature of the source (bis-dipivaloylmethanatocalcium (Ca(dpm)2) and (C 6H5O)3PO). An α-phase precipitates in the TNTZ matrix after heating the substrate, and the mechanical properties and Young's modulus of HAp-coated TNTZ are improved, HAp-coated TNTZ maintains excellent mechanical biocompatibility. The formability of HAp on HAp-coated TNTZ in Hank's balanced salt solution is better than that of HAp on non-coated TNTZ.
Ca-P-O films were prepared by laser CVD using Ca(dpm)2 and (C6H5O)3PO metal organic precursors. The crystal phase of Ca-P-O films changed depending on deposition temperature (Tdep), total pressure (Ptot), laser power (PL) and molar ratio of Ca to P (RCa/p). β-TCP films in a single phase were obtained in a P-rich and high 7dep region, while HAp films in a single phase were obtained in a Ca-rich and low Tdep region. The β-TCP films had a (220) orientation with an elongated and angular roof-shaped surface texture, whereas HAp films had a (300) orientation with a granular surface texture. Both the β-TCP film and the HAp film had a dense cross section. The Ca-P-O films were immersed in a Hanks' solution for 6 h to 7 d. Particle-shaped precipitates were observed on the β-TCP and HAp films after 3 d immersion. Needle-shaped precipitates covered the whole surface of HAp film after 7d immersion.
There is an increasing need for bone repair materials for skeletal reconstruction, due to the prevalence of diseases such as osteoporosis and to the growing number of aged and overweight people Worldwide. Although used widely, there are limitations with autograft and allograft, including issues of supply and effectiveness, respectively. This has led to the need for more suitable synthetic biomaterials to replace natural bone, which can be nearly inert or bioactive. This review aims to discuss bioactive implants, coatings and scaffolds made of ceramics, glasses, glass-ceramics and composites. These are able to form a chemical interfacial bond with tissue and can be resorbable or non-resorbable.
Hydroxyapatite from two sources was electrophoretically deposited onto flat titanium plate material. Depending upon the deposition conditions various changes in the structure of the ceramic were identified. A well-adhering Ti-P compound was present at the interface. Hydroxyapatite oxygenated to various degrees and tetracalcium phosphate were reproducibly formed in the coating.
A mechanical and histological evaluation of uncoated and hydroxylapatite-coated titanium implant materials was performed in this study. Mechanical push-out testing results indicated that the hydroxylapatite-coated implants exhibited significantly greater values of maximum interface shear strength and interface shear stiffness than the uncoated implants. Hydroxylapatite-coated implants demonstrated mineralization of bone directly onto the hydroxylapatite surface. The uncoated CP titanium implants showed a predominantly fibrous tissue interface, with only isolated instances of direct implant-bone apposition. An appropriate surface macrotexture, such as the one investigated, may be required to prevent the hydroxylapatite coating from being pulled off of the substrate by applied loads. The use of hydroxylapatite coatings can significantly enhance implant fixation by direct bone ingrowth or apposition by providing a mechanism for establishing considerable attachment strength shortly after implantation.
Permanent and bioresorbable hard tissue implant materials composed of calcium phosphate ceramics are currently under extensive investigation. In addition to being unusually well-tolerated, both porous and dense forms of these materials have demonstrated the ability to become chemically bonded to bone via natural-appearing bone cementing mechanisms. The results of animal and clinical studies indicate that these materials may find use as bone graft substitutes or extenders.