Papers by Keyword: Calcium Phosphate Cement (CPC)

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Authors: A. Rosenberg, Aliassghar Tofighi, N. Camacho, J. Chang
Abstract: A new class of osteoconductive and osteoinductive combination biomaterials composed of calcium phosphate cement (CPC), demineralized bone matrix (DBM) and a water-soluble viscosity modifier were prepared and characterized in-vitro and in-vivo. In previous studies, a range of combinations formulations were tested in order to compare their performance characteristic. In-vitro characterization results show that the mechanical strength is decreased when the amount of DBM increases. However, DBM does not affect the CPC’s ability to set hard and convert to nanocrystalline apatitic calcium phosphate, which shares the chemical structure of natural bone as seen in x-ray diffraction. It is known that the DBM alone is osteoinductive. In-vivo osteoinductivity testing of the formulations in an intramuscular, athymic rat model demonstrated that the combination material is also osteoinductive. Two formulations were chosen for in-vivo efficacy testing based on the results of in-vitro and in-vivo characterization. These formulations were studied using rabbit critical-sized femoral core defect model. The formulations were composed of DBM with particle sizes of 250 to 710 μm, carboxymethyl-cellulose (CMC) as the viscosity modifier and weight percent compositions of 50% DBM/ 45% CPC/ 5% CMC and 60% DBM/ 30% CPC/ 10% CMC. Bone integration and healing was graded at 6, 12, and 24 weeks. The two formulations were compared to the gold standard autograft at 12 weeks and to an empty defect as the negative control at 24 weeks. Based on micro-computed topography (μCT), both formulations allowed for continuity of bone throughout the defect region at all time points. No differences in dense area fraction were seen between two formulations at 6 weeks (p = 0.8661). There was no significant statistical difference between the two formulations and autograft at 12 weeks (p = 0.2467). At 24 weeks, both formulations had significantly higher dense area fractions than empty controls (p = 0.0001). Histologically, the biology of the treatment areas appeared to have returned to normal by 24 weeks with CPC appearing to be the principal osteogenic inducer. In conclusion, these combinations of CPC and DBM offers significant advantages (handling, mechanical properties and osteoinductivity) over current DBM products and can be an effective alternative to autograft in healing of bone defects.
Authors: Nader Nezafati, F. Moztarzadeh, Masoud Mozafari
Abstract: Basic drawbacks of calcium phosphate cements (CPCs) are the brittleness and low strength behavior which prohibit their use in many stress-bearing locations, unsupported defects, or reconstruction of thin bones. Recently, to solve these problems, researchers investigated the incorporation of fibers into CPCs to improve their strength. In the present study, various amounts of a highly bioactive glass fiber were incorporated into calcium phosphate bone cement. The obtained results showed that the compressive strength of the set cements without any fibers optimally increased by further addition of the fiber phase. Also, both the work-of-fracture and elastic modulus of the cement were considerably increased after applying the fibers in the cement composition. Herein, with the aim of using the reinforced-CPC as appropriate bone filler, the prepared sample was evaluated in vitro using simulated body fluid (SBF) and osteoblast cells. The samples showed significant enhancement in bioactivity within few days of immersion in SBF solution. Also, in vitro experiments with osteoblast cells indicated an appropriate penetration of the cells, and also the continuous increase in cell aggregation on the samples during the incubation time demonstrated the ability of the reinforced-CPC to support cell growth. Therefore, we concluded that this filler and strong reinforced-CPC may be beneficial to be used as bone fillers in surgical sites that are not freely accessible by open surgery or when using minimally invasive techniques.
Authors: M. Motisuke, R. García Carrodeguas, Cecília A.C. Zavaglia
Abstract: On this study the influence of silicon dopping on the properties of the final calcium phosphate cement were analysed and compared to the ones of the conventional Si and Mg-free α-TCP cement. In spite of silicon doping, Si-α-TCP calcination temperature (1400°C) was higher than the one used for conventional α-TCP (1300°C) as a result of Mg contamination on the commercial precursor used on the Si-α-TCP synthesis. Because of the high temperature used, Si-α-TCP sample was difficult to mill. Even after 1 week milling, the particle size achieved was 12µm while Si-free α-TCP reached 7.7µm. Consequently, the reactivity of both powders was different. In conclusion, the properties of Si-α-TCP cement were not satisfactory for clinical application. In order to do it so, it is essential to enhance the powder reactivity by reducing Mg contamination, lowering the sintering temperature and reducing the particle size to, then, achieve the desired reactivity and compressive strength.
Authors: G. Georgescu, J.L. Lacout, M. Frèche
Authors: E.F. Burguera, Francisco Guitián, Laurence C. Chow
Abstract: The progression of the setting reaction of a tetracalcium phosphate (TTCP) –dicalcium phosphate dihydrate (DCPD) rapid setting cement was investigated as a function of time. Compressive strength and extent of conversion to hydroxyapatite (HA) were obtained at different incubation times. The results indicated a rapid development of both strength and HA conversion in the early stages of the reaction, which slowed down after 4 h, presumably as a result of HA formation on the surface of the reactants. This hypothesis was supported by scanning electron microscopy examination of cement fracture surfaces.
Authors: Liam M. Grover, Uwe Gbureck, David Farrar, J.E. Barralet
Abstract: In this study, we have shown that by incorporating pyrophosphoric acid into a brushite cement system, it is possible to produce a cement that exhibits adhesive tensile strengths with cortical bone, alumina, sintered hydroxyapatite and 316L stainless steel of 700 kPa. To our knowledge, this is the first report of a calcium phosphate cement formulation that exhibits such adhesive properties without the addition of an organic additive. The production of a bond between medical prostheses and bone may further widen the field of application of calcium phosphate cements, additionally the adhesive nature of the calcium phosphate cement may be a desirable ‘handling characteristic’ during reconstructive surgery.
Authors: J. Friberg, E. Fernández, S. Sarda, M. Nilsson, M.P. Ginebra, S. Martínez, Josep A. Planell
Authors: Masashi Mukaida, Masashi Neo, Y. Mizuta, Yasushi Ikeda, Takashi Nakamura
Abstract: High resolution X-ray CT is a powerful means for analyzing comprehensive ceramic biomaterials in a living body. The benefit of this method is that morphological and volume changes of implant materials can be evaluated without retrieve of the implant in an animal body, resulting in no killing of the animals and long term evaluation even more than one year. In this study, in situ techniques for observation of calcium phosphate cement is developed. Calcium phosphate cement (CPC) was implanted into a femur and under skin of a rat. The volume and morphology change of the CPC were repeatedly measured using the same rat for more than 12 months. The 3-dimentional (3-D) structures of the CPC were imaged and reconstructed from hundreds of 2-D cross sectional CT images, which were obtained at one time by a 360 degree rotation of the sample. The structure of the CPC was visualized with 3-D, and the volume were numerically analyzed by using a 3-D structure analyzing computer software, which enabled two-value processing and estimation of the quantities of the CPC. Moreover some of the CPC samples were retrieved and were observed by SEM. In the results, the surface of the calcium phosphate cement changed from smooth to jagged with increasing implanted period. The CPC volume implanted into bone was gradually decreased with increasing implanted period. The volume loss was 8 % after 12 months. The CPC volume under skin after 1 month increased by 7 %. After that the volume gradually decreased in next 3 months. Absorption process of CPC in a rat will be discussed.
Authors: Y. Miyamoto, T. Toh, Tetsuya Yuasa, M. Takechi, Y. Momota, M. Nagayama, Ishikawa Kunio, Kiyoshi Suzuki
Authors: Daniela Jörn, Renate Gildenhaar, Georg Berger, Michael Stiller, Christine Knabe
Abstract: The setting behaviour, the compressive strength and the porosity of four calcium alkali orthophosphate cements were examined under laboratory conditions (dry) and under conditions similar to those during clinical application (37°C, contact with body fluid). The results showed an increase of the setting times when specimens were covered with simulated body fluid. Especially, the final setting time (FHZ) was significantly higher for three of the four cements. Furthermore, when specimens were stored in SBF for 16h, an extensive decrease of the compressive strength was noted. The porosity was more than twice as high after 16h in SBF and this may be the cause for the great decrease of the compressive strength.
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