Bioceramics 17

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Authors: J. Miguel Oliveira, Isabel B. Leonor, Rui L. Reis
Abstract: The aim of this research was to develop a new methodology to obtain bioactive coatings on bioinert and biodegradable polymers that are not intrinsically bioactive. In this study, three types of materials were used as substrates: (i) high molecular weight polyethylene (HMWPE) and two different types of starch based blends (ii) starch/ethylene vinyl alcohol blends, SEVA-C, and (iii)starch/cellulose acetate blends, SCA. These materials were obtained by injection moulding and by extrusion with blowing agents in order to obtain compact/porous 3D architectures. Three types of baths were developed in order to produce the newly proposed auto-catalytic Ca-P coatings: (i)alkaline, (ii) acid, and (iii) oxidant bath. The obtained results indicated that it was possible to coat the materials surfaces with calcium phosphate (Ca-P) layer with only 60 min of immersion in the different types of auto-catalytic solutions. These innovative auto-catalytic electroless route allows for the production of an adherent bioactive film on the polymeric surfaces. Furthermore, it was possible observe by SEM/EDS the clear bioactive nature of the Ca-P coatings after different immersion periods, in a simulated body fluid (SBF).
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Authors: Hyun Bin Kim, Yogesh K. Vohra, Patrick J. Louis, William R. Lacefield, Jack E. Lemons, Renato P. Camata
Abstract: We report results of in-vitro and in-vivo studies on biphasic thin film coatings of hydroxyapatite/tetracalcium phosphate produced by pulsed laser deposition using ablation targets of crystalline hydroxyapatite. Changes in coating phase composition during in-vitro dissolution experiments were monitored by x-ray diffraction. Scanning electron microscopy was used to assess variations in surface morphology. In-vivo experiments involving the insertion of coated metallic implants in the proximal tibia and distal femur of New Zealand White Rabbits were carried out. Histomorphometric studies on implant samples after surgical extraction show that biphasic coatings produced may lead to enhanced osteointegration compared to pure hydroxyapatite coatings.
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Authors: Y. Cao, Li Ping Wang, Bo Zhang, Qiang Lin, Xu Dong Li, C.Y. Bao, Ji Yong Chen, L. Yang, Xing Dong Zhang
Abstract: The three different structures of titanium oxide film were prepared: (1) The commercial pure titanium was treated with heating in air at 700°C for half hour and gotten a dense rutile film on titanium (HS Samples); (2) The commercial pure titanium was treated by chemically treating and gotten a layer of amorphous titania gel on the Ti surface (TS Samples); (3) After chemically treating, the samples were heated in air at 700 °C for half hour, and gotten nano-particles coalesced microporous titanium oxide (rutile) film on titanium surface (XS sample). The dense rutile and amorphous titania gel did not induce apatite formation on their surfaces in SBF solution for 48 hours, whereas the nano-particles coalesced microporous rutile structure induced apatite formation on their surfaces. Mechanical test and histological examination were investigated after the samples implanted in dogs limbs for 3 months. The results of push-out test are 12.96, 29.48 and 35.83 MPa respectively for HS, TS and XS sample. Histological results showed that TS sample and XS sample contacted the bone directly, without any intervening fibrous tissue, and there was a fibrous tissue layer between the bone and HS samples.
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Authors: Juan C. Hermida, Shantanu Patil, Fred Dimaano, Monica Hawkins, Clifford W. Colwell, Darryl D. D'Lima
Abstract: Implants with a highly porous coating of Tritanium Dimensionalized MetalÔ have the advantage of simulating the trabecular structure of bone to provide maximum available porous space for bone ingrowth. Plasma-sprayed hydroxyapatite coatings work well on non-porous substrates but do not coat the inner surfaces of open-porous substrates. Solution deposition can produce a consistent bioceramic coating of precise thickness on porous surfaces. This report compares bone response to a highly porous titanium surface with a solution deposited coating of hydroxyapatite. Ti6AL4V rods were implanted bilaterally in the intramedullary canals of 40 rabbit femurs. The implants had a 1.5 mm CPTi coating, which was >65% porous with pore sizes of 250-400 microns. (Tritanium Dimensionalized MetalÔ). Twenty implants (T-HA) were coated with hydroxyapatite by a solution deposition method (Peri-ApatiteÒ). The other 20 implants (T) had no hydroxyapatite coating. Implants were provided with a final diameter of 5 mm and length of 23 mm (Howmedica Osteonics, Mahwah, NJ). Rabbit femurs were harvested at 6 and 12 weeks after surgery sectioned at two levels: in the diaphyseal and metaphyseal portion of the femoral canal. Scanning electron images (SEM) in backscattered mode were digitally captured. Osseointegration was measured by automated computerized histomorphometry of the SEM images. Mean bone ingrowth at both time points was significantly different between hydroxyapatite-coated and non-hydroxyapatite coated implants (p<0.01). The hydroxyapatite coating had a significant benefit on the bone growth into porous titanium surfaces. Bone ingrowth was substantially higher at all time points in the hydroxyapatite-coated surface relative to the uncoated surface and in both diaphyseal and metaphyseal cross-section levels. The finding of a higher percentage of bone growth deeper in the pores of the surface is encouraging. This signifies that the solution deposited Peri-Apatite coating is capable of depositing a bioactive coat of hydroxyapatite in the depths of the porous surface. This depth of penetration is not achievable by conventional plasma-sprayed deposition of hydroxyapatite. Implants with a Tritanium Dimensionalized MetalÔ surface and a solution deposited Peri-Apatite coating have the potential to develop into attractive alternatives for noncemented total hip arthroplasty.
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Authors: Jae Hyup Lee, Hyun Seung Ryu, Dong Soo Lee, Kug Sun Hong, Bong-Soon Chang, Choon Ki Lee
Abstract: The purpose of this study is to compare the osseointegration of calcium pyrophosphate(CPP) coated screws with uncoated screws. CPP coating was prepared and coated by dipping method. CPP coated and uncoated screws were inserted into the mongrel dogs. The insertion torques, radiographs, histology, histomorphometric analysis, and extraction torques were evaluated at 2, 4, and 8 weeks after surgery. The insertion torque was not different between CPP coated and uncoated screws. The extraction torques of CPP coated screws at 2, 4, and 8 weeks(5.45±2.05, 7.62±1.51 and 6.60±2.80 cNM) were significantly higher than their insertion torques(2.74±1.13, 2.98±0.70, and 2.18±1.34 cNM)(p<0.0001, <0.0001 and 0.0005 respectively) and significantly higher than the extraction torques of uncoated screws(1.14±0.470, 2.57±1.36, and 3.18 ±0.499 cNM). The percentages of direct bone-screw contact of CPP coated screws were statistically higher than those of uncoated screws at 2, 4, and 8 weeks. These results suggest that CPP coating may improve the clinical results by allowing early motion exercises and early weight bearing.
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Authors: Adriana Bigi, E. Boanini, Barbara Bracci, A. Facchini, Silvia Panzavolta, F. Segatti, L. Sturba
Abstract: We employed a slightly supersaturated solution (Ca/P) with an ionic composition simpler than that of simulated body fluid (SBF) to obtain a fast biomimetic coating on Ti6Al4V substrates. The results of thin film X-ray diffraction, FTIR, SEM, TEM-ED investigations indicate that hydroxyapatite (HA) nanocrystals are laid down in a few hours on the susbstrates. The amount of deposition increases with the immersion time. Furthermore, the thin layer of HA deposited after 3 h soaking in Ca/P solution acts as a catalyst for the further deposition of apatite from SBF.
223
Authors: Ayako Oyane, Masaki Uchida, Yousuke Ishihara, Atsuo Ito
Abstract: Mechanism of formation of a laminin-apatite composite layer on the surface of an ethylene-vinyl alcohol copolymer (EVOH) using a liquid phase coating process was investigated by transmission electron microscopy (TEM). In this coating process, an EVOH substrate is alternately dipped in calcium and phosphate solutions, and then immersed in a laminin-containing calcium phosphate (LCP) solution. From the results obtained by the present study, formation of the laminin-apatite composite layer on EVOH is likely to proceed via the following events. By the alternate dipping process, particulate amorphous calcium phosphate, which is a precursor of apatite, was deposited onto the EVOH surface. When the specimen was subsequently immersed in the LCP solution, the amorphous calcium phosphate on the specimen transformed itself into needle-like apatite crystal, and then grew into a layer. During this process, laminin molecules contained in the LCP solution were incorporated into a matrix of the apatite crystals to produce a laminin-apatite composite layer on the EVOH surface.
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Authors: Bo Feng, Jie Weng, Shao Xing Qu, Xing Dong Zhang
Abstract: A microporous apatite coating was fabricated by a heat-oxidation and chemical routine. The morphology, composition and structure were characterized by scanning electron microscopy with X-ray energy dispersion spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The components of the coating were predominantly apatite, next tri-calcium phosphate and octa-calcium phosphate. The pore size ranged from 1µm to5µm. The thickness of the coating was about 6µm ~ 10µm. The microporous coating was Ca-deficient carbonate apatite.
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Authors: Yan Yonggang, Joop G.C. Wolke, Yu Bao Li, John A. Jansen
Abstract: RF magnetron sputtering was used to produce calcium phosphate coatings on titanium substrates. The as-sputtered amorphous calcium phosphate (CaP) coatings were subjected to a rapid heating with infrared irradiation and subsequent heating in an autoclave. XRD analyses showed that infrared radiation of the amorphous coatings changed respectively into a crystalline apatite- and a β-pyrophosphate structure. Heating in the autoclave showed for the amorphous CaP coating at 80°C for 2 days and 8 hours at 140°C no change in structure and the formation of a crystalline apatite structure respectively. The amorphous pyrophosphate(Pyro) coating altered during the autoclave treatment for 2days at 80°C into a monetite phase, while at 140°C an apatite structure was formed. SEM analyses demonstrated that after the different heat-treatments several coating morphologies were obtained. Infrared radiation had no effect on the coating morphology. The autoclave-treated coatings showed the formation of a calcium phosphate precipitate. CaP and Pyro coatings induced a morphologically different precipitate. On the CaP coating, spherocrystallites crystals were formed and the Pyro coatings showed the formation of needle like crystals. EDS analyses indicated for the autoclave heat treated Pyro coating an increase of the Ca/P ratio from 0.8 to 1.7.
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Authors: Dora A. Cortés-Hernández, A. Medina Ramírez, José C. Escobedo-Bocardo, M.A. López, J.M. Almanza-Robles
Abstract: Wollastonite ceramics was used in a biomimetic method to promote apatite formation on a Co-Cr-Mo alloy (ASTM F-75). The metallic samples were initially chemically treated in a 5M NaOH aqueous solution. The treated samples were immersed for 7 days in SBF on a bed of wollastonite and then immersed 7 or 14 days in 1.5SBF. For comparative purposes no wollastonite was used during the first 7 days in some tests. A homogeneous bonelike apatite layer was formed on the samples immersed in SBF on the wollastonite bed. The morphology and the Ca/P ratio of the layer were closely similar to those observed on the existing bioactive systems. A thinner homogeneous bonelike apatite layer was formed on the samples immersed in SBF and 1.5SBF without using wollastonite. However, the morphology and the Ca/P ratio of this layer differs slightly to that observed on the existing bioactive systems. The immersion of the samples during the first days in SBF on a wollastonite bed improves significantly the quality and thickness of the bonelike apatite layer.
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