Papers by Keyword: Octacalcium Phosphate

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Authors: Julietta V. Rau, Marco Fosca, Vladimir S. Komlev
Abstract: In situ monitoring of structural changes, taking place upon calcium phosphate bone cements hardening process was carried out by means of the Energy Dispersive X-Ray Diffraction method. Two different cement systems were studied, one of them based on the octacalcium phosphate and another - on the dicalcium phosphate dehydrate. Both systems contained natural biopolymer chitosan and were soaked in Simulated Body Fluid. The obtained experimental results evidence that during the hardening of the cement containing octacalcium phosphate its partial transformation into hydroxyapatite takes place, whereas no significant changes were detected during the hardening process of cement containing the dicalcium phosphate dehydrate.
Authors: M. Dutour Sikirić, Rene Elkaim, S. Lamolle, H.J. Ronold, S.P. Lyngstadass, Helga Füredi-Milhofer, F. Cuisinier
Abstract: Biological mineralization proceeds within an organic matrix and is induced and controlled by extracellular, highly acidic matrix macromolecules. Our group has recently prepared organic-inorganic nanocomposite coatings by a strategy that closely mimics these processes. The strategy involves depositing a matrix of polyelectrolyte multilayers (PE MLs), alternating with layers of amorphous calcium phosphate (ACP) particles, then "in situ" growing nanosized apatite crystals within that matrix [1, 2]. Here we describe the results of biological "in vitro" and "in vivo" testing of these materials.
Authors: M. Dutour Sikirić, Csilla Gergely, F. Cuisinier, Helga Füredi-Milhofer
Abstract: In the production of artificial bone and tooth implants, coating of the surfaces of hard, but bioinert materials (metals, polymers) with calcium phosphate crystals has been used to improve bioactivity and facilitate osteointegration. Recently low temperature methods, involving precipitation from aqueous solutions (biomimetic precipitation) including coprecipitation of specific organic macromolecules (growth hormones, enzymes, proteins) have been developed. In this paper an alternative approach is presented, which consists in first laying down a matrix consisting of polyelectrolyte multilayers (PE MLs) alternating with layers of amorphous calcium phosphate (ACP) particles and subsequently growing calcium phosphate crystals upon/within the multilayers. This attractive approach leads to the formation of a new class of true organic-inorganic nanocomposite coatings. In a previous communication we have shown preliminary results, which point to the feasibility of this approach [1]. Here we describe in detail the design, synthesis and characteristics of the thus obtained nanocomposite coatings.
Authors: Yoshitomo Honda, Shinji Kamakura, Takashi Kumagai, Osamu Suzuki
Abstract: Bone regeneration by calcium phosphates has been known to be intricately dependent on material properties or implanted milieu of host animals, such as site and species. Critical sized calvarial defects of mouse were recently used as the model for investigating bone regeneration ability and the mechanisms. The purpose of the present study is to investigate whether the critical sized mouse calvarial defects can be utilized to examine bone regeneration with synthetic octacalcium phosphate (OCP). OCP , prepared by wet synthesis methods, was sieved 0.3 ~ 0.5 mm in diameter and used for the animal experiment. At 14 days after surgery, histological examination showed that implantation of OCP grafted defects significantly enhanced bone formation compared with the control defect. OCP tended to convert to hydroxyapatite with time. The tartrate-resistant acid phosphatase (TRAP) positive osteoclastic cells were observed around the OCP particles. The results suggest that the mouse critical sized calvarial bone defects are useful model to investigate the bone formation by the OCP implantation.
Authors: Racquel Z. LeGeros, John P. LeGeros
Authors: Helga Füredi-Milhofer, P. Bar-Yosef Ofir, M. Sikirić, N. Garti
Authors: Osamu Suzuki, Shinji Kamakura, Takahisa Anada
Abstract: The present study was designed to investigate the mechanism of in vivo conversion from synthetic octacalcium phosphate (OCP) into hydroxyapatite (HA) at ultrastructural level, where the implanted OCP is enhancing bone regeneration in mouse calvarial bone defect. OCP granules were implanted into the subperiosteal area of the calvaria of 7-week-old BALB/c mice for 3 weeks. Transmission electron microscopy of undecalcified frontal sections, obtained from the acrylic resin-embedded skull specimens showed that the bone crystals in newly formed bone directly bonded to the OCP particles implanted. The morphological characteristic of original plate-like OCP particles was remained unchanged even after the implantation, whereas a number of de novo nano-particles were also directly formed onto the plate-like OCP particles. Some of OCP particles were linked with other OCP particles through these nano-particles. The results suggest that the OCP-apatite conversion, involving the enhanced bone regeneration, advances via topotaxial conversion without changing the original OCP morphology, accompanied by solution-mediated de novo nano-apatite formation, in the vicinity of the implanted OCP particles.
Authors: Kentaro Suzuki, Takahisa Anada, Yoshitomo Honda, Koshi N. Kishimoto, Naohisa Miyatake, Masami Hosaka, Hideki Imaizumi, Eiji Itoi, Osamu Suzuki
Abstract: We have previously shown that synthetic octacalcium phosphate (OCP) displays highly osteoconductive and biodegradable characteristics. However, OCP cannot be sintered without thermal decomposition due to the existence of water molecules in the structure. The acquisition of the moldability and the improvement of the handling property in this material are subjects for the clinical use. In the present study, we prepared OCP complex with hyaluronic acid (Hya) that could be used in the injectable form and further examined the bone tissue reaction to cortical bone by placing the complex directly on an 8-weeks-old ICR mouse calvaria in comparison with the placement of OCP granules only. The granule form of OCP (between 300 to 500 μm in diameter) was mixed with sodium hyaluronic acid with molecular weights 90 x 104. The complex revealed an injectable characteristic if it was utilized in a syringe. After polytetrafluoroethylen ring was mounted on mouse calvaria, the inner space of the ring was filled with the complex and left the complex as it is for 6 weeks. Histological examination using the decalcified specimens indicated that the OCP/Hya complex exhibited greater bone formation than OCP granules only group within the ring at 6 weeks. The results suggested that the OCP/Hya complex could be used as an injectable and osteoconductive bone substitute material in many clinical situations.
Authors: Christiane Xavier Resende, Gustavo Mendes Platt, Jean Dille, Ivan Napoleão Bastos, Gloria Dulce de Almeida Soares
Abstract: In this work, a solution able to precipitate calcium phosphate in titanium samples was studied. At first, a thermodynamic analysis of the proposed solution was conducted using a computational simulator that considers most of chemical reactions and evaluates parameters such as activity of species. After this procedure, experimental tests were performed in order to confirm this precipitation. With the use of TRIS at concentration of 50mM, the deposits were basically composed of octacalcium phosphate, as confirmed in some characterization techniques. The deposit presents a thickness of approximately 15μm after a 7-day exposure in the designed solution.
Authors: Shinji Kamakura, Kazuo Sasaki, Yoshitomo Honda, Taisuke Masuda, Takahisa Anada, Tadashi Kawai, Aritsune Matsui, Keiko Matsui, Seishi Echigo, Osamu Suzuki
Abstract: Our previous studies showed that synthetic octacalcium phosphate (OCP) enhances bone regeneration more than hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP). Also, a synthetic bone substitute constructed of synthetic octacalcium phosphate (OCP) and porcine atelocollagen sponge (OCP/Col) showed stable bone regeneration. The present study was designed to investigate the difference of bone regeneration by OCP/Col and other calcium phosphate-collagen composites. OCP/Col, β-TCP$-collagen% composite (β-TCP/Col), or HA$-collagen% composite (HA/Col) sponge was prepared from pepsin-digested atelocollagen isolated from the porcine dermis and OCP, β-TCP, or HA granules, respectively. A standardized critical-sized defect was made in the rat calvarium, and various calcium phosphate-collagen composites were implanted into the defect. The rats were fixed at four weeks after implantation and radiographic and histological examinations were performed by undecalcified cross sections of implants. Radiographic examination showed that uniform radiopaque masses were observed in the created defects treated with OCP/Col, whereas granulous and foggy radiopacity was observed in β-TCP/Col and HA/Col. Histological examination showed that newly formed bone was observed in the reticulum of OCP/Col and around the implanted OCP. The regenerated bone by β-TCP/Col or HA/Col seemed to be less than that by OCP/Col and would not to be nucleated by the granules of β-TCP or HA. The present study indicated that bone regeneration by OCP/Col was different from those of β-TCP/Col and HA/Col. Application of OCP/Col would be expected for clinical use in the future.
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