Bone substitutes

The in situ precipitation route towards obtaining composites of polymer and calcium phosphate is similar to the strategy employed in naturally occurring biocomposites and well may prove a viable method for the synthesis of bone substitutes. 

Resin glass polyalkenoate cements Alveolar bone substitute... 

Brook, I. M., Craig, G. T. Lamb, D. J. (1991b). Initial in-vitro evaluation of glass-ionomer cements for use as alveolar bone substitutes. Clinical Materials, 7, 295-300. 

Ohtsuki, C., Miyazaki, T. and Tanihara, M. (2002) Development of bioactive organic-inorganic hybrid for bone substitutes. Materials Science and Engineering C, 22, 27-34. 

Bone is one of the few tissues capable of self-regeneration during skeletal deficiency, but this regeneration is limited by the nature and size of the defect. In general, skeletal deficiency occurs as a result of trauma, tumor, bone disease, or abnormality. In the case of severe fracture, bone will not heal by itself. For this reason, artificial bone substitutes may be required to restore routine function without damaging living tissue, and the selection of the bone graft substitute is the most important factor for better performance in vivo. 

For bone substitutes, it is very important that bioceramics have a considerable degree of porosity and particularly interconnected pores so that living bone grows rapidly into the pores. Special bone remodeling cells called osteoclasts and osteoblasts play an extremely important part of the process of rebuilding or repairing the bone. 

The success of our bone substitute in rabbit tibia was first reported in 1986 on the International Science section of CNN cable news and in the Los Angeles Times. The CNN version depicted rabbits with pins removed running around out doors in the grass and in their cages. This report attracted widespread attention and interest (Figs. 10-12). Most of these surgeries were done by Dr. Paul Capano with the assistance of Dr. Lester Matthews and Dr. Sharon Hoffman. 

Ca-P ionic cements Bone substitute Improvement of cement setting. 

T. Bartels, W. Hein, C. Taube, G. Berger, H.J. Mest, The significance of llmaplant as a bone substitute with reference to prostaglandin biosynthesis in bones. An animal experiment-clinical study, Beitr. Orthop. Traumatol. 36 (1989) 207-213. 

Lavemia, C., and J. M. Schoenung, Calcium phosphate ceramics as bone substitutes, Ceram. Bull, 70(1), 95 (1991). 

Supercritical CO2 is used in a process for bone-tissue treatment to obtain a novel bone-substitute for human surgery. The supercritical extraction step results in de-lipidation of... 

Calcium PolyP fibre has been synthesized (Griffith, 1992) and new high-performance calcium polyphosphate bioceramics has been proposed as a bone-substitute material (Nelson et al, 1993 Pilliar et al, 2001). The in vivo experiments, in which porous rods of calcium PolyP were implanted in the distal femur of rabbits, show that these rods can support bone ingrowth and give no adverse reaction (Grynpas et al, 2002). 

M. D. Grynpas, R. M. Pilliar, R. A. Kandel, R. Renlund, M. Filiaggi and M. Dumitriu (2002). Porous calcium polyphosphate scaffolds for bone substitute applications in in vivo studies. Biomaterials, 23, 2063-2070. 

Considerable development has occurred on sintered ceramics as bone substitutes. Sintered ceramics, such as alumina-based ones, are uru eactive materials as compared to CBPCs. CBPCs, because they are chemically synthesized, should perform much better as biomaterials. Sintered ceramics are fabricated by heat treatment, which makes it difficult to manipulate their microstructure, size, and shape as compared to CBPCs. Sintered ceramics may be implanted in place but cannot be used as an adhesive that will set in situ and form a joint, or as a material to fill cavities of complicated shapes. CBPCs, on the other hand, are formed out of a paste by chemical reaction and thus have distinct advantages, such as easy delivery of the CBPC paste that fills cavities. Because CBPCs expand during hardening, albeit slightly, they take the shape of those cavities. Furthermore, some CBPCs may be resorbed by the body, due to their high solubility in the biological environment, which can be useful in some applications. CBPCs are more easily manufactured and have a relatively low cost compared to sintered ceramics such as alumina and zirconia. Of the dental cements reviewed in Chapter 2 and Ref. [1], plaster of paris and zinc phosphate... 

Wang, M., Joseph, R., and Bonfield, W., Hydroxyapatite-polyethylene composites for bone substitution effects of ceramic particle size and morphology. Biomaterials, 19, 2357, 1998. 

Datamonitor (2002) Market Dynamics bone substitutes and growth factors. Datamonitor, New York... 

The last method to be discussed, which is used to form polymer/ceramic composites by electrospinning, is extremely different to the methods previously described, but worth mentioning. Zuo et al. [129] used a method to create a composite scaffold that is actually the reverse of what most people are doing. Instead of mineralizing the nanofibers, Zuo et al. actually incorporated electrospun polymer nanofibers into a ceramic bone cement in order to form a composite scaffold. It was found that by incorporating electrospun nanofibers into the cement, the scaffold became less brittle and actually behaved similarly to that of a ductile material because of the fibers. Composite scaffolds with different polymers and fiber diameters were then tested in order to determine which scaffold demonstrated the most ideal mechanical properties. However, no cell studies were conducted and this method would most likely be used for a bone substitute instead of for bone regeneration applications. 

Verron, E., Bouler, J.M., and Guicheux, J. (2012) Controlling the biological function of calcium phosphate bone substitutes with drugs. Acta Biomater., 8 (10), 3541-3551. 

Ideally, bone substitute materials should be replaced by mature bone without transient loss of mechanical support. Unfortunately, at present there is no material available fulfilling these requirements. Consequently, mechanically unstable bone defects ought to be stabilised with a non-resorbable metallic fixation made from stainless steel or titanium and the bone defect filled with a bone graft substitute. While the mechanical properties of the bone graft substitute are of minor importance, much more important it is to optimise the resorption rate of the bone graft substitute to minimise the time required for bone healing (Bohner, 2010). To control the resorption rate several strategies such as modification of the... 

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