Papers by Keyword: Calcium Phosphate Cement (CPC)

Abstract: Due to their insufficient mechanical stability and brittle nature, calcium phosphate cements (CPCs) have not been used for the treatment of vertebral fractures. Mechanical stability of human bone is provided by a complex interaction of type I collagen fibres and hydroxyapatite crystals. In the present study, fibre reinforcement of an apatitic calcium phosphate prepared at different liquid/powder ratio (LPR) was investigated. Different lengths of type I collagen fibres sourced from bovine Achilles tendon were used. Compressive strength and fracture behaviour were examined. Fibre addition of up to 5 wt.% had a significant influence on the compressive properties of the CPC. The mechanism of fibre reinforcement appeared to be crack bridging. Setting time and injectability of the CPC with fibre reinforcement was also investigated and decreased with fibre volume fraction. Increasing the LPR, improved the injectability and delayed the setting reaction. However, the compressive properties of the hardened cement were reduced as a consequence.

Abstract: An application of calcium phosphates is as bone cements, among which the system based on alpha-tricalcium phosphate (α-TCP) exhibits excellent properties. The aim of this study is to analyze pH evolution and cytotoxicity of α-TCP cement with three different additives. Changes on the pH were measured at intervals of 12h during seven days. But initial measurements were executed at each 15 minutes. Indirect cytotoxicity test was performed according to ISO (10993-5, 1992) employing CHO-k1 cells and RPMI 1640 as culture medium. It was used a colorimetric method which uses the tetrazolium compound. The additives used on the liquid phase were disodium hydrogen phosphate (Na₂HPO₄) and/or citric acid (C₆H₈O₇) and/or tannic acid (C₇₆H₅₂O₄₆). The results indicate that the cement without additives does not have requirements to be applied like bone cement, while the other cements composition exhibit different responses in the pH and the cytotoxicity test. In conclusion, due to the presence of additives it was possible to control pH evolution during setting and cytotoxic response. However, further investigation is necessary in order to determine the influence of these additives, mainly tannic acid, on the in vivo behavior of these bone cements.

Abstract: Among the calcium phosphate cements, the system based on alpha-tricalcium phosphate (α-TCP) combines several interesting properties. However, these cements have their use limited to low load applications. The main objective of this study is to evaluate the influence of three different additives on the setting reaction kinetics and mechanical strength evolution of calcium phosphate cements as a function of time. The cement was obtained by mixing α-TCP powder with four different aqueous solutions containing or not containing disodium hydrogen phosphate (Na₂HPO₄), citric acid (C₆H₈O₇) and/or tannic acid (C₇₆H₅₂O₄₆). It was observed that two cement samples, one of them containing Na₂HPO₄ and C₆H₈O₇ and another containing Na₂HPO₄ and C₇₆H₅₂O₄₆ in the liquid phase, presented faster setting reaction and higher mechanical properties. These cements are more suitable for application as bone cement.

Abstract: The first generation of synthetic bone substitute materials, hydroxyapatite (or HA), was initially investigated as a “non self-hardening” biomaterial for remodeling of bone defects. CPBCs concepts were used as a platform to initiate a second generation of injectable, self-hardening cement. The variety of CPBC’s chemical composition leads to a better understanding of their mechanism of reaction and their proposed classification: acid-base, mono-component and hydrolysable. After hydration, mixing, and full chemical reaction, these cements have the ability to precipitate different end products (e.g. HA, calcium deficient apatite, carbonated apatite, brushite, etc.). In fact, the initial idea of having higher mechanical performance (>50 MPa in compression) for a bone void filler application was abandoned and has led to a greater focus on cement fast-hardening (<15 min), higher total porosity (>60%), extended performance of injectability (8 to 22 G), fast resorbability (< 2 years) and user-friendliness for the clinicians. A new CPBC combination (cement plus additives) has particularly improved rheological and biointegrity performance. A hybrid of CPBC-DBM (Demineralized Bone Matrix) has also added an osteoinductivity performance to the initial osteoconductive CPBC.This paper will propose a comparison of the chemical composition, reaction, and performance characteristics of major commercially available CPBC products. Furthermore, it will describe today’s surgeon’s CPBC needs as bone substitute materials for different clinical applications. Finally, we will discuss what we learned so far, how we can resolve several clinical impacts & product recall, and how we believe CPBC designers can meet development challenges, and users’ specific requirements.

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.

Abstract: Due to the lack of macroporosity in current available Calcium Phosphate cement used in osteoarticular surgery, Micro and Macroporous Biphasic CaP Cement (MCPC™) was developed. The MCPC™ concept was the association of a settable and a fast resorbable matrix and a sieved fraction of microporous biphasic calcium phosphate (BCP) granules, recognized for the high osteoconductive and osteogenic properties. During the resorption of the matrix, a porous structure is created and the osteoconductive effect of the granules promotes the bone ingrowth. A goat preclinical study was realized to evaluate the efficacy of MCPC™ for C3 and C4 vertebral body filling defects during 6 months. Bone remodelling was evidenced demonstrating bone ingrowth at the expense of the cement and surrounding the residual BCP granules. Bone trabeculae were observed coming from the spongious bone to the implant site. Human vertebral body filling cases demonstrated the biocompatibility and the safety of MCPC™ for bone reconstruction. Results of this study demonstrated the importance of special combination of calcium phosphate granules in the MCPC™ to provide macroporosity and scaffolding for newly formed bone.

Abstract: Tests were performed to assess the parameters influencing the injectability of cement pastes loaded with large particles, such as porogens or drug-delivery agents. The use of non-setting model pastes permitted to demonstrate that two phase separation mechanisms occurred simultaneously, i.e. the separation between liquid and powder, known as filter-pressing phenomenon, and the separation between larger and smaller particles.

Abstract: In this study, we invesgated the mechanical properties of the rabbit femurs fixed with calcium phosphate cement (CPC). Twenty adult rabbits were randomly divided into the control group and the group treated with femur fracture artifically, then fixed with CPC. Two weeks after surgery, all rabbits were sacrificed, and femurs were removed for the three point bending test to examine the changes of mechanical parameters of the femurs. Our results showed that although the maximum tension stress of the femurs in the treatment group was smaller than the control, its crosss-sectional area became bigger, which improved the ablity of the femur to bear more loading with the maximum pressure and absorbed energy during destroy up to 83.5% and 64.3% of normal bone material strength. It indicated that it was practicable to fix the fractured femur with CPC from the biomechanical view piont.

Abstract: In this paper, calcium phosphate cement (CPC) was prepared with tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA) system as solid phase and phosphate buffered solution (PBS) as liquid phase, then silk fibroin (SF) was added into CPC to form silk fibroin/calcium phosphate composite. To study the effect of SF on the properties of composite, different mass fraction of SF was added into the composite. The surface morphology was observed by Scanning Electron Microscope. The setting time was investigated by ISO Cement Standard Consistency Instrument. The structure of the composite was studied by X-ray diffraction and infrared spectroscopy. Mechanical properties of samples were tested by Instron Universal Testing Machine. The results showed that the particles of SF could be seen obviously in the surface of all composite, and acicular crystal of hydroxyapatite (HA) was formed in the hardening body of both the composite and the pure CPC. The acicular crystal of HA derived from composite with SF appeared to be thinner. The setting times of the composites were all between 9 to 15min. Compared to pure CPC, the compressive strength and work-of-compressive of composites were all improved. The compressive strength of the composite with 1% SF increased obviously.

Abstract: The long-retention of antibiotics in Calcium Phosphate Cement (CPC) may induce the development of drug resistance. Fast-releasing CPC containing antibiotics (FRCPC) was proposed as a solution to this problem and studied in this work. The FRCPC containing different proportions of soluble component were prepared and characterized. The setting time, compressive strength, degree of the conversion, in vitro antibiotic release and fracture surface morphology of FRCPC were studied. The results showed that the setting time increased, the compressive strength decreased, the in vitro antibiotic release accelerated with increasing fraction of soluble component in FRCPC. The setting time and compressive strength of FRCPC containing 20 wt% soluble components were close to the requirements of clinical applications, and the in vitro release was completed within 7 d. These results mentioned above showed that the FRCPC with suitable proportions of soluble components may prevent the development of drug resistance and may find applications in clinics.