Biodegradation of Synthetic Biphasic Calcium Phosphate and Biological Calcified Substratum by Cells of Hemopoietic Origin

Different types of osteoclastic cells (authentic osteoclasit from human giant cell tumor and bone marrow of newborn rats; newly-formed osteoclasts from adult rat bone marrow), giant multinucleated cells and macrophages were studied for their effect on synthetic and natural mineralized substrata. Biphasic calcium phosphate ceramic consisted of hydroxyapatite and beta tricalcium phosphate was chosen for in vitro experiments, and dentine served as a positive control for cell resorbing activity . Our results show the limited capacity of authentic and newly-formed osteoclasts to resorb synthetic ceramic as compared to that of natural substrata. In vitro cell-mediated biodegradation included also modifications of the synthetic substratum surface caused presumably by phagocytosis of the material

Scaffolds with a standardized macro-architecture fabricated from several calcium phosphate ceramics using an indirect rapid prototyping technique

Calcium phosphate ceramics, commonly applied as bone graft substitutes, are a natural choice of scaffolding material for bone tissue engineering. Evidence shows that the chemical composition, macroporosity and microporosity of these ceramics influences their behavior as bone graft substitutes and bone tissue engineering scaffolds but little has been done to optimize these parameters. One method of optimization is to place focus on a particular parameter by normalizing the influence, as much as possible, of confounding parameters. This is difficult to accomplish with traditional fabrication techniques. In this study we describe a design based rapid prototyping method of manufacturing scaffolds with virtually identical macroporous architectures from different calcium phosphate ceramic compositions. Beta-tricalcium phosphate, hydroxyapatite (at two sintering temperatures) and biphasic calcium phosphate scaffolds were manufactured. The macro- and micro-architectures of the scaffolds were characterized as well as the influence of the manufacturing method on the chemistries of the calcium phosphate compositions. The structural characteristics of the resulting scaffolds were remarkably similar. The manufacturing process had little influence on the composition of the materials except for the consistent but small addition of, or increase in, a beta-tricalcium phosphate phase. Among other applications, scaffolds produced by the method described provide a means of examining the influence of different calcium phosphate compositions while confidently excluding the influence of the macroporous structure of the scaffolds

Is bisphosphonate therapy compromised by the emergence of adverse bone disorders?

Bisphosphonates (BPs) are the preferred class of antiresorptive agents used for the treatment of osteoporosis and bone metastases. Recently, an increasing number of clinical reports concerning osteonecrosis of the jaw and atypical fractures have suggested a link between prolonged use of BPs and these adverse bone events, which are exceptionally difficult to treat. Even though these side effects were mainly observed in patients with metastases, osteoporotic patients might become increasingly affected by these conditions with the increasing use of injectable BPs. Could these severe adverse bone events compromise the use of BPs? The development of these unfavorable conditions as a consequence of oversuppression of bone resorption could raise concern regarding the use of therapeutic strategies involving antiresorptive drugs

Controlling the biological function of calcium phosphate bone substitutes with drugs

There is a growing interest in bone tissue engineering for bone repair after traumatic, surgical or pathological injury, such as osteolytic tumor or osteoporosis. In this regard, calcium phosphate (Cap) bone substitutes have been used extensively as bone-targeting drug-delivery systems. This localized approach improves the osteogenic potential of bone substitutes by delivering bone growth factors, thus extending their biofunctionality to any pathological context, including infection, irradiation, tumor and osteoporosis. This review briefly describes the physical and chemical processes implicated in the preparation of drug-delivering CaPs. It also describes the impact of these processes on the intrinsic properties of CaPs, especially in terms of the drug-release profile. In addition, this review focuses on the potential influence of drugs on the resorption rate of CaPs. Interestingly, by modulating the resorption parameters of CaP biomaterials, it should be possible to control the release of bone-stimulating ions, such as inorganic phosphate, in the vicinity of bone cells. Finally, recent in vitro and in vivo evaluations are extensively reported. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Adaptive crystal formation in normal and pathological calcifications in synthetic calcium phosphate and related biomaterials

International audienc

Biphasic calcium phosphates: Influence of three synthesis parameters on the HA/beta-TCP ratio

Hydroxyapatite (HA) contents measurements were conducted on eight biphasic calcium phosphate (BCP) samples obtained by sintering calcium-deficient apatite formed previously by hydrolyzing a dicalcium phosphate dihydrate (DCPD) powder. We evaluated the influences and interactions of three synthesis factors: alkalinity, process duration, and concentration of the water suspension in DCPD. Those parameters were varied simultaneously between two limit levels. Experiments used a factorial design method (FDM) allowing optimization of the number of samples as well as statistical analysis of results. FDM showed that HA content, in a defined experimental area, can be described by a first-order polynomial equation in which the initial alcalinity and the DCPD/water ratio are the major influences. Experiment prove that pH measured at the end of the hydrolysis was predictive of the HA content in the final BCP. This study leads up to an isoresponse line diagram which will allow the synthesis of some BCP with fitted HA/beta-tricalcium phosphate ratios. (C) 2000 John Wiley & Sons, Inc

Controlling the biological function of calcium phosphate bone substitutes with drugs

There is a growing interest in bone tissue engineering for bone repair after traumatic, surgical or pathological injury, such as osteolytic tumor or osteoporosis. In this regard, calcium phosphate (Cap) bone substitutes have been used extensively as bone-targeting drug-delivery systems. This localized approach improves the osteogenic potential of bone substitutes by delivering bone growth factors, thus extending their biofunctionality to any pathological context, including infection, irradiation, tumor and osteoporosis. This review briefly describes the physical and chemical processes implicated in the preparation of drug-delivering CaPs. It also describes the impact of these processes on the intrinsic properties of CaPs, especially in terms of the drug-release profile. In addition, this review focuses on the potential influence of drugs on the resorption rate of CaPs. Interestingly, by modulating the resorption parameters of CaP biomaterials, it should be possible to control the release of bone-stimulating ions, such as inorganic phosphate, in the vicinity of bone cells. Finally, recent in vitro and in vivo evaluations are extensively reported. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Nuclear magnetic resonance spectroscopy of bone substitutes

9th European Meeting on Injectable Bone and Joint Substitution Materials, LAUSANNE, SWITZERLAND, MAR 01-02, 1999Calcium phosphate bone replacement biomaterials are widely used in different applications. Structure, composition, and organization are, before implantation, analyzed with different methods. Among them, X-ray diffraction is a recognized test. As bioresorption produces more amorphous material, the process is observed and quantified via scanning electron microscopy, Comparatively high-resolution P-31 solid-state nuclear magnetic resonance spectroscopy is able to analyze raw ceramics composition and to estimate osteoformation, (Bone 25:103S-105S; 1999) (C) 1999 by Elsevier Science Inc. All rights reserved